Alex Filippenko: Supernovae, Dark Energy, Aliens & the Expanding Universe

Alex Filippenko (02:18.180)

It's one of the big questions of cosmology, and of course, we have evidence that the matter

Alex Filippenko (02:24.320)

density is sufficiently low that the universe will expand forever.

Lex Fridman (02:28.140)

But not only that, there's this weird repulsive effect, we call it dark energy for want of

Alex Filippenko (02:33.900)

a better term, and it appears to be accelerating the expansion of the universe.

Lex Fridman (02:38.860)

So if that continues, the universe will expand forever, but it need not necessarily continue.

Alex Filippenko (02:44.920)

It could reverse sign, in which case the universe could, in principle, collapse at some point

Lex Fridman (02:51.480)

in the far, far future.

Lex Fridman (02:53.200)

So in terms of investment advice, if you were to give me and then to bet all my money on

Lex Fridman (02:58.480)

one or the other, where does your intuition currently lie?

Alex Filippenko (03:01.320)

Well, right now, I would say that it would expand forever because I think that the dark

Lex Fridman (03:05.900)

energy is likely to be just quantum fluctuations of the vacuum.

Alex Filippenko (03:11.100)

The vacuum zero energy state is not a state of zero energy.

Alex Filippenko (03:15.960)

That is, the ground state is a state of some elevated energy which has a repulsive effect

Alex Filippenko (03:21.240)

to it.

Lex Fridman (03:22.240)

And that will never go away because it's not something that changes with time.

Lex Fridman (03:27.080)

So if the universe is accelerating now, it will forever continue to do so.

Lex Fridman (03:31.820)

And yet, I mean, you so effortlessly mentioned dark energy.

Lex Fridman (03:36.080)

Do we have any understanding of what the heck that thing is?

Lex Fridman (03:39.040)

Well, not really.

Lex Fridman (03:40.280)

But we're getting progressively better observational constraints.

Lex Fridman (03:44.180)

So different theories of what it might be predict different sorts of behavior for the

Alex Filippenko (03:50.160)

evolution of the universe.

Lex Fridman (03:51.900)

And we've been measuring the evolution of the universe now.

Lex Fridman (03:55.880)

And the data appear to agree with the predictions of a constant density vacuum energy, a zero

Lex Fridman (04:02.780)

point energy.

Lex Fridman (04:05.280)

But one can't prove that that's what it is because one would have to show that the measured

Lex Fridman (04:12.680)

numbers agree with the predictions to an arbitrary number of decimal places.

Lex Fridman (04:17.280)

And of course, even if you've got 8, 9, 10, 12 decimal places, what if in the 13th one,

Lex Fridman (04:23.120)

the measurements significantly differ from the prediction?

Alex Filippenko (04:27.360)

Then the dark energy isn't this vacuum state, ground state energy of the vacuum.

Lex Fridman (04:35.400)

And so then it could be some sort of a field, some sort of a new energy, a little bit like

Alex Filippenko (04:40.320)

light, like electromagnetism, but very different from light, that fills space.

Lex Fridman (04:47.480)

And that type of energy could in principle change in the distant future.

Alex Filippenko (04:52.660)

It could become gravitationally attractive for all we know.

Alex Filippenko (04:56.440)

There is a historical precedent to that, and that is that the inflation with which the

Alex Filippenko (05:00.880)

universe began when the universe was just a tiny blink of an eye old, a trillionth of

Alex Filippenko (05:07.120)

a trillionth of a trillionth of a second, the universe went whoosh, it exponentially

Alex Filippenko (05:11.320)

expanded.

Alex Filippenko (05:12.680)

That dark energy like substance, we call it the inflaton, that which inflated the universe,

Alex Filippenko (05:19.000)

later decayed into more or less normal gravitationally attractive matter.

Lex Fridman (05:24.680)

So the exponential early expansion of the universe did transition to a deceleration,

Alex Filippenko (05:31.720)

which then dominated the universe for about nine billion years.

Lex Fridman (05:35.080)

And now this small amount of dark energy started causing an acceleration about five billion

Alex Filippenko (05:42.880)

years ago.

Lex Fridman (05:43.880)

And whether that will continue or not is something that we'd like to answer, but I don't know

Alex Filippenko (05:48.280)

that we will anytime soon.

Lex Fridman (05:50.520)

So there could be this interesting field that we don't yet understand that's morphing over

Alex Filippenko (05:56.240)

time, that's changing the way the universe is expanding.

Alex Filippenko (05:59.480)

I mean, it's funny that you were thinking through this rigorously like an experimentalist.

Lex Fridman (06:06.760)

But what about like the fundamental physics of dark energy?

Alex Filippenko (06:11.260)

Is there any understanding of what the heck it is, or is this the kind of the god of the

Lex Fridman (06:20.680)

gaps or the field of the gaps?

Lex Fridman (06:22.880)

So like there must be something there because of what we're observing.

Alex Filippenko (06:26.800)

I'm very much a person who believes that there's always a cause, you know, there are no miracles

Lex Fridman (06:35.440)

of a supernatural nature, okay?

Lex Fridman (06:39.480)

So I mean, there are two broad categories, either it's the vacuum zero point energy,

Lex Fridman (06:45.360)

or it's some sort of a new energy field that pervades the universe.

Alex Filippenko (06:50.440)

The latter could change with time, the former, the vacuum energy cannot.

Lex Fridman (06:55.960)

So if it turns out that it's one of these new fields, and there are many, many possibilities,

Alex Filippenko (07:00.960)

they go by the name of quintessence and things like that, but there are many categories of

Alex Filippenko (07:06.360)

those sorts of fields, we try with data to rule them out by comparing the actual measurements

Alex Filippenko (07:14.760)

with the predictions.

Lex Fridman (07:16.440)

And some have been ruled out, but many, many others remain to be tested.

Lex Fridman (07:22.000)

And the data just have to become a lot better before we can rule out most of them and become

Lex Fridman (07:28.160)

reasonably convinced that this is a vacuum energy.

Lex Fridman (07:31.960)

So there is hypotheses for different fields, like with names and stuff like that?

Alex Filippenko (07:35.760)

Yeah, you know, generically quintessence, like the Aristotelian fifth essence, but there

Alex Filippenko (07:40.160)

are many, many versions of quintessence.

Alex Filippenko (07:42.880)

There's K essence, there's even ideas that, you know, this isn't something from within

Alex Filippenko (07:48.520)

this dark energy, but rather, there are a bunch of, say, bubble universes surrounding

Alex Filippenko (07:54.240)

our universe, and this whole idea of the multiverse is not some crazy madman type idea anymore.

Alex Filippenko (08:00.560)

It's, you know, real card carrying physicists are seriously considering this possibility

Lex Fridman (08:04.860)

of a multiverse.

Lex Fridman (08:06.240)

And some types of multiverses could have, you know, a bunch of bubbles on the outside,

Alex Filippenko (08:10.640)

which gravitationally act outward on our bubble because gravity or gravitons, the quantum

Alex Filippenko (08:18.600)

particle that is thought to carry gravity, is thought to traverse the bulk, the space

Lex Fridman (08:24.300)

between these different little bubble membranes and stuff.

Lex Fridman (08:27.080)

And so it's conceivable that these other universes are pulling outward on us.

Alex Filippenko (08:31.580)

That's not a favored explanation right now, but really, nothing has been ruled out.

Alex Filippenko (08:38.040)

No class of models has been ruled out completely.

Lex Fridman (08:41.680)

Certain examples within classes of models have been ruled out.

Lex Fridman (08:46.000)

But in general, I think we still have really a lot to learn about what's causing this

Alex Filippenko (08:52.000)

observed acceleration of the expansion of the universe, be it dark energy or some forces

Alex Filippenko (08:58.560)

from the outside, or perhaps, you know, I guess it's conceivable that, and sometimes

Alex Filippenko (09:05.760)

I wake up in the middle of the night screaming, that dark energy, that which causes the acceleration,

Lex Fridman (09:12.760)

and dark matter, that which causes galaxies and clusters of galaxies to be bound gravitationally

Lex Fridman (09:18.160)

even though there's not enough visible matter to do so.

Alex Filippenko (09:21.400)

Maybe these are our 20th and 21st century Ptolemaic epicycles.

Lex Fridman (09:28.360)

So Ptolemy had a geocentric and Aristotelian view of the world.

Alex Filippenko (09:32.820)

Everything goes around Earth.

Lex Fridman (09:34.520)

But in order to explain the backward motion of planets among the stars that happens every

Alex Filippenko (09:40.540)

year or two, or sometimes several times a year for Mercury and Venus, you needed the

Alex Filippenko (09:45.480)

planets to go around in little circles called epicycles, which themselves then went around

Alex Filippenko (09:51.080)

Earth.

Lex Fridman (09:52.080)

And in this part of the epicycle where the planet is going in the direction opposite

Alex Filippenko (09:58.840)

to the direction of the overall epicycle, it can appear in projection to be going backward

Lex Fridman (10:04.360)

among the stars, so called retrograde motion.

Lex Fridman (10:08.040)

And it was a brilliant mathematical scheme.

Alex Filippenko (10:10.240)

In fact, he could have added epicycles on top of epicycles and reproduced the observed

Alex Filippenko (10:16.480)

positions of planets to arbitrary accuracy.

Lex Fridman (10:19.740)

And this is really the beginning of what we now call Fourier analysis, right?

Alex Filippenko (10:24.760)

Any periodic function can be represented by a sum of sines and cosines of different periods,

Lex Fridman (10:31.680)

amplitudes, and phases.

Lex Fridman (10:33.560)

So it could have worked arbitrarily well.

Lex Fridman (10:36.360)

But other data show that, in fact, Earth is going around the sun.

Lex Fridman (10:42.080)

So our dark energy and dark matter, just these band aids that we now have to try to explain

Lex Fridman (10:49.420)

the data, but they're just completely wrong.

Alex Filippenko (10:53.160)

That's a possibility as well.

Lex Fridman (10:54.760)

And as a scientist, I have to be open to that possibility as an open minded scientist.

Lex Fridman (11:00.760)

How do you put yourself in the mindset of somebody that, or majority of the scientific

Lex Fridman (11:05.240)

community or majority of people believe that the Earth, everything rotates around Earth?

Lex Fridman (11:10.820)

How do you put yourself in that mindset and then take a leap to propose a model that the

Lex Fridman (11:21.200)

sun is, in fact, at the center of the solar system?

Alex Filippenko (11:25.760)

Sure.

Alex Filippenko (11:26.760)

I mean, so that puts us back in the shoes of Copernicus, right, 500 years ago, where

Alex Filippenko (11:32.640)

he had this philosophical preference for the sun being the dominant body in what we now

Lex Fridman (11:39.400)

call the solar system.

Alex Filippenko (11:41.440)

The observational evidence in terms of the measured positions of planets was not better

Lex Fridman (11:48.460)

explained by the heliocentric, sun centered system.

Alex Filippenko (11:53.460)

It's just that Copernicus saw that the sun is the source of all our light and heat, and

Lex Fridman (12:01.240)

he knew from other studies that it's far away.

Lex Fridman (12:03.920)

So the fact that it appears as big as the moon means it's actually way, way bigger because

Alex Filippenko (12:08.360)

even at that time, it was known that the sun is much farther away than the moon.

Lex Fridman (12:12.800)

So he just felt, wow, it's big, it's bright.

Lex Fridman (12:16.440)

What if it's the central thing?

Lex Fridman (12:18.680)

But the observed positions of planets at the time in the early to mid 16th century under

Alex Filippenko (12:26.720)

the heliocentric system was not a better match, at least not a significantly better match

Alex Filippenko (12:32.320)

than Ptolemy's system, which was quite accurate and lasted 1500 years.

Lex Fridman (12:36.840)

Yeah.

Alex Filippenko (12:37.840)

That's so fascinating to think that the philosophical predispositions that you bring to the table

Lex Fridman (12:45.280)

are essential.

Lex Fridman (12:46.280)

So like you have to have a young person come along that has a weird infatuation with the

Lex Fridman (12:50.600)

sun.

Alex Filippenko (12:51.600)

Yeah.

Alex Filippenko (12:52.600)

That like almost philosophically is like however their upbringing is, they're more ready for

Alex Filippenko (12:58.680)

whatever the more the simpler answer is.

Lex Fridman (13:02.560)

Right.

Alex Filippenko (13:03.560)

Oh, that's kind of sad.

Alex Filippenko (13:07.160)

It's a sad from an individual descendant of eight perspective because then that means

Alex Filippenko (13:12.640)

like me, you as a scientist, you're stuck with whatever the heck philosophies you brought

Alex Filippenko (13:19.400)

to the table and you might be almost completely unable to think outside this particular box

Alex Filippenko (13:25.140)

you've built.

Lex Fridman (13:26.140)

Right.

Alex Filippenko (13:27.140)

This is why I'm saying that, you know, as an objective scientist, one needs to have

Lex Fridman (13:29.540)

an open mind to crazy sounding new ideas.

Lex Fridman (13:34.040)

And even Copernicus was very much a man of his time and dedicated his work to the Pope.

Lex Fridman (13:40.320)

He still used circular orbits.

Alex Filippenko (13:43.120)

The sun was a little bit off center, it turns out, and a slightly off center circle looks

Lex Fridman (13:48.980)

like a slightly eccentric elliptical orbit.

Lex Fridman (13:52.220)

So then when Kepler, in fact, showed that the orbits are actually in general ellipses,

Alex Filippenko (13:58.000)

not circles, the reason that he needed Tuco Brahe's really great data to show that distinction

Alex Filippenko (14:07.760)

was that a slightly off center circle is not much different from a slightly eccentric ellipse.

Lex Fridman (14:13.520)

And so there wasn't much difference between Kepler's view and Copernicus's view and Kepler

Alex Filippenko (14:20.480)

needed the better data, Tuco Brahe's data.

Lex Fridman (14:24.640)

And so that's, again, a great example of science and observations and experiments working together

Alex Filippenko (14:33.440)

with hypotheses and they kind of bounce off each other.

Lex Fridman (14:36.960)

They play off of each other and you continually need more observations.

Lex Fridman (14:40.720)

And it wasn't until Galileo's work around 1610 that actual evidence for the heliocentric

Lex Fridman (14:49.320)

hypothesis emerged.

Alex Filippenko (14:51.040)

It came in the form of Venus, the planet Venus, going through all of the possible phases from

Alex Filippenko (14:57.100)

new to crescent to quarter to gibbous to full to waning gibbous, third quarter waning crescent,

Lex Fridman (15:03.840)

and then new again.

Alex Filippenko (15:05.020)

It turns out in the Ptolemaic system with Venus between Earth and the sun, but always

Alex Filippenko (15:10.560)

roughly in the direction of the sun, you could only get the new and crescent phases of Venus.

Lex Fridman (15:17.560)

But the observations showed a full set of phases.

Lex Fridman (15:21.600)

And moreover, when Venus was gibbous or full, that meant it was on the far side of the sun.

Alex Filippenko (15:26.620)

That meant it was farther from Earth than when it's crescent, so it should appear smaller

Lex Fridman (15:31.320)

and indeed it did.

Lex Fridman (15:33.000)

So that was the nail in the coffin in a sense.

Lex Fridman (15:36.800)

And then Galileo's other great observation was that Jupiter has moons going around it,

Lex Fridman (15:42.460)

the four Galilean satellites.

Lex Fridman (15:44.400)

And even though Jupiter moves through space, so too do the moons go with it.

Lex Fridman (15:49.440)

So first of all, Earth is not the only thing that has other things going around it.

Lex Fridman (15:53.820)

And secondly, Earth could be moving as Jupiter does and things would move with it.

Alex Filippenko (16:01.360)

We wouldn't fly off the surface and our moon wouldn't be left behind and all this kind

Alex Filippenko (16:04.720)

of stuff.

Lex Fridman (16:05.720)

So that was a big breakthrough as well, but it wasn't as definitive in my opinion as

Alex Filippenko (16:11.000)

the phases of Venus.

Alex Filippenko (16:13.680)

Sometimes I'm revealing my ignorance, but I didn't realize how much data they were working

Alex Filippenko (16:17.520)

with.

Lex Fridman (16:20.240)

So it wasn't Einstein or Freud thinking in theories.

Alex Filippenko (16:27.020)

It was a lot of data and you're playing with it and seeing how to make sense of it.

Lex Fridman (16:31.480)

So it isn't just coming up with completely abstract thought experiments.

Alex Filippenko (16:36.920)

It's looking at the data.

Lex Fridman (16:37.920)

Sure.

Lex Fridman (16:38.920)

And you look at Newton's great work, right?

Alex Filippenko (16:40.400)

The Principia, it was based in part on Galileo's observations of balls rolling down inclined

Alex Filippenko (16:47.480)

planes, supposedly falling off the Leaning Tower of Pisa, but that's probably apocryphal.

Alex Filippenko (16:53.240)

In any case, the Roman Catholic Church did history a favor, not that I'm condoning them,

Lex Fridman (17:04.040)

but they placed Galileo under house arrest and that gave Galileo time to publish, to

Alex Filippenko (17:10.440)

assemble and publish the results of his experiments that he had done decades earlier.

Alex Filippenko (17:15.640)

It's not clear he would have had time to do that, had he not been under house arrest.

Lex Fridman (17:21.400)

And so Newton, of course, very much used Galileo's observations.

Alex Filippenko (17:27.520)

Let me ask the old Russian overly philosophical question about death.

Lex Fridman (17:34.080)

So we're talking about the expanding universe.

Alex Filippenko (17:36.640)

Sure.

Lex Fridman (17:37.640)

How do you think human civilization will come to an end if we avoid the near term issues

Lex Fridman (17:42.680)

we're having?

Lex Fridman (17:45.400)

Will it be our sun burning out?

Lex Fridman (17:47.240)

Will it be comets?

Lex Fridman (17:48.240)

Oh, okay.

Lex Fridman (17:49.240)

Will it be, what is it?

Lex Fridman (17:52.560)

Do you think we have a shot at reaching the heat death of the universe?

Alex Filippenko (17:58.360)

Yeah.

Lex Fridman (17:59.360)

So we're going to leave out the anthropogenic causes of our potential destruction, which

Alex Filippenko (18:07.520)

I actually think are greater than the celestial causes.

Lex Fridman (18:14.460)

So if we get lucky and intelligent, I don't know.

Lex Fridman (18:18.560)

So no way will we as humans reach the heat death of the universe.

Alex Filippenko (18:23.680)

It's conceivable that machines, which I think will be our evolutionary descendants, might

Alex Filippenko (18:30.160)

reach that, although even they will have less and less energy with which to work as time

Alex Filippenko (18:35.120)

progresses because eventually even the lowest mass stars burn out, although it takes them

Alex Filippenko (18:40.960)

trillions of years to do so.

Lex Fridman (18:44.000)

So the point is that certainly on Earth, there are other celestial threats, existential threats,

Alex Filippenko (18:52.480)

comets, exploding stars, the sun burning out.

Lex Fridman (18:57.000)

So we will definitely need to move away from our solar system to other solar systems.

Lex Fridman (19:02.360)

And then the question is, can they keep on propagating to other planetary systems sufficiently

Lex Fridman (19:10.000)

long?

Alex Filippenko (19:11.800)

In our own solar system, the sun burning out is not the immediate existential threat.

Alex Filippenko (19:20.800)

That'll happen in about five billion years when it becomes a red giant, although I should

Alex Filippenko (19:25.400)

hasten to add that within the next one or two billion years, the sun will have brightened

Alex Filippenko (19:30.240)

enough that unless there are compensatory atmospheric changes, the oceans will evaporate

Alex Filippenko (19:38.520)

away.

Alex Filippenko (19:39.520)

They're going to need much less carbon dioxide for the temperatures to be maintained roughly

Alex Filippenko (19:44.320)

at their present temperature, and plants wouldn't like that very much.

Lex Fridman (19:47.840)

So you can't lower the carbon dioxide content too much.

Lex Fridman (19:51.520)

So within one or two billion years, probably the oceans will evaporate away.

Lex Fridman (19:56.240)

But on a sooner time scale than that, I would say an asteroid collision leading to a potential

Lex Fridman (1:00:02.680)

So there's no clear evidence that they've ever visited us on Earth here.

Lex Fridman (1:00:08.240)

And SETI has been now, the search for extraterrestrial intelligence has been scanning the skies and

Alex Filippenko (1:00:13.440)

true, we've only looked a couple of hundred light years out and that's a tiny fraction

Lex Fridman (1:00:17.320)

of the whole galaxy, a tiny fraction of these hundred billion plus stars.

Alex Filippenko (1:00:22.560)

Nevertheless, if the galaxy were teaming with life, especially intelligent life, you'd expect

Lex Fridman (1:00:30.540)

some of it to have been far more advanced than ours.

Alex Filippenko (1:00:34.800)

There's nothing special about when the industrial revolution started on Earth.

Alex Filippenko (1:00:39.880)

The chemical evolution of our galaxy was such that billions of years ago, nuclear processing

Lex Fridman (1:00:45.420)

and stars had built up clouds of gas after their explosion that were rich enough in heavy

Lex Fridman (1:00:51.280)

elements to have formed Earth like planets, even billions of years ago.

Lex Fridman (1:00:54.680)

So there could be civilizations that are billions of years ahead of ours.

Lex Fridman (1:00:58.960)

And if you look at the exponential growth of technology among Homo sapiens in the last

Alex Filippenko (1:01:03.680)

couple of hundred years and you just project that forward, I mean, there's no telling what

Alex Filippenko (1:01:07.400)

they could have achieved even in 1000 or 10,000 years, let alone a million or 10 million or

Alex Filippenko (1:01:13.360)

a billion years.

Lex Fridman (1:01:15.300)

And if they reach this capability of interstellar travel and colonization, then you can show

Alex Filippenko (1:01:21.120)

that within 10 million years or certainly a hundred million years, you can populate

Lex Fridman (1:01:25.860)

the whole galaxy.

Lex Fridman (1:01:28.960)

So then you don't have to have tried to detect them beyond a hundred or a thousand light

Lex Fridman (1:01:33.680)

years.

Alex Filippenko (1:01:34.680)

They would already be here.

Lex Fridman (1:01:35.680)

Do you think as a thought experiment, do you think it's possible that they are already

Alex Filippenko (1:01:41.360)

here, but we humans are so human centric that we're just not like our conception of what

Lex Fridman (1:01:47.720)

intelligent life looks like is, we don't want to acknowledge it.

Lex Fridman (1:01:53.720)

Like what if trees?

Lex Fridman (1:01:54.720)

Right.

Alex Filippenko (1:01:55.720)

Right.

Lex Fridman (1:01:56.720)

Right.

Alex Filippenko (1:01:57.720)

Okay, I guess the, in the form of a question, do you think we'll actually detect intelligent

Lex Fridman (1:02:02.640)

life if it came to visit us?

Alex Filippenko (1:02:04.480)

Yeah.

Alex Filippenko (1:02:05.480)

I mean, it's like, you know, you're an ant crawling around on a sidewalk somewhere and

Lex Fridman (1:02:08.240)

do you notice the humans wandering around and the empire state building and you know,

Lex Fridman (1:02:13.160)

rocket ships flying to the moon and all that kind of stuff, right?

Alex Filippenko (1:02:16.760)

It's conceivable that we haven't detected it and that we're so primitive compared to

Lex Fridman (1:02:21.340)

them that we're just not able to do so.

Alex Filippenko (1:02:23.240)

Like if you look at dark energy, maybe we call it as a field.

Alex Filippenko (1:02:27.540)

It's just that my own feeling is that in science now through observations and experiments,

Alex Filippenko (1:02:33.800)

we've measured so many things and basically we understand a lot of stuff.

Lex Fridman (1:02:40.000)

Okay.

Alex Filippenko (1:02:41.000)

Fabric of reality.

Lex Fridman (1:02:42.000)

Yeah.

Alex Filippenko (1:02:43.000)

The fabric of reality, we understand quite well.

Lex Fridman (1:02:44.000)

And there are a few little things like dark matter and dark energy that may be some sign

Alex Filippenko (1:02:47.480)

of some super intelligence, but I doubt it.

Lex Fridman (1:02:50.240)

Okay.

Lex Fridman (1:02:51.240)

You know, why would some super intelligence be holding clusters of galaxies together?

Lex Fridman (1:02:54.480)

Why would they be responsible for accelerating the expansion of the universe?

Lex Fridman (1:02:58.280)

So the point is, is that through science and applied science and engineering, we understand

Lex Fridman (1:03:04.440)

so much now that I'm not saying we know everything, but we know a hell of a lot.

Alex Filippenko (1:03:09.920)

Okay.

Lex Fridman (1:03:10.920)

And so there's, it's not like there are lots of mysteries flying around there that are

Alex Filippenko (1:03:14.820)

completely outside our level of exploration or understanding.

Lex Fridman (1:03:23.560)

Yeah.

Alex Filippenko (1:03:24.920)

From a, I would say from, from a mystery perspective, it seems like the mystery of our own like

Alex Filippenko (1:03:32.760)

cognition and consciousness is much grander than like the degrees of freedom of possible

Alex Filippenko (1:03:38.760)

explanations for what the heck is going on is much greater there than in the, in the

Lex Fridman (1:03:42.840)

physics of the observed.

Lex Fridman (1:03:44.440)

How the brain works.

Lex Fridman (1:03:46.000)

How did life arise?

Alex Filippenko (1:03:47.560)

Yeah.

Lex Fridman (1:03:48.560)

That's big, big questions.

Lex Fridman (1:03:50.500)

But they, to me, don't indicate the existence of, of, of an alien or something.

Alex Filippenko (1:03:57.000)

I mean, unless we are the aliens, you know, we could have been contamination from some

Alex Filippenko (1:04:00.760)

rocket ship that, that hit here a long, long time ago and all evidence of it has been destroyed.

Lex Fridman (1:04:06.120)

But again, that alien would have started out somewhere.

Lex Fridman (1:04:09.740)

They're not, they're not here watching us right now, right?

Lex Fridman (1:04:14.260)

They're not among us.

Lex Fridman (1:04:16.060)

And so though there are expert potential explanations for the Fermi paradox, and one of them that

Alex Filippenko (1:04:22.480)

I kind of like is that the truly intelligent creatures are those that decided not to colonize

Alex Filippenko (1:04:29.120)

the whole galaxy because they'd quickly run out of room there because it's exponential,

Lex Fridman (1:04:33.280)

right?

Alex Filippenko (1:04:34.280)

You send a probe to a planet, it makes two copies, they go out, they make two copies

Lex Fridman (1:04:39.480)

each and it's an exponential, right?

Alex Filippenko (1:04:41.480)

They quickly colonize the whole galaxy.

Lex Fridman (1:04:43.200)

But then the distance to the next galaxy, the next big one like Andromeda, that's two

Lex Fridman (1:04:47.620)

and a half million light years.

Lex Fridman (1:04:50.080)

That's a much grander scale now, right?

Lex Fridman (1:04:52.480)

And so it also could be that the reason they survived this long is that they got over this

Alex Filippenko (1:04:59.080)

tendency that may well exist among sufficiently intelligent creatures, this tendency for aggression

Lex Fridman (1:05:06.720)

and self destruction, right?

Alex Filippenko (1:05:09.280)

If they bypass that, and that may be one of the great filters if there are more than one,

Lex Fridman (1:05:14.480)

right?

Alex Filippenko (1:05:15.480)

Then they may not be a type of creature that feels the need to go and say, oh, there's

Alex Filippenko (1:05:21.800)

a nice looking planet and there's a bunch of ants on it, let's go squish them and colonize

Lex Fridman (1:05:28.640)

it.

Alex Filippenko (1:05:29.640)

No, it could even be the kind of Star Trek like prime directive where you go and explore

Lex Fridman (1:05:34.120)

worlds, but you don't interfere in any way, right?

Lex Fridman (1:05:38.340)

And also we call it exploration is beautiful and everything, but there is underlying this

Lex Fridman (1:05:44.080)

desire to explore is a desire to conquer.

Alex Filippenko (1:05:47.240)

Yeah.

Lex Fridman (1:05:48.240)

I mean, if we're just being really honest right now for us, it is right.

Lex Fridman (1:05:52.720)

And you're saying it's possible to separate, but I would venture to say that you wouldn't

Lex Fridman (1:05:58.960)

that those are coupled.

Lex Fridman (1:06:00.280)

So I could, I could imagine a civilization that lives on for billions of years that just

Alex Filippenko (1:06:06.160)

stays on, it's like figures out the minimal effort way of just peacefully existing.

Alex Filippenko (1:06:12.440)

It's like a monastery.

Lex Fridman (1:06:13.440)

Yeah.

Lex Fridman (1:06:14.440)

And it limits itself.

Lex Fridman (1:06:15.440)

Yeah.

Alex Filippenko (1:06:16.440)

It limits itself.

Lex Fridman (1:06:17.440)

You know, it's, it's planted its seeds in a number of places.

Lex Fridman (1:06:19.560)

So it's not vulnerable to a single point failure, right?

Alex Filippenko (1:06:24.280)

Supernova going off near one of these stars or something, or an asteroid or a comet coming

Alex Filippenko (1:06:28.760)

in from the Oort cloud equivalent of that planetary system and without warning, you

Lex Fridman (1:06:33.320)

know, thrashing them to bits.

Lex Fridman (1:06:35.240)

So they've got their seeds in a bunch of places, but they chose not to colonize, colonize the

Lex Fridman (1:06:40.480)

galaxy.

Lex Fridman (1:06:41.480)

And they also choose not to interfere with this incredibly prevalent, primitive organism

Lex Fridman (1:06:47.960)

homo sapiens, right?

Alex Filippenko (1:06:51.360)

Or they, uh, this is like a, they enjoy, this is like a TV show for them.

Lex Fridman (1:06:57.320)

Yeah.

Alex Filippenko (1:06:58.320)

It could be like a TV show.

Lex Fridman (1:06:59.320)

Right.

Lex Fridman (1:07:00.320)

So they just tuned in.

Lex Fridman (1:07:01.800)

Right.

Alex Filippenko (1:07:02.800)

There are no other possible explanations yet.

Alex Filippenko (1:07:05.400)

I think that to me, the most likely explanation for the peri me paradox is that they really

Alex Filippenko (1:07:10.640)

are very, very rare.

Lex Fridman (1:07:12.600)

And you know, Carl Sagan estimated a hundred thousand of them.

Alex Filippenko (1:07:16.080)

If there's that many, some of them would have been way ahead of us and, and I think we would

Lex Fridman (1:07:20.120)

have seen them by now.

Alex Filippenko (1:07:22.080)

If there are a handful, maybe they're there.

Lex Fridman (1:07:24.360)

But at that point, you're right on this dividing line between being a pessimist and an optimist.

Alex Filippenko (1:07:29.720)

Yeah.

Lex Fridman (1:07:30.720)

And what are the odds for that?

Alex Filippenko (1:07:31.720)

Right.

Lex Fridman (1:07:32.720)

What are the things that had to go right for us?

Alex Filippenko (1:07:35.080)

Yeah.

Lex Fridman (1:07:36.080)

And then, you know, getting back to something you said earlier, let's discuss, you know,

Alex Filippenko (1:07:39.600)

primitive life.

Lex Fridman (1:07:40.600)

Yeah.

Alex Filippenko (1:07:41.600)

That could be the thing that's difficult to achieve.

Alex Filippenko (1:07:44.520)

Just getting the random molecules together to a point where they start self replicating

Lex Fridman (1:07:50.200)

and evolving and becoming better and all that.

Alex Filippenko (1:07:53.960)

That's an inordinately difficult thing, I think, though I'm not, you know, some molecular

Alex Filippenko (1:07:58.120)

or cell biologist, but just it's, it's, it's the usual argument.

Alex Filippenko (1:08:01.960)

You know, you're wandering around in the Sahara desert and you stumble across a watch.

Alex Filippenko (1:08:06.660)

Is your, is your initial response, oh, you know, a bunch of sand grains just came together

Lex Fridman (1:08:12.760)

randomly and formed this watch.

Alex Filippenko (1:08:14.560)

No, you, you think that something formed it or it came from some simpler structure that

Lex Fridman (1:08:21.200)

then became, you know, more complex.

Alex Filippenko (1:08:23.360)

All right.

Lex Fridman (1:08:24.360)

It didn't just form.

Alex Filippenko (1:08:26.000)

Well, even the simplest life is, is a very, very complex structure.

Alex Filippenko (1:08:32.040)

Even the, even the simplest prokaryotic cells, not to mention eukaryotic cells, although

Alex Filippenko (1:08:36.640)

that transition may have been the so called great filter as well.

Lex Fridman (1:08:40.580)

Maybe the cells without a nucleus are relatively easy to form.

Lex Fridman (1:08:45.180)

And then the big next step is where you have a nucleus, which then provides a lot of energy,

Lex Fridman (1:08:50.240)

which allows the cell to become much, much more complex and so on.

Alex Filippenko (1:08:54.440)

Interestingly, going from eukaryotic cells, single cells to multicellular organisms does

Alex Filippenko (1:09:01.480)

not appear to be, at least on earth, one of these great filters because there's evidence

Alex Filippenko (1:09:05.640)

that it happened dozens of times independently on earth.

Lex Fridman (1:09:08.980)

So by, by a really great filter, something that happens very, very rarely, I mean that

Alex Filippenko (1:09:14.640)

we had to get through an obstacle that is just incredibly rare to get through.

Lex Fridman (1:09:25.320)

And one of the really exciting scientific things is that that particular point is something

Alex Filippenko (1:09:32.120)

that we might be able to discover, even in our lifetimes that find life elsewhere like

Lex Fridman (1:09:37.020)

Europa or be able to see that would be bad news, right?

Alex Filippenko (1:09:42.840)

Because if we find lots of pretty advanced life, yeah, that would suggest, and especially

Alex Filippenko (1:09:49.640)

if we found some, you know, defunct, you know, fossilized civilization or something somewhere

Alex Filippenko (1:09:53.520)

else that would be bacteria, you mean, defunct civilization of like, oh, I'm sorry, I switched

Lex Fridman (1:10:00.660)

gears there.

Alex Filippenko (1:10:01.660)

If we, if we found some intelligent or even trilobites right and stuff, you know, elsewhere,

Alex Filippenko (1:10:06.840)

that would be bad news for us because that would mean that the great filter is ahead

Alex Filippenko (1:10:09.840)

of us, you know, right, because it would mean that lots of, lots of things have gotten roughly

Lex Fridman (1:10:16.400)

to our level.

Alex Filippenko (1:10:17.400)

Yeah.

Alex Filippenko (1:10:18.400)

But, but given the Fermi paradox, if you accept that the Fermi paradox means that there's

Alex Filippenko (1:10:23.400)

no one else out there, you don't necessarily have to accept that, but if you accept that

Alex Filippenko (1:10:27.800)

it means that no one else is out there and yet there are lots of things we found that

Alex Filippenko (1:10:31.980)

are at or roughly at our level, that means that the great filter is ahead of us and that

Alex Filippenko (1:10:36.940)

bodes poorly for our longterm future, you know, it's funny you said, uh, you started by saying

Alex Filippenko (1:10:45.700)

you're a little bit on the pessimistic side, but it's funny because we're doing this kind

Alex Filippenko (1:10:51.040)

of dance between pessimism and optimism because I'm not sure if us being alone in the observable

Alex Filippenko (1:10:56.600)

universe as intelligent beings is pessimistic, well, it's good news in a sense for us because

Alex Filippenko (1:11:03.080)

it means that we made it through, see, if we're the only ones and there are such great

Alex Filippenko (1:11:10.880)

filters, maybe more than one formation of life might be one of them formation of eukaryotic

Alex Filippenko (1:11:16.400)

that is with the nucleus cells being another development of human like intelligence might

Lex Fridman (1:11:22.000)

be another, right?

Lex Fridman (1:11:23.040)

There might be several such filters and we were the lucky ones.

Lex Fridman (1:11:27.720)

And you know, then people say, well then that means you're putting yourself into a special

Alex Filippenko (1:11:31.640)

perspective and every time we've done that we've been wrong and yeah, yeah, I know all

Alex Filippenko (1:11:35.520)

those arguments, but it still could be the case that there's one of us at least per galaxy

Alex Filippenko (1:11:41.400)

or pretend or a hundred or a thousand galaxies and we're sitting here having this conversation

Alex Filippenko (1:11:47.260)

because we exist.

Lex Fridman (1:11:49.000)

And so there's a, there's an observational selection effect there, right?

Alex Filippenko (1:11:53.180)

Just because we're special doesn't mean that we shouldn't have these conversations about

Lex Fridman (1:11:57.000)

whether or not we're special, right?

Alex Filippenko (1:11:59.920)

Yeah, so that's, that's so exciting.

Lex Fridman (1:12:02.120)

That's optimistic.

Lex Fridman (1:12:03.360)

So that's the, that's the optimistic part that if we don't find other intelligent life

Lex Fridman (1:12:08.400)

there, it might mean that we're the ones that made it.

Lex Fridman (1:12:13.120)

And in general, outside the great filter and so on, you know, it's not obvious that the

Alex Filippenko (1:12:19.160)

Stephen Hawking thing, which is, it's not obvious that life out there is going to be kind to

Alex Filippenko (1:12:23.760)

us.

Lex Fridman (1:12:24.760)

Oh yeah.

Alex Filippenko (1:12:25.760)

So, you know, I knew Hawking and I greatly respect his, his scientific work and in particular

Alex Filippenko (1:12:33.040)

the early work on the unification of general theory of relativity and quantum physics to

Alex Filippenko (1:12:38.320)

two great pillars in modern physics, you know, Hawking radiation and all that fantastic work.

Alex Filippenko (1:12:42.760)

You know, if you were alive, you should have been a recipient of this year's physics Nobel

Alex Filippenko (1:12:47.240)

prize, which was for the discovery of black holes and also by Roger Penrose for the theoretical

Alex Filippenko (1:12:53.260)

work showing that given a star that's massive enough, you basically can't avoid having a

Alex Filippenko (1:13:00.120)

black hole.

Lex Fridman (1:13:01.120)

Anyway, Hawking, fantastic.

Alex Filippenko (1:13:02.120)

I, I tip my hat to him.

Lex Fridman (1:13:04.420)

May he rest in peace.

Alex Filippenko (1:13:05.420)

That would have been a heck of a Nobel prize, black holes, heck of a good group.

Alex Filippenko (1:13:10.400)

But, but, but going back to what he said that we shouldn't be broadcasting our presence

Alex Filippenko (1:13:14.820)

to others there, I actually disagree with him respectfully because first of all, we've

Alex Filippenko (1:13:21.160)

been unintentionally broadcasting our presence for a hundred years since the development

Alex Filippenko (1:13:25.360)

of radio and TV.

Lex Fridman (1:13:27.200)

Okay.

Alex Filippenko (1:13:28.200)

Secondly, any alien that has the capability of coming here and squashing us either already

Lex Fridman (1:13:35.600)

knows about us and you know, doesn't care because we're just like little ants.

Lex Fridman (1:13:39.880)

And when there are ants in your kitchen, you tend to squash them.

Lex Fridman (1:13:42.920)

But if there are ants on the sidewalk and you're walking by, do you feel some great

Lex Fridman (1:13:47.400)

conviction that you have to squash any of them?

Lex Fridman (1:13:49.720)

No, you generally don't, right?

Alex Filippenko (1:13:51.440)

We're irrelevant to them.

Alex Filippenko (1:13:53.040)

All they need to do is keep an eye on us to see whether we're approaching the kind of

Alex Filippenko (1:13:57.800)

technological capability and know about them and have intentions of attacking them.

Lex Fridman (1:14:04.800)

And then they can squash us, right?

Alex Filippenko (1:14:06.960)

Um, you know, they, they could have done it long ago.

Lex Fridman (1:14:10.800)

Yeah.

Alex Filippenko (1:14:11.800)

They'll, they'll do it if they want to, whether we advertise our presence or not is, is irrelevant.

Lex Fridman (1:14:17.160)

So I really think that that's not a huge existential threat.

Lex Fridman (1:14:21.720)

So this is a good place to bring up a difficult topic.

Alex Filippenko (1:14:25.020)

You mentioned, um, they might, they would be paying attention to us to see if we come

Alex Filippenko (1:14:31.160)

up with any crazy technology.

Lex Fridman (1:14:34.120)

There's folks who have reported UFO sightings.

Alex Filippenko (1:14:37.840)

There's actually, I've recently found out there's a websites that track this, the data,

Alex Filippenko (1:14:42.520)

the data of these reportings, and there's millions of them in the past, uh, several

Alex Filippenko (1:14:48.680)

decades.

Lex Fridman (1:14:49.680)

So seven decades and so on that they've been recorded and the ufologist community, as they

Alex Filippenko (1:14:58.760)

refer to themselves, you know, one of the ideas that I find compelling from an alien

Alex Filippenko (1:15:05.040)

perspective that they kind of started showing up ever since we figured out how to build

Alex Filippenko (1:15:11.560)

nuclear weapons that we should, uh, so I mean, you know, if I was an LA and I would start

Lex Fridman (1:15:19.760)

showing up then as well, just, well, why not just observe us from afar?

Alex Filippenko (1:15:23.240)

No, I know.

Lex Fridman (1:15:24.240)

Right.

Alex Filippenko (1:15:25.240)

I would figure out, but that's why I'm always, uh, keeping a distance and staying blurry,

Lex Fridman (1:15:30.160)

but very pixelated, very pixelated, you know, that there is a something in the human condition

Alex Filippenko (1:15:37.320)

that a cognition that wants to see, wants to believe beautiful things and, uh, some

Alex Filippenko (1:15:43.320)

are terrifying, some are exciting, uh, goats, Bigfoot is a big fascination for folks.

Alex Filippenko (1:15:51.040)

Yeah.

Lex Fridman (1:15:52.040)

And, uh, UFO sightings, I think falls into that.

Alex Filippenko (1:15:54.000)

There's people that look at lights in the night sky and I mean, there's, it's kind of

Lex Fridman (1:16:02.320)

a downer to think in a skeptical sense, to think that that's just a light.

Alex Filippenko (1:16:07.840)

Yeah.

Lex Fridman (1:16:08.840)

You want to feel like there's something magical there.

Alex Filippenko (1:16:11.280)

Sure.

Alex Filippenko (1:16:12.280)

Uh, I mean, I felt that first when my dad, my dad's a physicist, when he first told me

Alex Filippenko (1:16:16.600)

about ball lightning when I was like a little kid, very weird, very like weird physical

Lex Fridman (1:16:22.080)

phenomenon.

Lex Fridman (1:16:23.080)

And he said, his intuition was telling me this as a little kid, uh, like, I really like

Lex Fridman (1:16:29.880)

math.

Alex Filippenko (1:16:30.880)

His intuition was whoever figures out ball lightning, we'll get a Nobel prize.

Alex Filippenko (1:16:34.680)

Like he, I think that was a side comment he gave me and I decided there when I was like

Alex Filippenko (1:16:40.040)

five years old or whatever, I'm going to win a Nobel prize for figuring out ball lightning.

Lex Fridman (1:16:44.840)

That was like one of the first sort of sparks of the scientific mindset.

Alex Filippenko (1:16:49.040)

Those mysteries, they capture your imagination.

Lex Fridman (1:16:51.560)

I think when I speak to people that report UFOs, that's that fire.

Alex Filippenko (1:16:56.880)

That's what I see.

Lex Fridman (1:16:57.880)

That excitement.

Lex Fridman (1:16:58.880)

And I understand that.

Lex Fridman (1:16:59.880)

But what, what do we do with that?

Alex Filippenko (1:17:02.960)

Because there's hundreds of thousands, if not millions, and then the scientific community,

Lex Fridman (1:17:08.120)

you're like the perfect person.

Alex Filippenko (1:17:09.120)

You have an awesome Einstein shirt.

Lex Fridman (1:17:13.120)

What, what do we do with those reports?

Alex Filippenko (1:17:17.120)

It's a, most of the scientific community kind of rolls their eyes and dismisses it.

Lex Fridman (1:17:21.840)

Is it possible that a tiny percent of those folks saw something that's worth deeply investigating?

Alex Filippenko (1:17:30.520)

Sure.

Lex Fridman (1:17:31.520)

We should investigate it.

Alex Filippenko (1:17:32.600)

It's just one of these things where, you know, they've not brought us a hunk of kryptonite

Lex Fridman (1:17:37.000)

or something like that, right?

Alex Filippenko (1:17:38.340)

They haven't brought us actual tangible physical evidence with which experiments can be done

Lex Fridman (1:17:44.320)

in laboratories.

Alex Filippenko (1:17:45.320)

Right.

Lex Fridman (1:17:46.320)

It's, it's anecdotal evidence.

Alex Filippenko (1:17:48.120)

The photographs are, in some cases, in most cases, I would say quite ambiguous.

Lex Fridman (1:17:54.360)

I don't know what to think about.

Lex Fridman (1:17:55.560)

So David Faber is the first person.

Alex Filippenko (1:17:58.000)

He's a Navy pilot, commander, and there's a bunch of them, but he's sort of one of the

Alex Filippenko (1:18:02.960)

most legit pilots and people I've ever met.

Alex Filippenko (1:18:08.900)

The fact that he saw something weird, he doesn't know what the heck it is, but he saw something

Alex Filippenko (1:18:14.160)

weird.

Lex Fridman (1:18:15.160)

I mean, I don't know what to do with that.

Lex Fridman (1:18:16.920)

And one on the psychological side, so I'm pretty confident he saw what he says he saw,

Lex Fridman (1:18:24.040)

which he's not, he's saying it's something weird.

Alex Filippenko (1:18:29.240)

One of the interesting psychological things that worries me is that everybody in the Navy,

Alex Filippenko (1:18:36.560)

everybody in the US government, everybody in the scientific community, just kind of

Alex Filippenko (1:18:40.960)

like pretended that nothing happened.

Lex Fridman (1:18:45.800)

That kind of instinct.

Alex Filippenko (1:18:47.200)

That's what makes me believe if aliens show up, we would all like just ignore their presence.

Alex Filippenko (1:18:53.260)

That's what bothered me that you don't, you don't investigate it more carefully and use

Alex Filippenko (1:19:00.000)

this opportunity to inspire the world.

Lex Fridman (1:19:03.520)

So in terms of kryptonite, I think the conspiracy theory folks say that whenever there is some

Alex Filippenko (1:19:12.120)

good hard evidence that scientists would be excited about, there's this kind of conspiracy

Alex Filippenko (1:19:17.480)

that I don't like because it's ultimately negative that the US government will somehow

Alex Filippenko (1:19:21.360)

hide the good evidence to protect it.

Alex Filippenko (1:19:26.080)

Of course, there's some legitimacy to it because you want to protect military secrets, all

Alex Filippenko (1:19:32.200)

that kind of stuff.

Lex Fridman (1:19:33.200)

But I don't know what to do with this beautiful mess because I think millions of people are

Alex Filippenko (1:19:41.680)

inspired by UFOs and it feels like an opportunity to inspire people about science.

Lex Fridman (1:19:47.760)

So I would say, as Carl Sagan used to say, extraordinary claims require extraordinary

Alex Filippenko (1:19:53.200)

evidence.

Lex Fridman (1:19:54.200)

I've quoted him a number of times.

Alex Filippenko (1:19:59.240)

We would welcome such evidence.

Alex Filippenko (1:20:03.000)

On the other hand, a lot of the things that are seen or perhaps even hidden from us, you

Alex Filippenko (1:20:08.960)

could imagine for military purposes, surveillance purposes, the US government doesn't want us

Lex Fridman (1:20:15.560)

to know.

Alex Filippenko (1:20:16.560)

Or maybe some of these pilots saw Soviet or Israeli or whatever satellites or some of

Alex Filippenko (1:20:24.120)

the crashes that have occurred were later found to be weather balloons or whatever.

Alex Filippenko (1:20:31.040)

When there are more conventional explanations, science tends to stay away from the sensational

Lex Fridman (1:20:40.720)

ones.

Lex Fridman (1:20:41.960)

And so it may be that someone else's calling in life is to investigate these phenomena.

Lex Fridman (1:20:49.000)

And I welcome that as a scientist.

Alex Filippenko (1:20:51.640)

I don't categorically actually deny the possibility that ships of some sort could have visited

Alex Filippenko (1:20:58.360)

us because, as I said earlier, at slow speeds, there's no problem in reaching other stars.

Alex Filippenko (1:21:04.240)

In fact, our Voyager and Pioneer spacecraft in a few million years are going to be in

Lex Fridman (1:21:08.920)

the vicinity of different stars.

Lex Fridman (1:21:10.920)

We can even calculate which ones they're going to be in the vicinity of, right?

Lex Fridman (1:21:15.200)

So there's nothing that breaks any laws of physics if you do it slowly.

Lex Fridman (1:21:19.280)

But that's different, just having Voyager or Pioneer fly by some star, that's different

Alex Filippenko (1:21:24.480)

from having active aliens altering the trajectory of their vehicle in real time, spying on us,

Lex Fridman (1:21:31.680)

and then either zipping back to their home planet or sending signals that tell them about

Alex Filippenko (1:21:38.200)

us because they are likely many light years away, and they're not going to have broken

Lex Fridman (1:21:44.760)

that barrier as well, okay?

Lex Fridman (1:21:48.800)

So I just, you know, go ahead, study them.

Alex Filippenko (1:21:54.080)

For some young kid who wants to do it, it might be their calling, and that's how they

Alex Filippenko (1:22:00.400)

might find meaning in their lives, is to be the scientist who really explores these things.

Alex Filippenko (1:22:05.960)

I chose not to because at a very young age, I found the evidence, to the degree that I

Alex Filippenko (1:22:11.520)

investigated it, to be really quite unconvincing, and I had other things that I wanted to do.

Lex Fridman (1:22:18.320)

But I don't categorically deny the possibility, and I think it should be investigated.

Alex Filippenko (1:22:23.040)

Yeah, I mean, this is one of those phenomena that 99.9% of people are almost definitely,

Alex Filippenko (1:22:31.840)

there's conventional explanations, and then there's like mysterious things that probably

Alex Filippenko (1:22:38.300)

have explanations that are a little bit more complicated, but there's not enough to work

Alex Filippenko (1:22:45.400)

with.

Alex Filippenko (1:22:46.400)

I tend to believe that if aliens showed up, there will be plenty of evidence for scientists

Alex Filippenko (1:22:52.440)

to study.

Lex Fridman (1:22:53.440)

Yeah.

Lex Fridman (1:22:54.440)

And exactly as you said, avoid your type of spacecraft that could see sort of some kind

Alex Filippenko (1:23:03.760)

of, kind of a dumb thing, almost like a sensor that's like probing, like statistically speaking.

Alex Filippenko (1:23:09.240)

Flying by.

Alex Filippenko (1:23:10.240)

Flying by, maybe lands, maybe there's some kind of robot type of thingies that just like

Alex Filippenko (1:23:13.920)

move around and so on, like in ways that we don't understand.

Lex Fridman (1:23:17.920)

But I feel like, well, I feel like there'll be plenty of hard, hard to dismiss evidence.

Lex Fridman (1:23:27.320)

And I also, especially this year, believe that the US government is not sufficiently

Alex Filippenko (1:23:33.900)

competent given the huge amount of evidence that will be revealed from this kind of thing

Alex Filippenko (1:23:39.460)

to conceal all of it.

Lex Fridman (1:23:41.400)

Right.

Alex Filippenko (1:23:42.400)

At least in modern times, you can say maybe decades ago, but in modern times.

Alex Filippenko (1:23:46.720)

Right, you know, the people I speak to and the reason I bring it up is because so many

Alex Filippenko (1:23:51.200)

people write to me, they're inspired by it.

Alex Filippenko (1:23:53.600)

By the way, I wanted to comment on something you said earlier on, yeah, I had said that

Alex Filippenko (1:23:57.160)

I'm sort of a pessimist in that I think there are very few other intelligent, mechanically

Lex Fridman (1:24:03.640)

able creatures out there.

Lex Fridman (1:24:06.160)

But then I said, yes, in a sense, I'm an optimist, as you pointed out, because it means

Lex Fridman (1:24:10.360)

that we made it through the great filter.

Alex Filippenko (1:24:13.240)

Right.

Alex Filippenko (1:24:14.240)

I meant originally that I'm a pessimist in that I'm pessimistic about the possibility

Alex Filippenko (1:24:19.440)

that there are many, many of us out there, you know, mathematically speaking in the Drake

Lex Fridman (1:24:23.920)

equation.

Alex Filippenko (1:24:24.920)

Exactly.

Lex Fridman (1:24:25.920)

Right.

Alex Filippenko (1:24:26.920)

Right.

Lex Fridman (1:24:27.920)

But it may mean a good thing for our ultimate survival.

Alex Filippenko (1:24:28.920)

Right.

Lex Fridman (1:24:29.920)

So I'm glad you caught me on that.

Alex Filippenko (1:24:30.920)

Yeah, I definitely agree with you.

Lex Fridman (1:24:32.440)

It is ultimately an optimistic statement.

Lex Fridman (1:24:34.000)

But anyway, I think, you know, UFO research is interesting.

Lex Fridman (1:24:38.140)

And I guess one of the reasons I've not been terribly convinced is that I think there are

Alex Filippenko (1:24:43.280)

some scientists who are investigating this and they've not found any clear evidence.

Alex Filippenko (1:24:49.080)

Now, I must admit, I have not looked through the literature to convince myself that there

Alex Filippenko (1:24:53.880)

are many scientists doing systematic studies of these various reports.

Alex Filippenko (1:24:58.000)

I can't say for sure that there's a critical mass of them, but it's just that you never

Alex Filippenko (1:25:03.620)

get these reports from hardcore scientists.

Lex Fridman (1:25:06.580)

That's another thing.

Lex Fridman (1:25:07.580)

And astronomers, you know, what do we do?

Alex Filippenko (1:25:08.680)

We spend our time studying the heavens and you'd think we'd be the ones that are most

Alex Filippenko (1:25:12.760)

likely aside from pilots, perhaps, at seeing weird things in the sky.

Lex Fridman (1:25:17.480)

And we just never do of the unexplained UFO type nature.

Alex Filippenko (1:25:22.240)

Yeah, I definitely, I try to keep an open mind, but for people who listen, it's actually

Lex Fridman (1:25:28.720)

really difficult for scientists.

Alex Filippenko (1:25:30.680)

Like I get probably like this year, I've probably gotten over probably maybe over a thousand

Lex Fridman (1:25:38.160)

emails on the topic of AGI.

Alex Filippenko (1:25:42.740)

It's very difficult to, you know, people write to me, it's like, how can you ignore this

Lex Fridman (1:25:48.760)

in AGI side?

Alex Filippenko (1:25:49.880)

Like this model, this is obviously the model that's going to achieve general intelligence.

Lex Fridman (1:25:53.880)

How can you ignore it?

Alex Filippenko (1:25:54.880)

I'm giving you the answer.

Lex Fridman (1:25:55.880)

Here's my document.

Lex Fridman (1:25:56.880)

And they're always just these large write ups.

Lex Fridman (1:26:00.600)

The problem is it's very difficult to weed through a bunch of BS.

Alex Filippenko (1:26:07.920)

It's very possible that you had actually saw the UFO, but you have to acknowledge that

Alex Filippenko (1:26:15.040)

by UFO, I mean, an extraterrestrial life, you have to acknowledge the hundreds of thousands

Alex Filippenko (1:26:20.460)

of people who are a little bit, if not a lot full of BS.

Lex Fridman (1:26:26.600)

And from a scientist perspective, it's really hard work and it's when there's amazing stuff

Lex Fridman (1:26:33.560)

out there, it's like, why invest in Bigfoot when evolution in all of its richness is beautiful?

Lex Fridman (1:26:40.240)

Who cares about a monkey that walks on two feet or eight or whatever?

Alex Filippenko (1:26:43.360)

Like there's a zillion decoys at observatories.

Lex Fridman (1:26:47.940)

True fact.

Alex Filippenko (1:26:48.940)

We get lots and lots of phone calls when Venus, the evening star, but just really a bright

Alex Filippenko (1:26:55.280)

planet happens to be close to the crescent moon because it's such a striking pair.

Alex Filippenko (1:27:00.360)

This happens once in a while.

Lex Fridman (1:27:01.360)

And we get these phone calls, oh, there's a UFO next to the moon.

Lex Fridman (1:27:04.720)

And no, it's Venus.

Lex Fridman (1:27:06.280)

And so they're just and I'm not saying the best UFO reports are of that nature.

Alex Filippenko (1:27:12.520)

No, there are some much more convincing cases.

Lex Fridman (1:27:14.400)

And I've seen some of the footage and blah, blah, blah.

Lex Fridman (1:27:17.240)

But it's just there's so many decoys, right?

Lex Fridman (1:27:19.520)

So much so much noise that you have to filter out.

Lex Fridman (1:27:22.660)

And there's only so many scientists.

Lex Fridman (1:27:23.920)

So it's hard.

Alex Filippenko (1:27:24.920)

There's only so much.

Lex Fridman (1:27:25.920)

There's only so much time as well.

Lex Fridman (1:27:27.240)

And you have to choose what problems you work on.

Alex Filippenko (1:27:30.000)

You know, this might be a fun question to ask to kind of explore the idea of the expanding

Alex Filippenko (1:27:37.720)

universe.

Lex Fridman (1:27:38.720)

Yeah.

Lex Fridman (1:27:39.720)

So the the radius of the observable universe is 45.7 billion light years.

Lex Fridman (1:27:46.800)

Yeah.

Lex Fridman (1:27:47.800)

And the age of the universe is 13.7 billion years.

Lex Fridman (1:27:56.240)

That's less than the radius of the universe.

Lex Fridman (1:28:00.880)

How's that possible?

Lex Fridman (1:28:01.880)

So that's a great question.

Lex Fridman (1:28:03.560)

So I meant to bring a little a little prop I have with ping pong balls on a rubber hose,

Lex Fridman (1:28:08.720)

a rubber band.

Alex Filippenko (1:28:09.720)

I use it in many of the lectures that one can find of me online.

Lex Fridman (1:28:14.080)

But you have in an expanding universe, the space itself between galaxies or more correctly,

Alex Filippenko (1:28:20.120)

clusters of galaxies expanding.

Lex Fridman (1:28:23.040)

So imagine light going from one cluster to another.

Alex Filippenko (1:28:27.080)

It traverses some distance and then while it's traversing the rest, that part that it

Lex Fridman (1:28:33.640)

already traveled through continues to expand.

Alex Filippenko (1:28:38.440)

Now 13.7 billion years might have gone by since the light that we are seeing from the

Alex Filippenko (1:28:47.160)

early stages, the so called cosmic microwave background radiation, which is the afterglow

Alex Filippenko (1:28:52.280)

of the Big Bang or the echo of the Big Bang.

Lex Fridman (1:28:54.760)

Yeah, 13.7 billion years have gone by.

Alex Filippenko (1:28:57.400)

That's how long it's taken that light to reach us.

Lex Fridman (1:29:00.840)

But while it's been traveling that distance, the parts that it already traveled continue

Alex Filippenko (1:29:06.080)

to expand.

Lex Fridman (1:29:08.000)

So it's like you're walking on at an airport, you know, on one of these walkways and you're

Alex Filippenko (1:29:13.280)

walking along because you're trying to get to your terminal.

Lex Fridman (1:29:16.200)

But the walkway is continuing as well.

Alex Filippenko (1:29:19.240)

You end up traveling a greater distance or the same distance faster is another way of

Lex Fridman (1:29:24.160)

putting it, right?

Alex Filippenko (1:29:25.280)

That's why you get on one of these traveling walkways.

Lex Fridman (1:29:28.360)

So you get roughly a factor of pi, you know, but it's more like 3.2, I think.

Lex Fridman (1:29:33.560)

But when you work it all out, you multiply the number of years the universe has been

Lex Fridman (1:29:38.640)

in existence by, you know, three and a quarter or so.

Lex Fridman (1:29:42.520)

And that's how you get this 46 billion light year radius.

Lex Fridman (1:29:48.920)

But how is that, let me ask some nice dumb questions, how is that not traveling faster

Lex Fridman (1:29:56.000)

than the speed of light?

Alex Filippenko (1:29:57.000)

Yeah, it's not traveling faster than the speed of light because locally at any point, if

Alex Filippenko (1:30:01.160)

you were to measure the light, the photons zipping past, it would not be exceeding the

Lex Fridman (1:30:06.640)

speed of light.

Alex Filippenko (1:30:08.000)

The speed of light is a locally measured quantity.

Alex Filippenko (1:30:11.320)

After light has traversed some distance, if the rubber band keeps on stretching, then

Alex Filippenko (1:30:16.280)

yes, it looks like the light traveled a greater distance than it would have had the space

Lex Fridman (1:30:23.680)

not been expanding.

Lex Fridman (1:30:25.240)

But locally, it never was exceeding the speed of light.

Alex Filippenko (1:30:28.180)

It's just that the distance through which it already traveled then went off and expanded

Alex Filippenko (1:30:32.600)

on its own some more.

Lex Fridman (1:30:35.360)

And if you give the light credit, so to speak, for having traversed that distance, well,

Alex Filippenko (1:30:40.960)

then it looks like it's going faster than the speed of light.

Lex Fridman (1:30:43.680)

But that's not how speed works.

Lex Fridman (1:30:47.480)

And in relativity, also, the other thing that is interesting is that if you take two ping

Alex Filippenko (1:30:54.720)

pong balls that are sufficiently far apart, especially in an accelerating universe, you

Alex Filippenko (1:30:59.280)

can easily have them moving apart from one another faster than the speed of light.

Lex Fridman (1:31:03.400)

So take two ping pong balls that were originally 400,000 kilometers from each other and let

Alex Filippenko (1:31:09.680)

every centimeter in your rubber band expand to two in one second.

Lex Fridman (1:31:14.280)

Then suddenly, this 400,000 kilometer distance is 800,000 kilometers.

Alex Filippenko (1:31:20.720)

It went out by 400,000 kilometers in one second.

Lex Fridman (1:31:24.480)

That exceeds the 300,000 kilometer per second speed of light.

Lex Fridman (1:31:29.620)

But that light limit, that particle limit in special relativity, applies to objects

Lex Fridman (1:31:36.240)

moving through a preexisting space.

Alex Filippenko (1:31:39.640)

There's nothing in either special or general relativity that prevents space itself from

Lex Fridman (1:31:46.160)

expanding faster than the speed of light.

Alex Filippenko (1:31:48.680)

That's no problem.

Alex Filippenko (1:31:49.680)

Einstein wouldn't have had a problem with a universe as observed now by cosmologists.

Alex Filippenko (1:31:55.760)

Yeah, I'm not sure I'm yet ready to deal emotionally with expanding space.

Lex Fridman (1:32:04.240)

That to me is one of the most awe inspiring things, starting from the Big Bang.

Alex Filippenko (1:32:09.560)

It's definitely abstract.

Lex Fridman (1:32:11.480)

Space itself is expanding.

Alex Filippenko (1:32:13.320)

Right.

Lex Fridman (1:32:14.320)

Could you, can we talk about the Big Bang a little bit?

Alex Filippenko (1:32:18.600)

Sure.

Lex Fridman (1:32:19.600)

Yeah, yeah.

Alex Filippenko (1:32:20.600)

What, so like the entirety of it, the universe, was very small.

Lex Fridman (1:32:27.360)

Right.

Lex Fridman (1:32:28.360)

But it was not a point.

Lex Fridman (1:32:29.360)

It was not a point.

Alex Filippenko (1:32:31.160)

Because if we live in what's called a closed universe now, a sphere or the three dimensional

Alex Filippenko (1:32:36.080)

version of that would be a hypersphere, then regardless of how far back in time you go,

Alex Filippenko (1:32:43.120)

it was always that topological shape.

Lex Fridman (1:32:45.880)

You can't turn a point suddenly into a shell, okay?

Alex Filippenko (1:32:49.320)

It always had to be a shell.

Lex Fridman (1:32:52.020)

So when people say, well, the universe started out as a point, that's being kind of flippant,

Alex Filippenko (1:32:57.040)

kind of glib.

Lex Fridman (1:32:58.160)

It didn't really.

Alex Filippenko (1:32:59.160)

It just started out at a very high density.

Lex Fridman (1:33:02.480)

And we don't know actually whether it was finite or infinite, I think personally that

Alex Filippenko (1:33:06.880)

it was finite at the time, but it expanded very, very quickly.

Alex Filippenko (1:33:10.400)

Indeed, if it exponentiated and continued in some places to exponentiate, then it could

Alex Filippenko (1:33:16.300)

in fact be infinite right now.

Lex Fridman (1:33:18.140)

And most cosmologists think that it is infinite.

Alex Filippenko (1:33:20.480)

Wait, wait, wait.

Lex Fridman (1:33:21.480)

Yeah, sorry.

Lex Fridman (1:33:22.480)

What infinite, which dimension, mass, size?

Lex Fridman (1:33:25.040)

Infinite in space.

Alex Filippenko (1:33:26.440)

Infinite in space.

Lex Fridman (1:33:27.440)

And by that I mean that if you were trying to measure.

Alex Filippenko (1:33:29.560)

There's no boundary.

Lex Fridman (1:33:30.560)

There's no light to measure its size.

Alex Filippenko (1:33:33.280)

You'd never be able to measure its size because it would always be bigger than the distance

Lex Fridman (1:33:37.400)

light can travel.

Alex Filippenko (1:33:39.260)

That's what you get in a universe that's accelerating in its expansion.

Lex Fridman (1:33:42.760)

Okay.

Lex Fridman (1:33:43.760)

But if a thing was a hypersphere, it's very small, not a point, how can that thing be

Lex Fridman (1:33:50.280)

infinite?

Alex Filippenko (1:33:51.280)

Well, it expands exponentially.

Lex Fridman (1:33:54.040)

That's what the inflation theory is all about.

Alex Filippenko (1:33:56.200)

Indeed, at your home institution, Alan Guth is one of the originators of the whole inflationary

Alex Filippenko (1:34:01.400)

universe idea, along with Andre Linde at Stanford University here in the Bay Area.

Lex Fridman (1:34:07.280)

And others, Alexei Starobinsky and others had similar sorts of ideas.

Lex Fridman (1:34:11.240)

But in an exponentially expanding universe, if you actually try to make this measurement,

Alex Filippenko (1:34:17.400)

you send light out to try to see it curve back around and hit you in the back of the

Lex Fridman (1:34:22.720)

head.

Lex Fridman (1:34:23.720)

But in an exponentially expanding universe, the amount of space remaining to be traversed

Lex Fridman (1:34:29.360)

is always a bigger and bigger quantity.

Lex Fridman (1:34:32.400)

So you'll never get there from here.

Lex Fridman (1:34:34.520)

You'll never reach the back of your head.

Lex Fridman (1:34:35.920)

So observationally or operationally, it can be thought of as being infinite.

Lex Fridman (1:34:41.160)

That's one of the best definitions of infinity, by the way.

Lex Fridman (1:34:43.680)

What's that?

Lex Fridman (1:34:44.680)

That's one of the best sort of physical manifestations of infinity.

Alex Filippenko (1:34:49.520)

Yeah, yeah.

Lex Fridman (1:34:50.640)

Because you have to ask, how would you actually measure it?

Alex Filippenko (1:34:53.200)

Now, I sometimes say to my cosmology theoretical friends, well, if I were God and I were outside

Alex Filippenko (1:34:58.920)

this whole thing and I took a godlike slice in time, wouldn't it be finite no matter how

Lex Fridman (1:35:05.140)

big it is?

Lex Fridman (1:35:06.140)

And they object and they say, Alex, you can't be outside and take a godlike slice of time,

Lex Fridman (1:35:13.000)

you know?

Lex Fridman (1:35:14.000)

Because there's nothing outside.

Alex Filippenko (1:35:15.000)

Well, I'm not, you know, or also, you know, what slice of time you're taking depends on

Lex Fridman (1:35:22.000)

your motion.

Lex Fridman (1:35:23.000)

And that's true even in special relativity that slices of time get tilted, in a sense,

Alex Filippenko (1:35:28.680)

if you're moving quickly, the axes, x and t actually become tilted, not perpendicular

Alex Filippenko (1:35:36.100)

to one another.

Lex Fridman (1:35:37.920)

And you can look at Brian Greene's books and lectures and other things where he imagines

Alex Filippenko (1:35:43.320)

taking a loaf of bread and slicing it in units of time as you progress forward.

Lex Fridman (1:35:50.120)

But then if you're zipping along relative to that loaf of bread, the slices of time

Alex Filippenko (1:35:55.160)

actually become tilted.

Lex Fridman (1:35:57.400)

And so it's not even clear what slices of time mean.

Lex Fridman (1:36:00.700)

But I'm an observational astronomer, I know which end of the telescope to look through.

Lex Fridman (1:36:05.040)

And the way I understand the infinity is, as I just told you, that operationally or

Alex Filippenko (1:36:09.480)

observationally, there'd be no way of seeing that it's a finite universe, of measuring

Lex Fridman (1:36:16.340)

a finite universe.

Lex Fridman (1:36:17.340)

And so in that sense, it's infinite, even if it started out as a finite little dot.

Lex Fridman (1:36:25.600)

Not a dot, I'm sorry, a finite little hypersphere.

Lex Fridman (1:36:29.720)

But it didn't really start out there because what happened before that?

Lex Fridman (1:36:37.800)

Well, we don't know.

Lex Fridman (1:36:38.800)

So this is where it gets into a lot of speculation.

Lex Fridman (1:36:41.480)

Let's go, I mean...

Alex Filippenko (1:36:42.480)

Let's go there.

Lex Fridman (1:36:43.480)

Okay, sure.

Alex Filippenko (1:36:44.480)

So, you know...

Alex Filippenko (1:36:45.480)

The idea of what happened before t equals zero and whether there are other universes

Alex Filippenko (1:36:50.440)

out there, I like to say that these are sort of on the boundaries of science.

Alex Filippenko (1:36:55.160)

They're not just ideas that we wake up at three in the morning to go to the bathroom

Lex Fridman (1:36:58.820)

and say, oh, well, let's think about what happened before the Big Bang or let there

Lex Fridman (1:37:02.160)

be a multiplicity of universes.

Alex Filippenko (1:37:04.880)

In other words, we have real testable physics that we can use to draw certain conclusions

Lex Fridman (1:37:12.280)

that are plausibility arguments based on what we know.

Alex Filippenko (1:37:16.400)

Now, admittedly, there are not really direct tests of these hypotheses.

Lex Fridman (1:37:24.160)

That's why I call them hypotheses.

Alex Filippenko (1:37:26.040)

They're not really elevated to a theory because a theory in science is really something that

Lex Fridman (1:37:30.980)

has a lot of experimental or observational support behind it.

Lex Fridman (1:37:34.960)

So they're hypotheses, but they're not unreasonable hypotheses based on what we know about general

Lex Fridman (1:37:41.400)

relativity and quantum physics.

Lex Fridman (1:37:44.240)

And they may have indirect tests in that if you adopt this hypothesis, then there might

Alex Filippenko (1:37:49.720)

be a bunch of things you expect of the universe, and lo and behold, that's what we measure.

Lex Fridman (1:37:54.560)

But we're not actually measuring anything at t less than zero, or we're not actually

Alex Filippenko (1:38:00.620)

measuring the presence of another universe in this multiverse, and yet there are these

Alex Filippenko (1:38:05.780)

indirect ideas that stem forth.

Lex Fridman (1:38:09.180)

So it's hard to prove uniqueness, and it's hard to completely convince oneself that a

Alex Filippenko (1:38:15.560)

certain hypothesis must be true.

Lex Fridman (1:38:19.540)

But the more and more tests you have that it satisfies, let's say there are 50 predictions

Alex Filippenko (1:38:24.420)

it makes, and 49 of them are things that you can measure.

Lex Fridman (1:38:30.360)

And then the 50th one is the one where you want to measure the actual existence of that

Alex Filippenko (1:38:35.640)

other universe, or what happened before t equals zero, and you can't do that.

Lex Fridman (1:38:41.840)

But you've satisfied 49 of the other testable predictions, and so that's science, right?

Alex Filippenko (1:38:49.000)

Now a conventional condensed matter physicist or someone who deals with real data in the

Alex Filippenko (1:38:53.680)

laboratory might say, oh, you cosmologists, that's not really science because it's not

Alex Filippenko (1:38:58.040)

directly testable, but I would say it's sort of testable.

Lex Fridman (1:39:02.480)

But it's not completely testable, and so it's at the boundary, but it's not like we're coming

Alex Filippenko (1:39:06.040)

up with these crazy ideas, among them quantum fluctuations out of nothing, and then inflating

Alex Filippenko (1:39:11.980)

into a universe with, you might say, well, you created a giant amount of energy.

Lex Fridman (1:39:16.720)

But in fact, this quantum fluctuation out of nothing in a quantum way violates the conservation

Lex Fridman (1:39:22.800)

of energy.

Lex Fridman (1:39:23.800)

But who cares?

Lex Fridman (1:39:24.800)

That was a classical law anyway.

Lex Fridman (1:39:26.600)

And then an inflating universe maintains whatever energy it had, be it zero or some infinitesimal

Lex Fridman (1:39:32.760)

amount.

Alex Filippenko (1:39:33.760)

In a sense, the stuff of the universe has a positive energy, but there's a negative

Lex Fridman (1:39:38.800)

gravitational energy associated with it.

Alex Filippenko (1:39:41.280)

It's like I drop an apple.

Alex Filippenko (1:39:43.000)

I got kinetic energy, energy of motion out of that, but I did work on it to bring it

Alex Filippenko (1:39:47.880)

to that height.

Lex Fridman (1:39:49.800)

So by going down and gaining energy of motion, positive one, two, three, four, five units

Alex Filippenko (1:39:55.880)

of kinetic energy, it's also gaining or losing, depending on how you want to think of it,

Alex Filippenko (1:40:01.160)

negative one, two, three, four, five units of potential energy, so the total energy remains

Alex Filippenko (1:40:06.200)

the same.

Alex Filippenko (1:40:07.240)

An inflating universe can do that, or other physicists say that energy isn't conserved

Alex Filippenko (1:40:12.260)

in general relativity.

Lex Fridman (1:40:13.840)

That's another way out of creating a universe out of nothing.

Lex Fridman (1:40:17.520)

But the point is that this is all based on reasonably well tested physics, and although

Alex Filippenko (1:40:22.920)

these extrapolations seem kind of outrageous at first, they're not completely outrageous.

Alex Filippenko (1:40:30.080)

They're within the realm of what we call science already.

Lex Fridman (1:40:33.600)

And maybe some young whippersnapper will be able to figure out a way to directly test

Lex Fridman (1:40:39.080)

what happened before T equals zero or to test for the presence of these other universes,

Lex Fridman (1:40:44.060)

but right now we don't have a way of doing that.

Lex Fridman (1:40:46.460)

So speaking of young whippersnappers, Roger Penrose.

Lex Fridman (1:40:52.040)

So he kind of has a, you know, idea that we, there may be some information that travels

Alex Filippenko (1:40:58.240)

from whatever the heck happened before the Big Bang.

Lex Fridman (1:41:00.760)

Yeah, maybe.

Alex Filippenko (1:41:01.760)

I kind of doubt it.

Lex Fridman (1:41:03.320)

So do you think it's possible to detect something, like actually experimentally be able to detect

Alex Filippenko (1:41:09.480)

some, I don't know what it is, radiation, some sort of...

Alex Filippenko (1:41:13.640)

Yeah, and the cosmic microwave background radiation, there may be ways of doing that.

Lex Fridman (1:41:18.240)

But is it, is it philosophically or practically possible to detect signs that this was before

Alex Filippenko (1:41:25.480)

the Big Bang or is it, or is it what you said, which is like everything we observe will,

Lex Fridman (1:41:32.000)

as we currently understand, will have to be a creation of this particular observable universe?

Lex Fridman (1:41:36.200)

Yeah.

Alex Filippenko (1:41:37.200)

I mean, you know, if you, it's very difficult to answer right now because we don't have

Alex Filippenko (1:41:40.480)

a single verified, fully self consistent, experimentally tested quantum theory of gravity.

Alex Filippenko (1:41:48.360)

Right.

Lex Fridman (1:41:49.360)

And of course the beginning of the universe is a large amount of stuff in a very small

Alex Filippenko (1:41:53.600)

space.

Lex Fridman (1:41:54.600)

Yeah.

Lex Fridman (1:41:55.600)

So you need both quantum mechanics and general relativity.

Alex Filippenko (1:41:57.120)

Same thing if our universe re collapses and then bounces back to another Big Bang.

Alex Filippenko (1:42:01.400)

You know, there's also ideas there that some of the information leaks through or survives.

Alex Filippenko (1:42:06.320)

I don't know that we can answer that question right now because we don't have a quantum

Alex Filippenko (1:42:11.560)

theory of gravity that most physicists believe in.

Lex Fridman (1:42:15.360)

And belief is perhaps the wrong word that most physicists trust because the experimental

Alex Filippenko (1:42:20.600)

evidence favors it.

Lex Fridman (1:42:22.480)

Yeah.

Lex Fridman (1:42:23.480)

Right?

Lex Fridman (1:42:24.480)

Yeah.

Alex Filippenko (1:42:25.480)

There are various forms of string theory.

Lex Fridman (1:42:26.480)

There's quantum loop gravity.

Alex Filippenko (1:42:27.480)

There are various ideas, but which, if any, will be the one that survives the test of

Lex Fridman (1:42:33.240)

time and more importantly, within that, the test of experiment and observation.

Alex Filippenko (1:42:38.840)

Yeah.

Lex Fridman (1:42:39.840)

So my own feeling is probably these things don't survive.

Alex Filippenko (1:42:43.280)

I don't think we've seen any evidence in the cosmic microwave background radiation

Lex Fridman (1:42:47.400)

of information leaking through.

Alex Filippenko (1:42:50.520)

Similarly, the one way or one of the few ways in which we might test for the presence of

Alex Filippenko (1:42:55.880)

other universes is if they were to collide with ours, that would leave a pattern, a temperature

Alex Filippenko (1:43:02.200)

signature in the cosmic microwave background radiation.

Alex Filippenko (1:43:05.920)

Some astrophysicists claim to have found it, but in my opinion, it's not statistically

Lex Fridman (1:43:10.200)

significant to the level that would be necessary to have such an amazing claim, right?

Alex Filippenko (1:43:17.280)

It's just a 5% chance that the microwave background had that distribution just by chance.

Alex Filippenko (1:43:22.960)

5% isn't very long odds if you're claiming that instead that you're finding evidence

Lex Fridman (1:43:32.680)

from another universe.

Alex Filippenko (1:43:33.680)

I mean, it's like if the Large Hadron Collider people had claimed after gathering enough

Alex Filippenko (1:43:39.760)

data to show the Higgs particle when there was a 5% chance it could be just a statistical

Alex Filippenko (1:43:47.780)

fluctuation in their data.

Alex Filippenko (1:43:50.040)

No, they required 5 sigma, 5 standard deviations, which is roughly one chance in 2 million that

Alex Filippenko (1:43:57.640)

this is a statistical fluctuation of no physical greater significance.

Lex Fridman (1:44:04.280)

Extraordinary claims require extraordinary evidence.

Alex Filippenko (1:44:05.560)

There you go.

Lex Fridman (1:44:06.560)

It all boils down to that.

Lex Fridman (1:44:07.560)

And the greater your claim, the greater is the evidence that is needed and the more evidence

Lex Fridman (1:44:12.420)

you need from independent ways of measuring or of coming to that deduction.

Alex Filippenko (1:44:20.640)

A good example was the accelerating universe.

Alex Filippenko (1:44:23.560)

When we found evidence for it in 1998 with supernovae with exploding stars, it was great

Alex Filippenko (1:44:29.840)

that there were two teams that lent some credibility to the discovery.

Lex Fridman (1:44:34.240)

But it was not until other astrophysicists used not only that technique, but more importantly,

Alex Filippenko (1:44:41.200)

other independent techniques that had their own potential sources of systematic error

Lex Fridman (1:44:46.760)

or whatever.

Lex Fridman (1:44:47.940)

But they all came to the same conclusion and that started giving a much more complete picture

Alex Filippenko (1:44:52.760)

of what was going on and a picture in which most astrophysicists quickly gained confidence.

Alex Filippenko (1:44:59.220)

That's why that idea caught on so quickly is that there were other physicists and astronomers

Alex Filippenko (1:45:06.200)

doing observations completely independent of supernovae that seemed to indicate the

Alex Filippenko (1:45:11.640)

same thing.

Lex Fridman (1:45:12.640)

Yeah.

Alex Filippenko (1:45:13.640)

That period of your life that work with an incredible team of people that won the Nobel

Lex Fridman (1:45:22.480)

Prize is just fascinating work.

Alex Filippenko (1:45:25.880)

Oh gosh.

Alex Filippenko (1:45:26.880)

Never in my wildest dreams as a kid did I think that I would be involved, much less

Lex Fridman (1:45:33.280)

so heavily involved, in a discovery that's so revolutionary.

Alex Filippenko (1:45:37.880)

As a kid, as a scientist, if you're realistic, once you learn a little bit more about how

Alex Filippenko (1:45:41.760)

science is done and you're not going to win a Nobel Prize and be the next Newton or Einstein

Alex Filippenko (1:45:45.840)

or whatever, you just hope that you'll contribute something to humankind's understanding of

Lex Fridman (1:45:51.020)

how nature works and you'll be satisfied with that.

Lex Fridman (1:45:55.040)

But here I was in the right place at the right time, a lot of luck, a lot of hard work, and

Alex Filippenko (1:46:01.040)

there it was.

Lex Fridman (1:46:02.180)

We discovered something that was really amazing and that was the greatest thrill, right?

Alex Filippenko (1:46:08.400)

I couldn't have asked for anything more than being involved in that discovery.

Lex Fridman (1:46:14.060)

So the couple of teams, the Supernova Cosmology Project and the HiZ Supernova Search Team,

Lex Fridman (1:46:20.200)

what was the Nobel Prize given for?

Alex Filippenko (1:46:21.960)

It was given for the discovery of the accelerating expansion of the universe, not for the elucidation

Alex Filippenko (1:46:27.280)

of what dark energy is or what causes that expansion, that acceleration, be it universes

Lex Fridman (1:46:33.040)

on the outside or whatever, it was only for the observational fact.

Lex Fridman (1:46:36.840)

So first of all, what is the accelerating universe?

Lex Fridman (1:46:39.200)

So the accelerating universe is simply that if we look at the galaxies moving away from

Alex Filippenko (1:46:45.640)

us right now, we would expect them to be moving away more slowly than they were billions of

Lex Fridman (1:46:52.120)

years ago.

Alex Filippenko (1:46:53.120)

That's because galaxies have visible matter, which is gravitationally attractive, and dark

Alex Filippenko (1:46:58.080)

matter of an unknown sort that holds galaxies together and holds clusters of galaxies together.

Lex Fridman (1:47:04.600)

And of course, they then pull on one another and they would tend to retard the expansion

Lex Fridman (1:47:09.400)

of the universe.

Alex Filippenko (1:47:10.400)

Just as when I toss an apple up, even ignoring air resistance, the mutual gravitational attraction

Lex Fridman (1:47:17.280)

between Earth and the apple slows the apple down.

Alex Filippenko (1:47:20.640)

If that attraction is great enough, then the apple will someday stop and even come back.

Lex Fridman (1:47:24.800)

The Big Crunch, you could call it, or the Gnab Gibb, which is Big Bang backwards, right?

Alex Filippenko (1:47:29.080)

That's what could have happened to the universe.

Lex Fridman (1:47:30.520)

But even if the universe's original expansion energy was so great that it avoids the Big

Alex Filippenko (1:47:36.860)

Crunch, that's like an apple thrown at Earth's escape speed.

Lex Fridman (1:47:39.800)

It's like the rockets that go to Mars someday, right, with people.

Alex Filippenko (1:47:47.040)

Even then, you'd expect the universe to be slowing down with time.

Lex Fridman (1:47:50.800)

But we looked back through the history of the universe by looking at progressively more

Alex Filippenko (1:47:55.600)

distant galaxies and by seeing that the evolution of this expansion rate is that in the first

Lex Fridman (1:48:06.000)

nine billion years, yeah, it was slowing down.

Lex Fridman (1:48:09.340)

But in the last five billion years, it's been speeding up.

Lex Fridman (1:48:13.720)

So who asked for that, right, you know?

Alex Filippenko (1:48:17.320)

I think it's interesting to talk about a little bit of the human story of the Nobel Prize,

Lex Fridman (1:48:22.080)

which is, I mean, it's fascinating.

Alex Filippenko (1:48:24.920)

It's a really, first of all, the prize itself.

Alex Filippenko (1:48:27.960)

It's kind of fascinating on the psychological level that prizes, I know we kind of think

Alex Filippenko (1:48:34.040)

that prizes don't matter, but somehow they kind of focus the mind about some of the most

Lex Fridman (1:48:38.720)

special things we've accomplished.

Alex Filippenko (1:48:39.720)

They do.

Lex Fridman (1:48:40.720)

It's the recognition, the funding, you know.

Lex Fridman (1:48:43.200)

And also inspiration for, like I said, when I was a little kid, thinking about the Nobel

Lex Fridman (1:48:47.580)

Prize, like I didn't, you know, it inspires millions of young scientists.

Alex Filippenko (1:48:53.600)

At the same time, there's a sadness to it a little bit that, especially in the field,

Alex Filippenko (1:48:59.200)

like depending on the field, but experimental fields that involve teams of, I don't know,

Alex Filippenko (1:49:04.400)

sometimes hundreds of brilliant people, the Nobel Prize is only given to just a handful.

Lex Fridman (1:49:12.200)

That's right.

Lex Fridman (1:49:13.200)

Is it maxed at three?

Lex Fridman (1:49:14.760)

Yeah.

Alex Filippenko (1:49:15.760)

Yeah.

Lex Fridman (1:49:16.760)

And it's not even written in Alfred Nobel's will, it turns out.

Alex Filippenko (1:49:18.920)

One of our teammates looked into it in a museum in Stockholm when we went there for Nobel

Lex Fridman (1:49:23.960)

Week in 2011.

Alex Filippenko (1:49:25.840)

The leaders who got the prize formally knew that without the rest of us working hard in

Lex Fridman (1:49:30.560)

the trenches, the result would not have been discovered.

Lex Fridman (1:49:35.080)

So they invited us to participate in Nobel Week.

Lex Fridman (1:49:37.560)

And so one of the team members looked in the will and it's not there.

Alex Filippenko (1:49:41.320)

It's just tradition.

Lex Fridman (1:49:42.320)

That's interesting.

Lex Fridman (1:49:43.320)

But it's archaic, you know, that's the way science used to be done.

Lex Fridman (1:49:47.080)

It's not the way a lot of science is done now.

Lex Fridman (1:49:49.320)

And you look at gravitational wave discovery, which was, you know, recognized with the Nobel

Alex Filippenko (1:49:54.700)

Prize in 2017, Ray Weiss at MIT got it and Kip Thorne and Barry Barish at Caltech.

Lex Fridman (1:50:03.720)

And Ron Drever, one of the masterminds, had passed away earlier in the year.

Lex Fridman (1:50:07.560)

So again, one of the rules of Nobel is that it's not given posthumously, or at least the

Alex Filippenko (1:50:13.840)

one exception might be if they've made their decision and they're busy making their press

Alex Filippenko (1:50:17.960)

releases right before October, the first week in October or whatever, and then the person

Alex Filippenko (1:50:23.460)

passes away.

Lex Fridman (1:50:24.460)

I think they don't change their minds then.

Lex Fridman (1:50:25.920)

But yeah, you know, it doesn't square with today's reality that a lot of science is done

Lex Fridman (1:50:32.460)

by big teams, in that case, a team of a thousand people.

Alex Filippenko (1:50:35.800)

In our case, it was two teams consisting of about 50 people.

Lex Fridman (1:50:40.160)

And we used techniques that were arguably developed in part by people who, astrophysicists

Alex Filippenko (1:50:46.120)

who weren't even on those two papers, I mean, some of them were, but other papers were written

Alex Filippenko (1:50:51.320)

by other people, you know, and so it's like we're standing on the shoulders of giants.

Lex Fridman (1:50:56.560)

And none of those people was officially recognized.

Lex Fridman (1:50:59.520)

And to me, it was okay.

Alex Filippenko (1:51:01.800)

You know, again, it was the thrill of doing the work and ultimately the work, the discovery

Lex Fridman (1:51:06.560)

was recognized with the prize.

Lex Fridman (1:51:08.760)

And you know, we got to participate in Nobel week and, you know, it's okay with me.

Alex Filippenko (1:51:14.360)

I've known other physicists whose lives were ruined because they did not get the Nobel

Alex Filippenko (1:51:20.500)

prize and they felt strongly that they should have.

Alex Filippenko (1:51:23.840)

Ralph Alpher of the Alpher beta gamma paper predicting the microwave background radiation,

Alex Filippenko (1:51:31.560)

we should have gotten it.

Lex Fridman (1:51:33.400)

His advisor Gamoff was dead by that point.

Lex Fridman (1:51:36.600)

But you know, Penzias and Wilson got it for the discovery and an Alpher, apparently from

Lex Fridman (1:51:42.560)

colleagues who knew him well, I've talked to them.

Alex Filippenko (1:51:45.120)

His life was ruined by this.

Lex Fridman (1:51:46.760)

He just, it just not at his innards so much.

Alex Filippenko (1:51:50.840)

It's very possible that in a small handful of people, even three, that you would be one

Lex Fridman (1:51:56.040)

of the Nobel, one of the winners of the Nobel prize.

Alex Filippenko (1:51:59.440)

That doesn't weigh heavy on you.

Alex Filippenko (1:52:00.920)

Well, you know, there were the two team leaders, Saul Perlmutter and Brian Schmidt.

Lex Fridman (1:52:05.080)

And usually there's the team leaders that are recognized.

Lex Fridman (1:52:07.600)

And then Adam Rees was my postdoc.

Alex Filippenko (1:52:10.520)

First author, I guess.

Lex Fridman (1:52:11.520)

Yeah.

Alex Filippenko (1:52:12.520)

First author.

Lex Fridman (1:52:13.520)

I was second author of that paper.

Alex Filippenko (1:52:14.520)

Yeah.

Lex Fridman (1:52:15.520)

So I was his direct mentor at the time.

Alex Filippenko (1:52:16.520)

Although he was, you know, one of these people who just, you know, runs with things.

Alex Filippenko (1:52:19.920)

He was an MIT undergraduate by the way, Harvard graduate student, and then a postdoc as a

Lex Fridman (1:52:26.200)

so called Miller fellow for basic research and science at Berkeley, something that I

Lex Fridman (1:52:30.840)

was back in 84 to 86.

Lex Fridman (1:52:33.240)

But you're, you know, you're largely a free agent, but he worked quite closely with me

Lex Fridman (1:52:37.680)

and he came to Berkeley to work with me and on Schmidt's team, he was charged with analyzing

Alex Filippenko (1:52:43.000)

the data and he measured the brightnesses of these distant supernovae showing that they're

Lex Fridman (1:52:48.440)

fainter and thus more distant than anticipated.

Lex Fridman (1:52:51.480)

And that led to this conclusion that the universe had to have accelerated in order to push them

Lex Fridman (1:52:56.420)

out to such great distances.

Lex Fridman (1:52:58.520)

And I was shocked when he showed me the data, the results of his calculations and measurements.

Lex Fridman (1:53:04.800)

But it's very, you know, so he deserved it.

Lex Fridman (1:53:07.000)

And on Sol's team, Gerson Goldhaber deserved it.

Lex Fridman (1:53:10.440)

But he died, I think a year earlier in 2010, but that would have been four.

Lex Fridman (1:53:14.840)

And so, and me, well, I was on both teams, but, you know, was I number four, five, six,

Lex Fridman (1:53:21.720)

seven?

Alex Filippenko (1:53:22.720)

I don't know.

Alex Filippenko (1:53:23.720)

It's also very, so if I were to, it's possible that you're, I mean, I can make a very good

Alex Filippenko (1:53:28.800)

case for urine in the three.

Lex Fridman (1:53:31.400)

And does that, is that psychologically, I mean, listen, it weighs on me a little bit

Alex Filippenko (1:53:38.440)

because I don't know what to do with that.

Alex Filippenko (1:53:44.560)

Perhaps it should motivate the rethinking, like Time magazine started doing like, you

Alex Filippenko (1:53:51.120)

know, person of the year and like they would start doing like concepts and almost like

Alex Filippenko (1:53:56.120)

the black hole gets the Nobel prize or the universe gets the Nobel prize and here's the

Alex Filippenko (1:54:02.380)

list of people.

Lex Fridman (1:54:03.800)

So like, or like the Oscar that you could say, because it's a team effort now and it

Alex Filippenko (1:54:11.160)

should be redone.

Lex Fridman (1:54:12.160)

And the breakthrough prize in fundamental physics, which was started by Yuri Milner

Lex Fridman (1:54:16.360)

and Zuckerberg is involved in others as well, you know, uh, they recognize the larger team.

Lex Fridman (1:54:22.080)

Yeah, they, they recognize teams.

Lex Fridman (1:54:24.440)

And so in fact, both teams in the accelerating universe were recognized with the breakthrough

Lex Fridman (1:54:28.840)

prize in 2015.

Alex Filippenko (1:54:31.480)

Nevertheless, the same three people, Reese Perlmutter and Schmidt got the red carpet

Alex Filippenko (1:54:37.720)

rolled out for them and were at the big ceremony and shared half of the prize money.

Lex Fridman (1:54:43.480)

And the rest of us, roughly 50 shared the other half and didn't get to go to the ceremony.

Alex Filippenko (1:54:48.240)

So, but I, I feel for them, I mean, for the gravitational waves, it was a thousand people.

Lex Fridman (1:54:52.880)

What are they going to do?

Lex Fridman (1:54:53.880)

Invite everyone for the Higgs particle.

Alex Filippenko (1:54:55.980)

It was six to 8,000 physicists and engineers.

Alex Filippenko (1:54:58.760)

In fact, because of the whole issue of who gets it experimentally, that discovery still

Lex Fridman (1:55:04.500)

has not been recognized, right?

Alex Filippenko (1:55:06.620)

The theoretical work by Peter Higgs and, uh, Anglaire got recognized, but there was a troika

Alex Filippenko (1:55:13.240)

of other people who perhaps wrote the most complete paper and they were, they were left

Lex Fridman (1:55:18.240)

out and, um, another guy died, you know, and

Alex Filippenko (1:55:22.360)

it's hard.

Lex Fridman (1:55:23.360)

It's all of his heartbreak.

Lex Fridman (1:55:24.360)

And some people argue that the Nobel prize has been diluted too, because if you look

Alex Filippenko (1:55:28.400)

at Roger Penrose, you can make an argument that he should get the prize by himself.

Alex Filippenko (1:55:33.600)

Like it's just separate those, like he could have and should have, perhaps he should have

Lex Fridman (1:55:37.720)

perhaps gotten it with Hawking before Hawking's death, right?

Alex Filippenko (1:55:41.720)

The problem was Hawking radiation had not been detected, but you could argue that Hawking

Alex Filippenko (1:55:46.320)

made enough other fundamental contributions to the theoretical study of black holes and

Alex Filippenko (1:55:52.240)

the observed data were already good enough at the time of before Hawking's death.

Lex Fridman (1:55:57.920)

Okay.

Alex Filippenko (1:55:58.920)

I mean, the latest results by Reinhard Genzel's group is that they see the time dilation effect

Alex Filippenko (1:56:03.280)

of a star that's passing very close to the black hole in the middle of our galaxy.

Alex Filippenko (1:56:07.680)

That's cool, but, and it adds additional evidence, but hardly anyone doubted the existence of

Alex Filippenko (1:56:13.240)

the supermassive black hole and Andrea Gaz's group, I believe hadn't yet shown that relativistic

Alex Filippenko (1:56:18.880)

effect and yet she got part of the prize as well.

Lex Fridman (1:56:21.060)

So clearly it was given for the, the original evidence that was really good.

Lex Fridman (1:56:25.560)

And that evidence is at least a decade old, you know, so one could make the case for,

Alex Filippenko (1:56:30.320)

for Hawking, one could make the case that in 2016, when Mayor and Caloz won the Nobel

Alex Filippenko (1:56:37.460)

Prize for the discovery of the first exoplanet, 51B Pegasi, well, there was a fellow at Penn

Alex Filippenko (1:56:45.560)

State, Alex Wolszczan, who in 1992, three years preceding 1995, found a planet orbiting

Alex Filippenko (1:56:55.000)

a pulsar, a very weird kind of star, a neutron star, and that wouldn't have been a normal

Lex Fridman (1:56:59.920)

planet.

Alex Filippenko (1:57:00.920)

Sure.

Lex Fridman (1:57:01.920)

And so the Nobel committee, you know, they gave it for the discovery of planets around

Alex Filippenko (1:57:05.840)

normal sun like stars, but, but hell, you know, Wolszczan found a planet so they could

Alex Filippenko (1:57:11.160)

have given it to him as the third person instead of to Jim Peebles for the development of what's

Alex Filippenko (1:57:16.520)

called physical cosmology.

Alex Filippenko (1:57:18.360)

He's at Princeton, he deserved it, but they could have given Nobel for the development

Alex Filippenko (1:57:22.860)

of physical cosmology to Peebles and I would claim some other people were pretty important

Lex Fridman (1:57:27.920)

in that development as well.

Alex Filippenko (1:57:29.000)

You know, and they could have given it some other year.

Lex Fridman (1:57:32.600)

So there's, there's a lot of controversy.

Alex Filippenko (1:57:35.040)

I try not to dwell on it.

Lex Fridman (1:57:36.600)

Was I number three?

Alex Filippenko (1:57:37.760)

Probably not.

Lex Fridman (1:57:38.760)

You know, Adam Riess did the work.

Alex Filippenko (1:57:40.680)

You know, I helped bounce ideas off of him, but we wouldn't have had the result without

Lex Fridman (1:57:46.040)

him.

Alex Filippenko (1:57:47.040)

Yeah.

Lex Fridman (1:57:48.040)

And I was on both teams for reasons, I mean, you know, I, the style of the first team,

Alex Filippenko (1:57:53.360)

the supernova cosmology project didn't match mine.

Alex Filippenko (1:57:56.320)

They came largely from experimental high energy particle physics, physics where there's these

Alex Filippenko (1:58:00.520)

hierarchical teams and stuff and it's hard for the little guy to have a say, at least

Lex Fridman (1:58:05.440)

that's what I kind of thought.

Alex Filippenko (1:58:06.960)

Whereas the team of astronomers led by Brian Schmidt was first of all, a bunch of my friends

Lex Fridman (1:58:12.200)

and they grew up as astronomers making contributions on little teams and we decided to band together,

Lex Fridman (1:58:18.320)

but all of us had our voices heard.

Lex Fridman (1:58:20.440)

So it was sort of a culture, a style that I preferred really.

Lex Fridman (1:58:25.480)

But let me tell you a story at the Nobel banquet, okay?

Alex Filippenko (1:58:30.240)

I'm sitting there between two physicists who are members of the committee of the Swedish

Alex Filippenko (1:58:35.020)

National Academy of Sciences, you know, and I strategically kept, you know, offering them

Lex Fridman (1:58:39.920)

wine and stuff during this long drawn out Nobel ceremony, right?

Lex Fridman (1:58:45.080)

And I got them to be pretty talkative and then in a polite diplomatic way, I started

Alex Filippenko (1:58:50.080)

asking them pointed questions and basically they admitted that if there are four or more

Alex Filippenko (1:58:55.840)

people equally deserving, they wait for one of them to die or they just don't give the

Lex Fridman (1:59:01.600)

prize at all when it's unclear who the three are, at least unclear to them.

Lex Fridman (1:59:07.040)

But unclear to them, they're not even right part of the time.

Alex Filippenko (1:59:12.400)

I mean, Jocelyn Bell discovered pulsars with a radio antenna, a set of radio antennas that

Alex Filippenko (1:59:20.920)

her advisor Anthony Hewish conceived and built, so he deserves some credit, but he didn't

Lex Fridman (1:59:28.800)

discover the pulsar.

Alex Filippenko (1:59:30.520)

She did.

Lex Fridman (1:59:31.520)

And his initial reaction to the data that she showed him was a condescending rubbish,

Alex Filippenko (1:59:38.400)

my dear.

Lex Fridman (1:59:39.400)

Yeah, I'm not kidding.

Alex Filippenko (1:59:41.400)

Now, I know Jocelyn Bell and she did not let this destroy her life.

Lex Fridman (1:59:46.960)

She won every other prize under the sun, okay?

Alex Filippenko (1:59:51.080)

Vera Rubin, arguably one of the discoverers of dark matter, although there, if you look

Alex Filippenko (1:59:57.320)

at the history, there were a number of people and that was the issue, I think there were

Alex Filippenko (20:02.840)

mass extinction, or at least an extinction of complex beings such as ourselves that require

Alex Filippenko (20:08.720)

quite special conditions unlike cockroaches and amoebas to survive, one of these civilization

Alex Filippenko (20:19.040)

changing asteroids is only one kilometer or so in diameter and bigger, and a true mass

Lex Fridman (20:25.000)

extinction event is 10 kilometers or larger.

Alex Filippenko (20:28.880)

Now it's true that we can find and track the orbits of asteroids that might be headed toward

Alex Filippenko (20:34.560)

Earth, and if we find them 50 or 100 years before they impact us, then clever applied

Alex Filippenko (20:39.860)

physicists and engineers can figure out ways to deflect them.

Lex Fridman (20:43.440)

But at some point, some comet will come in from the deep freeze of the solar system,

Lex Fridman (20:48.640)

and there we have very little warning, months to a year.

Lex Fridman (20:52.000)

What's the deep freeze, sorry to interrupt.

Alex Filippenko (20:54.120)

The deep freeze is sort of out beyond Neptune.

Alex Filippenko (20:57.080)

There's this thing called the Kuiper Belt, and it consists of a bunch of dirty ice balls

Alex Filippenko (21:03.440)

or icy dirt balls.

Lex Fridman (21:04.920)

It's the source of the comets that occasionally come close to the Sun.

Lex Fridman (21:08.920)

And then there's an even bigger area called the Scattered Disk, which is sort of a big

Alex Filippenko (21:13.760)

doughnut surrounding the solar system way out there from which other comets come.

Lex Fridman (21:17.840)

And then there's the Oort Cloud, W O O R T after Jan Oort, a Dutch astrophysicist, and

Alex Filippenko (21:25.840)

it's the better part of a light year away from the Sun, so a good fraction of the distance

Alex Filippenko (21:31.080)

to the nearest star, but that's like a trillion or 10 trillion comet like objects that occasionally

Alex Filippenko (21:37.640)

get disturbed by a passing star or whatever, and most of them go flying out of the solar

Alex Filippenko (21:41.560)

system, but some go toward the Sun, and they come in with little warning.

Lex Fridman (21:46.960)

By the time we can see them, they're only a year or two away from us.

Lex Fridman (21:53.240)

And moreover, not only is it hard to determine their trajectories sufficiently accurately

Alex Filippenko (21:59.080)

to know whether they'll hit a tiny thing like Earth, but outgassing from the comet of gases

Alex Filippenko (22:07.040)

when the ices sublimate, that outgassing can change the trajectory just because of conservation

Lex Fridman (22:13.600)

of momentum, right?

Alex Filippenko (22:14.600)

It's the rocket effect.

Lex Fridman (22:15.920)

Gases go out in one direction, the object moves in the other direction.

Lex Fridman (22:19.100)

And so since we can't predict how much outgassing there will be and in exactly what direction

Alex Filippenko (22:25.000)

because these things are tumbling and rotating and stuff, it's hard to predict the trajectory

Alex Filippenko (22:30.400)

with sufficient accuracy to know that it will hit.

Lex Fridman (22:33.280)

And you certainly don't want to deflect a comet that would have missed but you thought

Alex Filippenko (22:38.760)

it was going to hit and end up having it hit.

Lex Fridman (22:41.980)

That would be like the ultimate Charlie Brown goat instead of trying to be the hero, right?

Alex Filippenko (22:47.200)

He ended up being the goat.

Lex Fridman (22:50.960)

What would you do if it seemed like in a matter of months that there is some nonzero probability,

Lex Fridman (22:58.960)

maybe a high probability that there will be a collision?

Lex Fridman (23:02.480)

So from a scientific perspective, from an engineering perspective, I imagine you would

Alex Filippenko (23:06.680)

actually be in the room of people deciding what to do.

Lex Fridman (23:10.520)

What uh, philosophically too.

Lex Fridman (23:12.680)

It's a tough one, right?

Alex Filippenko (23:13.720)

Because if you only have a few months, that's not much time in which to deflect it.

Alex Filippenko (23:19.680)

Early detection and early action are key because when it's far away, you only have to deflect

Lex Fridman (23:27.920)

it by a tiny little angle.

Lex Fridman (23:30.320)

And then by the time it reaches us, the perpendicular motion is big enough to miss Earth.

Lex Fridman (23:37.160)

All you need is one radius or one diameter of the Earth, right?

Alex Filippenko (23:41.520)

That actually means that all you would need to do is slow it down so it arrives four minutes

Alex Filippenko (23:47.540)

later or speed it up so it arrives four minutes earlier and Earth will have moved through

Alex Filippenko (23:54.320)

one radius in that time.

Lex Fridman (23:56.400)

So it doesn't take much.

Lex Fridman (23:57.400)

But you can imagine if a thing is about to hit you, you have to deflect it 90 degrees

Lex Fridman (24:02.600)

or more, right?

Alex Filippenko (24:03.600)

You know, and you don't have much time to do so and you have to slow it down or speed

Lex Fridman (24:07.160)

it up a lot if that's what you're trying to do to it.

Lex Fridman (24:09.280)

And so decades is sufficient time, but months is not sufficient time.

Lex Fridman (24:14.680)

So at that point, I would think the name of the game would be to try to predict where

Alex Filippenko (24:20.200)

it would hit.

Lex Fridman (24:22.560)

And if it's in a heavily populated region, try to start an orderly evacuation perhaps.

Lex Fridman (24:33.440)

But you know, that might cause just so much panic that I'm, how would you do with New

Lex Fridman (24:37.720)

York City or Los Angeles or something like that, right?

Alex Filippenko (24:41.400)

I might have a different opinion a year ago, I'm a bit disheartened by, you know, in the

Lex Fridman (24:48.360)

movies, there's always extreme competence from the government.

Alex Filippenko (24:54.760)

Competence, yeah.

Lex Fridman (24:55.760)

Competence, yeah.

Lex Fridman (24:56.760)

But we expect extreme incompetence, if anything, right?

Lex Fridman (24:59.720)

Yes, no.

Lex Fridman (25:00.720)

So I'm quite disappointed.

Lex Fridman (25:02.240)

But sort of from a medical perspective, I think you're saying there, and a scientific

Alex Filippenko (25:07.000)

one, it's almost better to get better and better, maybe telescopes and data collection

Alex Filippenko (25:13.080)

to be able to predict the movement of these things, or like come up with totally new technologies

Alex Filippenko (25:17.920)

that you can imagine actually sending out, like probes out there to be able to sort of

Alex Filippenko (25:24.240)

almost have little finger sensors throughout our solar system to be able to detect stuff.

Alex Filippenko (25:29.680)

Well, that's right.

Alex Filippenko (25:30.680)

Yeah, monitoring the asteroid belt is very important and 99% of the so called near earth

Alex Filippenko (25:35.640)

objects ultimately come from the asteroid belt.

Lex Fridman (25:39.200)

And so there we can track the trajectories and even if there's a close encounter between

Alex Filippenko (25:43.640)

two asteroids which deflects one of them toward earth, it's unlikely to be on a collision

Alex Filippenko (25:48.640)

course with earth in the immediate future, it's more like tens of years, so that gives

Alex Filippenko (25:53.720)

us time.

Lex Fridman (25:54.860)

But we would need to improve our ability to detect the objects that come in from a great

Alex Filippenko (26:00.840)

distance.

Lex Fridman (26:01.840)

And those are much rarer, the comets come in, 1% of the collisions perhaps are with

Alex Filippenko (26:09.720)

comets that come in without any warning hardly.

Lex Fridman (26:16.380)

So that might be more like a billion or two billion years before one of those hits us.

Lex Fridman (26:23.280)

So maybe we have to worry about the sun getting brighter on that time scale.

Alex Filippenko (26:28.240)

I mean, there's the possibility that a star will explode near us in the next couple of

Alex Filippenko (26:34.760)

billion years.

Lex Fridman (26:35.760)

But over the course of the history of life on earth, the estimates are that maybe only

Alex Filippenko (26:46.680)

one of the mass extinctions was caused by a star blowing up in particular, a special

Alex Filippenko (26:54.520)

kind called a gamma ray burst, and I think it's the Ordovician–Silurian extinction

Alex Filippenko (27:03.080)

420 or so, 440 million years ago that is speculated to have come from one of these particular

Lex Fridman (27:09.240)

types of exploding stars called gamma ray bursts.

Lex Fridman (27:12.240)

But even there, the evidence is circumstantial.

Lex Fridman (27:15.680)

So those kinds of existential threats are reasonably rare.

Alex Filippenko (27:20.800)

The greater danger I think is civilization changing events where it's a much smaller

Alex Filippenko (27:28.040)

asteroid, which those are harder to detect, or a giant solar flare that shorts out the

Alex Filippenko (27:37.200)

grid in all of North America, let's say.

Alex Filippenko (27:40.880)

Now, astronomers are monitoring the sun 24 seven with various satellites and we can tell

Alex Filippenko (27:46.560)

when there's a flare or a coronal mass ejection and we can tell that in a day or two, a giant

Alex Filippenko (27:52.840)

bundle of energetic particles will arrive and twang the magnetic field of earth and

Alex Filippenko (27:58.080)

send all kinds of currents through long distance power lines and that's what shorts out the

Alex Filippenko (28:03.120)

transformers and transformers are expensive and hard to replace and hard to transport

Lex Fridman (28:09.800)

and all that kind of stuff.

Lex Fridman (28:10.800)

So if we can warn the power companies and they can shut down the grid before the big

Alex Filippenko (28:18.640)

bundle of particle hits, then we will have mitigated much of this.

Alex Filippenko (28:21.360)

Now for a big enough bundle of particles, you can get short circuits even over small

Alex Filippenko (28:27.080)

distance scales, so not everything will be saved, but at least the whole grid might not

Lex Fridman (28:32.680)

go out.

Lex Fridman (28:33.680)

So again, astronomers, I like to say, support your local astronomer, they may help someday

Alex Filippenko (28:40.400)

save humanity by telling the power companies to shut down the grid, finding the asteroid

Alex Filippenko (28:46.160)

50 or 100 years before it hits, then having clever physicists and engineers deflect it.

Lex Fridman (28:52.260)

So many of these cosmic threats, cosmic existential threats, we can actually predict and do something

Alex Filippenko (29:00.960)

about or observe before they hit and do something about.

Lex Fridman (29:05.360)

So it's terrifying to think that people would listen to this conversation.

Alex Filippenko (29:10.920)

It's like when you listen to Bill Gates talk about pandemics in his Ted talk a few years

Lex Fridman (29:14.600)

ago and realizing we should have supported our local astronomer more.

Alex Filippenko (29:19.480)

Well, I don't know whether it's more because as I said, I actually think human induced

Alex Filippenko (29:24.520)

threats or things that occur naturally on earth, either a natural pandemic or perhaps

Alex Filippenko (29:29.440)

a bioengineering type pandemic or something like a super volcano.

Alex Filippenko (29:36.120)

There was one event towed by I think it was 70 plus thousand years ago that caused a gigantic

Alex Filippenko (29:44.080)

decrease in temperatures on earth because it sent up so much soot that it blocked the

Lex Fridman (29:50.640)

sun.

Alex Filippenko (29:51.640)

It's the nuclear winter type disaster scenario that some people including Carl Sagan talked

Lex Fridman (29:55.420)

about decades ago.

Lex Fridman (29:57.440)

What we can see in the history of volcanic eruptions even more recently in the 19th century,

Alex Filippenko (2:00:00.520)

a number of people, four or more who had similar data and similar ideas at about the same time.

Alex Filippenko (2:00:06.480)

Rubin won every prize under the sun, the new big large scale survey telescope being built

Alex Filippenko (2:00:12.440)

in Chile is being renamed the Vera Rubin Telescope because she passed away in December of 2015,

Alex Filippenko (2:00:19.080)

I think.

Alex Filippenko (2:00:21.880)

You know, it'll conduct this survey, large scale survey with the Rubin Telescope.

Lex Fridman (2:00:26.620)

So she's been recognized, but never with the Nobel Prize.

Lex Fridman (2:00:30.120)

And I would say that to her credit, she did not let that consume her life either.

Lex Fridman (2:00:36.000)

And perhaps it was a bit easier because there had been no Nobel given for the discovery

Alex Filippenko (2:00:41.200)

of dark matter, whereas in the case of pulsars and Jocelyn Bell, there was a prize given

Alex Filippenko (2:00:46.840)

for the discovery of the freaking pulsars and she didn't get it.

Lex Fridman (2:00:50.560)

Well, I mean, what a travesty of justice.

Lex Fridman (2:00:53.080)

So I also think as a fan of fiction, as a fan of stories that the travesty and the tragedy

Lex Fridman (2:01:01.840)

and the unfairness and the tension of it is what makes the prize and similar prizes beautiful.

Alex Filippenko (2:01:11.240)

The decisions of other humans that result in dreams being broken and, you know, like

Alex Filippenko (2:01:19.200)

that's why we love the Olympics as so many, you know, people, athletes give their whole

Alex Filippenko (2:01:24.600)

life for this particular moment and then there's referee decisions and like little slips of

Lex Fridman (2:01:31.280)

here and there, like the little misfortunes that destroy entire dreams.

Lex Fridman (2:01:36.400)

And that's, it's, it's weird to say, but it feels like that makes the entirety of it even

Lex Fridman (2:01:42.360)

more special.

Alex Filippenko (2:01:43.360)

Yeah.

Lex Fridman (2:01:44.360)

If it was perfect, it wouldn't be interesting.

Alex Filippenko (2:01:46.720)

Humans like competition and they like heroes and unfortunately it gives the impression

Alex Filippenko (2:01:51.160)

to youngsters today that science is still done by white men with gray beards wearing

Alex Filippenko (2:01:57.720)

white lab coats.

Lex Fridman (2:01:59.200)

And I'm very pleased to see that this year, you know, Andrea Ghez, the fourth woman in

Alex Filippenko (2:02:04.080)

the history of the physics prize to have received it.

Lex Fridman (2:02:07.520)

And then two women, one at Berkeley, one elsewhere won the Nobel prize in chemistry without any

Alex Filippenko (2:02:14.000)

male co recipient.

Lex Fridman (2:02:16.040)

And so that's sending a message I think to girls that they can do science and they have

Alex Filippenko (2:02:21.400)

role models.

Alex Filippenko (2:02:23.600)

I think the breakthrough prize and other such prizes show that teams get recognized as well.

Lex Fridman (2:02:31.240)

And if you pay attention to the newspapers, you know, most of the good authors like, you

Alex Filippenko (2:02:37.120)

know, Dennis Overby of the New York Times and others said that these were teams of people

Lex Fridman (2:02:41.520)

and they, they emphasize that and, you know, they all played a role.

Lex Fridman (2:02:46.040)

And you know, maybe if some grad student hadn't soldered some circuit, maybe the whole thing

Alex Filippenko (2:02:49.920)

wouldn't have worked, you know.

Lex Fridman (2:02:52.220)

But still, you know, Ray Weiss and Kip Thorne was the theoretical, you know, impetus for

Alex Filippenko (2:02:59.800)

the whole search for gravitational waves, Barry Barish brought the MIT and Caltech teams

Alex Filippenko (2:03:05.860)

together to get them to cooperate at a time when the project was nearly dead from what

Alex Filippenko (2:03:11.080)

I understand and contributed greatly to the experimental setup as well.

Alex Filippenko (2:03:16.120)

He's a great experimental physicist, but he was really good at bringing these two teams

Alex Filippenko (2:03:20.280)

together instead of having them duke it out in blows and leaving both of them bleeding

Lex Fridman (2:03:24.280)

and dying.

Alex Filippenko (2:03:25.280)

You know, the National Science Foundation was going to cut the funding from what I understand,

Lex Fridman (2:03:29.680)

you know.

Alex Filippenko (2:03:30.680)

So, so there's human drama involved in this whole thing.

Lex Fridman (2:03:33.880)

And the Olympics, yeah, you know, a runner, a swimmer, a runner, runner, you know, they

Alex Filippenko (2:03:38.960)

slip just at the moment that they were taking off from the first thing and that costs them

Lex Fridman (2:03:43.720)

some fraction of a second and that's it.

Alex Filippenko (2:03:46.400)

They didn't win, you know.

Lex Fridman (2:03:47.560)

And in that case, I mean, the coaches, the families, which I met a lot of Olympic athletes

Lex Fridman (2:03:53.920)

and the coaches and the families of the athletes are really the winners of the medals.

Lex Fridman (2:04:01.280)

But they don't get the medal and it's, you know, credit assignment is a fascinating thing.

Alex Filippenko (2:04:06.240)

I mean, that's the full human story we have.

Lex Fridman (2:04:10.040)

And outside of prizes, it's fascinating.

Alex Filippenko (2:04:13.520)

I mean, just to be in the middle of it for artificial intelligence, there's a field of

Lex Fridman (2:04:18.080)

deep learning.

Alex Filippenko (2:04:19.080)

That's really exciting.

Lex Fridman (2:04:20.080)

And people have been, there's yet another award, the touring awards given for deep learning

Alex Filippenko (2:04:26.320)

to three folks who are very much responsible for the field, but so are a lot of others.

Lex Fridman (2:04:32.560)

Yeah, that's right.

Lex Fridman (2:04:33.960)

And there's a few, there's a, there's a fellow by the name of Schmidt Huber who sort of symbolizes

Lex Fridman (2:04:43.480)

the, the forgotten folks in the deep learning community.

Lex Fridman (2:04:48.880)

But you know, that's, that's the unfortunate sad thing where you remember, remember Isaac

Alex Filippenko (2:04:55.040)

Newton or remember these, these, these special figures and the ones that flew close to them,

Alex Filippenko (2:05:04.080)

we forget.

Lex Fridman (2:05:05.080)

Well, that's right.

Lex Fridman (2:05:06.080)

And you know, often the breakthroughs are made based on the body of knowledge that had

Lex Fridman (2:05:10.220)

been assimilated prior to that.

Lex Fridman (2:05:13.320)

But you know, again, people like to worship heroes.

Alex Filippenko (2:05:15.840)

You mentioned the Oscars earlier and you know, you look at the direct, I mean, well, I mean,

Alex Filippenko (2:05:21.800)

okay, directors and stuff sometimes get awards and stuff, but you know, you look at even

Lex Fridman (2:05:26.520)

something like, I don't know, songwriters, musicians, Elton John or something, right?

Lex Fridman (2:05:30.320)

Bernie Taupin, right?

Alex Filippenko (2:05:32.240)

Wrote many of the words or he's not as well known or the Beatles or something like that.

Alex Filippenko (2:05:39.800)

I was heartbroken to learn that Elvis didn't write most of the songs.

Lex Fridman (2:05:43.400)

Yeah, Elvis.

Alex Filippenko (2:05:44.400)

That's right.

Lex Fridman (2:05:45.400)

There you go.

Lex Fridman (2:05:46.400)

But he was the king, right?

Lex Fridman (2:05:47.400)

And he had such a personality and it was such a performer, right?

Lex Fridman (2:05:50.840)

But it's the unsung heroes in many cases.

Lex Fridman (2:05:53.880)

Yeah.

Lex Fridman (2:05:54.880)

So maybe taking a step back, we talked about the Nobel prize of the accelerating universe,

Lex Fridman (2:06:00.480)

but your work and the ideas around supernova were important in detecting this accelerating

Alex Filippenko (2:06:11.040)

universe.

Lex Fridman (2:06:12.040)

Can we go to the very basics of what is this beautiful, mysterious object of a supernova?

Alex Filippenko (2:06:17.480)

Right.

Lex Fridman (2:06:18.480)

So a supernova is an exploding star.

Alex Filippenko (2:06:21.160)

Most stars die a relatively quiet death, our own sun, well, despite the fact that it'll

Lex Fridman (2:06:25.660)

become a red giant and incinerate earth, it'll do that reasonably slowly.

Lex Fridman (2:06:30.360)

But there's a small minority of stars that end their lives in a Titanic explosion.

Lex Fridman (2:06:35.860)

And that's not only exciting to watch from afar, but it's critical to our existence because

Alex Filippenko (2:06:40.880)

it is in these explosions that the heavy elements synthesize through nuclear reactions during

Alex Filippenko (2:06:46.960)

the normal course of the star's evolution and during the explosion itself, get injected

Alex Filippenko (2:06:52.640)

into the cosmos, making them available as raw material for new stars, planets, and ultimately

Lex Fridman (2:06:59.560)

life.

Lex Fridman (2:07:00.560)

And that's just a great story, the best in some ways.

Lex Fridman (2:07:04.880)

So we like to study these things and our origins, but it turns out these are incredibly useful

Alex Filippenko (2:07:11.040)

beacons as well, because if you know how powerful an exploding star really is by measuring the

Alex Filippenko (2:07:19.640)

apparent brightness at its peak in galaxies whose distances we already know through having

Alex Filippenko (2:07:25.680)

made other measurements, and you can thus calibrate how powerful the thing really is,

Lex Fridman (2:07:32.040)

and then you find ones that are much more distant, then you can use their observed brightness

Alex Filippenko (2:07:38.360)

compared with their true intrinsic power or luminosity to judge their distance and hence

Lex Fridman (2:07:43.780)

the distance of the galaxy in which they're located.

Alex Filippenko (2:07:49.160)

Let me just give this one analogy.

Alex Filippenko (2:07:51.980)

You judge the distance of an oncoming car at night by looking at how bright its headlights

Alex Filippenko (2:07:57.160)

appear to be, and you've calibrated how bright the headlights are of a car that's two or

Alex Filippenko (2:08:02.600)

three meters away of known distance, and you go, oh, that's a faint headlight, and so that's

Alex Filippenko (2:08:07.760)

pretty far away.

Alex Filippenko (2:08:09.120)

You also use the apparent angular separation between the two headlights as a consistency

Alex Filippenko (2:08:14.120)

check in your brain, but that's what your brain is doing.

Lex Fridman (2:08:16.720)

So we can do that for cars, we can do that for stars.

Alex Filippenko (2:08:19.760)

Nice, I like that.

Lex Fridman (2:08:21.720)

But you know, with cars, the headlights are all, there's some variation, but they're somewhat

Alex Filippenko (2:08:28.480)

similar so you can make those kinds of conclusions.

Lex Fridman (2:08:32.480)

How much variation is there between supernova that you can detect them?

Alex Filippenko (2:08:38.880)

Right, so first of all, there are several different ways that stars can explode, and

Alex Filippenko (2:08:42.800)

it depends on their mass and whether they're in a binary system and things like that.

Lex Fridman (2:08:47.540)

And the ones that we used for these cosmological purposes, studying the expansion of the history

Alex Filippenko (2:08:52.840)

of the universe, are the so called type Roman numeral I, lowercase a, type Ia supernovae.

Alex Filippenko (2:09:00.560)

They come from a weird type of a star called a white dwarf.

Lex Fridman (2:09:04.340)

Our own sun will turn into a white dwarf in about seven billion years.

Alex Filippenko (2:09:09.080)

It'll have about half its present mass compressed into a volume just the size of Earth.

Lex Fridman (2:09:14.920)

So that's an inordinate density, okay?

Alex Filippenko (2:09:17.120)

It's incredibly dense.

Lex Fridman (2:09:18.880)

And the matter is what's called by quantum physicists degenerate matter, not because

Alex Filippenko (2:09:23.400)

it's morally reprehensible or anything like that, but this is just the name that quantum

Lex Fridman (2:09:28.400)

physicists give to electrons that are squeezed into a very tight space.

Alex Filippenko (2:09:33.000)

The electrons take on a motion due to Heisenberg's uncertainty principle, and also due to the

Alex Filippenko (2:09:39.240)

Pauli exclusion principle that electrons don't like to be in the same place, they like to

Alex Filippenko (2:09:43.860)

avoid each other.

Lex Fridman (2:09:44.860)

And those two things mean that a lot of electrons are moving very rapidly, which gives the star

Alex Filippenko (2:09:50.280)

an extra pressure far above the thermal pressure associated with just the random motions of

Lex Fridman (2:09:56.040)

particles inside the star.

Lex Fridman (2:09:57.920)

So it's a weird type of star, but normally it wouldn't explode and our sun won't explode,

Alex Filippenko (2:10:04.680)

except that if such a white dwarf is in a pair with another more or less normal star,

Alex Filippenko (2:10:10.240)

it can steal material from that normal star until it gets to an unstable limit, roughly

Lex Fridman (2:10:18.760)

one and a half times the mass of our sun, 1.4 or so.

Alex Filippenko (2:10:22.460)

This is known as the Chandrasekhar limit after Subramanian Chandrasekhar, an Indian astrophysicist

Alex Filippenko (2:10:29.200)

who figured this out when he was about 20 years old on a voyage from India to England

Alex Filippenko (2:10:34.960)

where he was to be educated.

Lex Fridman (2:10:37.000)

And then he did this and then 50 years later he won the Nobel Prize in physics in 1984

Alex Filippenko (2:10:42.520)

largely for this work that he did as a youngster who was on his way to be educated.

Lex Fridman (2:10:48.600)

And his advisor, the great Arthur Eddington in England, who had done a lot of great things

Lex Fridman (2:10:54.440)

and was a great astrophysicist, nevertheless, he too was human and had his faults.

Alex Filippenko (2:10:59.640)

He ridiculed Chandra's scientific work at a conference in England and most of us, if

Alex Filippenko (2:11:07.400)

we had been Chandra, would have just given up astrophysics at that time when the great

Lex Fridman (2:11:12.760)

Arthur Eddington ridicules our work.

Alex Filippenko (2:11:16.880)

That's another inspirational story for the youngster.

Lex Fridman (2:11:19.960)

Just keep going.

Lex Fridman (2:11:20.960)

But anyway, no matter what your advisor says or don't always pay attention to your advisor.

Lex Fridman (2:11:28.960)

Don't lose hope if you really think you're onto something.

Alex Filippenko (2:11:32.520)

That doesn't mean never listen to your advisor.

Lex Fridman (2:11:34.360)

They may have sage advice as well.

Lex Fridman (2:11:36.720)

But anyway, when a white dwarf grows to a certain mass, it becomes unstable.

Lex Fridman (2:11:43.540)

And one of the ways it can end its life is to go through a thermonuclear runaway.

Lex Fridman (2:11:48.960)

So basically, the carbon nuclei inside the white dwarf start fusing together to form

Lex Fridman (2:11:54.960)

heavier nuclei.

Lex Fridman (2:11:56.880)

And the energy that those fusion reactions emit doesn't go into being dissipated out

Alex Filippenko (2:12:06.800)

of the star or expanding it the way if you take a blowtorch to the middle of the Sun,

Alex Filippenko (2:12:14.120)

you heat up its gases, the gases would expand and cool.

Lex Fridman (2:12:17.640)

But this degenerate star can't expand and cool.

Lex Fridman (2:12:21.240)

And so the energy pumped in through these fusion reactions goes into making the nuclei

Lex Fridman (2:12:27.200)

move faster.

Lex Fridman (2:12:28.560)

And that gets more of them sufficiently close together that they can undergo nuclear fusion,

Lex Fridman (2:12:33.880)

thereby releasing more energy that goes into speeding up more nuclei.

Lex Fridman (2:12:38.880)

And thus you have a runaway, a bomb, an uncontrolled fusion reactor instead of the controlled fusion,

Lex Fridman (2:12:46.440)

which is what our Sun does.

Alex Filippenko (2:12:48.360)

Our Sun is a marvelous controlled fusion reactor.

Lex Fridman (2:12:51.420)

This is what we need here on Earth, fusion energy to solve our energy crisis, right?

Lex Fridman (2:12:56.280)

But the Sun holds the stuff in through gravity and you need a big mass to do that.

Lex Fridman (2:13:01.100)

So this uncontrolled fusion reaction blows up a star that's pretty much the same in

Alex Filippenko (2:13:07.600)

all cases.

Lex Fridman (2:13:09.640)

And you measure it to be almost the same in all cases.

Lex Fridman (2:13:13.000)

But the devil is in the details, and in fact, we observe them to not be all the same.

Lex Fridman (2:13:18.940)

And theoretically, they might not be all the same because the rate of the fusion reactions

Alex Filippenko (2:13:23.360)

might depend on the amount of trace heavier elements in the white dwarf.

Lex Fridman (2:13:28.600)

And that could depend on how old it is, whether it was born billions of years ago when there

Alex Filippenko (2:13:33.440)

weren't many heavier elements or whether it's a relatively young white dwarf and all

Lex Fridman (2:13:38.300)

kinds of other things.

Lex Fridman (2:13:40.080)

And part of my work was to show that indeed, not all the Type Ia's are the same.

Lex Fridman (2:13:44.940)

You have to be careful when you use them.

Alex Filippenko (2:13:47.520)

You have to calibrate them.

Alex Filippenko (2:13:49.160)

They're not standard candles the way it just, if all headlights or all candles were the

Alex Filippenko (2:13:55.460)

same lumens or whatever, you'd say they're standard and then it would be relative.

Lex Fridman (2:13:59.900)

Standard candles is an awesome term, okay.

Alex Filippenko (2:14:01.940)

Standard candles is what astronomers like to say, but I don't like that term because

Lex Fridman (2:14:05.700)

there aren't any standard candles, but there are standardizable candles.

Lex Fridman (2:14:10.240)

And by looking at these type Ia's, you look at enough of them in nearby galaxies whose

Lex Fridman (2:14:17.800)

distances you know independently.

Lex Fridman (2:14:20.640)

And what you can tell is that, you know, this is something that a colleague of mine, Mark

Alex Filippenko (2:14:25.220)

Phillips did who was on Schmidt's team and arguably was one of the people who deserved

Alex Filippenko (2:14:30.560)

the Nobel Prize.

Alex Filippenko (2:14:31.560)

He showed that the intrinsically more powerful Type Ia's decline in brightness, and it turns

Alex Filippenko (2:14:39.720)

out rise in brightness as well, more slowly than the less luminous Ia's.

Lex Fridman (2:14:45.080)

And so if you calibrate this by measuring a whole bunch of nearby ones and then you

Alex Filippenko (2:14:50.260)

look at a distant one, instead of saying, well, it's a 100 watt Type Ia supernova, they're

Alex Filippenko (2:14:56.120)

much more powerful than that by the way, plus or minus 50, you can say, no, it's a hundred

Lex Fridman (2:15:01.440)

and 12 plus or minus 15, or it's 84 plus or minus 17.

Alex Filippenko (2:15:08.940)

It tells you where it is in the power scale and it greatly decreases the uncertainties.

Lex Fridman (2:15:15.240)

And that's what makes these things cosmologically useful.

Alex Filippenko (2:15:18.720)

I showed that if you spread the light out into a spectrum, you can tell spectroscopically

Alex Filippenko (2:15:24.080)

that these things are different as well.

Lex Fridman (2:15:26.560)

And in 1991, I happened to study two of the extreme peculiar ones, the low luminosity

Alex Filippenko (2:15:33.580)

ones and the high luminosity ones, 1991BG and 1991T.

Lex Fridman (2:15:40.560)

This showed that not all the Ia's are the same.

Lex Fridman (2:15:43.520)

And indeed, at the time of 1991, I was a little bit skeptical that we could use Type Ia's

Lex Fridman (2:15:50.520)

because of this diversity that I was observing.

Lex Fridman (2:15:53.120)

But in 1993, Mark Phillips wrote a paper that showed this correlation between the light

Lex Fridman (2:16:00.080)

curve, the brightness versus time and the peak luminosity.

Alex Filippenko (2:16:03.760)

Which gives you enough information to calibrate.

Lex Fridman (2:16:05.920)

Then they become calibratable and that was a game changer.

Lex Fridman (2:16:08.280)

How many Type Ia's are out there to use for data?

Alex Filippenko (2:16:12.320)

Now there are thousands of them, but at the time, the high Z team had 16 and the supernova

Alex Filippenko (2:16:19.840)

cosmology project had 40.

Lex Fridman (2:16:22.640)

But the 16 were better measured than the 40.

Lex Fridman (2:16:25.840)

And so our statistical uncertainties were comparable if you look at the two papers that

Lex Fridman (2:16:31.080)

were published.

Lex Fridman (2:16:32.080)

How does that make you feel that there's these gigantic explosions just sprinkled out there?

Alex Filippenko (2:16:38.760)

Well, I certainly don't want one to be very nearby and it would have to be within something

Alex Filippenko (2:16:43.380)

like 10 light years to be an existential threat.

Lex Fridman (2:16:46.400)

So they can happen in our galaxy?

Alex Filippenko (2:16:48.960)

Oh yeah, yeah.

Lex Fridman (2:16:49.960)

So they would be okay?

Alex Filippenko (2:16:52.480)

In most cases we'd be okay because our galaxy is 100,000 light years across.

Lex Fridman (2:16:57.160)

And you'd need one of these things to be within about 10 light years to be an existential

Alex Filippenko (2:17:01.360)

threat.

Lex Fridman (2:17:02.360)

And it gives birth to a bunch of other stars, I guess?

Alex Filippenko (2:17:07.040)

Yeah, it gives birth to expanding gases that are chemically enriched and those expanding

Alex Filippenko (2:17:11.060)

gases mixed with other chemically enriched expanding gases or primordial clouds of hydrogen

Lex Fridman (2:17:17.520)

and helium.

Lex Fridman (2:17:18.520)

I mean, this is in a sense the greatest story ever told, right?

Alex Filippenko (2:17:24.800)

I teach this introductory astronomy course at Berkeley and I tell them there's only five

Alex Filippenko (2:17:29.840)

or six things that I want them to really understand and remember and I'm going to come to their

Alex Filippenko (2:17:34.660)

deathbed and I'm going to ask them about this and if they get it wrong, I will retroactively

Lex Fridman (2:17:39.020)

fail and their whole career will have been shot.

Alex Filippenko (2:17:42.240)

That's a student's worst nightmare.

Alex Filippenko (2:17:43.240)

If they don't know and observe a total solar eclipse and yet they had the opportunity to

Alex Filippenko (2:17:46.680)

do so, I will retroactively fail them.

Lex Fridman (2:17:49.080)

But one of them is, where did we come from?

Lex Fridman (2:17:51.800)

Where did the elements in our DNA come from?

Alex Filippenko (2:17:54.560)

The carbon in our cells, the oxygen that we breathe, the calcium in our bones, the iron

Alex Filippenko (2:17:59.480)

in our red blood cells.

Alex Filippenko (2:18:01.780)

Those elements, the phosphorus in our DNA, they all came from stars, from nuclear reactions

Alex Filippenko (2:18:07.680)

in stars and they were ejected into the cosmos and in some cases, like iron, made during

Alex Filippenko (2:18:15.280)

the explosions and those gases drifted out, mixed with other clouds, made a new star or

Alex Filippenko (2:18:22.200)

a star cluster, some of whose members then evolved and exploded, thus enriching the gases

Alex Filippenko (2:18:30.240)

in the galaxy progressively more with time until finally, four and a half billion years

Alex Filippenko (2:18:35.120)

ago from one of these chemically enriched clouds, our solar system formed with a rocky

Alex Filippenko (2:18:41.560)

earthlike planet and somewhere, somehow, these self replicating, evolving molecules, bacteria

Alex Filippenko (2:18:49.440)

formed and evolved through paramecia and amoebas and slugs and apes and us.

Lex Fridman (2:18:58.940)

And here we are, sentient beings that can ask these questions about our very origins

Lex Fridman (2:19:05.040)

and with our intellect and with the machines we make, come to a reasonable understanding

Lex Fridman (2:19:12.540)

of our origins.

Lex Fridman (2:19:15.080)

What a beautiful story.

Alex Filippenko (2:19:16.640)

I mean, if that does not put you at least in awe, if not in love with science and its

Lex Fridman (2:19:24.280)

power of deduction, I don't know what will, right?

Lex Fridman (2:19:30.100)

It's one of the greatest stories, if not the greatest story.

Alex Filippenko (2:19:33.040)

Obviously, that's personality dependent and all that, it's a subjective opinion, but it's

Lex Fridman (2:19:38.040)

perhaps the greatest story ever told.

Alex Filippenko (2:19:41.280)

I mean, you could link it to the Big Bang and go even farther, right, to make an even

Alex Filippenko (2:19:45.040)

more complete story, but as a subset, that's even in some ways a greater story than even

Alex Filippenko (2:19:51.600)

the existence of the universe in some ways, because you could just imagine some really

Lex Fridman (2:19:56.280)

boring universe that never leads to sentient creatures such as ourselves.

Lex Fridman (2:20:01.300)

And is a supernova usually the introduction to that story?

Lex Fridman (2:20:06.880)

So are they usually the thing that launches the, is there other engines of creation?

Alex Filippenko (2:20:12.200)

Well, the supernova is the one, I mean, I touch upon the subject earlier in my course,

Alex Filippenko (2:20:18.360)

in fact, right about now in my lectures, because I talk about how our sun right now is fusing

Alex Filippenko (2:20:22.880)

hydrogen to form helium nuclei and later it'll form carbon and oxygen nuclei, but that's

Alex Filippenko (2:20:29.440)

where the process will stop for our sun, it's not massive enough, some stars that are more

Alex Filippenko (2:20:34.160)

massive can go somewhat beyond that.

Lex Fridman (2:20:37.060)

So that's the beginning of this idea of the birth of the heavy elements, since they couldn't

Alex Filippenko (2:20:42.760)

have been born at the time of the Big Bang, conditions of temperature and pressure weren't

Lex Fridman (2:20:47.480)

sufficient to make any significant quantities of the heavier elements.

Lex Fridman (2:20:51.960)

And so that's the beginning, but then you need some of these stars to explode, right?

Alex Filippenko (2:20:57.480)

Because if those heavy elements remained forever trapped in the cores of stars, then they would

Alex Filippenko (2:21:03.020)

not be available for the production of new stars, planets, and ultimately life.

Lex Fridman (2:21:08.920)

So indeed the supernova, my main area of interest, plays a leading role in this whole story.

Alex Filippenko (2:21:17.400)

I saw that you got a chance to call Richard Feynman a mentor of yours when you were at

Lex Fridman (2:21:22.520)

Caltech.

Alex Filippenko (2:21:23.520)

Yeah.

Lex Fridman (2:21:24.520)

Do you have any fond memories of Feynman, any lessons that stick with you?

Alex Filippenko (2:21:28.880)

Oh yeah, he was quite a character and one of the deepest thinkers of all time probably,

Lex Fridman (2:21:36.040)

and at least in my life, the physicist who had the single most intuitive understanding

Alex Filippenko (2:21:42.840)

of how nature works of anyone I've met.

Alex Filippenko (2:21:48.960)

I learned a number of things from him, he was not my thesis advisor, I worked with Wallace

Alex Filippenko (2:21:53.240)

Sargent at Caltech on what are called active galaxies, big black holes in the centers of

Alex Filippenko (2:21:58.140)

galaxies that are accreting or swallowing material, a little bit like the stuff of this

Alex Filippenko (2:22:03.180)

year's Nobel Prize in Physics 2020.

Lex Fridman (2:22:06.860)

But Feynman I had for two courses, one was general theory of relativity at the graduate

Alex Filippenko (2:22:12.180)

level and one was applications of quantum physics to all kinds of interesting things.

Lex Fridman (2:22:18.100)

And he had this very intuitive way of looking at things that he tried to bring to his students

Lex Fridman (2:22:28.880)

and he felt that if you can't explain something in a reasonably simple way to a non scientist

Alex Filippenko (2:22:38.200)

or at least someone who is versed a little bit with science but is not a professional

Alex Filippenko (2:22:43.680)

scientist then you probably don't understand it very well yourself very thoroughly.

Lex Fridman (2:22:49.420)

So that in me made a desire to be able to explain science to the general public and

Alex Filippenko (2:22:58.400)

I've often found that in explaining things, yeah, there's a certain part that I didn't

Alex Filippenko (2:23:02.580)

really understand myself, that's one reason I like to teach the introductory courses to

Alex Filippenko (2:23:06.760)

the lay public is that I sometimes find that my explanations are lacking in my own mind.

Lex Fridman (2:23:12.700)

So he did that for me.

Alex Filippenko (2:23:14.180)

Is there a, if I could just pause for a second, you said he had one of the most intuitive

Lex Fridman (2:23:18.220)

understanding of nature.

Lex Fridman (2:23:20.820)

What if you could break apart what intuitive means, like is that on the philosophical level?

Lex Fridman (2:23:26.940)

No, sort of physical.

Lex Fridman (2:23:28.580)

How do you draw a mental picture or a picture on paper of what's going on?

Lex Fridman (2:23:33.660)

And he's perhaps most famous in this regard for his Feynman diagrams, which in what's

Alex Filippenko (2:23:39.000)

called quantum electrodynamics, a quantum field theory of electricity and magnetism.

Lex Fridman (2:23:44.140)

What you have are actually an exchange of photons between charged particles and they

Alex Filippenko (2:23:48.800)

might even be virtual photons if the particles are at rest relative to one another.

Lex Fridman (2:23:55.500)

And there are ways of doing calculations that are brute force that take pages on pages and

Alex Filippenko (2:24:00.140)

pages of calculations.

Lex Fridman (2:24:02.340)

And Julian Schwinger developed some of the mathematics for that and won the Nobel prize

Alex Filippenko (2:24:06.780)

for it.

Lex Fridman (2:24:07.780)

But Feynman had these diagrams that he made and he had a set of rules of what to do at

Alex Filippenko (2:24:12.500)

the vertex.

Alex Filippenko (2:24:13.500)

You'd have two particles coming together and then a particle going out and then two particles

Alex Filippenko (2:24:17.020)

coming out again.

Lex Fridman (2:24:18.020)

And he'd have these rules associated when there were vertices and when there were particles

Alex Filippenko (2:24:22.100)

splitting off from one another and all that.

Lex Fridman (2:24:24.380)

And it looked a little bit like a bunch of a hodgepodge at first.

Lex Fridman (2:24:27.920)

But to those who learned the rules and understood them, they saw that you could do these complex

Lex Fridman (2:24:34.220)

calculations in a much simpler way.

Lex Fridman (2:24:37.340)

And indeed, in some ways, Freeman Dyson had an even better knack for explaining really

Lex Fridman (2:24:42.700)

what quantum electrodynamics actually was.

Lex Fridman (2:24:46.180)

But I didn't know Freeman Dyson.

Lex Fridman (2:24:48.300)

I knew Feynman.

Alex Filippenko (2:24:49.300)

Maybe he did have a more intuitive view of the world than Feynman did.

Lex Fridman (2:24:52.920)

But of the people I knew, Feynman was the most intuitive, most sort of, is there a picture?

Lex Fridman (2:24:58.860)

Is there a simple way you can understand this?

Alex Filippenko (2:25:01.980)

In the path that a particle follows even, you can get the classical path, at least for

Alex Filippenko (2:25:10.580)

a baseball or something like that, by using quantum physics if you want.

Lex Fridman (2:25:14.700)

But in a sense, the baseball sniffs out all possible paths.

Alex Filippenko (2:25:19.740)

It goes out to the Andromeda galaxy and then goes to the batter.

Lex Fridman (2:25:23.060)

But the probability of doing that is very, very small because tiny little paths next

Alex Filippenko (2:25:28.420)

door to any given path cancel out that path.

Lex Fridman (2:25:32.500)

And the ones that all add together, they're the ones that are more likely to be followed.

Lex Fridman (2:25:38.940)

And this actually ties in with Fermat's principle of least action and there are ideas in optics

Alex Filippenko (2:25:45.740)

that go into this as well and just sort of beautifully brings everything together.

Lex Fridman (2:25:50.620)

But the particle sniffs out all possible paths.

Lex Fridman (2:25:54.060)

What a crazy idea.

Lex Fridman (2:25:55.060)

But if you do the mathematics associated with that, it ends up being actually useful, a

Lex Fridman (2:26:00.980)

useful way of looking at the world.

Lex Fridman (2:26:02.540)

So you're also, I mean, you're widely acknowledged as, I mean, outside of your science work as

Lex Fridman (2:26:07.780)

being one of the greatest educators in the world.

Lex Fridman (2:26:12.500)

And Feynman is famous for being that.

Lex Fridman (2:26:16.140)

Is there something about being a teacher that you...

Alex Filippenko (2:26:19.220)

Well, it's very, very rewarding when you have students who are really into it.

Alex Filippenko (2:26:23.260)

You know, going back to Feynman, at Caltech, I was taking these graduate courses and there

Alex Filippenko (2:26:29.220)

were two of us, myself and Jeff Richmond, who's now a professor of physics at University

Lex Fridman (2:26:34.140)

of California, Santa Barbara, who asked lots of questions.

Lex Fridman (2:26:38.100)

And a lot of the Caltech students are nervous about asking questions.

Lex Fridman (2:26:42.780)

They want to save face.

Alex Filippenko (2:26:43.980)

They seem to think that if they ask a question, their peers might think it's a stupid question.

Lex Fridman (2:26:49.100)

Well, I didn't really care what people thought and Jeff Richmond didn't either.

Alex Filippenko (2:26:52.620)

We asked all these questions and in fact, in many cases, they were quite good questions

Lex Fridman (2:26:57.300)

and Feynman said, well, the rest of you should be having questions like this.

Lex Fridman (2:27:00.660)

And I remember one time in particular when he said to the rest of the class, why is it

Lex Fridman (2:27:07.260)

always these two?

Lex Fridman (2:27:09.620)

Aren't the rest of you curious about what I'm saying?

Lex Fridman (2:27:12.020)

Do you really understand it all that well?

Lex Fridman (2:27:14.580)

If so, why aren't you asking the next most logical question?

Lex Fridman (2:27:17.980)

No, you guys are too scared to ask these questions that these two are asking.

Lex Fridman (2:27:23.300)

So he actually invited us to lunch a couple of times where just the three of us sat and

Lex Fridman (2:27:28.420)

had lunch with one of the greatest thinkers of 20th century physics.

Lex Fridman (2:27:33.540)

And so, yeah, he rubbed off on me and, you know, you encourage questions as well, encourage

Alex Filippenko (2:27:38.220)

questions, you know, and yeah, you know, definitely, I mean, you know, I encourage questions.

Alex Filippenko (2:27:45.140)

I like it when students ask questions.

Lex Fridman (2:27:46.980)

I tell them that they shouldn't feel shy about asking a question.

Alex Filippenko (2:27:51.340)

Probably half the students in the class would have that same question if they even understood

Lex Fridman (2:27:55.580)

the material enough to ask that question.

Alex Filippenko (2:27:58.460)

Yeah.

Lex Fridman (2:27:59.460)

Curiosity is the first step of seeing the beauty of something.

Lex Fridman (2:28:04.580)

So yeah, and the question is the ultimate form of curiosity.

Lex Fridman (2:28:10.180)

Let me ask, what is the meaning of life?

Alex Filippenko (2:28:14.220)

The meaning of life, you know, from a cosmologist's perspective or from a human perspective, personal,

Lex Fridman (2:28:19.900)

you know, life is what you make of it, really, right?

Alex Filippenko (2:28:23.300)

It's each of us has to have our own meaning and it doesn't have to be.

Alex Filippenko (2:28:31.100)

Well, I think that in many cases, meaning is to some degree associated with goals.

Alex Filippenko (2:28:36.220)

You set some goals or expectations for yourself, things you want to accomplish, things you

Alex Filippenko (2:28:41.380)

want to do, things you want to experience, and to the degree that you experience those

Lex Fridman (2:28:47.100)

and do those things, it can give you meaning.

Alex Filippenko (2:28:50.740)

You don't have to change the world the way Newton or Michelangelo or da Vinci did.

Alex Filippenko (2:28:56.540)

I mean, people often say, you changed the world, but look, come on, there's seven and

Lex Fridman (2:29:00.180)

a half, close to eight billion of us now.

Alex Filippenko (2:29:02.780)

Most of us are not going to change the world and does that mean that most of us are leading

Lex Fridman (2:29:06.300)

meaningful lives?

Alex Filippenko (2:29:07.900)

No, it just has to be something that gives you meaning, that gives you satisfaction,

Lex Fridman (2:29:15.220)

that gives you a good feeling about what you did.

Lex Fridman (2:29:17.860)

And often, based on human nature, which can be very good and also very bad, but often

Alex Filippenko (2:29:24.480)

it's the things that help others that give us meaning and a feeling of satisfaction.

Alex Filippenko (2:29:31.800)

You taught someone to read, you cared for someone who was terminally ill, you brought

Alex Filippenko (2:29:37.100)

up a nice family, you brought up your kids, you did a good job, you put your heart and

Alex Filippenko (2:29:43.220)

soul into it, you read a lot of books if that's what you wanted to do, had a lot of perspectives

Lex Fridman (2:29:49.780)

on life, you traveled the world if that's what you wanted to do.

Lex Fridman (2:29:54.840)

But if some of these things are not within reach, you're in a socioeconomic position

Lex Fridman (2:30:00.260)

where you can't travel the world or whatever, you find other forms of meaning.

Alex Filippenko (2:30:06.500)

It doesn't have to be some profound, I'm going to change the world, I'm going to be

Lex Fridman (2:30:13.660)

the one who everyone remembers type thing, right?

Alex Filippenko (2:30:17.900)

In the context of the greatest story ever told, like the fact that we came from stars

Lex Fridman (2:30:26.100)

and now we're two apes asking about the meaning of life, how does that fit together?

Lex Fridman (2:30:31.500)

How does that make any sense?

Alex Filippenko (2:30:34.780)

It does, it does, and this is sort of what I was referring to, that it's a beautiful

Lex Fridman (2:30:39.700)

universe that allows us to come into creation, right?

Alex Filippenko (2:30:46.820)

It's a way that the universe found of knowing, of understanding itself, because I don't

Alex Filippenko (2:30:52.780)

think that inanimate rocks and stars and black holes and things have any real capability

Alex Filippenko (2:31:00.420)

of abstract thoughts and of learning about the rest of the universe or even their origins.

Alex Filippenko (2:31:08.260)

I mean, they're just a pile of atoms that has no conscience, has no ability to think,

Lex Fridman (2:31:16.060)

has no ability to explore, and we do.

Lex Fridman (2:31:20.620)

And I'm not saying we're the epitome of all life forever, but at least for life on Earth

Lex Fridman (2:31:27.940)

so far the evidence suggests that we are the epitome in terms of the richness of our thoughts,

Alex Filippenko (2:31:36.060)

the degree to which we can explore the universe, do experiments, build machines, understand

Lex Fridman (2:31:42.180)

our origins.

Lex Fridman (2:31:43.180)

And I just hope that we use science for good, not evil, and that we don't end up destroying

Lex Fridman (2:31:50.300)

ourselves.

Alex Filippenko (2:31:51.300)

I mean, the whales and dolphins are plenty intelligent.

Alex Filippenko (2:31:54.320)

They don't ask abstract questions, they don't read books, but on the other hand, they're

Alex Filippenko (2:31:59.180)

not in any danger of destroying themselves and everything else as well.

Lex Fridman (2:32:03.360)

And so maybe that's a better form of intelligence, but at least in terms of our ability to explore

Lex Fridman (2:32:10.100)

and make use of our minds, I mean, to me, it's this.

Lex Fridman (2:32:16.300)

It's this that gives me the potential for meaning, right?

Alex Filippenko (2:32:21.740)

The fact that I can understand and explore.

Alex Filippenko (2:32:24.520)

It's kind of fascinating to think that the universe created us and eventually we've built

Alex Filippenko (2:32:31.560)

telescopes to look back at it, to look back at its origins and to wonder how the heck

Lex Fridman (2:32:38.500)

the thing works.

Alex Filippenko (2:32:39.500)

It's magnificent.

Lex Fridman (2:32:40.500)

It needn't have been that way, right?

Lex Fridman (2:32:44.260)

And this is one of the, you know, the multiverse sort of things.

Alex Filippenko (2:32:48.480)

You know, you can alter the laws of physics or even the constants of nature, seemingly

Alex Filippenko (2:32:53.460)

inconsequential things like the mass ratio of the proton and the neutron, you know, wake

Lex Fridman (2:32:58.020)

me up when it's over, right?

Lex Fridman (2:32:59.720)

What could be more boring?

Lex Fridman (2:33:00.720)

But it turns out you play with things a little bit like the ratio of the mass of the neutron

Alex Filippenko (2:33:04.900)

to the proton and you generally get boring universes, only hydrogen or only helium or

Lex Fridman (2:33:11.700)

only iron.

Alex Filippenko (2:33:12.700)

You can't even get the rich periodic table, let alone bacteria, paramecia, slugs and humans,

Lex Fridman (2:33:19.020)

okay?

Alex Filippenko (2:33:20.020)

I'm not even anthropocentrizing this to the degree that I could.

Alex Filippenko (2:33:25.440)

Even a rich periodic table wouldn't be possible if certain constants weren't this way, but

Alex Filippenko (2:33:33.060)

they are.

Lex Fridman (2:33:34.060)

And that to me leads to the idea of a multiverse that, you know, the dice were thrown many,

Alex Filippenko (2:33:39.420)

many times and there's this cosmic archipelago where most of the universes are boring and

Lex Fridman (2:33:44.020)

some might be more interesting.

Lex Fridman (2:33:45.700)

But we are in the rare breed that's really quite darn interesting.

Lex Fridman (2:33:51.700)

And if there were only one and maybe there is only one, well then that's truly amazing.

Alex Filippenko (2:33:57.060)

We're lucky.

Lex Fridman (2:33:58.060)

We're lucky.

Lex Fridman (2:33:59.060)

But I actually think there are lots and lots, just like there are lots of planets.

Lex Fridman (2:34:03.020)

Earth isn't special for any particular reason.

Alex Filippenko (2:34:05.860)

There are lots of planets in our solar system and especially around other stars.

Lex Fridman (2:34:09.820)

And occasionally there are going to be ones that are conducive to the development of complexity

Alex Filippenko (2:34:14.660)

culminating in life as we know it.

Lex Fridman (2:34:17.100)

And that's a beautiful story.

Alex Filippenko (2:34:18.820)

I don't think there's a better way to end it.

Lex Fridman (2:34:21.660)

Alex, it's a huge honor.

Alex Filippenko (2:34:23.100)

One of my favorite conversations I've had in this podcast.

Lex Fridman (2:34:25.300)

Well, thank you so much for talking to us.

Alex Filippenko (2:34:27.580)

For the honor of having been asked to do this.

Alex Filippenko (2:34:31.900)

Thanks for listening to this conversation with Alex Filipenko, and thank you to our

Alex Filippenko (2:34:36.420)

sponsors.

Alex Filippenko (2:34:37.420)

Neuro, the maker of functional sugar free gum and mints that I use to give my brain

Alex Filippenko (2:34:41.940)

a quick caffeine boost.

Lex Fridman (2:34:44.040)

BetterHelp, online therapy with a licensed professional.

Alex Filippenko (2:34:47.580)

Masterclass, online courses that I enjoy from some of the most amazing humans in history.

Lex Fridman (2:34:54.300)

And CashApp, the app I use to send money to friends.

Alex Filippenko (2:34:58.460)

Please check out these sponsors in the description to get a discount and support this podcast.

Alex Filippenko (2:35:03.180)

If you enjoy this thing, subscribe on YouTube, review it with 5 Stars and Apple Podcast,

Alex Filippenko (2:35:09.100)

follow on Spotify, support on Patreon, or connect with me on Twitter at Lex Friedman.

Lex Fridman (2:35:15.540)

And now, let me leave you with some words from Carl Sagan.

Alex Filippenko (2:35:19.580)

The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in

Lex Fridman (2:35:26.880)

our apple pies, were made in the interiors of collapsing stars.

Alex Filippenko (2:35:32.340)

We are made of star stuff.

Lex Fridman (2:35:36.060)

Thank you for listening, and hope to see you next time.

Alex Filippenko (30:02.280)

Tambora and other ones, you look at the record and you see rather large dips in temperature

Lex Fridman (30:08.840)

associated with massive volcanic eruptions.

Alex Filippenko (30:12.120)

Well these super volcanoes, one of which by the way exists under Yellowstone in the central

Alex Filippenko (30:18.000)

US, it's not just one or two states, it's a gigantic region and there's controversy

Alex Filippenko (30:25.400)

as to whether it's likely to blow anytime in the next 100,000 years or so.

Lex Fridman (30:30.880)

But that would be perhaps not a mass extinction or perhaps not a complete existential threat

Alex Filippenko (30:37.080)

because you have to get rid of the very last humans for that, but at least getting rid

Lex Fridman (30:43.220)

of killing off so many humans, truly billions and billions of humans.

Alex Filippenko (30:49.460)

There have been ones tens of thousands of years ago including this one, Toba I think

Alex Filippenko (30:55.880)

it's called, where it's estimated that the human population was down to 10,000 or 5,000

Alex Filippenko (31:02.880)

individuals, something like that.

Alex Filippenko (31:05.040)

If you have a 15 degree drop in temperature over quite a short time, it's not clear that

Alex Filippenko (31:11.320)

even with today's advanced technology, we would be able to adequately respond at least

Lex Fridman (31:15.960)

for the vast majority of people.

Alex Filippenko (31:18.260)

Maybe some would be in these underground caves where you'd keep the president and a bunch

Alex Filippenko (31:21.840)

of other important people, but the typical person is not going to be protected when all

Alex Filippenko (31:28.080)

of agriculture is cut off.

Lex Fridman (31:32.120)

It could be hundreds of millions or billions of people starving to death.

Alex Filippenko (31:36.960)

Exactly.

Lex Fridman (31:37.960)

That's right.

Alex Filippenko (31:38.960)

They don't all die immediately, but they use up their supplies or again, this electrical

Lex Fridman (31:44.080)

grid.

Alex Filippenko (31:45.080)

First of toilet paper.

Lex Fridman (31:46.080)

Dash that toilet paper or the electrical grid.

Alex Filippenko (31:50.840)

Imagine North America without power for a year.

Lex Fridman (31:55.240)

We've become so dependent, we're no longer the cave people.

Alex Filippenko (31:58.420)

They would do just fine.

Lex Fridman (32:00.160)

What do they care about the electrical grid?

Lex Fridman (32:02.480)

What do they care about agriculture, their hunters and gatherers?

Lex Fridman (32:06.040)

But we now have become so used to our way of life that the only real survivors would

Alex Filippenko (32:12.240)

be those rugged individualists who live somewhere out in the forest or in a cave somewhere,

Lex Fridman (32:17.520)

completely independent of anyone else.

Alex Filippenko (32:20.160)

Yeah.

Alex Filippenko (32:21.160)

Recently I recommended, it's totally new to me, this kind of survivalist folks, but there's

Alex Filippenko (32:26.080)

a few shows.

Alex Filippenko (32:27.500)

There's a lot of shows of those, but I saw one on Netflix and I started watching them

Lex Fridman (32:32.720)

and they make a lot of sense.

Alex Filippenko (32:37.040)

They reveal to you how dependent we are on all aspects of this beautiful systems we human

Alex Filippenko (32:43.260)

have built and how fragile they are.

Lex Fridman (32:47.200)

Incredibly fragile.

Lex Fridman (32:48.380)

And this whole conversation is making me realize how lucky we are.

Alex Filippenko (32:53.040)

Oh, we're incredibly lucky, but we've set ourselves up to be very, very fragile and

Alex Filippenko (32:59.240)

we are intrinsically complex biological creatures that except for the fact that we have brains

Lex Fridman (33:05.720)

and minds with which we can try to prevent some of these things or respond to them.

Alex Filippenko (33:11.800)

We as a living organism require quite a narrow set of conditions in order to survive.

Lex Fridman (33:18.700)

We're not cockroaches.

Alex Filippenko (33:20.240)

We're not going to survive a nuclear war.

Lex Fridman (33:23.120)

So we're kind of this beautiful dance between, we've been talking about astronomy, that astronomy,

Alex Filippenko (33:31.360)

the stars like inspires everybody and at the same time, there's this pragmatic aspect that

Lex Fridman (33:37.840)

we're talking about.

Lex Fridman (33:39.140)

And so I see space exploration as the same kind of way that it's reaching out to other

Lex Fridman (33:44.880)

planets, reaching out to the stars, this really beautiful idea.

Lex Fridman (33:48.760)

But if you listen to somebody like Elon Musk, he talks about space exploration as very pragmatic.

Alex Filippenko (33:56.800)

Like we have to be, he has this ridiculous way of sounding like an engineer about it,

Alex Filippenko (34:03.880)

which is like, it's obvious we need to become a multi planetary species if we were to survive

Lex Fridman (34:09.440)

long term.

Lex Fridman (34:10.540)

So maybe both philosophically in terms of beauty and in terms of practical, what's your

Alex Filippenko (34:18.080)

thoughts on space exploration, on the challenges of it, on how much we should be investing

Alex Filippenko (34:24.260)

in it and on a personal level, like how excited you are by the possibility of going to Mars,

Lex Fridman (34:30.760)

colonizing Mars and maybe going outside the solar system.

Alex Filippenko (34:34.600)

Yeah.

Lex Fridman (34:35.600)

You know, great question.

Alex Filippenko (34:37.920)

There's a lot to unpack there of course.

Lex Fridman (34:41.280)

Humans are by their very nature explorers, pioneers.

Alex Filippenko (34:44.460)

They want to go out, climb the next mountain, see what's behind it, explore the option depths,

Lex Fridman (34:51.440)

explore space.

Alex Filippenko (34:52.460)

This is our destiny to go out there.

Lex Fridman (34:55.360)

And of course, from a pragmatic perspective, yes, we need to plant our seeds elsewhere

Alex Filippenko (35:02.420)

really because things could go wrong here on Earth.

Lex Fridman (35:05.480)

Now some people say that's an excuse to not take care of our planet.

Alex Filippenko (35:11.080)

Well, we say we're elsewhere and so we don't have to take good care of our planet.

Lex Fridman (35:14.280)

No, we should take the best possible care of our planet.

Alex Filippenko (35:18.160)

We should be cognizant of the potential impact of what we're doing.

Lex Fridman (35:22.120)

Nevertheless, it's prudent to have us be elsewhere as well.

Lex Fridman (35:26.880)

So in that regard, I actually agree with Elon.

Lex Fridman (35:31.200)

It'd be good to be on Mars.

Alex Filippenko (35:32.420)

That would be yet another place for us from which to explore further.

Lex Fridman (35:38.240)

Would that be a good next step?

Alex Filippenko (35:39.640)

Well, it's a good next step.

Lex Fridman (35:42.160)

I happen to disagree with him as to how quickly it will happen.

Alex Filippenko (35:46.360)

I think he's very optimistic.

Alex Filippenko (35:48.120)

Now you need visionary people like Elon to get people going and to inspire them.

Alex Filippenko (35:52.760)

I mean, look at the success he's had with multiple companies.

Lex Fridman (35:57.120)

So maybe he gives this very optimistic timeline in order to be inspirational to those who

Alex Filippenko (36:03.480)

are going out there.

Lex Fridman (36:04.480)

And certainly his success with the rocket that is reusable because it landed upright

Lex Fridman (36:10.000)

and all that.

Lex Fridman (36:11.000)

I mean, that's a game changer.

Alex Filippenko (36:12.400)

It's sort of like every time you flew from San Francisco to Los Angeles, you discard

Lex Fridman (36:16.880)

the airplane, right?

Lex Fridman (36:17.880)

I mean, that's crazy, right?

Lex Fridman (36:20.240)

So that's a game changer.

Lex Fridman (36:21.840)

But nevertheless, the timescale over which he thinks that there could be a real thriving

Lex Fridman (36:27.080)

colony on Mars, I think is far too optimistic.

Lex Fridman (36:30.680)

What's the biggest challenges to you?

Alex Filippenko (36:33.480)

One is just getting rockets, not rockets, but people out there and two is the colonization.

Lex Fridman (36:40.360)

Do you have thoughts about this, the challenges of this kind of prospect?

Alex Filippenko (36:44.360)

Yeah, I haven't thought about it in great detail other than recognizing that Mars is

Alex Filippenko (36:50.040)

a harsh environment.

Lex Fridman (36:51.040)

Yeah.

Alex Filippenko (36:52.040)

You don't have much of an atmosphere there.

Lex Fridman (36:53.360)

You've got less than a percent of Earth's atmosphere.

Lex Fridman (36:57.000)

So you'd need to build some sort of a dome right away, right?

Lex Fridman (37:00.320)

And that would take time.

Alex Filippenko (37:02.280)

You need to melt the water that's in the permafrost or have canals dug from which you transport

Lex Fridman (37:09.280)

it from the polar ice caps.

Alex Filippenko (37:11.840)

You know, I was reading recently in terms of like, what's the most efficient source

Lex Fridman (37:17.240)

of nutrition for humans that were to live on Mars?

Lex Fridman (37:20.440)

And people should look into this, but it turns out to be insects.

Lex Fridman (37:23.480)

Insects.

Alex Filippenko (37:24.480)

Yeah.

Lex Fridman (37:25.480)

So you want, you want to build giant colonies of insects and just be eating them.

Alex Filippenko (37:29.680)

Yeah, insects have a lot of protein.

Lex Fridman (37:30.680)

Yeah, a lot of protein.

Lex Fridman (37:32.000)

And they're easy to grow.

Lex Fridman (37:34.280)

Like you can think of them as farming.

Alex Filippenko (37:36.200)

Right.

Lex Fridman (37:37.200)

But it's not going to be as easy as growing a whole plot of potatoes like in the movie

Lex Fridman (37:41.960)

The Martian, you know, or something, right?

Lex Fridman (37:44.240)

It's not going to be that easy.

Lex Fridman (37:45.880)

But you know, so there's this thin atmosphere.

Lex Fridman (37:48.420)

It's got the wrong composition.

Alex Filippenko (37:49.620)

It's mostly carbon dioxide.

Lex Fridman (37:51.820)

There are these violent dust storms.

Alex Filippenko (37:54.900)

The temperatures are generally cold.

Lex Fridman (37:57.800)

You know, you'd need to do a lot of things.

Alex Filippenko (37:59.360)

You need to terraform it basically in order to make it nicely livable without some dome

Lex Fridman (38:04.840)

surrounding you.

Lex Fridman (38:05.840)

And if you, and if you insist on a dome, well, that's not going to house that many people,

Lex Fridman (38:10.880)

right?

Alex Filippenko (38:11.880)

You know, so let's look, let's look briefly then, you know, we're looking for a new apartment

Lex Fridman (38:17.480)

to move into.

Alex Filippenko (38:18.480)

Right.

Lex Fridman (38:19.480)

So let's look outside the solar system.

Lex Fridman (38:20.480)

Do you think you've, you've spoken about exoplanets as well?

Lex Fridman (38:25.440)

Do you think there's possible homes out there for us outside of our solar system?

Alex Filippenko (38:31.840)

There are lots and lots of homes.

Lex Fridman (38:33.960)

Possible homes.

Alex Filippenko (38:34.960)

There are, there's a planetary system around nearly every star you see in the sky.

Lex Fridman (38:40.480)

And one in five of those is thought to have a roughly Earth like planet.

Lex Fridman (38:45.920)

And that's a relatively new discovery.

Lex Fridman (38:46.920)

Yeah.

Alex Filippenko (38:47.920)

It's a new discovery.

Alex Filippenko (38:48.920)

I mean, the Kepler satellite, which was flying around above Earth's atmosphere was able to

Alex Filippenko (38:53.320)

monitor the brightness of stars with exquisite detail.

Lex Fridman (38:57.180)

And they could detect planets crossing the line of sight between us and the star, thereby

Alex Filippenko (39:03.880)

dimming its light for a short time ever so slightly.

Lex Fridman (39:08.080)

And it's amazing.

Lex Fridman (39:09.240)

So there are now thousands and thousands of these exoplanet candidates of which something

Lex Fridman (39:14.120)

like 90% are probably genuine exoplanets.

Lex Fridman (39:17.380)

And you have to remember that only about 1% of stars have their planetary system oriented

Alex Filippenko (39:25.100)

edge on to your line of sight, which is what you need for this transit method to work,

Lex Fridman (39:30.960)

right?

Alex Filippenko (39:31.960)

Your planetary angle won't work and certainly perpendicular to your line of sight.

Alex Filippenko (39:36.200)

That is in the plane of the sky won't work because the planet is orbiting the star and

Lex Fridman (39:40.920)

never crossing your line of sight.

Lex Fridman (39:43.680)

So the fact that they found planets orbiting about 1% of the stars that they looked at

Lex Fridman (39:51.240)

in this field of 150 plus thousand stars, they found planets around 1%.

Alex Filippenko (39:57.720)

You then multiply by the inverse of 1%, which is 1% is about what the fraction of the stars

Lex Fridman (40:06.820)

that have their planetary system oriented the right way.

Lex Fridman (40:10.720)

And that already back of the envelope calculation tells you that of order 50 to 100% of all

Lex Fridman (40:16.840)

stars have planets.

Lex Fridman (40:18.280)

And then they've been finding these Earth like planets, et cetera, et cetera.

Lex Fridman (40:21.780)

So there are many potential homes.

Alex Filippenko (40:23.840)

The problem is getting there.

Lex Fridman (40:26.680)

So then a typical bright star, Sirius, the brightest star in the sky, maybe not a typical

Alex Filippenko (40:32.720)

bright star, but it's 8.7 light years away.

Lex Fridman (40:37.600)

So that means the light took 8.7 years to reach us.

Alex Filippenko (40:43.440)

We're seeing it as it was about nine years ago.

Lex Fridman (40:47.460)

So then you ask how long would a rocket take to get there at Earth's escape speed, which

Alex Filippenko (40:54.560)

is 11 kilometers per second.

Lex Fridman (40:57.000)

And it turns out it's about a quarter of a million years.

Alex Filippenko (41:01.540)

Now that's 10,000 generations.

Lex Fridman (41:04.120)

Let's say a generation of humans is 25 years.

Lex Fridman (41:07.360)

So you'd need this colony of people that is able to sustain itself, all their food, all

Lex Fridman (41:14.760)

their waste disposal, all their water, all the recycling of everything.

Alex Filippenko (41:18.660)

For 10,000 generations, they have to commit themselves to living on this vehicle.

Lex Fridman (41:26.800)

I just don't see it happening.

Lex Fridman (41:28.920)

What I see potentially happening, if we avoid self destruction, intentional or unintentional

Alex Filippenko (41:34.520)

here on Earth, is that machines will do it, robots that can essentially hibernate.

Alex Filippenko (41:40.960)

They don't need to do much of anything for a long, long time as they're traveling.

Lex Fridman (41:44.640)

And moreover, if some energetic charged particle, some cosmic ray, hits the circuitry, it fixes

Alex Filippenko (41:50.720)

itself.

Lex Fridman (41:51.720)

Machines can do this.

Alex Filippenko (41:55.800)

It's a form of artificial intelligence.

Lex Fridman (41:57.940)

You just tell the thing, fix yourself basically.

Lex Fridman (42:00.100)

And then when you land on the planet, start producing copies of yourself, initially from

Lex Fridman (42:05.920)

materials that were perhaps sent, or you just have a bunch of copies there.

Lex Fridman (42:10.280)

And then they set up factories with which to do this.

Alex Filippenko (42:13.740)

This is very, very futuristic, but it's much more feasible, I think, than sending flesh

Lex Fridman (42:20.800)

and blood over interstellar distances, a quarter of a million years to even the nearest stars.

Lex Fridman (42:28.480)

You're subject to all kinds of charged particles and radiation.

Alex Filippenko (42:32.180)

You have to shield yourself really well.

Alex Filippenko (42:34.440)

That's by the way, one of the problems of going to Mars is that it's not a three day

Alex Filippenko (42:38.080)

journey like going to the moon.

Alex Filippenko (42:40.040)

You're out there for the better part of a year or two, and you're exposed to lots of

Alex Filippenko (42:45.460)

radiation, which typically doesn't do well with living tissue, or living tissue doesn't

Lex Fridman (42:52.560)

do well with the radiation.

Lex Fridman (42:54.800)

And the hope is that the robots, the AI systems might be able to carry the fire of consciousness,

Alex Filippenko (43:05.400)

whatever makes us humans, like a little drop of whatever makes us humans so special, not

Alex Filippenko (43:11.120)

to be too poetic about it.

Lex Fridman (43:12.720)

No, but I like being poetic about it because it's an amazing question.

Lex Fridman (43:17.480)

Is there something beyond just the bits, the ones and zeros to us?

Lex Fridman (43:22.400)

It's an interesting question.

Alex Filippenko (43:24.760)

I like to think that there isn't anything, and that how beautiful it is that our thoughts,

Lex Fridman (43:29.520)

our emotions, our feelings, our compassion all come from these ones and zeros, right?

Alex Filippenko (43:35.880)

That to me actually is a beautiful thought.

Lex Fridman (43:38.800)

And the idea that machines, silicon based life effectively, could be our natural evolutionary

Alex Filippenko (43:45.520)

descendants, not from a DNA perspective, but they are our creations and they then carry

Lex Fridman (43:51.360)

on.

Alex Filippenko (43:52.360)

That to me is a beautiful thought in some ways, but others find it to be a horrific

Lex Fridman (43:55.880)

thought.

Lex Fridman (43:56.880)

So that's exciting to you.

Alex Filippenko (43:58.480)

It is exciting to me as well because to me, from a purely an engineering perspective,

Alex Filippenko (44:05.240)

I believe it's impossible to create, like whatever systems we create that take over

Alex Filippenko (44:11.280)

the world, it's impossible for me to imagine that those systems will not carry some aspect

Alex Filippenko (44:17.540)

of what makes humans beautiful.

Lex Fridman (44:19.840)

So like a lot of people have these kind of paperclip ideas that we'll build machines

Alex Filippenko (44:26.000)

that are cold inside or philosophers call them zombies.

Alex Filippenko (44:31.240)

That naturally the systems that will out compete us on this earth will be cold and non conscious,

Alex Filippenko (44:41.660)

not capable of all the human emotions and empathy and compassion and love and hate,

Lex Fridman (44:48.720)

the beautiful mix of what makes us human.

Lex Fridman (44:53.160)

But to me, intelligence requires all of that.

Lex Fridman (44:56.520)

So in order to out compete humans, you better be good at the full picture.

Alex Filippenko (45:01.680)

Right.

Lex Fridman (45:02.680)

So artificial general intelligence, in my view, encompasses a lot of these attributes

Lex Fridman (45:08.280)

that you just talked about, curiosity, inquisitiveness, you know, right?

Alex Filippenko (45:13.540)

It might look very different than us humans, but it will have some of the magic.

Lex Fridman (45:17.160)

But it'll also be much more able to survive the onslaught of existential threats that

Alex Filippenko (45:24.120)

either we bring upon ourselves or don't anticipate here on earth, or that occasionally come from

Alex Filippenko (45:30.040)

beyond and there's nothing much we can do about a supernova explosion that just suddenly

Lex Fridman (45:34.400)

goes off.

Lex Fridman (45:36.200)

And really, if we want to move to other planets outside our solar system, I think realistically

Alex Filippenko (45:42.640)

that's a much better option than thinking that humans will actually make these gigantic

Alex Filippenko (45:48.200)

journeys.

Alex Filippenko (45:49.200)

And, you know, then I do this calculation for my class, you know, Einstein's special

Alex Filippenko (45:53.280)

theory of relativity says that you can do it in a short amount of time in your own frame

Lex Fridman (45:57.360)

of reference if you go close to the speed of light.

Lex Fridman (46:00.520)

But then you bring in E equals MC squared and you figure out how much energy it takes

Alex Filippenko (46:05.680)

to get you accelerated to close enough to the speed of light to make the time scales

Alex Filippenko (46:10.880)

short in your own frame of reference.

Lex Fridman (46:13.880)

And the amount of energy is just unfathomable, right?

Alex Filippenko (46:17.380)

We can do it at the Large Hadron Collider with protons, you know, we can accelerate

Lex Fridman (46:22.120)

them to 99.9999% of the speed of light, but that's just a proton.

Lex Fridman (46:27.560)

We're gazillions of protons, okay?

Lex Fridman (46:29.800)

And that doesn't even count the rocket that would carry us, the payload.

Lex Fridman (46:34.040)

And you would need to either store the fuel in the rocket, which then requires even more

Alex Filippenko (46:39.900)

mass for the rocket or collect fuel along the way, which, you know, is difficult.

Lex Fridman (46:44.920)

And so getting close to the speed of light, I think, is not an option either other than

Alex Filippenko (46:49.880)

for a little tiny thing like, you know, Yuri Milner and others are thinking about this,

Alex Filippenko (46:54.840)

the Starshot project where they'll send a little tiny camera to Alpha Centauri 4.2 light

Lex Fridman (47:00.040)

years away.

Alex Filippenko (47:01.040)

They'll zip past it, take a picture of the exoplanets that we know, orbit that three

Lex Fridman (47:06.080)

or more star system and say hello real quick.

Lex Fridman (47:09.320)

Say hello real quickly and then send the images back to us, okay?

Lex Fridman (47:12.760)

So that's a tiny little thing, right?

Alex Filippenko (47:15.060)

Maybe you can accelerate that to, they're hoping, 20% of the speed of light with a whole

Lex Fridman (47:19.960)

bunch of high powered lasers aimed at it.

Alex Filippenko (47:22.680)

It's not clear that other countries will allow us to do that, by the way, but that's a very

Lex Fridman (47:26.480)

forward looking thought.

Alex Filippenko (47:27.480)

I mean, I very much support the idea, but there's a big difference between sending a

Alex Filippenko (47:31.600)

little tiny camera and sending a payload of people with equipment that could then mine

Lex Fridman (47:38.920)

the resources on the exoplanet that they reach and then go forth and multiply, right?

Alex Filippenko (47:46.400)

Well, let's talk about the big galactic things and how we might be able to leverage them

Alex Filippenko (47:51.920)

to travel fast.

Alex Filippenko (47:52.920)

I know this is a little bit science fiction, but, you know, ideas of wormholes and ideas

Alex Filippenko (48:03.200)

at the edge of black holes that reveal to us that this fabric of space time could be

Lex Fridman (48:10.680)

messed with, perhaps.

Lex Fridman (48:13.240)

Is that at all an interesting thing for you?

Alex Filippenko (48:16.680)

I mean, in looking out at the universe and studying it as you have, is that also a possible,

Alex Filippenko (48:24.840)

like a dream for you that we might be able to find clues how we can actually use it to

Lex Fridman (48:29.720)

improve our transportation?

Alex Filippenko (48:31.600)

It's an interesting thought.

Alex Filippenko (48:32.600)

I'm certainly excited by the potential physics that suggests this kind of faster than light

Alex Filippenko (48:40.400)

travel effectively or, you know, cutting the distance to make it very, very short through

Lex Fridman (48:45.320)

a wormhole or something like that.

Lex Fridman (48:47.280)

Possible?

Lex Fridman (48:48.280)

No?

Alex Filippenko (48:49.280)

Well, you know, call me not very imaginative, but based on today's knowledge of physics,

Alex Filippenko (48:54.000)

which I realize, you know, people have gone down that rabbit hole and, you know, a century

Alex Filippenko (48:58.600)

ago, Lord Kelvin, one of the greatest physicists of all time, said that all of fundamental

Lex Fridman (49:03.440)

physics is done, the rest is just engineering, and guess what?

Alex Filippenko (49:07.280)

Then came special relativity, quantum physics, general relativity, how wrong he was.

Lex Fridman (49:12.340)

So let me not be another Lord Kelvin.

Alex Filippenko (49:15.120)

On the other hand, I think we know a lot more now about what we know and what we don't know

Lex Fridman (49:20.360)

and what the physical limitations are.

Lex Fridman (49:23.340)

And to me, most of these schemes, if not all of them, seem very farfetched, if not impossible.

Lex Fridman (49:30.300)

So travel through wormholes, for example, you know, it appears that for a non rotating

Alex Filippenko (49:36.820)

black hole, that's just a complete no go because the singularity is a point like singularity

Lex Fridman (49:42.480)

and you have to reach it to traverse the wormhole and you get squished by the singularity, okay?

Alex Filippenko (49:49.640)

Now for a rotating black hole, it turns out there is a way to pass through the event horizon,

Alex Filippenko (49:55.000)

the boundary of the black hole, and avoid the singularity and go out the other side

Alex Filippenko (49:59.940)

or even traverse the donut hole like singularity.

Lex Fridman (50:04.220)

In the case of a rotating black hole, it's a ring singularity.

Lex Fridman (50:06.880)

So there's actually two theoretical ways you could get through a rotating black hole or

Alex Filippenko (50:11.400)

a charged black hole, not that we expect charged black holes to exist in nature because they

Alex Filippenko (50:16.320)

would quickly bring in the opposite charge so as to neutralize themselves.

Lex Fridman (50:21.040)

But rotating black holes, definitely a reality.

Alex Filippenko (50:23.640)

We now have good evidence for them.

Lex Fridman (50:25.720)

Do they have traversable wormholes?

Alex Filippenko (50:29.240)

Probably not because it's still the case that when you go in, you go in with so much energy

Alex Filippenko (50:34.760)

that it either squeezes the wormhole shut or you encounter a whole bunch of incoming

Lex Fridman (50:42.280)

and outgoing energy that vaporizes you.

Lex Fridman (50:46.080)

It's called the mass inflation instability, and it just sort of vaporizes you.

Alex Filippenko (50:50.600)

Nevertheless, you could imagine, well, you're in some vapor form, but if you make it through,

Lex Fridman (50:55.060)

maybe you could reform or something.

Lex Fridman (50:58.200)

So it's still information.

Lex Fridman (50:59.200)

Yeah, it's still information.

Lex Fridman (51:00.200)

It's scrambled information, but there's a way maybe of bringing it back, right?

Lex Fridman (51:04.480)

But then the thing that really bothers me is that as soon as you have this possibility

Alex Filippenko (51:11.680)

of traversal of a wormhole, you have to come to grips with a fundamental problem, and that

Alex Filippenko (51:16.760)

is that you could come back to your universe at a time prior to your leaving, and you could

Alex Filippenko (51:24.400)

essentially prevent your grandparents from ever meeting.

Lex Fridman (51:27.480)

This is called the grandfather paradox, right?

Lex Fridman (51:29.580)

And if they never met, and if your parents were never born, and if you were never born,

Lex Fridman (51:33.880)

how would you have made the journey to prevent the history from allowing you to exist, right?

Alex Filippenko (51:44.880)

It's a violation of causality, of cause and effect.

Lex Fridman (51:48.560)

Now physicists such as myself take causality violation very, very seriously.

Alex Filippenko (51:54.720)

We've never seen it.

Lex Fridman (51:55.720)

You took a stand.

Lex Fridman (51:56.720)

Yeah, I mean, it's one of these back to the future type movies, right?

Lex Fridman (52:01.600)

And you have to work things out in such a way that you don't mess things up, right?

Alex Filippenko (52:06.640)

Some people say that, well, you come back to the universe, but you come back in such

Lex Fridman (52:10.500)

a way that you cannot affect your journey.

Lex Fridman (52:14.960)

But then that seems kind of contrived to me.

Alex Filippenko (52:19.360)

Or some say that you end up in a different universe, and this also goes into the many

Alex Filippenko (52:24.640)

different types of the multiverse hypothesis and the many worlds interpretation and all

Lex Fridman (52:28.880)

that.

Lex Fridman (52:29.880)

And then it's not the universe from which you left, right?

Lex Fridman (52:34.000)

And you don't come back to the universe from which you left.

Lex Fridman (52:37.000)

And so you're not really going back in time to the same universe, and you're not even

Lex Fridman (52:42.700)

going forward in time necessarily then to the same universe, right?

Alex Filippenko (52:46.720)

You're ending up in some other universe.

Lex Fridman (52:50.200)

So what have you achieved, right?

Alex Filippenko (52:53.680)

You've traveled.

Lex Fridman (52:56.600)

You ended up in a different place than you started in more ways than one.

Alex Filippenko (53:00.720)

Yeah.

Lex Fridman (53:01.720)

And then there's this idea, the Alcubierre drive, where you warp space time in front

Alex Filippenko (53:07.320)

of you so as to greatly reduce the distance, and you can expand the space time behind you.

Lex Fridman (53:12.480)

So you're sort of riding a wave through space time.

Lex Fridman (53:16.120)

But the problem I see with that, beyond the practical difficulties and the energy requirements,

Lex Fridman (53:20.440)

and by the way, how do you get out of this bubble through which you're riding this wave

Lex Fridman (53:25.740)

of space time?

Lex Fridman (53:26.740)

And Miguel Alcubierre acknowledged all these things.

Alex Filippenko (53:29.160)

He said this is purely theoretical, fanciful, and all that.

Lex Fridman (53:31.880)

But a fundamental problem I see is that you'd have to get to those places in front of you

Lex Fridman (53:38.280)

so as to change the shape of space time so as to make the journey quickly.

Lex Fridman (53:44.080)

But to get there, you got there in the normal way at a speed considerably less than that

Alex Filippenko (53:49.320)

of light.

Lex Fridman (53:50.740)

So in a sense, you haven't saved any time, right?

Lex Fridman (53:53.640)

You might as well have just taken that journey and gotten to where you were going, right?

Lex Fridman (54:00.680)

What have you done?

Alex Filippenko (54:01.680)

It's not like you snap your fingers and say, okay, let that space there be compressed,

Lex Fridman (54:06.480)

and then I'll make it over to Alpha Centauri in the next month.

Alex Filippenko (54:10.040)

You can't snap your fingers and do that.

Lex Fridman (54:12.240)

Yeah.

Lex Fridman (54:13.240)

But yeah, we're sort of assuming that we can fix all the biological stuff that requires

Alex Filippenko (54:18.260)

for humans to persist through that whole process, because ultimately, it might go down to just

Alex Filippenko (54:24.560)

extending the life of the human in some form, whether it's through the robot, through the

Alex Filippenko (54:29.360)

digital form, or actually just figuring out genetically how to live forever, because that

Alex Filippenko (54:35.240)

journey that you mentioned, the long journey, might be different if somehow our understanding

Alex Filippenko (54:41.800)

of genetics, of our understanding of our own biology, all that kind of stuff, that's another

Alex Filippenko (54:47.280)

trajectory that possibly...

Lex Fridman (54:48.280)

Well, right.

Alex Filippenko (54:49.280)

If you could put us into some sort of suspended animation, hibernation or something, and greatly

Lex Fridman (54:54.080)

increase the lifetime, and so these 10,000 generations I talked about, what do they care?

Lex Fridman (54:58.580)

It's just one generation, and they're asleep, okay?

Lex Fridman (55:00.960)

It's a long nap.

Lex Fridman (55:02.280)

So then you can do it.

Lex Fridman (55:04.500)

It's still not easy, right?

Alex Filippenko (55:05.500)

Because you've got some big old huge colony, and that just through E equals MC squared,

Lex Fridman (55:09.320)

right?

Alex Filippenko (55:10.320)

That's a lot of mass.

Lex Fridman (55:11.320)

That's a lot of stuff to accelerate.

Lex Fridman (55:13.480)

The Newtonian kinetic energy is gigantic, right?

Lex Fridman (55:18.200)

So you're still not home free, but at least you're not trying to do it in a short amount

Lex Fridman (55:23.480)

of clock time, right?

Alex Filippenko (55:26.240)

Which if you look at E equals MC squared, requires truly unfathomable amounts of energy,

Alex Filippenko (55:32.520)

because the energy is your rest mass, M naught C squared, divided by the square root of one

Lex Fridman (55:39.800)

minus V squared over C squared.

Lex Fridman (55:42.200)

And if your listeners want to just sort of stick into their pocket calculator, as V over

Alex Filippenko (55:46.440)

C approaches one, that one over the square root of one minus V squared over C squared

Alex Filippenko (55:52.100)

approaches infinity.

Lex Fridman (55:54.160)

So if you wanted to do it in zero time, you'd need an infinite amount of energy.

Alex Filippenko (55:58.520)

That's basically why you can't reach, let alone exceed the speed of light, for a particle

Lex Fridman (56:04.680)

moving through a preexisting space.

Alex Filippenko (56:07.960)

It's that it takes an infinite amount of energy to do so.

Lex Fridman (56:11.640)

So that's talking about us going somewhere.

Lex Fridman (56:15.080)

What about, one of the things that inspires a lot of folks, including myself, is the possibility

Alex Filippenko (56:22.040)

that there's other, that this conversation is happening on another planet in different

Alex Filippenko (56:27.920)

forms with intelligent life forms.

Lex Fridman (56:35.360)

So first we could start, as a cosmologist, what's your intuition about whether there

Lex Fridman (56:41.840)

is or isn't intelligent life out there?

Lex Fridman (56:45.400)

Outside of our own?

Alex Filippenko (56:46.400)

Yeah, I would say I'm one of the pessimists in that I don't necessarily think that we're

Alex Filippenko (56:51.280)

the only ones in the observable universe, which goes out, you know, roughly 14 billion

Alex Filippenko (56:57.880)

years in light travel time and more like, you know, 46 billion years when you take into

Lex Fridman (57:02.640)

account the expansion of space.

Lex Fridman (57:04.280)

So the diameter of our observable universe is something like, you know, 90, 92 billion

Lex Fridman (57:08.480)

light years.

Alex Filippenko (57:09.700)

That encompasses, you know, a hundred billion to a trillion galaxies with, you know, a hundred

Lex Fridman (57:16.040)

billion stars each.

Lex Fridman (57:17.280)

So now you're talking about something like 10 to the 22nd, 10 to the 23rd power stars

Lex Fridman (57:22.400)

and roughly an equal number of Earth like planets and so on.

Lex Fridman (57:27.880)

So there may well be other intelligent life.

Lex Fridman (57:32.000)

But your sense is our galaxy is not teeming with life.

Alex Filippenko (57:35.120)

Yeah, our galaxy, our Milky Way galaxy with several hundred billion stars and potentially

Lex Fridman (57:41.080)

habitable planets is not teeming with intelligent life.

Alex Filippenko (57:44.080)

Intelligent.

Alex Filippenko (57:45.080)

Yeah, I wouldn't, well, I'll get to the primitive life, the bacteria in a moment, but, you know,

Alex Filippenko (57:51.520)

we may well be the only ones in our Milky Way galaxy, at most a handful, I'd say, but

Alex Filippenko (57:56.920)

I'd probably side with the school of thought that suggests we're the only ones in our own

Alex Filippenko (58:03.200)

galaxy, just because I don't see human intelligence as being a natural evolutionary path for life.

Lex Fridman (58:13.520)

I mean, there's a number of arguments.

Alex Filippenko (58:16.000)

First of all, there's been more than 10 billion species of life on Earth in its history.

Alex Filippenko (58:22.000)

Everything has approached our level of intelligence and mechanical ability and curiosity.

Alex Filippenko (58:27.400)

You know, whales and dolphins appear to be reasonably intelligent, but there's no evidence

Lex Fridman (58:31.600)

that they can think abstract thoughts that they're curious about the world.

Alex Filippenko (58:35.360)

They certainly can't build machines with which to study the world.

Lex Fridman (58:39.720)

So that's one argument.

Alex Filippenko (58:41.520)

Secondly, we came about as early hominids only four or five million years ago and as

Lex Fridman (58:47.560)

homo sapiens only about a quarter of a million years ago.

Lex Fridman (58:52.100)

So for the vast majority of the history of life on Earth, an intelligent alien zipping

Alex Filippenko (58:56.920)

by Earth would have said there's nothing particularly intelligent or mechanically able on Earth.

Alex Filippenko (59:02.640)

Okay.

Alex Filippenko (59:03.640)

Thirdly, it's not clear that our intelligence is a long term evolutionary advantage.

Alex Filippenko (59:10.760)

Now it's clear that in the last 100 years, 200 years, we've improved the lives of hundreds

Alex Filippenko (59:15.680)

of millions of people, but at the risk of potentially destroying ourselves either intentionally

Alex Filippenko (59:21.800)

or unintentionally or through neglect, as we discussed before.

Alex Filippenko (59:26.200)

That's a really interesting point, which is it's possible that they're a huge amount of

Alex Filippenko (59:32.120)

intelligent civilizations have been born even through our galaxy, but they live very briefly

Lex Fridman (59:38.200)

and they die.

Alex Filippenko (59:39.200)

Flash bulbs in the night.

Lex Fridman (59:42.200)

That brings me to the fourth issue and that is the Fermi paradox.

Lex Fridman (59:47.960)

If they're common, where the hell are they?

Alex Filippenko (59:52.440)

Notwithstanding the various UFO reports in Roswell and all that, they just don't meet

Alex Filippenko (59:56.480)

the bar.

Lex Fridman (59:57.700)

They don't clear the bar of scientific evidence in my opinion.