Avi Loeb: Aliens, Black Holes, and the Mystery of the Oumuamua

Avi Loeb (02:59.760)

universe, are there now or have ever been other sentient civilizations that, like ours, explored

Avi Loeb (03:07.440)

the stars and left evidence of their efforts? So let me ask, are we alone? That's an excellent

Avi Loeb (03:14.160)

question. For me, the answer is sort of clear because I start from the principle of modesty.

Avi Loeb (03:22.880)

You know, if we believe that we are alone and special and unique, that shows arrogance. My

Avi Loeb (03:28.800)

daughters, when they were infants, they tended to think that they are special, unique, and then they

Avi Loeb (03:33.600)

went out to the street and realized that other kids are very much like them. And then they

Avi Loeb (03:39.840)

developed a sense of a better perspective about themselves. And I think the only reason that we

Avi Loeb (03:45.920)

are still thinking that we are special is because we haven't searched well enough to find others

Avi Loeb (03:51.840)

that might even be better than us. And, you know, I say that because I look at the newspaper every

Avi Loeb (03:57.920)

morning and I see that we do foolish things. We are not necessarily the most intelligent ones.

Lex Fridman (04:02.880)

And if you think about it, if you open a recipe book, you see that out of the same ingredients,

Avi Loeb (04:08.560)

you can make very different cakes, depending on how you put them together and how you heat them

Avi Loeb (04:14.240)

up. And what is the chance that by taking the soup of chemicals that existed on earth and cooking it

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one way to get our life, that you got the best cake possible? I mean, we are probably not the

Avi Loeb (04:28.480)

sharpest cookie in the jar. And my question is, I mean, it's pretty obvious to me that we are

Avi Loeb (04:34.240)

probably not alone because half of all the sun like stars we know now as astronomers, half of

Avi Loeb (04:40.000)

the sun like stars from the Kepler satellite data have a planet the size of the earth, roughly at

Avi Loeb (04:47.760)

the same distance that the earth is from the sun. And that means that they can have liquid water on

Avi Loeb (04:54.000)

their surface and the chemistry of life as we know it. So if you roll the dice billions of times,

Avi Loeb (05:00.160)

just within the Milky Way galaxy, and then you have tens of billions of galaxies like it within

Avi Loeb (05:07.280)

the observable volume of the universe, it would be extremely arrogant to think that we are special.

Avi Loeb (05:11.520)

I would think that we are sort of middle of the road, typical forms of life. And that's why

Avi Loeb (05:17.040)

nobody pays attention to us. If you go down the street on a sidewalk and you see an ant,

Avi Loeb (05:23.200)

you don't pay attention or a special respect to that ant, you just continue to walk. And

Lex Fridman (05:28.000)

so I think that we are sort of average, not very interesting, not exciting, so nobody cares about

Avi Loeb (05:33.680)

us. We tend to think that we are special, but that's a sign of immaturity. And we're very early

Avi Loeb (05:39.200)

on in our development. Yes, that's another thing that we have our technology only for 100 years,

Lex Fridman (05:44.640)

and it's evolving exponentially right now on a three year timescale. So imagine what would happen

Avi Loeb (05:50.320)

in a hundred years, in a thousand years, in a million years or in a billion years. Now, the Sun

Avi Loeb (05:56.000)

is actually relatively late in the star formation history of the universe. Most of the Sun like stars

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formed earlier, and some of them already died, you know, became white dwarfs. And so if you imagine

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that a civilization like ours existed around a typical Sun like star, by now, if they survived,

Avi Loeb (06:16.880)

they could be a billion years old. And then imagine a billion year technology, it would

Avi Loeb (06:22.560)

look like magic to us, you know, an approximation to God, we wouldn't be able to understand it.

Lex Fridman (06:28.640)

And so in my view, we should be humble. And by the way, we should probably just listen and not speak,

Avi Loeb (06:36.080)

because there is a risk, right? If you are inferior, there is a risk if you speak too loudly,

Avi Loeb (06:43.120)

something bad may happen to you. You mentioned, we should be humble also in the sense,

Avi Loeb (06:50.240)

with the analogy to ants, that they might be better than us. So there's a kind of scale that

Avi Loeb (06:58.000)

we're talking about. And in the question, you mentioned the word sentient. So sentience,

Avi Loeb (07:03.920)

or maybe the more basic formulation is consciousness. Do you think that this

Avi Loeb (07:13.360)

thing within us humans in terms of the typical life form of consciousness is the essential

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element that permeates other, if there's other alien civilizations out there, that they have

Avi Loeb (07:25.840)

something like consciousness as well? Or is this, I guess I'm asking, can you try to untangle the

Avi Loeb (07:31.680)

word sentient? Yeah, so that's a good question. I think what is most abundant, depending on how

Avi Loeb (07:38.720)

long it survives. So if you look at us, as an example, we are now, we do have consciousness

Lex Fridman (07:46.480)

and we do have technology. But the technologies that we are developing are also means for our

Avi Loeb (07:53.280)

own destruction, as we can tell. You know, we can change the climate if we are not careful enough.

Avi Loeb (07:58.880)

We can go into nuclear wars. So we are developing means for our own destruction through

Avi Loeb (08:05.920)

self inflicted wounds. And it might well be that creatures like us are not long lived, that

Avi Loeb (08:13.760)

crocodiles on other planets live for billions of years. They don't destroy themselves, they live

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naturally. And so if you look around, the most common thing would be dumb animals that live for

Avi Loeb (08:26.400)

long times, you know, not those that have conscious. But in terms of changing the environment, I think

Avi Loeb (08:34.480)

since, I mean, humans develop tools, they develop the ability to construct technologies that would

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lift us from this planet that we were born in. And that's something animals without a

Avi Loeb (08:48.800)

conscious, consciousness cannot really do. And so I, you know, in terms of looking for things

Avi Loeb (08:57.920)

that are new, that went beyond the circumstances they were born into, I would think that even if

Avi Loeb (09:05.040)

they're short lived, these are the creatures that made the biggest difference to their environment.

Lex Fridman (09:10.480)

And we can search for them, you know, even if they're short lived, and most of the civilizations

Avi Loeb (09:15.280)

are dead by now. Even if that's the case. That's sad to think about, by the way.

Avi Loeb (09:19.680)

Well, but if you look on Earth, that, you know, there are lots of cultures that existed throughout

Avi Loeb (09:24.400)

time, and they're dead by now. The Mayan culture was very sophisticated, died. But we can find

Avi Loeb (09:30.400)

evidence for it and learn about it just by archaeology, digging into the ground, looking.

Lex Fridman (09:35.600)

And so we can do the same thing in space, look for dead civilizations. And perhaps we can learn a

Avi Loeb (09:41.680)

lesson why they died and behave better so that we will not share the same fate. So I think, you know,

Avi Loeb (09:48.960)

there is a lesson to be learned from the sky. And by the way, I should also say, if we find

Avi Loeb (09:54.640)

a technology that we have not dreamed of, that we can import to Earth, that may be a better

Avi Loeb (10:01.760)

strategy for making a fortune than going to Silicon Valley or going to Wall Street. Because

Avi Loeb (10:07.680)

you make a jump start into something of the future. So that's one way to do the leap is

Avi Loeb (10:13.520)

actually to find, to literally discover versus come up with the idea in our own limited human

Avi Loeb (10:20.560)

capacity, like a cognitive capacity. It would look like, it would feel like cheating in an exam

Avi Loeb (10:25.840)

where you look over the shoulder of a student next to you. Yeah. But it's not good on an exam,

Lex Fridman (10:30.960)

but it is good when you're coming up with technology that could change the fabric of

Avi Loeb (10:35.200)

human civilization. But there is, you know, in my neck of the woods of artificial intelligence,

Avi Loeb (10:42.320)

there's a lot of trajectories one can imagine of creating very powerful beings,

Avi Loeb (10:50.240)

the technology that's essentially, you know, you can call super intelligence that could achieve

Avi Loeb (10:57.040)

space exploration, all those kinds of things without consciousness, without something that

Avi Loeb (11:01.520)

to us humans looks like consciousness. And there, you know, there is a sad feeling I have that

Avi Loeb (11:09.680)

consciousness too, in terms of us being humble, is a thing we humans take too seriously. That it's,

Avi Loeb (11:17.040)

we think it's special just because we have it. But it could be a thing that's actually holding

Avi Loeb (11:21.040)

us back in some kind of way. It may well be. It may well be. I should say something about AI,

Avi Loeb (11:26.160)

because I do think it offers a very important step into the future. If you look at the Old

Avi Loeb (11:33.600)

Testament, the Bible, there is this story about Noah's Ark that you might know about. Noah

Avi Loeb (11:41.440)

knew about a great flood that is about to endanger all life on earth. So he decided to build an ark.

Lex Fridman (11:49.680)

And the Bible actually talks about specifically what the size of this ark was, what the dimensions

Avi Loeb (11:55.440)

were. Turns out it was quite similar to Oumuamua that we will discuss in a few minutes. But at any

Avi Loeb (12:02.480)

event, he built this ark and he put animals on it so that they were saved from the great flood.

Avi Loeb (12:08.960)

Now, you can think about doing the same on earth, because there are risks for future catastrophes.

Avi Loeb (12:16.000)

You know, we could have the self inflicted wounds that we were talking about, like nuclear war,

Avi Loeb (12:20.960)

changing the climate. Or there could be an asteroid impacting us, just like the dinosaurs

Avi Loeb (12:26.720)

died. The dinosaurs didn't have science, astronomy. They couldn't have a warning system.

Lex Fridman (12:32.400)

But there was this big stone, big rock that approached them. It must have been a beautiful

Avi Loeb (12:37.600)

sight. Just when it was approaching, it got very big and then smashed them and killed them. So

Avi Loeb (12:44.080)

you could have a catastrophe like that. Or in a billion years, the sun will basically boil off

Avi Loeb (12:48.640)

all the oceans on earth. And currently all our eggs are in one basket, but we can spread them.

Avi Loeb (12:57.040)

It's sort of like the printing press, if you think about it. The revolution that Gutenberg

Avi Loeb (13:02.400)

brought is there were very few copies of the Bible at the time, and each of them was precious

Avi Loeb (13:07.520)

because it was handwritten. But once the printing press produced multiple copies, you know,

Avi Loeb (13:13.040)

if something bad happened to one of the copies, it wasn't a catastrophe. You know, it wasn't

Avi Loeb (13:17.360)

disaster because you had many more copies. And so if we have copies of life here on earth elsewhere,

Avi Loeb (13:25.520)

then we avoid the risk of it being eliminated by a single point breakdown, catastrophe.

Lex Fridman (13:32.960)

So the question is, can we build NOx spaceship that will carry life as we know it? Now,

Avi Loeb (13:39.680)

you might think we have to put elephants and whales and birds on a big spaceship, but that's

Avi Loeb (13:45.840)

not true because all you need to know is the DNA making, the genetic making of these animals,

Avi Loeb (13:52.640)

put it on a computer system that has AI plus a 3D printer so that this CubeSat, which is rather

Avi Loeb (14:02.720)

small, can go with this information to another planet and use the raw materials there to produce

Avi Loeb (14:09.600)

synthetic life. And that would be a way of producing copies, just like the Gutenberg printing press.

Avi Loeb (14:16.400)

Yeah, and it doesn't have to be exact copies of the humans, it could just contain some basic

Avi Loeb (14:21.440)

elements of life and then have enough life on board that it could reproduce the process of

Avi Loeb (14:29.040)

evolution on another place. So I mean, that also makes you sad, of course, because you confront

Avi Loeb (14:34.800)

the mortality of your own little precious consciousness and all your own memories and

Avi Loeb (14:38.400)

knowledge and all that stuff. But who cares? I care about mine, right? And you care about yours.

Avi Loeb (14:44.400)

No, no, I actually don't. If you're an astronomer, one thing that you learn from the universe

Avi Loeb (14:50.240)

is to be modest because you're not so significant. I mean, think about it, all these emperors and

Avi Loeb (14:56.000)

kings that conquered a piece of land on Earth and were extremely proud. You see these images

Avi Loeb (15:01.280)

of kings and emperors that usually are alpha males and they stand strong and they're very

Avi Loeb (15:10.480)

proud of themselves. But if you think about it, there are 10 to the power 20 planets like the

Avi Loeb (15:15.600)

Earth in the observable volume of the universe. And this view of conquering a piece of land and

Avi Loeb (15:22.400)

even conquering all of Earth is just like an ant hugging a single grain of sand on the landscape

Avi Loeb (15:29.120)

of a huge beach. That's not very impressive. So you can't be arrogant. If you see the big picture,

Avi Loeb (15:35.840)

you have to be humble. Also, we are short lived. Within 100 years, that's it. So what does it teach

Avi Loeb (15:44.000)

you? First to be humble, modest. You never have significant powers relative to the big scheme

Avi Loeb (15:49.760)

of things. And second, you should appreciate every day that you live and learn about the world.

Avi Loeb (15:56.160)

Humble and still grateful. Yes, exactly. Well, let's talk about probably the most interesting

Avi Loeb (16:07.040)

object I've heard about and also the most fun to pronounce. Oumuamua. Can you tell me the story

Avi Loeb (16:13.840)

of this object and why it may be an important event in human history? And is it possibly a piece

Avi Loeb (16:21.120)

of alien technology? Right. So this is the first object that was spotted close to Earth from

Avi Loeb (16:29.600)

outside the solar system. And it was found on October 19th, 2017. And at that time, it was

Avi Loeb (16:38.240)

receding away from us. And at first, astronomers thought it must be a piece of rock, you know,

Avi Loeb (16:44.960)

just like all the asteroids and comets that we have seen from within the solar system.

Lex Fridman (16:49.440)

And it just came from another star. I should say that the actual discovery of this object

Avi Loeb (16:54.240)

was surprising to me because a decade earlier, I wrote the first paper together with Ed Turner

Lex Fridman (16:59.600)

and Amaya Moro Martin that tried to predict whether the same telescope that was surveying

Avi Loeb (17:06.240)

the sky, PanSTARRS from Hawaii, would find anything from interstellar space, given what

Avi Loeb (17:12.720)

we know about the solar system. So if you assume that other planetary systems have similar

Avi Loeb (17:17.760)

abundance of rocks and you just calculate how many should be ejected into interstellar space,

Avi Loeb (17:23.760)

the conclusion is no, we shouldn't find anything with PanSTARRS. To me, I apologize for probably

Avi Loeb (17:30.560)

revealing my stupidity, but it was surprising to me that so few interstellar objects from outside

Avi Loeb (17:36.320)

this whole system have ever been detected. No, nothing. None has been. You do maybe talk about

Avi Loeb (17:44.000)

it that there has been one or two rocks since then. Well, since then, there was one called

Avi Loeb (17:50.240)

the Borisov. It was discovered by an amateur Russian astronomer, Gennady Borisov. And that one

Avi Loeb (17:58.240)

looked like a comet. And just like a comet from within the solar system. But this is a really

Avi Loeb (18:05.200)

important point. Sorry to interrupt it. You showed that it's unlikely that a rock from another solar

Avi Loeb (18:10.880)

system would arrive to ours. Right. And so the actual detection of this one was surprising by

Avi Loeb (18:16.880)

itself to me. Yes. But then, so at first they thought maybe it's a comet or an asteroid,

Lex Fridman (18:24.480)

but then it didn't look like anything we've seen before. Borisov did look like a comet. So people

Avi Loeb (18:31.520)

asked me afterwards and said, you know, doesn't it convince you if Borisov looks like a comet,

Avi Loeb (18:38.400)

doesn't it convince you that Oumuamua is also natural? And I said, you know, when I went on the

Avi Loeb (18:44.160)

first date with my wife, she looked special to me. And since then I met many women. That didn't

Avi Loeb (18:50.640)

change my opinion of my wife. So, you know, that's not an argument. Anyway, so why did the Oumuamua

Avi Loeb (18:59.120)

look weird? Let me explain. So first of all, astronomers monitored the amount of light,

Avi Loeb (19:05.200)

sunlight that it reflects. And it was tumbling, spinning every eight hours. And as it was spinning,

Avi Loeb (19:13.120)

the brightness that we saw from that direction, we couldn't resolve it because it's tiny. It's

Avi Loeb (19:18.000)

about a hundred meters, a few hundred feet, size of a football field. And we cannot, from Earth,

Avi Loeb (19:24.080)

with existing telescopes, we cannot resolve it. The only way to actually get a photograph of it

Avi Loeb (19:29.600)

is to send a camera close to it. And that was not possible at the time that Oumuamua was discovered

Avi Loeb (19:38.080)

because it was already moving away from us faster than any rocket we can send. It's sort of like a

Avi Loeb (19:43.680)

guest that appeared for dinner. And then by the time we realized that it's weird, the guest is

Avi Loeb (19:49.440)

already out the front door into the dark street. What we would like to find is an object like it

Avi Loeb (19:56.160)

approaching us, because then you can send the camera irrespective of how fast it moves. And

Avi Loeb (1:00:03.040)

there are lots of implicit assumptions about all the other factors that will enable us to detect

Avi Loeb (1:00:08.640)

the signal. Now, I should say the Drake equation has a very limited validity just for signals from

Avi Loeb (1:00:15.760)

civilizations that are transmitting at the time that you're observing them. However, we can do

Avi Loeb (1:00:22.640)

much better than that. We can look for artifacts that they left behind. Even if they are dead,

Lex Fridman (1:00:29.360)

you can look for industrial pollution in the atmosphere of planets. Why do I bring this up?

Lex Fridman (1:00:35.200)

Why do I bring this up? Again, to show you the conservatism of the mainstream in astronomy.

Lex Fridman (1:00:40.320)

And by the way, I have leadership positions. I was chair of the astronomy department for nine

Avi Loeb (1:00:45.360)

years, the longest serving chair at Harvard. And I'm the chair of the board on physics and astronomy

Avi Loeb (1:00:51.440)

of the National Academies. It's a primary board. And I'm director of two centers at Harvard and so

Avi Loeb (1:00:59.600)

forth. So I do represent the community in various ways. But at the same time, I'm a little bit

Avi Loeb (1:01:06.800)

disappointed by the conservatism that people have. And so let me give you an illustration of that.

Lex Fridman (1:01:11.920)

So the astronomy community actually is going right now through the process of defining its goals for

Avi Loeb (1:01:18.240)

the next decade. And there are proposals for telescopes that would cost billions of dollars

Lex Fridman (1:01:25.280)

and whose goal is to find evidence for oxygen in the atmosphere of planets around other stars,

Avi Loeb (1:01:33.360)

with the idea that this would be a marker, a signature of life. Now, the problem with that

Avi Loeb (1:01:40.320)

is Earth didn't have much oxygen in its atmosphere for the first two billion years. Roughly half of

Avi Loeb (1:01:47.840)

its life, it didn't have much oxygen. But it had life. It had microbial life. It's not

Avi Loeb (1:01:53.760)

it's not clear yet as of yet what the origin is for the rise in the oxygen level after two

Avi Loeb (1:02:01.920)

billion years, about 2.4 billion years ago. But we know that a planet can have life without oxygen

Avi Loeb (1:02:10.320)

in the atmosphere because Earth did it. The second problem with this approach is that you can have

Avi Loeb (1:02:16.720)

oxygen from natural processes. You can break water molecules and make oxygen. So even if you find it,

Avi Loeb (1:02:23.440)

it will never tell you that for sure life exists there. And so even with these billions of dollars,

Avi Loeb (1:02:30.080)

the mainstream community will never be confident whether there is life. Now, how can it be

Avi Loeb (1:02:37.280)

confident? There is actually a way. If instead of looking with the same instruments, if you look for

Avi Loeb (1:02:42.400)

molecules that indicate industrial pollution, for example, CFCs that are produced by refrigerating

Avi Loeb (1:02:50.000)

systems or industries here on Earth, that they do the ozone layer, you can search for that. And

Avi Loeb (1:02:55.520)

I wrote a paper five years ago suggesting that. Now, what's the problem? You can just tell NASA,

Avi Loeb (1:03:01.680)

I want to build this telescope to search for oxygen, but also for industrial pollution.

Avi Loeb (1:03:08.240)

Nobody would say that because it sounds like on the periphery of the field. And I ask you,

Lex Fridman (1:03:16.560)

why would? Hilarious. Because that's exactly, I mean, that would be saying is quite brilliant. I

Avi Loeb (1:03:22.240)

mean, because it's a really strong signal. And if life, if there's alien civilizations out there,

Avi Loeb (1:03:29.760)

then they're probably going to be many of them. And they're probably going to be more advanced

Avi Loeb (1:03:34.480)

than us. And they're probably going to have something like industrial pollution, which would

Avi Loeb (1:03:37.840)

be a much stronger signal than some basic gas, which could have a lot of different explanations.

Lex Fridman (1:03:44.160)

So like something like oxygen or, I mean, we could talk about signs of life on Venus and so on.

Lex Fridman (1:03:52.720)

But if you want a strong signal, it would be pollution. I love how garbage is.

Avi Loeb (1:03:58.400)

No, but the pollution, you have to understand, we think of pollution as a problem,

Lex Fridman (1:04:02.560)

but on a planet that was too cold, for example, to have a comfortable life on it, you can imagine

Avi Loeb (1:04:09.600)

terraforming it and putting a blanket of polluting gases such that it will be warmer. And that would

Avi Loeb (1:04:16.800)

be a positive change. So if an industrial or a technological civilization wants to terraform a

Avi Loeb (1:04:25.200)

planet that otherwise is too cold for them, they will do it. So what's the problem of defining it

Avi Loeb (1:04:31.200)

as a search goal using the same technologies? The problem is that there is a taboo. We're not

Avi Loeb (1:04:39.840)

supposed to discuss extraterrestrial intelligence. There is no funding for this subject, not much,

Avi Loeb (1:04:45.280)

very little. And young people, because of the bullying on Twitter, you know, all the social

Avi Loeb (1:04:51.760)

media and elsewhere, young people with talent that are curious about these questions do not enter

Avi Loeb (1:04:58.160)

this field of study. And obviously, if you step on the grass, it will never grow, right? So if you

Avi Loeb (1:05:05.840)

don't give funding, obviously, you know, the mainstream community says, look, nothing was

Avi Loeb (1:05:10.480)

discovered so far. Obviously, nothing would be discovered. If talented people go to other

Avi Loeb (1:05:15.760)

districts, you never search for it well enough, you will never find anything. I mean, look at

Avi Loeb (1:05:21.040)

gravitational wave astrophysics. It's a completely new window into the universe, pioneered by Ray

Avi Loeb (1:05:26.000)

Weiss at MIT. And at first, it was ridiculed. And thanks to some administrators at the National

Avi Loeb (1:05:34.400)

Science Foundation, it received funding, despite the fact that the mainstream of the astronomy

Avi Loeb (1:05:39.760)

community was very resistant to it. And now it's considered a frontier. So all these people that

Avi Loeb (1:05:47.280)

I remember as a young postdoc, these people that bashed this field and said bad things about

Avi Loeb (1:05:51.920)

people, you know, said nothing will come out of it. Now they say, oh, yeah, of course, you know,

Avi Loeb (1:05:57.840)

the Nobel Prize was given to the LIGO collaboration. Of course, now they are supportive

Avi Loeb (1:06:06.320)

of it. But my point is, if you suppress innovation early on, there are lots of missed opportunities.

Avi Loeb (1:06:15.920)

The discovery of exoplanets is one example. You know, in 1952, there was an astronomer called

Avi Loeb (1:06:21.680)

the name Otto Struve. And he wrote a paper saying, why don't we search for Jupiter like planets

Avi Loeb (1:06:31.440)

close to their host star? Because if they're close enough, they would move the star back and forth,

Lex Fridman (1:06:36.960)

and we can detect the signal. And so astronomers on time allocation committees of telescopes

Avi Loeb (1:06:44.480)

for 40 years argued, this is not possible because we know why Jupiter resides so far from the Sun.

Avi Loeb (1:06:53.440)

You cannot have Jupiter so close because there is this region where ice forms far from the Sun.

Lex Fridman (1:06:59.120)

And beyond that region is where Jupiter like planets can form. There was a theory behind

Avi Loeb (1:07:03.600)

it which ended up being wrong by today's standards. But anyway, they did not give time

Lex Fridman (1:07:09.680)

on telescopes to search for such systems until the first system was discovered

Avi Loeb (1:07:14.800)

four decades after Otto Struve's paper. And the Nobel Prize was awarded to that

Avi Loeb (1:07:20.080)

just a couple of years ago. And then you ask yourself, okay, so science still made progress.

Avi Loeb (1:07:26.080)

What's the problem? The problem is that this baby came out barely, and there was a delay of

Avi Loeb (1:07:33.360)

four decades. So the progress was delayed. And I wonder how many babies were not born because of

Avi Loeb (1:07:39.120)

this resistance. So there must be ideas that are as good as this one that were suppressed because

Avi Loeb (1:07:44.080)

they were bullied, because people ridiculed them, that were actually good ideas. And these are missed

Avi Loeb (1:07:51.920)

opportunities, babies that were never born. And I'm willing to push this frontier of the search

Avi Loeb (1:07:58.560)

for technologies or technological signatures of other civilizations. Because when I was young,

Avi Loeb (1:08:04.000)

I was in the military in Israel. It's obligatory to serve. And there was this saying that one of

Avi Loeb (1:08:10.960)

the soldiers sometimes has to put his body on the barbed wire so that others can go through.

Lex Fridman (1:08:18.560)

And I'm willing to suffer the pain so that younger people in the future will be able to speak freely

Avi Loeb (1:08:25.920)

about the possibility that some of the anomalies we find in the sky are due to technological

Avi Loeb (1:08:30.960)

signatures. And it's quite obvious. This is why I like the folks in artificial intelligence space,

Avi Loeb (1:08:35.840)

Elon Musk and a few others speak about this. And they look at the long arc. They say like,

Avi Loeb (1:08:41.840)

what, you know, this kind of, you know, you can call it like first principles thinking,

Avi Loeb (1:08:46.320)

or you can call it anything really is like, if we just zoom out from our current bickering and our

Avi Loeb (1:08:53.360)

current, like discussions in the what science is doing, look at the long arc of the trajectory

Avi Loeb (1:08:59.280)

we're headed at. Which questions are obviously fundamental to science? And it should be asked,

Lex Fridman (1:09:07.680)

and which is the space of hypothesis we should be exploring? And like exoplanets is a really

Avi Loeb (1:09:12.080)

good example of one that was like an obvious one. I recently talked to Sarah Seager, and it was very

Avi Loeb (1:09:18.320)

taboo when she was starting out to work on an exoplanet. And that was even in the 90s. And like

Avi Loeb (1:09:24.640)

it's obvious should not be a taboo subject. And to me, I mean, I'm probably ignorant, but to me,

Avi Loeb (1:09:30.480)

exoplanets seems like it's ridiculous that that would ever be a taboo subject to not fund,

Avi Loeb (1:09:36.480)

to not explore. That's very, but even for her, it's now taboo to say, like what, you know, to look for

Avi Loeb (1:09:46.320)

industrial pollution, right? Right. And I find that ridiculous. I'll tell you why. She can't take

Avi Loeb (1:09:51.280)

the next step. It's ridiculous for another reason. Not because of just the scientific benefits that

Avi Loeb (1:09:56.800)

we might have by exploring it, but because the public cares about these questions. And the public

Avi Loeb (1:10:03.280)

funds science. So how dare the scientists shy away from addressing these questions,

Avi Loeb (1:10:09.360)

if they have the technology to do it. It's like saying, I don't want to look through

Avi Loeb (1:10:14.880)

Galileo's telescope. It's exactly the same. You have the technology to explore this question,

Lex Fridman (1:10:19.600)

to find the evidence and you shy away from it. You might ask, why do people shy away from it?

Lex Fridman (1:10:25.840)

And perhaps it's because of the fact that there is science fiction. I'm not a fan of science fiction,

Avi Loeb (1:10:30.720)

because it has an element to it that violates the laws of physics in many of the books and the

Avi Loeb (1:10:36.320)

films. And I cannot enjoy these things when I see the laws of physics violated. But who cares that

Avi Loeb (1:10:43.200)

the, you know, the fact that there is science fiction. I mean, if you have the scientific

Avi Loeb (1:10:47.760)

methodology to address the same subject, I don't care that other people, you know, spoke nonsense

Avi Loeb (1:10:53.760)

about this subject or said things that make no sense. Who cares? You do your scientific work,

Avi Loeb (1:10:59.200)

just like you explore the dark matter. You explore the possibility that umuamua is an

Avi Loeb (1:11:05.120)

artifact. You just look for evidence and try to deduce what it means. And I have no problem with

Avi Loeb (1:11:13.920)

doing that. To me, it sounds like any other scientific question that we have. And given

Avi Loeb (1:11:18.000)

the public's interest, we have an obligation to do that. By the way, science to me is not

Avi Loeb (1:11:24.000)

an occupation of the elite. It doesn't allow me to feel superior to other humans that are unable to

Avi Loeb (1:11:29.200)

understand the math. To me, it's a way of life. You know, if there is a problem in the faucet or

Avi Loeb (1:11:35.120)

in the pipe at home, I try to figure out what the problem is. And with a plumber, we figure it out

Lex Fridman (1:11:41.520)

and we look at the clues. And the same thing in science. You look at the evidence, you try to

Avi Loeb (1:11:47.040)

figure out what it means. It's common sense in a way. And it shouldn't be regarded as something

Avi Loeb (1:11:54.720)

removed from the public. It should be a reflection of the public's interest. And I think it's

Avi Loeb (1:11:59.920)

actually a crime to resist the public. If the public says, I care about this, and you say,

Avi Loeb (1:12:05.600)

no, no, no, that's not sophisticated enough for me. I want to do intellectual gymnastics on

Avi Loeb (1:12:09.920)

anti the sitter space. To me, that's a crime. Yes, I 100% agree. So it's hilarious that the very,

Avi Loeb (1:12:18.400)

not hilarious, it's sad, that people who are trained in the scientific community to have the

Avi Loeb (1:12:26.160)

tools to explore this world, to be children, to be the most effective at being children,

Avi Loeb (1:12:31.680)

are the ones that resist being children the most. But there is a large number of people

Avi Loeb (1:12:37.600)

that embrace the childlike wonder about the world and may not necessarily have the tools to do it.

Avi Loeb (1:12:44.880)

That's the more general public. And so, I wonder if I could ask you and talk to you a little bit

Avi Loeb (1:12:51.680)

about UFO sightings. That there's people, quote unquote believers, there's hundreds of thousands

Avi Loeb (1:13:00.960)

of UFO sightings. And I've consumed some of the things that people have said about it. And one

Avi Loeb (1:13:12.320)

thing I really like about it is how excited they are by the possibility. It's almost like this

Avi Loeb (1:13:21.680)

childlike wonder about the world out there. It's not a fear, it's an excitement. Do you think,

Avi Loeb (1:13:28.480)

because we're talking about this possibly extraterrestrial object that visited, that flew

Avi Loeb (1:13:35.680)

by Earth, do you think it's possible that out of those hundreds of thousands of UFO sightings,

Avi Loeb (1:13:43.360)

one is an actual, one or some number is an actual sighting of a nonhuman, some alien technology.

Lex Fridman (1:13:52.560)

And that we're not, we did not, we're too close minded to look and to see.

Avi Loeb (1:14:04.080)

I think to answer this question, we need better evidence. My starting point, as I said,

Avi Loeb (1:14:11.440)

out of modesty is that we are not particularly interesting. And therefore I would be hard pressed

Avi Loeb (1:14:17.920)

to imagine that someone wants to really spy on us. So I would think, as a starting point,

Avi Loeb (1:14:25.040)

that we don't deserve attention and we shouldn't expect someone, but who knows.

Avi Loeb (1:14:30.480)

Now, the problem that I have with UFO sighting reports is that 50 years ago, there were some

Avi Loeb (1:14:37.280)

reports of fuzzy images, saucer like things. By now, our technologies are much better. Our cameras

Avi Loeb (1:14:45.440)

are much more sensitive. These fuzzy images should have turned into crisp, clear images

Avi Loeb (1:14:52.880)

of things that we are confident about. And they haven't turned that way. It's always on the border

Avi Loeb (1:14:58.720)

line of believability. And because of that, I believe that it might be most likely artifacts

Avi Loeb (1:15:04.000)

of our instruments or some natural phenomena that we are unable to understand. Now, of course,

Lex Fridman (1:15:09.600)

the reason you must examine those, if, for example, pilots report about them or

Avi Loeb (1:15:17.040)

the military finds evidence for them, is because it may pose a national security threat. If another

Avi Loeb (1:15:23.120)

country has technologies that we don't know about and they're spying on us, we need to know about

Avi Loeb (1:15:28.320)

it. And therefore we should examine everything that looks unusual. But to associate it with an

Avi Loeb (1:15:33.600)

alien life is a little too far for me until we have evidence that stands up to the level of

Avi Loeb (1:15:43.200)

scientific credence, that we are 100% sure that from multiple detectors and through a scientific

Avi Loeb (1:15:53.120)

process. Now, again, if the scientific community shies away from these reports, we will never have

Avi Loeb (1:15:58.720)

that. It's like saying, I don't want to take photographs of something because I know what it is,

Avi Loeb (1:16:04.960)

then you will never know what it is. But I think if some scientist, if grants, let's put it this

Avi Loeb (1:16:10.560)

way, if funding will be given to scientists to follow on some of these reports and use scientific

Avi Loeb (1:16:17.840)

instruments that are capable of detecting those sightings with much better resolution, with much

Avi Loeb (1:16:24.160)

better information, that would be great because it will clarify the matter. These are not,

Avi Loeb (1:16:29.520)

as you said, hundreds of thousands, these are not once in a lifetime events. So it's possible to

Avi Loeb (1:16:35.520)

take scientific instrumentation and explore, go to the ocean where someone reported that there are

Avi Loeb (1:16:42.480)

frequent events that are unusual and check it out, do a scientific experiment. Why only do experiments

Avi Loeb (1:16:50.720)

deep into the ocean and look at the oceanography or do other things. We can do scientific

Avi Loeb (1:16:57.440)

investigation of these sightings and figure out what they mean. I'm very much in favor of that,

Lex Fridman (1:17:04.480)

but until we have the evidence, I would be doubtful as to what they actually mean.

Avi Loeb (1:17:09.280)

Yeah, we'll have to be humble and acknowledge that we're not that interesting. It's kind of,

Avi Loeb (1:17:14.880)

you're making me realize that because it's so taboo, that the people that have the equipment,

Avi Loeb (1:17:19.040)

uh, meaning, and we're not just talking, everybody has cameras now, but to have a large scale,

Avi Loeb (1:17:25.280)

like a sensor network that collects data that regularly collects, just like we look at the

Avi Loeb (1:17:32.160)

weather, we're collecting information and then we can then access that information when there is

Avi Loeb (1:17:36.560)

reports and like have it not be a taboo thing where there's like millions or billions of dollars

Avi Loeb (1:17:42.080)

or billions of dollars funding this effort that by the way, inspires millions of people.

Avi Loeb (1:17:49.520)

This is exactly what you're talking about. It's like the scientific community is afraid of a

Avi Loeb (1:17:55.200)

topic that inspires millions of people. It's absurd. But if you put blinders on your eyes,

Avi Loeb (1:18:01.200)

you don't see it. Right. I should say that we do have meteors that we see. These are rocks

Avi Loeb (1:18:08.080)

that by chance happen to collide with the earth and they, if they're small, they burn up in the

Avi Loeb (1:18:14.240)

atmosphere. But if they're big enough, tens of meters or more, hundreds of meters, the outer

Avi Loeb (1:18:21.760)

layer burns up, but then the core of the object makes it through. And this is our chance of putting

Avi Loeb (1:18:29.040)

our hands around an object if this meteor came from interstellar space. So one path of discovery

Avi Loeb (1:18:37.440)

is to search for interstellar meteors. And with a student of mine, we actually looked through the

Avi Loeb (1:18:43.520)

record and we thought that we found one example of a meteor that was reported that might have come

Avi Loeb (1:18:50.000)

from interstellar space. And then another approach is, for example, to look at the moon. The moon is

Avi Loeb (1:18:57.040)

different from the earth in the sense that it doesn't have an atmosphere. So objects do not

Avi Loeb (1:19:02.080)

burn up on their way to it. It's sort of like a museum. It collects everything. Of rocks from out

Avi Loeb (1:19:07.600)

there in deep space. Yeah. And there is no geological activity on the moon. So on earth,

Avi Loeb (1:19:12.560)

every hundred million years, you know, we could have had computer terminals on earth that could

Avi Loeb (1:19:17.520)

have been a civilization like ours with electronic equipment. Yes. More than a hundred million years

Avi Loeb (1:19:23.200)

ago. And it's completely lost. You cannot excavate and find it, evidence for it, because in

Avi Loeb (1:19:29.200)

archaeological digs, because the earth is being mixed on these timescales. And everything that

Avi Loeb (1:19:35.120)

was on the surface more than a hundred million years ago is buried deep inside the earth right

Avi Loeb (1:19:39.760)

now because of geological activity. Fascinating to think about, by the way. Yeah. But on the moon,

Avi Loeb (1:19:44.400)

this doesn't happen. The only thing that happens on the moon is you have objects impacting the moon

Lex Fridman (1:19:49.600)

and they go 10 meters deep. So they produce some dust, but the moon keeps everything. It's like a

Avi Loeb (1:19:55.280)

museum. It keeps everything on the surface. So if we go to the moon, I would highly recommend

Avi Loeb (1:20:01.440)

regarding it as an archaeological site. Yes. And looking for objects that are strange. Maybe it

Avi Loeb (1:20:07.920)

collected some trash, you know, from interstellar space. If we could just linger on the Drake

Avi Loeb (1:20:13.280)

equation for a little bit. We kind of talked about there's a lot of uncertainty in the parameters

Lex Fridman (1:20:18.720)

and the Drake equation itself is very limited. But I think the parameters are interesting in

Avi Loeb (1:20:26.320)

themselves, even if it's limited, because I think each one is within the reach of science,

Avi Loeb (1:20:31.120)

right? Did you get the evidence for it? I mean, a few I find really interesting,

Avi Loeb (1:20:36.400)

could be interesting to get your comment on. So the one with the most variance, I would say,

Avi Loeb (1:20:43.440)

from my perspective, is the length that civilizations last. However you define it. In the Drake

Avi Loeb (1:20:48.800)

equation, it's the length of how long you're communicating. Yeah, transmitting.

Avi Loeb (1:20:52.960)

Transmitting. Just like you said, that's a wrong way to think about it, because we can be detecting

Avi Loeb (1:20:59.120)

some other outputs of the civilizations, etc. But if we just define broadly how long those

Avi Loeb (1:21:04.240)

civilizations last, do you have a sense of how long they might last? Like what are the great

Avi Loeb (1:21:12.160)

filters that might destroy civilizations that we should be thinking about? And how can

Avi Loeb (1:21:19.360)

science give us more hints on this topic? So I, as I mentioned before, operate by the

Avi Loeb (1:21:25.120)

Copernican principle, meaning that we are not special. We don't live in a special place

Lex Fridman (1:21:31.200)

and not in a special time. And by the way, it's just modesty encapsulated in scientific terms,

Avi Loeb (1:21:38.480)

right? You're saying, I'm not special, you know, I find conditions here, they exist

Avi Loeb (1:21:43.040)

everywhere. So if you adopt the Copernican principle, you basically say, our civilization

Avi Loeb (1:21:50.720)

transmitted radio signals for a hundred years, roughly, so probably it would last another

Avi Loeb (1:21:57.920)

hundred or a few hundred and that's it. Because we don't live at a special time.

Lex Fridman (1:22:02.160)

So that's, you know, well, of course, if we get our act together and we somehow start

Avi Loeb (1:22:10.480)

to cooperate rather than fighting each other, killing each other, you know, wasting a lot

Avi Loeb (1:22:15.760)

of resources on things that would destroy our planet, maybe we can lengthen that period

Avi Loeb (1:22:23.520)

if we get smarter. But the most natural assumption is to say that we will live into the future as

Avi Loeb (1:22:31.040)

much as we lived from the time that we start to develop the means for our own destruction,

Avi Loeb (1:22:35.840)

the technologies we have, which is quite pessimistic, I must say. So several centuries,

Avi Loeb (1:22:40.960)

that's what I would give, unless we get our act, unless we become more intelligent

Avi Loeb (1:22:45.680)

than the newspapers report every day. Okay. Point number one. Second, and by the way,

Avi Loeb (1:22:51.920)

this is relevant, I should say, because there was a report about perhaps a radio signal detected

Avi Loeb (1:22:58.480)

from Proxima Centauri. What do you make of that signal? Oh, I think it's some Australian guy with

Avi Loeb (1:23:03.520)

a cell phone next to the observatory or something like that, because it was the Parkes Telescope in

Avi Loeb (1:23:09.200)

Australia. Okay. So it's human created noise. Yeah. Which is always the worry because actually

Avi Loeb (1:23:17.120)

the same observatory, the Parkes Observatory, detected a couple of years ago some signal

Lex Fridman (1:23:22.480)

and then they realized that it comes back at lunchtime. Yes. And they said, okay, what could

Avi Loeb (1:23:29.600)

it be? And then they figured out that it must be the microwave oven in the observatory because

Avi Loeb (1:23:34.000)

someone was opening it before it finished and it was creating this radio signal that they detected

Avi Loeb (1:23:40.000)

with a telescope every lunchtime. So just a cautionary remark. But the reason I think it's

Avi Loeb (1:23:47.680)

human made, without getting to the technical details, is because of this very short window

Avi Loeb (1:23:54.000)

by which we were transmitting radio signals out of the lifetime of the Earth. As I said,

Avi Loeb (1:23:58.480)

100 years out of four and a half billion years that the Earth existed. So what's the chance

Avi Loeb (1:24:04.320)

that another civilization, a twin civilization of ours, is transmitting radio signals exactly

Avi Loeb (1:24:10.080)

at the time that we are looking with our radio telescopes? 10 to the minus 7. And the other

Avi Loeb (1:24:19.120)

argument I have is that they detected it in a very narrow band of frequencies and that makes it

Avi Loeb (1:24:28.080)

cannot be through natural processes, very narrow band, just like some radio transmissions that we

Avi Loeb (1:24:34.880)

produce. But if it were to come from the habitable zone, from a transmitter on the surface of Proxima

Avi Loeb (1:24:42.880)

b, this is the planet that orbits Proxima Centauri, then I calculated that the frequency

Avi Loeb (1:24:48.720)

would drift through the Doppler effect. Just like when you hear a siren on the street, when the car

Avi Loeb (1:24:56.560)

approaches you, it has a different pitch than when it recedes away from you, that's the Doppler

Avi Loeb (1:25:02.000)

effect. And when the planet orbits the star, Proxima Centauri, you would see or detect a

Avi Loeb (1:25:10.160)

different frequency when the planet approaches us as compared to when it recedes. So there should

Avi Loeb (1:25:14.720)

be a frequency drift just because of the motion of the planet. And I calculated that it must be

Avi Loeb (1:25:22.800)

much bigger than observed. So it cannot just be a transmitter sitting on the planet and sending in

Avi Loeb (1:25:29.840)

our direction a radio signal unless they want to cancel the Doppler effect. But then they need to

Avi Loeb (1:25:36.560)

know about us because in a different direction, it will not be cancelled. Only in our direction,

Avi Loeb (1:25:40.720)

they can cancel it perfectly. So there is this direction of Proxima Centauri, but I have a

Avi Loeb (1:25:48.480)

problem imagining a transmitter on the surface of a planet in the habitable zone emitting it.

Lex Fridman (1:25:53.840)

But my main issue is really with the likelihood, given what we know about ourselves.

Lex Fridman (1:26:01.600)

Right. In terms of the duration of the civilization.

Avi Loeb (1:26:03.760)

The Copernican principle. Yeah.

Lex Fridman (1:26:06.880)

So nevertheless, this particular signal is likely to be a human interference, perhaps. But

Lex Fridman (1:26:12.400)

do you find Proxima be interesting? Or the more general question is, do you think we humans

Lex Fridman (1:26:19.840)

will venture out into outside our solar system and potentially colonize other habitable planets?

Avi Loeb (1:26:30.240)

Actually, I am involved in a project whose goal is to develop the technology that would allow us

Avi Loeb (1:26:35.600)

to leave the solar system and visit the nearest stars. And that is called the Star Shot. In 2015,

Avi Loeb (1:26:43.440)

May 2015, an entrepreneur from Silicon Valley, Yuri Milner, came to my office at Harvard and said,

Avi Loeb (1:26:51.680)

would you be interested in leading a project that would do that in our lifetime? Because as we

Avi Loeb (1:26:58.560)

discussed before, to traverse those distances with existing rockets would take tens of thousands of

Avi Loeb (1:27:05.040)

years. And that's too long. For example, to get to Proxima Centauri with the kind of

Avi Loeb (1:27:13.840)

spacecrafts that we already sent, like New Horizons or Voyager 1, Voyager 2, you needed to

Avi Loeb (1:27:22.480)

send them when the first humans left Africa, so that they would arrive there now. And that's a

Avi Loeb (1:27:29.840)

long time to wait. So Yuri wanted to do it within a lifetime, 10, 20 years, meaning it has to move

Avi Loeb (1:27:36.720)

at a fraction of the speed of light. So can we send a spacecraft that would be moving at the

Avi Loeb (1:27:42.000)

fraction of the speed of light? And I said, let me look into that for six months. And with my

Avi Loeb (1:27:47.440)

students and postdocs, we arrived to the conclusion that the only technology that can do that is the

Avi Loeb (1:27:52.880)

light sail technology, where you basically produce a very powerful laser beam on Earth. So you can

Avi Loeb (1:28:01.760)

collect sunlight with photovoltaic cells or whatever and then convert it into stored energy

Lex Fridman (1:28:13.120)

and then produce a very powerful laser beam that is 100 gigawatts and focus it on a sail in space

Avi Loeb (1:28:22.720)

that is roughly the size of a person, a couple of meters or a few meters, that weighs only a gram

Avi Loeb (1:28:30.880)

or a few grams, very thin. And through the math, you can show that you can propel such a sail,

Avi Loeb (1:28:39.120)

if you shine on it for a few minutes, it will traverse the distance that is five times the

Avi Loeb (1:28:43.600)

distance to the moon, and it will get to a fifth of the speed of light. Sounds crazy. But I've

Avi Loeb (1:28:49.600)

talked to a bunch of people and they're like, I know it sounds crazy, but it's actually,

Avi Loeb (1:28:54.480)

it will work. This is one of those, it's beautiful. I mean, this is science.

Lex Fridman (1:28:59.840)

And the point is, people didn't get excited about space since the Apollo era. And it's about time,

Avi Loeb (1:29:08.960)

you know, for us to go into space. A couple of months ago, I was asked to participate in a debate

Avi Loeb (1:29:15.280)

organized by IBM and Bloomberg News. And the discussion centered on the question,

Avi Loeb (1:29:22.160)

is the space race between the US and China good for humanity? Oh, interesting. And all the other

Avi Loeb (1:29:28.080)

debaters were worried about the military threats. And I just couldn't understand what they're

Lex Fridman (1:29:35.360)

talking about, because military threats come from hovering above the surface of the Earth, right?

Lex Fridman (1:29:41.760)

And we live on a two dimensional surface, we live on the surface of the Earth. But space is

Avi Loeb (1:29:47.200)

all about the third dimension, getting far from Earth. So if you go to Mars, or you go to a star,

Avi Loeb (1:29:52.880)

another star, there is no military threat. What are we talking about? Space is all about,

Avi Loeb (1:29:58.960)

you know, feeling that, you know, we are one civilization, in fact, not fighting each other,

Avi Loeb (1:30:04.560)

just going far, and having aspirations for something that goes beyond military threats.

Lex Fridman (1:30:10.160)

So why would we be worried that the space race will lead?

Avi Loeb (1:30:14.480)

That's actually brilliant. I didn't, you know, there's something in our discourse about it,

Avi Loeb (1:30:18.960)

the space race is sometimes made synonymous with like the Cold War or something like that.

Lex Fridman (1:30:23.680)

Right.

Avi Loeb (1:30:24.080)

Or with wars. But really, yeah, there was a lot of ego tied up in that. I remember,

Lex Fridman (1:30:28.880)

I mean, it's still to this day, there's a lot of pride that Russians,

Avi Loeb (1:30:32.880)

Soviet Union was the first to space. And there's a lot of pride in the American side that was the

Avi Loeb (1:30:36.880)

first on the moon. But yeah, you're exactly right. Like, there's no aggression, there's no wars.

Lex Fridman (1:30:42.160)

And beyond that, if you think about the global economy, right now, there is a commercial

Avi Loeb (1:30:47.360)

interest. That's why Jeff Bezos and Elon Musk are interested about, you know, Mars and so on.

Avi Loeb (1:30:52.640)

There is a commercial interest, which is international. It's driven by money,

Avi Loeb (1:30:57.040)

not by pride. And, you know, nations can sign treaties. First of all, there are lots of treaties

Avi Loeb (1:31:04.320)

that were signed even before the First World War and the Second World War and the World War took

Avi Loeb (1:31:08.560)

place. So who cares, you know, like humans, treaties do not safeguard anything, you know.

Lex Fridman (1:31:15.360)

But beyond that, even if nations sign treaties about space exploration, you might still find

Avi Loeb (1:31:21.440)

commercial entities that will find a way to get their launches. And, you know, so I think we

Avi Loeb (1:31:27.760)

should rethink space. It has nothing to do with national pride. Once again, nothing to do with

Avi Loeb (1:31:33.360)

our egos. It's about exploration. And the biggest problem, I think, in human history is that humans

Avi Loeb (1:31:42.720)

tend to think about egos and about their own personal image rather than, look at the big

Avi Loeb (1:31:53.280)

picture, you know. We will not be around for long. We are just occupying a small space right now.

Avi Loeb (1:31:58.800)

Now, let's move out of this, you know, the way that Oscar Wilde said, I think is the best. He said,

Lex Fridman (1:32:06.160)

all of us are in the gutters, but some of us are looking at the stars.

Avi Loeb (1:32:11.760)

Yeah, and the more of us are looking at the stars, the likelier we are to, for this thing,

Avi Loeb (1:32:18.480)

this little experiment we have going on to last a while as opposed to end too quickly. I mean,

Avi Loeb (1:32:25.280)

it's not just about science of being humble. It's about the survival of the human species

Lex Fridman (1:32:29.920)

as being humble. To me, it's incredibly inspiring, the Starshot project of,

Avi Loeb (1:32:36.720)

I mean, there's something magical about being able to go to another habitable planet and take

Avi Loeb (1:32:41.840)

a picture even. I mean, within our lifetime, I mean, that, with crazy technology too, which is...

Avi Loeb (1:32:49.680)

I should tell you how it was conceived. So, I was at the time, so after six months passed,

Avi Loeb (1:32:56.560)

after the visit of Yuri Miller, I was, usually I go in December during the winter break,

Avi Loeb (1:33:02.880)

I go to Israel. I used to go to see my family and I get a phone call just before the weekend

Avi Loeb (1:33:11.280)

started. I get a phone call, Yuri would like you to present your concept in two weeks at his home.

Lex Fridman (1:33:19.440)

And I said, well, thank you for letting me know because I'm actually out of the door of the hotel

Avi Loeb (1:33:25.280)

to go to a goat farm in the Negev, in the southern part of Israel, because my wife wanted to have

Avi Loeb (1:33:34.640)

to go to a place that is removed from civilization, so to speak.

Avi Loeb (1:33:39.040)

So, we went to that goat farm and I need to make the presentation and there was no internet

Avi Loeb (1:33:47.120)

connectivity except in the office of the goat farm. So, the following morning at 6am, I sit

Avi Loeb (1:33:53.520)

with my back to the office of that goat farm, looking at goats that were newly born and typing

Avi Loeb (1:34:00.800)

into my laptop, the presentation, the PowerPoint presentation about our ambitions for visiting the

Lex Fridman (1:34:06.880)

nearest star. And that was very surreal to me. Like our origins in many ways,

Avi Loeb (1:34:16.560)

this very primitive origins and our dreams of looking out that is brilliant. So that is

Avi Loeb (1:34:23.280)

incredibly inspiring to me, but it's also inspiring of putting humans onto other

Avi Loeb (1:34:32.960)

moons or planets. I still find going to the moon really exciting. I don't know, maybe I'm just a

Avi Loeb (1:34:38.240)

sucker for it, but it's really exciting. And Mars, which is a new place, a new planet, another planet

Avi Loeb (1:34:44.960)

that might have life. I mean, there's something magical to that or some traces of previous life.

Avi Loeb (1:34:49.840)

You might think that humans cannot really survive and there are risks by going there. But my point

Avi Loeb (1:34:55.680)

is, we started from Africa and we got to apartment buildings in Manhattan, right? It's a very

Avi Loeb (1:35:03.840)

different environment from the jungles to live in an apartment building in a small cubicle.

Avi Loeb (1:35:09.120)

Yes. And it took tens of thousands of years,

Lex Fridman (1:35:13.440)

but humans adapted, right? So why couldn't humans also make the leap and adapt to a habitat in

Avi Loeb (1:35:20.240)

space? Now you can build a platform that would look like an apartment building in the Bronx

Avi Loeb (1:35:26.800)

or somewhere, but have inside of it everything that humans need. And just like the space station,

Lex Fridman (1:35:34.320)

but bigger. And it will be a platform in space. And the advantage of that is if something bad

Avi Loeb (1:35:40.400)

happens on Earth, you have that complex where humans live. And you can also move it back and

Avi Loeb (1:35:47.360)

forth depending on how bright the sun gets. Because within a billion years, the sun would be

Avi Loeb (1:35:56.080)

too hot and it will boil off all the oceans on Earth. So we cannot stay here for more than a

Avi Loeb (1:36:01.520)

billion years. That's for sure. Yes. So that's a billion years from now. I prefer shorter term

Avi Loeb (1:36:07.920)

deadlines. And so there's a lot of threats that we're facing currently. Do you find it exciting

Avi Loeb (1:36:13.840)

the possibility of landing on Mars and starting little like building a Manhattan style apartment

Avi Loeb (1:36:22.880)

building on Mars and humans occupying it? Do you think from a scientific or an engineering

Avi Loeb (1:36:27.920)

perspective, that's a worthy pursuit? I think it's worthy. But the real issue that is often

Avi Loeb (1:36:35.920)

underplayed is the risk to the human body from cosmic rays. These are energetic particles

Lex Fridman (1:36:43.520)

and we are protected from them by the magnetic field around the Earth that blocks them. But if

Avi Loeb (1:36:51.040)

you go to Mars, where there is no such magnetic field to block them, then, you know, a significant

Avi Loeb (1:36:57.680)

fraction of the brain cells in your head will be damaged within a year. And the consequences of

Avi Loeb (1:37:04.480)

that are not clear. I mean, it's quite possible that humans cannot really survive on the surface.

Avi Loeb (1:37:12.560)

Now, it may mean that we need to dig tunnels, go underground or create some protection.

Avi Loeb (1:37:19.440)

This is something that can be engineered. Yes. And, you know, we can start from the

Avi Loeb (1:37:23.760)

Moon and then move to Mars. That would be a natural progression. But it's a big issue

Avi Loeb (1:37:29.600)

that needs to be dealt with. I don't think, you know, it's a showstopper. I think we can overcome

Avi Loeb (1:37:35.360)

it. But, you know, just like anything in science and technology, you have to work on it for a while,

Avi Loeb (1:37:40.080)

figure out solutions. But it's not as rosy as Elon Musk talks about. I mean, Elon Musk can

Avi Loeb (1:37:47.200)

obviously be optimistic. I think eventually it will boil down to figuring out how to cope with

Avi Loeb (1:37:53.360)

this risk, the health risk. Yeah, I mean, in defense of optimism, I find that there's at

Avi Loeb (1:37:59.920)

least a correlation, if not their best friends, is optimism and open mindedness. It's a necessary

Avi Loeb (1:38:10.400)

precondition to try crazy things. And in that sense, the sense I have about going to Mars,

Avi Loeb (1:38:18.880)

if we use today's logic of what kind of benefits we'll get from that, we're never going to go.

Lex Fridman (1:38:28.080)

And like most decisions we make in life, most decisions we've made as a human species

Avi Loeb (1:38:34.240)

are irrational if you look at just today. But if you look at the long arc and the

Avi Loeb (1:38:41.680)

possibilities that it might bring, just like humans, Europe and destroyed everybody.

Lex Fridman (1:38:51.120)

But it was a commercial interest that drove that for trade. And, you know, it might happen again,

Avi Loeb (1:38:58.000)

in this context, you have people like Jeff Bezos and Elon Musk that are commercially driven to go

Avi Loeb (1:39:02.640)

to space. But it doesn't mean that what we will ultimately find is not new worlds that have

Avi Loeb (1:39:10.160)

nothing, you know, have much more to offer than just commercial interest. And as a side effect,

Avi Loeb (1:39:16.960)

almost. Yeah, yeah. And then that's why I think, you know, we should be open minded and explore.

Avi Loeb (1:39:22.800)

And, however, at the same time, because of the reasons you pointed out, I'm not optimistic that

Avi Loeb (1:39:28.960)

we will survive more than a few centuries into the future, because people do not think long term.

Lex Fridman (1:39:34.240)

And that means that we will only survive for the short term. I don't know if you have thoughts

Avi Loeb (1:39:39.600)

about this, but what are the things that worry you the most about, from the great perspective

Avi Loeb (1:39:45.360)

of the universe, which is the great filters that destroys intelligent civilizations,

Lex Fridman (1:39:49.840)

but for our own species here? Like, what are the things that worry you the most?

Avi Loeb (1:39:55.440)

Yeah, the thing that worries me the most is that people pay attention to how many likes they have

Avi Loeb (1:39:59.920)

on Twitter. And rather than, you know, basketball coaches tell the team players, keep your eyes on

Avi Loeb (1:40:10.160)

the ball, not on the audience. The problem is we keep our eyes on the audience most of the time.

Avi Loeb (1:40:17.120)

Let's keep our eyes on the ball. And what does that mean? First of all, in the context of science,

Lex Fridman (1:40:21.600)

it means pay attention to the evidence. When the evidence looks strange,

Avi Loeb (1:40:26.000)

then we should figure it out. You know, I went to a seminar about Umuamua at Harvard,

Lex Fridman (1:40:32.320)

and a colleague of mine that is mainstream, conservative, would never say anything that would

Avi Loeb (1:40:40.880)

deviate from what everyone else is thinking, said to me after the seminar, I wish this object never

Avi Loeb (1:40:48.400)

existed. Now, to me, I mean, I just couldn't hear that. What do you mean, nature is whatever it is,

Avi Loeb (1:40:56.240)

you have to pay attention to it. You cannot say, you know, you cannot bury your head in this. I

Avi Loeb (1:41:01.680)

mean, you should bless nature for giving you clues about things that you haven't expected.

Avi Loeb (1:41:05.840)

Yes.

Lex Fridman (1:41:06.400)

And I think that's the biggest fault that we are looking for confirmations of things we already

Avi Loeb (1:41:12.800)

know, so that we can maintain our pride that we already knew it, and maintain our image,

Avi Loeb (1:41:20.800)

not make mistakes, because we already knew it, therefore we expected the right thing.

Avi Loeb (1:41:25.120)

Yes.

Lex Fridman (1:41:25.600)

But science is a learning experience, and sometimes you're wrong. And let's learn from

Avi Loeb (1:41:30.800)

those mistakes. And what's the problem about that? Why do we have to get, you know, prizes,

Lex Fridman (1:41:36.480)

and why do we get to be honored and maintain our image, when the actual objective of science is

Lex Fridman (1:41:42.320)

learning about nature?

Lex Fridman (1:41:43.600)

And like you've talked about, anomalies in this case are actually are not things that

Avi Loeb (1:41:49.520)

are unfortunate and to be ignored are, in fact, gifts and should be the focus of science.

Avi Loeb (1:41:54.960)

Exactly, because that's the way for us to improve our understanding. If you look at quantum

Avi Loeb (1:41:59.200)

mechanics, nobody dreamed about it. And it was revolutionary, and we still don't fully understand

Lex Fridman (1:42:05.200)

it. It's a pain for us to figure out.

Lex Fridman (1:42:07.680)

So I understand from the perspective that's holding our science back, why do you have

Avi Loeb (1:42:13.760)

a sense that that's also something that might be a problem for us in terms of the survival

Lex Fridman (1:42:20.960)

of human civilization?

Avi Loeb (1:42:22.160)

Because when you look at society, it operates by the same principles. People look for affirmation

Avi Loeb (1:42:31.120)

by groups, and they, you know, people segregate into herds that think like them, especially

Avi Loeb (1:42:39.280)

these days when social media is so strong, you can find your support group. And if you

Avi Loeb (1:42:44.880)

don't look for evidence for what you're saying, you can say crazy things as long as there

Avi Loeb (1:42:49.360)

are enough people supporting what you say. You can even have your newspapers, you can

Avi Loeb (1:42:54.560)

have everything to support your view, and then, you know, bad things will happen to

Avi Loeb (1:42:59.360)

society. Because we're detaching ourselves from reality. And if we detach ourselves

Avi Loeb (1:43:04.480)

from reality, all the destructive things that naturally can occur in the real world, whether

Avi Loeb (1:43:09.120)

from nuclear weapons, all the kinds of threats that we're facing, even we're living through

Avi Loeb (1:43:13.840)

a pandemic, the supposed, you know, a much, much worse pandemic could happen. And then

Avi Loeb (1:43:19.840)

we could sadly, like we did this one, politicize it in some kind of way and have bickering

Avi Loeb (1:43:25.600)

in the space of Twitter and politics, as opposed to there's an actual thing that can destroy

Lex Fridman (1:43:31.040)

the human species.

Avi Loeb (1:43:32.000)

Exactly. So the only way for us to maintain, to stay modest and learn about what really

Avi Loeb (1:43:37.600)

happens is by looking for evidence. Again, I'm saying, it's not about ourself, you know,

Avi Loeb (1:43:44.480)

it's about figuring out what's around us. And if you close yourself by surrounding yourself

Avi Loeb (1:43:49.360)

with people that are like minded, that refuse to look at the evidence, you can do bad things.

Lex Fridman (1:43:57.040)

And throughout human history, that's the origin of all the bad things that happen.

Lex Fridman (1:44:02.800)

Yes.

Lex Fridman (1:44:03.280)

And I think it's a key. It's a key to be modest and to look at evidence. And it's

Avi Loeb (1:44:07.920)

not a nuance. Now, you might say, Oh, okay, the uneducated person might operate. No,

Avi Loeb (1:44:15.360)

it's the scientific community operates this way. My problem is not with people that don't

Lex Fridman (1:44:21.040)

have an academic pedigree. It's included everywhere in society.

Avi Loeb (1:44:24.960)

On the topic of the discovery of evidence of alien civilizations, which is something

Avi Loeb (1:44:30.880)

you touch on in your book, what that idea would do to societies, to the human psyche

Lex Fridman (1:44:38.960)

and in general, do you think, and you talk about the, I still have trouble pronouncing,

Lex Fridman (1:44:46.400)

but a Muamua wager, right? What do you think is, can you explain it? And what do you think

Lex Fridman (1:44:54.320)

in general is the effect that such knowledge might have on human civilization?

Avi Loeb (1:44:58.640)

Right. So Pascal had this wager about God. And by the way, there are interesting connections

Avi Loeb (1:45:04.400)

between theology and the search for extraterrestrial life. It's possible that we were planted on

Avi Loeb (1:45:11.040)

this planet by another civilization. We attribute to God powers that belong really to the technological

Avi Loeb (1:45:19.040)

civilization. But putting that aside, Pascal basically said, there are two possibilities,

Avi Loeb (1:45:26.800)

there are two possibilities, either God exists or not. And if God exists, the consequences

Avi Loeb (1:45:34.560)

are quite significant. And therefore, we should consider that possibility differently than

Avi Loeb (1:45:42.640)

equal weight to both possibilities. And I suggest that we do the same with Muamua or

Avi Loeb (1:45:50.400)

other technological signatures, that we keep in mind the consequences and therefore pay

Avi Loeb (1:45:58.960)

more attention to that possibility. Now, some people say extraordinary claims require extraordinary

Avi Loeb (1:46:05.600)

evidence. My point is that the term extraordinary is really subjective. For one person, a black hole

Avi Loeb (1:46:14.720)

is extraordinary. For another, it's just a consequence of Einstein's theory of gravity. It's

Avi Loeb (1:46:20.640)

nothing extraordinary. The same about the type of dark matter, anything. So we should leave the

Avi Loeb (1:46:27.680)

extraordinary part of that sentence. Just keep evidence, okay? So let's be guided by evidence.

Lex Fridman (1:46:35.520)

And even if we have extraordinary claims, let's not dismiss them because the evidence is not

Avi Loeb (1:46:42.080)

extraordinary enough. Because if we have an image of something and it looks really strange and we

Avi Loeb (1:46:47.360)

say, oh, the image is not sufficiently sharp, therefore, we should not even pay attention to

Avi Loeb (1:46:51.920)

this image or not even consider. I think that's a mistake. What we should do is say, look, there is

Avi Loeb (1:46:57.520)

some evidence for something unusual. Let's try and build instruments that will give us a better

Avi Loeb (1:47:02.800)

image. And if you just dismiss extraordinary claims, because you consider them extraordinary,

Avi Loeb (1:47:09.680)

you avoid discovering things that you haven't expected. And so I believe that along the history

Avi Loeb (1:47:17.520)

of astronomy, there are many missed opportunities. And I speak about astronomy, but I'm sure in other

Avi Loeb (1:47:21.920)

fields, it's also true. I mean, this is my expertise. For example, you know, the Astrophysical

Avi Loeb (1:47:27.360)

Journal, which is the main primary publication in astrophysics. If you go before the 1980s,

Avi Loeb (1:47:35.600)

there are images that were posted in the Astrophysical Journal of giant arcs, you know, arcs

Avi Loeb (1:47:41.520)

of light surrounding clusters of galaxies. And, you know, you can find it in printed versions of

Avi Loeb (1:47:49.680)

the Astrophysical Journal. People just ignore it. They put the image, they see the arc, they say,

Avi Loeb (1:47:54.960)

who knows what it is and just ignore it. And then in the 1980s, the subject of gravitational

Avi Loeb (1:48:00.960)

lensing became popular. And the idea is that you can deflect light by the force of gravity. And

Avi Loeb (1:48:11.200)

then you can put a source behind the cluster of galaxies, and then you will get these arcs. And

Avi Loeb (1:48:16.160)

actually, Einstein predicted it in 1940. And, you know, so these things were expected, but

Avi Loeb (1:48:23.760)

people just had them in the images, didn't pay attention. So I'm sure there are lost opportunities

Avi Loeb (1:48:28.320)

sometimes. Even in existing data, you have things that are unusual and exceptional and are not being

Avi Loeb (1:48:36.160)

addressed. Yeah, you actually, I think you have an article, the data is not enough from quite a few

Avi Loeb (1:48:42.560)

years ago, where you talk, you know, we can go back to the 70s and 80s, but we can go also to the

Avi Loeb (1:48:48.240)

Mayan civilization. Right, the Mayan civilization basically believed in astrology that you can

Avi Loeb (1:48:53.680)

forecast the outcome of a war based on the position of the planets. And they had, you know,

Avi Loeb (1:49:00.240)

astronomers in their culture had the highest social status. They were priests, they were elevated.

Lex Fridman (1:49:08.240)

And the reason was that they helped politicians decide when to go to war, because they would tell

Avi Loeb (1:49:14.080)

the politicians, you know, the planets would be in this configuration, it's a better chance for you

Avi Loeb (1:49:18.560)

to win the war, go to war. And in retrospect, they collected wonderful data, but misinterpreted it,

Avi Loeb (1:49:27.120)

because we now know that the position of Venus or Jupiter or whatever has nothing to do with the

Avi Loeb (1:49:33.520)

outcome of World War I, World War II, you know, has nothing to do. And so we can have a prejudice

Lex Fridman (1:49:40.480)

and collect data without actually doing the right thing with it. That's such a Pisces thing to say.

Avi Loeb (1:49:47.200)

I looked up what your astrological sign is.

Avi Loeb (1:49:52.880)

Well, so you mentioned Einstein predicted that black holes don't exist, or just didn't, or thought.

Avi Loeb (1:49:58.560)

Don't exist in nature.

Lex Fridman (1:49:59.520)

Don't exist in nature.

Avi Loeb (1:50:00.880)

When Einstein came up with his theory of gravity in 1915, November 1915, a few months later,

Avi Loeb (1:50:07.520)

another physicist, Karl Schwarzschild, he was the director of the Potsdam Observatory,

Lex Fridman (1:50:13.120)

but he was a patriot, a German patriot. So he went into the First World War fighting for Germany.

Lex Fridman (1:50:18.800)

But while he was at the front, he sent a postcard to Einstein saying, you know,

Avi Loeb (1:50:23.600)

a few months after the theory was developed, saying, actually, I found a solution to your

Avi Loeb (1:50:27.360)

equations. And that was a black hole solution. And then he died a few months later. And Einstein

Avi Loeb (1:50:34.480)

was a pacifist, and he survived. So the lesson from this story is that if you want to work out

Avi Loeb (1:50:40.080)

the consequences of a theory, you better be a pacifist. But the point is that this solution

Avi Loeb (1:50:47.840)

was known shortly after Einstein came up with his theory. But in 1939, Einstein wrote a paper

Lex Fridman (1:50:55.920)

in the Annals of Mathematics saying, even though the solution exists,

Avi Loeb (1:51:00.000)

I don't think it's realized in nature. And his argument was, if you imagine a star collapsing,

Avi Loeb (1:51:05.760)

stars often spin, and the spin will prevent them from making a black hole, collapsing to a point.

Avi Loeb (1:51:11.280)

So, I mean, can you maybe, one of the many things you have worked on, you're an expert in,

Lex Fridman (1:51:20.000)

is black holes. Can you first say, what are black holes? And second, how do we know that they exist?

Avi Loeb (1:51:26.560)

Right. So black holes are the ultimate prison. You know, you can check in, but you can never check out.

Lex Fridman (1:51:32.800)

It's romantic.

Avi Loeb (1:51:33.360)

You can never check out. Even light cannot escape from them. So there are extreme structures of

Avi Loeb (1:51:40.000)

space and time. And there is this so called Schwarzschild radius or the event horizon of

Avi Loeb (1:51:48.640)

a black hole. Once you enter into it with a spaceship, you would never be able to tweet

Avi Loeb (1:51:54.160)

back to your friends and tell them, by the way, I asked the students in my class, freshman seminar

Avi Loeb (1:51:59.360)

at Harvard, I said, let me give you two possible journeys that you can take. I said, suppose aliens

Avi Loeb (1:52:06.800)

come to Earth and suggest that you would board their spaceship, would you do it? And the second

Lex Fridman (1:52:15.280)

is, suppose you could board a spaceship that will take you into a black hole, would you do it?

Lex Fridman (1:52:20.000)

So all of them said to the first question, yes, under one condition, that I'll be able to maintain

Avi Loeb (1:52:28.080)

my social media contacts and report back, share the experience with them. Personally, I have no

Lex Fridman (1:52:34.960)

footprint on social media.

Avi Loeb (1:52:36.240)

Yeah, which is as a matter of principle.

Lex Fridman (1:52:39.040)

Yeah, my wife asked me when we got married, and I honor that.

Lex Fridman (1:52:44.560)

And I told you offline, I need to get married to such a woman. She truly is a special agent.

Avi Loeb (1:52:49.280)

Well, she was wise enough to recognize the risk. But it saves me time. And it also keeps me away

Avi Loeb (1:52:56.480)

from crowds. I don't have the notion of what a lot of other people think, so I can think

Lex Fridman (1:53:03.600)

independently.

Avi Loeb (1:53:04.080)

Crowd think, exactly.

Avi Loeb (1:53:04.720)

Yeah, exactly. So I was surprised to hear that for students, it's extremely important to share

Avi Loeb (1:53:11.840)

experiences. Even if they go on a spaceship with aliens, they still want to brag about it rather

Lex Fridman (1:53:17.600)

than look around and see what's going on.

Avi Loeb (1:53:19.680)

This is not an option when you go to the black hole, is exactly the point.

Lex Fridman (1:53:22.960)

So for the black hole, they said no, because obviously you can find your death after you get

Avi Loeb (1:53:29.680)

into it, you crash into singularity. There is this singularity in the center. So inside the event

Avi Loeb (1:53:35.680)

horizon, we know that all the matter collects at a point. Now, we can't really predict what happens

Avi Loeb (1:53:44.560)

at the singularity because Einstein's theory breaks down. And we know why it breaks down,

Avi Loeb (1:53:49.680)

because it doesn't have quantum mechanics that talks about small distances. We don't have a

Avi Loeb (1:53:55.280)

theory that unifies quantum mechanics and gravity so that it will predict what happens near a

Avi Loeb (1:54:02.240)

singularity. And in fact, a couple of years ago, I had a flood in my basement. And I invited a

Avi Loeb (1:54:12.720)

plumber to come over and figure out and we found that the sewer was clogged because of

Avi Loeb (1:54:20.560)

tree roots that got into it. And we solved the problem. But then I thought to myself,

Avi Loeb (1:54:28.080)

well, isn't that what happens at the singularity of a black hole? Because the question is,

Avi Loeb (1:54:33.600)

where does the matter go? In the case of a home, I never thought about it, but the water,

Avi Loeb (1:54:39.920)

all the water that we use, goes in through the sewer to some reservoir somewhere. And the question

Avi Loeb (1:54:46.640)

is, what happens inside a black hole? And one possibility is that there is an object in the

Avi Loeb (1:54:51.440)

middle, just like a star, and everything collects there. And the object has the maximum density that

Avi Loeb (1:54:56.800)

we can imagine, like Planck density. It's the ultimate density that you can have, where gravity

Avi Loeb (1:55:03.600)

is as strong as all the other forces. So you can imagine this object, very dense object at the

Avi Loeb (1:55:11.040)

center that collects all the matter. Another possibility is that there is some tunnel just

Avi Loeb (1:55:15.920)

like the sewer. It takes the matter into another place. And we don't know the answer. But I wrote

Avi Loeb (1:55:22.320)

a Scientific American essay about it, admitting our ignorance. It's a fascinating question. What

Avi Loeb (1:55:28.080)

happens to the matter that goes into a black hole? I actually recommend it to some of my colleagues

Avi Loeb (1:55:32.400)

that work on string theory. At the closing of a conference, I'm the founding director of the Black

Avi Loeb (1:55:38.240)

Hole Initiative at Harvard, which brings together astronomers, physicists, philosophers, and

Avi Loeb (1:55:42.960)

mathematicians. And we have a conference once a year. And at the end of one of them, since I'm the

Avi Loeb (1:55:49.040)

director, I had to summarize. And I said that I wish we could go on a field trip to a black hole

Avi Loeb (1:55:56.480)

nearby. And I highly recommend to my colleagues that work on string theory to enter into that

Avi Loeb (1:56:03.120)

black hole, because then they can test their theory when they get inside. But one of the

Avi Loeb (1:56:08.880)

string theorists in the audience, Nimar Khani Hamad, immediately raised his voice and said,

Avi Loeb (1:56:14.000)

you have an ulterior motive for sending us into a black hole, which I didn't deny, but at any event.

Lex Fridman (1:56:21.280)

Yeah, that's true. That's true. Can you say why we know that black holes exist?

Avi Loeb (1:56:32.560)

Right. So it's an interesting question because black holes were considered a theoretical

Avi Loeb (1:56:38.800)

construct. And Einstein even denied their existence in 1939. But then in the mid 1960s, quasars were

Avi Loeb (1:56:51.840)

discovered. These are very bright sources of light, 100 times brighter than their host galaxy,

Avi Loeb (1:56:59.840)

which are point like at the center of galaxies. And it was immediately suggested

Avi Loeb (1:57:06.800)

by Ed Salpeter in the West and by Yakov Zeldovich in the East, that these are black holes that

Avi Loeb (1:57:16.560)

accrete gas, collect gas from their host galaxy that are being fed with gas. And they shine very

Avi Loeb (1:57:23.120)

brightly because as the gas falls towards the black holes, just like water running down the sink,

Avi Loeb (1:57:32.240)

the gas swirls and then rubs against itself and heats up and shines very brightly because it's

Avi Loeb (1:57:41.440)

very hot close to the black hole. By viscosity, it heats up. And in the case of black holes,

Avi Loeb (1:57:49.440)

it's the turbulence, the turbulent viscosity that causes it to heat up. So we get these very bright

Avi Loeb (1:57:56.320)

sources of light just from black holes that are supposed to be dark, nothing but black holes.

Avi Loeb (1:58:01.600)

You know, nothing escapes from them, but they create a violent environment where gas moves

Avi Loeb (1:58:07.680)

close to the speed of light and therefore shines very brightly, much more than any other source

Avi Loeb (1:58:12.880)

in the sky. And we can see these quasars all the way to the edge of the universe.

Lex Fridman (1:58:17.520)

So we have evidence now that when the universe was, you know, about 7% of its present age,

Avi Loeb (1:58:24.000)

you know, infant, already back then you had black holes of a billion times the mass of the sun,

Avi Loeb (1:58:30.240)

which is quite remarkable. It's like finding giant babies in a nursery, you know, like how can these

Avi Loeb (1:58:38.320)

black holes grow so fast? You know, less than a billion years after the Big Bang, you already have

Avi Loeb (1:58:43.040)

a billion times the mass of the sun in these black holes. And the answer is presumably there are very

Avi Loeb (1:58:48.800)

quick processes that build them up. They build quickly. Very quickly. And so we see those black

Avi Loeb (1:58:58.240)

holes, and that was found in the mid 1960s. But in 2015, exactly 100 years after Einstein came up

Avi Loeb (1:59:08.480)

with his theory of gravity, the LIGO observatory detected gravitational waves. And these are just

Avi Loeb (1:59:16.400)

ripples in space and time. So according to Einstein's theory, the innovation, the ingenuity

Avi Loeb (1:59:21.600)

of Einstein's theory of gravity that was formulated in November 1915 was to say that space and time

Avi Loeb (1:59:30.480)

are not rigid. You know, they respond to matter. So, for example, if you have two black holes and

Avi Loeb (1:59:40.240)

they collide, it's just like a stone being thrown on the surface of a pond. They generate waves,

Avi Loeb (1:59:48.400)

disturbances in space and time that propagate out at the speed of light. These are gravitational

Avi Loeb (1:59:53.040)

waves. They create a space time storm around them, and then the waves go all the way through

Avi Loeb (1:59:59.760)

the universe and reach us. And if you have a sensitive enough detector like LIGO, you can

Avi Loeb (20:01.600)

if we were to find it in July 2017, that would have been possible because it was approaching us

Avi Loeb (20:07.760)

at that time. Actually, I was visiting Mount Haleakala in Maui, Hawaii with my family for

Avi Loeb (20:14.240)

vacation at that time in July 2017, but nobody knew at the observatory that the Oumuamua is

Avi Loeb (20:23.440)

very close. That's sad to think about that we had the opportunity at that time to send up a camera.

Lex Fridman (20:28.560)

But don't worry. I mean, there will be more. There will be more because I operate by the Copernican

Avi Loeb (20:35.360)

principle, which says we don't live at a special place and we don't live at a special time. And

Avi Loeb (20:42.000)

that means if we surveyed the sky for a few years and we had sensitivity to this region between us

Lex Fridman (20:48.960)

and the sun, and we found this object with PanStars, there should be many more that we

Avi Loeb (20:55.280)

will find in the future with surveys that might be even better. And actually, in three years

Avi Loeb (21:01.760)

timescale, there would be the so called LSST. That's a survey of the Vera Rubin Observatory

Avi Loeb (21:08.000)

that would be much more sensitive and could potentially find an Oumuamua like object

Avi Loeb (21:14.320)

every month. OK, so I'm just waiting for that. And the main reason for me to alert everyone

Avi Loeb (21:22.160)

to the unusual properties of Oumuamua is with the hope that next time around, when we see

Avi Loeb (21:27.600)

something as unusual, we would take a photograph or we would get as much evidence as possible

Avi Loeb (21:32.560)

because science is based on evidence, not on prejudice. And we will get back to that theme.

Lex Fridman (21:37.920)

So anyway, let me let me point out some of the properties, actually, the elongated nature,

Avi Loeb (21:42.560)

all those kinds of things. So the light curve, the amount of light, sunlight that was reflected

Avi Loeb (21:48.160)

from it was changing over eight hours by a factor of 10, meaning that the area of this

Avi Loeb (21:55.840)

object, even though we can't resolve it, the area on the sky that reflects sunlight was

Avi Loeb (22:02.640)

bigger by a factor of 10 in some phases as it was tumbling around than in other phases.

Lex Fridman (22:09.280)

So even if you take a piece of paper that is razor thin, you know, there is a very small

Avi Loeb (22:14.400)

likelihood that it's exactly edge on and getting a factor of 10 change in the area that you see

Avi Loeb (22:20.720)

on the sky is huge. It's much more than any. It means that the object has an unusual geometry.

Avi Loeb (22:27.760)

It's at least a factor of a few more than any of the comets or asteroids that we have seen before.

Lex Fridman (22:32.640)

You mentioned reflectivity. So it's not just the geometry, but

Avi Loeb (22:35.760)

the properties of the surface of that thing. Well, if you assume the reflectivity is the same,

Avi Loeb (22:42.640)

then it's just geometry. If you assume the reflectivity may change, then it could be

Avi Loeb (22:47.680)

a combination of the area that you see and the reflectivity because different directions may

Avi Loeb (22:52.720)

reflect differently. But the point is that it's very extreme. And actually the best fit

Avi Loeb (23:00.000)

to the light curve that we saw was of a flat object. Unlike all the cartoons that you have seen

Avi Loeb (23:06.640)

of a cigar shape, a flat object at the 90% confidence gives a better model for the way

Avi Loeb (23:13.360)

that the light varied. So like flat meaning like a pancake.

Avi Loeb (23:17.680)

Like a pancake. Exactly. And so that's, you know, the very first unusual property. But to me,

Avi Loeb (23:25.440)

it was not unusual enough to think that it might be artificial. It was not significant enough.

Avi Loeb (23:32.000)

Then there was no cometary tail, you know, no dust, no gas around this object. And the

Avi Loeb (23:38.800)

Spitzer Space Telescope really searched very deeply for carbon based molecules. There was nothing.

Lex Fridman (23:45.680)

So it's definitely not a comet the way people expected it to be.

Lex Fridman (23:49.280)

Can you maybe briefly mention what properties a comet that you're referring to usually has?

Avi Loeb (23:55.760)

Right. So a comet is a rock that has some water ice on the surface. So you can think of it as an

Avi Loeb (24:02.960)

icy rock. Actually comets were discovered a long time ago, but the first model that was developed

Avi Loeb (24:12.320)

for them was by Fred Whipple, who was at Harvard. And I think the legend goes that he got the idea

Avi Loeb (24:19.680)

from walking through Harvard Square and seeing during a winter day and seeing these icy rocks,

Lex Fridman (24:26.560)

you know. So a comet is icy and an asteroid is not.

Avi Loeb (24:30.800)

It's just a rock. It's just a rock.

Lex Fridman (24:32.400)

Yeah. So when you have ice on the surface, when the rock gets close to the sun,

Avi Loeb (24:38.320)

the sunlight warms it up and the ice sublimates, evaporates. Because the one thing about ice,

Avi Loeb (24:46.480)

water ice, is it doesn't become liquid if you warm it up in vacuum, you know, without

Avi Loeb (24:53.280)

an external pressure. It just goes straight into gas. And that's what you see as the tail of a

Avi Loeb (24:59.680)

comet. The only way to get liquid water is to have an atmosphere like on Earth that has an external

Avi Loeb (25:07.120)

pressure. Only then you get liquid. And that's why it's essential to have an atmosphere to a planet

Avi Loeb (25:13.360)

in order to have liquid water and the chemistry of life. So if you look at Mars, Mars lost its

Avi Loeb (25:19.200)

atmosphere and therefore no liquid water on the surface anymore. I mean, there may have been early

Lex Fridman (25:25.120)

and that's what the Perseverance survey, you know, the Perseverance mission will try to find out

Avi Loeb (25:31.600)

whether it had liquid water, whether there was life perhaps on it at the time, but at some point

Avi Loeb (25:37.600)

it lost its atmosphere and then the liquid water was gone. So the only reason that we can live on

Avi Loeb (25:44.000)

Earth is because of the atmosphere. But a comet is in vacuum pretty much. And then when it gets

Avi Loeb (25:51.680)

warmed up on the surface, the water becomes, the water ice becomes gas and then you see this

Avi Loeb (25:58.160)

cometary tail behind it. In addition to water, there are all kinds of carbon based molecules

Avi Loeb (26:05.440)

or dust that comes off the surface. And those are detectable. Yeah, it's easy to detect. It's very

Avi Loeb (26:11.600)

prominent. You see these cometary tails that look very prominent because they reflect sunlight

Lex Fridman (26:16.400)

and you can see them. In fact, it's sometimes difficult to see the nucleus of the comet

Avi Loeb (26:20.640)

because it's surrounded and shrouded with, and in this case, there was no trace of anything.

Avi Loeb (26:26.640)

That's fascinating. Now you might say, okay, it's not a comet. So that's what the community said.

Avi Loeb (26:30.480)

Okay, it's not a, no problem. It's still a rock, you know, it's not a comet,

Lex Fridman (26:34.080)

but it's just a rock, bare rock. You know, okay, no problem. Then, and that's the thing that

Avi Loeb (26:40.320)

convinced me to write about it. And then in June 2018, you know, significantly later,

Avi Loeb (26:46.880)

there was a report that in fact the object exhibited an excess push in addition to the

Avi Loeb (26:55.200)

force of gravity. So the sun acts on it by gravity, but then there was an extra push

Avi Loeb (27:00.080)

on this object that was figured out from the orbit that you can trace. And the question was,

Lex Fridman (27:06.400)

what is this excess push? So for comets, you get the rocket effect. When you evaporate gas,

Avi Loeb (27:12.000)

you know, just like a jet engine on an airplane, you throw, a jet engine is very simple. You throw

Avi Loeb (27:18.000)

the gas back and it pushes the airplane forward. That's all. That's how the jet. So in a case of

Avi Loeb (27:23.840)

a comet, you throw gas in the direction of the sun because it, and then you get a push.

Avi Loeb (27:29.200)

Okay. So in the case of comets, you can get a push, but there was no cometary tail. So then

Avi Loeb (27:34.800)

people say, oh, wait a second. Is it an asteroid? No, but it behaves like a comet, but it doesn't

Avi Loeb (27:40.240)

look like a comet. So what, well, forget about it. Business as usual. So that's what they mean

Avi Loeb (27:45.520)

by a non gravitation acceleration. So that's interesting. So like the primary force acting

Avi Loeb (27:52.080)

on something like just a rock, like an asteroid would be like, you can predict the trajectory

Avi Loeb (27:57.360)

based on the gravity, based on gravity. And so here there's detected movement that's not,

Avi Loeb (28:02.880)

cannot be accounted purely by the gravity of the sun. And if it was a comet, you would need about

Avi Loeb (28:07.600)

a 10th of the mass of this comet, the weight of this comet to be evaporated in order to give it.

Lex Fridman (28:14.080)

And there was no sign of that. No sign. 10% of the mass evaporating. It's huge. Think about it.

Lex Fridman (28:19.760)

A hundred meter size object losing 10% of its mass. You can't miss that.

Lex Fridman (28:25.440)

So that's super weird.

Lex Fridman (28:27.600)

It's super weird.

Lex Fridman (28:28.640)

Is there a good explanation, is there in your mind a possible explanation for this?

Lex Fridman (28:32.160)

So I operated just like Sherlock Holmes in a way. I said, okay, what are the possibilities? And

Avi Loeb (28:37.520)

the only thing I could think, so I ruled out everything else. And I said, it must be the

Avi Loeb (28:42.000)

sunlight reflected off it. Okay. So the sunlight reflects off the surface and gives it a push,

Avi Loeb (28:49.920)

just like you get a push on a sail on a boat, you know, from the wind reflecting off it.

Avi Loeb (28:56.160)

Now, in order for this to be effective, it turns out the object needs to be extremely thin.

Avi Loeb (29:03.440)

It turns out it needs to be less than a millimeter thick. Nature does not produce such things.

Lex Fridman (29:08.640)

But we produce it because it's called the technology of a light sail. So we are,

Avi Loeb (29:15.920)

for space exploration, we are exploring this technology because it has the benefit of

Avi Loeb (29:21.520)

not needing to carry the fuel with the spacecraft. So you don't have the fuel, you just have a

Avi Loeb (29:28.480)

sail and it's being pushed either by sunlight or by a laser beam or whatever. So perhaps this is

Avi Loeb (29:37.680)

the light sail. So this is actually the same technology with the Starshot project. Yes.

Lex Fridman (29:42.800)

So people afterwards say, okay, you work on this project, you imagine. No, that's a pretty good

Avi Loeb (29:49.760)

explanation, right? Obviously, my imagination is limited by what I know. So I would not deny that

Avi Loeb (29:57.040)

working on light sails expanded my ability to imagine this possibility. But let me offer another

Avi Loeb (2:00:05.840)

detect these waves. And so it was not just the message that we received for the first time,

Avi Loeb (2:00:11.120)

gravitational waves, but it was the messenger. So there are two aspects to it. One is the messenger

Avi Loeb (2:00:16.880)

which is gravitational wave for the first time were detected directly. And the second was the

Avi Loeb (2:00:21.120)

message, which was a collision of two black holes, because we could see the pattern of the ripples

Avi Loeb (2:00:27.280)

in space and time. And it was fully consistent with the prediction that Schwarzschild made for

Lex Fridman (2:00:33.520)

how the space time around the black hole is, because when two black holes collide, you can sort

Avi Loeb (2:00:39.280)

of map from the message that you get, you can reconstruct what really happened and it's fully

Avi Loeb (2:00:49.200)

consistent. And in 2017 and 2020, there's two Nobel prizes. That's right. That had to do with the

Avi Loeb (2:01:00.560)

black holes. Can you maybe describe in the same masterful way that you've already been doing what

Avi Loeb (2:01:07.200)

the 2017 was given for the LIGO collaboration for discovering gravitation waves from collisions

Avi Loeb (2:01:13.600)

of black holes? And the 2020 Nobel prize in physics was given for two things. One was

Avi Loeb (2:01:24.800)

theoretical work that was done by Roger Penrose in the 1960s, demonstrating that black holes are

Avi Loeb (2:01:32.080)

inevitable when stars collapse. And it was mostly mathematical work. And actually, Stephen Hawking

Avi Loeb (2:01:41.360)

also contributed significantly to that frontier. And unfortunately, he is not alive, so he could

Avi Loeb (2:01:48.000)

not be honored. So Penrose received it on his own. And then two other astronomers received it as well,

Avi Loeb (2:01:56.720)

Andrea Ghez and Reinhard Genzel, and they provided conclusive evidence that there is a black hole at

Avi Loeb (2:02:03.360)

the center of the Milky Way galaxy that weighs about 4 million times the mass of the sun. And

Avi Loeb (2:02:10.720)

they found the evidence from the motion of stars very close to the black hole. Just like we see the

Avi Loeb (2:02:15.920)

planets moving around the sun, there are stars close to the center of the galaxy and they are

Avi Loeb (2:02:21.360)

orbiting at very high speeds of other thousands of kilometers per second or thousands of miles per

Avi Loeb (2:02:27.360)

second per second. Think about it. Which can only be induced at those distances if there is a 4

Avi Loeb (2:02:37.680)

million solar mass object that is extremely compact. And the only thing that is compatible

Avi Loeb (2:02:46.560)

with the constraints is a black hole. And they actually made a movie of the motion of these

Avi Loeb (2:02:54.160)

stars around the center. One of them moves around the center over a decade, over timescales that we

Avi Loeb (2:03:00.800)

can monitor. And it was a breakthrough in a way. So combining LIGO with the detection of a black

Avi Loeb (2:03:11.280)

hole at the center of the Milky Way and in many other galaxies like quasars, now I would say

Avi Loeb (2:03:20.720)

black hole research is vogue. It's very much in fashion. We saw it back in 2016 when we established

Avi Loeb (2:03:28.240)

the black hole initiative. You kind of saw that there's this excitement about in breakthroughs

Lex Fridman (2:03:37.120)

and discoveries around black holes which are probably one of the most fascinating objects

Avi Loeb (2:03:42.000)

in the universe. It's up there. They're both terrifying and beautiful and they capture the

Avi Loeb (2:03:49.360)

entirety of the physics that we know about this universe. I should say the question is where is

Avi Loeb (2:03:53.760)

the nearest black hole? Can we visit it? And I wrote a paper with my undergraduate student,

Avi Loeb (2:04:01.040)

Amir Siraj, suggesting that perhaps if there is one in the solar system, we can detect it.

Avi Loeb (2:04:09.840)

I don't know if you heard, but there is a claim that maybe there is a

Avi Loeb (2:04:14.000)

planet nine in the solar system because we see some anomalies at the outer parts of the solar

Avi Loeb (2:04:20.960)

system. So some people suggested maybe there is a planet out there that was not yet detected. So

Avi Loeb (2:04:26.400)

people searched for it, didn't find it. It weighs roughly five times the mass of the earth. And we

Avi Loeb (2:04:32.240)

said, okay, maybe you can't find it because it's a black hole that was formed early in the universe.

Lex Fridman (2:04:39.680)

Where do you stand on that?

Avi Loeb (2:04:40.640)

It could be that the dark matter is made of black holes of this mass. We don't know what

Avi Loeb (2:04:44.480)

the dark matter is made of. It could be the black holes. So we said, but there is an experimental

Avi Loeb (2:04:50.240)

way to test it. And the way to do it is because there is the Oort cloud of icy rocks in the outer

Avi Loeb (2:04:59.680)

solar system. And if you imagine a black hole there, every now and then a rock will pass close

Avi Loeb (2:05:06.400)

enough to the black hole to be disrupted by the very strong gravity close to the black hole. And

Avi Loeb (2:05:12.400)

that would produce a flare that you can observe. And we calculated how frequently these flares

Avi Loeb (2:05:17.600)

should occur. And with LSST on the Vera Rubin Observatory, we found that you can actually

Avi Loeb (2:05:23.120)

test this hypothesis. And if you don't see flares, then you can put limits on the existence of a

Avi Loeb (2:05:29.440)

black hole in the solar system. It would be extremely exciting if there was a black hole,

Avi Loeb (2:05:33.920)

if planet nine was a black hole, because we could visit it and we can examine it. And it will not

Avi Loeb (2:05:41.520)

be a matter of an object that is very removed from us. Another thing I should say is it's

Avi Loeb (2:05:47.920)

possible that the black hole affected life on Earth. The black hole at the center of the Milky

Avi Loeb (2:05:53.920)

Way. How? That black hole right now is dormant. It's very faint. But we know that it flares.

Avi Loeb (2:06:04.080)

When a star like the sun comes close to it, the star will be spaghettified, basically become a

Avi Loeb (2:06:10.800)

stream of gas, like a spaghetti. And then the gas would fall into the black hole and there would be

Avi Loeb (2:06:16.640)

a flare. And this process happens once every 10,000 years or so. So we expect that these flares to

Avi Loeb (2:06:22.960)

occur every 10,000 years. But we also see evidence for the possibility that gas clouds were disrupted

Avi Loeb (2:06:31.120)

by the black hole, because the stars that are close to the black hole are residing in a single

Avi Loeb (2:06:36.560)

or two planes. And the only way you can get that is if they formed out of a disk of gas,

Avi Loeb (2:06:42.080)

just like the planets in the solar system formed. So there is evidence that gas fell into the black

Avi Loeb (2:06:48.320)

hole and powered possibly a flare. And these flares produce x rays and ultraviolet radiation

Avi Loeb (2:06:56.240)

that could damage life if the Earth was close enough to the center of the galaxy.

Avi Loeb (2:07:02.640)

Where we are right now, it's not very risky for us. But there is a theoretical argument that says

Avi Loeb (2:07:10.960)

the solar system, the sun, was closer to the galactic center early on, and then it migrated

Avi Loeb (2:07:17.120)

outwards. So maybe in the early stage of the solar system, the conditions were affected,

Avi Loeb (2:07:27.200)

shaped by these flares of the black hole at the center of the galaxy. And that's why

Avi Loeb (2:07:31.440)

for the first two billion years, there wasn't any oxygen in the atmosphere, who knows. But

Avi Loeb (2:07:37.440)

it's just interesting to think that from a theoretical concept that Einstein resisted in 1939,

Avi Loeb (2:07:44.640)

it may well be that black holes have influence on our life. And that it's just like discovering that

Avi Loeb (2:07:51.280)

some stranger affected your family and in a way your life. And if that happens to be the case,

Avi Loeb (2:08:04.560)

a second Nobel Prize should be given, not for just the discovery of this black hole at the

Avi Loeb (2:08:10.640)

center of the galaxy, but perhaps for the Nobel Prize in chemistry, for the effect that it had.

Avi Loeb (2:08:15.200)

For the effect for the interplay that resulted in some kind of, yeah, the chemical effect,

Avi Loeb (2:08:23.680)

biology, I mean, all those kinds of things in terms of the emergence of life and the creation

Avi Loeb (2:08:30.320)

of a habitable environment. That's so fascinating. And of course, like you said, dark matter, like

Avi Loeb (2:08:35.360)

black holes have some... They could be the dark matter in principle, yes. We don't know what the

Avi Loeb (2:08:41.440)

dark matter is at the moment. Does it make you sad? So you've had an interaction and perhaps

Lex Fridman (2:08:46.960)

a bit of a friendship with Stephen Hawking. Does it make you sad that he didn't win the Nobel?

Avi Loeb (2:08:52.000)

Well, all together, I don't assign great importance to prizes because, you know,

Avi Loeb (2:08:58.960)

Jean Paul Sartre, who I admired as a teenager, because I was interested in philosophy. When I

Avi Loeb (2:09:04.880)

grew up on a farm in Israel, I used to collect eggs every afternoon and I would drive the tractor to

Avi Loeb (2:09:11.520)

the hills of our village and just think about philosophy, read philosophy books. And Jean Paul

Avi Loeb (2:09:16.480)

Sartre was one of my favorites. And he was honored with a Nobel Prize in literature. He was a

Avi Loeb (2:09:22.080)

philosopher primarily, existentialist. And he said, the hell with it. Why should I give

Avi Loeb (2:09:27.600)

special attention to this committee of people that get their self importance from awarding me

Avi Loeb (2:09:36.160)

the prize? Why does that merit my attention? So he gave up on the Nobel Prize. And

Avi Loeb (2:09:44.480)

you know, there are two benefits to that. One, that you're not working your entire life in the

Avi Loeb (2:09:52.000)

direction that would satisfy the will of other people. You work independently, you're not

Avi Loeb (2:09:57.440)

after these honors. Just for the same reason that if you're not living your life for making a profit

Avi Loeb (2:10:04.960)

or money, you can live a more fulfilling life because you're not being swayed by the wind,

Avi Loeb (2:10:10.480)

you know, of how to make money and so forth. The second aspect of it is, you know, that

Avi Loeb (2:10:17.120)

very often, you know, these prizes, they distort the way we do science because instead of people

Avi Loeb (2:10:29.520)

willing to take risks, and instead of having announcements only after a group of people

Avi Loeb (2:10:36.400)

converges with a definite result, you know, the natural progression of science is based on trial

Lex Fridman (2:10:44.800)

and error, you know, reporting some results, and perhaps they're wrong, but then other people find

Avi Loeb (2:10:50.320)

perhaps better evidence, and then you figure out what's going on. And that's the natural way that

Avi Loeb (2:10:54.800)

science is, you know, it's a learning experience. So if you give the public an image by which

Avi Loeb (2:11:00.800)

scientists are always right, you know, and you know, some of my colleagues say we must do that,

Avi Loeb (2:11:06.080)

because otherwise the public will never believe us that global warming is really taking place.

Lex Fridman (2:11:10.400)

But that's not true, because the public would really believe you if you show the evidence. So

Avi Loeb (2:11:15.360)

the point is, you should be sincere. When the evidence is not absolutely clear, or where there

Avi Loeb (2:11:19.920)

are disputes about the interpretation of the evidence, we should show ourselves. You know,

Avi Loeb (2:11:23.600)

the king is naked, okay? There is no point in pretending that the king is dressed,

Avi Loeb (2:11:30.160)

saying that scientists are always right. Scientists are wrong, frequently. And the only way to make

Avi Loeb (2:11:36.480)

progress is by evidence, giving us the support that we need to make airtight arguments. So when

Avi Loeb (2:11:43.440)

you say global warming is taking place, if the evidence is fully supportive, there are no holes

Avi Loeb (2:11:49.760)

in the argument, then people will be convinced, because you're not trying to fool them. When the

Avi Loeb (2:11:55.360)

evidence was not complete, you also show them that the evidence is not complete.

Lex Fridman (2:11:58.480)

And when there's holes, you show that there's holes, and here's the methodology we're using

Avi Loeb (2:12:02.320)

to try to close those holes. Exactly. Let's be sincere. Why pretend? So if there were no,

Avi Loeb (2:12:06.800)

in a world where there were no prizes, no honours, we would act like kids, as I said before.

Avi Loeb (2:12:13.600)

We would really be focusing on the ball and not on the audience. Yeah, the prizes get in the way,

Lex Fridman (2:12:19.120)

and it's so powerful. Do you think, in some sense, the few people that have turned down the prize

Avi Loeb (2:12:26.240)

made a much more powerful statement? I don't know if you're familiar in the space of mathematics

Avi Loeb (2:12:31.920)

with the Fields Medal and Google Perlman turned down the prize. One of the reasons I started

Avi Loeb (2:12:40.960)

this podcast is I'm going to definitely talk to Putin, I'm definitely talking to Perlman,

Lex Fridman (2:12:46.000)

and people keep telling me it's impossible. I love hearing that, because I'll talk to both.

Lex Fridman (2:12:52.160)

Anyway, but do you have a sense of why he turned down the prize,

Lex Fridman (2:13:00.480)

and is that a powerful statement to you? Well, what I read is that he was disappointed by the

Avi Loeb (2:13:10.960)

response of the community, the mainstream community, the mathematicians, to his earlier work,

Avi Loeb (2:13:17.520)

where they dismissed it, they didn't attend to the details, and didn't treat him with proper

Avi Loeb (2:13:24.480)

respect, because he was not considered one of them. And I think that speaks volumes about the

Avi Loeb (2:13:32.640)

current scientific culture, which is based on groupthink and on social interaction, rather

Avi Loeb (2:13:42.080)

than on the merit of the argument, and on the evidence in the context of physics. So in mathematics

Avi Loeb (2:13:47.200)

there is no empirical basis, you're exploring ideas that are logically consistent, but nevertheless

Avi Loeb (2:13:54.160)

there is this groupthink. And I think he was so frustrated with his past experience that he didn't

Avi Loeb (2:14:02.080)

even bother to publish his papers, he just posted them on the archive, and in a way saying, you know,

Avi Loeb (2:14:09.680)

I know what the answer is, go look at it. And then again, in the long arc of history,

Avi Loeb (2:14:17.040)

his work on archive will be remembered, and all the prizes, most of the prizes will be forgotten,

Avi Loeb (2:14:23.280)

that's what people don't kind of think about. When you look at Roger Penrose, for example,

Avi Loeb (2:14:29.440)

is another fascinating figure, you know, it's possible, and forgive me if this, I'm sure,

Avi Loeb (2:14:35.280)

my ignorance, but he's also did some work on consciousness. He's been one of the only people

Avi Loeb (2:14:40.640)

who spoke about consciousness, which for the longest time, and is still arguably outside

Avi Loeb (2:14:47.040)

the realm of the sciences. It's still seen as a taboo subject, and he was brave enough to explore

Avi Loeb (2:14:55.920)

it from a physics perspective, from just a philosophical perspective, but like with the rigor,

Avi Loeb (2:15:01.680)

like proposing different kind of hypotheses of how consciousness might be able to emerge in the brain,

Lex Fridman (2:15:07.600)

and it's possible that that is the thing he's remembered for if you look 100 years from now,

Avi Loeb (2:15:11.840)

right? As opposed to the work in the black holes, which fits into what the current scientific

Avi Loeb (2:15:22.640)

community allows to be the space of what is and isn't science. Yeah, it's really interesting to

Avi Loeb (2:15:30.160)

look at people that are innovators, where in some phases of their career, their ideas fit into the

Avi Loeb (2:15:37.600)

social structure that is around them, but in other phases, it doesn't. And when you look at them,

Avi Loeb (2:15:44.240)

they just operated the same way throughout, and it says more about their environment than about them.

Avi Loeb (2:15:51.440)

Well, yeah, and I don't know if you know who Max Tegmark is, I just recently talked to him.

Lex Fridman (2:15:55.360)

He's a friend of mine.

Avi Loeb (2:15:56.400)

I just recently talked to him again, and he, I mean, he was a little bit more explicit about

Avi Loeb (2:16:01.360)

saying, you know, being aware, which is something I also recommend, is like being aware where the

Avi Loeb (2:16:06.000)

scientific community stands, and doing enough to get, like move along into your career, in your

Avi Loeb (2:16:11.280)

career. And it's the necessary evil, I suppose, if you are one of those out of the box thinkers that

Avi Loeb (2:16:17.920)

just naturally have this childlike curiosity, which Max definitely is one of them, is sometimes

Avi Loeb (2:16:23.120)

you have to do some stuff that fits in, you publish and you get tenure and all those kinds of things.

Lex Fridman (2:16:27.440)

But the tenure is a great privilege because it allows you to, in principle, explore things that

Avi Loeb (2:16:32.560)

are not accepted by others. And unfortunately, it's not being taken advantage of by most people,

Lex Fridman (2:16:40.240)

and it's a waste of a very precious resource.

Avi Loeb (2:16:43.680)

Yeah, absolutely. The space that you kind of touched on that's full of theories and is perhaps

Avi Loeb (2:16:52.400)

detached from appreciation of empirical evidence, or longing for empirical evidence, or grounding

Avi Loeb (2:17:00.400)

in empirical evidence, is the theoretical physics community and the interest in unifying the laws

Avi Loeb (2:17:07.440)

of physics and with the theory of everything. I'm not sure from which direction to approach this

Avi Loeb (2:17:15.600)

question, but how far away are we from arriving at a theory of everything, do you think? And how

Avi Loeb (2:17:25.120)

would we, how important is it to try to arrive at it, at this kind of goal of this beautiful simple

Avi Loeb (2:17:33.680)

theory that unlocks the very, you know, fundamental basis of our nature as we know it? And, you know,

Lex Fridman (2:17:45.280)

and how, what are the kinds of approaches we need to take to get there?

Avi Loeb (2:17:50.160)

Yeah, so in physics, the biggest challenge is to unify quantum mechanics with gravity.

Lex Fridman (2:17:56.240)

And I believe that once we have experimental evidence for how this happens in nature,

Lex Fridman (2:18:04.320)

in systems that have quantum mechanical effects, but also gravity is important,

Avi Loeb (2:18:09.920)

then the theory will fall into our lap, okay? But the mistake that is made by the community

Avi Loeb (2:18:17.040)

right now is to come up with the right theory from scratch. And, you know, Einstein gave the

Avi Loeb (2:18:25.200)

illusion that you can just sit in your office and understand nature, you know, when he came up with

Avi Loeb (2:18:30.720)

his general theory of relativity. But, you know, first of all, perhaps he was lucky, but it's not

Avi Loeb (2:18:38.400)

a rule. The rule is that you need evidence to guide you, especially when dealing with quantum

Avi Loeb (2:18:42.880)

mechanics, which is really not intuitive. And so there are two places where the two theories meet.

Avi Loeb (2:18:52.320)

One is black holes, and there is a puzzle there. It's called the information paradox.

Avi Loeb (2:18:58.480)

In principle, you can throw the Encyclopedia Britannica into a black hole. It's a lot of

Avi Loeb (2:19:02.640)

information. And then it will be gone because a black hole carries only three properties or

Avi Loeb (2:19:12.720)

qualities, the mass, the charge, and the spin, according to Einstein. But then when Hawking

Avi Loeb (2:19:19.600)

tried to bring in quantum mechanics to the game, he realized that black holes have a temperature

Lex Fridman (2:19:26.560)

and they radiate. This is called Hawking radiation. It was sort of anticipated by

Avi Loeb (2:19:35.440)

Jacob Bekenstein before him, and Hawking wanted to prove Bekenstein wrong and then figure this out.

Lex Fridman (2:19:42.240)

And so what it means is black holes eventually evaporate. And they evaporate into radiation that

Avi Loeb (2:19:48.800)

doesn't carry this information, according to Hawking's calculation. And then the question is,

Avi Loeb (2:19:53.840)

according to quantum mechanics, information must be preserved. So where did the information go

Avi Loeb (2:20:00.240)

if a black hole is gone? And where is the information that was encoded in the Encyclopedia

Avi Loeb (2:20:06.640)

when it went into the black hole? And to that question, we don't have an answer yet. It's one

Avi Loeb (2:20:12.640)

of those puzzles about black holes. And it touches on the interplay between quantum mechanics and

Lex Fridman (2:20:17.920)

gravity. Another important question is what happened at the beginning of the universe?

Lex Fridman (2:20:24.480)

What happened before the Big Bang? And by the way, on that, I should say, you know, there are some

Avi Loeb (2:20:31.280)

conjectures. In principle, if we figure it out, if we have a theory of quantum gravity,

Avi Loeb (2:20:37.760)

it's possible to imagine that we will figure out how to create a universe in the laboratory.

Lex Fridman (2:20:43.440)

And by irritating the vacuum, you might create a baby universe. And if we do that,

Avi Loeb (2:20:50.640)

it will offer a solution to what happened before the Big Bang. Perhaps the Big Bang emerged from

Avi Loeb (2:20:55.600)

the laboratory of another civilization. So it's like baby universes are being born out of

Avi Loeb (2:21:01.840)

laboratories. And inside the baby universe, you have a civilization that brings to existence a

Avi Loeb (2:21:07.520)

new baby universe. So just like humans, right? We have babies and they make babies. So in principle,

Avi Loeb (2:21:13.120)

that would solve the problem of why there was a Big Bang and also what happened before the Big

Avi Loeb (2:21:19.760)

Bang. So we came, our umbilical cord is connected to a laboratory of a civilization that produced

Avi Loeb (2:21:26.960)

our universe once it figured out quantum gravity, you know. It's baby Big Bangs all the way down.

Lex Fridman (2:21:36.160)

So if we collect data about how the universe started, we could potentially test

Avi Loeb (2:21:40.320)

theories of, or it can educate us about how to unify quantum mechanics and gravity.

Avi Loeb (2:21:45.520)

If we get any information about what happens near the singularity of a black hole,

Avi Loeb (2:21:50.400)

you know, if we get a sense of, you know, somehow we learn what happens at the same,

Avi Loeb (2:21:56.800)

that would educate. So there are places where we can search for evidence, but it's very challenging,

Avi Loeb (2:22:03.120)

I should say. And my point is, you know, the string theorists, they decided that they know

Lex Fridman (2:22:08.640)

how to approach the problem, that they don't have a single theory. There is a multitude of theories

Lex Fridman (2:22:15.440)

and it's not tightly constrained and they cannot make predictions about black holes or about the

Avi Loeb (2:22:21.040)

beginning of the universe. So at the moment I say we're at a loss. And the way I feel about this

Avi Loeb (2:22:27.200)

concept of the theory of everything, we should wait until we get enough evidence to guide us.

Lex Fridman (2:22:32.880)

And until then, you know, there are many important problems that we can address,

Lex Fridman (2:22:36.320)

you know. Why bang our head against the wall on a problem for which we have no guidance?

Lex Fridman (2:22:43.200)

Right. We don't have a good dance partner in terms of evidence. There's not.

Avi Loeb (2:22:46.640)

Exactly.

Avi Loeb (2:22:47.040)

I mean, it'd be interesting, just like you said, I mean, the lab is one place to create

Avi Loeb (2:22:53.760)

universes or black holes, but it'd be fascinating if there is indeed a black hole in our solar

Avi Loeb (2:22:58.720)

system that you can interact with. So the problem with the origin of the universe

Avi Loeb (2:23:03.440)

is all you can do is collect data about it, right? You can't interact with it.

Avi Loeb (2:23:07.600)

Well, you can, for example, detect gravitational waves that emerged from that. And, you know,

Avi Loeb (2:23:13.200)

there is an effort to do that and that could potentially tell us something. But yeah,

Avi Loeb (2:23:18.800)

it's a challenge and that's why we're stuck. So I should say, despite what physicists portray,

Avi Loeb (2:23:25.840)

that, you know, we live through an exceptional growth in our understanding of the universe,

Avi Loeb (2:23:31.360)

we're actually pretty much stuck, I would say, because we don't know the nature of the dark

Avi Loeb (2:23:36.240)

matter. Most of the matter in the universe, we don't know what it is. And we don't know how

Avi Loeb (2:23:40.640)

the universe started. We don't know what happens in the interior of a black hole.

Avi Loeb (2:23:45.760)

Because you've thought quite a bit about dark matter as well. Do you have any kind of hypothesis,

Avi Loeb (2:23:50.240)

interesting hypothesis? We already mentioned a few about what is dark matter and what are the

Lex Fridman (2:23:55.680)

possible paths that we could take to unlock the mystery of dark? What is dark matter?

Avi Loeb (2:24:01.440)

Yeah. So what we need is some anomalies that would hint what the nature of the dark matter is,

Avi Loeb (2:24:07.040)

or to detect it in the laboratory. There are lots of laboratory experiments searching,

Lex Fridman (2:24:11.040)

but it's like searching for a needle in a haystack, because there are so many possibilities

Avi Loeb (2:24:15.040)

for the type of particle that it may be. But maybe at some point, you know, we'll find either

Avi Loeb (2:24:21.520)

a particle or black holes as the dark matter, or something else. But at the moment...

Lex Fridman (2:24:26.240)

Can you also maybe, sorry to interrupt, comment about what is dark matter?

Lex Fridman (2:24:30.240)

Like what, it's just a name we assign to what?

Lex Fridman (2:24:33.520)

So most of the community believes that it's a particle that we haven't yet detected. It doesn't

Avi Loeb (2:24:40.720)

interact with light, so it's dark. But the question is, what does it interact with,

Lex Fridman (2:24:46.000)

and how can we find it? And for many years, physicists were guided by the idea that

Avi Loeb (2:24:52.240)

it's some extension of the standard model of particle physics. But then they said,

Avi Loeb (2:24:57.360)

oh, we will find some clues from the Large Hadron Collider about its nature. Or maybe

Avi Loeb (2:25:03.120)

it's related to supersymmetry, which is a new symmetry that we haven't found any evidence for.

Avi Loeb (2:25:07.680)

In both cases, the Large Hadron Collider did not give us any clues. And other people search for

Avi Loeb (2:25:13.360)

specific types of particles in the laboratory and didn't find any. A couple of years ago,

Avi Loeb (2:25:19.120)

actually, around the time that I worked on Oumuamua, I also worked on the possibility that

Avi Loeb (2:25:25.760)

the dark matter particles may have a small electric charge, which is a speculation, but

Avi Loeb (2:25:32.000)

nobody complained about it. And, you know, it was published and I regarded it more as

Avi Loeb (2:25:38.160)

of a speculation than the artificial origin of Oumuamua. And to me, I apply, you know,

Avi Loeb (2:25:44.960)

as far as I'm concerned, I apply the same scientific tools in both cases. There is an

Avi Loeb (2:25:48.800)

anomaly that led me to that discussion, which has to do with hydrogen being cold in the early

Avi Loeb (2:25:55.040)

universe more than we expected. So we suggested maybe the dark matter particles have some small

Avi Loeb (2:25:59.520)

charge. But then you deal with anomalies by exploring possibilities. That's the only way to

Avi Loeb (2:26:05.360)

do it, and then collecting more data to check those. And searching for technological signatures

Avi Loeb (2:26:14.960)

is the same as any other part of our scientific endeavor. We make hypotheses and we collect data,

Lex Fridman (2:26:23.520)

and I don't see any reason for having a taboo on this subject.

Avi Loeb (2:26:27.120)

In your childlike, open minded excitement and approach to science, you're, I think,

Avi Loeb (2:26:33.600)

to anyone listening to this, truly inspiring. I mean, the question I think is useful to ask

Avi Loeb (2:26:38.800)

is by way of advice for young people. A lot of young people listen to this, whether from all

Avi Loeb (2:26:45.200)

over the world, and teenagers, undergraduate students, even graduate students, even young

Avi Loeb (2:26:53.680)

faculty, even older faculty, they're all young at heart. Like there's many of them young at heart.

Lex Fridman (2:26:58.320)

Do you have advice for, but let's focus on the traditionally defined sort of young folks that

Avi Loeb (2:27:04.160)

kind of graduate. Do you have advice to give to young people like that today about life,

Lex Fridman (2:27:10.560)

maybe in general, maybe a life of curiosity in the sciences?

Avi Loeb (2:27:14.960)

Definitely. Well, first, I should confess that I enjoy working with young people much more than

Avi Loeb (2:27:20.160)

with senior people. And the reason is they don't carry a baggage of prejudice. They're not so

Avi Loeb (2:27:26.880)

self centered. They're open to exploration. My advice, I mean, one of the lessons that

Avi Loeb (2:27:34.000)

took me a while to learn, and I should say I lost important opportunities as a result of that. So

Avi Loeb (2:27:40.720)

I would regard it as a mistake on my behalf, was to believe experts. So, quote unquote. So on a

Avi Loeb (2:27:50.640)

on a number of occasions, I would come up with an original idea and then suggest it to an expert,

Avi Loeb (2:27:57.760)

someone that works in the same field for a while. And the expert would dismiss it most of the time

Avi Loeb (2:28:04.480)

because it's new and was not explored, not because of the merit. And then what happened to me several

Avi Loeb (2:28:11.840)

times is that someone else would listen to the conversation or would hear me suggesting it.

Lex Fridman (2:28:17.520)

And I would give up because the expert said no. And then that someone else would develop it so

Avi Loeb (2:28:25.680)

that it becomes the hottest thing in this field. And once it happened to me multiple times,

Avi Loeb (2:28:31.680)

I then realized the hell with the experts. They don't know what they're doing. They're

Avi Loeb (2:28:36.880)

just repeating them. They don't think creatively. They are being threatened by innovation. And it's

Avi Loeb (2:28:45.200)

the natural reaction of someone that cares about their ego more than about the matter

Avi Loeb (2:28:52.000)

that we are discussing. And so I said, I don't care how many likes I have on Twitter. I don't

Avi Loeb (2:28:57.760)

care whether the experts say one thing or another. I will basically exercise my judgment and do the

Avi Loeb (2:29:03.200)

best I can. Turns out that I'm wrong. I made a mistake. That's part of the scientific endeavor.

Lex Fridman (2:29:10.720)

And it took me a while to recognize that. And it was a lot of wasted opportunities. So to the

Avi Loeb (2:29:16.800)

young people, I would recommend don't listen to experts. Carve your own path. Now, of course,

Avi Loeb (2:29:24.400)

you will be wrong. You should learn from experience, just like kids do. But do it yourself.

Lex Fridman (2:29:30.160)

Your father died in 2017. Your mother died in 2019. Do you miss them?

Avi Loeb (2:29:40.400)

Very much so.

Lex Fridman (2:29:42.800)

Is there a memory, that fond memory that stands out? Or maybe what have you learned from them?

Avi Loeb (2:29:50.800)

From my mother, I mean, she was very much my inspiration for pursuing intellectual work,

Avi Loeb (2:30:00.160)

because she studied at the university. And then because of the Second World War,

Avi Loeb (2:30:08.000)

after the Second World War, she was born in Bulgaria. They immigrated to Israel. And she

Lex Fridman (2:30:15.680)

and she left university to work on a farm. And later in life, when all the kids left home,

Avi Loeb (2:30:24.640)

she went back to the university and finished the PhD. But she planted in me the intellectual

Avi Loeb (2:30:30.720)

curiosity and valuing learning or acquiring knowledge as a very important element in life.

Lex Fridman (2:30:41.040)

And my love with philosophy came from attending classes that she took at the university.

Avi Loeb (2:30:50.160)

When I was a teenager, I was fortunate to go to some of these and they inspired me later on. And

Avi Loeb (2:30:58.080)

I'm very different than my colleagues, as you can tell, because my upbringing was quite different.

Lex Fridman (2:31:03.920)

And the only reason I'm doing physics or astrophysics is because of circumstances.

Avi Loeb (2:31:08.320)

At age 18, I was asked to serve in the military. And the only way for me to pursue intellectual

Avi Loeb (2:31:17.440)

work was to work on physics, because that was the closest to philosophy. And I was good at physics.

Lex Fridman (2:31:25.920)

So they admitted me to an elite program called LPO that allowed me to finish my PhD

Avi Loeb (2:31:30.960)

at age 24 and to actually propose the first international project that was funded by the

Avi Loeb (2:31:38.560)

Star Wars initiative of Ronald Reagan. And that brought me to the US to visit Washington, DC,

Avi Loeb (2:31:45.120)

where we were funded from. And then on one of the visits, I went to the Institute for Advanced

Avi Loeb (2:31:51.520)

Study at Princeton and met John Bacall that later offered me a five year fellowship there. Under the

Avi Loeb (2:31:59.200)

under the condition that I'll switch to astrophysics. At which point, you know, I said,

Avi Loeb (2:32:03.920)

OK, I cannot give up on this opportunity. I'll do it. Switch to astrophysics. It felt like a forced

Avi Loeb (2:32:10.080)

marriage, kind of arranged marriage. And then I was offered the position at Harvard because

Avi Loeb (2:32:15.920)

nobody wanted that. They first selected someone else. And that someone said, I don't want to

Avi Loeb (2:32:22.320)

become a junior faculty at the Harvard Astronomy Department because the chance for being promoted

Avi Loeb (2:32:27.760)

are very small. So he took another job. And then I was second in line. They gave it to me. I didn't

Avi Loeb (2:32:33.120)

care much because I could go back to the farm any day, you know. And after three years, I was

Avi Loeb (2:32:39.120)

tenured. And eventually, a decade later, became the chair of this department and served for nine years

Avi Loeb (2:32:46.160)

as the chair of the astronomy department at Harvard. But at that point, it became clear

Avi Loeb (2:32:51.360)

to me that I'm actually married to the love of my life, even though it was an arranged marriage.

Avi Loeb (2:32:56.480)

There are many philosophical questions in astrophysics that we can address. But I'm still

Avi Loeb (2:33:01.360)

very different than my colleagues, you know, that were focusing on technical skills in getting to

Avi Loeb (2:33:07.920)

this job. So my mother was really extremely instrumental in planting the seeds of thinking

Avi Loeb (2:33:17.280)

about the big picture in me. Then my father, he was, you know, he was working in the farm.

Lex Fridman (2:33:24.240)

And we didn't speak much because we sort of understood each other without speaking.

Lex Fridman (2:33:30.480)

But what he gave me is a sense of, you know, that it's more important to do things than to

Avi Loeb (2:33:39.920)

talk about them. I love the, I mean, my apologies, but MIT mind and hand. I love that there's

Avi Loeb (2:33:47.600)

that the root of philosophy that you gain from your mom and the hand, that action is all that

Avi Loeb (2:33:54.320)

ultimately in the end matters from your dad. That's really powerful. If we could take a small

Avi Loeb (2:34:00.720)

detour into philosophy, is there by chance any books, authors, whether philosophical or not,

Avi Loeb (2:34:10.000)

you mentioned Sartre, that stand out to you that were formative in some small or big way,

Lex Fridman (2:34:15.040)

that perhaps you would recommend to others, maybe when you were very young or maybe later on in life?

Lex Fridman (2:34:20.640)

Well, actually, yeah, I, you know, I read the number of existentialists that

Avi Loeb (2:34:27.920)

appealed to me because they were authentic. You know, Sartre, you know, he declined the Nobel

Avi Loeb (2:34:32.800)

Prize, as we discussed, but he also was mocking people that pretend to be something better than

Avi Loeb (2:34:39.920)

they are. You know, he was living an authentic life that is sincere. And that's what appealed to me.

Lex Fridman (2:34:45.760)

And Albert Camus was another French philosopher that advocated existentialism. You know, that

Avi Loeb (2:34:53.840)

really appealed to me. That's probably my favorite existentialist, Camus. Yeah. Yeah. And he died at

Avi Loeb (2:34:58.960)

a young age in an accident, unfortunately. And then, you know, people like Nietzsche that, you

Avi Loeb (2:35:07.200)

know, broke conventions. And I noticed that Nietzsche is still extremely popular. You know,

Avi Loeb (2:35:16.880)

that's quite surprising. He appeals to the young people of today. It's the childlike wonder

Avi Loeb (2:35:25.440)

about the world. And he was unapologetic. You know, it's like most philosophers have a very

Avi Loeb (2:35:30.960)

strict adherence to terminology and to the practices, academic philosophers. And Nietzsche was full of

Avi Loeb (2:35:36.160)

contradictions. And he just, I mean, he was just this big kid with opinions and thought deeply

Avi Loeb (2:35:44.640)

about this world. And people are really attracted to that. And surprisingly, there's not enough

Avi Loeb (2:35:49.040)

people like that throughout history of philosophy. And that's why I think he's still drawn to them.

Avi Loeb (2:35:55.600)

Yeah. To me, what stands out is his statement that the best way to corrupt the mind of young people

Avi Loeb (2:36:03.280)

is to tell them that they should agree with the common view, you know. And, you know, it goes back

Avi Loeb (2:36:11.600)

to the thread that went throughout discussion. Yes. You've kind of suggested that we ought to

Avi Loeb (2:36:18.400)

be humble about our very own existence and that our existence lasts only a short time. We talked

Avi Loeb (2:36:25.520)

about you losing your father and your mother. Do you think about your own mortality? Are you afraid

Avi Loeb (2:36:34.480)

of death? I'm not afraid. You know what, Epicurus, actually Epicurus was a very wise person.

Avi Loeb (2:36:41.520)

According to Lucretius, Epicurus didn't leave anything in writing. But he said that he's never

Avi Loeb (2:36:48.000)

afraid of death because as long as he's around, death is not around. And when death will be around,

Avi Loeb (2:36:56.160)

he will not be around. So he will never meet death. So why should you be worried about something

Avi Loeb (2:37:01.520)

you will never meet? You know, and it's an interesting philosophy of life. You know,

Lex Fridman (2:37:06.240)

you shouldn't be afraid of something that you will never encounter, right?

Lex Fridman (2:37:09.360)

But there's a finiteness to this experience. We live every day.

Avi Loeb (2:37:13.920)

I mean, I think if we're being honest, we live every day as if it's going to last forever.

Avi Loeb (2:37:20.880)

We often kind of don't contemplate the fact that it ends. You kind of have plans and goals and you

Avi Loeb (2:37:26.880)

have these possibilities. You have a kind of lingering thought, especially as you get older

Lex Fridman (2:37:31.760)

and older and older, that this is, especially when you lose friends, then you start to realize,

Avi Loeb (2:37:38.720)

you know, it does end. But I don't know if you really are cognizant of that. I mean,

Avi Loeb (2:37:43.600)

because... But you have to be careful not to be depressed by it, because otherwise you lose the

Avi Loeb (2:37:48.800)

vitality, right? So I think the most important thing to draw from knowing that you are short lived

Avi Loeb (2:37:56.160)

is a sense of appreciation that you're alive. That's the first thing. But more importantly,

Avi Loeb (2:38:02.320)

a sense of modesty, because how can anyone be arrogant if they kept at the same time this

Avi Loeb (2:38:09.760)

notion that they are short lived? I mean, you cannot be arrogant, because anything that you

Avi Loeb (2:38:14.080)

advocate for, you know, you will not be around to do that in a hundred years. So people will

Avi Loeb (2:38:19.920)

just forget and move on, you know. And if you keep that in mind, you know, the Caesars in ancient

Avi Loeb (2:38:26.800)

Rome, they had a person next to them telling them, don't forget that you are mortal. You know,

Avi Loeb (2:38:32.880)

there was a person with that duty because the Caesars thought that they are all powerful,

Avi Loeb (2:38:37.840)

you know. And they had, for a good reason, someone they hired to whisper in their ear,

Avi Loeb (2:38:47.040)

don't forget that you are mortal. Yeah. Well, you're somebody, one of the most respected,

Avi Loeb (2:38:55.120)

famous scientists in the world, sitting on a farm, gazing up at the stars. So you seem like

Avi Loeb (2:39:00.160)

an appropriate person to ask the completely inappropriate question of, what do you think

Avi Loeb (2:39:05.120)

is the meaning of it all? What's the meaning of life? That's an excellent question. And if we ever

Avi Loeb (2:39:11.040)

find an alien that we can converse with, I would like to answer this. I would like to ask for an

Avi Loeb (2:39:16.560)

answer to this question because... Would they have a different opinion, you think? Well, they might be

Avi Loeb (2:39:21.680)

wiser because they lived around for a while, but I'm afraid they will be silent. I'm afraid they

Avi Loeb (2:39:27.760)

will not have a good answer. And I think it's the process that you should get satisfied by,

Avi Loeb (2:39:38.000)

the process of learning you should enjoy. Okay, so it's not so much that there is a meaning.

Avi Loeb (2:39:45.280)

In fact, there is, as far as I can tell, things just exist, you know. And I think it's inappropriate

Avi Loeb (2:39:55.120)

for us to assign a meaning for our existence because, as a civilization, we will eventually

Avi Loeb (2:40:01.600)

perish and nothing will be... Just another planet on which life died. And if you look at the big

Lex Fridman (2:40:10.080)

scheme of things, who cares? Who cares? And how can we assign significance to what we are doing?

Lex Fridman (2:40:17.520)

So if you said the meaning of life is this, well, it will not be around in a billion years. So

Avi Loeb (2:40:23.600)

it cannot be the meaning of life because nothing will be around. So I think we should just enjoy

Avi Loeb (2:40:31.040)

the process. And it's like many other things in life, you enjoy good food, okay? And you can enjoy

Avi Loeb (2:40:39.920)

learning. Why? Because it makes you appreciate better the environment that you live in.

Lex Fridman (2:40:47.600)

And sometimes people think religion, for example, is in conflict with science, spirituality.

Avi Loeb (2:40:55.760)

That's not true. If you see a watch and you look at it from the outside, you might say,

Avi Loeb (2:41:04.480)

oh, that's interesting. But then if you start to open it up and learn about how it works,

Avi Loeb (2:41:08.800)

you appreciate it more. So science is the way to learn about how the world works. And

Avi Loeb (2:41:14.320)

it's not in conflict to the meaning that you assign to all of this, but it helps you appreciate the

Avi Loeb (2:41:21.440)

world better. So in fact, I would think that a religious person should promote science because

Avi Loeb (2:41:27.120)

it gives you a better appreciation of what's around you. It's like if you buy in a grocery,

Avi Loeb (2:41:34.400)

buy something, a bunch of fruits that are packed together, and you can't see from the outside

Avi Loeb (2:41:42.240)

exactly what kind of fruits are inside. But if you open it up and study, you appreciate better

Avi Loeb (2:41:47.120)

the merchandise that you get, right? So you pay the same amount of money, but at least you know

Avi Loeb (2:41:51.600)

what's inside. So why don't we figure out what the world is about, what the universe contains,

Lex Fridman (2:41:56.400)

what is the dark matter? It will help us appreciate the bigger picture. And then you can assign

Avi Loeb (2:42:02.480)

your own flavor to what it means. Ali, I think I'm truly grateful that a person like you,

Avi Loeb (2:42:11.520)

exists at the center of the scientific community, gives me faith and hope about this big journey

Avi Loeb (2:42:19.440)

that we call science. So thank you for writing the book you wrote recently. You have many other books

Lex Fridman (2:42:26.880)

and articles that I think people should definitely read. And thank you for wasting all this time with

Avi Loeb (2:42:32.400)

me. It's truly an honor. Thank you so much. It was not a waste at all. And thank you for having me.

Avi Loeb (2:42:36.480)

I learned a lot from your questions and your remarks. Thank you. Thank you. Thanks for listening to this

Avi Loeb (2:42:43.120)

conversation with Avi Loeb. And thank you to our sponsors, Zero Fasting App for intermittent

Avi Loeb (2:42:48.400)

fasting, Element Electro Light Drink, Sun Basket Meal Delivery Service, and Pessimist Archive

Avi Loeb (2:42:55.440)

History Podcast. So the choice is a fasting app, fasting fuel, fast breaking, delicious meals,

Lex Fridman (2:43:03.120)

and a history podcast that has very little, as far as I know, to do with fasting. Choose wisely,

Avi Loeb (2:43:09.040)

my friends. And if you wish, click the sponsor links below to get a discount and to support

Avi Loeb (2:43:14.320)

this podcast. And now let me leave you some words from Albert Einstein. The important thing is not

Avi Loeb (2:43:20.480)

to stop questioning. Curiosity has its own reason for existence. One cannot help but be in awe when

Avi Loeb (2:43:27.200)

he contemplates the mysteries of eternity, of life, of the marvelous structure of reality. It is enough

Avi Loeb (2:43:34.160)

if one tries merely to comprehend a little of this mystery every day. Thank you for listening

Lex Fridman (2:43:40.480)

and hope to see you next time.

Avi Loeb (30:03.280)

interesting anecdote. In September this year, 2020, there was another object found,

Lex Fridman (30:13.840)

and it was given the name 2020SO by the Minor Planet Center. This is an organization actually

Avi Loeb (30:22.640)

in Cambridge, Massachusetts, that gives names to astronomical objects found in the solar system.

Lex Fridman (30:28.800)

And they gave it that name 2020SO because, you know, it looked like an object in the solar system

Lex Fridman (30:35.360)

and it moved in an orbit that is similar to the orbit of the Earth, but not the same exactly.

Lex Fridman (30:42.480)

And therefore it was bound to the Sun, but it also exhibited a deviation from what you expect

Avi Loeb (30:49.440)

based on gravity. So the astronomers that found it extrapolated back in time and found that

Avi Loeb (30:55.680)

in 1966, it intercepted the Earth. And then they went to the history books and they realized,

Avi Loeb (31:03.360)

oh, there was a mission called Lunar Lander Surveyor 2 that had a rocket booster. It was

Avi Loeb (31:12.000)

a failed mission, but there was a rocket booster that was kicked into space. And presumably this

Avi Loeb (31:18.240)

is the rocket booster that we're seeing. Now, this rocket booster was sufficiently hollow and thin

Avi Loeb (31:23.680)

for us to recognize that it's pushed by sunlight. So here is my point. We can tell from the orbit

Avi Loeb (31:30.400)

of an object, obviously this object didn't have any cometary tail. It was artificially made. We

Avi Loeb (31:36.480)

know that it was made by us and it did deviate from an orbit of a rock. So just by seeing

Avi Loeb (31:44.320)

something that doesn't have cometary tail and deviates from an orbit shaped by gravity,

Avi Loeb (31:49.520)

we can tell that it's artificial. In the case of Oumuamua, it couldn't have been sent by humans

Avi Loeb (31:55.040)

because it just passed near us for a few months. We know exactly what we were doing at that time.

Lex Fridman (32:01.360)

And also it was moving faster than any object that we can launch. And so obviously it came from

Avi Loeb (32:06.800)

outside the solar system. And the question is who produced it? Now, I should say that when I walk

Avi Loeb (32:13.600)

on vacation on the beach, I often see natural objects like seashells that are beautiful and I

Avi Loeb (32:21.120)

look at them. And every now and then I stumble on a plastic bottle that was artificially produced.

Lex Fridman (32:29.920)

And my point is that maybe Oumuamua was a message in a bottle. And this is simply another window

Avi Loeb (32:37.440)

into searching for artifacts from other civilizations. Where do you think it could have

Avi Loeb (32:43.840)

come from? And if it's so, okay, from a scientific perspective, the narrow minded view, as we'll

Avi Loeb (32:54.240)

probably talk about throughout, is, you know, you kind of want to stick to the things that,

Avi Loeb (33:00.640)

to naturally originating objects like asteroids and comets. Okay, that's the space of possible

Avi Loeb (33:06.640)

hypotheses. And then if we expand beyond that, you start to think, okay, these are artificially

Avi Loeb (33:12.160)

constructed. Like you just said, it could be by humans. It could be by whatever that means,

Avi Loeb (33:19.280)

by some kind of extraterrestrial alien civilizations. If it's the alien civilization

Avi Loeb (33:26.640)

variety, what is this object then? That's an excellent question. And let me lay out,

Avi Loeb (33:34.400)

I mean, we don't have enough evidence to tell. If we had a photograph, perhaps we would have

Avi Loeb (33:38.400)

more information. But there is one other peculiar fact about Oumuamua. Well, other than it was very

Avi Loeb (33:47.440)

shiny, that I didn't mention, you know, we didn't detect any heat from it. And that implies that

Avi Loeb (33:53.120)

it's rather small and shiny. But the other peculiar fact is that it came from a very special frame of

Avi Loeb (34:00.880)

reference. So it's sort of like finding a car in a parking lot, in a public parking lot, that,

Avi Loeb (34:08.480)

you know, you can't really tell where it came from. So there is this frame of reference where

Avi Loeb (34:13.440)

you average over the motions of all the stars in the neighborhood of the Sun. So you find the

Lex Fridman (34:20.800)

so called local standard of rest of the galaxy. And that's a frame of reference that is obtained

Avi Loeb (34:28.480)

by averaging the random motions of all the stars. And the Sun is moving relative to that frame at

Avi Loeb (34:34.080)

some speed. But this object was at rest in that frame. And only one in 500 stars is so much at

Avi Loeb (34:41.840)

rest in that frame. And that's why I was saying it's like a parking lot. It was parked there,

Lex Fridman (34:46.480)

and we bumped into it. So the relative speed between the solar system and this object is just

Avi Loeb (34:52.560)

because we are moving. It was sitting still. Now you ask yourself, why is it so unusual in that

Avi Loeb (34:59.840)

context? You know why? Because if it was expelled from another planetary system, most likely it will

Avi Loeb (35:06.400)

carry the speed of the host star that it came from. Because it was, you know, the most loosely

Avi Loeb (35:12.480)

bound objects are in the periphery of the planetary system, and they move very slowly relative to the

Avi Loeb (35:19.680)

star. And so they carry the, when they are ripped apart from the planetary system, most of the

Avi Loeb (35:24.480)

objects will have the residual motion of the star roughly relative to the local star. But this one

Avi Loeb (35:30.320)

was at rest in the local star. Now, one thing I can think of, if there is a grid of road posts,

Avi Loeb (35:37.840)

you know, like for navigation system, so that you can find your way in the local frame, then that

Avi Loeb (35:44.080)

would be one possibility. These are like little sensors of, that's fascinating to think about. So

Avi Loeb (35:48.800)

there could be, I mean, not necessarily literally a grid, but just evenly, in some definition of

Avi Loeb (35:55.440)

evenly spread out set of objects like these that are just out there. A lot of them. Another

Avi Loeb (36:01.280)

possibility is that these are relay stations, you know, for communication. You might think,

Avi Loeb (36:06.080)

in order to communicate, you need a huge beacon, a very powerful beacon. But it's not true. Because

Avi Loeb (36:12.640)

even on Earth, you know, we have these relay stations. So you have a not so powerful beacon.

Lex Fridman (36:17.520)

So it can be heard only out to a limited distance, but then you relay the message.

Lex Fridman (36:22.880)

And it could be one of those. Now, after it collided with the solar system, of course,

Avi Loeb (36:28.080)

it got a kick. So it's just like a billiard ball, you know, we gave it a kick by colliding with,

Lex Fridman (36:33.760)

but most of them are not colliding with stars. And so that's one possibility. Okay. And there

Avi Loeb (36:38.560)

should be numerous, lots of them, if that's the case. The other possibility is that it's a probe,

Avi Loeb (36:46.240)

you know, that was sent in the direction of the habitable region around the Sun to find out if

Avi Loeb (36:54.960)

there is life. Now, it takes tens of thousands of years for such a probe to traverse the solar

Avi Loeb (37:00.480)

system from the outer edge of the Oort cloud, all the way to where we are. And, you know,

Avi Loeb (37:06.160)

it's a long journey. So when it started the journey from the edge of the solar system to

Avi Loeb (37:09.680)

get to us now, you know, we were rather primitive back then, you know, we still didn't have any

Avi Loeb (37:15.120)

technology, there was no reason to visit, you know, there was grass around and so forth. But,

Avi Loeb (37:20.000)

you know, maybe it is a probe. So you said 10,000 years, that's faster. So it takes that long.

Avi Loeb (37:25.440)

Tens of thousands, yes. Tens of thousands of years. Yeah. Yeah. And the other thing I should

Avi Loeb (37:30.560)

say is, you know, it could be just an outer layer of something else, like, you know, something that

Avi Loeb (37:38.160)

was ripped apart, like a surface of an instrument. And you can have lots of these pieces, you know,

Avi Loeb (37:45.280)

if something breaks, lots of these pieces spread out, like space junk. And, you know, that...

Lex Fridman (37:51.040)

It could be just space junk from an alien civilization.

Avi Loeb (37:56.800)

Yes. So it's kind of...

Lex Fridman (37:59.120)

I should tell you about space junk. Let me...

Lex Fridman (38:01.440)

Yes. What do you mean by space junk?

Avi Loeb (38:03.600)

So, I think, you know, you might ask, why aren't they looking for us? One possibility

Avi Loeb (38:09.760)

is that we are not interesting, like we were talking about ants. Another possibility,

Avi Loeb (38:14.560)

you know, if there are millions or billions of years into their technological development,

Avi Loeb (38:21.760)

they created their own habitat, their own cocoon, where they feel comfortable, they have everything

Avi Loeb (38:28.800)

they need. And it's risky for them to establish communication with other... So they have their

Avi Loeb (38:36.160)

own cocoon and they close off. They don't care about anything else. Now, in that case, you might

Avi Loeb (38:41.600)

say, oh, so how can we find about them if they are closed off? The answer is they still have to

Avi Loeb (38:47.600)

deposit trash, right? That is something from the law of thermodynamics. There must be some production

Avi Loeb (38:53.600)

of trash. And, you know, we can still find about them just like investigative journalists going

Avi Loeb (39:00.480)

through the trash cans of celebrities in Hollywood, you know. You can learn about the private lives

Lex Fridman (39:06.640)

of those celebrities by looking at the trash.

Avi Loeb (39:09.120)

It's fascinating to think, you know, if we are the ants in this picture,

Avi Loeb (39:14.000)

if this thing is a water bottle, or if it's like a smartphone, like where on the spectrum of

Lex Fridman (39:21.040)

possible objects of space, because there's a lot of interesting trash. How interesting is this trash?

Lex Fridman (39:28.640)

But imagine a caveman seeing a cell phone. The caveman would think, since the caveman played

Avi Loeb (39:34.720)

with rocks all of his life, he would say, it's a rock, just like my fellow astronomers said.

Avi Loeb (39:39.680)

Yes, exactly. That's brilliantly put. Actually, as a scientist, do you hope it's a water bottle

Lex Fridman (39:45.360)

or a smartphone?

Avi Loeb (39:46.240)

Because I hope it's even more than a smartphone. I hope that it's something that is really

Avi Loeb (39:51.360)

sophisticated.

Avi Loeb (39:52.240)

That's funny. See, I'm the opposite. I feel like I hope it's a water bottle because

Avi Loeb (39:57.760)

at least we have a hope with our current set of skills to understand it. A caveman has no way of

Avi Loeb (40:03.280)

understanding the smartphone. It's like, it will be like, I feel like a caveman has more to learn

Avi Loeb (40:08.320)

from the plastic water bottle than they do from the smartphone.

Lex Fridman (40:11.360)

But suppose we figure it out. If we, for example, come close to it and learn what it's made of.

Lex Fridman (40:17.840)

And I guess a smartphone is full of like thousands of different technologies that we could

Avi Loeb (40:22.640)

probably pick at. Do you have a sense of where a hypothesis of where is the cocoon that it

Lex Fridman (40:32.800)

might have come from?

Avi Loeb (40:33.600)

No, because, okay, so first of all, you know, the solar system, the outermost edge of the

Avi Loeb (40:40.400)

solar system is called the Oort cloud. It's a cloud of icy rocks of different sizes that were

Avi Loeb (40:49.840)

left over from the formation of the solar system. And it's thought to be roughly a ball or a

Avi Loeb (40:57.520)

sphere. And it's halfway, the extent of it is roughly halfway to the nearest star. Okay, so you

Avi Loeb (41:04.640)

can imagine each planetary system basically touching the Oort clouds of those stars that are

Avi Loeb (41:14.560)

near us are touching each other. Space is full of these billiard balls that are very densely

Avi Loeb (41:22.320)

packed. And what that means is any object that you see, irrespective of whether it came from

Avi Loeb (41:28.480)

the local standard. So we said that this object is special because it came from a local standard

Avi Loeb (41:32.880)

of rest. But even if it didn't, you would never be able to trace where it came from because all

Avi Loeb (41:38.880)

these Oort clouds overlap. So if you take some direction in the sky, you will cross as many

Avi Loeb (41:46.080)

stars as you have in that direction. Like, there is no way to tell which Oort cloud it came from.

Lex Fridman (41:52.240)

So yes, I didn't realize how densely packed everything was from the perspective of the Oort

Avi Loeb (41:57.120)

cloud. And that's really interesting. So yeah, it could be nearby, it could be very far away.

Avi Loeb (42:01.920)

Yeah, we have no clue.

Avi Loeb (42:03.920)

You said cocoon. And you kind of paint, I think in the book, I've read a lot of your articles too

Avi Loeb (42:13.200)

on the Scientific American, which are brilliant. So I'm kind of mixing things up in my head a

Avi Loeb (42:16.720)

little bit. But what does that cocoon look like? What does a civilization that's able to harness

Avi Loeb (42:24.480)

the power of multiple suns, for example, look like? When you imagine possible civilizations that are

Lex Fridman (42:31.680)

a million years more advanced than us, what do you think that actually looks like?

Avi Loeb (42:36.800)

I think it's very different than we can imagine. By the way, I should start from the point that

Avi Loeb (42:42.800)

even biological life, just without technology getting into the game, could look like something

Avi Loeb (42:50.240)

we have never seen before. Take, for example, the nearest star, which is Proxima Centauri.

Avi Loeb (42:55.920)

It's four and a quarter light years away. So they will know about the results of the 2016 elections

Avi Loeb (43:03.040)

only next month, in February 2021. It's very far away. But if you think about it, this star is a

Avi Loeb (43:16.000)

dwarf star, and it's twice as cold as the sun. And it emits mostly infrared radiation. So if there

Avi Loeb (43:26.560)

are any creatures on the planet close to it that is habitable, which is called Proxima B, there is

Avi Loeb (43:34.400)

a planet in the habitable zone, in the zone just at the right distance where, in principle, liquid

Avi Loeb (43:39.120)

water can be on the surface. If there are any animals there, they have infrared eyes because

Avi Loeb (43:45.040)

our eyes were designed to be sensitive to where most of the sunlight is in the visible range.

Lex Fridman (43:51.440)

But Proxima Centauri emits mostly infrared. So in the nearest star system, these animals would be

Avi Loeb (44:00.800)

quite strange. They would have eyes that are detectors of infrared, very different from ours.

Avi Loeb (44:06.480)

Moreover, this planet, Proxima B, faces the star always with the same side. So it has a permanent

Avi Loeb (44:12.880)

day side and a permanent night side. And obviously the creatures that would evolve on the permanent

Avi Loeb (44:19.360)

day side, which is much warmer, would be quite different than those on the permanent night side.

Avi Loeb (44:24.560)

Between them, there would be a permanent sunset strip. And my daughters said that that's the best

Avi Loeb (44:31.280)

opportunity for high value real estate because you will see the sunset throughout your life,

Avi Loeb (44:37.600)

right? The sun never sets on this trip. So these worlds are out of our imagination.

Avi Loeb (44:46.000)

Just even the individual creatures, the sensor suite that they're operating with

Avi Loeb (44:50.240)

might be very different. Very different. So I think when we see something like that,

Avi Loeb (44:53.680)

we would be shocked not to speak about seeing technology. So I don't even dare to imagine.

Lex Fridman (45:01.440)

And I think obviously we can bury our head in the sand and say, it's never aliens,

Avi Loeb (45:07.760)

like many of my colleagues say. And it's a self fulfilling prophecy. If you never look,

Avi Loeb (45:13.360)

you will never find. If you're not ready to find wonderful things, you will never discover them.

Lex Fridman (45:19.360)

And the other thing I would like to say is reality doesn't care whether you ignore it or not.

Avi Loeb (45:25.360)

You can ignore reality, but it's still there. So we can all agree, based on Twitter,

Avi Loeb (45:32.560)

that aliens don't exist. That Umuamua was a rock. We can all agree. And you will get a lot of likes,

Avi Loeb (45:39.600)

we will have a big crowd of supporters, and everyone will be happy and give each other

Avi Loeb (45:44.480)

awards and honors and so forth. But Umuamua might still be an alien artifact. Who cares

Lex Fridman (45:51.920)

what humans agree on? There is a reality out there. And we have to be modest enough to recognize

Avi Loeb (45:59.680)

that we should make our statements based on evidence. Science is not about ourselves. It's

Avi Loeb (46:06.400)

not about glorifying our image. It's not about getting honors, prizes. A lot of the academic

Avi Loeb (46:14.160)

activity is geared towards creating your echo chamber where you have students, postdocs,

Avi Loeb (46:19.680)

repeating your mantras so that your voice is heard loudly so that you can get more honors,

Avi Loeb (46:25.120)

prizes, recognition. That's not the purpose of science. The purpose is to figure out what nature

Avi Loeb (46:31.600)

is. And in the process of doing that, it's a learning experience. You make mistakes. Einstein

Avi Loeb (46:37.840)

made three mistakes at the end of his career. He argued that in the 1930s, he argued that black

Avi Loeb (46:44.080)

holes don't exist, gravitational waves don't exist, and quantum mechanics doesn't have spooky action

Avi Loeb (46:52.400)

at a distance. And all three turned out to be wrong. So the point is that if you work at the

Avi Loeb (46:58.400)

frontier, then you make mistakes. It's inevitable because you can't tell what is true or not.

Lex Fridman (47:04.000)

And avoiding making mistakes in order to preserve your image makes you extremely boring. You will

Avi Loeb (47:10.640)

get a prize, but you will be a boring scientist because you will keep repeating things we already

Avi Loeb (47:16.480)

know. If you want to make progress, if you want to innovate, you have to take risks and you have

Avi Loeb (47:22.160)

to look at the evidence. It's a dialogue with nature. You don't know the truth in advance. You

Avi Loeb (47:28.480)

let nature tell you, educate you, and then you realize that what you thought before is incorrect.

Lex Fridman (47:35.440)

And a lot of my colleagues prefer to be in a state where they have a monologue. You know,

Avi Loeb (47:40.960)

if you look at these people that work on string theory, they have a monologue. They know what,

Lex Fridman (47:46.160)

and in fact, their monologue is centered on anti de Sitter space, which we don't live in now.

Avi Loeb (47:53.440)

To me, it's just like the Olympics. You define a hundred meters and you say,

Avi Loeb (47:57.840)

whoever runs these hundred meters is the best athlete, the fastest. And it's completely

Avi Loeb (48:03.920)

arbitrary. You could have decided it would be 50 meters or 20 meters. Who cares? You just measure

Avi Loeb (48:09.680)

the ability of people this way. So you define anti de Sitter space as a space where you do your

Avi Loeb (48:14.560)

mathematical gymnastics, and then you find who can do it the best. And you give jobs based on that.

Avi Loeb (48:19.680)

You give prizes. But as we said before, you know, nature doesn't care about, you know,

Avi Loeb (48:25.280)

the prizes that you give to each other. It cares, you know, it has its own reality and we should

Avi Loeb (48:32.160)

figure it out. And it's not about us. The scientific activity is about figuring out nature. And

Avi Loeb (48:37.760)

sometimes we may be wrong. Our image will not be preserved. But that's the fun, you know. Kids

Avi Loeb (48:46.560)

explore the world out of curiosity. And I always want to maintain my childhood curiosity. And I

Avi Loeb (48:52.960)

don't care about the labels that I have. In fact, having tenure is exactly the opportunity to behave

Avi Loeb (48:59.840)

like a child because you can make mistakes. And I was asked by the Harvard Gazette, you know,

Lex Fridman (49:05.360)

the Pravda of Harvard, what is the one thing that you would like to change about the world?

Lex Fridman (49:14.800)

And I said, I would like my colleagues to behave more like kids. That's the one thing I would like

Avi Loeb (49:21.120)

them to do. Because something bad happens to these kids when they become tenured professors.

Avi Loeb (49:27.520)

They start to worry about their ego and about themselves more than about the purpose of science,

Avi Loeb (49:33.440)

which is, you know, curiosity driven, figuring out from evidence. Evidence is the key. So when

Avi Loeb (49:38.960)

an object shows anomalies like Oumuamua, what's the problem discussing, you know, whether it's

Avi Loeb (49:44.800)

artificial or not? You know, so there was, I should tell you, there was a mainstream

Avi Loeb (49:49.280)

paper in Nature published saying it must be natural. That's it. It's unusual, but it must

Avi Loeb (49:56.240)

be natural, period. And then at the same time, some other mainstream scientists tried to explain

Lex Fridman (50:04.880)

the properties. And they came up with interpretations like it's a dust bunny,

Avi Loeb (50:09.920)

you know, the kind that you find in a household, a collection of dust particles pushed by sunlight,

Avi Loeb (50:16.240)

something we have never seen before. Or it's a hydrogen iceberg. It actually evaporates like

Avi Loeb (50:21.760)

a comet, but hydrogen is transparent. You don't see it. And that's why we don't see the cometary

Avi Loeb (50:26.560)

tail. Again, we have never seen something like that. In both cases, the objects would not

Avi Loeb (50:31.760)

survive the long journey. We discussed it in a paper that I wrote afterwards. But my point is,

Avi Loeb (50:37.920)

those that tried to explain the unusual properties went into great length at discussing things that

Avi Loeb (50:44.720)

we have never seen before. Okay? So even when you think about a natural origin, you have to come up

Avi Loeb (50:50.480)

with scenarios of things that were never seen before. And by the way, they look less plausible

Avi Loeb (50:57.120)

to me personally. But my point is, if we discuss things that were never seen before,

Lex Fridman (51:03.520)

why not discuss, why not contemplate an artificial origin? What's the problem?

Lex Fridman (51:07.840)

Why do people have this pushback? You know, I worked on dark matter, and we don't know what

Avi Loeb (51:16.160)

most of the matter in the universe is. It's called dark matter. It's just an acronym because we have

Avi Loeb (51:22.160)

no clue. We simply don't know. So it could be all kinds of particles. And over the years, people

Avi Loeb (51:26.800)

suggested weakly interacting massive particles, axions, all kinds of particles. And experiments

Avi Loeb (51:32.560)

were made. They cost hundreds of millions of dollars. They put upper limits, constraints

Avi Loeb (51:38.880)

that ruled out many of the possibilities that were proposed as natural initially. The mainstream

Avi Loeb (51:44.560)

community regarded it as a mainstream activity to search the nature of the dark matter.

Lex Fridman (51:50.400)

And nobody complained that it's speculative to consider weakly interacting massive particles.

Avi Loeb (51:56.160)

Now, I ask you, why is it speculative to consider extraterrestrial technologies? We have a proof

Avi Loeb (52:04.320)

that it exists here on Earth. We also know that the conditions of Earth are reproduced

Avi Loeb (52:10.720)

in billions of systems throughout the Milky Way galaxy. So what's more conservative than to say,

Avi Loeb (52:16.480)

if you arrange for similar conditions, you get the same outcome. How can you imagine this to be

Avi Loeb (52:22.320)

speculative? It's not speculative at all. And nevertheless, it's regarded the periphery. And

Avi Loeb (52:26.800)

at the same time, you have physicists, theoretical physicists, working on extra dimensions, super

Avi Loeb (52:32.320)

symmetry, super string theory, the multiverse. Maybe we live in a simulation. All of these ideas

Avi Loeb (52:39.520)

that have no grounding in reality, some of which sound to me like, you know, just like what someone

Avi Loeb (52:47.280)

would say. Science fiction, basically. Because you have no way to test it, you know, through

Avi Loeb (52:54.880)

experiments. And experiments really are key. It's not just the nuance. You say, okay, forget about

Lex Fridman (52:59.920)

experiments. As some philosophers try to say, you know, if there is a consensus, what's the problem?

Avi Loeb (53:04.640)

The point is, it's key. Then that's what Galileo found. It's key to have feedback from reality.

Avi Loeb (53:10.320)

You know, you can think that you have a billion dollars or that you are more rich than, you know,

Avi Loeb (53:16.240)

Elon Musk. That's fine. You can feel very happy about it. You can talk about it with your friends

Lex Fridman (53:22.400)

and all of you will be happy and think about what you can do with the money. Then you go to

Avi Loeb (53:26.320)

an ATM machine and you make an experiment. You check how much money you have in your checking

Avi Loeb (53:31.040)

account. And if it turns out that, you know, you don't have much, you can't materialize your dreams.

Avi Loeb (53:39.200)

Okay. So you realize, you have a reality check. And my point is, without experiments giving you

Avi Loeb (53:44.480)

a reality check, without the ATM machine showing you whether your ideas are bankrupt or not,

Avi Loeb (53:49.520)

without putting skin in the game. And by skin in the game, I mean, don't just talk about

Avi Loeb (53:55.200)

theoretical ideas. Make them testable. If you don't make them testable, they're worthless.

Avi Loeb (54:01.440)

They're just like theology that is not testable. By the way, theology has some tests. Let me give you

Avi Loeb (54:09.760)

three examples. It turns out that my book already inspired a PhD student at Harvard in the English

Avi Loeb (54:17.760)

department to pursue a PhD in that direction. And she invited me to the PhD exam a couple of months

Avi Loeb (54:25.920)

ago. And in the exam, one of the examiners, a professor, asked her, do you know why Giordano

Avi Loeb (54:34.800)

Bruno was burnt at the stake? And she said, no, I think it's because he was an obnoxious

Avi Loeb (54:42.080)

guy and irritated a lot of people, which is true. But the professor said, no,

Lex Fridman (54:50.000)

it's because Giordano Bruno said that other stars are just like the sun,

Lex Fridman (54:56.720)

and they could have a planet like the Earth around them that could host life. And that

Avi Loeb (55:03.840)

was offensive to the church. Why was it offensive? Because there is the possibility that this life

Avi Loeb (55:09.600)

sinned. And if that life sinned on planets around other stars, it should have been saved by Christ.

Lex Fridman (55:18.720)

And then you need multiple copies of Christ. And that's unacceptable. How can you have duplicates

Avi Loeb (55:25.440)

of Christ? And so they burned the guy. I'm just like loading this all in because that's kind of

Avi Loeb (55:34.320)

brilliant. So he was actually already, it's not just about the stars, it's anticipating that there

Lex Fridman (55:39.600)

could be other life forms. Like why, if this star, if there's other stars, why would it be special?

Lex Fridman (55:46.080)

Why would our star be special? He was making the right argument. And he would just follow that

Avi Loeb (55:51.040)

all along to say like, there should be other Earth like places, there should be other life forms.

Lex Fridman (55:56.240)

And then there needs to be copies of Christ. Yeah, so that was offensive. So I said to that

Avi Loeb (56:02.000)

professor, I said, great, I wanted to introduce some scientific tone to the discussion. And I said,

Avi Loeb (56:08.800)

this is great because now you basically laid the foundation for an experimental test of this

Avi Loeb (56:13.680)

theology. What is the test? We now know that other stars are like the sun and we know they have

Avi Loeb (56:20.000)

planets like the Earth around them. So suppose we find life there and we figure out that they sinned,

Avi Loeb (56:26.400)

then we ask them, did you witness Christ? And if they say no, it means that this theology

Avi Loeb (56:33.920)

is ruled out. So there is an experimental test. So this is experimental test number one.

Avi Loeb (56:38.880)

Another experimental test, in the Bible, in the Old Testament, Abraham

Avi Loeb (56:46.400)

was heard the voice, the voice of God to sacrifice his son, right? Only son. And that's what the

Avi Loeb (56:56.000)

story says. Now, suppose Abraham, my name, by the way, had a voice memo up on his cell phone. He

Avi Loeb (57:04.960)

could have pressed this up and recorded the voice of God. And that would have been experimental

Lex Fridman (57:10.320)

evidence that God exists, right? Fortunately, he didn't, but it's an experimental test, right?

Avi Loeb (57:18.000)

There is a third example I should tell, and that is Elie Wiesel attributed this story to Martin

Avi Loeb (57:24.400)

Buber, but it's not clear whether it's true or not. At any event, the story goes that Martin

Avi Loeb (57:30.160)

Buber, you know, he was a philosopher and he said, you know, the Christians, you know,

Avi Loeb (57:36.240)

the Messiah arrived already and will come back again in the future. The Jews argue the Messiah

Avi Loeb (57:44.880)

never came and will arrive in the future. So he said, why argue? Both sides agree that the Messiah

Avi Loeb (57:54.400)

will arrive in the future. When the Messiah arrives, we can ask whether he or she will arrive

Avi Loeb (58:01.360)

in the future. When the Messiah arrives, we can ask whether he or she came before, you know, like

Avi Loeb (58:09.520)

visited us and then figure it out. And one side. So again, experimental test of a theology. So even

Lex Fridman (58:16.080)

theology, if it puts a skin in the game, you know, if it makes a prediction, could be tested, right?

Lex Fridman (58:22.800)

So why can't string theories test themselves? Or why can't, you know, even cosmic inflation? That's

Avi Loeb (58:28.880)

a model that, you know, one of the inventors from MIT, Alan Guth, argues that it's not falsifiable.

Avi Loeb (58:35.840)

My point is a theory that cannot be falsified is not helpful because it means that you can't

Avi Loeb (58:41.920)

make progress. You cannot improve your understanding of nature. The only way for us to

Avi Loeb (58:46.800)

learn about nature is by making hypotheses that are testable, doing the experiments and learning

Avi Loeb (58:53.360)

whether we are correct or not. So B, and coupled that with a curiosity and open mindedness that

Avi Loeb (58:59.440)

allows us to explore all kinds of possible hypotheses, but always the pursuit of those,

Avi Loeb (59:06.880)

the scientific rigor around those hypotheses is ultimately get evidence. Knowledge of what nature

Avi Loeb (59:15.120)

is should be a dialogue with nature. Yes. Rather than a monologue. Monologue, beautifully put.

Avi Loeb (59:20.400)

Can we talk a little bit about the Drake equation? Another framework from which to have this kind of

Avi Loeb (59:25.760)

discussion about possible civilizations out there. So let me ask, within the context of the Drake

Lex Fridman (59:31.680)

equation or maybe bigger, how many alien civilizations do you think are out there?

Avi Loeb (59:37.200)

Well, it's hard to tell because the Drake equation is again quantifying our ignorance. It's just a set

Avi Loeb (59:42.640)

of factors. The only one that we know, or actually two that we know quite well is the rate of star

Avi Loeb (59:50.240)

formation in the Milky Way galaxy, which we measured by now, and the frequency of planets

Avi Loeb (59:56.880)

like the Earth around stars and at the right distance to have life. But other than that,