Harry Cliff: Particle Physics and the Large Hadron Collider
物理与宇宙学音乐与艺术AI 与机器学习技术与编程政治与社会
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🔑 关键词
particlesfieldforcehiggsparticledoncalledmattertheorylhcquarkselectrondatauniversefieldsquarkenergyphysicsmadetogether
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🎙️ 完整对话（2514 条）
Lex Fridman (00:00.000)
The following is a conversation with Harry Cliff,
以下是与哈利·克里夫的对话，
Lex Fridman (00:03.000)
a particle physicist at the University of Cambridge,
剑桥大学的粒子物理学家，
Lex Fridman (00:05.760)
working on the Large Hadron Collider beauty experiment
致力于大型强子对撞机美丽实验
Lex Fridman (00:09.840)
that specializes in investigating the slight differences
专门研究细微的差异
Lex Fridman (00:13.000)
between matter and antimatter
物质与反物质之间
Harry Cliff (00:15.280)
by studying a type of particle called the beauty quark
通过研究一种称为美夸克的粒子
Lex Fridman (00:18.400)
or b quark.
或 b 夸克。
Harry Cliff (00:19.880)
In this way, he's part of the group of physicists
这样，他就成为物理学家群体中的一员了
Lex Fridman (00:22.280)
who are searching for the evidence of new particles
他们正在寻找新粒子的证据
Harry Cliff (00:25.120)
that can answer some of the biggest questions
可以回答一些最大的问题
Lex Fridman (00:26.920)
in modern physics.
在现代物理学中。
Harry Cliff (00:28.280)
He's also an exceptional communicator of science
他也是一位杰出的科学传播者
Lex Fridman (00:31.840)
with some of the clearest and most captivating explanations
一些最清晰、最吸引人的解释
Harry Cliff (00:34.880)
of basic concepts in particle physicists
粒子物理学家的基本概念
Lex Fridman (00:37.440)
that I've ever heard.
我听说过。
Lex Fridman (00:39.560)
So when I visited London, I knew I had to talk to him.
所以当我访问伦敦时，我知道我必须和他谈谈。
Lex Fridman (00:42.960)
And we did this conversation
我们进行了这次对话
Harry Cliff (00:44.920)
at the Royal Institute Lecture Theatre,
在皇家学院演讲厅，
Lex Fridman (00:47.280)
which has hosted lectures for over two centuries
举办讲座已有两个多世纪
Harry Cliff (00:50.520)
from some of the greatest scientists
来自一些最伟大的科学家
Lex Fridman (00:52.120)
and science communicators in history,
Harry Cliff (00:54.160)
from Michael Faraday to Carl Sagan.
Lex Fridman (00:57.680)
This conversation was recorded
Harry Cliff (00:59.080)
before the outbreak of the pandemic.
Lex Fridman (01:01.240)
For everyone feeling the medical and psychological
Lex Fridman (01:03.440)
and financial burden of this crisis,
Lex Fridman (01:05.440)
I'm sending love your way.
Harry Cliff (01:07.360)
Stay strong.
Lex Fridman (01:08.400)
We're in this together.
Harry Cliff (01:09.560)
We'll beat this thing.
Lex Fridman (01:11.160)
This is the Artificial Intelligence Podcast.
Harry Cliff (01:13.840)
If you enjoy it, subscribe on YouTube,
Lex Fridman (01:15.920)
review it with five stars on Apple Podcast,
Harry Cliff (01:18.320)
support it on Patreon,
Lex Fridman (01:19.520)
or simply connect with me on Twitter
Harry Cliff (01:21.400)
at Lex Friedman, spelled F R I D M A N.
Lex Fridman (01:25.080)
As usual, I'll do a few minutes of ads now
Lex Fridman (01:27.120)
and never any ads in the middle
Lex Fridman (01:28.400)
that can break the flow of the conversation.
Harry Cliff (01:30.560)
I hope that works for you
Lex Fridman (01:31.880)
and doesn't hurt the listening experience.
Harry Cliff (01:35.040)
Quick summary of the ads.
Lex Fridman (01:36.480)
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Harry Cliff (01:40.000)
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Lex Fridman (01:41.680)
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Lex Fridman (01:46.720)
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Lex Fridman (01:50.880)
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Harry Cliff (01:52.800)
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Lex Fridman (01:55.200)
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Harry Cliff (01:58.400)
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Lex Fridman (02:01.280)
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Harry Cliff (02:04.480)
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Harry Cliff (02:09.600)
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Lex Fridman (02:11.000)
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Harry Cliff (02:13.720)
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Lex Fridman (02:15.800)
So big props to the Cash App engineers
Harry Cliff (02:17.720)
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Lex Fridman (02:20.200)
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Harry Cliff (02:22.680)
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Lex Fridman (02:25.720)
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Lex Fridman (02:28.560)
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Lex Fridman (02:31.480)
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Lex Fridman (02:34.840)
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Lex Fridman (02:38.400)
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Harry Cliff (02:41.520)
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Lex Fridman (02:43.960)
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Harry Cliff (02:47.880)
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Lex Fridman (02:50.720)
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Harry Cliff (02:54.720)
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Lex Fridman (02:57.600)
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Harry Cliff (03:01.240)
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Lex Fridman (03:04.080)
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Lex Fridman (03:05.960)
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Lex Fridman (03:08.360)
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Harry Cliff (03:11.360)
I might be in Boston now, but I can make it look
Lex Fridman (03:13.880)
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Harry Cliff (03:17.700)
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Lex Fridman (03:20.180)
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Harry Cliff (03:23.380)
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Lex Fridman (03:26.380)
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Harry Cliff (03:28.460)
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Lex Fridman (03:31.380)
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Lex Fridman (03:35.780)
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Lex Fridman (03:38.100)
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Harry Cliff (03:43.100)
to get a discount and to support this podcast.
Lex Fridman (03:46.580)
And now, here's my conversation with Harry Kliff.
Harry Cliff (03:51.900)
Let's start with probably one of the coolest things
Lex Fridman (03:54.160)
that human beings have ever created,
Harry Cliff (03:56.140)
the Large Hadron Collider, OHC.
Lex Fridman (04:00.000)
What is it?
Lex Fridman (04:00.940)
How does it work?
Lex Fridman (04:02.180)
Okay, so it's essentially this gigantic
Harry Cliff (04:05.260)
27 kilometer circumference particle accelerator.
Lex Fridman (04:08.340)
It's this big ring.
Harry Cliff (04:09.540)
It's buried about 100 meters underneath the surface
Lex Fridman (04:12.100)
in the countryside just outside Geneva in Switzerland.
Lex Fridman (04:14.700)
And really what it's for, ultimately,
Lex Fridman (04:17.060)
is to try to understand what are the basic building blocks
Harry Cliff (04:20.380)
of the universe.
Lex Fridman (04:21.640)
So you can think of it in a way
Harry Cliff (04:23.060)
as like a gigantic microscope,
Lex Fridman (04:24.540)
and the analogy is actually fairly precise, so.
Harry Cliff (04:28.500)
Gigantic microscope.
Lex Fridman (04:30.060)
Effectively, except it's a microscope
Harry Cliff (04:32.580)
that looks at the structure of the vacuum.
Lex Fridman (04:36.180)
In order for this kind of thing to study particles,
Harry Cliff (04:40.500)
which are the microscopic entities, it has to be huge.
Lex Fridman (04:44.420)
It's a gigantic microscope.
Lex Fridman (04:45.780)
So what do you mean by studying vacuum?
Lex Fridman (04:48.580)
Okay, so I mean, so particle physics as a field
Harry Cliff (04:51.960)
is kind of badly named in a way,
Lex Fridman (04:53.460)
because particles are not the fundamental ingredients
Harry Cliff (04:56.620)
of the universe.
Lex Fridman (04:57.740)
They're not fundamental at all.
Lex Fridman (04:58.940)
So the things that we believe
Lex Fridman (05:00.180)
are the real building blocks of the universe
Harry Cliff (05:02.340)
are objects, invisible fluid like objects
Lex Fridman (05:05.420)
called quantum fields.
Lex Fridman (05:07.420)
So these are fields like the magnetic field
Lex Fridman (05:10.200)
around a magnet that exists everywhere in space.
Harry Cliff (05:12.620)
They're always there.
Lex Fridman (05:13.620)
In fact, actually, it's funny that we're
Harry Cliff (05:15.020)
in the Royal Institution,
Lex Fridman (05:15.860)
because this is where the idea of the field
Harry Cliff (05:19.000)
was effectively invented by Michael Faraday
Lex Fridman (05:21.260)
doing experiments with magnets and coils of wire.
Lex Fridman (05:23.840)
So he noticed that, you know,
Lex Fridman (05:26.060)
it was a very famous experiment that he did
Harry Cliff (05:28.420)
where he got a magnet and put on top of it a piece of paper
Lex Fridman (05:31.220)
and then sprinkled iron filings.
Lex Fridman (05:32.680)
And he found the iron filings arranged themselves
Lex Fridman (05:34.620)
into these kind of loops,
Harry Cliff (05:37.460)
which was actually mapping out the invisible influence
Lex Fridman (05:40.300)
of this magnetic field, which is a thing, you know,
Harry Cliff (05:42.400)
we've all experienced, we've all felt, held a magnet
Lex Fridman (05:44.740)
or two poles of magnet and pushed them together
Lex Fridman (05:46.500)
and felt this thing, this force pushing back.
Lex Fridman (05:48.620)
So these are real physical objects.
Lex Fridman (05:51.020)
And the way we think of particles in modern physics
Lex Fridman (05:53.820)
is that they are essentially little vibrations,
Harry Cliff (05:56.660)
little ripples in these otherwise invisible fields
Lex Fridman (06:00.260)
that are everywhere.
Harry Cliff (06:01.420)
They fill the whole universe.
Lex Fridman (06:03.260)
You know, I don't, I apologize perhaps
Harry Cliff (06:05.860)
for the ridiculous question.
Lex Fridman (06:07.420)
Are you comfortable with the idea
Lex Fridman (06:10.240)
of the fundamental nature of our reality being fields?
Lex Fridman (06:14.140)
Because to me, particles, you know,
Harry Cliff (06:17.540)
a bunch of different building blocks makes more sense
Lex Fridman (06:20.620)
sort of intellectually, sort of visually,
Harry Cliff (06:22.600)
like it seems to, I seem to be able to visualize
Lex Fridman (06:26.680)
that kind of idea easier.
Harry Cliff (06:28.620)
Are you comfortable psychologically with the idea
Lex Fridman (06:31.740)
that the basic building block is not a block, but a field?
Harry Cliff (06:35.300)
I think it's, I think it's quite a magical idea.
Lex Fridman (06:38.220)
I find it quite appealing.
Lex Fridman (06:39.400)
And it's, well, it comes from a misunderstanding
Lex Fridman (06:42.020)
of what particles are.
Lex Fridman (06:43.180)
So like when you, when we do science at school
Lex Fridman (06:45.460)
and we draw a picture of an atom,
Harry Cliff (06:46.740)
you draw like, you know, a nucleus with some protons
Lex Fridman (06:49.180)
and neutrons, these little spheres in the middle,
Lex Fridman (06:50.940)
and then you have some electrons that are like little flies
Lex Fridman (06:53.540)
flying around the atom.
Lex Fridman (06:54.820)
And that is a completely misleading picture
Lex Fridman (06:56.460)
of what an atom is like.
Harry Cliff (06:57.700)
It's nothing like that.
Lex Fridman (06:58.540)
The electron is not like a little planet orbiting the atom.
Harry Cliff (07:01.980)
It's this spread out, wibbly wobbly wave like thing.
Lex Fridman (07:05.900)
And we know we've known that since, you know,
Harry Cliff (07:07.420)
the early 20th century, thanks to quantum mechanics.
Lex Fridman (07:10.140)
So when we, we, we carry on using this word particle
Harry Cliff (07:13.220)
because sometimes when we do experiments,
Lex Fridman (07:15.780)
particles do behave like they're little marbles
Harry Cliff (07:17.980)
or little bullets, you know.
Lex Fridman (07:19.260)
So in the LHC, when we collide particles together,
Harry Cliff (07:22.580)
you'll get, you know, you'll get like hundreds of particles
Lex Fridman (07:25.080)
all flying out through the detector
Lex Fridman (07:26.300)
and they all take a trajectory and you can see
Lex Fridman (07:28.660)
from the detector where they've gone
Lex Fridman (07:29.940)
and they look like they're little bullets.
Lex Fridman (07:31.420)
So they behave that way, you know, a lot of the time.
Harry Cliff (07:35.380)
When you really study them carefully,
Lex Fridman (07:37.620)
you'll see that they are not little spheres.
Harry Cliff (07:40.100)
They are these ethereal disturbances
Lex Fridman (07:43.220)
in these underlying fields.
Lex Fridman (07:44.940)
So this is really how we think nature is,
Lex Fridman (07:48.460)
which is surprising, but also I think kind of magic.
Harry Cliff (07:51.640)
So, you know, we are, our bodies are basically made up
Lex Fridman (07:54.580)
of like little knots of energy
Harry Cliff (07:56.860)
in these invisible objects that are all around us.
Lex Fridman (08:00.280)
And what is the story of the vacuum when it comes to LHC?
Lex Fridman (08:07.760)
So why did you mention the word vacuum?
Lex Fridman (08:09.920)
Okay, so if we just, if we go back to like the physics,
Harry Cliff (08:13.040)
we do know.
Lex Fridman (08:13.920)
So atoms are made of electrons,
Harry Cliff (08:16.320)
which were discovered a hundred or so years ago.
Lex Fridman (08:18.260)
And then in the nucleus of the atom,
Harry Cliff (08:20.000)
you have two other types of particles.
Lex Fridman (08:21.720)
There's an up, something called an up quark
Lex Fridman (08:23.480)
and a down quark.
Lex Fridman (08:24.420)
And those three particles make up every atom in the universe.
Lex Fridman (08:27.920)
So we think of these as ripples in fields.
Lex Fridman (08:30.640)
So there is something called the electron field
Lex Fridman (08:34.300)
and every electron in the universe is a ripple moving
Lex Fridman (08:37.440)
about in this electron field.
Lex Fridman (08:39.080)
So the electron field is all around us, we can't see it,
Lex Fridman (08:40.800)
but every electron in our body is a little ripple
Harry Cliff (08:42.920)
in this thing that's there all the time.
Lex Fridman (08:45.600)
And the quark fields are the same.
Lex Fridman (08:46.960)
So there's an up quark field and an up quark
Lex Fridman (08:48.960)
is a little ripple in the up quark field.
Lex Fridman (08:50.240)
And the down quark is a little ripple
Lex Fridman (08:51.720)
in something else called the down quark field.
Lex Fridman (08:53.340)
So these fields are always there.
Lex Fridman (08:55.000)
Now there are potentially, we know about a certain number
Harry Cliff (08:58.880)
of fields in what we call the standard model
Lex Fridman (09:00.440)
of particle physics.
Lex Fridman (09:01.320)
And the most recent one we discovered was the Higgs field.
Lex Fridman (09:04.040)
And the way we discovered the Higgs field
Harry Cliff (09:07.080)
was to make a little ripple in it.
Lex Fridman (09:08.620)
So what the LHC did, it fired two protons into each other,
Harry Cliff (09:12.520)
very, very hard with enough energy
Lex Fridman (09:14.920)
that you could create a disturbance in this Higgs field.
Lex Fridman (09:18.460)
And that's what shows up as what we call the Higgs boson.
Lex Fridman (09:20.840)
So this particle that everyone was going on about
Harry Cliff (09:22.940)
eight or so years ago is proof really,
Lex Fridman (09:25.800)
the particle in itself is, I mean, it's interesting,
Lex Fridman (09:28.500)
but the thing that's really interesting is the field.
Lex Fridman (09:30.620)
Because it's the Higgs field that we believe
Harry Cliff (09:33.900)
is the reason that electrons and quarks have mass.
Lex Fridman (09:38.280)
And it's that invisible field that's always there
Harry Cliff (09:41.000)
that gives mass to the particles.
Lex Fridman (09:42.480)
The Higgs boson is just our way
Harry Cliff (09:44.360)
of checking it's there basically.
Lex Fridman (09:46.340)
And so the Large Hadron Collider,
Harry Cliff (09:49.160)
in order to get that ripple in the Higgs field,
Lex Fridman (09:51.900)
it requires a huge amount of energy.
Harry Cliff (09:54.380)
Yeah, I suppose.
Lex Fridman (09:55.220)
And so that's why you need this huge,
Harry Cliff (09:57.000)
that's why size matters here.
Lex Fridman (09:58.360)
So maybe there's a million questions here,
Lex Fridman (10:01.440)
but let's backtrack.
Lex Fridman (10:02.640)
Why does size matter in the context of a particle collider?
Lex Fridman (10:09.960)
So why does bigger allow you for higher energy collisions?
Lex Fridman (10:15.760)
Right, so the reason, well, it's kind of simple really,
Harry Cliff (10:18.500)
which is that there are two types of particle accelerator
Lex Fridman (10:21.080)
that you can build.
Harry Cliff (10:21.920)
One is circular, which is like the LHC,
Lex Fridman (10:23.640)
the other is a great long line.
Lex Fridman (10:25.680)
So the advantage of a circular machine
Lex Fridman (10:28.560)
is that you can send particles around a ring
Lex Fridman (10:30.580)
and you can give them a kick every time they go around.
Lex Fridman (10:32.560)
So imagine you have a, there's actually a bit of the LHC,
Harry Cliff (10:34.700)
that's about only 30 meters long,
Lex Fridman (10:36.800)
where you have a bunch of metal boxes,
Harry Cliff (10:38.720)
which have oscillating 2 million volt electric fields
Lex Fridman (10:41.800)
inside them, which are timed so that when a proton
Harry Cliff (10:44.360)
goes through one of these boxes,
Lex Fridman (10:45.560)
the field it sees as it approaches is attractive.
Lex Fridman (10:48.240)
And then as it leaves the box,
Lex Fridman (10:49.200)
it flips and becomes repulsive
Lex Fridman (10:51.240)
and the proton gets attracted
Lex Fridman (10:52.520)
and kicked out the other side, so it gets a bit faster.
Lex Fridman (10:55.060)
So you send it, and then you send it back round again.
Lex Fridman (10:57.160)
And it's incredible, like the timing of that,
Lex Fridman (10:59.440)
the synchronization, wait, really?
Lex Fridman (11:01.160)
Yeah, yeah, yeah, yeah.
Harry Cliff (11:02.760)
I think there's going to be a multiplicative effect
Lex Fridman (11:05.520)
on the questions I have.
Harry Cliff (11:06.720)
Is, okay, let me just take that attention for a second.
Lex Fridman (11:12.520)
The orchestration of that, is that fundamentally
Lex Fridman (11:15.120)
a hardware problem or a software problem?
Lex Fridman (11:17.600)
Like what, how do you get that?
Harry Cliff (11:20.120)
I mean, I should first of all say, I'm not an engineer.
Lex Fridman (11:22.680)
So the guys, I did not build the LHC,
Lex Fridman (11:24.640)
so they're people much, much better at this stuff than I.
Lex Fridman (11:26.840)
For sure, but maybe.
Lex Fridman (11:30.120)
But from your sort of intuition,
Lex Fridman (11:33.680)
from the echoes of what you understand,
Lex Fridman (11:37.440)
what you heard of how it's designed, what's your sense?
Lex Fridman (11:40.560)
What's the engineering aspects of it?
Harry Cliff (11:43.360)
The acceleration bit is not challenging.
Lex Fridman (11:45.400)
Okay, I mean, okay, there's always challenges
Harry Cliff (11:47.120)
with everything, but basically you have these,
Lex Fridman (11:50.280)
the beams that go around the LHC, the beams of particles
Harry Cliff (11:53.600)
are divided into little bunches.
Lex Fridman (11:55.480)
So they're called, they're a bit like swarms of bees,
Harry Cliff (11:57.800)
if you like, and there are around,
Lex Fridman (12:00.280)
I think it's something of the order 2000 bunches
Harry Cliff (12:04.040)
spaced around the ring.
Lex Fridman (12:05.280)
And they, if you're at a given point on the ring,
Harry Cliff (12:07.800)
counting bunches, you get 40 million bunches
Lex Fridman (12:10.120)
passing you every second.
Lex Fridman (12:11.240)
So they come in like cars going past
Lex Fridman (12:14.200)
on a very fast motorway.
Lex Fridman (12:16.000)
So you need to have, if you're an electric field
Lex Fridman (12:18.280)
that you're using to accelerate the particles,
Harry Cliff (12:20.400)
that needs to be timed so that as a bunch of protons arrives,
Lex Fridman (12:23.800)
it's got the right sign to attract them
Lex Fridman (12:26.080)
and then flips at the right moment.
Lex Fridman (12:27.600)
But I think the voltage in those boxes
Harry Cliff (12:29.600)
oscillates at hundreds of megahertz.
Lex Fridman (12:31.200)
So the beams are like 40 megahertz,
Lex Fridman (12:33.280)
but it's oscillating much more quickly than the beam.
Lex Fridman (12:35.200)
So I think it's difficult engineering,
Lex Fridman (12:37.640)
but in principle, it's not a really serious challenge.
Lex Fridman (12:41.480)
The bigger problem.
Harry Cliff (12:42.320)
There's probably engineers like screaming at you right now.
Lex Fridman (12:44.600)
Probably, but I mean, okay.
Lex Fridman (12:46.400)
So in terms of coming back to this thing,
Lex Fridman (12:47.880)
why is it so big?
Harry Cliff (12:48.760)
Well, the reason is you wanna get the particles
Lex Fridman (12:51.520)
through that accelerating element over and over again.
Lex Fridman (12:54.160)
So you wanna bring them back round.
Lex Fridman (12:55.280)
So that's why it's round.
Lex Fridman (12:56.320)
The question is why couldn't you make it smaller?
Lex Fridman (12:58.640)
Well, the basic answer is that these particles
Harry Cliff (13:01.360)
are going unbelievably quickly.
Lex Fridman (13:03.120)
So they travel at 99.9999991% of the speed of light
Harry Cliff (13:09.880)
in the LHC.
Lex Fridman (13:11.360)
And if you think about, say,
Harry Cliff (13:12.520)
driving your car around a corner at high speed,
Lex Fridman (13:16.040)
if you go fast, you need a lot of friction in the tires
Harry Cliff (13:19.520)
to make sure you don't slide off the road.
Lex Fridman (13:21.200)
So the limiting factor is how powerful a magnet can you make
Harry Cliff (13:26.560)
because what we do is magnets are used
Lex Fridman (13:28.480)
to bend the particles around the ring.
Lex Fridman (13:30.960)
And essentially the LHC, when it was designed,
Lex Fridman (13:33.120)
was designed with the most powerful magnets
Harry Cliff (13:35.200)
that could conceivably be built at the time.
Lex Fridman (13:37.920)
And so that's your kind of limiting factor.
Lex Fridman (13:40.400)
So if you wanted to make the machine smaller,
Lex Fridman (13:41.800)
that means a tighter bend,
Harry Cliff (13:42.840)
you need to have a more powerful magnet.
Lex Fridman (13:44.280)
So it's this toss up between how strong are your magnets
Harry Cliff (13:48.200)
versus how big a tunnel can you afford.
Lex Fridman (13:49.920)
The bigger the tunnel, the weaker the magnets can be.
Harry Cliff (13:51.560)
The smaller the tunnel, the stronger they've gotta be.
Lex Fridman (13:54.080)
Okay, so maybe can we backtrack to the Standard Model
Lex Fridman (13:57.680)
and say what kind of particles there are, period,
Lex Fridman (14:00.800)
and maybe the history of kind of assembling
Harry Cliff (14:04.560)
that the Standard Model of physics
Lex Fridman (14:06.880)
and then how that leads up to the hopes and dreams
Lex Fridman (14:10.400)
and the accomplishments of the Large Hadron Collider.
Lex Fridman (14:12.800)
Yeah, sure, okay.
Lex Fridman (14:14.000)
So all of 20th century physics in like five minutes.
Lex Fridman (14:16.720)
Yeah, please.
Harry Cliff (14:17.560)
Okay, so, okay, the story really begins properly.
Lex Fridman (14:21.280)
End of the 19th century, the basic view of matter
Harry Cliff (14:24.760)
is that matter is made of atoms
Lex Fridman (14:26.720)
and the atoms are indestructible, immutable little spheres
Harry Cliff (14:30.280)
like the things we were talking about
Lex Fridman (14:31.480)
that don't really exist.
Lex Fridman (14:32.600)
And there's one atom for every chemical element.
Lex Fridman (14:35.280)
So there's an atom for hydrogen, for helium,
Harry Cliff (14:36.880)
for carbon, for iron, et cetera, and they're all different.
Lex Fridman (14:39.800)
Then in 1897, experiments done
Harry Cliff (14:41.880)
at the Cavendish Laboratory in Cambridge,
Lex Fridman (14:43.280)
which is where I'm still, where I'm based,
Harry Cliff (14:45.840)
showed that there are actually smaller particles
Lex Fridman (14:48.720)
inside the atom, which eventually became known as electrons.
Lex Fridman (14:51.640)
So these are these negatively charged things
Lex Fridman (14:53.200)
that go around the outside.
Harry Cliff (14:54.840)
A few years later, Ernest Rutherford,
Lex Fridman (14:57.080)
very famous nuclear physicist,
Harry Cliff (14:58.680)
one of the pioneers of nuclear physics
Lex Fridman (15:00.000)
shows that the atom has a tiny nugget in the center,
Harry Cliff (15:03.480)
which we call the nucleus,
Lex Fridman (15:04.400)
which is a positively charged object.
Lex Fridman (15:05.840)
So then by like 1910, 11, we have this model of the atom
Lex Fridman (15:09.080)
that we learn in school,
Harry Cliff (15:09.960)
which is you've got a nucleus, electrons go around it.
Lex Fridman (15:13.240)
Fast forward a few years, the nucleus,
Harry Cliff (15:16.280)
people start doing experiments with radioactivity
Lex Fridman (15:18.480)
where they use alpha particles
Harry Cliff (15:20.840)
that are spat out of radioactive elements as bullets,
Lex Fridman (15:24.520)
and they fire them at other atoms.
Lex Fridman (15:26.800)
And by banging things into each other,
Lex Fridman (15:28.560)
they see that they can knock bits out of the nucleus.
Lex Fridman (15:31.200)
So these things come out called protons, first of all,
Lex Fridman (15:33.880)
which are positively charged particles
Harry Cliff (15:36.040)
about 2000 times heavier than the electron.
Lex Fridman (15:38.800)
And then 10 years later, more or less,
Harry Cliff (15:41.160)
a neutral particle is discovered called the neutron.
Lex Fridman (15:43.880)
So those are the three basic building blocks of atoms.
Harry Cliff (15:47.000)
You have protons and neutrons in the nucleus
Lex Fridman (15:49.400)
that are stuck together by something called the strong force,
Harry Cliff (15:51.800)
the strong nuclear force,
Lex Fridman (15:53.200)
and you have electrons in orbit around that,
Harry Cliff (15:55.800)
held in by the electromagnetic force,
Lex Fridman (15:57.920)
which is one of the forces of nature.
Harry Cliff (16:00.440)
That's sort of where we get to by like 1932, more or less.
Lex Fridman (16:04.840)
Then what happens is physics is nice and neat.
Harry Cliff (16:07.440)
In 1932, everything looks great, got three particles
Lex Fridman (16:09.520)
and all the atoms are made of, that's fine.
Lex Fridman (16:11.160)
But then cloud chamber experiments.
Lex Fridman (16:13.960)
These are devices that can be used to,
Harry Cliff (16:16.000)
the first device is capable of imaging subatomic particles
Lex Fridman (16:18.600)
so you can see their tracks.
Lex Fridman (16:19.600)
And they're used to study cosmic rays,
Lex Fridman (16:21.760)
particles that come from outer space
Lex Fridman (16:23.760)
and bang into the atmosphere.
Lex Fridman (16:25.640)
And in these experiments,
Harry Cliff (16:28.120)
people start to see a whole load of new particles.
Lex Fridman (16:29.840)
So they discover for one thing antimatter,
Harry Cliff (16:31.560)
which is the sort of a mirror image of the particles.
Lex Fridman (16:34.440)
So we discovered that there's also,
Harry Cliff (16:35.960)
as well as a negatively charged electron,
Lex Fridman (16:37.440)
there's something called a positron,
Harry Cliff (16:38.520)
which is a positively charged version of the electron.
Lex Fridman (16:40.480)
And there's an antiproton, which is negatively charged.
Lex Fridman (16:43.240)
And then a whole load of other weird particles
Lex Fridman (16:45.600)
start to get discovered.
Lex Fridman (16:46.480)
And no one really knows what they are.
Lex Fridman (16:48.800)
This is known as the zoo of particles.
Harry Cliff (16:50.960)
Are these discoveries from the first theoretical discoveries
Lex Fridman (16:55.160)
or are they discoveries in an experiment?
Lex Fridman (16:58.360)
So like, yeah, what's the process of discovery
Lex Fridman (17:01.120)
for these early sets of particles?
Harry Cliff (17:03.280)
It's a mixture.
Lex Fridman (17:04.120)
The early stuff around the atom is really
Harry Cliff (17:06.040)
experimentally driven.
Lex Fridman (17:07.200)
It's not based on some theory.
Harry Cliff (17:09.000)
It's exploration in the lab using equipment.
Lex Fridman (17:11.640)
So it's really people just figuring out,
Harry Cliff (17:12.920)
getting hands on with the phenomena,
Lex Fridman (17:14.400)
figuring out what these things are.
Lex Fridman (17:16.000)
And the theory comes a bit later.
Lex Fridman (17:17.600)
That's not always the case.
Lex Fridman (17:18.880)
So in the discovery of the anti electron, the positron,
Lex Fridman (17:22.480)
that was predicted from quantum mechanics and relativity
Harry Cliff (17:26.160)
by a very clever theoretical physicist called Paul Dirac,
Lex Fridman (17:30.320)
who was probably the second brightest physicist
Harry Cliff (17:33.240)
of the 20th century, apart from Einstein,
Lex Fridman (17:34.920)
but isn't anywhere near as well known.
Lex Fridman (17:36.720)
So he predicted the existence of the anti electron
Lex Fridman (17:39.240)
from basically a combination of the theories
Harry Cliff (17:41.880)
of quantum mechanics and relativity.
Lex Fridman (17:43.240)
And it was discovered about a year after
Harry Cliff (17:44.720)
he made the prediction.
Lex Fridman (17:46.000)
What happens when an electron meets a positron?
Harry Cliff (17:49.160)
They annihilate each other.
Lex Fridman (17:50.680)
So when you bring a particle and its antiparticle together,
Harry Cliff (17:54.400)
they react, well, they don't react,
Lex Fridman (17:56.440)
they just wipe each other out and they turn,
Harry Cliff (17:58.520)
their mass is turned into energy,
Lex Fridman (18:00.040)
usually in the form of photons, so you get light produced.
Lex Fridman (18:03.440)
So when you have that kind of situation,
Lex Fridman (18:06.920)
why does the universe exist at all
Lex Fridman (18:08.880)
if there's matter in any matter?
Lex Fridman (18:10.320)
Oh God, now we're getting into the really big questions.
Lex Fridman (18:12.080)
So, do you wanna go there now?
Lex Fridman (18:15.680)
Let's, maybe let's go there later.
Harry Cliff (18:19.000)
Cause that, I mean, that is a very big question.
Lex Fridman (18:20.600)
Yeah, let's take it slow with the standard model.
Harry Cliff (18:23.720)
So, okay, so there's matter and antimatter in the 30s.
Lex Fridman (18:28.240)
So what else?
Lex Fridman (18:29.520)
So matter and antimatter,
Lex Fridman (18:30.400)
and then a load of new particles start turning up
Harry Cliff (18:33.400)
in these cosmic ray experiments, first of all.
Lex Fridman (18:36.880)
And they don't seem to be particles that make up atoms.
Harry Cliff (18:40.120)
They're something else.
Lex Fridman (18:41.080)
They all mostly interact with a strong nuclear force.
Lex Fridman (18:44.120)
So they're a bit like protons and neutrons.
Lex Fridman (18:46.480)
And by, in the 1960s in America, particularly,
Lex Fridman (18:50.280)
but also in Europe and Russia,
Lex Fridman (18:52.320)
scientists started to build particle accelerators.
Lex Fridman (18:54.160)
So these are the forerunners of the LHC.
Lex Fridman (18:55.800)
So big ring shaped machines that were, you know,
Harry Cliff (18:58.280)
hundreds of meters long, which in those days was enormous.
Lex Fridman (19:00.720)
You never, you know, most physics up until that point
Harry Cliff (19:02.760)
had been done in labs, in universities, you know,
Lex Fridman (19:04.840)
with small bits of kit.
Lex Fridman (19:06.240)
So this is a big change.
Lex Fridman (19:07.160)
And when these accelerators are built,
Harry Cliff (19:08.920)
they start to find they can produce
Lex Fridman (19:10.680)
even more of these particles.
Lex Fridman (19:12.160)
So I don't know the exact numbers, but by around 1960,
Lex Fridman (19:16.440)
there are of order a hundred of these things
Harry Cliff (19:19.320)
that have been discovered.
Lex Fridman (19:20.160)
And physicists are kind of tearing their hair out
Harry Cliff (19:22.720)
because physics is all about simplification.
Lex Fridman (19:25.040)
And suddenly what was simple has become messy
Lex Fridman (19:28.080)
and complicated and everyone sort of wants
Lex Fridman (19:29.720)
to understand what's going on.
Harry Cliff (19:31.640)
As a quick kind of aside and probably really dumb question,
Lex Fridman (19:34.600)
but how is it possible to take something like a,
Harry Cliff (19:38.720)
like a photon or electron and be able to control it enough,
Lex Fridman (19:44.000)
like to be able to do a controlled experiment
Lex Fridman (19:49.000)
where you collide it against something else?
Lex Fridman (19:51.480)
Yeah.
Harry Cliff (19:52.320)
Is that, is that, that seems like an exceptionally difficult
Lex Fridman (19:55.920)
engineering challenge because you mentioned vacuum too.
Lex Fridman (19:59.520)
So you basically want to remove every other distraction
Lex Fridman (1:00:00.600)
3000 physicists and scientists
Lex Fridman (1:00:02.720)
and computer scientists on them each.
Lex Fridman (1:00:04.760)
They are the ones that discovered the Higgs
Lex Fridman (1:00:06.080)
and they look for supersymmetry and dark matter and so on.
Lex Fridman (1:00:08.560)
What we look at are standard model particles
Harry Cliff (1:00:11.200)
called bequarks, which depending on your preferences,
Lex Fridman (1:00:14.880)
either bottom or beauty,
Harry Cliff (1:00:16.600)
we tend to say beauty because it sounds sexier.
Lex Fridman (1:00:18.800)
Yeah, for sure.
Lex Fridman (1:00:20.440)
But these particles are interesting
Lex Fridman (1:00:22.680)
because they have, we can make lots of them.
Harry Cliff (1:00:25.840)
We make billions or hundreds of billions of these things.
Lex Fridman (1:00:28.880)
You can therefore measure their properties very precisely.
Lex Fridman (1:00:31.560)
So you can make these really lovely precision measurements.
Lex Fridman (1:00:34.400)
And what we are doing really is a sort of complimentary thing
Harry Cliff (1:00:39.400)
to the other big experiments, which is they,
Lex Fridman (1:00:41.920)
if you think of the sort of analogy they often use is,
Harry Cliff (1:00:44.120)
if you imagine you're looking in, you're in the jungle
Lex Fridman (1:00:45.800)
and you're looking for an elephant, say,
Lex Fridman (1:00:48.680)
and you are a hunter and you're kind of like,
Lex Fridman (1:00:52.040)
let's say there's the relevance, very rare.
Harry Cliff (1:00:53.520)
You don't know where in the jungle, the jungle's big.
Lex Fridman (1:00:55.440)
So there's two ways you go about this.
Harry Cliff (1:00:56.760)
Either you can go wandering around the jungle
Lex Fridman (1:00:58.720)
and try and find the elephant.
Harry Cliff (1:01:00.160)
The problem is if the elephant,
Lex Fridman (1:01:01.320)
if there's only one elephant and the jungle's big,
Harry Cliff (1:01:02.720)
the chances of running into it are very small.
Lex Fridman (1:01:04.760)
Or you could look on the ground
Lex Fridman (1:01:07.200)
and see if you see footprints left by the elephant.
Lex Fridman (1:01:09.200)
And if the elephant's moving around, you've got a chance,
Harry Cliff (1:01:11.480)
that you're better chance maybe
Lex Fridman (1:01:12.320)
of seeing the elephant's footprints.
Harry Cliff (1:01:13.880)
If you see the footprints, you go, okay, there's an elephant.
Lex Fridman (1:01:16.080)
I maybe don't know what kind of elephant it is,
Lex Fridman (1:01:18.320)
but I got a sense there's something out there.
Lex Fridman (1:01:20.000)
So that's sort of what we do.
Harry Cliff (1:01:21.600)
We are the footprint people.
Lex Fridman (1:01:23.040)
We are, we're looking for the footprints,
Harry Cliff (1:01:25.800)
the impressions that quantum fields
Lex Fridman (1:01:28.800)
that we haven't managed to directly create the particle of,
Harry Cliff (1:01:32.600)
the effects these quantum fields have
Lex Fridman (1:01:33.960)
on the ordinary standard model fields
Harry Cliff (1:01:35.560)
that we already know about.
Lex Fridman (1:01:36.480)
So these B particles, the way they behave
Harry Cliff (1:01:39.760)
can be influenced by the presence of say,
Lex Fridman (1:01:41.720)
super fields or dark matter fields or whatever you like.
Lex Fridman (1:01:45.200)
And the way they decay and behave can be altered slightly
Lex Fridman (1:01:48.640)
from what our theory tells us they ought to behave.
Lex Fridman (1:01:52.480)
And it's easier to collect huge amounts of data
Lex Fridman (1:01:54.600)
on B quarks.
Harry Cliff (1:01:56.600)
We get billions and billions of these things.
Lex Fridman (1:01:58.440)
You can make very precise measurements.
Lex Fridman (1:02:00.280)
And the only place really at the LHC
Lex Fridman (1:02:03.200)
or really in high energy physics at the moment
Harry Cliff (1:02:05.200)
where there's fairly compelling evidence
Lex Fridman (1:02:08.920)
that there might be something beyond the standard model
Harry Cliff (1:02:10.960)
is in these B, these beauty quarks decays.
Lex Fridman (1:02:15.320)
Just to clarify, which is the difference
Harry Cliff (1:02:18.640)
between the different, the four experiments,
Lex Fridman (1:02:20.320)
for example, that you mentioned,
Lex Fridman (1:02:21.600)
is it the kind of particles that are being collided?
Lex Fridman (1:02:24.760)
Is it the energies which they're collided?
Harry Cliff (1:02:27.160)
What's the fundamental difference
Lex Fridman (1:02:28.960)
between the different experiments?
Harry Cliff (1:02:30.440)
The collisions are the same.
Lex Fridman (1:02:32.280)
What's different is the design of the detectors.
Lex Fridman (1:02:34.480)
So Atlas and CMS are called,
Lex Fridman (1:02:37.040)
they're called what are called general purpose detectors.
Lex Fridman (1:02:39.760)
And they are basically barrel shaped machines
Lex Fridman (1:02:42.360)
and the collisions happen in the middle of the barrel
Lex Fridman (1:02:44.440)
and the barrel captures all the particles
Lex Fridman (1:02:46.600)
that go flying out in every direction.
Lex Fridman (1:02:48.040)
So in a sphere effectively that can fly out
Lex Fridman (1:02:49.840)
and it can record all of those particles.
Lex Fridman (1:02:51.840)
And what's the, sorry to be interrupting,
Lex Fridman (1:02:54.720)
but what's the mechanism of the recording?
Harry Cliff (1:02:57.440)
Oh, so these detectors, if you've seen pictures of them,
Lex Fridman (1:02:59.520)
they're huge, like Atlas is 25 meters high
Lex Fridman (1:03:03.080)
and 45 meters long, they're vast machines,
Lex Fridman (1:03:07.760)
instruments, I guess you should call them really.
Harry Cliff (1:03:09.600)
They are, they're kind of like onions.
Lex Fridman (1:03:11.760)
So they have layers, concentric layers of detectors,
Harry Cliff (1:03:15.360)
different sorts of detectors.
Lex Fridman (1:03:16.480)
So close into the beam pipe,
Harry Cliff (1:03:18.160)
you have what are called usually made of silicon,
Lex Fridman (1:03:20.600)
they're tracking detectors.
Lex Fridman (1:03:21.720)
So they're little made of strips of silicon
Lex Fridman (1:03:23.600)
or pixels of silicon.
Lex Fridman (1:03:24.960)
And when a particle goes through the silicon,
Lex Fridman (1:03:26.800)
it gives a little electrical signal
Lex Fridman (1:03:28.520)
and you get these dots, electrical dots
Lex Fridman (1:03:30.280)
through your detector, which allows you
Harry Cliff (1:03:31.440)
to reconstruct the trajectory of the particle.
Lex Fridman (1:03:34.120)
So that's the middle
Lex Fridman (1:03:34.960)
and then the outsides of these detectors,
Lex Fridman (1:03:36.280)
you have things called calorimeters,
Harry Cliff (1:03:37.720)
which measure the energies of the particles
Lex Fridman (1:03:39.600)
and the very edge you have things called muon chambers,
Harry Cliff (1:03:42.640)
which basically these muon particles,
Lex Fridman (1:03:44.680)
which are the heavy version of the electron,
Harry Cliff (1:03:46.720)
they're like high velocity bullets
Lex Fridman (1:03:48.440)
and they can get right to the edge of the detectors.
Harry Cliff (1:03:50.120)
If you see something at the edge, that's a muon.
Lex Fridman (1:03:52.480)
So that's broadly how they work.
Lex Fridman (1:03:54.000)
And all of that is being recorded.
Lex Fridman (1:03:55.720)
That's all being fed out to, you know, computers.
Harry Cliff (1:03:58.280)
Data must be awesome, okay.
Lex Fridman (1:04:00.800)
So LHCb is different.
Lex Fridman (1:04:02.000)
So we, because we're looking for these be quarks,
Lex Fridman (1:04:04.680)
be quarks tend to be produced along the beam line.
Lex Fridman (1:04:07.960)
So in a collision, the be quark tend to fly
Lex Fridman (1:04:10.640)
sort of close to the beam pipe.
Lex Fridman (1:04:12.840)
So we built a detector that sort of pyramid cone shaped
Lex Fridman (1:04:15.520)
basically, that just looks in one direction.
Lex Fridman (1:04:18.120)
So we ignore, if you have your collision,
Lex Fridman (1:04:20.280)
stuff goes everywhere.
Harry Cliff (1:04:21.120)
We ignore all the stuff over here and going off sideways.
Lex Fridman (1:04:23.400)
We're just looking in this little region
Harry Cliff (1:04:26.240)
close to the beam pipe
Lex Fridman (1:04:27.080)
where most of these be quarks are made.
Lex Fridman (1:04:28.720)
So is there a different aspect of the sensors involved
Lex Fridman (1:04:34.160)
in the collection of the be quark trajectories?
Harry Cliff (1:04:37.600)
There are some differences.
Lex Fridman (1:04:38.720)
So one of the differences is that,
Harry Cliff (1:04:40.840)
one of the ways you know you've seen a be quark
Lex Fridman (1:04:42.600)
is that be quarks are actually quite long lived
Harry Cliff (1:04:44.880)
by particle standards.
Lex Fridman (1:04:45.920)
So they live for 1.5 trillionths of a second,
Harry Cliff (1:04:49.120)
which is if you're a fundamental particle
Lex Fridman (1:04:50.600)
is a very long time.
Harry Cliff (1:04:51.640)
Cause the Higgs boson, I think lives for about
Lex Fridman (1:04:54.600)
a trillionth of a trillionth of a second,
Harry Cliff (1:04:57.240)
or maybe even less than that.
Lex Fridman (1:04:58.400)
So these are quite long lived things
Lex Fridman (1:05:00.760)
and they will actually fly a little distance
Lex Fridman (1:05:02.600)
before they decay.
Lex Fridman (1:05:03.440)
So they will fly a few centimeters maybe if you're lucky,
Lex Fridman (1:05:06.280)
then they'll decay into other stuff.
Lex Fridman (1:05:07.920)
So what we need to do in the middle of the detector,
Lex Fridman (1:05:10.360)
you wanna be able to see,
Harry Cliff (1:05:12.160)
you have your place where the protons crash into each other
Lex Fridman (1:05:14.560)
and that produces loads of particles that come flying out.
Lex Fridman (1:05:16.880)
So you have loads of lines, loads of tracks
Lex Fridman (1:05:18.960)
that point back to that proton collision.
Lex Fridman (1:05:21.320)
And then you're looking for a couple of other tracks,
Lex Fridman (1:05:23.400)
maybe two or three that point back to a different place
Harry Cliff (1:05:25.880)
that's maybe a few centimeters away
Lex Fridman (1:05:27.360)
from the proton collision.
Lex Fridman (1:05:28.400)
And that's the sign that a little B particle has flown
Lex Fridman (1:05:31.560)
a few centimeters and decayed somewhere else.
Lex Fridman (1:05:33.240)
So we need to be able to very accurately resolve
Lex Fridman (1:05:36.760)
the proton collision from the B particle decay.
Lex Fridman (1:05:39.480)
So the middle of our detector is very sensitive
Lex Fridman (1:05:42.360)
and it gets very close to the collision.
Lex Fridman (1:05:44.160)
So you have this really beautiful delicate
Lex Fridman (1:05:46.520)
silicon detector that sits,
Harry Cliff (1:05:48.360)
I think it's seven millimeters from the beam.
Lex Fridman (1:05:52.360)
And the LHC beam has as much energy
Harry Cliff (1:05:53.920)
as a jumbo jet at takeoff.
Lex Fridman (1:05:55.200)
So it's enough to melt a ton of copper.
Lex Fridman (1:05:57.360)
So you have this furiously powerful thing sitting next
Lex Fridman (1:05:59.840)
to this tiny delicate silicon sensor.
Lex Fridman (1:06:03.360)
So those aspects of our detector that are specialized
Lex Fridman (1:06:07.120)
to measure these particular B quarks
Harry Cliff (1:06:09.840)
that we're interested in.
Lex Fridman (1:06:10.880)
And is there, I mean, I remember seeing somewhere
Harry Cliff (1:06:12.960)
that there's some mention of matter and antimatter
Lex Fridman (1:06:15.360)
connected to the B, these beautiful quarks.
Lex Fridman (1:06:18.280)
Is that, what's the connection?
Lex Fridman (1:06:23.600)
Yeah, what's the connection there?
Harry Cliff (1:06:25.880)
Yeah, so there is a connection, which is that
Lex Fridman (1:06:29.600)
when you produce these B particles,
Harry Cliff (1:06:31.880)
these particles, because you don't see the B quark,
Lex Fridman (1:06:33.760)
you see the thing that B quark is inside.
Lex Fridman (1:06:35.400)
So they're bound up inside what we call beauty particles,
Lex Fridman (1:06:37.960)
where the B quark is joined together with another quark
Harry Cliff (1:06:40.640)
or two, maybe two other quarks, depending on what it is.
Lex Fridman (1:06:43.400)
They're a particular set of these B particles
Harry Cliff (1:06:46.160)
that exhibit this property called oscillation.
Lex Fridman (1:06:49.480)
So if you make a, for the sake of argument,
Harry Cliff (1:06:52.280)
a matter version of one of these B particles,
Lex Fridman (1:06:55.440)
as it travels, because of the magic of quantum mechanics,
Harry Cliff (1:06:58.840)
it oscillates backwards and forwards
Lex Fridman (1:07:01.040)
between its matter and antimatter versions.
Lex Fridman (1:07:03.880)
So it does this weird flipping about backwards and forwards.
Lex Fridman (1:07:06.720)
And what we can use this for is a laboratory
Harry Cliff (1:07:09.160)
for testing the symmetry between matter and antimatter.
Lex Fridman (1:07:12.880)
So if the symmetry between antimatter is precise,
Harry Cliff (1:07:15.680)
it's exact, then we should see these B particles decaying
Lex Fridman (1:07:20.040)
as often as matter, as they do as antimatter,
Harry Cliff (1:07:21.840)
because this oscillation should be even.
Lex Fridman (1:07:23.360)
It should spend as much time in each state.
Lex Fridman (1:07:26.000)
But what we actually see is that one of the states,
Lex Fridman (1:07:29.000)
it spends more time and it's more likely to decay
Harry Cliff (1:07:31.720)
in one state than the other.
Lex Fridman (1:07:32.800)
So this gives us a way of testing this fundamental symmetry
Harry Cliff (1:07:36.960)
between matter and antimatter.
Lex Fridman (1:07:39.160)
So what can you, sort of returning to the question
Harry Cliff (1:07:42.400)
before about this fundamental symmetry,
Lex Fridman (1:07:44.480)
it seems like if there's perfect symmetry
Harry Cliff (1:07:46.520)
between matter and antimatter,
Lex Fridman (1:07:50.560)
if we have the equal amount of each in our universe,
Harry Cliff (1:07:54.600)
it would just destroy itself.
Lex Fridman (1:07:57.000)
And just like you mentioned,
Harry Cliff (1:07:58.760)
we seem to live in a very unlikely universe
Lex Fridman (1:08:00.920)
where it doesn't destroy itself.
Lex Fridman (1:08:03.520)
So do you have some intuition about why that is?
Lex Fridman (1:08:07.280)
I mean, well, I'm not a theorist.
Harry Cliff (1:08:10.160)
I don't have any particular ideas myself.
Lex Fridman (1:08:11.680)
I mean, I sort of do measurements
Harry Cliff (1:08:13.120)
to try and test these things,
Lex Fridman (1:08:14.200)
but I mean, so the terms of the basic problem
Harry Cliff (1:08:16.000)
is that in the Big Bang,
Lex Fridman (1:08:17.800)
if you use the standard model to figure out
Lex Fridman (1:08:19.240)
what ought to have happened,
Lex Fridman (1:08:20.120)
you should have got equal amounts of matter
Lex Fridman (1:08:21.640)
and antimatter made,
Lex Fridman (1:08:22.480)
because whenever you make a particle
Harry Cliff (1:08:23.880)
in our collisions, for example,
Lex Fridman (1:08:25.440)
when we collide stuff together,
Harry Cliff (1:08:26.800)
you make a particle, you make an antiparticle.
Lex Fridman (1:08:28.440)
They always come together.
Harry Cliff (1:08:29.480)
They always annihilate together.
Lex Fridman (1:08:30.920)
So there's no way of making more matter than antimatter
Harry Cliff (1:08:33.440)
that we've discovered so far.
Lex Fridman (1:08:35.040)
So that means in the Big Bang,
Harry Cliff (1:08:36.080)
you get equal amounts of matter and antimatter.
Lex Fridman (1:08:38.200)
As the universe expands and cools down during the Big Bang,
Harry Cliff (1:08:41.720)
not very long after the Big Bang,
Lex Fridman (1:08:43.240)
I think a few seconds after the Big Bang,
Harry Cliff (1:08:45.040)
you have this event called the Great Annihilation,
Lex Fridman (1:08:47.280)
which is where all the particles and antiparticles
Harry Cliff (1:08:49.840)
smack into each other, annihilate, turn into light mostly,
Lex Fridman (1:08:53.520)
and you end up with a universe later on.
Harry Cliff (1:08:55.000)
If that was what happened,
Lex Fridman (1:08:55.960)
then the universe we live in today would be black and empty,
Harry Cliff (1:08:58.800)
apart from some photons, that would be it.
Lex Fridman (1:09:01.600)
So there is stuff in the universe.
Harry Cliff (1:09:03.560)
It appears to be just made of matter.
Lex Fridman (1:09:04.960)
So there's this big mystery as to how did this happen?
Lex Fridman (1:09:08.200)
And there are various ideas,
Lex Fridman (1:09:09.720)
which all involve sort of physics going on
Harry Cliff (1:09:13.520)
in the first trillionth of a second or so of the Big Bang.
Lex Fridman (1:09:17.040)
So it could be that one possibility
Harry Cliff (1:09:20.080)
is that the Higgs field is somehow implicated in this,
Lex Fridman (1:09:22.600)
that there was this event that took place
Harry Cliff (1:09:25.360)
in the early universe where the Higgs field
Lex Fridman (1:09:27.680)
basically switched on, it acquired its modern value.
Lex Fridman (1:09:31.400)
And when that happened,
Lex Fridman (1:09:33.480)
this caused all the particles to acquire mass
Lex Fridman (1:09:35.600)
and the universe basically went through a phase transition
Lex Fridman (1:09:37.880)
where you had a hot plasma of massless particles.
Lex Fridman (1:09:41.000)
And then in that plasma,
Lex Fridman (1:09:42.040)
it's almost like a gas turning into droplets of water.
Harry Cliff (1:09:44.760)
You get kind of these little bubbles forming in the universe
Lex Fridman (1:09:47.960)
where the Higgs field has acquired its modern value,
Harry Cliff (1:09:50.760)
the particles have got mass.
Lex Fridman (1:09:52.280)
And this phase transition in some models
Harry Cliff (1:09:55.200)
can cause more matter than antimatter to be produced,
Lex Fridman (1:09:57.960)
depending on how matter bounces off these bubbles
Harry Cliff (1:10:00.640)
in the early universe.
Lex Fridman (1:10:01.760)
So that's one idea.
Harry Cliff (1:10:02.760)
There's other ideas to do with neutrinos,
Lex Fridman (1:10:04.680)
that there are exotic types of neutrinos
Harry Cliff (1:10:06.360)
that can decay in a biased way to just matter
Lex Fridman (1:10:09.280)
and not to antimatter.
Harry Cliff (1:10:10.200)
So, and people are trying to test these ideas.
Lex Fridman (1:10:12.640)
That's what we're trying to do at LHCb.
Harry Cliff (1:10:14.280)
There's neutrino experiments planned
Lex Fridman (1:10:15.720)
that are trying to do these sorts of things as well.
Lex Fridman (1:10:17.560)
So yeah, there are ideas, but at the moment,
Lex Fridman (1:10:19.560)
no clear evidence for which of these ideas might be right.
Lex Fridman (1:10:22.920)
So we're talking about some incredible ideas.
Lex Fridman (1:10:25.520)
By the way, never heard anyone be so eloquent
Harry Cliff (1:10:28.320)
about describing even just the standard model.
Lex Fridman (1:10:31.680)
So I'm in awe just listening.
Harry Cliff (1:10:34.520)
Oh, thank you.
Lex Fridman (1:10:35.360)
Yeah, just having fun enjoying it.
Lex Fridman (1:10:38.080)
So the, yes, the theoretical,
Lex Fridman (1:10:40.280)
the particle physics is fascinating here.
Harry Cliff (1:10:42.520)
To me, one of the most fascinating things
Lex Fridman (1:10:44.680)
about the Large Hadron Collider is the human side of it.
Harry Cliff (1:10:47.880)
That a bunch of sort of brilliant people
Lex Fridman (1:10:51.520)
that probably have egos got together
Lex Fridman (1:10:54.360)
and were collaborate together and countries,
Lex Fridman (1:10:57.720)
I guess, collaborate together for the funds
Lex Fridman (1:11:00.000)
and everything's just collaboration everywhere.
Lex Fridman (1:11:03.000)
Cause you may be, I don't know what the right question here
Harry Cliff (1:11:07.440)
to ask, but almost what's your intuition
Lex Fridman (1:11:09.680)
about how it was possible to make this happen
Lex Fridman (1:11:11.840)
and what are the lessons we should learn
Lex Fridman (1:11:14.360)
for the future of human civilization
Lex Fridman (1:11:16.080)
in terms of our scientific progress?
Lex Fridman (1:11:17.840)
Cause it seems like this is a great, great illustration
Harry Cliff (1:11:21.600)
of us working together to do something big.
Lex Fridman (1:11:24.640)
Yeah, I think it's possibly the best example.
Harry Cliff (1:11:27.040)
Maybe I can think of international collaboration
Lex Fridman (1:11:30.280)
that isn't for some unpleasant purpose, basically.
Harry Cliff (1:11:33.400)
You know, I mean, so when I started out in the field
Lex Fridman (1:11:37.400)
in 2008 as a new PhD student,
Harry Cliff (1:11:39.720)
the LHC was basically finished.
Lex Fridman (1:11:41.480)
So I didn't have to go around asking for money for it
Harry Cliff (1:11:44.600)
or trying to make the case.
Lex Fridman (1:11:45.520)
So I have huge admiration for the people who managed that.
Harry Cliff (1:11:48.760)
Cause this was a project that was first imagined
Lex Fridman (1:11:51.160)
in the 1970s, in the late 70s
Harry Cliff (1:11:53.440)
was when the first conversations about the LHC were mooted
Lex Fridman (1:11:56.440)
and it took two and a half decades of campaigning
Lex Fridman (1:12:00.800)
and fundraising and persuasion
Lex Fridman (1:12:03.600)
until they started breaking ground
Lex Fridman (1:12:05.200)
and building the thing in the early noughties in 2000.
Lex Fridman (1:12:08.040)
So, I mean, I think the reason just from a sort of,
Harry Cliff (1:12:11.280)
from the point of view of the sort of science,
Lex Fridman (1:12:13.280)
the scientists there,
Harry Cliff (1:12:14.120)
I think the reason it works ultimately
Lex Fridman (1:12:16.680)
is that everywhere, everyone there is there
Harry Cliff (1:12:19.280)
for the same reason, which is, well, in principle, at least
Lex Fridman (1:12:23.680)
they're there because they're interested in the world.
Harry Cliff (1:12:25.520)
They want to find out, you know,
Lex Fridman (1:12:27.400)
what are the basic ingredients of our universe?
Lex Fridman (1:12:29.360)
What are the laws of nature?
Lex Fridman (1:12:31.040)
And so everyone is pulling in the same direction.
Harry Cliff (1:12:32.920)
Now, of course, everyone has their own
Lex Fridman (1:12:34.720)
things they're interested in.
Harry Cliff (1:12:35.680)
Everyone has their own careers to consider.
Lex Fridman (1:12:37.360)
And, you know, I wouldn't pretend that
Harry Cliff (1:12:38.800)
there isn't also a lot of competition.
Lex Fridman (1:12:40.760)
So there's this funny thing in these experiments
Harry Cliff (1:12:42.880)
where your collaborators,
Lex Fridman (1:12:43.960)
your 800 collaborators in LHCb,
Lex Fridman (1:12:46.120)
but you're also competitors
Lex Fridman (1:12:47.320)
because your academics in your various universities
Lex Fridman (1:12:49.920)
and you want to be the one that gets the paper out
Lex Fridman (1:12:51.520)
on the most exciting, you know, new measurements.
Lex Fridman (1:12:53.400)
So there's this funny thing where you're kind of trying
Lex Fridman (1:12:55.720)
to stake out your territory while also collaborating
Lex Fridman (1:12:58.440)
and having to work together to make the experiments work.
Lex Fridman (1:13:00.920)
And it does work amazingly well,
Harry Cliff (1:13:03.560)
actually considering all of that.
Lex Fridman (1:13:05.160)
And I think there was actually,
Harry Cliff (1:13:06.760)
I think McKinsey or one of these big management
Lex Fridman (1:13:08.680)
consultancy firms went into CERN maybe a decade or so ago
Harry Cliff (1:13:11.840)
to try to understand how these organizations function.
Lex Fridman (1:13:15.000)
Did they figure it out?
Harry Cliff (1:13:16.040)
I don't think they could.
Lex Fridman (1:13:16.960)
I mean, I think one of the things that's interesting,
Harry Cliff (1:13:18.800)
one of the other interesting things
Lex Fridman (1:13:19.800)
about these experiments is, you know,
Harry Cliff (1:13:21.080)
they're big operations like say Atlas has 3000 people.
Lex Fridman (1:13:24.960)
Now there was a person nominally
Harry Cliff (1:13:26.320)
who was the head of Atlas, they're called the spokesperson.
Lex Fridman (1:13:29.680)
And the spokesperson is elected by,
Harry Cliff (1:13:32.360)
usually by the collaboration,
Lex Fridman (1:13:34.240)
but they have no actual power really.
Harry Cliff (1:13:36.400)
I mean, they can't fire anyone.
Lex Fridman (1:13:38.560)
They're not anyone's boss.
Harry Cliff (1:13:39.720)
So, you know, my boss is a professor at Cambridge,
Lex Fridman (1:13:43.360)
not the head of my experiments.
Harry Cliff (1:13:45.120)
The head of my experiment can't tell me what to do really.
Lex Fridman (1:13:47.520)
And there's all these independent academics
Harry Cliff (1:13:50.200)
who are their own bosses who, you know,
Lex Fridman (1:13:52.400)
so that somehow it, nonetheless,
Harry Cliff (1:13:54.600)
by kind of consensus and discussion and lots of meetings,
Lex Fridman (1:13:58.520)
these things do happen and it does get done, but.
Harry Cliff (1:14:01.640)
It's like the queen here in the UK is the spokesperson.
Lex Fridman (1:14:04.960)
I guess so.
Harry Cliff (1:14:05.800)
No actual power. Except we don't elect her, no.
Lex Fridman (1:14:07.560)
No, we don't elect her.
Lex Fridman (1:14:08.880)
But everybody seems to love her.
Lex Fridman (1:14:10.480)
I don't know, from my outside perspective.
Lex Fridman (1:14:16.240)
But yeah, giant egos, brilliant people.
Lex Fridman (1:14:19.840)
And moving forward, do you think there's.
Harry Cliff (1:14:22.920)
Actually, I would pick up one thing you said just there,
Lex Fridman (1:14:24.800)
just the brilliant people thing.
Harry Cliff (1:14:25.840)
Cause I'm not saying that people aren't great.
Lex Fridman (1:14:28.240)
But I think there is this sort of impression
Harry Cliff (1:14:30.600)
that physicists all have to be brilliant or geniuses,
Lex Fridman (1:14:32.960)
which is not true actually.
Lex Fridman (1:14:34.160)
And you know, you have to be relatively bright for sure.
Lex Fridman (1:14:37.520)
But you know, a lot of people,
Harry Cliff (1:14:39.120)
a lot of the most successful experimental physicists
Lex Fridman (1:14:41.560)
are not necessarily the people with the biggest brains.
Harry Cliff (1:14:43.960)
They're the people who, you know,
Lex Fridman (1:14:45.680)
particularly one of the skills that's most important
Harry Cliff (1:14:47.440)
in particle physics is the ability to work
Lex Fridman (1:14:49.560)
with others and to collaborate and exchange ideas
Lex Fridman (1:14:51.320)
and also to work hard.
Lex Fridman (1:14:52.360)
And it's a sort of, often it's more a determination
Harry Cliff (1:14:55.520)
or a sort of other set of skills.
Lex Fridman (1:14:57.520)
It's not just being, you know, kind of some great brain.
Harry Cliff (1:15:01.440)
Very true.
Lex Fridman (1:15:02.280)
So, I mean, there's parallels to that
Harry Cliff (1:15:04.160)
in the machine learning world.
Lex Fridman (1:15:05.160)
If you wanna solve any real world problems,
Harry Cliff (1:15:08.200)
which I see as the particle accelerators,
Lex Fridman (1:15:11.200)
essentially a real world instantiation
Harry Cliff (1:15:14.920)
of theoretical physics.
Lex Fridman (1:15:16.720)
And for that, you have to not necessarily be brilliant,
Lex Fridman (1:15:20.280)
but be sort of obsessed, systematic, rigorous,
Lex Fridman (1:15:26.320)
sort of unborable, stubborn, all those kind of qualities
Harry Cliff (1:15:29.840)
that make for a great engineer.
Lex Fridman (1:15:31.160)
So, scientists purely speaking,
Harry Cliff (1:15:34.200)
that practitioner of the scientific method.
Lex Fridman (1:15:36.200)
So you're right.
Lex Fridman (1:15:37.400)
But nevertheless, to me that's brilliant.
Lex Fridman (1:15:39.800)
My dad's a physicist.
Harry Cliff (1:15:41.600)
I argue with him all the time.
Lex Fridman (1:15:43.040)
To me, engineering is the highest form of science.
Lex Fridman (1:15:46.000)
And he thinks that's all nonsense,
Lex Fridman (1:15:48.360)
that the real work is done by the theoretician.
Harry Cliff (1:15:50.640)
So, in fact, we have arguments about like people
Lex Fridman (1:15:54.320)
like Elon Musk, for example,
Harry Cliff (1:15:56.080)
because I think his work is quite brilliant,
Lex Fridman (1:15:58.640)
but he's fundamentally not coming up
Harry Cliff (1:16:00.520)
with any serious breakthroughs.
Lex Fridman (1:16:02.480)
He's just creating in this world, implementing,
Harry Cliff (1:16:07.080)
like making ideas happen that have a huge impact.
Lex Fridman (1:16:09.640)
To me, that's the Edison.
Harry Cliff (1:16:12.200)
That to me is a brilliant work,
Lex Fridman (1:16:17.400)
but to him, it's messy details
Harry Cliff (1:16:22.840)
that somebody will figure out anyway.
Lex Fridman (1:16:25.440)
I mean, I don't know whether you think
Harry Cliff (1:16:26.640)
there is a actual difference in temperament
Lex Fridman (1:16:29.000)
between say a physicist and an engineer,
Harry Cliff (1:16:31.160)
whether it's just what you got interested in.
Lex Fridman (1:16:33.000)
I don't know.
Harry Cliff (1:16:34.240)
I mean, a lot of what experimental physicists do
Lex Fridman (1:16:37.920)
is to some extent engineering.
Harry Cliff (1:16:40.040)
I mean, it's not what I do.
Lex Fridman (1:16:40.880)
I mostly do data stuff,
Lex Fridman (1:16:42.120)
but a lot of people would be called electrical engineers,
Lex Fridman (1:16:45.520)
but they trained as physicists,
Lex Fridman (1:16:46.960)
but they learned electrical engineering, for example,
Lex Fridman (1:16:48.880)
because they were building detectors.
Harry Cliff (1:16:50.960)
So, there's not such a clear divide, I think.
Lex Fridman (1:16:52.880)
Yeah, it's interesting.
Harry Cliff (1:16:53.720)
I mean, but there does seem to be,
Lex Fridman (1:16:55.600)
like you work with data.
Harry Cliff (1:16:57.120)
There does seem to be a certain,
Lex Fridman (1:16:59.920)
like I love data collection.
Harry Cliff (1:17:01.640)
There might be an OCD element or something
Lex Fridman (1:17:03.680)
that you're more naturally predisposed to
Harry Cliff (1:17:06.600)
as opposed to theory.
Lex Fridman (1:17:07.600)
Like I'm not afraid of data.
Harry Cliff (1:17:08.880)
I love data.
Lex Fridman (1:17:10.160)
And there's a lot of people in machine learning
Harry Cliff (1:17:11.680)
who are more like,
Lex Fridman (1:17:14.360)
they're basically afraid of data collection,
Harry Cliff (1:17:16.920)
afraid of data sets, afraid of all of that.
Lex Fridman (1:17:18.880)
They just want to stay in more than theoretical
Lex Fridman (1:17:20.720)
and they're really good at it, space.
Lex Fridman (1:17:22.800)
So, I don't know if that's the genetic,
Harry Cliff (1:17:24.040)
that's your upbringing, the way you go to school,
Lex Fridman (1:17:28.280)
but looking into the future of LHC and other colliders.
Harry Cliff (1:17:33.400)
So, there's in America,
Lex Fridman (1:17:35.320)
there's whatever it was called, the super,
Harry Cliff (1:17:37.520)
there's a lot of super.
Lex Fridman (1:17:38.360)
Superconducting super colliders.
Harry Cliff (1:17:39.840)
Yeah, superconducting.
Lex Fridman (1:17:40.840)
The desertron, yeah.
Harry Cliff (1:17:41.880)
Desertron, yeah.
Lex Fridman (1:17:43.000)
So, that was canceled, the construction of that.
Harry Cliff (1:17:45.880)
Yeah.
Lex Fridman (1:17:48.120)
Which is a sad thing,
Lex Fridman (1:17:50.880)
but what do you think is the future of these efforts?
Lex Fridman (1:17:54.160)
Will a bigger collider be built?
Lex Fridman (1:17:56.480)
Will LHC be expanded?
Lex Fridman (1:17:58.560)
What do you think?
Harry Cliff (1:17:59.920)
Well, in the near future, the LHC is gonna get an upgrade.
Lex Fridman (1:18:03.360)
So, that's pretty much confirmed.
Harry Cliff (1:18:04.840)
I think it is confirmed, which is,
Lex Fridman (1:18:07.160)
it's not an energy upgrade.
Harry Cliff (1:18:08.160)
It's what we call a luminosity upgrade.
Lex Fridman (1:18:10.200)
So, it basically means increasing
Harry Cliff (1:18:11.680)
the data collection rates.
Lex Fridman (1:18:13.400)
So, more collisions per second, basically,
Harry Cliff (1:18:15.920)
because after a few years of data taking,
Lex Fridman (1:18:18.160)
you get this law of diminishing returns
Harry Cliff (1:18:19.560)
where each year's worth of data
Lex Fridman (1:18:20.680)
is a smaller and smaller fraction
Harry Cliff (1:18:21.960)
of the lot you've already got.
Lex Fridman (1:18:23.440)
So, to get a real improvement in sensitivity,
Harry Cliff (1:18:25.840)
you need to increase the data rate
Lex Fridman (1:18:27.200)
by an order of magnitude.
Harry Cliff (1:18:28.280)
So, that's what this upgrade is gonna do.
Lex Fridman (1:18:30.520)
LHCb, at the moment, the whole detector
Harry Cliff (1:18:32.680)
is basically being rebuilt to allow it to record data
Lex Fridman (1:18:36.240)
at a much larger rate than we could before.
Harry Cliff (1:18:38.000)
So, that will make us sensitive
Lex Fridman (1:18:39.240)
to whole loads of new processes
Harry Cliff (1:18:40.680)
that we weren't able to study before.
Lex Fridman (1:18:42.200)
And I mentioned briefly these anomalies that we've seen.
Harry Cliff (1:18:45.760)
So, we've seen a bunch of very intriguing anomalies
Lex Fridman (1:18:49.040)
in these b quark decays,
Harry Cliff (1:18:52.320)
which may be hinting at the first signs
Lex Fridman (1:18:55.480)
of this kind of the elephant,
Harry Cliff (1:18:57.360)
the signs of some new quantum field
Lex Fridman (1:18:59.640)
or fields maybe beyond the standard model.
Harry Cliff (1:19:01.200)
It's not yet at the statistical threshold
Lex Fridman (1:19:02.920)
where you can say that you've observed something,
Lex Fridman (1:19:06.200)
but there's lots of anomalies in many measurements
Lex Fridman (1:19:08.840)
that all seem to be consistent with each other.
Harry Cliff (1:19:11.040)
So, it's quite interesting.
Lex Fridman (1:19:12.000)
So, the upgrade will allow us
Harry Cliff (1:19:13.600)
to really home in on these things
Lex Fridman (1:19:15.840)
and see whether these anomalies are real,
Harry Cliff (1:19:17.360)
because if they are real,
Lex Fridman (1:19:19.480)
and this kind of connects to your point
Harry Cliff (1:19:20.880)
about the next generation of machines,
Lex Fridman (1:19:23.720)
what we would have seen then is,
Harry Cliff (1:19:26.320)
we would have seen the tail end of some quantum field
Lex Fridman (1:19:29.240)
in influencing these b quarks.
Lex Fridman (1:19:31.800)
What we then need to do is to build a bigger collider
Lex Fridman (1:19:34.520)
to actually make the particle of that field.
Harry Cliff (1:19:37.480)
So, if these things really do exist.
Lex Fridman (1:19:40.240)
So, that would be one argument.
Harry Cliff (1:19:41.280)
I mean, so at the moment,
Lex Fridman (1:19:42.360)
Europe is going through this process
Harry Cliff (1:19:44.000)
of thinking about the strategy for the future.
Lex Fridman (1:19:47.800)
So, there are a number of different proposals on the table.
Harry Cliff (1:19:49.720)
One is for a sort of higher energy upgrade of the LHC,
Lex Fridman (1:19:53.600)
where you just build more powerful magnets
Lex Fridman (1:19:55.280)
and put them in the same tunnel.
Lex Fridman (1:19:56.200)
That's a sort of cheaper, less ambitious possibility.
Harry Cliff (1:19:59.680)
Most people don't really like it
Lex Fridman (1:20:00.840)
because it's sort of a bit of a dead end,
Harry Cliff (1:20:02.560)
because once you've done that, there's nowhere to go.
Lex Fridman (1:20:05.560)
There's a machine called Click,
Harry Cliff (1:20:06.840)
which is a compact linear collider,
Lex Fridman (1:20:08.960)
which is a electron positron collider
Harry Cliff (1:20:10.720)
that uses a novel type of acceleration technology
Lex Fridman (1:20:13.440)
to accelerate at shorter distances.
Harry Cliff (1:20:15.520)
We're still talking kilometers long,
Lex Fridman (1:20:17.000)
but not like 100 kilometers long.
Lex Fridman (1:20:19.880)
And then probably the project that is,
Lex Fridman (1:20:22.480)
I think getting the most support,
Harry Cliff (1:20:23.920)
it'd be interesting to see what happens,
Lex Fridman (1:20:25.400)
something called the Future Circular Collider,
Harry Cliff (1:20:28.040)
which is a really ambitious longterm multi decade project
Lex Fridman (1:20:32.040)
to build a 100 kilometer circumference tunnel
Harry Cliff (1:20:35.960)
under the Geneva region.
Lex Fridman (1:20:38.160)
The LHC would become a kind of feeding machine.
Harry Cliff (1:20:40.720)
It would just feed.
Lex Fridman (1:20:41.560)
So the same area, so it would be a feeder for the.
Harry Cliff (1:20:44.080)
Yeah.
Lex Fridman (1:20:44.920)
So it would kind of, the edge of this machine
Harry Cliff (1:20:46.400)
would be where the LHC is,
Lex Fridman (1:20:47.640)
but it would sort of go under Lake Geneva
Lex Fridman (1:20:49.120)
and round to the Alps, basically,
Lex Fridman (1:20:51.560)
up to the edge of the Geneva basin.
Lex Fridman (1:20:52.920)
So it's basically the biggest tunnel you can fit
Lex Fridman (1:20:55.560)
in the region based on the geology.
Harry Cliff (1:20:57.240)
100 kilometers.
Lex Fridman (1:20:58.080)
Yeah, so it's big.
Harry Cliff (1:20:58.920)
It'd be a long drive if your experiment's on one side.
Lex Fridman (1:21:01.880)
You've got to go back to CERN for lunch,
Lex Fridman (1:21:03.080)
so that would be a pain.
Lex Fridman (1:21:04.280)
But you know, so this project is,
Harry Cliff (1:21:07.600)
in principle, it's actually two accelerators.
Lex Fridman (1:21:09.120)
The first thing you would do
Harry Cliff (1:21:09.960)
is put an electron positron machine
Lex Fridman (1:21:11.720)
in the 100 kilometer tunnel to study the Higgs.
Lex Fridman (1:21:14.360)
So you'd make lots of Higgs bows
Lex Fridman (1:21:15.440)
and study it really precisely
Harry Cliff (1:21:16.960)
in the hope that you see it misbehaving
Lex Fridman (1:21:18.600)
and doing something it's not supposed to.
Lex Fridman (1:21:20.480)
And then in the much longer term,
Lex Fridman (1:21:22.880)
100, that machine gets taken out,
Harry Cliff (1:21:24.840)
you put in a proton proton machine.
Lex Fridman (1:21:26.520)
So it's like the LHC, but much bigger.
Lex Fridman (1:21:29.040)
And that's the way you start going
Lex Fridman (1:21:30.440)
and looking for dark matter,
Harry Cliff (1:21:32.400)
or you're trying to recreate this phase transition
Lex Fridman (1:21:35.960)
that I talked about in the early universe,
Harry Cliff (1:21:37.120)
where you can see matter anti matter being made,
Lex Fridman (1:21:39.360)
for example.
Harry Cliff (1:21:40.200)
There's lots of things you can do with these machines.
Lex Fridman (1:21:41.080)
The problem is that they will take,
Harry Cliff (1:21:43.560)
you know, the most optimistic,
Lex Fridman (1:21:45.440)
you're not gonna have any data
Harry Cliff (1:21:46.720)
from any of these machines until 2040,
Lex Fridman (1:21:49.080)
or, you know, because they take such a long time to build
Lex Fridman (1:21:51.840)
and they're so expensive.
Lex Fridman (1:21:52.920)
So you have, there'll be a process of R&D design,
Lex Fridman (1:21:55.960)
but also the political case being made.
Lex Fridman (1:21:57.960)
So LHC, what costs a few billion?
Harry Cliff (1:22:01.280)
Depends how you count it.
Lex Fridman (1:22:03.200)
I think most of the sort of more reasonable estimates
Harry Cliff (1:22:05.440)
that take everything into account properly,
Lex Fridman (1:22:07.000)
it's around the sort of 10, 11, 12 billion euro mark.
Lex Fridman (1:22:10.400)
What would be the future, sorry,
Lex Fridman (1:22:12.400)
I forgot the name already.
Harry Cliff (1:22:13.240)
Future Circular Collider.
Lex Fridman (1:22:14.720)
Future Circular Collider.
Harry Cliff (1:22:15.560)
Presumably they won't call it that when it's built,
Lex Fridman (1:22:16.920)
cause it won't be the future anymore.
Lex Fridman (1:22:18.280)
But I don't know, I don't know what they'll call it then.
Lex Fridman (1:22:20.680)
The very big Hadron Collider, I don't know.
Lex Fridman (1:22:25.120)
But that will, now I should know the numbers,
Lex Fridman (1:22:28.840)
but I think the whole project is estimated
Harry Cliff (1:22:31.160)
at about 30 billion euros,
Lex Fridman (1:22:32.880)
but that's money spent over between now and 2070 probably,
Harry Cliff (1:22:37.840)
which is when the last bit of it
Lex Fridman (1:22:39.840)
would be sort of finishing up, I guess.
Lex Fridman (1:22:42.360)
So you're talking a half a century of science
Lex Fridman (1:22:46.560)
coming out of this thing, shared by many countries.
Lex Fridman (1:22:48.720)
So the actual cost, the arguments that are made
Lex Fridman (1:22:51.200)
is that you could make this project fit
Harry Cliff (1:22:53.120)
within the existing budget of CERN,
Lex Fridman (1:22:56.160)
if you didn't do anything else.
Lex Fridman (1:22:57.480)
And CERN, by the way, we didn't mention, what is CERN?
Lex Fridman (1:23:00.520)
CERN is the European Organization for Nuclear Research.
Harry Cliff (1:23:03.280)
It's an international organization
Lex Fridman (1:23:05.240)
that was established in the 1950s
Harry Cliff (1:23:07.080)
in the wake of the second world war as a kind of,
Lex Fridman (1:23:10.280)
it was sort of like a scientific Marshall plan for Europe.
Harry Cliff (1:23:12.520)
The idea was that you bring European science back together
Lex Fridman (1:23:16.080)
for peaceful purposes,
Harry Cliff (1:23:17.320)
because what happened in the forties was,
Lex Fridman (1:23:20.000)
a lot of particular Jewish scientists,
Lex Fridman (1:23:21.280)
but a lot of scientists from central Europe
Lex Fridman (1:23:22.640)
had fled to the United States
Lex Fridman (1:23:25.000)
and Europe had sort of seen this brain drain.
Lex Fridman (1:23:27.240)
So there was a desire to bring the community back together
Harry Cliff (1:23:29.920)
for a project that wasn't building nasty bombs,
Lex Fridman (1:23:32.280)
but was doing something that was curiosity driven.
Harry Cliff (1:23:34.280)
So, and that has continued since then.
Lex Fridman (1:23:37.320)
So it's kind of a unique organization.
Harry Cliff (1:23:38.840)
It's you, to be a member as a country,
Lex Fridman (1:23:41.480)
you sort of sign up as a member
Lex Fridman (1:23:43.040)
and then you have to pay a fraction of your GDP
Lex Fridman (1:23:45.960)
each year as a subscription.
Harry Cliff (1:23:47.360)
I mean, it's a very small fraction, relatively speaking.
Lex Fridman (1:23:49.520)
I think it's like, I think the UK's contribution
Harry Cliff (1:23:51.480)
is a hundred or 200 million quid or something like that.
Lex Fridman (1:23:54.840)
Yeah, which is quite a lot, but not so.
Harry Cliff (1:23:57.480)
That's fascinating.
Lex Fridman (1:23:58.400)
I mean, just the whole thing that is possible,
Harry Cliff (1:24:00.040)
it's beautiful.
Lex Fridman (1:24:01.240)
It's a beautiful idea,
Harry Cliff (1:24:02.240)
especially when there's no wars on the line,
Lex Fridman (1:24:05.320)
it's not like we're freaking out,
Harry Cliff (1:24:06.560)
as we're actually legitimately collaborating
Lex Fridman (1:24:08.880)
to do good science.
Harry Cliff (1:24:09.880)
One of the things I don't think we really mentioned
Lex Fridman (1:24:11.880)
is on the final side, that sort of the data analysis side,
Harry Cliff (1:24:15.360)
is there breakthroughs possible there
Lex Fridman (1:24:17.080)
and the machine learning side,
Harry Cliff (1:24:18.160)
like is there a lot more signal to be mined
Lex Fridman (1:24:22.680)
in more effective ways from the actual raw data?
Harry Cliff (1:24:25.400)
Yeah, a lot of people are looking into that.
Lex Fridman (1:24:27.680)
I mean, so I use machine learning in my data analysis,
Lex Fridman (1:24:31.600)
but pretty naughty, basic stuff,
Lex Fridman (1:24:33.840)
cause I'm not a machine learning expert.
Harry Cliff (1:24:35.440)
I'm just a physicist who had to learn to do this stuff
Lex Fridman (1:24:37.960)
for my day job.
Lex Fridman (1:24:38.800)
So what a lot of people do is they use
Lex Fridman (1:24:40.600)
kind of off the shelf packages
Harry Cliff (1:24:42.560)
that you can train to do signal noise.
Lex Fridman (1:24:46.240)
Just clean up all the data.
Lex Fridman (1:24:48.280)
But one of the big challenges,
Lex Fridman (1:24:50.040)
the big challenge of the data is A, it's volume,
Harry Cliff (1:24:52.720)
there's huge amounts of data.
Lex Fridman (1:24:53.880)
So the LHC generates, now, okay,
Harry Cliff (1:24:56.480)
I try to remember what the actual numbers are,
Lex Fridman (1:24:57.920)
but if you, we don't record all our data,
Harry Cliff (1:24:59.440)
we record a tiny fraction of the data.
Lex Fridman (1:25:02.240)
It's like of order one 10,000th or something, I think.
Lex Fridman (1:25:04.920)
Is that right?
Lex Fridman (1:25:05.880)
Around that.
Lex Fridman (1:25:07.040)
So most of it gets thrown away.
Lex Fridman (1:25:08.600)
You couldn't record all the LHC data
Harry Cliff (1:25:10.080)
cause it would fill up every computer in the world
Lex Fridman (1:25:11.480)
in a matter of days, basically.
Lex Fridman (1:25:13.680)
So there's this process that happens on live,
Lex Fridman (1:25:17.000)
on the detector, something called a trigger,
Harry Cliff (1:25:18.880)
which in real time, 40 million times every second
Lex Fridman (1:25:21.360)
has to make a decision about whether this collision
Harry Cliff (1:25:23.680)
is likely to contain an interesting object,
Lex Fridman (1:25:26.400)
like a Higgs boson or a dark matter particle.
Lex Fridman (1:25:28.560)
And it has to do that very fast.
Lex Fridman (1:25:29.760)
And the software algorithms in the past
Harry Cliff (1:25:33.240)
were quite relatively basic.
Lex Fridman (1:25:36.040)
They did things like measure mementos
Lex Fridman (1:25:37.840)
and energies of particles and put some requirements.
Lex Fridman (1:25:40.320)
So you would say, if there's a particle
Harry Cliff (1:25:42.200)
with an energy above some threshold,
Lex Fridman (1:25:43.640)
then record this collision.
Lex Fridman (1:25:44.840)
But if there isn't, don't.
Lex Fridman (1:25:46.240)
Whereas now the attempt is get more and more
Harry Cliff (1:25:47.960)
machine learning in at the earliest possible stage.
Lex Fridman (1:25:51.080)
That's cool, at the stage of deciding
Harry Cliff (1:25:53.160)
whether we want to keep this data or not.
Lex Fridman (1:25:55.280)
But also maybe even lower down than that,
Harry Cliff (1:25:57.640)
which is the point where there's this,
Lex Fridman (1:26:01.160)
so generally how the data is reconstructed
Harry Cliff (1:26:02.800)
is you start off with a set of digital hits
Lex Fridman (1:26:06.280)
in your detector.
Lex Fridman (1:26:07.120)
So channels saying, did you see something?
Lex Fridman (1:26:08.840)
Did you not see something?
Harry Cliff (1:26:10.120)
That has to be then turned into tracks,
Lex Fridman (1:26:12.560)
particles going in different directions.
Lex Fridman (1:26:14.040)
And that's done by using fits
Lex Fridman (1:26:15.520)
that fit through the data points.
Lex Fridman (1:26:17.200)
And then that's passed to the algorithms
Lex Fridman (1:26:18.640)
that then go, is this interesting or not?
Harry Cliff (1:26:20.520)
What'd be better is you could train machine learning
Lex Fridman (1:26:22.520)
to just look at the raw hits,
Harry Cliff (1:26:24.120)
the basic real base level information,
Lex Fridman (1:26:26.360)
not have any of the reconstruction done.
Lex Fridman (1:26:28.440)
And it just goes, and it can learn to do pattern recognition
Lex Fridman (1:26:31.040)
on this strange three dimensional image that you get.
Lex Fridman (1:26:34.240)
And potentially that's where you could get really big gains
Lex Fridman (1:26:36.800)
because our triggers tend to be quite inefficient
Harry Cliff (1:26:38.760)
because they don't have time to do
Lex Fridman (1:26:41.880)
the full whiz bang processing
Harry Cliff (1:26:43.360)
to get all the information out that we would like,
Lex Fridman (1:26:45.400)
because you have to do the decision very quickly.
Lex Fridman (1:26:46.760)
So if you can come up with some clever
Lex Fridman (1:26:48.760)
machine learning technique,
Harry Cliff (1:26:50.080)
then potentially you can massively increase
Lex Fridman (1:26:52.000)
the amount of useful data you record
Lex Fridman (1:26:54.960)
and get rid of more of the background
Lex Fridman (1:26:58.400)
earlier in the process.
Harry Cliff (1:26:59.800)
Yeah, to me, that's an exciting possibility
Lex Fridman (1:27:01.440)
because then you don't have to build a sort of,
Harry Cliff (1:27:04.880)
you can get a gain without having to.
Lex Fridman (1:27:08.640)
Without having to build any hardware, I suppose.
Harry Cliff (1:27:10.360)
Hardware, yeah.
Lex Fridman (1:27:11.200)
Although you need lots of new GPU farms, I guess.
Lex Fridman (1:27:13.960)
So hardware still helps.
Lex Fridman (1:27:15.280)
But I got to talk to you,
Harry Cliff (1:27:20.280)
sort of I'm not sure how to ask,
Lex Fridman (1:27:22.840)
but you're clearly an incredible science communicator.
Harry Cliff (1:27:27.480)
I don't know if that's the right term,
Lex Fridman (1:27:29.560)
but you're basically a younger Neil deGrasse Tyson
Harry Cliff (1:27:32.520)
with a British accent.
Lex Fridman (1:27:33.680)
So, and you've, I mean,
Lex Fridman (1:27:36.480)
can you say where we are today, actually?
Lex Fridman (1:27:39.160)
Yeah, so today we're in the Royal Institution in London,
Harry Cliff (1:27:42.560)
which is a very old organization.
Lex Fridman (1:27:45.880)
It's been around for about 200 years now, I think.
Harry Cliff (1:27:47.760)
Maybe even I should know when it was founded.
Lex Fridman (1:27:49.800)
Sort of early 19th century,
Harry Cliff (1:27:51.440)
it was set up to basically communicate science to the public.
Lex Fridman (1:27:55.880)
So it was one of the first places in the world
Harry Cliff (1:27:57.560)
where famous scientists would come and give talks.
Lex Fridman (1:28:01.240)
So very famously Humphrey Davy, who you may know of,
Harry Cliff (1:28:05.440)
who was the person who discovered nitrous oxide.
Lex Fridman (1:28:07.560)
He was a very famous chemist and scientist.
Harry Cliff (1:28:11.200)
Also discovered electrolysis.
Lex Fridman (1:28:12.720)
So he used to do these fantastic,
Harry Cliff (1:28:13.920)
he was a very charismatic speaker.
Lex Fridman (1:28:15.040)
So he used to appear here.
Harry Cliff (1:28:15.880)
There's a big desk that they usually have in the theater
Lex Fridman (1:28:18.440)
and he would do demonstrations to the sort of the,
Harry Cliff (1:28:21.160)
the folk of London back in the early 19th century.
Lex Fridman (1:28:23.760)
And Michael Faraday, who I talked about,
Harry Cliff (1:28:25.200)
who is the person who did so much work on electromagnetism,
Lex Fridman (1:28:27.280)
he used, he lectured here.
Harry Cliff (1:28:28.400)
He also did experiments in the basement.
Lex Fridman (1:28:29.880)
So this place has got a long history
Harry Cliff (1:28:31.240)
of both scientific research,
Lex Fridman (1:28:33.320)
but also communication of scientific research.
Lex Fridman (1:28:35.800)
So you gave a few lectures here.
Lex Fridman (1:28:38.040)
How many, two?
Harry Cliff (1:28:39.320)
I've given, yeah, I've given a couple of lectures
Lex Fridman (1:28:41.080)
in this theater before, so.
Harry Cliff (1:28:42.280)
I mean, that's, so people should definitely go watch online.
Lex Fridman (1:28:46.000)
It's just the explanation of particle physics.
Lex Fridman (1:28:48.640)
So all the, I mean, it's incredible.
Lex Fridman (1:28:50.480)
Like your lectures are just incredible.
Harry Cliff (1:28:53.360)
I can't sing it enough praise.
Lex Fridman (1:28:54.520)
So it was awesome.
Lex Fridman (1:28:55.480)
But maybe can you say, what did that feel like?
Lex Fridman (1:29:00.280)
What does it feel like to lecture here, to talk about that?
Lex Fridman (1:29:03.600)
And maybe from a different perspective,
Lex Fridman (1:29:06.440)
more kind of like how the sausage is made is,
Lex Fridman (1:29:09.360)
how do you prepare for that kind of thing?
Lex Fridman (1:29:12.120)
How do you think about communication,
Harry Cliff (1:29:14.320)
the process of communicating these ideas
Lex Fridman (1:29:16.440)
in a way that's inspiring to,
Lex Fridman (1:29:18.480)
what I would say your talks are inspiring
Lex Fridman (1:29:21.200)
to like the general audience.
Harry Cliff (1:29:22.560)
You don't actually have to be a scientist.
Lex Fridman (1:29:25.080)
You can still be inspired without really knowing much of the,
Harry Cliff (1:29:28.040)
you start from the very basics.
Lex Fridman (1:29:30.720)
So what's the preparation process?
Lex Fridman (1:29:33.320)
And then the romantic question is,
Lex Fridman (1:29:34.800)
what did that feel like to perform here?
Harry Cliff (1:29:38.000)
I mean, profession, yeah.
Lex Fridman (1:29:39.600)
I mean, the process, I mean, the talk,
Harry Cliff (1:29:42.200)
my favorite talk that I gave here
Lex Fridman (1:29:43.280)
was one called Beyond the Higgs,
Harry Cliff (1:29:44.520)
which you can find on the Royal Institute's YouTube channel,
Lex Fridman (1:29:46.800)
which you should go and check out.
Harry Cliff (1:29:48.280)
I mean, and their channel's got loads of great talks
Lex Fridman (1:29:50.000)
with loads of great people as well.
Harry Cliff (1:29:52.760)
I mean, that one, I'd sort of given a version of it
Lex Fridman (1:29:55.160)
many times, so part of it is just practice, right?
Lex Fridman (1:29:57.360)
And actually, I don't have some great theory
Lex Fridman (1:29:59.000)
of how to communicate with people.
Harry Cliff (1:30:00.360)
It's more just that I'm really interested
Lex Fridman (1:30:02.640)
and excited by those ideas and I like talking about them.
Lex Fridman (1:30:05.240)
And through the process of doing that,
Lex Fridman (1:30:07.280)
I guess I figured out stories that work
Lex Fridman (1:30:09.640)
and explanations that work.
Lex Fridman (1:30:10.840)
When you say practice, you mean legitimately
Harry Cliff (1:30:12.920)
just giving talks? Just giving talks, yeah.
Lex Fridman (1:30:14.960)
I started off when I was a PhD student
Harry Cliff (1:30:17.240)
doing talks in schools and I still do that as well
Lex Fridman (1:30:20.040)
some of the time and doing things,
Harry Cliff (1:30:21.760)
I've even done a bit of standup comedy,
Lex Fridman (1:30:23.200)
which sort of went reasonably well,
Harry Cliff (1:30:25.240)
even if it was terrifying.
Lex Fridman (1:30:26.280)
And that's on YouTube as well.
Harry Cliff (1:30:27.480)
That's also on, I wouldn't necessarily recommend
Lex Fridman (1:30:29.240)
you check that out.
Harry Cliff (1:30:30.080)
I'm gonna post the links several places
Lex Fridman (1:30:33.200)
to make sure people click on it.
Lex Fridman (1:30:35.400)
But it's basically, I kind of have a story in my head
Lex Fridman (1:30:37.760)
and I kind of, I have to think about what I wanna say.
Harry Cliff (1:30:41.720)
I usually have some images to support what I'm saying
Lex Fridman (1:30:43.480)
and I get up and do it.
Lex Fridman (1:30:44.440)
And it's not really, I wish there was some kind of,
Lex Fridman (1:30:47.200)
I probably should have some proper process.
Harry Cliff (1:30:48.640)
This is very sounds like I'm just making up as I go along
Lex Fridman (1:30:50.640)
and I sort of am.
Harry Cliff (1:30:52.200)
Well, I think the fundamental thing that you said,
Lex Fridman (1:30:54.240)
I think it's like, I don't know if you know
Harry Cliff (1:30:58.320)
who a guy named Joe Rogan is.
Lex Fridman (1:31:01.120)
Yes, I do.
Lex Fridman (1:31:02.200)
So he's also kind of sounds like you in a sense
Lex Fridman (1:31:05.040)
that he's not very introspective about his process,
Lex Fridman (1:31:08.560)
but he's an incredibly engaging conversationalist.
Lex Fridman (1:31:13.040)
And I think one of the things that you and him share
Harry Cliff (1:31:15.800)
that I could see is like a genuine curiosity
Lex Fridman (1:31:19.920)
and passion for the topic.
Harry Cliff (1:31:22.320)
I think that could be systematically cultivated.
Lex Fridman (1:31:26.840)
I'm sure there's a process to it,
Lex Fridman (1:31:28.200)
but you come to it naturally somehow.
Lex Fridman (1:31:30.520)
I think maybe there's something else as well,
Harry Cliff (1:31:31.920)
which is to understand something.
Lex Fridman (1:31:34.240)
There's this quote by Feynman, which I really like,
Harry Cliff (1:31:35.920)
which is what I cannot create, I do not understand.
Lex Fridman (1:31:38.240)
So I'm not particularly super bright.
Lex Fridman (1:31:43.200)
So for me to understand something,
Lex Fridman (1:31:44.680)
I have to break it down into its simplest elements.
Lex Fridman (1:31:47.240)
And if I can then tell people about that,
Lex Fridman (1:31:49.800)
that helps me understand it as well.
Lex Fridman (1:31:51.120)
So I've learned to understand physics a lot more
Lex Fridman (1:31:55.480)
from the process of communicating,
Harry Cliff (1:31:57.120)
because it forces you to really scrutinize the ideas
Lex Fridman (1:32:00.640)
that you're communicating and it often makes you realize
Harry Cliff (1:32:02.600)
you don't really understand the ideas you're talking about.
Lex Fridman (1:32:06.000)
And I'm writing a book at the moment,
Lex Fridman (1:32:08.120)
and I had this experience yesterday where I realized
Lex Fridman (1:32:09.960)
I didn't really understand a pretty fundamental
Harry Cliff (1:32:12.600)
theoretical aspect of my own subject.
Lex Fridman (1:32:14.480)
And I had to go and I had to sort of spend
Harry Cliff (1:32:15.960)
a couple of days reading textbooks and thinking about it
Lex Fridman (1:32:18.840)
in order to make sure that the explanation I gave
Harry Cliff (1:32:21.760)
captured the, got as close to what is actually happening
Lex Fridman (1:32:24.800)
in the theory.
Lex Fridman (1:32:26.040)
And to do that, you have to really understand it properly.
Lex Fridman (1:32:29.040)
Yeah, and there's layers to understanding.
Harry Cliff (1:32:31.040)
It seems like the more,
Lex Fridman (1:32:33.720)
there must be some kind of Feynman law.
Harry Cliff (1:32:35.920)
I mean, the more you understand sort of the simpler
Lex Fridman (1:32:39.680)
you're able to really convey the essence of the idea, right?
Lex Fridman (1:32:46.080)
So it's like this reverse effect that it's like
Lex Fridman (1:32:52.480)
the more you understand, the simpler the final thing
Harry Cliff (1:32:54.880)
that you actually convey.
Lex Fridman (1:32:56.280)
And so the more accessible somehow it becomes.
Harry Cliff (1:32:58.800)
That's why Feynman's lectures are really accessible.
Lex Fridman (1:33:03.200)
It was just counterintuitive.
Harry Cliff (1:33:04.880)
Yeah, although there are some ideas
Lex Fridman (1:33:06.720)
that are very difficult to explain
Harry Cliff (1:33:09.400)
no matter how well or badly you understand them.
Lex Fridman (1:33:12.240)
Like I still can't really properly explain
Harry Cliff (1:33:15.280)
the Higgs mechanism.
Lex Fridman (1:33:16.440)
Yeah.
Harry Cliff (1:33:17.400)
Because some of these ideas only exist
Lex Fridman (1:33:19.120)
in mathematics really.
Lex Fridman (1:33:21.680)
And the only way to really develop an understanding
Lex Fridman (1:33:24.320)
is to go unfortunately to a graduate degree in physics.
Lex Fridman (1:33:29.080)
But you can get kind of a flavor of what's happening,
Lex Fridman (1:33:31.880)
I think, and it's trying to do that in a way
Harry Cliff (1:33:33.520)
that isn't misleading, but always also intelligible.
Lex Fridman (1:33:36.840)
So let me ask them the romantic question of
Lex Fridman (1:33:39.760)
what to you is the most, perhaps an unfair question,
Lex Fridman (1:33:44.480)
what is the most beautiful idea in physics?
Harry Cliff (1:33:49.000)
One that fills you with awe is the most surprising,
Lex Fridman (1:33:52.680)
the strangest, the weirdest.
Harry Cliff (1:33:54.760)
There's a lot of different definitions of beauty.
Lex Fridman (1:33:57.600)
And I'm sure there's several for you,
Lex Fridman (1:33:59.320)
but is there something that just jumps to mind
Lex Fridman (1:34:01.080)
that you think is just especially beautiful?
Harry Cliff (1:34:07.080)
There's a specific thing and a more general thing.
Lex Fridman (1:34:08.760)
So maybe the specific thing first,
Harry Cliff (1:34:10.040)
which I can now first came across as an undergraduate.
Lex Fridman (1:34:12.400)
I found this amazing.
Lex Fridman (1:34:13.440)
So this idea that the forces of nature,
Lex Fridman (1:34:17.120)
electromagnetism, strong force, the weak force,
Harry Cliff (1:34:19.960)
they arise in our theories as a consequence of symmetries.
Lex Fridman (1:34:24.720)
So symmetries in the laws of nature,
Harry Cliff (1:34:27.480)
in the equations essentially
Lex Fridman (1:34:29.000)
that used to describe these ideas,
Harry Cliff (1:34:32.080)
the process whereby theories come up
Lex Fridman (1:34:34.440)
with these sorts of models is they say,
Harry Cliff (1:34:36.600)
imagine the universe obeys this particular type of symmetry.
Lex Fridman (1:34:39.920)
It's a symmetry that isn't so far removed
Harry Cliff (1:34:42.240)
from a geometrical symmetry, like the rotations of a cube.
Lex Fridman (1:34:44.880)
It's not, you can't think of it quite that way,
Lex Fridman (1:34:46.360)
but it's sort of a similar sort of idea.
Lex Fridman (1:34:49.040)
And you say, okay, if the universe respects the symmetry,
Harry Cliff (1:34:51.880)
you find that you have to introduce a force
Lex Fridman (1:34:54.720)
which has the properties of electromagnetism
Harry Cliff (1:34:57.960)
or a different symmetry, you get the strong force
Lex Fridman (1:35:00.080)
or a different symmetry, you get the weak force.
Lex Fridman (1:35:01.800)
So these interactions seem to come from some deeper,
Lex Fridman (1:35:05.160)
it suggests that they come
Harry Cliff (1:35:06.280)
from some deeper symmetry principle.
Lex Fridman (1:35:07.960)
I mean, it depends a bit how you look at it
Harry Cliff (1:35:09.680)
because it could be that we're actually
Lex Fridman (1:35:10.720)
just recognizing symmetries in the things that we see,
Lex Fridman (1:35:12.800)
but there's something rather lovely about that.
Lex Fridman (1:35:15.160)
But I mean, I suppose a bigger thing that makes me wonder
Harry Cliff (1:35:17.080)
is actually, if you look at the laws of nature,
Lex Fridman (1:35:20.200)
how particles interact when you get really close down,
Harry Cliff (1:35:22.680)
they're basically pretty simple things.
Lex Fridman (1:35:24.240)
They bounce off each other by exchanging
Harry Cliff (1:35:26.360)
through force fields and they move around
Lex Fridman (1:35:27.840)
in very simple ways.
Lex Fridman (1:35:29.280)
And somehow these basic ingredients,
Lex Fridman (1:35:31.880)
these few particles that we know about in the forces
Harry Cliff (1:35:34.560)
creates this universe, which is unbelievably complicated
Lex Fridman (1:35:37.360)
and has things like you and me in it,
Lex Fridman (1:35:39.520)
and the earth and stars that make matter in their cores
Lex Fridman (1:35:43.400)
from the gravitational energy of their own bulk
Harry Cliff (1:35:46.160)
that then gets sprayed into the universe
Lex Fridman (1:35:47.600)
that forms other things.
Harry Cliff (1:35:48.480)
I mean, the fact that there's this incredibly long story
Lex Fridman (1:35:52.880)
that goes right back to the beginning,
Lex Fridman (1:35:55.920)
and we can take this story right back to a trillionth
Lex Fridman (1:35:58.240)
of a second after the Big Bang,
Lex Fridman (1:35:59.440)
and we can trace the origins of the stuff
Lex Fridman (1:36:01.280)
that we're made from.
Lex Fridman (1:36:02.440)
And it all ultimately comes from these simple ingredients
Lex Fridman (1:36:05.040)
with these simple rules.
Lex Fridman (1:36:06.560)
And the fact you can generate such complexity from that
Lex Fridman (1:36:08.720)
is really mysterious, I think, and strange.
Lex Fridman (1:36:11.080)
And it's not even a question that physicists
Lex Fridman (1:36:12.920)
can really tackle because we are sort of trying
Harry Cliff (1:36:15.760)
to find these really elementary laws.
Lex Fridman (1:36:19.080)
But it turns out that going from elementary laws
Lex Fridman (1:36:21.880)
and a few particles to something even as complicated
Lex Fridman (1:36:24.040)
as a molecule becomes very difficult.
Lex Fridman (1:36:26.600)
So going from a molecule to a human being
Lex Fridman (1:36:28.640)
is a problem that just can't be tackled,
Harry Cliff (1:36:31.960)
at least not at the moment, so.
Lex Fridman (1:36:34.040)
Yeah, the emergence of complexity from simple rules
Harry Cliff (1:36:37.320)
is so beautiful and so mysterious.
Lex Fridman (1:36:40.600)
And we don't have good mathematics
Harry Cliff (1:36:43.600)
to even try to approach that emergent phenomena.
Lex Fridman (1:36:47.320)
That's why we have chemistry and biology
Lex Fridman (1:36:48.800)
and all the other subjects, yeah, okay.
Lex Fridman (1:36:52.040)
I don't think there's a better way to end it, Harry.
Harry Cliff (1:36:55.880)
I can't, I mean, I think I speak for a lot of people
Lex Fridman (1:36:59.040)
that can't wait to see what happens
Harry Cliff (1:37:01.880)
in the next five, 10, 20 years with you.
Lex Fridman (1:37:03.800)
I think you're one of the great communicators of our time.
Lex Fridman (1:37:06.080)
So I hope you continue that and I hope that grows.
Lex Fridman (1:37:09.840)
And I'm definitely a huge fan.
Lex Fridman (1:37:12.280)
So it was an honor to talk to you today.
Lex Fridman (1:37:13.960)
Thanks so much, man.
Harry Cliff (1:37:14.800)
It was really fun, thanks very much.
Lex Fridman (1:37:16.360)
Thanks for listening to this conversation with Harry Kliff.
Lex Fridman (1:37:19.040)
And thank you to our sponsors, ExpressVPN
Lex Fridman (1:37:22.000)
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Harry Cliff (1:37:23.240)
Please consider supporting the podcast
Lex Fridman (1:37:25.000)
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Lex Fridman (1:37:29.880)
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Lex Fridman (1:37:34.160)
If you enjoy this podcast, subscribe on YouTube,
Harry Cliff (1:37:36.760)
review it with five stars on Apple Podcast,
Lex Fridman (1:37:39.240)
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Harry Cliff (1:37:41.880)
on Twitter at lexfreedman.
Lex Fridman (1:37:45.440)
And now let me leave you with some words from Harry Kliff.
Harry Cliff (1:37:48.520)
You and I are leftovers.
Lex Fridman (1:37:51.160)
Every particle in our bodies is a survivor
Harry Cliff (1:37:53.760)
from an almighty shootout between matter and antimatter
Lex Fridman (1:37:57.080)
that happened a little after the Big Bang.
Harry Cliff (1:37:59.360)
In fact, only one in a billion particles created
Lex Fridman (1:38:02.760)
at the beginning of time have survived to the present day.
Harry Cliff (1:38:06.080)
Thank you for listening and hope to see you next time.
Lex Fridman (20:03.200)
and really focus on this collision.
Lex Fridman (20:04.760)
How difficult of an engineering challenge is that?
Lex Fridman (20:06.840)
Just to get a sense.
Lex Fridman (20:07.840)
And it is very hard.
Lex Fridman (20:09.680)
I mean, in the early days,
Harry Cliff (20:10.920)
particularly when the first accelerators are being built
Lex Fridman (20:12.960)
in like 1932, Ernest Lawrence builds the first,
Lex Fridman (20:17.880)
what we call a cyclotron,
Lex Fridman (20:18.880)
which is like a little accelerator, this big or so.
Harry Cliff (20:21.760)
There's another one.
Lex Fridman (20:22.600)
Is it really that big?
Harry Cliff (20:23.420)
There's a tiny little thing.
Lex Fridman (20:24.260)
Yeah.
Lex Fridman (20:25.100)
So most of the first accelerators
Lex Fridman (20:27.840)
were what we call fixed target experiments.
Lex Fridman (20:31.000)
So you had a ring, you accelerate particles around the ring
Lex Fridman (20:34.100)
and then you fire them out the side into some target.
Lex Fridman (20:37.480)
So that makes the kind of,
Lex Fridman (20:39.480)
the colliding bit is relatively straightforward
Harry Cliff (20:41.320)
because you just fire it,
Lex Fridman (20:42.360)
whatever it is you want to fire it at.
Harry Cliff (20:43.660)
The hard bit is the steering the beams
Lex Fridman (20:46.200)
with the magnetic fields, getting, you know,
Harry Cliff (20:47.760)
strong enough electric fields to accelerate them,
Lex Fridman (20:49.560)
all that kind of stuff.
Harry Cliff (20:50.400)
The first colliders where you have two beams
Lex Fridman (20:53.760)
colliding head on, that comes later.
Lex Fridman (20:56.680)
And I don't think it's done until maybe the 1980s.
Lex Fridman (21:01.920)
I'm not entirely sure, but it's a much harder problem.
Harry Cliff (21:05.360)
That's crazy.
Lex Fridman (21:06.200)
Cause you have to like perfectly get them to hit each other.
Harry Cliff (21:09.880)
I mean, we're talking about, I mean, what scale it takes,
Lex Fridman (21:13.120)
what's the, I mean, the temporal thing is a giant mess,
Lex Fridman (21:18.160)
but the spatially, like the size is tiny.
Lex Fridman (21:23.160)
Well, to give you a sense of the LHC beams,
Harry Cliff (21:26.060)
the cross sectional diameter is I think around a dozen
Lex Fridman (21:31.620)
or so microns.
Harry Cliff (21:32.820)
So, you know, 10 millionths of a meter.
Lex Fridman (21:37.060)
And a beam, sorry, just to clarify,
Harry Cliff (21:39.900)
a beam contains how many,
Lex Fridman (21:41.340)
is it the bunches that you mentioned?
Lex Fridman (21:43.060)
Is it multiple particles or is it just one particle?
Lex Fridman (21:45.060)
Oh no, no.
Harry Cliff (21:45.900)
The bunches contains say a hundred billion protons each.
Lex Fridman (21:48.920)
So a bunch is, it's not really bunch shaped.
Harry Cliff (21:51.020)
They're actually quite long.
Lex Fridman (21:51.900)
They're like 30 centimeters long,
Lex Fridman (21:53.660)
but thinner than a human hair.
Lex Fridman (21:54.860)
So like very, very narrow, long sort of objects.
Harry Cliff (21:58.420)
Those are the things.
Lex Fridman (21:59.260)
So what happens in the LHC is you steer the beams
Lex Fridman (22:02.260)
so that they cross in the middle of the detector.
Lex Fridman (22:06.080)
So they basically have these swarms of protons
Harry Cliff (22:08.540)
that are flying through each other.
Lex Fridman (22:10.160)
And most of the, you have to have a hundred billion
Harry Cliff (22:12.180)
coming one way, a hundred billion another way,
Lex Fridman (22:14.500)
maybe 10 of them will hit each other.
Harry Cliff (22:17.100)
Oh, okay.
Lex Fridman (22:17.940)
So this, okay, that makes a lot more sense.
Lex Fridman (22:19.400)
So that's nice.
Lex Fridman (22:20.240)
But you're trying to use sort of,
Harry Cliff (22:21.980)
it's like probabilistically, you're not.
Lex Fridman (22:24.560)
You can't make a single particle collide
Harry Cliff (22:26.100)
with a single other particle.
Lex Fridman (22:26.940)
That's not an efficient way to do it.
Harry Cliff (22:28.140)
You'd be waiting a very long time to get anything.
Lex Fridman (22:30.980)
So you're basically, right.
Harry Cliff (22:34.020)
You're relying on probability to be that some fraction
Lex Fridman (22:37.460)
of them are gonna collide.
Lex Fridman (22:38.780)
And then you know which,
Lex Fridman (22:40.820)
because it's a swarm of the same kind of particle.
Lex Fridman (22:44.340)
So it doesn't matter which ones hit each other exactly.
Lex Fridman (22:46.420)
I mean, that's not to say it's not hard.
Harry Cliff (22:48.240)
You've got to, one of the challenges
Lex Fridman (22:50.420)
to make the collisions work is you have to squash
Harry Cliff (22:52.880)
these beams to very, very,
Lex Fridman (22:54.580)
basically the narrower they are the better
Harry Cliff (22:56.020)
cause the higher chances of them colliding.
Lex Fridman (22:58.780)
If you think about two flocks of birds
Harry Cliff (23:00.380)
flying through each other,
Lex Fridman (23:01.580)
the birds are all far apart in the flocks.
Harry Cliff (23:03.660)
There's not much chance that they'll collide.
Lex Fridman (23:04.980)
If they're all flying densely together,
Harry Cliff (23:06.420)
then they're much more likely to collide with each other.
Lex Fridman (23:08.360)
So that's the sort of problem.
Lex Fridman (23:10.060)
And it's tuning those magnetic fields,
Lex Fridman (23:12.060)
getting the magnetic fields powerful enough
Harry Cliff (23:13.380)
that you squash the beams and focus them
Lex Fridman (23:15.220)
so that you get enough collisions.
Harry Cliff (23:16.900)
That's super cool.
Lex Fridman (23:17.900)
Do you know how much software is involved here?
Harry Cliff (23:20.360)
I mean, it's sort of,
Lex Fridman (23:21.200)
I come from the software world and it's fascinating.
Harry Cliff (23:24.780)
This seems like software is buggy and messy.
Lex Fridman (23:28.060)
And so like, you almost don't want to rely
Harry Cliff (23:30.980)
on software too much.
Lex Fridman (23:31.900)
Like if you do, it has to be like low level,
Harry Cliff (23:33.900)
like Fortran style programming.
Lex Fridman (23:36.340)
Do you know how much software
Lex Fridman (23:37.540)
is in a large Hadron Collider?
Lex Fridman (23:39.500)
I mean, it depends at which level a lot.
Harry Cliff (23:41.580)
I mean, the whole thing is obviously computer controlled.
Lex Fridman (23:43.640)
So, I mean, I don't know a huge amount
Harry Cliff (23:45.460)
about how the software for the actual accelerator works,
Lex Fridman (23:49.340)
but I've been in the control center.
Lex Fridman (23:51.340)
So at CERN, there's this big control room,
Lex Fridman (23:53.280)
which is like a bit like a NASA mission control
Harry Cliff (23:55.480)
with big banks of desks where the engineers sit
Lex Fridman (23:57.760)
and they monitor the LHC.
Harry Cliff (23:59.180)
Cause you obviously can't be in the tunnel
Lex Fridman (24:00.860)
when it's running.
Lex Fridman (24:01.680)
So everything's remote.
Lex Fridman (24:03.460)
I mean, one sort of anecdote about the software side,
Harry Cliff (24:07.460)
in 2008, when the LHC first switched on,
Lex Fridman (24:10.460)
they had this big launch event
Lex Fridman (24:11.620)
and then big press conference party
Lex Fridman (24:14.940)
to inaugurate the machine.
Lex Fridman (24:16.260)
And about 10 days after that,
Lex Fridman (24:18.300)
they were doing some tests
Lex Fridman (24:19.580)
and this dramatic event happened
Lex Fridman (24:22.100)
where a huge explosion basically took place
Harry Cliff (24:24.180)
in the tunnel that destroyed or damaged, badly damaged
Lex Fridman (24:26.880)
about half a kilometer of the machine.
Lex Fridman (24:29.880)
But the stories, the engineers
Lex Fridman (24:31.540)
are in the control room that day.
Harry Cliff (24:33.620)
One guy told me this story about,
Lex Fridman (24:35.300)
basically all these screens they have in the control room
Harry Cliff (24:37.700)
started going red.
Lex Fridman (24:38.540)
So these alarms like kind of in software going off
Lex Fridman (24:42.300)
and then they assume that there's something wrong
Lex Fridman (24:43.500)
with the software, cause there's no way
Harry Cliff (24:45.500)
something this catastrophic could have happened.
Lex Fridman (24:48.700)
But I mean, when I worked on, when I was a PhD student,
Harry Cliff (24:52.300)
one of my jobs was to help to maintain the software
Lex Fridman (24:56.060)
that's used to control the detector that we work on.
Lex Fridman (24:59.140)
And that was, it's relatively robust,
Lex Fridman (25:01.180)
not such, you don't want it to be too fancy.
Harry Cliff (25:02.940)
You don't want it to sort of fall over too easily.
Lex Fridman (25:04.620)
The more clever stuff comes
Harry Cliff (25:07.040)
when you're talking about analyzing the data
Lex Fridman (25:08.500)
and that's where the sort of, you know.
Lex Fridman (25:10.540)
Are we jumping around too much?
Lex Fridman (25:11.740)
Do we finish with a standard model?
Harry Cliff (25:13.160)
We didn't, no.
Lex Fridman (25:14.000)
We didn't, so have we even started talking about quarks?
Harry Cliff (25:17.020)
We haven't talked to them yet.
Lex Fridman (25:17.860)
No, we got to the messy zoo of particles.
Harry Cliff (25:20.360)
Let me, let's go back there if it's okay.
Lex Fridman (25:22.980)
Okay, that's fine.
Lex Fridman (25:23.820)
Can you take us to the rest of the history of physics
Lex Fridman (25:26.540)
in the 20th century?
Harry Cliff (25:27.700)
Okay, sure.
Lex Fridman (25:29.020)
Okay, so circa 1960, you have this,
Harry Cliff (25:32.000)
you have these a hundred or so particles.
Lex Fridman (25:33.680)
It's a bit like the periodic table all over again.
Lex Fridman (25:35.540)
So you've got like having a hundred elements,
Lex Fridman (25:37.860)
it's sort of a bit like that.
Lex Fridman (25:39.260)
And people start to try to impose some order.
Lex Fridman (25:41.500)
So Murray Gellman, he's a theoretical physicist,
Harry Cliff (25:46.140)
American from New York.
Lex Fridman (25:47.700)
He realizes that there are these symmetries
Harry Cliff (25:50.500)
in these particles that if you arrange them in certain ways,
Lex Fridman (25:53.340)
they relate to each other.
Lex Fridman (25:54.380)
And he uses these symmetry principles
Lex Fridman (25:56.060)
to predict the existence of particles
Harry Cliff (25:58.260)
that haven't been discovered,
Lex Fridman (25:59.220)
which are then discovered in accelerators.
Lex Fridman (26:01.060)
So this starts to suggest
Lex Fridman (26:02.480)
there's not just random collections of crap.
Harry Cliff (26:04.500)
There's like, you know, actually some order
Lex Fridman (26:06.460)
to this underlying it.
Harry Cliff (26:08.740)
A little bit later in 1960, again, around the 1960s,
Lex Fridman (26:14.260)
he proposes along with another physicist called George Zweig
Harry Cliff (26:17.860)
that these symmetries arise because
Lex Fridman (26:21.060)
just like the patterns in the periodic table arise
Harry Cliff (26:23.380)
because atoms are made of electrons and protons,
Lex Fridman (26:26.420)
that these patterns are due to the fact
Harry Cliff (26:28.100)
that these particles are made of smaller things.
Lex Fridman (26:30.260)
And they are called quarks.
Lex Fridman (26:31.900)
So these are the particles they're predicted from theory.
Lex Fridman (26:34.500)
For a long time, no one really believes they're real.
Harry Cliff (26:36.700)
A lot of people think that they're a kind of theoretical
Lex Fridman (26:39.180)
convenience that happened to fit the data,
Lex Fridman (26:41.480)
but there's no evidence.
Lex Fridman (26:42.580)
No one's ever seen a quark in any experiment.
Lex Fridman (26:45.460)
And lots of experiments are done to try to find quarks,
Lex Fridman (26:48.580)
to try to knock a quark out of a...
Lex Fridman (26:50.460)
So the idea, if protons and neutrons are made of quarks,
Lex Fridman (26:52.860)
you should be able to knock a quark out and see the quark.
Harry Cliff (26:55.140)
That never happens.
Lex Fridman (26:56.020)
And we still have never actually managed to do that.
Lex Fridman (26:58.140)
Wait, really?
Lex Fridman (26:59.260)
No.
Lex Fridman (27:00.100)
So the way that it's done in the end
Lex Fridman (27:02.260)
is this machine that's built in California
Harry Cliff (27:04.620)
at the Stanford Lab, Stanford Linear Accelerator,
Lex Fridman (27:08.860)
which is essentially a gigantic,
Harry Cliff (27:10.540)
three kilometer long electron gun.
Lex Fridman (27:12.460)
It fires electrons, almost the speed of light, at protons.
Lex Fridman (27:16.260)
And when you do these experiments,
Lex Fridman (27:17.860)
what you find is at very high energy,
Harry Cliff (27:20.100)
the electrons bounce off small, hard objects
Lex Fridman (27:24.000)
inside the proton.
Lex Fridman (27:25.420)
So it's a bit like taking an X ray of the proton.
Lex Fridman (27:28.100)
You're firing these very light, high energy particles,
Lex Fridman (27:31.580)
and they're pinging off little things inside the proton
Lex Fridman (27:34.260)
that are like ball bearings, if you like.
Lex Fridman (27:36.260)
So you actually, that way,
Lex Fridman (27:38.220)
they resolve that there are three things
Harry Cliff (27:41.020)
inside the proton, which are quarks,
Lex Fridman (27:42.820)
the quarks that Gellman and Zweig had predicted.
Lex Fridman (27:45.480)
So that's really the evidence that convinces people
Lex Fridman (27:47.900)
that these things are real.
Harry Cliff (27:49.400)
The fact that we've never seen one
Lex Fridman (27:50.820)
in an experiment directly,
Harry Cliff (27:51.980)
they're always stuck inside other particles.
Lex Fridman (27:56.260)
And the reason for that is essentially
Harry Cliff (27:58.180)
to do with a strong force.
Lex Fridman (27:59.100)
The strong force is the force that holds quarks together.
Lex Fridman (28:01.700)
And it's so strong that it's impossible
Lex Fridman (28:04.020)
to actually liberate a quark.
Lex Fridman (28:06.460)
So if you try and pull a quark out of a proton,
Lex Fridman (28:08.260)
what actually ends up happening
Harry Cliff (28:09.700)
is that you kind of create this spring like bond
Lex Fridman (28:14.260)
in the strong force.
Harry Cliff (28:15.100)
You imagine two quarks that are held together
Lex Fridman (28:16.780)
by a very powerful spring.
Harry Cliff (28:18.540)
You pull and pull and pull,
Lex Fridman (28:19.940)
more and more energy gets stored in that bond,
Harry Cliff (28:22.280)
like stretching a spring,
Lex Fridman (28:23.420)
and eventually the tension gets so great,
Harry Cliff (28:25.340)
the spring snaps, and the energy in that bond
Lex Fridman (28:28.700)
gets turned into two new quarks
Harry Cliff (28:30.660)
that go on the broken ends.
Lex Fridman (28:32.420)
So you started with two quarks,
Harry Cliff (28:33.260)
you end up with four quarks.
Lex Fridman (28:34.660)
So you never actually get to take a quark out.
Harry Cliff (28:37.180)
You just end up making loads more quarks in the process.
Lex Fridman (28:39.860)
So how do we, again, forgive the dumb question,
Lex Fridman (28:42.900)
how do we know quarks are real then?
Lex Fridman (28:44.880)
Well, A, from these experiments where we can scatter,
Harry Cliff (28:48.100)
you fire electrons into the protons.
Lex Fridman (28:49.700)
They can burrow into the proton and knock off,
Lex Fridman (28:52.620)
and they can bounce off these quarks.
Lex Fridman (28:55.140)
So you can see from the angles,
Harry Cliff (28:56.460)
the electrons come out.
Lex Fridman (28:58.100)
I see, you can infer.
Harry Cliff (28:59.120)
You can infer that these things are there.
Lex Fridman (29:02.060)
The quark model can also be used.
Harry Cliff (29:03.620)
It has a lot of successes that you can use it
Lex Fridman (29:05.340)
to predict the existence of new particles
Harry Cliff (29:07.500)
that hadn't been seen.
Lex Fridman (29:08.700)
So, and it basically, there's lots of data
Harry Cliff (29:10.780)
basically showing from, you know,
Lex Fridman (29:12.340)
when we fire protons at each other at the LHC,
Harry Cliff (29:16.420)
a lot of quarks get knocked all over the place.
Lex Fridman (29:18.820)
And every time they try and escape from,
Harry Cliff (29:20.540)
say, one of their protons,
Lex Fridman (29:21.580)
they make a whole jet of quarks that go flying off,
Harry Cliff (29:25.580)
bound up in other sorts of particles made of quarks.
Lex Fridman (29:28.560)
So all the sort of the theoretical predictions
Harry Cliff (29:30.740)
from the basic theory of the strong force and the quarks
Lex Fridman (29:33.740)
all agrees with what we are seeing in experiments.
Harry Cliff (29:35.380)
We've just never seen an actual quark on its own
Lex Fridman (29:38.020)
because unfortunately it's impossible
Harry Cliff (29:39.280)
to get them out on their own.
Lex Fridman (29:41.140)
So quarks, these crazy smaller things
Harry Cliff (29:45.120)
that are hard to imagine are real.
Lex Fridman (29:47.160)
So what else?
Lex Fridman (29:48.140)
What else is part of the story here?
Lex Fridman (29:49.780)
So the other thing that's going on at the time,
Harry Cliff (29:52.100)
around the 60s, is an attempt to understand the forces
Lex Fridman (29:57.380)
that make these particles interact with each other.
Lex Fridman (30:00.220)
So you have the electromagnetic force,
Lex Fridman (30:01.780)
which is the force that was sort of discovered
Harry Cliff (30:03.900)
to some extent in this room, or at least in this building.
Lex Fridman (30:07.140)
So the first, what we call quantum field theory
Harry Cliff (30:10.020)
of the electromagnetic force is developed
Lex Fridman (30:13.380)
in the 1940s and 50s by Feynman,
Harry Cliff (30:17.660)
Richard Feynman amongst other people,
Lex Fridman (30:19.740)
Julian Schrodinger, Tom Onaga,
Harry Cliff (30:22.020)
who come up with the first,
Lex Fridman (30:23.060)
what we call a quantum field theory
Harry Cliff (30:24.420)
of the electromagnetic force.
Lex Fridman (30:25.740)
And this is where this description of,
Harry Cliff (30:27.340)
which I gave you at the beginning,
Lex Fridman (30:28.360)
that particles are ripples in fields.
Harry Cliff (30:30.820)
Well, in this theory, the photon, the particle of light
Lex Fridman (30:33.900)
is described as a ripple in this quantum field
Harry Cliff (30:36.340)
called the electromagnetic field.
Lex Fridman (30:38.720)
And the attempt then is made to try,
Harry Cliff (30:40.240)
well, can we come up with a quantum field theory
Lex Fridman (30:42.260)
of the other forces, of the strong force and the weak,
Harry Cliff (30:45.140)
the third force, which we haven't discussed,
Lex Fridman (30:47.140)
which is the weak force, which is a nuclear force.
Harry Cliff (30:50.740)
We don't really experience it in our everyday lives,
Lex Fridman (30:52.640)
but it's responsible for radioactive decay.
Harry Cliff (30:54.960)
It's the force that allows, you know,
Lex Fridman (30:56.980)
on a radioactive atom to turn
Harry Cliff (30:59.140)
into a different element, for example.
Lex Fridman (31:01.060)
And I don't know if you've explicitly mentioned,
Lex Fridman (31:03.420)
but so there's technically four forces.
Lex Fridman (31:06.100)
Yes.
Harry Cliff (31:06.980)
I guess three of them would be in the standard model,
Lex Fridman (31:09.900)
like the weak, the strong, and the electromagnetic,
Lex Fridman (31:13.460)
and then there's gravity.
Lex Fridman (31:14.540)
And there's gravity, which we don't worry about that,
Harry Cliff (31:16.220)
because it's too hard.
Lex Fridman (31:17.040)
It's too hard.
Harry Cliff (31:17.880)
Well, no, maybe we bring that up at the end, but yeah.
Lex Fridman (31:19.940)
Gravity, so far, we don't have a quantum theory of,
Lex Fridman (31:22.340)
and if you can solve that problem,
Lex Fridman (31:23.580)
you'll win a Nobel Prize.
Harry Cliff (31:25.140)
Well, we're gonna have to bring up
Lex Fridman (31:26.340)
the graviton at some point, I'm gonna ask you,
Lex Fridman (31:28.140)
but let's leave that to the side for now.
Lex Fridman (31:31.160)
So those three, okay, Feynman, electromagnetic force,
Lex Fridman (31:36.500)
the quantum field, and where does the weak force come in?
Lex Fridman (31:41.920)
So yeah, well, first of all,
Harry Cliff (31:43.580)
I mean, the strong force is the easiest.
Lex Fridman (31:44.780)
The strong force is a little bit
Harry Cliff (31:46.460)
like the electromagnetic force.
Lex Fridman (31:47.600)
It's a force that binds things together.
Lex Fridman (31:49.140)
So that's the force that holds quarks together
Lex Fridman (31:51.060)
inside the proton, for example.
Lex Fridman (31:52.860)
So a quantum field theory of that force
Lex Fridman (31:55.960)
is discovered in the, I think it's in the 60s,
Lex Fridman (31:59.820)
and it predicts the existence
Lex Fridman (32:01.460)
of new force particles called gluons.
Lex Fridman (32:04.500)
So gluons are a bit like the photon.
Lex Fridman (32:06.940)
The photon is the particle of electromagnetism.
Harry Cliff (32:09.500)
Gluons are the particles of the strong force.
Lex Fridman (32:13.540)
So just like there's an electromagnetic field,
Harry Cliff (32:15.860)
there's something called a gluon field,
Lex Fridman (32:17.540)
which is also all around us.
Lex Fridman (32:19.500)
So some of these particles, I guess,
Lex Fridman (32:21.780)
are the force carriers or whatever.
Harry Cliff (32:23.660)
They carry the force.
Lex Fridman (32:24.500)
It depends how you want to think about it.
Harry Cliff (32:25.980)
I mean, really the field, the strong force field,
Lex Fridman (32:28.460)
the gluon field is the thing that binds the quarks together.
Harry Cliff (32:32.880)
The gluons are the little ripples in that field.
Lex Fridman (32:35.460)
So that like, in the same way that the photon is a ripple
Harry Cliff (32:37.740)
in the electromagnetic field.
Lex Fridman (32:39.900)
But the thing that really does the binding is the field.
Harry Cliff (32:43.620)
I mean, you may have heard people talk about things
Lex Fridman (32:45.680)
like you've heard the phrase virtual particle.
Lex Fridman (32:49.860)
So sometimes in some, if you hear people describing
Lex Fridman (32:52.460)
how forces are exchanged between particles,
Harry Cliff (32:54.900)
they quite often talk about the idea
Lex Fridman (32:56.220)
that if you have an electron and another electron, say,
Lex Fridman (32:59.180)
and they're repelling each other
Lex Fridman (33:00.640)
through the electromagnetic force,
Harry Cliff (33:03.060)
you can think of that as if they're exchanging photons.
Lex Fridman (33:05.820)
So they're kind of firing photons
Harry Cliff (33:07.060)
backwards and forwards between each other.
Lex Fridman (33:08.660)
And that causes them to repel.
Harry Cliff (33:11.060)
That photon is then a virtual particle.
Lex Fridman (33:13.060)
Yes, that's what we call a virtual particle.
Harry Cliff (33:14.460)
In other words, it's not a real thing,
Lex Fridman (33:15.580)
it doesn't actually exist.
Lex Fridman (33:16.820)
So it's an artifact of the way theorists do calculations.
Lex Fridman (33:19.900)
So when they do calculations in quantum field theory,
Harry Cliff (33:22.140)
rather than, no one's discovered a way
Lex Fridman (33:24.460)
of just treating the whole field.
Harry Cliff (33:25.780)
You have to break the field down into simpler things.
Lex Fridman (33:28.200)
So you can basically treat the field
Harry Cliff (33:30.200)
as if it's made up of lots of these virtual photons,
Lex Fridman (33:33.540)
but there's no experiment that you can do
Harry Cliff (33:35.660)
that can detect these particles being exchanged.
Lex Fridman (33:38.420)
What's really happening in reality
Harry Cliff (33:40.460)
is that the electromagnetic field is warped
Lex Fridman (33:43.280)
by the charge of the electron and that causes the force.
Lex Fridman (33:46.240)
But the way we do calculations involves particles.
Lex Fridman (33:49.300)
So it's a bit confusing,
Lex Fridman (33:50.840)
but it's really a mathematical technique.
Lex Fridman (33:53.300)
It's not something that corresponds to reality.
Harry Cliff (33:55.740)
I mean, that's part, I guess, of the Feynman diagrams.
Lex Fridman (33:58.260)
Yes.
Harry Cliff (33:59.100)
Is this these virtual particles, okay.
Lex Fridman (34:00.100)
That's right, yeah.
Harry Cliff (34:01.500)
Some of these have mass, some of them don't.
Lex Fridman (34:06.380)
What does that even mean, not to have mass?
Lex Fridman (34:09.060)
And maybe you can say which one of them have mass
Lex Fridman (34:11.900)
and which don't.
Harry Cliff (34:12.860)
Okay, so.
Lex Fridman (34:14.140)
And why is mass important or relevant
Lex Fridman (34:17.020)
in this field view of the universe?
Lex Fridman (34:22.020)
Well, there are actually only two particles
Harry Cliff (34:23.700)
in the standard model that don't have mass,
Lex Fridman (34:25.500)
which are the photon and the gluons.
Lex Fridman (34:28.480)
So they are massless particles,
Lex Fridman (34:30.300)
but the electron, the quarks,
Lex Fridman (34:32.960)
and there are a bunch of other particles
Lex Fridman (34:34.140)
I haven't discussed.
Harry Cliff (34:34.960)
There's something called a muon and a tau,
Lex Fridman (34:36.380)
which are basically heavy versions of the electron
Harry Cliff (34:39.280)
that are unstable.
Lex Fridman (34:40.120)
You can make them in accelerators,
Lex Fridman (34:41.380)
but they don't form atoms or anything.
Lex Fridman (34:44.200)
They don't exist for long enough.
Lex Fridman (34:45.600)
But all the matter particles, there are 12 of them,
Lex Fridman (34:48.700)
six quarks and six, what we call leptons,
Harry Cliff (34:51.940)
which includes the electron and its two heavy versions
Lex Fridman (34:54.460)
and three neutrinos, all of them have mass.
Lex Fridman (34:57.380)
And so do, this is the critical bit.
Lex Fridman (34:59.500)
So the weak force, which is the third of these
Harry Cliff (35:02.860)
quantum forces, which is one of the hardest to understand,
Lex Fridman (35:07.540)
the force particles of that force have very large masses.
Lex Fridman (35:13.860)
And there are three of them.
Lex Fridman (35:14.900)
They're called the W plus, the W minus, and the Z boson.
Lex Fridman (35:19.540)
And they have masses of between 80 and 90 times
Lex Fridman (35:23.000)
that of the protons.
Harry Cliff (35:24.580)
They're very heavy.
Lex Fridman (35:25.660)
Wow.
Harry Cliff (35:26.500)
They're very heavy things.
Lex Fridman (35:27.320)
So they're what, the heaviest, I guess?
Harry Cliff (35:29.440)
They're not the heaviest.
Lex Fridman (35:30.280)
The heaviest particle is the top quark,
Harry Cliff (35:32.920)
which has a mass of about 175 ish protons.
Lex Fridman (35:38.460)
So that's really massive.
Lex Fridman (35:39.700)
And we don't know why it's so massive,
Lex Fridman (35:41.680)
but coming back to the weak force,
Lex Fridman (35:43.160)
so the problem in the 60s and 70s was that
Lex Fridman (35:47.380)
the reason that the electromagnetic force
Harry Cliff (35:50.100)
is a force that we can experience in our everyday lives.
Lex Fridman (35:51.900)
So if we have a magnet and a piece of metal,
Harry Cliff (35:53.260)
you can hold it, you know, a meter apart
Lex Fridman (35:55.420)
if it's powerful enough and you'll feel a force.
Harry Cliff (35:57.040)
Whereas the weak force only becomes apparent
Lex Fridman (36:00.380)
when you basically have two particles touching
Harry Cliff (36:03.180)
at the scale of a nucleus.
Lex Fridman (36:05.340)
So we just get to very short distances
Harry Cliff (36:06.980)
before this force becomes manifest.
Lex Fridman (36:09.620)
It's not, we don't get weak forces going on in this room.
Harry Cliff (36:12.260)
We don't notice them.
Lex Fridman (36:14.060)
And the reason for that is that the particle,
Harry Cliff (36:15.860)
well, the field that transmits the weak force,
Lex Fridman (36:20.140)
the particle that's associated with that field
Harry Cliff (36:22.300)
has a very large mass,
Lex Fridman (36:23.380)
which means that the field dies off very quickly.
Lex Fridman (36:26.240)
So as you, whereas an electric charge,
Lex Fridman (36:28.360)
if you were to look at the shape of the electromagnetic field,
Harry Cliff (36:30.640)
it would fall off with this,
Lex Fridman (36:32.140)
you have this thing called the inverse square law,
Harry Cliff (36:33.780)
which is the idea that the force halves
Lex Fridman (36:36.220)
every time you double the distance.
Harry Cliff (36:38.740)
No, sorry, it doesn't half.
Lex Fridman (36:39.700)
It quarters every time you double the distance
Harry Cliff (36:42.580)
between say the two particles.
Lex Fridman (36:44.220)
Whereas the weak force kind of,
Harry Cliff (36:45.780)
you move a little bit away from the nucleus
Lex Fridman (36:47.300)
and just disappears.
Harry Cliff (36:49.400)
The reason for that is because these fields,
Lex Fridman (36:51.980)
the particles that go with them have a very large mass.
Lex Fridman (36:55.420)
But the problem that theorists faced in the 60s
Lex Fridman (36:59.860)
was that if you tried to introduce massive force fields,
Harry Cliff (37:04.300)
the theory gave you nonsensical answers.
Lex Fridman (37:06.540)
So you'd end up with infinite results
Harry Cliff (37:08.700)
for a lot of the calculations you tried to do.
Lex Fridman (37:11.140)
So the basically, it seemed that quantum field theory
Harry Cliff (37:13.660)
was incompatible with having massive particles,
Lex Fridman (37:17.320)
not just the force particles actually,
Lex Fridman (37:18.700)
but even the electron was a problem.
Lex Fridman (37:21.900)
So this is where the Higgs
Harry Cliff (37:23.740)
that we sort of alluded to comes in.
Lex Fridman (37:25.640)
And the solution was to say, okay, well,
Harry Cliff (37:28.400)
actually all the particles in the Standard Model are mass.
Lex Fridman (37:30.460)
They have no mass.
Lex Fridman (37:31.540)
So the quarks, the electron, they don't have a mass.
Lex Fridman (37:33.340)
Neither do these weak particles.
Harry Cliff (37:34.820)
They don't have mass either.
Lex Fridman (37:36.740)
What happens is they actually acquire mass
Harry Cliff (37:38.500)
through another process.
Lex Fridman (37:40.420)
They get it from somewhere else.
Harry Cliff (37:41.660)
They don't actually have it intrinsically.
Lex Fridman (37:43.780)
So this idea that was introduced by,
Harry Cliff (37:46.500)
well, Peter Higgs is the most famous,
Lex Fridman (37:47.740)
but actually there are about six people
Harry Cliff (37:49.380)
that came up with the idea more or less at the same time,
Lex Fridman (37:52.080)
is that you introduce a new quantum field,
Harry Cliff (37:55.180)
which is another one of these invisible things
Lex Fridman (37:56.880)
that's everywhere.
Lex Fridman (37:58.100)
And it's through the interaction with this field
Lex Fridman (38:01.500)
that particles get mass.
Lex Fridman (38:02.660)
So you can think of say an electron in the Higgs field,
Lex Fridman (38:07.380)
the Higgs field kind of bunches around the electron.
Harry Cliff (38:10.900)
It's sort of drawn towards the electron.
Lex Fridman (38:12.900)
And that energy that's stored in that field
Harry Cliff (38:15.580)
around the electron is what we see
Lex Fridman (38:17.720)
as the mass of the electron.
Lex Fridman (38:19.320)
But if you could somehow turn off the Higgs field,
Lex Fridman (38:21.740)
then all the particles in nature would become massless
Lex Fridman (38:23.880)
and fly around at the speed of light.
Lex Fridman (38:26.540)
So this idea of the Higgs field allowed other people,
Harry Cliff (38:32.540)
other theorists to come up with a, well,
Lex Fridman (38:36.160)
it was another, basically a unified theory
Harry Cliff (38:39.500)
of the electromagnetic force and the weak force.
Lex Fridman (38:41.580)
So once you bring in the Higgs field,
Harry Cliff (38:43.060)
you can combine two of the forces into one.
Lex Fridman (38:45.620)
So it turns out the electromagnetic force
Lex Fridman (38:47.900)
and the weak force are just two aspects
Lex Fridman (38:49.660)
of the same fundamental force.
Lex Fridman (38:52.420)
And at the LHC, we go to high enough energies
Lex Fridman (38:54.760)
that you see these two forces unifying effectively.
Lex Fridman (38:59.460)
So first of all, it started as a theoretical notion,
Lex Fridman (39:04.260)
like this is some, and then, I mean,
Lex Fridman (39:07.540)
wasn't the Higgs called the God particle at some point?
Lex Fridman (39:10.660)
It was by a guy trying to sell popular science books, yeah.
Harry Cliff (39:13.660)
Yeah, but I mean, I remember because when I was hearing it,
Lex Fridman (39:17.880)
I thought it would, I mean, that would solve a lot of,
Harry Cliff (39:22.060)
that unify a lot of our ideas of physics was my notion.
Lex Fridman (39:26.340)
But maybe you can speak to that.
Harry Cliff (39:29.020)
Is it as big of a leap as a God particle
Lex Fridman (39:32.540)
or is it a Jesus particle, which, you know,
Harry Cliff (39:37.340)
what's the big contribution of Higgs
Lex Fridman (39:39.020)
in terms of this unification power?
Harry Cliff (39:40.780)
Yeah, I mean, to understand that,
Lex Fridman (39:42.940)
it maybe helps know the history a little bit.
Lex Fridman (39:45.060)
So when the, what we call electroweak theory
Lex Fridman (39:47.740)
was put together, which is where you unify electromagnetism
Harry Cliff (39:50.580)
with the weak force and Higgs is involved in all of that.
Lex Fridman (39:53.280)
So that theory, which was written in the mid 70s,
Harry Cliff (39:55.420)
predicted the existence of four new particles,
Lex Fridman (39:59.380)
the W plus boson, the W minus boson,
Harry Cliff (40:01.780)
the Z boson and the Higgs boson.
Lex Fridman (40:03.500)
So there were these four particles
Harry Cliff (40:04.780)
that came with the theory,
Lex Fridman (40:06.020)
that were predicted by the theory.
Harry Cliff (40:07.500)
In 1983, 84, the W's and the Z particles
Lex Fridman (40:11.620)
were discovered at an accelerator at CERN
Harry Cliff (40:14.320)
called the super proton synchrotron,
Lex Fridman (40:15.980)
which was a seven kilometer particle collider.
Lex Fridman (40:19.240)
So three of the bits of this theory had already been found.
Lex Fridman (40:22.820)
So people were pretty confident from the 80s
Harry Cliff (40:25.560)
that the Higgs must exist
Lex Fridman (40:27.060)
because it was a part of this family of particles
Harry Cliff (40:30.800)
that this theoretical structure only works
Lex Fridman (40:33.020)
if the Higgs is there.
Lex Fridman (40:34.460)
So what then happens,
Lex Fridman (40:36.540)
and so you've got this question about
Lex Fridman (40:37.380)
why is the LHC the size it is?
Lex Fridman (40:39.420)
Well, actually the tunnel that the LHC is in
Harry Cliff (40:41.500)
was not built for the LHC.
Lex Fridman (40:42.780)
It was built for a previous accelerator
Harry Cliff (40:45.140)
called the large electron positron collider.
Lex Fridman (40:48.740)
So that began operation in the late 80s, early 90s.
Harry Cliff (40:53.800)
They basically, that's when they dug
Lex Fridman (40:55.220)
the 27 kilometer tunnel.
Harry Cliff (40:56.420)
They put this accelerator into it,
Lex Fridman (40:58.020)
the collider that fires electrons
Lex Fridman (40:59.860)
and anti electrons at each other, electrons and positrons.
Lex Fridman (41:02.660)
So the purpose of that machine was,
Harry Cliff (41:05.180)
well, it was actually to look for the Higgs.
Lex Fridman (41:06.700)
That was one of the things it was trying to do.
Harry Cliff (41:08.700)
It didn't have enough energy to do it in the end.
Lex Fridman (41:11.380)
But the main thing it achieved was it studied
Harry Cliff (41:13.820)
the W and the Z particles at very high precision.
Lex Fridman (41:17.540)
So it made loads of these things.
Harry Cliff (41:19.300)
Previously, you can only make a few of them
Lex Fridman (41:20.540)
at the previous accelerator.
Lex Fridman (41:21.460)
So you could study these really, really precisely.
Lex Fridman (41:24.500)
And by studying their properties,
Harry Cliff (41:25.680)
you could really test this electroweak theory
Lex Fridman (41:28.220)
that had been invented in the 70s
Lex Fridman (41:29.820)
and really make sure that it worked.
Lex Fridman (41:31.260)
So actually by 1999, when this machine turned off,
Harry Cliff (41:36.380)
people knew, well, okay, you never know
Lex Fridman (41:39.500)
until you find the thing.
Lex Fridman (41:41.420)
But people were really confident
Lex Fridman (41:43.000)
this electroweak theory was right.
Lex Fridman (41:44.800)
And that the Higgs almost,
Lex Fridman (41:46.820)
the Higgs or something very like the Higgs had to exist
Harry Cliff (41:49.860)
because otherwise the whole thing doesn't work.
Lex Fridman (41:52.220)
It'd be really weird if you could discover
Lex Fridman (41:54.000)
and these particles, they all behave exactly
Lex Fridman (41:55.900)
as your theory tells you they should.
Lex Fridman (41:57.320)
But somehow this key piece of the picture is not there.
Lex Fridman (42:00.900)
So in a way, it depends how you look at it.
Harry Cliff (42:03.920)
The discovery of the Higgs on its own
Lex Fridman (42:07.020)
is obviously a huge achievement in many,
Harry Cliff (42:09.980)
both experimentally and theoretically.
Lex Fridman (42:12.300)
On the other hand, it's like having a jigsaw puzzle
Harry Cliff (42:15.260)
where every piece has been filled in.
Lex Fridman (42:17.100)
You have this beautiful image, there's one gap
Lex Fridman (42:19.020)
and you kind of know that piece must be there somewhere.
Lex Fridman (42:22.860)
So the discovery in itself, although it's important,
Harry Cliff (42:29.020)
is not so interesting.
Lex Fridman (42:30.420)
It's like a confirmation of the obvious at that point.
Lex Fridman (42:34.340)
But what makes it interesting
Lex Fridman (42:36.020)
is not that it just completes the standard model,
Harry Cliff (42:38.080)
which is a theory that we've known
Lex Fridman (42:39.980)
had the basic layout offs for 40 years or more now.
Harry Cliff (42:44.780)
It's that the Higgs actually is a unique particle.
Lex Fridman (42:48.420)
It's very different to any of the other particles
Harry Cliff (42:50.540)
in the standard model.
Lex Fridman (42:51.860)
And it's a theoretically very troublesome particle.
Harry Cliff (42:55.260)
There are a lot of nasty things to do with the Higgs,
Lex Fridman (42:59.240)
but also opportunities.
Lex Fridman (43:00.860)
So that we basically, we don't really understand
Lex Fridman (43:02.580)
how such an object can exist in the form that it does.
Lex Fridman (43:06.260)
So there are lots of reasons for thinking
Lex Fridman (43:08.500)
that the Higgs must come with a bunch of other particles
Harry Cliff (43:12.540)
or that it's perhaps made of other things.
Lex Fridman (43:15.020)
So it's not a fundamental particle,
Harry Cliff (43:16.460)
that it's made of smaller things.
Lex Fridman (43:17.940)
I can talk about that if you like a bit.
Harry Cliff (43:19.580)
That's still a notion, so the Higgs
Lex Fridman (43:23.180)
might not be a fundamental particle,
Harry Cliff (43:24.820)
that there might be some, it might, oh man.
Lex Fridman (43:27.180)
So that is an idea, it's not been demonstrated to be true.
Lex Fridman (43:31.080)
But I mean, all of these ideas basically come
Lex Fridman (43:33.820)
from the fact that this is a problem
Harry Cliff (43:37.940)
that motivated a lot of development in physics
Lex Fridman (43:40.100)
in the last 30 years or so.
Lex Fridman (43:42.380)
And it's this basic fact that the Higgs field,
Lex Fridman (43:44.780)
which is this field that's everywhere in the universe,
Harry Cliff (43:47.260)
this is the thing that gives mass to the particles.
Lex Fridman (43:49.060)
And the Higgs field is different from all the other fields
Harry Cliff (43:51.340)
in that, let's say you take the electromagnetic field,
Lex Fridman (43:54.420)
which is, if we actually were to measure
Harry Cliff (43:56.080)
the electromagnetic field in this room,
Lex Fridman (43:57.420)
we would measure all kinds of stuff going on
Harry Cliff (43:58.900)
because there's light, there's gonna be microwaves
Lex Fridman (44:00.940)
and radio waves and stuff.
Lex Fridman (44:02.100)
But let's say we could go to a really, really remote part
Lex Fridman (44:04.940)
of empty space and shield it and put a big box around it
Lex Fridman (44:07.660)
and then measure the electromagnetic field in that box.
Lex Fridman (44:10.060)
The field would be almost zero,
Harry Cliff (44:12.180)
apart from some little quantum fluctuations,
Lex Fridman (44:14.780)
but basically it goes to naught.
Harry Cliff (44:16.980)
The Higgs field has a value everywhere.
Lex Fridman (44:19.140)
So it's a bit like the whole,
Harry Cliff (44:20.700)
it's like the entire space has got this energy
Lex Fridman (44:23.440)
stored in the Higgs field, which is not zero,
Harry Cliff (44:25.420)
it's finite, it's a bit like having the temperature
Lex Fridman (44:28.860)
of space raised to some background temperature.
Lex Fridman (44:33.900)
And it's that energy that gives mass to the particles.
Lex Fridman (44:36.900)
So the reason that electrons and quarks have mass
Harry Cliff (44:40.460)
is through the interaction with this energy
Lex Fridman (44:42.440)
that's stored in the Higgs field.
Harry Cliff (44:44.820)
Now, it turns out that the precise value this energy has
Lex Fridman (44:50.620)
has to be very carefully tuned if you want a universe
Harry Cliff (44:55.700)
where interesting stuff can happen.
Lex Fridman (44:58.140)
So if you push the Higgs field down,
Harry Cliff (45:00.660)
it has a tendency to collapse to,
Lex Fridman (45:03.100)
well, there's a tendency,
Harry Cliff (45:04.020)
if you do your sort of naive calculations,
Lex Fridman (45:05.620)
there are basically two possible likely configurations
Harry Cliff (45:08.260)
for the Higgs field, which is either it's zero everywhere,
Lex Fridman (45:11.320)
in which case you have a universe
Harry Cliff (45:12.480)
which is just particles with no mass that can't form atoms
Lex Fridman (45:15.860)
and just fly about at the speed of light,
Harry Cliff (45:18.060)
or it explodes to an enormous value,
Lex Fridman (45:20.700)
what we call the Planck scale,
Harry Cliff (45:21.820)
which is the scale of quantum gravity.
Lex Fridman (45:24.140)
And at that point, if the Higgs field was that strong,
Harry Cliff (45:27.060)
even an electron would become so massive
Lex Fridman (45:28.900)
that it would collapse into a black hole.
Lex Fridman (45:31.200)
And then you have a universe made of black holes
Lex Fridman (45:33.100)
and nothing like us.
Lex Fridman (45:34.940)
So it seems that the strength of the Higgs field
Lex Fridman (45:37.640)
is to achieve the value that we see
Harry Cliff (45:40.180)
requires what we call fine tuning of the laws of physics.
Lex Fridman (45:42.900)
You have to fiddle around with the other fields
Harry Cliff (45:45.340)
in the Standard Model and their properties
Lex Fridman (45:47.340)
to just get it to this right sort of Goldilocks value
Harry Cliff (45:50.780)
that allows atoms to exist.
Lex Fridman (45:53.100)
This is deeply fishy.
Harry Cliff (45:54.580)
People really dislike this.
Lex Fridman (45:57.380)
Well, yeah, I guess, so what would be,
Lex Fridman (45:59.420)
so two explanations.
Lex Fridman (46:00.840)
One, there's a god that designed this perfectly,
Lex Fridman (46:03.060)
and two is there's an infinite number
Lex Fridman (46:05.580)
of alternate universes,
Lex Fridman (46:07.020)
and we just happen to be in the one in which life
Lex Fridman (46:10.300)
is possible, complexity.
Lex Fridman (46:12.380)
So when you say, I mean, life, any kind of complexity,
Lex Fridman (46:15.540)
that's not either complete chaos or black holes.
Lex Fridman (46:21.500)
I mean, how does that make you feel?
Lex Fridman (46:22.760)
What do you make of that?
Harry Cliff (46:23.600)
That's such a fascinating notion
Lex Fridman (46:25.260)
that this perfectly tuned field
Harry Cliff (46:28.340)
that's the same everywhere is there.
Lex Fridman (46:31.120)
What do you make of that?
Lex Fridman (46:33.140)
Yeah, what do you make of that?
Lex Fridman (46:34.200)
I mean, yeah, so you laid out
Harry Cliff (46:35.300)
two of the possible explanations.
Lex Fridman (46:36.660)
Really?
Harry Cliff (46:37.500)
Some, well, yeah, I mean, well,
Lex Fridman (46:38.820)
someone, some cosmic creator went,
Harry Cliff (46:41.060)
yeah, let's fix that to be at the right level.
Lex Fridman (46:43.140)
That's one possibility, I guess.
Harry Cliff (46:44.420)
It's not a scientifically testable one,
Lex Fridman (46:45.900)
but theoretically, I guess, it's possible.
Harry Cliff (46:48.740)
Sorry to interrupt, but there could also be
Lex Fridman (46:50.860)
not a designer, but couldn't there be just,
Harry Cliff (46:54.540)
I guess I'm not sure what that would be,
Lex Fridman (46:55.980)
but some kind of force that,
Harry Cliff (46:58.240)
that some kind of mechanism
Lex Fridman (47:03.240)
by which this kind of field is enforced
Harry Cliff (47:09.840)
in order to create complexity,
Lex Fridman (47:11.920)
basically forces that pull the universe
Harry Cliff (47:16.280)
towards an interesting complexity.
Lex Fridman (47:19.800)
I mean, yeah, I mean, there are people
Harry Cliff (47:21.360)
who have those ideas.
Lex Fridman (47:22.280)
I don't really subscribe to them.
Harry Cliff (47:23.600)
As I'm saying, it sounds really stupid.
Lex Fridman (47:25.520)
No, I mean, there are definitely people
Harry Cliff (47:27.120)
that make those kind of arguments.
Lex Fridman (47:29.400)
There's ideas that, I think it's Lee Smolin's idea,
Harry Cliff (47:33.040)
or one, I think, that universes are born inside black holes.
Lex Fridman (47:38.120)
And so, universes, they basically have
Harry Cliff (47:40.280)
like Darwinian evolution of the universe,
Lex Fridman (47:42.480)
where universes give birth to other universes.
Lex Fridman (47:44.800)
And if universes where black holes can form
Lex Fridman (47:46.720)
are more likely to give birth to more universes,
Lex Fridman (47:48.760)
so you end up with universes which have similar laws.
Lex Fridman (47:51.260)
I mean, I don't know, whatever.
Harry Cliff (47:52.600)
Well, I talked to Lee recently on this podcast,
Lex Fridman (47:57.080)
and he's a reminder to me that the physics community
Harry Cliff (48:02.360)
has like so many interesting characters in it.
Lex Fridman (48:05.600)
It's fascinating.
Harry Cliff (48:06.960)
Anyway, sorry, so.
Lex Fridman (48:08.040)
I mean, as an experimentalist, I tend to sort of think,
Harry Cliff (48:10.120)
these are interesting ideas, but they're not really testable,
Lex Fridman (48:12.760)
so I tend not to think about them very much.
Harry Cliff (48:14.720)
So, I mean, going back to the science of this,
Lex Fridman (48:17.600)
there is an explanation.
Harry Cliff (48:19.120)
There is a possible solution to this problem of the Higgs,
Lex Fridman (48:21.240)
which doesn't involve multiverses or creators fiddling about
Harry Cliff (48:25.200)
with the laws of physics.
Lex Fridman (48:26.560)
If the most popular solution
Harry Cliff (48:28.400)
was something called supersymmetry,
Lex Fridman (48:30.440)
which is a theory which involves a new type of symmetry
Harry Cliff (48:34.800)
of the universe.
Lex Fridman (48:35.720)
In fact, it's one of the last types of symmetries
Harry Cliff (48:37.680)
that it's possible to have
Lex Fridman (48:38.560)
that we haven't already seen in nature,
Harry Cliff (48:40.400)
which is a symmetry between force particles
Lex Fridman (48:43.600)
and matter particles.
Lex Fridman (48:44.760)
So what we call fermions, which are the matter particles
Lex Fridman (48:47.880)
and bosons, which are force particles.
Lex Fridman (48:49.920)
And if you have supersymmetry, then there is a super partner
Lex Fridman (48:52.600)
for every particle in the standard model.
Lex Fridman (48:55.920)
And without going into the details,
Lex Fridman (48:57.520)
the effect of this basically is that you have
Harry Cliff (48:59.320)
a whole bunch of other fields,
Lex Fridman (49:01.320)
and these fields cancel out the effect
Harry Cliff (49:04.240)
of the standard model fields,
Lex Fridman (49:05.680)
and they stabilize the Higgs field at a nice sensible value.
Lex Fridman (49:09.000)
So in supersymmetry, you naturally,
Lex Fridman (49:11.360)
without any tinkering about with the constants of nature
Harry Cliff (49:14.280)
or anything, you get a Higgs field with a nice value,
Lex Fridman (49:17.360)
which is the one we see.
Lex Fridman (49:18.960)
So this is one of the,
Lex Fridman (49:20.200)
and supersymmetry's also got lots of other things
Harry Cliff (49:22.000)
going for it.
Lex Fridman (49:22.840)
It predicts the existence of a dark matter particle,
Harry Cliff (49:25.360)
which would be great.
Lex Fridman (49:27.000)
It potentially suggests that the strong force
Lex Fridman (49:30.120)
and the electroweak force unify at high energy.
Lex Fridman (49:32.760)
So lots of reasons people thought this was a productive idea.
Lex Fridman (49:35.360)
And when the LHC was, just before it was turned on,
Lex Fridman (49:37.800)
there was a lot of hype, I guess,
Harry Cliff (49:39.600)
a lot of an expectation that we would discover
Lex Fridman (49:42.440)
these super partners because,
Lex Fridman (49:44.280)
and particularly the main reason was
Lex Fridman (49:46.080)
that if supersymmetry stabilizes the Higgs field
Harry Cliff (49:50.240)
at this nice Goldilocks value,
Lex Fridman (49:52.960)
these super particles should have a mass
Harry Cliff (49:55.760)
around the energy that we're probing at the LHC,
Lex Fridman (49:58.520)
around the energy of the Higgs.
Lex Fridman (49:59.920)
So it was kind of thought, you discover the Higgs,
Lex Fridman (50:01.520)
you probably discover super partners as well.
Lex Fridman (50:03.600)
So once you start creating ripples in this Higgs field,
Lex Fridman (50:06.200)
you should be able to see these kinds of,
Harry Cliff (50:08.680)
you should be, yeah.
Lex Fridman (50:09.520)
So the super fields would be there.
Harry Cliff (50:11.000)
When I, at the very beginning I said,
Lex Fridman (50:12.320)
we're probing the vacuum.
Lex Fridman (50:13.720)
What I mean is really that, you know,
Lex Fridman (50:15.200)
okay, let's say these super fields exist.
Harry Cliff (50:16.680)
The vacuum contains super fields.
Lex Fridman (50:18.200)
They're there, these supersymmetric fields.
Harry Cliff (50:20.160)
If we hit them hard enough, we can make them vibrate.
Lex Fridman (50:22.640)
We see super particles come flying out.
Harry Cliff (50:24.840)
That's the sort of, that's the idea.
Lex Fridman (50:26.320)
That's the whole, okay.
Harry Cliff (50:27.160)
That's the whole point.
Lex Fridman (50:29.600)
But we haven't.
Lex Fridman (50:30.680)
But we haven't.
Lex Fridman (50:31.520)
So, so far at least, I mean,
Harry Cliff (50:33.240)
we've had now a decade of data taking at the LHC.
Lex Fridman (50:38.920)
No signs of super partners have,
Harry Cliff (50:41.760)
supersymmetric particles have been found.
Lex Fridman (50:43.360)
In fact, no signs of any physics, any new particles
Harry Cliff (50:46.000)
beyond the Standard Model have been found.
Lex Fridman (50:47.520)
So supersymmetry is not the only thing that can do this.
Harry Cliff (50:49.520)
There are other theories that involve
Lex Fridman (50:51.440)
additional dimensions of space
Harry Cliff (50:53.160)
or potentially involve the Higgs boson
Lex Fridman (50:55.680)
being made of smaller things,
Harry Cliff (50:56.920)
being made of other particles.
Lex Fridman (50:58.360)
Yeah, that's an interesting, you know,
Harry Cliff (50:59.480)
I haven't heard that before.
Lex Fridman (51:00.560)
That's really, that's an interesting,
Lex Fridman (51:02.320)
but can you maybe linger on that?
Lex Fridman (51:03.640)
Like what, what could be,
Lex Fridman (51:06.400)
what could the Higgs particle be made of?
Lex Fridman (51:08.880)
Well, so the oldest, I think the original ideas about this
Harry Cliff (51:11.560)
was these theories called technicolor,
Lex Fridman (51:14.080)
which were basically like an analogy with the strong force.
Lex Fridman (51:17.320)
So the idea was the Higgs boson was a bound state
Lex Fridman (51:21.440)
of two very strongly interacting particles
Harry Cliff (51:24.480)
that were a bit like quarks.
Lex Fridman (51:25.560)
So like quarks, but I guess higher energy things
Harry Cliff (51:29.200)
with a super strong force.
Lex Fridman (51:30.440)
So not the strong force, but a new force
Harry Cliff (51:31.880)
that was very strong.
Lex Fridman (51:33.000)
And the Higgs was a bound state of these, these objects.
Lex Fridman (51:36.480)
And the Higgs would in principle, if that was right,
Lex Fridman (51:38.440)
would be the first in a series of technicolor particles.
Harry Cliff (51:42.400)
Technicolor, I think not being a theorist,
Lex Fridman (51:45.560)
but it's not, it's basically not done very well,
Harry Cliff (51:48.120)
particularly since the LHC found the Higgs,
Lex Fridman (51:49.600)
that kind of, it rules out, you know,
Harry Cliff (51:52.360)
a lot of these technicolor theories,
Lex Fridman (51:53.440)
but there are other things that are a bit like technicolor.
Lex Fridman (51:55.440)
So there's a theory called partial composite,
Lex Fridman (52:00.560)
which is an idea that some of my colleagues
Harry Cliff (52:02.560)
at Cambridge have worked on,
Lex Fridman (52:04.360)
which is a similar sort of idea that the Higgs
Harry Cliff (52:06.840)
is a bound state of some strongly interacting particles,
Lex Fridman (52:10.440)
and that the standard model particles themselves,
Harry Cliff (52:13.000)
the more exotic ones like the top quark
Lex Fridman (52:16.000)
are also sort of mixtures of these composite particles.
Lex Fridman (52:20.480)
So it's a kind of an extension to the standard model,
Lex Fridman (52:23.320)
which explains this problem
Harry Cliff (52:25.280)
with the Higgs bosons, Goldilocks value,
Lex Fridman (52:28.560)
but also helps us understand we have,
Harry Cliff (52:31.160)
we're in a situation now, again,
Lex Fridman (52:32.840)
a bit like the periodic table,
Harry Cliff (52:34.480)
where we have six quarks, six leptons in this kind of,
Lex Fridman (52:38.640)
you can arrange in this nice table
Lex Fridman (52:40.000)
and you can see these columns where the patterns repeat
Lex Fridman (52:42.480)
and you go, okay, maybe there's something deeper
Harry Cliff (52:46.160)
going on here, you know,
Lex Fridman (52:47.640)
and so this would potentially be something,
Harry Cliff (52:49.640)
this partial composite theory could explain,
Lex Fridman (52:52.880)
a sort of enlarge this picture
Harry Cliff (52:54.360)
that allows us to see the whole symmetrical pattern
Lex Fridman (52:56.480)
and understand what the ingredients, why do we have,
Lex Fridman (52:59.120)
so one of the big questions in particle physics is,
Lex Fridman (53:02.160)
why are there three copies of the matter particles?
Lex Fridman (53:06.240)
So in what we call the first generation,
Lex Fridman (53:07.920)
which is what we're made of,
Harry Cliff (53:08.920)
there's the electron, the electron neutrino,
Lex Fridman (53:11.760)
the up quark and the down quark,
Harry Cliff (53:13.160)
they're the most common matter particles in the universe,
Lex Fridman (53:15.640)
but then there are copies of these four particles
Harry Cliff (53:18.800)
in the second and the third generations,
Lex Fridman (53:20.360)
so things like nuons and top quarks and other stuff,
Harry Cliff (53:23.120)
we don't know why, we see these patterns,
Lex Fridman (53:25.240)
we have no idea where it comes from,
Lex Fridman (53:26.440)
so that's another big question, you know,
Lex Fridman (53:28.880)
can we find out the deeper order that explains
Lex Fridman (53:32.920)
this particular periodic table of particles that we see?
Lex Fridman (53:36.440)
Is it possible that the deeper order includes
Harry Cliff (53:40.240)
like almost a single entity,
Lex Fridman (53:42.400)
so like something that I guess like string theory
Harry Cliff (53:44.960)
dreams about, is this essentially the dream,
Lex Fridman (53:50.240)
is to discover something simple, beautiful and unifying?
Harry Cliff (53:54.120)
Yeah, I mean, that is the dream,
Lex Fridman (53:55.640)
and I think for some people, for a lot of people,
Harry Cliff (53:59.480)
it still is the dream,
Lex Fridman (54:00.400)
so there's a great book by Steven Weinberg,
Harry Cliff (54:03.800)
who is one of the theoretical physicists
Lex Fridman (54:05.760)
who was instrumental in building the Standard Model,
Lex Fridman (54:08.360)
so he came up with some others with the electroweak theory,
Lex Fridman (54:12.000)
the theory that unified electromagnetism and the weak force,
Lex Fridman (54:14.560)
and he wrote this book,
Lex Fridman (54:15.680)
I think it was towards the end of the 80s, early 90s,
Harry Cliff (54:18.080)
called Dreams of a Final Theory,
Lex Fridman (54:20.000)
which is a very lovely, quite short book
Harry Cliff (54:22.920)
about this idea of a final unifying theory
Lex Fridman (54:26.200)
that brings everything together,
Lex Fridman (54:27.560)
and I think you get a sense reading his book
Lex Fridman (54:29.440)
written at the end of the 80s, early 90s,
Harry Cliff (54:31.760)
that there was this feeling that such a theory was coming,
Lex Fridman (54:37.760)
and that was the time when string theory
Harry Cliff (54:39.200)
was very exciting, so string theory,
Lex Fridman (54:41.960)
there's been this thing called the superstring revolution,
Lex Fridman (54:44.080)
and theoretical physicists were very excited,
Lex Fridman (54:46.080)
they discovered these theoretical objects,
Harry Cliff (54:47.960)
these little vibrating loops of string
Lex Fridman (54:49.440)
that in principle not only was a quantum theory of gravity
Lex Fridman (54:52.440)
but could explain all the particles in the Standard Model
Lex Fridman (54:54.840)
and bring it all together,
Lex Fridman (54:55.760)
and as you say, you have one object, the string,
Lex Fridman (54:59.520)
and you can pluck it, and the way it vibrates
Harry Cliff (55:02.560)
gives you these different notes,
Lex Fridman (55:03.840)
each of which is a different particle,
Lex Fridman (55:05.960)
so it's a very lovely idea,
Lex Fridman (55:08.160)
but the problem is that, well, there's a few,
Harry Cliff (55:11.920)
people discover that mathematics is very difficult,
Lex Fridman (55:14.680)
so people have spent three decades or more
Harry Cliff (55:17.640)
trying to understand string theory,
Lex Fridman (55:19.120)
and I think if you spoke to most string theorists,
Harry Cliff (55:21.520)
they would probably freely admit
Lex Fridman (55:22.640)
that no one really knows what string theory is yet,
Harry Cliff (55:24.920)
I mean, there's been a lot of work,
Lex Fridman (55:26.000)
but it's not really understood,
Lex Fridman (55:27.320)
and the other problem is that string theory
Lex Fridman (55:31.240)
mostly makes predictions about physics
Harry Cliff (55:34.040)
that occurs at energies far beyond
Lex Fridman (55:36.560)
what we will ever be able to probe in the laboratory.
Harry Cliff (55:40.600)
Yeah, probably ever.
Lex Fridman (55:42.200)
By the way, so sorry to take a million tangents,
Lex Fridman (55:44.840)
but is there room for complete innovation
Lex Fridman (55:48.080)
of how to build a particle collider
Harry Cliff (55:50.240)
that could give us an order of magnitude increase
Lex Fridman (55:52.720)
in the kind of energies,
Lex Fridman (55:55.200)
or do we need to keep just increasing the size of things?
Lex Fridman (55:58.520)
I mean, maybe, yeah, I mean, there are ideas,
Harry Cliff (56:00.920)
to give you a sense of the gulf that has to be bridged.
Lex Fridman (56:03.920)
So the LHC collides particles at an energy
Harry Cliff (56:09.320)
of what we call 14 tera electron volts,
Lex Fridman (56:13.440)
so that's basically the equivalent
Harry Cliff (56:15.040)
if you've accelerated a proton through 14 trillion volts.
Lex Fridman (56:19.200)
That gets us to the energies
Harry Cliff (56:20.520)
where the Higgs and these weak particles live.
Lex Fridman (56:23.240)
They're very massive.
Harry Cliff (56:24.480)
The scale where strings become manifest
Lex Fridman (56:27.760)
is something called the Planck scale,
Harry Cliff (56:29.320)
which I think is of the order 10 to the,
Lex Fridman (56:31.960)
hang on, get this right,
Harry Cliff (56:33.720)
it's 10 to the 18 giga electron volts,
Lex Fridman (56:35.840)
so about 10 to the 15 tera electron volts.
Lex Fridman (56:41.000)
So you're talking trillions of times more energy.
Lex Fridman (56:44.760)
Yeah, 10 to the 15th or 10 to the 14th larger, I don't even.
Harry Cliff (56:49.760)
It's of that order.
Lex Fridman (56:50.840)
It's a very big number.
Lex Fridman (56:52.680)
So we're not talking just an order
Lex Fridman (56:54.400)
of magnitude increase in energy,
Harry Cliff (56:55.600)
we're talking 14 orders of magnitude energy increase.
Lex Fridman (56:58.600)
So to give you a sense of what that would look like,
Harry Cliff (57:01.160)
were you to build a particle accelerator
Lex Fridman (57:03.000)
with today's technology.
Lex Fridman (57:04.760)
Bigger or smaller than our solar system?
Lex Fridman (57:07.960)
The size of the galaxy.
Harry Cliff (57:09.120)
The galaxy.
Lex Fridman (57:10.040)
So you'd need to put a particle accelerator
Harry Cliff (57:11.480)
that circled the Milky Way to get to the energies
Lex Fridman (57:14.560)
where you would see strings if they exist.
Lex Fridman (57:17.600)
So that is a fundamental problem,
Lex Fridman (57:20.400)
which is that most of the predictions
Harry Cliff (57:22.600)
of these unified theories, quantum theories of gravity,
Lex Fridman (57:26.040)
only make statements that are testable at energies
Harry Cliff (57:29.200)
that we will not be able to probe,
Lex Fridman (57:32.200)
and barring some unbelievable,
Harry Cliff (57:35.200)
completely unexpected technological
Lex Fridman (57:37.160)
or scientific breakthrough,
Harry Cliff (57:38.080)
which is almost impossible to imagine.
Lex Fridman (57:40.000)
You never say never, but it seems very unlikely.
Harry Cliff (57:42.800)
Yeah, I can just see the news story.
Lex Fridman (57:45.120)
Elon Musk decides to build a particle collider
Harry Cliff (57:48.840)
the size of our galaxy.
Lex Fridman (57:51.080)
We'd have to get together
Harry Cliff (57:51.920)
with all our galactic neighbors to pay for it, I think.
Lex Fridman (57:55.120)
What is the exciting possibilities
Lex Fridman (57:56.720)
of the Large Hadron Collider?
Lex Fridman (57:58.960)
What is there to be discovered
Lex Fridman (58:00.640)
in this order of magnitude of scale?
Lex Fridman (58:04.160)
Is there other bigger efforts on the horizon in this space?
Lex Fridman (58:09.800)
What are the open problems, the exciting possibilities?
Lex Fridman (58:12.720)
You mentioned supersymmetry.
Harry Cliff (58:14.560)
Yeah, so, well, there are lots of new ideas.
Lex Fridman (58:17.600)
Well, there are lots of problems that we're facing.
Lex Fridman (58:18.920)
So there's a problem with the Higgs field,
Lex Fridman (58:20.160)
which supersymmetry was supposed to solve.
Harry Cliff (58:23.320)
There's the fact that 95% of the universe
Lex Fridman (58:25.720)
we know from cosmology, astrophysics, is invisible,
Harry Cliff (58:29.360)
that it's made of dark matter and dark energy,
Lex Fridman (58:31.840)
which are really just words
Harry Cliff (58:33.520)
for things that we don't know what they are.
Lex Fridman (58:35.360)
It's what Donald Rumsfeld called a known unknown.
Lex Fridman (58:37.920)
So we know we don't know what they are.
Lex Fridman (58:39.880)
Well, that's better than unknown unknown.
Harry Cliff (58:42.480)
Yeah, well, there may be some unknown unknowns,
Lex Fridman (58:43.800)
but by definition we don't know what those are, so, yeah.
Lex Fridman (58:47.360)
But the hope is a particle accelerator
Lex Fridman (58:52.480)
could help us make sense of dark energy, dark matter.
Lex Fridman (58:55.560)
There's still, there's some hope for that?
Lex Fridman (58:57.680)
There's hope for that, yeah.
Lex Fridman (58:58.760)
So one of the hopes is the LHC could produce
Lex Fridman (59:01.400)
a dark matter particle in its collisions.
Lex Fridman (59:03.800)
And it may be that the LHC
Lex Fridman (59:08.360)
will still discover new particles,
Harry Cliff (59:09.920)
that it might still, supersymmetry could still be there.
Lex Fridman (59:11.920)
It's just maybe more difficult to find
Harry Cliff (59:14.320)
than we thought originally.
Lex Fridman (59:15.640)
And dark matter particles might be being produced,
Lex Fridman (59:18.520)
but we're just not looking in the right part of the data
Lex Fridman (59:20.600)
for them, that's possible.
Harry Cliff (59:22.120)
It might be that we need more data,
Lex Fridman (59:23.320)
that these processes are very rare
Lex Fridman (59:24.800)
and we need to collect lots and lots of data
Lex Fridman (59:26.600)
before we see them.
Lex Fridman (59:27.600)
But I think a lot of people would say now
Lex Fridman (59:29.880)
that the chances of the LHC
Harry Cliff (59:33.720)
directly discovering new particles
Lex Fridman (59:36.000)
in the near future is quite slim.
Harry Cliff (59:37.760)
It may be that we need a decade more data
Lex Fridman (59:40.800)
before we can see something, or we may not see anything.
Harry Cliff (59:43.920)
That's the, that's where we are.
Lex Fridman (59:45.480)
So, I mean, the physics, the experiments that I work on,
Lex Fridman (59:48.960)
so I work on a detector called LHCb,
Lex Fridman (59:50.760)
which is one of these four big detectors
Harry Cliff (59:52.760)
that are spaced around the ring.
Lex Fridman (59:54.400)
And we do slightly different stuff to the big guys.
Harry Cliff (59:57.520)
There's two big experiments called Atlas and CMS,
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