The following is a conversation with Don
Lincoln, a particle physicist at Firmeny
Lab, who has spent decades working at
the frontier of high energy physics.
This was a mind-blowing and inspiring
conversation. Don turned out to be one
of my favorite people to talk to about
physics. truly a unique mind with that
Richard Fineman ability of taking very
complicated ideas and explaining them
simply without losing any of the
essential brilliant insights at the core
of those ideas. This is the Lex Freedman
podcast. To support it, please check out
our sponsors in the description where
you can also find ways to contact me,
ask questions, give feedback, and so on.
And now dear friends, here's Don
Lincoln.
In describing the search for theory of
everything in physics, you describe the
history of physics can be told
effectively as a kind of history of
unifications.
There's this centuries long quest to
show that these distinct phenomena are
actually linked by some unified
underlying principles. uh even starting
with Newton that you can think of the
effort of physics as one as trying to
unify the laws of nature. So I was
wondering if we could talk through the
history of unification that lens of
physics. There are of course lots of
different ways to do physics, but the
the way that I would say that particle
physicists, cosmologists do is they are
trying to to really find basically the
underlying principles that govern the
laws of of nature. If we go back say to
the I don't know 1650s or so, uh you're
the most brilliant person around and
you've noticed two things. One you've
noticed is that when you trip, you fall.
That is the nature of gravity that that
we all experience daytoday. But then
there's sort of astronomy where you look
out at the heavens and you see the stars
march across the sky. You see the
planets move through the stars and there
that seems to have absolutely nothing to
do with what happens when you drop your
sandwich and and the dog grabs it from
you. So
>> yeah,
>> the brilliant thing was when Newton
looked at that and he thought about
maybe the moon is falling but it's
missing the earth. So what we had is
that in maybe 1650 you had what we might
call the laws of celestial gravity, the
gravity that governs the heavens and
terrestrial gravity, the gravity that is
here on Earth. Now we don't think of
that that way anymore. We think of it as
just gravity. But at that time that
wasn't at all obvious. And in fact, if
you look in the books, Newton's theory
is Newton's law of universal gravity.
The universal is there. And the reason
is is because he realized these two
things that seem to have nothing to do
with one another were indeed one and the
same. I mean, this is absolutely
brilliant. I mean, Newton is arguably
one of the most brilliant humans I of
which I'm ever aware. But at any rate,
it is the first sort of easily to
describe unification of physics that you
can state in a way that sort of makes
sense to to modern humans. I mean, you
can go back farther than that where
people are talking about chemistry, the
nature of atoms. You go back to Democrus
who was wrong about very many things,
but the idea that there was a smallest
particulate form of matter is right. So,
it's kind of funny. You talk, you read
the chemistry books and they say that
the idea of atoms goes back to Democrus
and you know he his idea was that like
um there was a smallest atom of oil
which was smooth and it was smooth of
course because well oil is smooth. There
was a smallest atom of vinegar because
vinegar is tart and it pricks your
tongue so therefore atoms were little
sharp pointy things. Um and so he was
wrong about a lot but he was right about
the idea that there was a small particle
and and we now know a very we have a
very different concept than he did. So
you can go back farther than that but
getting to unification there are more
examples. For instance if you go back to
say 1830 or so scientists were trying to
understand electricity for instance and
there was a lot going on. people really
understood things. But at the time you
would have two phenomena that are
familiar to us now. One is a magnet
which you know at the time mostly
magnets were were simply little pieces
of iron that had been magnetized and
they could stick to steel. And then you
had electricity which was at the time
they were generating little sparks that
they could play and and have fun with or
more broadly a uh a lightning bolt
blazing across the sky. And so when you
think about this, that lightning bolt
and that little magnet seemed to be
really unrelated.
>> Mhm.
>> Um but over the 1800s, a number of
scientists were exploring little aspects
of it. What happens when you run
electricity through a wire? It seems to
make a magnetic field. You know, they
was a whole bunch of experiments and
there were a lot of names. But in about
the 1860s or so, James Clark Maxwell
took all of those ideas that had been
percolating around for the previous 50
years and wrote his laws of
electromagnetism.
And they're really fascinating. If you
look at the laws of electromagnetism,
they are they're differential equations
or integral equations. But basically
what they say is on one side you have a
bunch of terms that have electricity in
them and then you have equals on the
other side a magnetism thing. So
forgetting all of the mathematical
symbols you have electricity side equals
a magnetism side. Electricity equals
magnetism. And that is a staggering
concept. The fact that these two things
a lightning bolt and the magnet that
holds your kids art to the refrigerator
are one and the same. And this was
another case where electricity and
magnetism became unified into
electromagnetism. So now we have two
examples. One, gravity being unified,
terrestrial and celestial gravity, and
then electricity and magnetism. So I
I'll tell you about some more in a
moment. But one thing that's kind of
important because the goal is of course
to to unify everything that if if I
could do what I want to do, I would have
some unified theory that would explain
all the behavior of all energy, matter,
space and time, which is a grand goal.
>> And and we should say that maybe one of
the goals of science more broadly
outside of physics even is to construct
uh models
that can generalize
the world. So if you look at Darwinian
evolution that was a very beautiful
theory that captures another layer of
reality of like how this particular
thing that we see here on earth happens
right
>> so when we talk about theory of
everything in physics that's capturing a
different layer of abstraction about the
functioning of the universe
>> right the whole Darwinian evolution the
fact that our genetics has significant
overlap with genetics of a banana is is
pretty staggering is astonishing that
that works. So that is amazing. Um but
for at least the class of of scientists
that I am what we think of is well sure
biology is interesting and all but when
you get right down to it it's it's it's
caused whatever happens in biology is
caused by the movement of molecules. And
then you say, "Well, that's great and
all, but molecules, they do what they do
because they're made of atoms."
>> And then the next step is, well, you
know, atoms, that's great, but atoms
work the way they do because of the
nucleus and the electrons. And then the
nucleus is protons and neutrons. And so
there are those of us, myself included,
who want to dig down at to the very very
bottom and find out what is the smallest
building block of nature from which all
of these other far more complex and
interesting and abstract things are, but
what is at the very very bottom? And
also that's great, but if you know um
what the smallest building blocks are,
that doesn't tell you the story. That's
like having a whole bunch of Legos but
not knowing how to put them together.
You also need to know how they interact,
how they work. And so that's what we
study forces. So there are the various
subatomic forces of which we're
familiar. And um for instance,
electricity and magnetism are components
of electromagnetism which then governs
the behavior of things like this is
amazing. Electric electromagnetism
explains of course electricity magnetism
but it explains how light works. It
explains how much of chemistry works. So
electromagnetism 1860 or 70 uh the
wonderful thing about that is if you
take Maxwell's equations and you apply a
little bit of calculus it's very easy to
see that the laws of electricity and the
laws of magnetism combined together
make what's called a wave equation which
that's shows that these electric and
magnetic fields oscillate. they they
vary. And if you have a something that's
varied, that's a wave. And the wave then
moves. And if you do the math, you find
out that the speed at which these waves
move is the speed of light. And so
people said, "Wow, the speed of light
comes out of those equations." And that
had to be, I think, very persuasive. And
of course, electromagnetism also plays a
really significant role in chemistry
because after all, atoms are held
together by electromagnetic forces.
There's more to how atoms work. There is
all the quantum mechanic stuff. But if
you did not have electromagnetism or if
electromagnetism was very different,
then atoms would be very different. So
it plays a very big role in in holding
us together. So it it's a a staggering
advance in science to have a good
behavior on that. And of course
being able to to tame electromagnetism
is why people can hear you when you do
your podcast because through the
miracles of the internet just or just
electricity running the computers. I
mean, this is a case, if I can get on a
small soap box, where people back then
said, "Well, why are you messing around
with magnets and sparks and who cares?"
Well, that very
fundamental digging into the laws of
nature has spin-offs. And it has
spin-offs. One of the big spin-offs is
our entire technological society.
without being able to govern
electricity, we'd still be farmers and
shoemakers in cities, but we certainly
would not have everything that we do.
So, off my soap box, but it's really a
lovely thing to show how this this
digging into deep fundamental, not
understood, mysterious things can 100 or
200 years later transform the world. And
the type of science I do now, people
often ask, well, what good is knowing
about how the inside of atoms work, how
the inside of quarks work. And I don't
know the answer to that. Um, but just
being a little more pragmatic, if I go
back, say, hundred years, where people
were trying to understand how the
protons and neutrons inside atoms held
together, how they split, how they they
how you could combine them and so forth.
This has led to nuclear power. Now,
whatever you think about nuclear power
and some people like it and some people
don't, but it is powerful. It will
generate uh energy for humanity and and
it may be that is the path that that we
take as we move away from digging fossil
fuels out of the ground. Humanity is
going to need power no matter what.
Nobody is going to go back to the way
things were in the 1700s. And one
enormous source of energy that is there
for us to take if we so choose is the
modification of the nucleus of atoms
seem to have absolutely nothing to do
with anything. And yet it provides
humanity with an opportunity which of
course requires that we think carefully
of how we do that and and if we want to
but it gives us something that we didn't
have before. Yeah, it's very clear that
nuclear fusion and nuclear fision will
unlock huge amount of energy that's
required for a civilization to flourish.
But that's almost like near-term.
>> Mhm.
>> Longer term, you can think about things
like we'll talk about dark energy crisis
and antimatter. Maybe if you figure out
some of the mysteries around antimatter,
that too would lead to energy sources,
how to produce energy, that too might
lead to counterintuitive propulsion
systems
>> for us humans to travel through through
the universe. Now, right now it seems
farfetched, too expensive, too
complicated, too difficult. But
breakthroughs in the fundamentals
theoretical physics might lead us to
unlock some incredible energy sources,
incredible technologies that uh will uh
allow humans to explore the universe.
And of course, we should also mention
that as always with technology, it's a
double-edged sword. It will most likely
lead to the development of more
dangerous weapons or other sources of
harm. And then we uh as a civilization
kind of have to walk that uh line and
hope we figure out how to do more good
than bad with the technologies we built.
>> Right? But but we have to really
remember while people worry about
nuclear weapons which are admittedly
very dangerous and even nuclear power
which has waste that has to be dealt
with.
What science is doing is
working out finding power that nature
has presented to us. This is not new.
Fire is like that too. Fire can burn
down your house or it can cook your
steak. Power is like that. And that's
just something that we have to
understand as humanity. And that's why
this needs to be a you know when we talk
about science it has to be a broad
conversation by all of society because
what scientists can do is figure out how
the world works. Society has to figure
out how we wish to apply that or not
apply that.
>> Also solving the mysteries and the
puzzles of the universe in itself is
effing awesome.
>> It is. It is. So, I mean that that's the
thing that makes us human in part is
looking at a thing and saying, "How does
this work?" And then together, uh, a
bunch of apes get together like poke the
thing, kind of shake the thing,
>> and then over time you have rockets
going out into space, you build roads
and bridges, you build the internet.
Anyway, so we talked about Newton, we
talked about Maxwell. That takes us in
the 20th century in terms of
unification. There's a guy named
Einstein on whom you wrote a book who
did quite a lot of progress on the
effort of unification.
>> Sure. So Einstein, he's a pretty amazing
guy. In 1905, he had his miracle year
where he wrote multiple papers. The one
that most people know about is special
relativity where he showed something
that makes no sense to anybody who's not
really dug into it very hard. And that
is that two people experience time
differently. Time, you know, is a
fascinating thing. We don't really
understand what time is, which is weird.
You think that that'd be something we'd
understand very well, but we really
don't. We know a lot about it, but
really understanding it, not so much.
But, um, Newton thought that time was
just universal for everyone. So my time,
your time, some person's time on Mars or
on Alpha Centator, everybody experienced
time the same. What Einstein showed was
that that wasn't the case. That
different people moving at different
speeds with respect to one another
experience time differently, which is
absolutely a mindblowing concept. Now,
most people think that Einstein then
said, well, he invented spaceime that
that space and time are the same thing.
and he was behind that. But that actual
insight came from one of his teachers, a
guy by the name of Minowski, who looked
at Einstein's equations. Mowski was a
little bit more mathematically inclined
than Einstein. And he saw that if you
look at the equations, you have
basically one person's space and time
equals some numbers times this person's
space and time. And so that's kind of a
a staggering thing. So, so that is where
Einstein and Manowski really did this
unbelievable concept that that space and
time are actually pretty much the same
thing that runs a foul of our
understanding of how the world works
because time just moves. It's
continuous. We we know what it is at a
visceral level
and an experiential level. We might not
understand it at a formal level, but we
know what time is. It's what keeps makes
today today and not yesterday or
tomorrow. Space is a little different.
You can walk somewhere, you can walk
back, you can move around. You have more
freedom to move in space than you have
to move in time. You can always move
forward in time. It's just moving
backwards. It turns out to be a little
more difficult. But yeah, Einstein's
understanding that that is the case, it
caused everybody to think about the
world very very differently. And that
was in 1908 when Minkowski really laid
it out in the strict spaceime.
>> Uh and that also led to the work on
special relativity led to the speed
limit, the speed of light.
>> Well, it was a premise. He had two
premises. One was that the laws of
nature are the same for everybody. So if
you're moving at some speed or if I'm
moving at some speed, I can say I'm not
moving and saying you're moving at some
speed. That's not controversial. That is
what we call Galilean relativity. It's
from hundreds of years ago. But what
Einstein said that was controversial was
that everybody measures that the speed
of light is the same irrespective of how
we're moving with respect to each other.
You'll measure the speed of light to be
a number. I'll measure the speed of
light to a number. And that's very very
different from what Newton would have
said or Galile or any of the old guys.
And it was taking those two things
together that caused all of the
weirdnesses of special relativity. Now
you could then very easily say, well
that second premise that everybody
measures the speed of light to the same
is just dumb and that you know you could
test that. So that's where testing
relativity comes in and Einstein's
equations which include those two
assumptions it predicts the behavior of
everything perfectly well. Now we've
actually measured
uh done experiments where we can say
that the speed of light is the same for
everybody. That's not how that's been in
the beginning. It was really that
assumption leads to predictions. The
predictions are true. So the assumption
is true. Now there is a for for those
people for your viewers who want to say
well how do you measure that the speed
of light is the same for everyone the
particle physicists do this and the way
you do this is the following there are
some subatomic particles that when they
decay they emit light that's their decay
product and so you collide two things
together so you know when the particle
was created then you have surround your
collision point by a detector and you
measure how long it takes for light to
get to your detector and by God it's the
speed of light which it should be.
However, sometimes in these collisions
some of these subatomic particles you
make are coming out at very high speed.
They might be coming out at 95 or 97 or
very large fraction of the speed of
light and then they decay into photons.
And so you measure how long it takes for
the photon to get to your detector and
it says it's light travels at the speed
of light. Now if it were that
if Einstein's conjecture was incorrect,
you'd have a particle coming out at near
the speed of light. It would be decaying
into a particle traveling at the speed
of light. Then that particle should have
traveled at say two times the speed of
light or something like that. So it
should have taken half as much time to
get to the detector. But it doesn't. So
this is a hard serious measurement that
shows that something you know we we can
measure the speed at which light comes
out of this stationary created particle
and it's the speed of light then we can
measure what the speed is of it coming
out of something that's moving and it's
still the speed of light. So that is an
actual measurement but that is not
something that was possible in
Einstein's day but it is now. Just to
take a small tangent. Uh how weird is it
in the full ranking of weirdness that is
physics? How weird is it that there's
that speed limit of this speed of light?
>> Well, I have to tell you, when I first
encountered this, it's pretty freaking
weird. It's like pegs the weird meter.
But as you become more familiar with it,
as you become more more comfortable with
the idea, the thing to remember is the
speed of light. It's the speed of light
through spaceime. Once you embrace that,
that makes a whole ton of sense. It all
of a sudden makes everything fall much
more into place. I think that there is
an ultimate speed isn't that shocking.
It just simply says that it's a property
of space in the same way that there is
you know space can can transmit a
certain strength electric field. like
trans it can support a certain things
whatever space is and we don't know what
space is but whatever it is it has the
capability of of transmitting these
things at that one speed through space
or time and everything else comes from
our insisting that we keep space and
time different that's that's how I view
it and at least for me that once I
accepted that it all became very
comfortable
>> so The nature of my question actually
here that will apply over and over
>> is trying to empathize, trying to put
ourselves in the shoes of the people
before space and time are unified into
spaceime
>> and and really experience and think
through how difficult of a leap is that
>> huge.
>> The reason I I sort of say that is we
are now in the modern day in the 21st
century and of course we're going to
have to make leaps like that in our
future. Mh.
>> So what are the unifications we're not
seeing in front of our eyes? So for
example, there's so many examples
through through your work, through your
lectures of um uh Paul Durak taking
antimatter seriously.
>> Mhm.
>> Looking at what the math shows and
saying, I really think this thing
exists,
>> right?
>> I mean, it just sounds insane.
>> It does.
>> And so I think this is a good warm-up.
The space-time unification is a good
warm-up as we march through the 20th
century because it gets uh in my view at
least weirder and weirder even with
Einstein himself.
>> Well, let me give you an even more basic
example. Sodium and chloride.
Sodium is an explosive metal. You put it
in water and and it's kind of neat. You
put it in water and it just it doesn't
quite explode, but it gets hot and it
pops around. Chlorine, it's a gas. It's
going to kill you. So these two things
are deadly. They're awful. And yet when
you mix them, you put it on your food at
night. Salt, right? And so this is a
case where where this whole a
unification and b this deeper
understanding in this case of chemistry
of how two things that that are
dangerous can be brought together and
turned into something not only innocuous
but necessary for human life. And so
this is not unusual that what what
you're describing. I mean when you think
about it, forget about everything else.
Just the fact that you know we tell
little kids little kids that the world
is made of atoms. Now that's crazy. Most
people have never seen atoms and yet
nobody really doubts it anymore. And I
think it's just a a case of of
familiarity and then the culture slowly
accepts it and it's then it's real even
without the evidence. In fact, one of
the courses you described there, um, how
we know what we know. I think that's a
valid question. How do we know there are
atoms? And, and of course, there are
ways we do. And by the way, on that
front, I would love to go through how we
know the building blocks in the universe
as we march towards quirks. That in the
course that you mentioned is one of the
most fascinating things of this
philosophy of atoms being around for a
very long time. Then you concretize and
you actually can prove or have
strong observations that indicate that
there is atoms and then there is a
nucleus, there is electrons, there is
photons, there is quarks and I mean it
gets weirder and weirder and now we're
facing the mystery. Is there building
blocks even smaller than that? But
anyway, Einstein turns out didn't just
do special relativity. By the way, I I
really think he deserves three Nobel
prizes. He got it for photoelectric
effect. The fact that he didn't get it
for general relativity is a crime
against humanity. I don't understand.
Obviously should have gotten it for
general relativity and and special
relativity. I mean I think special
relativity is separate for general
relativity in ter as far as Nobel prizes
go. Uh so general relativity is another
unification.
>> Yes, that's right. What Einstein
realized was that if you were in a
rocket ship and the rocket ship was a
very quiet rocket ship and it was
accelerating, it would feel like you're
experiencing gravity. And so, as as you
say, it's one of his happiest moments
when he realized that acceleration and
gravity feel very much the same. What
I'm impressed by is that idea, which is
already a pretty neat idea,
somehow led him to take his space-time
idea, take this acceleration gravity
idea and realize that he could describe
gravity as the bending of spacetime.
Spacetime being constant like east,
west, north, south, that's already hard
enough. But now he's saying, well, you
know, take your your map and crinkle it
and bend it and so forth and that's
gravity. That is a staggering
mind-blowing idea.
>> I guess I wonder if you can comment on
what do you think is the idea generation
process that leads to that. So it
probably in Einstein case has to start
with what if gravity is itself
space-time geometry. You you have to
have a thought like that, right?
>> Yes, I think so. There's a lot about
science. There's of course knowing what
went before. There is knowing the
mathematics that allows you to figure
out the implications of your theory.
There is the discipline to argue with
yourself and other people because most
ideas are wrong. But then there's what
you just described that intuitive spark
and that is something that is very very
difficult to to create. There's a reason
that we venerate these people is because
it is an unusual
feature and most people only have that
aha moment once in their lifetime if
they have it at all. Mhm.
>> And then there's a tricky business
because I'm sure you do and I get a lot
of letters from from creative thinkers
who don't have all of the the history
and the mathematical discipline and the
the self, you know, self-critique that's
necessary. Um, and so they come up with
these ideas and often it's easy to see
where they just don't play out. Um so in
order to be that person who changes the
way we see the world, ideas themselves
are not enough. These these creative
ideas that's not enough. You need it
with the discipline and the critique.
And it's that amalgam of those things
that you know make you a genius that
that history remembers.
>> But it's hard to know in in a field of
people you might uh be tempted to call
crazy, there could be geniuses there.
And it's hard to know which is which. We
should mention that Einstein himself
couldn't see the genius in quantum
mechanics initially. Couldn't see the
the correctness, I should say. So he
could see the the insanity of
gravity bending spacetime, but quantum
mechanics was too weird for Einstein.
>> In all fairness, it's weird for me, too.
But um
>> but the thing is even while that is true
and Einstein maybe spent the last few
years of his life trying to to blend um
electricity and magnetism, gravity in a
a single thing and he was unsuccessful
but he still was a very very valuable
critic of quantum mechanics. It's not
that he didn't understand it because he
did understand it. He thought about the
implications and all this quantum
entanglement business. Well, not all of
it, but he was responsible for saying,
well, if you're right, then this. And of
course, then people went out and found
out that that Einstein's implication of
quantum mechanics was real. And so they
could say, see, quantum mechanics is
real. So, you know, he was thinking
deeply about it. And he was doing
exactly that thing I said. There's that
spark idea, but there's that critique
idea. And if you're able to critique an
idea, you might kill it. And that is
it's always depressing when I have this
brilliant idea and it gets killed, but
it's better to be killed than to keep it
around and waste time on it. Um, and so
he was in that case not generating the
the aha, but he was saying is, "All
right, let's take your aha. Let's see
it's right. What does it mean? It means
this." that allows people to go test it.
And so he was contributing very
crucially
to that other part of scientific
advancement, which is not just the aha
moment, but the beat it to death, test
it, critique it, and make sure it's
real. And it's only after all of that
has been done that you really are sure
you're right. And that's why science is
such a a powerful tool. It is that that
combative just downright kind of jerky
critique that most people don't like.
They don't like people saying your
ideas, you know, might be wrong.
But that is it is crucial. It is crucial
part of the scientific process.
>> Plus, there's that quote on the other
side of it that I've heard you mention
which is uh you know, I believe your
idea is crazy, but is it crazy enough?
Was that
>> Yes. Yes. We all agree that your idea is
crazy, but is it crazy enough?
>> And there is some degree of taking those
leaps uh of crazy, but it has to be
backed with rigor,
>> right?
>> And the unifications continue that as we
uh take steps towards the standard
model, which is such an incredible part
of of physics in the 20th century. So,
can you describe that unification?
>> So, you know, we're sort of jumping
forward here now to the 1930s or
thereabout. And at by that time people
had realized that there are four
distinct forces that do not seem to be
connected. One is gravity, two is
electromagnetism, and those are things
people are relatively familiar with. But
there are two other forces that only
have any real importance inside the
nucleus of atoms, which is why most
people have no experience with them. One
is the strong nuclear force which holds
the nucleus of the atoms together and
the other one is what we call the weak
nuclear force which is responsible for
some types of of radioactivity. And
since most people don't play around with
nuclei and most people don't play around
with radioactivity, they don't know what
that is. But um by the 30s scientists
had done enough experiments, done enough
theorizing to to say that there were
these four forces and that was already a
triumph. I mean we in our goal for a
theory of everything we'd like to think
that there is one force which is what
we're talking about the unification.
Maybe these four forces are are just
different ways of looking at a single
underlying force. But in the 30s that's
where we were. there were the four
forces.
So we move ahead and in the late 50s and
early 60s some people were thinking that
maybe the weak nuclear force and
electromagnetism
actually were the same. So they were
working on trying to bring together
these two forces to show that they're
connected. And it came true. They were
able to show that electricity and
magnetism were actually two different
facets of a single force that we now
call the electroeak force. Mhm.
>> Now, the story that you're told in in
articles about this about what you
people have called the Higs Bzon or the
God particle, the story is very very
simplified
because in 1964
the um there were three groups with six
individuals who came up with important
papers talking about what's called the
Higsfield. I'll get to back get to what
that is in a minute. But the Higsfield
is important. But it wasn't until 1967,
so 3 years later, that Steven Weinberg
and and some others actually unified
electromagnetism and the weak force.
Sheldon Glashau, Abdul Salam and Steven
Weyberg successfully unified
electromagnetism and the weak nuclear
force that uh showing that high energies
uh these two forces were merged into a
single electroeak force,
>> right? And that was in ' 67. All right.
Um everybody talks about this thing
happening in ' 64, but it it really
wasn't. It happened over quite a few
years actually. But all right. So now
let's what you said is true. So um uh
Weinberg, Glacial and Salam showed that
electromagnetism in the weak force at
high energies were the same. There was a
problem however and the problem is that
electromagnetism has an infinite range.
Um and we know that because we can see
stars that are millions of light years
away. I mean that shows you that the
range of that force is essentially
infinite.
>> The weak force however um basically
becomes non-existent on distances much
smaller than the size of a proton.
>> Mhm.
>> So that you know to say oh they're the
same and yet one can reach across the
universe and one can't reach out of an
atom. Well that's just dumb. I mean the
obvious
thought here is well we just proved that
that whole idea is stupid so throw it
away ridiculous. And that is where these
ideas from 1964 came in and saved the
day. So how can it be true
that the electroeak force is real and
electromagnetism
and the weak force act so differently?
The way that could happen is if these
forces were transmitted by a particle
moving from one subatomic particle to
the other. In the case of
electromagnetism, it's the photon. In
the case of the weak force, we call them
now the W and Z particles. So the idea
is that that Higgs and his colleagues
came up with is saying all right
electroeak force is real.
The way we make it so that there is now
an electromagnetic force and a weak
force is the force carrying particle of
electromagnetism has no mass. The force
carrying particle of the weak force has
a mass. And so what was done is a field
was postulated that there was this
additional field that was kind of
distinct from this electroeak field and
we call it the Higs field. And the Higs
field permeates all of space.
And and here's the kicker, some
particles interact with a field and some
particles don't interact with a field.
The ones that interact with the field
get mass and the ones that don't
interact with the field don't have mass.
And so that's the idea is that the Higs
field gives the weak force particles
mass. However, the photon laughs at the
Higs field, doesn't see it, and it has
no mass. And I should say here, going to
perplexity, the big picture view, the
Higs field is a quantum field that fills
all of space and gives many elementary
particles. Just as you're saying their
mass through their interaction with it,
the Higs Bzon is the particle associated
with ripples or excitations of this
field. In modern particle physics, every
type of particle corresponds to a field
that exists everywhere. The Higs field
is one such scalar field, meaning at
each point in space, it has a single
numerical value rather than a direction.
The Higs field differs from most other
fields because even in empty space,
empty in quotes by the way, empty space,
it's uh average value is not zero. This
nonzero vacuum value is what enable it
to endow particles with mass.
>> Right? So let's talk about something a
little more familiar just to to try and
hang some some intuition on those words.
All right? So right in front of us there
is a gravitational field. Now, you can't
see it, but right there. Right there.
Check it out.
>> Yep.
>> If I were to take something, a pen or
whatever, and put it there, it feels a
force and a falls.
>> Mhm.
>> Very insightful. I know. So, we have the
gravity field and we have the pen that
has a mass. And the mass and the gravity
field interact and it drops. Now, if we
had another
>> I have uh object for you demonstration
purposes,
>> performance art. Here we go. This is
great.
>> This thing has mass and we drop it. How
remarkable. It falls. But when we step
back and think about what really
happens, it's the mass of this thing and
the interaction with this invisible
field we see here. That's what gives
this weight.
>> Now, I have this particle here that you
can't see, but it's there. It has no
mass and I leave it there. Well, since
it has no mass, it doesn't feel gravity.
It's still floating there.
And that is really all the Higs field
is. Some particles have effectively what
you could call the Higs charge that
interacts and sees the field and other
particles don't. And that is really what
what what you read just basically means.
Now it's kind of neat because in the
ordinary day there is a Higs field right
there and the Higs field is not zero
just like gravity is not zero and things
will get mass but at super high energies
the Higs field the strength of the Higs
field goes to zero so whether things
have mass whether they have a Higs
charge or not they have no char or they
have the Higs charge Higs field zero
they don't interact it has no mass so
that's kind of what uh Weineberg and
Salam Glass show said is at very high
energies, the Higs field is zero. Since
the Higs field is zero, the weak force
particles don't feel mass and therefore
they can travel at the speed of light
just like the photon does and
everything's happy.
>> Mhm.
>> It is when the universe cooled down
after the big bang. It was very hot,
very high energy. Nothing had mass. the
universe cooled and at a certain
temperature what happened is the Higs
field turned on and at the moment it
turned on it gave mass to the weak force
particles did not give mass to the
photons. So that's what we call
electroeak symmetry breaking. So, it's a
mouthful, but all it says is there was a
moment in time early in the history of
the universe at 10 the -12 seconds after
the big bang, the Higs field turned on
and particles got mass. So, that's the
whole idea. So, this is another really
neat thing. So, the electroeak symmetry
theory doesn't need Higs because that
only really applies at very very high
energies. But in order to make it work
at low energies, you need to fix the
theory. And you need to fix the theory
by effectively putting a band-aid on the
theory. Higs theory is just a band-aid
on top of electroeek symmetry theory.
And that is the band-aid that fixes it
because it gives mass to particles at
low energy. Well, how does then Higs
this band-aid the field and uh the Higs
Bzon come into play on the experimental
front on the evidence? Okay.
>> Discovery front. So, what is this uh
Higs Bzon?
>> Okay. Excellent.
>> So, we have never seen the Higsfield.
Higsfield is a hypothetical theoretical
thing.
>> But that is true of of most of our
fields. We've never seen the
electromagnetic field. We've never seen
the gravity field. We've seen the effect
of the field. And so all of these
theories are now what we call quantum
field theories. And that the whole idea
of quantum fields if you have a quantum
field, but that field can vibrate like a
drum head. And so it doesn't vibrate
just exactly like a drum head, but it
vibrates locally. So you can have
specific localized vibrations. And those
specific localized vibrations are the
particles. In the electromagnetic field,
the vibration is the photon. In the Higs
field, the vibration is the Higs Bzon.
And so what we can do is not see the
field, but we can actually excite the
field, make it vibrate and detect the
vibrations. So the Higs Bzon idea was
predicted in ' 64. It became useful in '
67. And then scientists started looking
for it. So in the early 2000s,
people were starting to think that we
had built part particle accelerators
more powerful or powerful enough to
actually to be able to create these
vibrations and detect them. So the
accelerator that was working at the time
was a large particle accelerator outside
Chicago at Firmeny Lab called the
Tevatron.
>> And we were colliding protons and
antimatter protons at near the speed of
light at very high energy. And that was
the accelerator at which the top quark
was discovered in '95.
But we had upgraded our apparatus. We
had 10 times the number of collisions
per second. We had slightly more energy
and we were banging the protons and the
antimatter protons together hoping that
we would actually find the Higs bzon.
>> Can you actually back up a little bit
and look at the bigger picture? So,
Firmy Lab has this legendary accelerator
that there's also a personal story with
you connected to it because I mean
there's a million questions uh I want to
ask you and we'll ask you about some
aspects of that. So, this idea of an
accelerator, the design and the physics
of an accelerator, how is that
productive for understanding
and discovering uh different aspects of
particle physics?
>> Well, I'm so glad you asked.
I mean, this is fascinating. All right,
everybody has heard Einstein's equation
E= MC². Nobody knows what it means.
Maybe they heard that energy equals mass
and mass equals energy. I don't know,
you know, but they've heard the
equation, the most famous equation in
all of science.
But buried inside that equation is a
really thoroughly fascinating concept
that energy and matter are equivalent.
And you can in fact convert movement
energy into mass. And so this is
something that we've known for a long
time. This was predicted back in
basically 1928. So a long time ago,
actually almost 100 years ago. And it is
not in the slightest bit controversial.
We can do this all the time. So the
simplest thing is to take two particles
that have no no structure. So you know
the closest thing you can have to BB's
that are just true mathematical BB's. If
you smash those two things together,
it's coming in with a huge amount of
energy from one direction, a huge amount
of energy from the other direction, the
directions cancel. So the net momentum,
the net energy of this has no motion. So
you have these two things coming in with
a you know exactly balanced energy and
if they collide they could stop. Well
that energy has to go somewhere and that
energy can literally create mass create
particles. Now there are special rules
about what happens if you have two
things coming together and it creates a
particle. It has to create an antimatter
particle to balance it. That's just kind
of the rules of the laws of nature. Why
is that the case? Well, we have some
ideas, but in many respects the answer
is because those are the laws of the
universe and that's the things that we
try to understand. But this is
absolutely true. So what what particle
accelerators do among other things is
simply transform energy into particles.
And so basically any uh particle that
doesn't exist in nature we can make in
this way. You can make the antimatter
electron by taking two particles,
smashing them together. The energy sits
there and it will make an electron and
an antimatter electron and it just does.
And we know that the antimatter electron
was discovered in 1932.
This is all pretty easy. The antimatter
proton was discovered in 1955 at the
Berkeley Bevatron.
And so this is just what you do. You can
convert energy into a matter antimatter
particle. Now the converse goes true and
that's something we might talk about.
You can take matter and antimatter and
bring it together and it'll make energy.
It's the uh the process can go both
ways. Energy can make matter and
antimatter. Matter and antimatter can
make energy. And this is just true. We
do it all the time. There's no question
that this is the case. We should also
mention that uh this is the reason why
Firmeny Lab had a nice stash of
antimatter particles. So as as a side
effect, you can also collect antimatter
in this kind of way.
>> You can produce antimatter, but it's an
extremely costly
>> well very very costly. Um in order at
the Firmeny Lab machine, we would have
to smash 100,000 protons into something
to make one antimatter proton. So I mean
it it took some work. Is there some
extremely precise recipe of uh of being
able to produce particular kinds of
particles and all this kind of stuff
when you smash two things together? Is
there like how can you control
accurately which kind of particles
you're trying to produce? If you want to
make antimatter electrons, you smash
together energy at a certain it's just
easier with electrons because the
electrons to the best of our knowledge
have nothing inside them. So they're
simple. They have a certain mass and
that's that. So if you smash particles
together with the right energy, you can
make them very very easily because you
can it's like a old style radio back in
the day where you had to dial it in. you
could get right on the station and you
could hear the the signal and if you
were off a little it didn't work. The
problem for things like protons and so
forth is they're not pointlike
particles. They're kind of like garbage
cans full of stuff and so it's very
difficult to make antimatter protons.
Now you can get more of them by
increasing the um energy at which you
collide two particles together. If
you're at below a certain energy, the
and you collide, say you collide two
protons together at kind of low energy,
you just don't have enough energy to
make an anti-roton
>> and so it doesn't happen. You get to a
certain energy and you can just barely
make them. The more energy you collide
them together, the more you make. So
that is just sort of how it works. More
is better. And then uh with with CERN if
you compare maybe CERN and Firmayab
going to perplexity here CERN's
accelerator the large hydron collider
LHC is the world's highest energy proton
collider while Firmayab's current and
plant accelerators focus on intense
proton beams for neutrino physics rather
than pushing the absolute energy
frontier. Absolute energy frontier
meaning highest possible energy
smashing of protons together.
>> Correct. So one we were talking about
like accumulating antimatter. Yes. All
right. And so um there that is typically
making anti-roton as opposed to making
all particles in general. So let's focus
on the anti-roton side to begin with.
All right.
>> So formula doesn't make anti-rotons
anymore. We stopped making them in 2011
and it's because we shut our big
accelerator down to concentrate on a
different facet of particle physics.
However, at the time we would smash um
protons with a an energy of 120 GEV and
in that we would make anti-roton. So
that's a ton of energy.
It's true that the CERN accelerator, the
big accelerator, is now much higher
energy than the Firmenab accelerator
was. No problem. But that's not how they
make anti-roton.
The all of these big beam uh big
laboratories, it's not one accelerator.
At Firmay Lab, there were five distinct
accelerators and it was basically like
shifting an old standard car cuz you
couldn't just go zero to super speed in
one accelerator. you had to go from one
to another getting higher and higher.
Well, at CERN, they use one of the
basically their second gear in their
very big accelerator complex to make
antimatter protons. And their
accelerator is only 26 GEV compared to
the 120 GV at Firmeny Lab. Firmay Lab's
not operating, but when it was
operating, it operated at an energy of
about four times higher than what CERN
is doing now. And why is that? Well,
it's because what CERN needs to do is to
not make as many anti-rotons as Firmay
Lab did. They are doing a very different
current experimental program. They're
doing a fascinating experimental program
including trying to figure out does
anti-gravity fall up or down, which is
kind of neat and we sort of know the
answer to that different that's
separate. But anyways, so getting back
to the anti-roton business.
>> Yeah.
>> Well, Firmay Lab doesn't do it now. It
was top dog. It's not anymore. Um, the
only really big anti-roton accelerator
creator is a small accelerator at CERN.
Okay, so that's the anti-roton thing.
And if we get back to antimatter, we
could talk about that because that is
way cool.
>> Yeah. So,
>> now the other side of your thing about
making high energergy unknown particles,
bigger is better. And it is true that
the LHC is a very high energy machine.
It is about seven times more powerful in
terms of energy per collision. It is
also about a hundred times more
collisions per second than the Firmeny
lab machine. So it is true that the LHC
can make bigger heavier
uh particles that the old firm lab the
Tevatron ever couldn't and that is true.
So if you want to look at high energy
stuff, yeah, you go to CERN now. Which
is why many of my colleagues including
myself once we had
measured all of the sort of frontier
measurements we thought we could make
with the Firmeny Lab accelerator, we saw
this bigger, more powerful machine with
seven times the energy and 100 times
more collisions per second. We said,
"Heck yeah, let's go work on that." And
to give you a sense of scale, the top
quark, which is the heaviest particle
ever discovered, discovered at Firmeny
Lab in 1995. There were two discovery
papers and the one on which I was a
co-author. We had worked for a good
chunk of between 6 months and a year of
collecting collisions and there were a
lot of collisions and our paper had 38
top quirk candidates. 38. And we knew
that half of them were crap because when
you make a detector like that, there's
what you call background. So you have
the background and the good stuff. And
we know it was about 50/50. So we had
maybe 19 top quarks after working for
between 6 months and a year of
collecting data. But now at the LHC, we
make a top quark every second.
And that's what higher energy and more
collisions per second will do for you.
That extra energy, you're above
threshold. You make a ton of them. And
when you compare the 1995 Firm Firmab
accelerator to the current CERN
accelerator, it's probably a thousand
times of collisions per second. So it
went from painstaking, pulling teeth to,
yeah, now top quarks are a background.
We try to get rid of them. There's just
too many of them. They get in the way of
searching for the stuff we really want
to search. They are like so 30 years
ago. By the way, is there something to
be said about the the kind of sort of
signal processing here? How you remove
the noise, how you remove the
background, how you determine which
particle is which. There's probably some
like incredible nuance there
>> even outside of the scope of this
conversation.
>> So, let me just throw some numbers out.
All right. So, at the CERN accelerator
when it's operating, the collisions
occur at a prodigious rate. We get about
a billion with a B collisions per
second. Now each one of those Yeah.
Yeah. That's what I said. Wow. Now it
turns out some of them are happening at
the same time. So there's about of order
40 million moments in time per second
where you would take a shot and inside
that moment there might be 20
collisions.
>> So that's why where we get to the
billion.
>> Yeah. But can you individually pinpoint
the collisions
>> sort of to a to a degree. So the beams
are, you know, the when people think of
beams, they think of like laser beams,
but that's not really what particle
beams look like. Particle beams look
like little tiny sticks of spaghetti,
except they're much thinner. They're not
as fat as a stick of spaghetti, and
they're at the LHC. Different
accelerators are different. They're
about this long. And so you have one of
them going one way full of protons and
another one going the other way full of
protons. And they pass through each
other. And as they pass through of each
other, you should think of this as like
a swarm of bees. And this is like a
swarm of bees. And mostly the bees pass
through each other and don't do
anything. But every so often some of the
bees hit nose on and stripes and and and
wings and everything everywhere.
>> That's awesome.
>> And so as they collide through each
other, you know, one collisions here and
one's here and one's here and you can't
tell too much side to side because the
beams are really small. They're sort of
the thickness of a human hair. But you
can see along the direction and there,
you know, this is about the right size.
And so we have detectors around them and
we can actually see, oh, particles came
from here and particles came from here.
And that's amazing. All right. So at any
one crossing, there's maybe 20
collisions. Now, most collisions are
absolutely boring. They're boring
because they are they they exemplify
physics that we know a great deal about
already. We've tested it for for
decades. We know all about it. We don't
care. I mean, it's kind of blas that we
can say, "Oh, yeah, yeah, we're making a
billion partic subatomic particles every
second, but who cares?" Because, you
know, but that's just the way of, you
know, frontier scientists. So, what you
need is you need to pick out the cool
ones, the weird ones, the ones that
nobody's seen before. And so what
happens is uh these things these beams
uh collide and we surround the collision
point within the enormous detector.
There are two absolutely ginormous
detectors at the LHC. One of them called
CMS which is the one I'm on and the
other one is called Atlas
>> which is the other one and we don't
speak of because well no they're both
really amazing.
>> Okay. It's good to know that there's
friendly competition even inside
that's awesome.
>> I mean the fact is they are both amazing
absolutely amazing detectors
>> but CMS is just a little cooler than
>> Oh yeah. Yeah. I mean you know in in in
particle physics we really absolutely
want our competitors to do extremely
well just not quite as well as we do.
>> Got it. All right. So these two giant
detectors
>> right. So but one of them our detector
the CMS detector it's the small one. It
is 70 ft long, 50 ft high, 50 ft wide.
It's 5 stories tall. It weighs 14,000
tons.
>> Small
>> small. Atlas experiment is 150 ft long,
80 ft across. It weighs only 7,000 tons.
Just piece of cake.
>> You could take the Atlas detector and
you could put four of them on a soccer
or football field and it would fill the
field up with just enough room on the
sidelines for the cheerleaders and the
water boy and the coaches and stuff.
That's how big they are. So these are
absolutely ginormous detectors and
basically they're cameras and what they
can do is they can take pictures 40
million times per second. Now all the
data comes streaming off that detector
and we can't record it all. It would
just fill up all of our tapes and it
would be full of all these boring things
we don't care about. So what we do is as
the beams pass through one another, we
teach our detectors to say we only want
one where there are certain
configurations that might be interesting
like there's gobs of energy in the
detector or there's a gob of energy on
one side and nothing on the other side
or there's four gobs of energy or
whatever. These are called triggers. And
so these what we have is fast
electronics that take the 40 million
possible pictures per second and it says
you know about a 100,000 of those are
really cool. We should think about them.
And then it passes not all of the 40
million but those 100,000 to the next
level which are commercial processors
that have uh basically our final uh
analysis code but optimized to run very
very quickly. And what they do is they
do a really quick and dirty analysis to
say to to further refine what's good and
what's not. And that that computer form
then accepts about a thousand collisions
per second and we record those for
further analysis. So that's what's
really happening of the 50 million
possible collisions per second the fast
electronics and then the computers pick
the thousand and then we pass those
through analysis software and hand them
to the graduate students and they pick
through them looking and finding the
handful that are the next Nobel Prize.
So that's how that works and that that
is truly astonishing. I'm hats off to
the accelerator builders, the detector
builders, the the the people who make
the software work, the people who make
the not not gigabytes, not terabytes,
but pabytes of data flow around the
world seamlessly. It's really amazing.
I'm very grateful.
>> Uh so take me to uh July 4th, 2012, the
discovery of Higs Bzon. So this is
really fun because the people searching
for the Higs, it's a it's a community
and the entire community knew that the
LHC was coming online. So even though
many of us had been working on the
Firmenab accelerators, a lot of us were
transitioning to the CERN uh
accelerator. So we were in the very
funny business of wearing our Firmenab
detector people hats trying desperately
to find the Higs Bzon at Firmeny Lab
>> while simultaneously wearing our CERN
hats knowing that CERN was going to be
able to find it if existed. And so you
know we were a little neurotic kind of
wanted you know our old stuff to work
and and there was an awful lot of people
on both experiments. Did you um have a
sense that one of the two places would
be able to find the Higs? First, did you
think the Higs Bzon existed? And second,
did you think that these accelerators
have the chance to find them?
>> So, I was cognizant of the fact that the
Higs Bzon might not exist, but there was
a lot of evidence pointing in the
direction that it might be. I knew that
both experiments, the Firmeny Lab
accelerator and the CERN accelerator
would either find or rule out the Higs
if it existed.
>> Rule out?
>> Well, that's a possibility. I mean,
maybe the Higs theory was wrong.
>> Yeah.
>> Right. Until you until you know it's
there, it might be wrong. It's like dark
matter. People talk about dark matter.
It might not be real.
>> I mean, I it probably is, but it might
not be.
>> So, you knew at these energy levels, you
would be a you should be able to find
the Hig boson.
>> Yes. So that's the nice thing about this
kind of physics because there was a
theory that theory made predictions. Now
there were parameters in the theory we
didn't know if the mass was this we'd
get this thing. If the mass was this we
get this thing. But we could do the the
calculation for every conceivable Higs
mass. And so then we could search look
well let's say the Higs mass is 100 in
some units. Did we see it there? No.
then it's not 100. Well, let's look at
103. Is it there? No. So, we could do
that. Both accelerators could either
find it or definitively rule out the
predictions of simple Higs theory. 100%
guaranteed.
>> However, the CERN accelerator had 10
times the collisions per second and
three and a half times the energy. So
remember when I said it with the top
quirks it was like 6 months for 19
versus one a second. There's no question
the writing is on the wall. The h the
the LHC was going to have an easier time
of it if it was real.
>> However, so but you know I'm a Firmay
Lab scientist and we wanted Firmen Lab
you know come on we want Firm Lab to win
not you know. So we were busting our
butt and we had done what I said. We had
ruled out this region. And we had
certain R mass ranges. We knew it wasn't
there. And we finally said if there was
a Higs Bzon, if it existed, which we
didn't know at the time, its mass was
somewhere between, if I recall, between
like 120 and 145. All right, we'd ruled
out all the other stuff. And so, wearing
our our CERN hat, we said, "Okay, we're
going to find that." But we were really,
really, really trying to do it. Now, if
we had had another 2 years or maybe 3
years of running the Fermy accelerator,
Fermy Lab would have discovered or ruled
out or in this case turning out
discovered the Higs boson because it's a
real thing. We would have found it
without a question, but we didn't have
enough data in July of 2012. We needed a
couple more years. Unfortunately,
in 2008, or fortunately, the LHC had
turned on. It broke. They had to fix it.
Turned on again in 2010. It ran poorly
in 2011. In 2012, they pushed up their
sleeves and said, "Let's do this." And
it turned on. And so, you know, there
was this the Firmy Lab knew if it didn't
have it now, it wasn't it was too late.
Anyways, come 2012 rolls around and um
like two days before
uh the announcement at CERN was July
4th. So two days before that, Firmayab
made a measurement and said we can rule
out certain regions but certain regions
we can't rule out but what we know and
this is important. If the Higs Bzon
exists, it must be in this region for
which we are not capable yet of ruling
out. So that's where we were 2 days
before the LHC said we got it. That was
uh July 4th, 2012. So detecting the Higs
Bzon confirmed the existence of the Higs
field, the mechanism through which
fundamental particles like electrons and
quarks acquire mass in the standard
model. Correct? Although let's be very
specific of what we did then we found a
particle consistent with the existence
of the Higs boson. There were
alternative theories at the time that
predicted not one but multiple Higs
bosons. So there's a theory called super
symmetry which said that there was not
one but five Higs bosons. The standard
original 1964 Higs theory says there
were one. And so all we really knew at
the time was we found a theory. We did
not necessarily confirm that Higs was
right. We found data that said that it
looked like Higs was right. But until we
ran for longer, we were unable to rule
out other alternative theories. So
that's the the deal. Now in the fullness
of time, it is after all uh what 14
years now later, we have been able to
basically rule out some of those other
things. And by now we have validated a
things. We found the mass of the
particle. We know the spin of the Higs
Bzon. It has a spin of zero. We have
discovered Hig Bzon decays. It
preferentially decays into the heaviest
particles. It can through energy
conservation can't decay into top
quarks. It's too light to decay into top
quarks, but it can decay into bottom
quirs. It can decay into W and Z
particles. Can decay into a weird way
into photons. And we have looked for all
of the hypothesized decays of the
original Higs theory. And we have
validated that it decays in those ways
at the rates that theory predicted. And
so now in the fullness of time, I'm
pretty comfortable saying Peter Higgs
and Robert Brout and Franco and his
colleagues, they were right back in the
60s. But we weren't sure on July 4th.
All we knew is we found a particle
consistent. But the thing is with these
discoveries, they're often just barely
discoveries. it takes a while to go and
do the more complex detailed
measurements and that's what we've done.
>> So at the time I remember being called
referred to as the god particle.
>> Uh you also uh had a minor in theology.
So throwing that all together. So
calling it the god particle is speaking
to the importance the potential
importance of discovering this particle.
Do you think uh that is in some degree
justified like if we look at the big
impact of it on the the history of
physics? How important was it to find
and show that the the the Higs fields is
real?
>> Well, I don't think it is as important
as for instance some of Einstein's
stuff. I mean it was it's an important
prediction like the prediction of quirks
was very important and interesting in
validating this. The Higs was kind of
like um validating that quirks existed.
it it's an important stepping stone and
I I do not wish to to denigrate it in
any way but there's ones that change the
way we thought about the world like
Einstein did it wasn't that sort of
thing and there is a funny story so the
reason they call it the God particles
this book by Leon Letterman and um and
if you read his book he uh he says well
you know we we call it the god particle
but but we should call it the godamn
particle because it's been causing us so
much trouble trying to find it.
>> And Leon ran Firmy Lab. So, and he wrote
a a forward for one of my books. And you
know, I talked to him. He's he was a
really funny guy.
>> And the real truth was the book was
called The God Particle because his
publisher thought it would sell more
copies.
>> But but you know, then that got into the
mindset of the reporters and so forth
and we called it the God Particle. Leon
never really thought of it as anything
to do with a religious or even I mean he
was an incredible jokester. the goddamn
particle.
>> It is a really important part of our
model of the universe. It is that
there's this field that it gives mass to
some particles and not others. That's
>> right. It it's a huge thing but it was
part of the standard model. The standard
model had known forces. It had known
particles. It had all that. The the Higs
Bzon the one thing that is true is it
was the last
unvalidated
piece of the standard model. The
standard model does not answer all
questions which is why we have
unanswered questions in physics. But it
was a punctuation point end of about 50
years of discovery and searching where
we finally were able to say the standard
model while while incomplete, it's
mostly right as far as it goes. Quick
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And now, dear friends, back to my
conversation with Don Lincoln. We did a
whirlwind tour of the history of physics
and took a little tangent on this
incredible discovery of the Higs boson.
Uh, but we didn't go all the way yet.
There's this dream of the grand unified
theory, the gut that uh is a step
towards the toe theory of everything. So
can we talk about the gut first? So what
what's what's entailed in the gut? So
the gut is short for grand unified
theory. We talked about that there were
four known subatomic forces. the um
electromagnetic force, gravity, the
strong force and the weak force and
electroeak symmetry unification merged
the weak force and electromagnetism into
the electroeak force. So what gut hopes
to do is to merge the electroeak force
and the strong force into one grand
unified force. Now that leaves gravity
outside because gravity is seemingly
fundamentally significantly different.
Then subsequently it is hoped that a
higher energy we will be able to blend
the theory of everything together with
all of the known subatomic forces the
strong weak and electromagnetic forces
and then gravity but so as you say gut
is sort of a a way station along the way
that's the goal and uh at this point I
would have to say that I do not see a
fast progress in the immediate future. I
think we're a ways away from that at
this point.
>> You mean on the gravity front?
>> Maybe we'll come up with something
really cool. We certainly had some ideas
back in the early 80s that we tested and
they didn't pan out.
>> Uh speaking of which, string theory is
the thing you're referring to.
>> Uh so string theory posits that
particles are tiny vibrating strings and
by tiny we mean extremely tiny at the
scale of a plank length. Uh then there's
there's other leading candidates like
loop quantum gravity. Uh maybe there's
some alternate theories in the works. So
can you uh linger on that a little bit
more? Do you think a theory of
everything exists? So I hold personally
that there are rules that govern matter
and energy space time and they probably
are rules that I don't know. There are
probably phenomena I'm not aware of. But
I do believe that something there are is
a rule that governs reality. And so in
that sense once we understand the rules
that govern reality, the fundamental
rules that would be a theory of
everything. You know there are things
that are unknowable like for instance
inside black holes we don't know what's
inside there but that doesn't mean that
there's not something inside there. So
there's a distinction between what we
can know and truth. So I I do believe
that there are the rules and I do
believe that with sufficient time,
technology, effort, we will be able to
figure this all out. Now, this isn't a
thing in my lifetime. It's not a thing
in my grandchildren's lifetime or even
their grandchildren's lifetime.
>> Whoa, whoa, whoa. That's a pretty strong
statement, right? That's a pretty strong
statement saying we're
>> we're 50 to 100 years out from finding a
theory of of everything. It took 200
years to go from unifying gravity to
unifying electromagnetism. It took a
hundred years to go from unifying
electromagnetism to unifying the
electroeak force. Now you could say,
well, gee, that's went from 200 to 100.
So it's getting faster, but it's also
getting harder because the unification
scale is of order 10 the 15, which we
can do the math. That's a quadrillion
times higher than the highest energy
accelerator we can build today.
>> And it was one thing to, you know, we
are reaching diminishing returns. We get
something like a factor of seven
increase in particle accelerator energy
every 20 years. And so we have to get to
a quadrillion times. Now, you know, if
you really did believe uh a factor of
seven every 20 years, then that's we're
talking like 500 years, but you know,
this is like Mo's law that it doesn't
continue forever. We're not going to
every seven year. I mean, every 20 years
get another factor of seven. So, yes, I
I think it's a very long time. That's my
prediction. Um, you know, some people
are far more optimistic and we can talk
about that. We should also actually
mention
that I guess your intuition behind that
is not just the part where you come up
with a theory that's beautiful and seems
to be internally consistent, but you
have to have a theory that's making
falsifiable testable predictions.
>> Correct? And you have to have a a
feasible
engineering construction a methodology
for creating an experiment that tests
that prediction. So I think a lot of
your this is 50 100 200 years from now.
Intuition is maybe about the second part
of that which is like you need to have
an experiment. Yeah. Yes. Yes. But you
know let's say I mean you alluded to
super strings. I haven't answered that
question. And I'll table that for a
moment. Super strings is a fascinating
idea. I don't believe it. Um but I love
it. I hope it's true. And there's a
real, you know, apherism and it says you
should absolutely never believe what you
think. So even if you think Superstrings
is true, you shouldn't believe it
because it hasn't been tested.
>> Now let's say super string is correct.
I mean hypothesis it's correct. 100%
correct. I don't know it's correct. So I
don't care. I mean, you know, it could
be correct, but I don't, you know, until
it's validated, it's just a wild ass
guess, you know. So, I we have to have a
way of validating it. So, yes, the the
the empirical side of it is important. I
mean, you could wake up tomorrow and
have the theory that is the perfect
theory, but if I can't prove it, I don't
care. If we were to think, this is going
back to the great courses on the
evidence for modern physics,
>> we're talking about energy levels and
tiny particles
to the degree where the kind of
prediction we would be making is not
accelerator type predictions. So,
it's probably going to be impossible to
build an accelerator that detects
something like a string.
So you have to make predictions
about macrocale behaviors.
>> That's another alternative.
>> It's a different kind of prediction.
>> Sure.
>> Do we even have intuitions about what
kind of predictions they would be? So
one one of course one of the lines of
intuitions has to do with black holes
where in the singularity
the physics of black holes combine
certain elements of general relativity
and quantum mechanics. So there
>> you could see some kind of predictions
you can make.
>> Uh but you can't really mess with a
black hole. It's not like you can create
a black hole in the lab.
>> And the energies that you were talking
about, the sizes we're talking about are
inside a black hole, which you can
intrinsically never see.
>> Yeah.
>> So you know, you can only see the
outside of a black hole, not the inside
of a black hole. So what you said, you
did say something that was incredibly
important and incredibly correct and
probably won't happen, but that's still
good. Okay. So we have two choices when
you talk about super strings. Either
super strings are correct and they're
making predictions up at the plank
energy scale at which point we have to
somehow build facilities that can
generate plank plank energies. That's
possibility one. Possibility too is this
theory which is currently only
applicable at plank energy scales.
Someone figures out a way to take those
equations and solve them in a way that
say predicts the mass of the electron.
>> Mhm.
>> Right. And that is a tricky business.
Um, I am not a string theorist, so I
can't tell you that that's likely, but I
can tell you that they've been working
on it since the 80s, and they haven't
gotten very far. Furthermore, if I uh I
think it's fair to characterize that
string theory is still a a vague idea,
and that's unfair. But let me tell you
why I say that. Because what they have
are approximate solutions to approximate
equations.
And that is already saying that we're a
ways away from really getting a handle
on that. So yes, if there could be some
bright young ladder lass out there,
someone listening to this podcast right
now who figures out a way to take super
string theory and solve them in
tractable ways that makes predictions
from the scale at which they currently
apply down to measurable scale today.
And if that happens, well, then I might
retract my my question or my my concept.
There's a reason why I think that
probably isn't true. That's probably not
valid. So, let let me I I love this. All
right, so let's back up. I'm going to
pitch. I wrote this book for Oxford,
Einstein's Unfinished Dream. And
Einstein's unfinished dream was to come
up with a theory of everything. It was
unfinished because, well, it's
unfinished. And so the the second part
the tagline of that book is practical
progress towards a theory of everything
with the emphasis on practical. Because
when you read books about theories of
everything, when you see podcasts, when
you listen to YouTube videos or
whatever, they are often written by
theorists. And theorists are they're big
idea people. They're very very smart.
But but there's a pragmatism that is
often missing in the sense that they say
well super strings look you know have
these little vibrating things and
wouldn't it be cool and you know but you
got to get to the do you know it. So
let's pretend super string theory or
something like it is correct. The energy
scale at which um that should occur is
of order um 10 to the 15 times higher 10
to the 19 Gev. We can currently do
things at 10 the 4th GEV give or take.
So that is 10 the 15 that's a
quadrillion times higher energy.
So what we are doing now is we are
looking at the world with our very best
measurements and we are trying to
project out a quadrillion times higher
and figure out a theory that explains
everything. Now I I have this I have a
couple of analogies but I like this.
Suppose that you were some, you know,
Joe oustralopythecus 2 million years ago
or something in Africa wandering around
somewhere in Kenya.
>> Mhm.
>> All right. You're about a meter in size.
So you can walk a meter meter scale is
like your scale.
>> Mhm.
>> You can walk 10 meters in every
direction. That's 30 ft. No problem. You
can work 100 meters, 300 feet. You can
work a thousand meters, that's half a
mile. You can work 10,000 meters, that's
60 miles. 100,000 meters is 10 to the
5th. And that that's unlikely. But the
distance that we need to go from what we
can see to the plank scale, it's not 10
to the 5th, it's 10 to the 15th. So that
means in my analogy, think about this
guy who's walking around Africa. Now, if
he walks, you know, 100 ft or something,
it looks a lot like what it is now. He
can make a prediction about what he
sees, and when he goes to that new
place, it's probably going to be okay.
But if he starts walking 500 miles east,
well, he walking around the center of
Africa has no concept of, for instance,
the Indian Ocean, he would never predict
sperm whales or Kraken. He would never
predict what it's like the bottom of the
ocean is going north. He's he's in
Africa. He would never ever have a clue
about the Alps or Antarctica. Going even
smaller distances, going a mile up,
things wouldn't be very different. But
if he goes 10 miles up, he wouldn't
breathe and he'd freeze. If he goes 100
miles up, he would die. If he goes two
miles down, he would roast. The point
being is
we are like that oropycus. We have a
realm that we can study and we can even
predict to some validity what would
happen if we go some distance away. But
the farther away we go, the less and
less our local prediction really
represents the reality of those more
distant times. And so basically his
theory about the the world would be
totally bogus. So even if he had the
best theory, his theory would not have
anticipated the elps. It would not have
anticipated penguins,
>> right? Flamingos not there, you know,
>> and that is just the case. So now that's
what we're doing. We are taking
something and we have reason to
understand what we know and we can
predict a factor of 10 or 100. But I
think it is the absolute
the pinnacle of arrogance to think that
what we can do given the understanding
that we have from what we've measured
now and predict it out a quadrillion
times higher than we can see now. So my
opinion and this is partly because I'm
an experimentalist. The correct way to
make progress, practical progress
towards a theory of everything, is to
look around at the things that we don't
have answers to right now. For instance,
are there something smaller than quarks?
I don't know. Is dark matter real? I
don't know. If it's real, what is it? I
don't know. Is dark energy real? Yes,
probably. But I don't know. What is the
nature of space and time? I don't know.
But these are questions we can explore.
And I would expect, and this is my
prediction, that all right, we're going
to figure things out at a factor of 10
or 100 times better than we can do now.
And we might be able to do that in my
kids' lifetime or something like that.
But in order for us to predict a
quadrillion times higher, I'm pretty
sure super string theory is wrong. Not
because people aren't smart, but because
something new is going to happen. I
mean, if you were talking about
chemistry, you would have never
predicted nuclear physics. And that's a
small increase in energy, right? The
idea that there is something in the
nucleus of atoms that causes the sun to
burn. There's a reason why people didn't
believe, you know, they they calculated
how old the sun should be and it should
only be 10 million years old because
otherwise it would burn out. Well,
that's clearly wrong. And it's wrong
because of nuclear physics. That is why
I feel fairly confident to say while
someone could think well super string
might be right or something and maybe
it's right and I hope it's right. It
would be awesome if it's right but what
are the odds when you making something
with that tiny lever arm predicting it
out a quadrillion away and say oh yeah
we got it right. What are the odds? And
my answer is you got to be kidding me.
Now I could be wrong and I admit that I
could be wrong but that's why I I think
the real issue is not the brilliance of
humanity. It's the stuff we haven't
found. We don't know. I mean the simple
one and I'm say simple and it's not but
what is dark matter.
>> We don't have a bleeping clue. Not a
clue. We know a lot of what it isn't but
we don't know what it is. And so you
know talk about super strings. All
right. Well, maybe dark matter fits in
superstrings. Or maybe dark matter is
governed by a physics that is completely
diametrically opposed to the super
string concept.
>> And allow me a bit of a thought
experiment here. A brief thought. My
intuition says that when you propose a
theory of everything, the kind of
prediction you want to make involves a
kind of leap of conceptual understanding
that Einstein did. So for example, you
want to come up with something like
spacetime and then gravity bends space
time.
>> So it's not merely that you have this
beautiful mathematical framework,
but that framework allows you to rethink
how you see reality enough to make a
prediction that's about the macro world.
I mean to come up with something like
spacetime you know there's one idea for
instance to say that space and time
aren't real they they emerge from from
entropy yeah that's a way of a new way
of thinking and maybe there's some
validity and I want people to think
about it but in the end it's just an
idea and that's the real key thing and
and as you say it has to tie to a macro
world you have to validate if you don't
validate it's a crazy idea theorists are
incredibly creative, smart, wonderfully
interesting people. But I don't care. I
want a measurement that validates the
idea because there are so many I mean if
you read the the journals, there are so
many theoretical papers with all these
nifty ideas that die. you know, uh, one
that was recently I liked and and might
still be true was, um, that dark matter
that, you know, our simple model of dark
matter is that there's a subatomic
particle out there that's heavy and it's
floating around and it's causing
gravity. But someone said, well, you
know, maybe there's complex dark matter,
which means there's a whole dark sector.
So, there are dark atoms and they
interact with one another. And that is a
nifty idea and I love it. And that was
all the rage for a while. and we looked
at it and it may still be true but the
simple ideas have been mostly
invalidated
because we've tested it and it doesn't
work. Same thing there was a talk about
um large extra dimensions. The reason
that gravity is so much weaker than the
other forces was well maybe gravity can
sneak into more dimensions than the
other forces.
>> It leaks into those dimensions.
>> That was a cool idea. I mean but that's
the point is you have these lovely cool
interesting ideas that constantly die.
Mhm.
>> And so,
you know, I I would love for a new nifty
idea to be the idea, but I don't know
how to pick it out of the the hurricane
of wrong ideas.
>> I mean, that's the real beauty of
science. It really is. I mean, the
theories kind of get some of the glory
sometimes, but the real beauty emerges
from the experiment and the
demonstration that the theory is is
correct.
>> And there are two directions. You're
talking a top down. someone comes up
with this big idea that's testable. But
you also have the other way that science
advances and it's not with a theory that
is then tested. It's with the huh that's
weird. For instance, either in in the
1930s with Fritz Wiki or in the 1970s
with Vera Rubin, she did a simple thing.
She said, "How fast are galaxies
rotating?" Cuz it's an easy thing to
calculate. You can literally calculate
that with high school physics and you
get an answer and then you measure it
and it's wrong. And so all that that's
the wow. Huh. I don't know what that is.
And that led to the hypothesis of of
dark matter. Now dark matter is not a
theory of everything, but it's a clue.
It's a powerful clue. We should pull tug
at that thread. Maybe our entire
theoretical edifice unravels. Or maybe
it doesn't. Maybe it's just a snag and
we can fix what we have now. I'm not
sure. So that's another option is to
simply look at many measurements that
are very precise and find ones where the
outcome and the prediction with
established theory disagree and that is
a clue. Before we leave the topic, we
got to talk about string theory. In your
view, is it basically dead? as I
understand uh one of the primary flaws
of string theory outside of the testable
experiments that we were talking about
is uh because it's relies on these
unobserved extra dimensions. There was a
hope that it uh it uniquely could
explain our universe, but it turns out
this quote landscape, there's an
enormous so-called landscape of
possibilities that it'll lead to. And so
it renders the theory basically
unpredictive because you can describe
all kinds of universes and therefore you
can just select
>> uh tune it to describe ours. I I agree
to a degree,
>> but I bring it back to my prior
objection. It is absolutely true that
super string theory um in its current
manifestation
aside from the extra dimensions which
are at some level small potatoes, it
allows for an extremely large number of
possible universes.
What if we were able to take those
predictions and somehow connect it to a
physical measurement? Then what we would
do is we'd lop off those alternatives.
We'd throw them away as saying, well,
you know, those are like an equation,
you know, x + 5. I can put in any number
I want in there. It doesn't matter. But
if x + 5 equals 9, then I've ruled out a
whole bunch of pe numbers except four.
And so this is a case of string theory
does allow for many predictions. But if
we could rule them out by connection to
a measurement, then it would no longer
do it. We would modify string theory and
we would retain the vibrating string
concept, which I really really like. I
mean, I really like it. But until we can
can validate this, it's it's I we can't.
So now you ask is it dead or not? In my
opinion, it is very difficult to kill
such a theory. I mean really truly kill
it cuz kill it means make a prediction
and it fails. But what can happen and
what is happening is people have been
working on it since the 70s. So we're
talking of order 50 years. people have
been working on it and it has not solved
the problem. And so I think what's
happening is people are looking at that
and saying
I do I want to spend my life working in
this direction with a very likely
possibility that 30 years from now we'll
be not much farther along than we are
now. It's a lot like back in the 1940s
when people started thinking about the
meaning of quantum mechanics. And I
wanted to do that when I was a kid in in
the 70s. But then when I went to grad
school, I realized that people very
smart people smarter than me had been
working on that for most of their lives
and made no definitive progress. And so
you have to decide as a scientist who
wants to answer questions. Do I really
want to take on a question that is so
hard that it will not be answered in my
lifetime? And I think that's what's
happening with a lot of super string
theory is people are saying it's really
neat. It might be right, but I don't
want to devote my life to something that
I might not see progress
forward in my lifetime.
>> What do you think about the alternate
theories? Do you think there's anything
interesting in those?
>> You know, many of those theories are
espoused by passionate people. They have
fans,
people love them, but they don't do what
science needs to do, which is make
predictions. Now, loop quantum gravity
is a little different. That one is
better developed. And that one is not a
theory of everything. So, we should be
make that clear. Loop quantum gravity is
not a theory of everything. It is simply
a theory of quantum gravity. Period. It
does not aspire to include all of the
known forces. It simply tries to take
gravity which is currently intrinsically
it treats space as smooth and
continuous. For those of your viewers
who are mathematically inclined in
Einstein's theory of general relativity,
gravity is infinitely divisible. There
is no smallest bit. And so essentially
the laws of calculus apply.
>> Mhm. However, it is possible that at a
small enough scale
um space is no longer divisible in the
same way that you can, you know, take a
cup of water out of a swimming pool and
then a/4 a cup and so forth, but
eventually once you've taken out a
single molecule of water, you can no
longer take out a smaller thing. So,
loop quantum gravity attempts to
quantize gravity. So, that's what it
does. And so this is unlike string
theory which attempts to bring gravity
in with the other forces. And in fact
the reason the fundamental the one
reason why string theory became so um
interesting to the theoretical community
is string theory was not
being developed as a theory of
everything. It was being developed as a
theory of the strong force. And it was
in competition with QCD, which is the
currently accepted theory of the strong
force. And it turned out the the two
groups, the string theory groups and the
um QCD groups competed for a while. And
string theory basically failed the race
and people paid attention to to quantum
chromodnamics, QCD. But then somebody
noticed in string theory that one of the
things it predicted was a zero mass spin
2 particle. And you can prove that any
zero mass spin 2 particle is the
graviton. And so if you see a theory
that has a zero mass spin 2 particle,
you are now have a candidate for
dragging gravity in. And then oh my
gosh, people got terribly excited
because now this theory which was um
working in the direction of the other
quantum forces brought in gravity and
now it was a candidate theory for
everything.
But um but that's not what loop quantum
gravity is. Loop quantum gravity is
simply trying to understand the nature
of space itself which is already a
fantastic thing. And you I talk to Ralli
every so often. I write about his theory
um and I point out some of the issues
with the theory but I'm usually about
like two months behind as he and his
colleagues are developing and so forth
because one of the things is originally
loop quantum gravity predicted that the
speed of light would not be universal.
The speed of light would depend on the
frequency of the light. So high
frequency would travel at one speed and
low frequency would travel at a
different speed. didn't it had to do
with the wavelength of light basically
interacting with the structure of space
if you know and so that was an issue
with loop quantum gravity and so if you
look at gammaray bursters which are you
know super explosions of astronomical
events that are a billion lightyears
away or more and they spit out light in
all wavelengths and if that loop quantum
gravity prediction were correct when you
saw a um one of these gammaray bursters
you would see the wavelength of one
light appearing on Earth at a different
time than another wavelength because of
the different speeds. And that wasn't
the case. They appear at the same time.
And so I went on to say, well, let's
pretty much kill loop quantum gravity
only to get a prickly note from Mr. or
Dr. Ralli saying, you know, we've
disproved that. We've changed the
theory. That's no longer true. And now
that that prediction, that old
prediction of loop quantum gravity is no
longer valid. And so that observation of
the the uniformity of the speed of light
no longer kills the new loot quantity.
It would have killed the old one, but it
didn't kill the new one.
>> By the way, that example of uh different
uh speeds of light uh based on
wavelength, that's a beautiful thing
that a theory that's a testable thing.
>> It is.
>> Right. So like those kinds of things and
if it in fact did explain a phenomena of
that sort that's a good sign for the
theory right
>> if it correctly predicted. There was
another brilliant observation recently.
I love it. Um the observation of uh
gravity waves.
>> Mhm.
>> And it was from two neutron stars
orbiting and coalescing. And so they
made gravitational waves. Fantastic. But
they also because they were not black
holes, they were neutron stars. They hit
and exploded. Gave off a tremendous
bright flash of light. And so
astronomers saw the flash.
>> Mhm.
>> Gravitational wave astronomers saw the
ripples of spaceime. It was 140 million
lighty years away, which means light
would have traveled 140 million years to
get here. And the two incidents, light
and gravity, both arrived within 1.7
seconds of one another. And that tells
you that gravity travels at the speed of
light. That was a brilliant, fantastic
measurement. Now we thought gravity
traveled at the speed of light, but now
we have a measurement. We proved it and
damn it, I am impressed. Our universe is
so fascinating. Speaking of which, since
we brought up antimatter,
we have to talk about it. Uh you've
talked about in several of your lectures
from different angles, including uh the
dark energy crisis and including uh
empty space and vacuum and so on. So
let's look at the empty space angle. So
uh you know it turns out the empty space
is not empty.
>> It's true which is kind of bizarre.
>> Can you can you speak about what do we
know about what makes up empty space?
>> That's a hard hard question because we
don't know what space is. But let's
start out
>> let's just start out with something
simple. We'll assume that space is not
quantized. Okay. Now it probably is. I
don't know. But you know, we got to
start with somewhere. So, let's start
out with sort of the space of calculus,
the space that you can divide forever.
The modern version of quantum mechanics
is called quantum field theory. And it
postulates that a space exists. Then it
postulates that within space there exist
fields for every known subatomic
particle. So there is a photon field,
there's an electron field, there's an up
quark field, there's a down quark field,
there's a all the fields
and those fields can vibrate and when
they vibrate those are the subatomic
particles. So an electron field
vibrating in a characteristic way is an
electron. Now, it's also possible for
the electron field to vibrate not in the
characteristic way, but in a way that's
still vibrating, but it's not an exact
electron. So, this is what we call
virtual particles. Now, virtual
particles, there are lots of ways to
talk about them, and the way I'm talking
about now is the most correct and the
most sophisticated way that we can talk
about them. I will talk about them
briefly in a in a simpler way to help
but right now that's the important thing
is that there are these fields specific
vibrations are the known particles
vibrations that are a little different
are
are these virtual particles they're
particles that don't truly exist and so
that is what
we think space is. There is all of these
these these fields. They are all
vibrating a little. If you insert the
right amount of energy, you can get it
to vibrate in the characteristic way and
make that subatomic particle. But even
when you don't there is um the particles
I mean the fields are there and they are
vibrating. So those vibrating vibrations
are what we called virtual particles.
Now your viewers may have heard of
virtual particles in other ways in which
case it says that space is just empty
and what happens is matter and
antimatter particles briefly appear for
a very short period of time before they
coalesce back again and disappear and
and reemerge back into the field. And so
that these are both correct. So what
happens is is that's what quantum field
theory says is it says that these
ripples are hearing or these particles
are appearing and disappearing. And so
that just sounds nuts. You look at empty
space, you're not seeing anything
happening, but they're happening fast
enough that they can't be seen. But they
do have consequences. And there are two
experimental measurements that I can
think of that validate that this thing
that sounds crazy is really happening.
And one is called the casemir effect. So
in the casemir effect you take two metal
plates that parallel plates and you put
them near one another very very close.
Now if this is the case if if these
virtual particles exist then in between
the plates these particles appearing and
disappearing and outside the plates the
particles are disappear appearing and
disappearing. However, because these
plates are close to one another, this
puts a constraint on the wavelength of
the particles that can occur between the
two plates because they the particles
cannot extend outside the plates. So the
short wavelength particles can exist
inside the between the plates, but the
longer ones cannot. However, outside the
plates there is no constraint. So short
wavelength and long wavelength particles
can exist there. And the net effect is
there are more particle virtual
particles outside and less particles
inside. And therefore you have a net
pressure which would then push those two
plates together. That is a prediction
we've been talking about. And guess
what? It happens. Those plates push
together. So that is a validation for
the existence of these particles in
empty space. Now there is another
measurement and this changes the
magnetic properties of particles like
the electron the muon and and so forth
and so this was uh discovered in 1948.
So if you take old school standard
quantum mechanics um you know the spin
of an electron you know its charge you
can calculate its magnetic moment and it
comes out to a number. If you do the
measurement, what you find is the
measurement disagrees with the quantum
mechanics, the 1930s quantum mechanical
prediction by 0.1%. And that was
measured in 1948.
And people went, huh? So this happened
at the Shelter Island conference in New
York. And on the way home, someone who
saw the this measurement thought about
it and they invented what we now call
quantum electronamics. So old quantum
mechanics quantizes matter. The second
quantization quantizes both matter and
the fields. In this case, quantized the
electric fields. And so in this
quantized um field, it predicts that
surrounding a bare say electron which is
spinning and has a has a charge, there
is this this bath of particles, virtual
particles appearing and disappearing all
around it. And the ensemble of all of
those particles appearing and
disappearing will alter the magnetic
properties that you can measure for the
subatomic particle. and it changes it by
0.1%. And we have measured this and we
have not measured this imprecisely. We
have measured the magnetic properties of
both the electron and the muon to 12
count them 12 significant figures. And
the theory and the data agree number for
number for 10 places. And then once you
get out to the very end where both the
theory and the data have some
imprecision, they then disagree. And so
maybe there's some interesting stuff
going on there. But 10 figures, it's
just staggering. So virtual particles
refer to
matter and antimatter particles coming
to life.
>> Correct.
>> Can we just talk about the the
antimatter part of that? So it's
starting with Paul Durac, one of the
most legendary examples of math leading
to physics. So the math suggesting that
so something like an antimatter should
exist and Paul Direct taking it
seriously and then eventually showing
that it does exist. So what evidence do
we have for antimatter? So antimatter
was predicted in 1928. Paul Durac was
trying to merge quantum mechanics and
relativity because the original
Schroinger equation did not was not
relativistic and in doing so he
basically the equations were complex but
in the end it came down to something
like equation squar= 1. You take the
square root of both sides you get
equation equals +1 or minus1. + one was
the electron minus one was something you
didn't know what it was. Um there was
some conversation for a while thought
maybe it might be the proton but that
didn't seem to work out and so he
insisted that his equations were right
and that there was an antimatter he
didn't call it an antimatter but a
positively charged uh sibling of the
electron what we now call the posetron
the antimatter electron so it was
predicted it was discovered in 1932 by
Carl Anderson and his student Seth
Nettoer they saw saw an antimatter
electron
and that was pretty cool. So that right
there they knew it was real. Antimatter
was predicted. It was observed. That's
that. In 1956 the antimatter proton was
created and that required a large
particle accelerator high enough energy
um to to to make it and that was done at
Berkeley and a year later the antimatter
neutron was discovered. So at this point
and now jumping ahead to now we can make
using uh energy by smashing particles
together we can make antimatter protons.
We can make antimatter electrons. We
have gone so far to make anti-atter
helium nuclei. So we have made two anti-
protons and two anti- neutrons. Combine
them together to make an anti-atter
helium nuclei. This has been done, been
observed. No question. At CERN, they
have gone so far as to make antimatter
hydrogen. They take a beam off one of
their lower energy accelerators. They
make antimatter protons. They collect
them. They slow them down. They cool
them to almost absolute zero. They take
um sodium 22, which makes antimatter
electrons. They slow them down. They
bring them together. They coalesce them
and they make literal antimatter
hydrogen atoms with an antimatter proton
surrounded by an antimatter electron and
they have done incredible measurements.
They have agitated the atoms and caused
it to emit light. They have looked at
the light that comes out of antimatter
atoms. And the question is is does the
light coming out of antimatter hydrogen
atoms have exactly the same spectral
characteristics as ordinary hydrogen
which we predict that it does
and the answer is it does. So the tests
have been staggering. We now know a
great deal about antimatter hydrogen.
recently recently like 2023 I believe it
was one of the experiments called alpha
at CERN made antimatter hydrogen put it
in a bottle and released it and watched
which way it would go did it fall up or
did it fall down because um while it
kind of makes sense maybe to think that
maybe antimatter falls up in the same
way that we have Kulum's law you've got
electric charges and they might attract
or repel Well, um, however, there was
lots of ample theoretical reasons to
believe that antimatter also would fall
down. So they did this fantastic
measurement and they first they put in
hydrogen and they calculated that some
if they did this something like 80% of
the hydrogen atoms would fall through
the bottom of the bottle and 20% would
go through the top just because um
gravity is very weak and the atoms will
escape wherever they do but there will
be a bias pulling hydrogen atoms down.
So they did the exactly the same thing
and what did they find? They find that
antimatter falls down. Now they do not
have a good enough measurement at this
time to say that the gravity that
antimatter experiences is 100% that of
matter. What they have measured is that
antimatter fell down with 75%
the strength of regular matter. But
there were big uncertainties. There was
plus or minus.13
due to the experiment which was good but
imperfect and plus or minus.16 due to
their um their theoretical model. So
it's like 75 plus or minus something
like 29 and that means there's a good
chance it's between.5 and one which
means it's consistent with one. So they
are improving their measurements. Well,
if I can, I would love to take a bit of
a tangent on that topic because I went
down a rabbit hole watching some of your
v videos on antimatter and I mean Firmmy
Lab was the hub for the production of
antimatter for quite a while.
>> It was
>> I saw that NASA said that the global
estimate for the current rate of
production of antimatter is 1 nanog per
year. Can you speak to how hard was it
to make antimatter? And also you did
mention in a video that you know if
matter and antimatter meet they produce
a lot of energy.
>> I think 20 grams of antimatter is
equivalent to a 1 megaton nuclear
warhead in terms of explosive energy.
Yeah. So all those questions together.
So how hard is it to produce antimatter?
>> It's freaking hard. Okay. All right. So
here's the deal. So at the time until
2011, Firmay Lab was the most powerful
anti-roton production facility on the
planet. Every 2.3 seconds, we would
smash 10^ the 13 protons into a target
and we would get out 10 to the 8th
anti-roton. So basically in order to get
a single anti-roton we needed to smash
100,000 protons into material. So every
2.3 seconds we would get of order 10 to
the 8th antiprotons. And what we would
do is we would collect them over the
course of 12 hours or so. And we would
get in the end we would have to collect
them and cool them down and so forth of
order 10 the 12th antirotons every 12 to
24 hours. So 10 the 12th sounds like a
lot. It really does. That is a trillion.
But you need to remember that a gram of
antimatter is 10^ the 23 antirotons. So
that means over the course of a day we
were able to create something like 100
billionth of a gram.
And so if we did that for a year then
that would be about a nanogram. So about
a nanogram a year give or take. That's
that's a reasonable estimate. So a nanog
one billionth of a gram. So that means
at that rate with that facility it would
take a billion years running with very
little downtime to make a single gram of
antimatter. If you combine 1 g of
antimatter and 1 g of matter together,
the energy release is equivalent to the
combined Hiroshima and Nagasaki
explosions. So that tells you if you
wanted a megat ton, you need about 25
times more. So you would have to run for
25 billion years to get a megat ton of
explosive power.
>> Let me uh lay it all out because I think
it's pretty interesting actually. This
is a NASA estimate of how much it cost
to produce antimatter. So looking at all
the the cost of the accelerator, all
everything combined together to do
enough for a one megaton antimatter bomb
of such a thing would be even possible
on the order of 25 grams like we
mentioned will cost about based on the
NASA estimate
>> uh 1.5 quadrillion.
By the way, uh NASA wasn't talking about
Obama. It's just me adding NASA was
talking about the estimate the cost of
62 to63 trillion per gram of
anti-hydrogen
actually is what they're referring to.
Uh so compared I was looking at
estimates the current best estimates how
much it takes to produce a 1 megaton
nuclear warhead
everything combined is about 10 to 50
million in the United States. So you're
talking about difference in terms of a
weapon with equal power $50 million
versus $1.5 quadrillion.
To me what's interesting weapons is just
one uh indication of this. One other
possibility and NASA also writes about
this is the use of antimatter and
propulsion systems.
>> Right?
>> Uh just like you can use uh nuclear
fision and maybe even nuclear fusion
down the line in propulsion systems. I
saw that one gram can help get us to
Alpha Centauri star system. If we can
get to 02 times the speed of light in 20
years. Uh meaning it would take us 20
years to get to Alpha Centauri. Is any
of this a possible future? The use of
antimatter for generation of energy
because we should mention that it's
extremely compact. It has the obvious
downsides that it's extremely costly to
produce. who don't know how to do that
kind of scale.
>> The upside is it's compact. It's
>> very powerful.
>> So the short answer is it is not a
physics problem. It's an engineering
problem. So I have people for that.
Okay. Um okay. But no no um the truth is
that antimatter
if you are able to uh assemble it and
store it. Sure. It would be able to take
that antimatter, heat up matter and
shoot it out the back of a rocket and it
would, you know, do what rockets do and
it would make us go quick and that would
be fine.
>> And we should mention the thing that you
just mentioned is is correct. One of the
hugest challenges is the containment.
>> Oh, because antimatter when it comes in
contact with matter
>> uh is a is a problem,
>> right? So if you were unable to uh to
contain your trip to Alpha Centuri for
even a millionth of a second, boom. And
that would not be good.
>> Yeah.
>> Um you know, it reminds me of the uh the
Star Trek where Scotty's saying,
"Captain, you know, the antimatter pods
are about look, we're losing containment
going to blow." And that's exactly what
would happen.
So the short answer is yes. antimatter
as in principle we could make and use as
a a source of energy, but there are
probably far less expensive sources of
energy. Um,
you know, it depends on what you need to
do. The Voyager probes are still
chugging along with plutonium now.
They're running out of energy at this
point, but we could, you know,
presumably do a somewhat better job if
we needed to. So, I I like the idea of
antimatter, you know, but the reality is
the danger, not the obvious danger of
weapons, but the danger of if you wanted
to be in a ship run by antimatter, if it
ever got loose, well, you you would
never know it. That would be that.
>> The reason I I find this kind of
inspiring
is antimatter in this space of physics
that has a lot of mysteries. There's a
lot of exploration to be done. And so
this kind of connection to energy means
that
uh if we have a bunch of breakthroughs
on the antimatter side that might lead
to a better propulsion system, better
energy generation systems
>> in principle.
>> There's some combination of engineering
here, but there's some combination of
understanding the fundamental physics.
>> I mean, we know how to do this.
You know, we we know you take energy,
you make antimatter. You have to contain
it, you have to store it, you have to do
all the hard things. But I I would be
shocked if there was some like new
addition to the theory that made
antimatter production easier.
>> Interesting. So, we know how to produce
antimatter with accelerators. You're
saying there's not
breakthroughs in physics that could lead
to different mechanisms for the
generation of antimatter.
>> You have to concentrate energy. That's
it. If there's another way to
concentrate energy, that would work too.
>> And our best knowledge of how to
concentrate energy is the accelerator.
>> And remember, we're talking
concentrating it into um volumes the
size of a proton. I mean, if you
concentrated to the size of your thumb,
well then, you know, it's really the
density that matters, the local density.
And so, when you smash two protons
together, all of that's occurring in a
tiny tiny volume. So, it's the local
density of energy that matters. If you
had a lot of energy in a thimble or
something,
>> it's probably not dense enough. You
know, it really has to be in close
proximity for that to happen. And then
when it does it, it's it's okay. So So
if there's another way, we know how to
do it to to make that that density thing
with with accelerators. If someone has a
bright idea on how to make highly dense
energy then yeah uh making antimatter is
a piece of cake but that's the crux
concentrated energy.
>> Yeah. How to do so in a cost efficient
manner not trillions of dollars.
>> Well yeah.
>> So one of the big mysteries with
antimatter is the bigger why.
Where is the antimatter that should kind
of be there? If the whole idea is that
anytime you generate matter, you
generate the same amount of antimatter.
And yet when we look out into the
observable universe, it seems like
there's not antimatter for the most part
there.
>> So what do we understand about this
mystery? What are the possible
explanations as to why? So there's this
thing called um
biogenesis and and as you say so
reiterating a little bit what you just
said um these are both Einstein things.
Einstein says that when you take energy
you make matter and antimatter in equal
quantities and Einstein says after the
big bang there was a lot of energy in
the universe which should have made
matter and antimatter. We only see
matter. Where' the antimatter go? And
the answer is we don't know.
However, there are some ideas and
there's a lot of thinking on it and um
in fact for me it's doing an experiment
right now with nutrinos trying to to
better understand what it was that made
the matter and antimatter not be the
same. Now, we do have a measurement of
how much different it should be. And
it's kind of neat. We can do this by
counting the number of protons in the
universe just looking at galaxies and so
forth. And then we can look at the
cosmic microwave background which is
sort of the aftermath of the big bang.
And we can count the number of photons
from the cosmic microwave background.
And with a little bit of math, what we
can do is we can then say that somehow
in the early universe, something made a
very very tiny asymmetry.
So that for every billion billion with a
B antimatter particles that existed in
the universe, there were a billion and
one matter particles. Mhm.
>> The billions canled, annihilated,
destroyed each other, and that extra one
that's left over is us.
>> Mhm.
>> And so what physics mechanism made that
ever so slight
asymmetry is not understood. There are
some thoughts. One thought is uh that
well, it's just how it was when the
universe was formed. There was an
asymmetry. it was not made by matter and
antimatter.
Another possibility is um there are
various numbers of theories all under
the word beriogenesis and berio um
coming from word beron which basically
means protons and genesis meaning the
creation of and we'd say that simply
because the protons are the heaviest
particles and so biogenesis is just the
creation of matter and there are just a
number of theories in quantum mechanics
that say that matter and antimatter can
can oscillate back and forth into one
another. And there is a slate slate
asymmetry in how that happens. And we
know that this is true to a degree. Um
we've measured it in the 1960s with a a
different form of matter. I mean, you
know, not protons, but a a a type of
ephemeral matter that only exists in
particle accelerators. And so we know
that there is a slight difference
between matter and antimatter, but it's
not enough. If it doesn't explain that,
we're not sure. So, at Firmeny Lab, we
have this idea which kind of turns
things on its head and it it's not
beriogenesis, it's leptogenesis. So,
lepttons are the electrons.
And because Fermy Lab is currently the
world's most powerful nutrino
accelerator and nutrinos are leptons,
there is this idea. Now leptogenesis is
incredibly complicated but the idea is
that it is possible. We we know that
nutrinos actually change their identity.
There are three different types of
nutrinos like uh I don't know cats and
jaguars and tigers. And if you have a
beam of just cats if you go along a
little while you find there's cats and
jaguars and then tigers and then they'll
be back to all cats again. And so this
oscillation thing is called nutrino
oscillation. We've known it's been true
since 1998.
And what we are studying is we're going
to make a beam of nutrinos and another
beam of antimatter nutrinos. And we're
going to study the oscillation behavior
of the two of them. And it is possible,
it is unlikely, but it is possible that
the two of them will oscillate at
slightly different rates.
>> Mhm. And if the nutrinos oscillate at
slightly different rates, then that
along with several other highly
improbable things can tie together and
might explain why there is more matter
in the universe. So if I was going to
bet the farm, I'll bet that they
oscillate at the same rate. But I don't
know, and you don't know till you do the
measurement. So that's what we're doing.
There are some other uh experiments
trying to measure it right now. So
there's a big race between the Firmeny
Lab group and another group in Japan to
see who gets there first and make this
measurement and we will find out. If it
turns out though that there is a
difference in this oscillation rate
between matter and antimatter, it will
be a huge clue in this very very
difficult puzzle. I wish I could tell
you I knew what the answer is, but but
literally nobody knows. I mean, and
that's the thing of being a research
scientist like me is if you're not
confused,
you're not doing your job.
>> So, there is this desperate or not
desperate, exciting search for this tiny
asymmetry.
>> Yes.
>> It's so so crazy to think that
everything we see around us
is a result of this tiny asymmetry that
there was this gigantic annihilation of
matter and antimatter in the early
universe.
>> And this is just some little
accident.
>> Yeah. Yeah. That's crazy.
>> It's a happy accident.
>> That is just I mean it's totally crazy.
>> This is one of the areas of physics
where there's a lot of mystery.
>> Mhm.
>> Okay. So, uh can we pull at that thread
a little further? Let's talk about our
intuition of what is uh dark energy as
it connects to empty space and
everything we've been talking about. Uh
what's what's the cleanest definition of
dark energy? So dark energy is either
energy of space or energy in space. The
most common statement is the energy of
space.
And it is essentially a repulsive form
of gravity.
And we believe this is real. And the
reason we believe this is real is from
observation. And this is one of those
things where we talked about a while ago
where I said that, you know, you can
think about things up this theoretical
stuff and try to come up with a
measurement or you can make measurements
and see where they disagree with
predictions and lead that in a
direction. So back in the late 1990s,
some astronomers were looking at the
expansion rate of the universe. So the
the big bang occurred, the universe is
expanding. The universe is full of
matter. Matter attracts. So the gravity
due to the matter of the universe should
slow the expansion of the universe. And
the only question was how much? There
were three possibilities. The
possibilities were there was so much
gravitational force that the expansion
of the universe would slow and be pulled
back together in a big crunch. Number
two was that the universe would continue
expanding, slowing down, but never
really stopping. And then the third
possibility was the exact critical case
where expansion would slow forever and
approach zero only at infinity never
quite stopping or reversing. So those
were the possibilities. Door number one,
two or three. So they did the
measurement and what did they found? It
was door number four. The universe was
not only expanding but the expansion was
speeding up. And the only way that could
happen given that gravity slows it down
is there was a repulsive force. And the
name we give to that repulsive force is
dark energy. This is something that
Einstein postulated early on in his um
his development of of general
relativity. But then because at the time
he knew that his theory predicted that
the universe would collapse. Um but he
believed the universe was eternal and
not unchanging. And so he needed
something to counterbalance the uh that
uh collapse. And so he invented dark
energy. He didn't call it that. Call it
the cosmological constant. Um but then a
few years later, Edwin Hubble discovered
that the universe was indeed expanding.
And so since the universe was no longer
static, Einstein said no need for
cosmological constant, took it back out.
>> Thought it was a dumb idea that he put
it in and was embarrassed. Um, however,
in 1998, it became clear that his
original idea that there should be some
sort of repulsive form of gravity was
real and it's put back in the theory.
>> And so that's what it is. We are pretty
confident at this point that the
expansion of the universe is speeding up
and the thing driving it is dark energy.
Now, what is dark energy? I don't know.
Um, as I said, the most common thought
is that it is the energy of space
itself.
But it is at least conceivable that
there is a field in space where space
exists
>> and that field is pushing space apart.
That's another conceivability that I'm
not sure that we have the the
instrumentation to distinguish, but
that's not what normally people think.
People think it is literally a property
of space.
>> But but there is the
what you call the worst prediction in
physics which is a
>> oh yeah that's another one
>> a nice little insight about the
complicated nature of dark energy. So
the observations
as you described say that empty space
has a tiny energy density that
accelerates expansion of the universe.
But
quantum field theory's prediction for
what vacuum energy should be when
coupled with gravity is much larger.
>> Mhm.
>> Uh so this is what makes for the uh
quote you have a video on this worst
prediction in physics.
>> Can you can you explain this crisis?
>> Well the there's a measurement and you
can measure how fast the universe is
expanding and from that you get a
measurement of dark energy. However, if
you then say, well, suppose the dark
energy is due to fields in space. So
that's quantum field theory. Hey, I know
a lot about quantum field theory.
>> And so we can take the quantum field
theory and we can calculate what the
density of energy is due to quantum
field theory. And basically what you do
is you take within a volume the uh all
of the wavelengths, the the longer
wavelength, the shorter wavelengths, the
shorter shorter and shorter. And you can
add them all up.
And each wavelength adds a certain
amount of energy. And if you add that
all up, then you get a number. And that
number is the rather embarrassing
10 to the 120 power times that's a one
with 120 zeros after it bigger than the
measurement of dark energy.
>> Yeah.
>> So you go yuck that is not fun at all.
And that is because the equation comes
to the highest energy or the smallest
wavelength particle that you can imagine
to the fourth power since anything to
the fourth power is a big deal. So
that's where you get that awful number.
Now if it turns out that there is some
new physics that's just about at the
energy scale we can measure using our
biggest particle accelerators. Remember
I told you that that was a factor the
maximum energy scale plank scale is 10
the 15 times bigger than what we can
measure now. So let's say that we don't
have to calculate up to the plank scale
because something happens something
changes at the energy that we know right
now. Well then that means we don't have
to integrate to plank scale. We
integrate to 10 the 15th less of the
plank scale. And this thing is to the
4th power. So 10^ the 15 to the 4th
power is 60. So now
even if we say you know Don he's
brilliant he's going to find something
at the LHC tomorrow is going to solve
all this problem. Now we've solved it.
It's much better. It's only different by
10 to the 60 power which is still pretty
bleeding big. So the short answer is
there is very clearly something going
on, something wrong, very badly wrong in
the quantum field theory. You know, we
have to have maybe there's another field
that balances out the energy that
cancels it down. And even that, you
know, that that's not so so outrageous.
You know, you could imagine that there's
another, you know, like we have matter
and antimatter. They balance pretty
well. Okay, maybe there's something
going on. And you could cancel that out.
That'd be perfect. But cancelelling
something to zero is easy cuz you know
plus one and minus one 0 + 2 - 2 0. But
we still have dark energy. Dark energy
is a little bit. So if it cancels, it
doesn't cancel exactly because it left
over that little bit of dark energy. So
that is its own curiosity. Perfect
cancellation pretty easy. Theorists do
that, you know, eight times before
breakfast. imperfect cancellation much
harder.
>> Just to elaborate that a little bit,
what do you think solving in quotes
solving dark energy would look like?
>> Well, you could what you would do is you
would hypothesize that there existed
some other field that had the the the
reverse uh effect of existing quantum
fields,
>> but not to zero.
>> But not to zero. So, but if you had it
to go to zero, you know, uh, sure, maybe
there's a field that that exists at
really high energies that we haven't
seen yet. I don't know, but it cancel
things out and we're cool.
>> How would we then demonstrate the
existence of that field?
>> Uh, well, that would depend on the
prediction.
>> How do you even come up with a new field
>> like all theorists do? Well, let's add
something to my equation and see what
happens. I mean, and and that's okay. I
mean, I I'm being glib about that, but
that is precisely what you do. You say
what change? We we have this thing that
works quite beautifully except it fails
here. What is the addition that we need
to make that changes very little in the
realm that we measured and yet fixes
this hard thing? And so you literally
just go da da da. Okay, what do I need
plus six or something and as long as it
makes no changes where it would hurt our
measurements and fixes the big thing,
then that is at least a candidate
theory. Now, that doesn't mean it's
right, but it at least gives you an
understanding
of what the right answer should look
like. M
>> and so that's the first step is what
should the real answer look like or what
is a possible real answer and then once
you kind of know that then other people
can look and say well let me think about
a theory that kind of has the required
properties
to do what we need it to do. So, it's
it's a multi-step process, but the first
step is how do we tame this problem
without coming up with really terrible
predictions that we've already ruled
out.
>> And and so that's what you do. And and
you know that that is literally a a
sensible, viable theoretical thing, you
know, cuz you have to explore cool
ideas. I mean one of the reasons dark
energy is super interesting is it kind
of gives us a mechanism by which we can
talk about the deep future of the
universe. I it's making we have
observations about the expansion of the
universe
but it's also giving us the mechanism of
that right so we can talk about
uh any weirdness any good model we have
that that captures some of the weirdness
of dark energy
>> might give us insights about how this
thing ends how the universe
>> about the deep future of the universe
right
>> absolutely as it stands right now if
dark energy is real and who knows you
know if it's a real exact exactly as
we've measured it. Then as the um
universe gets uh bigger and bigger, dark
energy becomes a bigger and bigger
component of the energy balance of the
universe and it takes over and it drives
the continued accelerated expansion of
the universe.
>> And if dark energy gets lower, you know,
for some reason that we don't
understand, maybe it changes over time,
gets smaller, that could change things.
If it gets bigger, it could change
things. That is one of the big open
questions whether it's constant over
time or not.
>> Right? And there has been a recent
measurement that suggests that dark
energy is getting smaller. Um however
that is a new measurement not confirmed
blah blah blah blah blah. Nobody should
believe it but it's a hint that maybe
it's changing which is kind of cool in
itself because the current bias until
recently is that dark energy is
constant. Now I want to be super careful
because it's misleading. People say dark
energy is constant. Dark energy is a
density.
>> Mhm.
>> Now that think about that. You have a
certain density. Let's start with that.
>> Then the universe expands. So energy is
volume times density. If the universe
gets bigger and the density is constant,
that means dark energy
>> is increasing. It's not just increasing
as a fraction and overwhelming ordinary
matter. But ordinary matter as the
universe expands its density decreases
because it's constant and the volume
gets bigger, the density drops. Dark
energy until recently is thought to be
constant density.
>> So that's what's implied when you say
constant. You say constant density which
means it's actually increasing because
space is increasing. The size of space
is increasing. Interesting. And so
that's a a weirdness. And that then ties
into the nature of space. Why does that
tie into the nature of space? Well,
because if dark energy is a field in
space, if you increase the volume, you
would think the energy density would
drop.
>> Mhm.
>> But if space is increasing and space is
quantized, and I don't know if it is,
then maybe what's happening is space
isn't stretching, but like little space
particles are appearing as the space You
know, there's like bubbles of space
appearing and each bubble contains a
certain amount of dark energy. And so
therefore, that would give you a sense
that dark energy is a property of space
rather than a field in space. But that's
all very handwavy, guessworky stuff. So
if you had bet all your money, is dark
energy like a real physical what does
that even mean thing that exists versus
is this just an a renaming of the
cosmological constant?
>> Unfortunately, I think it's both. I
mean,
>> well, I mean, it is it's describing a
reality, but it's also maybe telling us
something about space,
>> literally a property of space. Yeah,
it's I mean that's kind of what it looks
like given that it seems to be constant
density. That seems to me now this is
not something anybody should believe.
Please, nobody believe this. But it
seems to me that this is leaning towards
the idea that A it's a property of
space, B, space is quantized. C as space
is expanding little quantum of space are
appearing and D each one of those quanta
has a certain amount of energy
associated with it and that would kind
of explain the constant density. Now,
please, that's not anybody should,
nobody accepts that. This is just
nonsense.
>> But a lot of the stuff that you just
said is experimentally
probably experimentally testable. You
can probably construct them
>> experiment the bubbles of
>> Well, finding out the bubbles of space,
but those quanta conceivably are
planksiz bubbles.
>> Yeah, the quanta.
>> Well, they'd be quantum of space. I mean
the idea is you know you look at a sand
dune and it looks smooth and continuous
but you can see individual grains of
sand right and so what this is saying is
as this dune expands new grains of sand
are appearing and each one of them is a
quantum of space.
>> So what kind of experiments can we do in
the coming decades or centuries to
understand dark energy better? I mean
people have been talking about quantum
entanglement of gravity.
In standard quantum mechanics a particle
can be in two places at the same time.
All right? So now you have two
particles. So this particle can be in
two places in the same time. This
particle be be two places at the same
time. If you put them near one another,
well if they're close to each other,
there's a certain gravitational force.
If they're far apart, they're certain.
And if they one is close and one is far,
you have another one. You can calculate
the effects of gravity having to do with
quantum entangled particles being in two
places. And people are talking about
doing this and trying to see if in doing
such a measurement they might be able to
definitively determine whether gravity
is a quantum phenomena
or a continuous phenomena. And that is
potentially a measurement that could be
done
soonish because the technologies of
inherent in all of this recent work on
quantum mechanics is allowing people to
be able to make
instrumentation that might be precise
enough to do this measurement. Now this
will not tell us what quantum gravity
is. It will not tell us anything. But it
will tell us that gravity is quantized.
And just knowing that, well, for one
thing, it shuts out a whole realm of of
continuous gravity. And the theoretical
community will then turn its attention,
forget this stuff, and and think over
here. Now, that doesn't tell you that
space is quantized, but it tells you
that gravity is quantized if it bears
out. So, and if gravity is quantized,
then people will start thinking more
about space being quantized.
>> I have to ask because you mentioned dark
matter is perhaps even more mysterious
than dark energy.
>> Okay.
>> Can you can you can you uh build up the
intuition why it's more mysterious. What
is dark matter?
>> Oh gosh. What is dark matter? A, I don't
know. B, it's terribly fascinating.
>> Yeah.
>> All right. So, first thing and the most
important thing cuz I'm an
experimentalist by God. The first thing
is why do we believe there's dark
matter? And the reason is that
astronomical measurements do not agree
with predictions by Newtonian or
relativity theory. Galaxies spin too
fast. Clusters of galaxies move too
quickly. And the distortion of very
distant galaxies due to the
gravitational field of near galaxies
disagrees with the prediction from what
we see from the observed matter. So
there are three very distinct reasons
why we are predicting that that
something is wrong in our understanding
of either the laws of physics or the
matter budget of the universe. The
easiest one to talk about is the
spinning galaxies. Now this is what I'm
saying is not unique to spinning
galaxies just easiest to talk about. So,
galaxies are observed to spin more
quickly than they should if we add up
the gravity we see. By all rights,
galaxies spinning that fast should blow
themselves apart and they don't. So,
what can be the answer? Well, you have
the force required for a star to orbit
to move in a circle and you have the
force due to gravity and they're
connected by an equal sign and the
prediction is wrong. So either the force
due to gravity is wrong, the force
needed to move in a circle is wrong or
the equal sign is wrong. I mean this is
really simple. One of those things is
wrong.
So one possibility is simply that
Newton's law of gravity mass time the
mass over r 2 time a constant that's
just wrong. Another possibility is
Newton's F= ma that we are taught in
introductory physics is wrong. Both of
those are eminently possible over here.
Maybe we don't understand gravity
or maybe there's more mass than we can
see. So these, you know, I mean, it's
nice that that you can look at this
really simply and come up with a list,
you know, cookbook things we can test.
And um and so we've done that. We've
gone and said, what are the
possibilities? Well, the most obvious
possibility is that there is more mass
than we can see. there's black holes,
there's uh um hydrogen gas that we can't
see, whatever. There's something out
there. So, that was the first thing. So,
you go and you look and there's no
hydrogen gas because we can see that
with radio waves. That's not it. Um in
the '9s, we went looking for black
holes, rogue planets, things like that.
Those exist, but not enough of them.
That's not it. And so now we're left
with there's some sort of matter that we
can't see or we don't understand gravity
or we don't understand inertia.
Now I personally if you asked me this oh
I don't know 25 years ago I would have
said the most likely uh answer is that
we don't understand inertia or gravity.
You know I if 20 years ago 25 years ago
that's what I would have said. No
problem. However, there have been a
couple of observations
that um
that have caused me to change my
thinking and I think that dark matter is
more likely. One of them is called the
bullet cluster. So, the bullet cluster
there are two large clusters of
galaxies.
In these large clusters of galaxies,
well, any galaxy consists of a couple of
components. There are the galaxies
themselves. There is the hydrogen gas
that surrounds the galaxies. And maybe
there is dark matter.
And if dark matter is real or dark
matter is not real, you will get
different answers if those two galaxies
pass through one another. The galaxies
themselves should pass through one
another basically not interacting. But
the big thing is the gas clouds. So if
there's big clouds of gas, as the
galaxies pass through one another, the
clouds should interact and the gas cloud
should stop in the middle and be really
really hot. So then you would see if
there were no dark matter, you would see
a cluster of galaxies, a cluster of
galaxies, a big gas cloud in the middle.
And because the big gas cloud in the
middle is much more massive than the
galaxies themselves, you would expect to
see distortions that we call dark matter
distortions in the middle. If however,
dark matter is real, the galaxies pass
through one another. The cloud stops.
dark matter doesn't interact with the
clouds so it passes through. In that
case, you would expect to see the
distortions where the galaxies are
>> and that's what we see. So that is a
strong evidence in my mind. The bullet
cluster is strong evidence that dark
matter is a real thing. And there is
another example which is much more
recent. Dark bullet cluster was a while
ago called the dragonfly galaxies.
There's dragonfly 2 and dragonfly 4.
These are galaxies
that rotate exactly according to
Newton's laws.
And so the fact that they rotate exactly
according to Newton's laws
says that whatever is causing galaxies
to rotate too fast is not a property of
matter. But if you had a galaxy where
there was no dark matter, for whatever
reason, it got stripped off or
something, this is one of those lovely
ironies that the existence of a galaxy
with no dark matter is very strong
evidence that dark matter is real
because you can take the dark matter
out. So the DF2 and DF4 also suggests to
me that dark matter is real. So now
while it remains possible that um we
need to modify the laws of inertia or we
need to modify the laws of gravity those
are possible still in my opinion and now
this is Dawn's opinion but it's probably
the opinion of most of the the
scientific community.
Dark matter is likely a real thing. Now
that's great. I've taken you all the way
to dark matter. So now you're going to
ask me. You're going to say, "Don, what
is dark matter?" I'm going to I don't
know.
But I know what it isn't. Okay? I know
that it is not black holes. I know that
it is not rogue planets. I know that
we've done the measurements. We've
looked across nearly every mass range
for compact objects and ruled them out.
So if dark matter is real, it can't be
made of those.
So then you're left with the idea that
dark matter is a particle. And that's
what we've thought about. The name for
the the dark matter particle that we've
called for a long time is a wimp for a
weekly interacting massive particle. And
we have spent the last god 30 years
looking for them in the various ways.
There are three ways that we might see
dark matter. The direct way which says
that dark matter exists literally
everywhere in this room in our
laboratory and the dark matter is
passing through the earth like a wind
and we put up detectors trying to see
those. We have done that and we've seen
nothing.
>> So we should say we have done that for
nutrinos.
>> We've done that for many different types
of dark matter. We just simply put
detectors in labs deep underground and
we can see nutrinos in them. It's true.
But dark matter would have especially
heavy dark matter what these these wimps
um they have a different signature and
we've seen no evidence of dark matter
interaction in these detectors. So
nutrinos are also weakly interacting and
also have mass they are
>> but not enough ma. So wimps are
>> heavy on the um
>> right? Nutrinos are indeed wimps of a
sort. Now we have to be careful what we
mean by wimps. They are weakly
interacting massive particles but we can
calculate and there's just not enough
mass in them. It's not it.
>> Got it. So we need another form and we
have seen zero evidence of this wind of
dark matter through the uh the earth.
Another possibility is you look where
you think dark matter might be
concentrated at the center of galaxies
and if dark matter exists and there's
antimatter dark matter maybe they
annihilate and make photons. And so we
look for gamma rays and various other
signatures of annihilating dark matter.
And there are always constantly
announcements of oh we saw it oh we
didn't oh you know the problem is that
way of looking for dark matter is hard
because there are other ways of making
for instance gamma rays like neutron
stars and stuff and you really need to
understand the details of galaxies
really really well to believe that and
then the final option is what I do where
we smash particles together at high ma
or high energy we try to make dark
matter particles If you make dark matter
particles because they don't interact
except via gravity, they escape with
your detector. So what you're seeing,
what you hope to see is an event where
you collide particles, a dark matter
particle escapes and you don't see it,
but the recoil you see on the other side
because momentum is conserved. So you
see a blob of energy on this side,
nothing on the other side. Maybe that's
dark matter. And that also happens with
nutrinos. So you need to understand
everything about nutrinos and calculate
how many of those you see and then hope
you see more and then that might be dark
matter again that hasn't worked. So
we've ruled out some dark matter
particles but the problem is the range
of space of possible mass if dark matter
is of a particulate form. The range of
viable dark matter ranges from something
like the mass of an asteroid to far
lighter than an electron and everywhere
in between.
And we have looked, we've ruled out some
little spots in that phase space, but
that's a big range.
>> Is it really possible to miss a particle
the size of an asteroid? the
astronomical searches were not sensitive
to that level of of dark matter, but you
know, then you would expect that there
would be some of those in the solar
system. And if they're what we think
like asteroids or something, then we'd
heat them up and we'd eventually see
them. But if they're really like truly
dark matter doesn't interact with
matter, which means they wouldn't absorb
energy from the sun, so they'd be really
dark. I don't know, maybe they're out
there. But the only way we have we
searched for them was um a thing called
microl lensing. So if a massive object
you have a distant star and a massive
object pass between that star and your
eye that star will momentarily brighten.
>> Mhm. And so you just look for these what
they call microl lensing events and you
count them and you see some and we did
see some you know black holes pass in
front of stars and and we've seen them
but we just haven't seen enough. And for
very low mass particles like asteroids
they um they just wouldn't make enough
brightening effect to see. So there's
like a minimum sensitivity of
brightening and that about a third the
mass of a moon. Our moon is about the
sensitivity that we had. So you know
that nobody I think really thought that
these low mass guys were likely. What
they thought was more likely they were
just unseen black holes which I thought
you know I think is completely
reasonable. Then when that got ruled out
I thought okay modified gravity or uh
>> or inertia. Well, now that you know,
bullet cluster and dragonfly seems to
ruled that out. So, I'm stuck in my head
with dark matter seems to be real and it
we don't know what it is
>> and it makes up a giant percentage of
matter in the universe.
>> It is five times more prevalent than
ordinary matter.
>> This is incredible. It is so fascinating
and that's why it's cool. So, if someone
out there is, you know, a young person
wants to get into this, understanding
dark matter is a big deal. I mean, it's
five times more prevalent. The problem
is is, as I told you, if the mass is
ranging from an asteroid to far lighter
than an electron, if you get on an
experiment that looks at one little
range of mass, maybe you weren't the
lucky guy that measured the right place,
you know, and that's one of the reasons
why, as fascinating as I think it is,
I'm not doing dark matter experiments,
because,
you know, if you make an experiment that
searches one mass range, it'll be blind
to another mass range. So what you need
is you need many groups doing all sorts
of radically different experiments
exploring all sorts of parameter space.
And with all that said, until you see
it, there still is the possibility that
maybe we don't understand gravity or
inertia, right? You know, you can't rule
that out.
>> If there is dark matter out there,
you're hoping it's actually somehow
detectable.
>> I mean, I don't know what it is. I think
it's cool. It's very, very fascinating.
That is one thing I really do hope in my
lifetime is is understood because I' I'd
like to know the answer to that.
>> And that that's the thing that you could
there legitimately you can see a
discovery of.
>> You got to get lucky though. I mean you
got to look in the right place whatever
it is.
>> Just imagine or you have to come up with
that really cool theoretical idea that
everybody's overlooked which is another
possibility. And there are people who
are really really religiously hating
dark matter largely because we've looked
so hard for so many years and the
experiments in today's world are a
million times more sensitive than when I
was a a starting student and they still
haven't seen anything and that's why
people really hate dark matter. I mean
some of them because they think we
should have seen it by now but
>> you know uh I don't know. I mean, I'm a
sucker for direct observation. Not
indirect is obviously also really great,
but direct. Just imagine pointing your
telescope in a certain direction and
because of some artifact of cosmology
being able to directly detect a giant
amount of of a thing that you could say
is dark matter.
>> Yeah. You would see it orbit things
orbit it or it would eclipse things in
front of it or
>> Yeah. like in an obvious way cuz uh some
of the stuff you mentioned with DF2 and
DF4 those are like brilliant indirect
um deductions that there should be
something like dark matter but some
obvious yeah blocking oluding this kind
of thing we did that in the 90s with
experiments called macho ogle and some
others they looked for a black hole that
you just can't see you know black hole
you can't see it's perfect it's a
perfect candidate for dark matter. And
if there's enough of them out there,
remember there's five times the number
of stars, which means there's a whole
lot of freaking black holes out there.
We should have seen them and we didn't.
>> What a grand mystery. We covered so many
of them. I could talk to you for a
thousand more hours. Don, let me if I
can uh ask you about a little bit more
of a on the personal side. Um, you have
a really inspiring life story. Your
folks didn't uh go to college. Can you
just tell me about your childhood and
where you found the love for physics and
science and maybe how you found your
journey to to to become a physicist
given the the context of where you came
from?
Well, uh, you know, I grew up a poor kid
in the Boondocks. Great parents, but not
ones that could guide me terribly
academically, but very, uh, very
nurturing. You know, my mom would laugh
that she could stop helping me math
after like sixth or seventh grade, you
know. Um, but they were supportive. And
there were a couple of things that
couple three things I think that folded
into it. One is I was a voracious reader
as a kid. I loved science fiction. I
would read a book a day. It drove my
mother nuts cuz she would try to be
nice. She'd buy me a book and I'd say
thank you and the next day it'd be done.
You know, it just drove her completely
nuts. But anyways, but science fiction
is good for
fostering imagination. And so that's
precisely what it did. In addition, um,
and this is where the more serious
science came along, there were lovely
science communicators that were popular
in the 1970s. Isaac Azimoff, Carl Sean,
guy by the name of George Gamma. They
wrote books about science aimed at a lay
person. I was a kid. I surely couldn't
read a a textbook and understand it, but
I could read and and you know, get a a
hint of what science was. And on top of
that, you know, I was, as most
scientist, people who became scientists,
irrepressibly curious about everything.
Um, and I had sort of a quasi
philosophical
mind. I mean, I was interested in things
that questions that have in the past
been theological and then philosophical
and now are more scientific. Questions
about how did the universe come into
existence? Um, why is the universe the
way it is? Why are the laws of the
universe what we see them to be? How
will the universe was it created? How
will it be destroyed? These are, you
know, big questions that have bothered
humanity for, well, thousands of years.
And so, you know, I did you you said I
had uh um you know, philosophy and
religion minors in college, and I did
because I was curious about that. Um I
was hoping that learning that history
might help me understand these
questions. Um and it was in college
where I came to realize that the answers
that I were searching for were not to be
found in those directions, but I still
learned about how those questions have
been asked in the past.
Um, and so I became a a scientist and
the only question was was I going to be
uh a cosmologist/astrophysicist
or a particle physicist. And when I had
to make that decision, it was the
mid80s. And at the time, there were a
lot fewer cosmology measurements. There
was an awful lot of thinking about the
universe and not enough measuring.
Whereas with uh particle physics, by
God, you could do experiments. And so
the what attracted me was the ability to
actually get an answer and not just mull
over what an answer might be. And so I
became a particle physicist. Um it was
difficult without having you know uh
family mentors or anything like that but
but you know I managed and that actually
is why well I'm here and why I have
spent a fair bit of my time writing
books and so forth because I figure that
there has to be some other kid out there
in Iowa, Kansas, Montana somewhere out
in some little town without a lot of
access to the kinds of thing that
people, you know, who have highly
educated parents do. And I'm hoping
that, you know, some of them will have
read some of the things I've written and
will find their own path forward because
I found it very rewarding over the
years. And um, you know, I've been doing
this long enough that I'm I'm sure this
is true. I've had kids come up to me at
the lab and say, "Hey, I'm a summer
intern because I saw your video or read
your book or you know, whatever." Um, so
I know that at least I've made a small
impact. I mean, always would like to do
more and, you know, I appreciate the uh
opportunity that your uh audience
affords me um cuz I I think it's
important to talk about these things.
These are really cool, fascinating
questions. They are unanswered and they
are just waiting for youngsters to come
and spend some time thinking about them
because one of your viewers might be one
of the people who answer these questions
that have stymied very smart people for
decades.
>> And we should also say that you're a
legit scientist. So we we'll mention
Sean Carol who's a legit scientist,
legit physicist, but is also a good
science communicator. Anyway, I did want
to mention, I don't know if this is
true, but I I kind of heard you talk
about this, that when you first showed
up to Firmeny Lab, you were like working
crazy hours, working extremely hard,
>> 8:00 a.m. to midnight.
>> I did.
>> Uh, first of all, I love that.
>> Uh, can you speak to what drove you and
maybe the value of hard work in those
context in your in the early career when
you discover a thing you're passionate
about?
Well, yeah. I mean, obviously being
smart, you know, if you're Einstein,
then maybe you can slack, I guess.
Although even he didn't do that, but I'm
not Einstein. But the fact is when I was
young and I was unencumbered, no no
family, no kids or something. I couldn't
imagine anything I wanted to do more. I
mean, some people they want to go out to
the club, they want to, I don't know,
play soccer or something, but I wanted
to make measurements and I wanted to
understand and and and learn, and that
was fantastic. And so, as a graduate
student, and this isn't for everybody,
but I worked outrageously. I would from
Monday through Saturday, I would be at
the lab voluntarily because I wanted to
be from 8:00 a.m. to midnight. And on
Sunday, I would work from 8 until about
5:00. And that's because from 5 to
midnight I had to wash clothes and buy
groceries and things like that. And I
loved it, you know, uh, and I still love
it. I can't do that anymore. Um, but but
that's simply because I have other
obligations, but had I been rich, I
would have done the same thing. You
know, it's it's something I truly truly
loved. And the I mean there is
absolutely nothing more fascinating to
me than having a hard problem and
figuring it out. And that you know that
work ethic. Well, there's a couple of
things that separate
smart people from no kidding scientists
cuz all scientists are smart. But the
thing that that separates that that that
many scientists have is a a drive and a
real grit. the um
for me and for so many scientists that I
know
trying to measure something and having
it not work just kind of ticks me off
and I am not going to let the universe
in my lab or whatever
beat me. And you know some people they
you know if the thing breaks it's like
oh man that didn't work and a lot of
people well I'm going to go home I'm fed
up. No, it would just kind of make me
mad and I'd put more effort into it. And
you know, not every I mean, okay, I was
crazy. I worked long hours, but but I
think the people who are really good at
this will do maybe not that much. You
know, some people have to have a better
life than that, but but a lot because it
it's just you can't imagine not knowing
the answer. Mhm.
>> And that if when when you see that as an
older guy, you don't maybe not to that
degree, but when you see that kind of
drive, that that that
intensity of trying to get the answers,
you know that person's a winner. And and
so if you know some student out there,
if it doesn't, you know, bring you joy,
as uh what's her name? The Japanese girl
says, if it doesn't bring you joy, then
it might not be for you. And then you
could be a person who reads about it and
you know is involved. But if you want to
be a real scientist, it it has to be
just part of what you are here.
>> And by the way,
it is a hard life, but it is also a very
fulfilling one. So working hard towards
the thing you love is a really
fulfilling way to to be. I think that's
true for an artist or something, you
know, anybody, a musician, you know,
musician, they just keep practicing
because it is who they are.
>> Well, I'm glad there's people like you
at a place I admire like Fermy Lab, uh,
one of the many places in the United
States, in the world that, uh, is
carrying the beacon of great science and
great engineering
forward. Uh, Don, thank you so much for
everything you do, for all the teaching
you do uh, online, for all the
incredible physics work that you do at
Firmay Lab, and uh, thank you so much
for talking today.
>> Thank you for having me.
>> Thanks for listening to this
conversation with Don Lincoln. To
support this podcast, please check out
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you can also find links to contact me,
ask questions, give feedback, and so on.
And now, let me leave you with some
words from Marie Kuri, a twotime Nobel
Prize winner. First in physics, second
in chemistry. Nothing in life is to be
feared. It is only to be understood.
Thank you for listening. I hope to see
you next time.