(soft music)
- My name is Wick Haxton,
I'm the chair of the physics department,
and it's my honor to welcome you
to what is now the 21st annual
Robert Oppenheimer lecture.
This lecture this week comes
at a really special time.
Next Monday marks to the
day the 150th anniversary
of the University of California.
It was at that point that the
state assembly passed the bill
that created the University
of California campus
here at Berkeley.
The charge that was given
to Berkeley at that time
is interesting, it's very
appropriate for today as well,
to provide instruction and
thorough and complete education
in all departments of
science, literature, and art,
industrial, and professional pursuits.
And today we actually
encapsulate this in the UC motto,
which is a few outlooks to
bring new knowledge to light.
So we're proud that on our 150th birthday
Berkeley stands as the world's
premier public university.
It combines outstanding scholarship
with our goal of making
education accessible to all.
The Oppenheimer lecture,
the 21st of which you'll hear tonight,
was established in 1998.
The past lecturers are literally
a who's who of theoretical physics.
They include C.N. Yang, Freeman Dyson,
Frank WilCzek, Gerard 't
Hooft, Robert Laughlin,
Martin Rees, Ed Witten, Stephen Hawking,
Claude Cohen-Tannoudji, Murray
Gell-Mann, and Kip Thorne,
and one other, our own Marvin Cohen
who is in the audience tonight.
Robert Oppenheimer was born in 1904,
he grew up in an upper middle
class family in Manhattan,
he graduated from Harvard,
majoring in chemistry,
entered Cambridge University
in 1924 as a graduate student
in the hope of working
with Earnest Rutherford.
Then he left two years later in 1926
to finish his PhD with
Max Born in Gottingen.
He published more than a
dozen papers while with Born,
mostly focused on the theory
of the new quantum mechanics,
this included what is
probably his most famous work,
the Born-Oppenheimer approximation,
that describes how you
simplify molecular physics
by separating the slow
motion of the nucleus
from the faster morion of the electrons.
His oral PhD exam was
administered by a Nobel Laureate,
James Frank, who stated afterward,
"I am glad it is over,
"he was on the point of questioning me".
Thereafter Oppenheimer joined
Caltech as a research fellow,
but also spent most of his
first year after his PhD
working with Ehrenfest in Leiden,
and Wolfgang Pauli at ETH.
In 1929 on returning to the US,
he accepted an associate
professorship from Berkeley,
and he remained here
for the next 15 years.
During this period he did
a lot of marvelous work,
and built a fantastic
theory group around him.
He published one of the most
famous papers with Volkoff,
establishing what is known
as the Tolman-Oppenheimer-Volkoff Limit
on the maximum mass of a neutron star,
the mass above which a star
has to collapse into a black hole.
The observation just six months ago
of the merger of two neutron stars,
helped us fix that maximum mass
at just under 2.2 solar masses.
His scientific leadership that he
demonstrated here at Berkeley
complicated his later life
and his role in science.
He was selected in 1942 to lead
World War Two's Manhattan
Project's engineering lab,
which he helped sight at
Los Alamos, New Mexico,
very near a ranch that he owned.
His work culminated there in
the successful trinity test.
The decision by our government
to then use atomic weapons
in the war against Japan was an issue
that troubled Oppenheimer
for the rest of his life.
After World War Two,
Oppenheimer became very much
the public face of science in the US,
and he was featured on covers
of Time Magazine and Life.
This period of his life
was effectively ended
a decade later with the controversial loss
of his security clearance in 1954,
reflecting the fears at that time
that were generated by the new cold war.
Some ten years later, there
was some resolution to this
with the honor that President
Kennedy bestowed on him,
the Fermi Award that was presented
by Lyndon Johnson after Kennedy's death.
In a sense Oppenheimer's legacy
here at Berkeley is a simpler one
that we strive to continue today,
and it's really summarized by a plaque
that you can visit by going up
to the fourth floor of old Le Conte,
and we took a photo of that this morning.
It simply says that in these
corner offices 1929-1942,
J. Robert Oppenheimer
created the greatest school
of theoretical physics
the world has ever known.
So it's a very high standard
that we try to live up to today.
That quote came from Hans Bethe.
So now it's my great pleasure
to introduce my colleague,
Saul Perlmutter,
who was the UC professor of
physics in 2011 Nobel Laureate,
he's going to introduce
tonight's Oppenheimer lecturer,
Michael Turner from the
University of Chicago.
Saul.
(audience applause)
- Well good evening, I
have a great pleasure
of introducing our
distinguished speaker today
who is Professor Michael Turner.
He's the Bruce V. Rauner
Distinguished Service Professor
at the University of Chicago,
and also the director
of the Kavli Institute
For Cosmological Physics,
which he helped establish in 2004,
and he's also a favorite colleague
of any of us cosmologists.
Michael received his B.S. from Caltech
and PhD from Stanford,
and then together with a few
theoretical astrophysicist colleagues
proceeded to be a driving force
in bringing together the fields
of particle physics and cosmology.
Along with many key
papers and the training
of many grad students and post docs,
he together with Rocky Kolb
founded the Fermilab astrophysics group,
and then they wrote a
book, The Early Universe,
that became a standard in the field,
teaching a whole
generation of cosmologists.
I think it's worth commenting
that when a field is relatively small,
a few people really help
shape the mood of the field,
and Michael and Rocky set a
standard of playful curiosity
that I think has really
played an important role,
so I just called it out.
His work itself addressed and often set
most of the agenda items of the field,
from big bang
nucleosynthesis, dark matter,
and it's candidate particles to inflation
and the current so-called
Lambda-CDM picture of cosmology.
With respect to this,
I can personally attest
to a minor but fun claim
to fame of Michael's,
which is that right after we measured
the accelerating
expansion of the universe,
Michael and our Berkeley
colleague, Martin White
led a paper that I joined them on
that needed a term to describe what it is
that is causing the
acceleration of the universe,
and I remember a phone call with Michael,
in which he convinced me that rather than
calling it something
nerdy like elastic energy,
we should use the Star
Wars-y term dark energy,
and of course he was absolutely right.
If you want to make a
field exciting as it is,
it needs to be able to talk about things
like dark matter and dark energy
as it's fundamental mysteries.
And of course I'm sure Michael had
already started using this term
and was just letting me
catch up on that night call.
Finally, Michael has played
a key role in science policy,
he led the mathematical and
physical science directorate
at The National Science
Foundation in the mid 2000s,
and also led a very influential
National Academy of Science report
called Quarks to the Cosmos,
that helped shape science
policy in physics.
Of course I personally
remember the early days
when he had time to serve on committees
reviewing work we were
doing here at Berkeley,
and he was one of the
few committee members
who thought that we were
doing something important,
so for me it's a real pleasure
to have the opportunity
to welcome Mike Turner as this
year's Oppenheimer lecturer,
and his title is What
Happened Before The Big Bang,
And Other Big Questions
About The Universe,
so please join me in
welcoming Michael Turner.
(audience applause)
- Thank you, that was very generous.
Well good evening, it's a real honor
to be the 2018 Oppenheimer lecturer,
and it's also a real
honor to be introduced.
Wick and I were graduate students together
at that other school on the other side,
San Jose State or something like that,
I can't remember what it's called,
and Saul and I are very good friends.
So not only is it an honor
to be here as the lecturer,
but I get to talk about
my favorite subject,
which is cosmology.
And so I thought I would start out slow,
and then speed up to this question
about what happened, oh I
didn't intend that joke,
but that was pretty good.
So the universe is really
big, does everybody know that?
Whenever somebody asks
you about the universe
the answer is billions.
And it's often beyond the reach
of our minds and our instruments,
but the past two decades have
seen revolutionary progress
due to big ideas and powerful instruments.
And because, as you heard,
Oppie was an idea guy,
I'm gonna emphasize the
ideas over the instruments.
So what is the big idea
that I'm gonna emphasize?
And it's been mentioned already,
and you'll see it throughout the talk,
and the big idea are the deep connections
between the very small,
the elementary particles,
and the very big.
So that's the big idea
that has helped power
this revolution in our
understanding of the universe.
Now even if you're a theorist,
you get seduced by the
powerful instruments,
so I've gotta remind you
that this is science,
it's not science fiction,
and so we actually rely on evidence.
I know we have to remind people
that evidence is a good thing.
And so we've been helped
by powerful instruments,
so you know this is atop
Maunakea and the Keck telescopes,
and other people have telescopes in Chile,
the Europeans and the
Carnegie Institution,
we have fantastic telescopes
at the South Pole,
there are big telescopes in space,
let's see if I can name them,
the Hubble, the Chandra Telescope,
the Fermi Gamma Ray Observatory,
and the Spitzer, and oh my God, let's see,
Hubble was Chicago, Chandra was Chicago,
and Fermi was Chicago, I had
never noticed that before.
(audience laughing)
Okay, a quick orientation to the universe,
so I'm gonna start slow,
and then I'm gonna speed up,
so the basics of our universe,
100 billion galaxies,
each lit with the light
of about 100 billion stars,
so there's the billion number again.
And they're carried away from each other
by expanding space and
a big bang beginning.
So that's the basic
architecture of our universe,
and I just wanna talk a little bit
about the discovery of those two things
that happened about 100 years ago,
not quite 100 years ago.
So this is the night sky,
and most of these stars are in our galaxy,
and I think this is from
a California mountain top,
and can you see the trees there,
so it's a big part of the sky,
and about 100 years ago all
we knew of was our own galaxy,
and these fuzzy little patches on the sky.
Do you see that little fuzz ball?
Called the Nebulae, and nobody
knew what the Nebulae were,
and the person who solved that puzzle,
where did he get his PhD?
University of Chicago, so that was Hubble.
So Hubble using the 100 inch
telescope at Mount Wilson,
the Hooker telescope resolved
stars in that fuzzball,
actually let me just go back,
that's the Andromeda, that's
one of the few galaxies
you can see with the naked eye,
and showed that it was an island universe.
It was another galaxy, and so that meant
that most of the nebulae
were other galaxies,
and Hubble enlarged the universe,
I think this is a record.
I'm not even sure Trump's
inauguration beats this record.
(audience laughing)
We're not taping this are we?
He enlarged the universe up
by a factor of 100 billion.
So evidence, so this is the deepest image
that we have of the universe.
This is the Hubble deep field,
and in this image you see a
lot of smudgy little things,
and you see a couple of stars.
There's a star, there's a star.
This is a tiny bit of the sky,
and in this image there
are 10,000 galaxies,
and this is one ten millionth of the sky.
And so if you multiply
ten million times 100,000,
you get 100 billion
galaxies in the universe.
So 100 billion galaxies in the universe.
The other thing that Hubble did
was he noticed that the galaxies
had a pattern of motion that
we call the Hubble flow.
Here's our galaxy, and the other galaxies
are moving away from us.
And the galaxies that are
further away are moving faster.
And if you think about this,
this looks like in the
past all the galaxies
must've been on top of one another,
and in fact, this pattern of motion
is the pattern of the big bang.
But the person who correctly
interpreted that for us,
with a little bit of help
from some other theorists,
was Einstein.
So the big bang was not an
explosion of galaxies into space,
it was an explosion of space
with the galaxies being carried along.
So Einstein's general theory of relativity
says that space is flexible, time warps,
so space being flexible, the
expansion of the universe
is actually space expanding
and galaxies being carried along,
and I'll show you how this works.
So there's space, there are the galaxies,
can you see it expand?
Okay, now this is our galaxy,
let's line up those three
time frames together,
and so you can see from our point of view
all the other galaxies
are moving away from us.
So are we the center of the universe?
Well the way we do things
in science is by polling.
How many people say we're at
the center of the universe?
(audience laughing)
Well, let's try another galaxy.
If we line them up on this galaxy,
that galaxy sees the same thing,
everyone moving away from it.
And of course, I should have
drawn more galaxies here.
If we were in Cambridge Massachusetts
at one of those small
schools there like Harvard
it would take a third
time to convince them,
so we'll line it up on that
and see the same thing.
So no center, just different perspectives.
Another way to say this is that everyone's
at the center of their universe.
I know on the left coast
you don't know that,
but at Harvard everyone's at
the center of their universe.
So let's go back before this revolution
of joining particle physics and cosmology.
The big questions of cosmology in 1978
were articulated by Allan
Sandage who was Hubble's student,
and Sandage said, "Cosmology
is just two numbers,
"H naught and Q naught", and I'll tell you
a little bit about those numbers,
and they are really important numbers,
and this is a beautiful drawing
of the 200 inch telescope at Mount Palomar
that doesn't project that well,
and Sandage said all of those were gonna
resolve that with this telescope.
So he called cosmology a
search for two numbers.
So let me tell you just a
little bit about those numbers,
they're important.
So here's the size of the
universe against time,
so the universe is getting bigger,
and so that means the
universe is expanding,
but of course it's slowing
down due to gravity,
and so the question is how
much is it slowing down,
is it slowing down enough so that it
eventually stops expanding
and falls back on itself,
or does it expand forever?
And so let me tell you about H naught,
that's the expansion rate today,
for the mathematically inclined,
that's the slope of this line,
and that gives you the
age of the universe.
That's a pretty important number.
Q naught is the deceleration parameter,
and I'm gonna use a technical
term for mathematics,
it's the droopiness of the line.
So if the line really droops,
it's slowing down a lot,
and the universe will re-collapse,
so these two numbers were age and destiny,
that's pretty important.
So that was the conversation,
and just to calibrate things at that time,
cosmology was tens of astronomers
working alone, solitary,
trying to figure it all out,
without the help of physicists.
Okay, you may have
heard about a discovery,
boy, you hear a lot about
Nobel prizes here at Berkeley,
so not all the Nobel prizes
go to people at Berkeley,
even though maybe they should.
Penzias and Wilson got
a Nobel Prize in 1978
for detecting the microwave
echo or the big bang,
cosmic microwaves, and the upshot of that
is they discovered that
it wasn't just a big bang,
it was a hot big bang,
and in the beginning,
and this is a technical term,
it was hotter than hell.
And when you heat something up,
it's reduced to it's most
fundamental entities.
And around 1980 the particle
physicists were realizing
that the fundamental entities
were the quarks and the leptons.
So the six quarks that we now know of,
up, charm, top, down, strange, bottom,
and the electron and it's friends
including the neutrinos and
the force carrying particles,
the photon, the gluon, and
then of course in the middle,
the Higgs boson.
So in the beginning the
universe was quark soup,
so that's the big idea, and
so here is the universe,
starts as quark soup,
and then as it expands
it cools and layer upon
layer of structure is built,
and at that time in 1980,
this is the part that we understood
at about 1/100,000 of a second,
the universe was neutrons and protons,
the universe was a nuclear reactor
and made some helium and deuterium,
and then atoms formed, and
then at about 400,000 years
gravity took over and took
any lumps in the matter,
and brought them together
and made the galaxy.
So this is the picture we had,
but I call your attention to this early,
this first microsecond,
the quark soup era,
so is anything interesting
happened during that time?
So I came along to cosmology late,
and so I was assigned
the first microsecond,
that's all that was
left, so the question is,
did anything interesting happen then?
And I'm gonna try to argue that
that is the most interesting time.
And so the 1980s, I guess
if you can remember them
you weren't there.
Isn't there some joke like that?
Anyway, I can sort of remember them,
and Saul alluded to this.
We had a really good time,
these were the go-go days of
cosmology, new ideas every day.
It was a great time to
be a young scientist,
and the particle physicists
were trying to figure out
how to unify the forces
and particles of nature,
and we had the most powerful
accelerator, the big bang,
and so we were looking at the
implications of these ideas,
so we had a conference at Fermilab
called Inner space Outer space in 1984
that kind of was the
announcement of this field.
I'll show you how important
it was in a second.
I'll tell you a little
story about this book,
Rocky Kolb was mentioned earlier,
and we organized this conference,
and we had to get the book published,
so we went to the
University of Chicago Press,
and they said,
"Well we don't do
proceedings of conferences",
and we said, "no, this is
not a conference proceedings,
"this is a milestone in human knowledge",
and so they said, "okay, we'll do that".
And not only that, 'cause
last week was the Olympics,
so probably most people
don't remember this.
This inner space, outer space,
the official conference of
the 1984 Summer Olympics,
and not only that, Rocky and I pioneered
financing of conferences by
selling conference T-shirts.
These are still available on eBay,
make sure you get a genuine one.
So lots of ideas, and what I like to say,
at least for this talk, is we changed
the vocabulary of cosmology.
So we changed the conversation.
So we talked about Q naught and H naught,
and you'll only hear
about them one more time.
And so the words now that you
hear about are quark soup,
dark matter, dark energy,
inflation, cold dark matter,
I don't know if I'll talk
about WIMPs and baryogenesis,
but the vocabulary of
the field was changed,
and also it went from a
little cottage industry
to we brought in those nasty physicists,
so physicists and
astronomers working together
to figure it all out.
So let's talk about dark matter,
inflation, and dark energy.
So in 1970s, the late Vera
Rubin discovered dark matter.
So how did she do that?
So she was looking at,
I believe this actually
is the rotation curve
of the Andromeda galaxy,
so here's the Andromeda galaxy,
and the stars in Andromeda are
moving around on Andromeda,
and this chart here is how fast
they're moving around Andromeda,
plotted against how far their distance
from the center of Andromeda.
And I said flat rotation curve,
so this is called the rotation curve.
You'll notice that the
stars that are way out there
are still moving fast.
Does everyone see that?
And if all the gravity
were due to the stars,
you don't need math to
realize that shouldn't happen,
'cause when you're
getting way far out there,
the gravity is weakening, and
you better be moving slower,
otherwise you're gonna escape.
And so this was the
evidence for dark matter,
and so the upshot is the galaxy
has this starry nugget, but
it's surrounded by an enormous,
we call it a halo of dark matter.
So the question was,
what is the dark matter?
And I won't bore you with going through
all the things we eliminated,
but the best bet is the dark matter
is a new form of matter predicted to exist
by these particle physics theories
that unify the forces of nature.
So that's the idea, the
dark matter particle
is something new, and here are,
actually these are all
still current today,
this is a slide from 1990, the axion,
the neutralino, everybody's
heard of super string theory,
so the neutralino is the lightest
super-symmetric particle.
Here were the neutrinos,
so those are particles known to exist,
so they're not quite as interesting,
and we now know they have mass,
but they only contribute a few percent,
so they're a spice.
So the idea is that the dark matter
is a new form of matter in the universe.
So another puzzle that
had been with people
was the following, is
here's our universe today,
the galaxies are blue,
and they're nicely distributed
around the universe,
and we live in an old universe.
And you can ask yourself,
well how did the universe have to begin
to get to a universe that
looks as regular as ours,
and is as old as ours?
And it turns out that it requires
very special initial conditions.
You'd have to begin the
universe in a very special way,
and Stephen Hawking and
a graduate student ask,
well, if you just kind of threw a dart
at the dart board of initial conditions,
just started the universe any old way,
what would happen?
In a very short amount of
time I'll let you read it,
you would end up with a mess, black holes,
and you wouldn't end up with our universe.
Okay, so how does that work?
Well, the universe
could've started that way,
so it's not a logical inconsistency,
they didn't show there's no way
to start the universe to get ours,
but they said it would
have to be very special.
So there was a challenge out there,
can you make the current
state of our universe
less dependent on the initial conditions?
And so that's explained by this idea
of cosmic inflation that
I'm gonna talk about now.
So the idea is very, very simple,
so you take this highly
irregular universe,
or this more typical universe,
and you focus on a tiny little bit of it,
and the mathematicians say
that even if you take
this initial space time
that's highly curved and all kinds
of bendings and everything,
if you take a small enough bit of it,
it will look smooth and flat,
but of course it won't
be big enough for us.
Well, blow it up, so if the universe grows
by an enormous amount,
which I've shown here,
so take this little black thing
and it becomes this big black circle,
it's smooth, it's flat,
and we can fit in it.
So if you have this tremendous
growth spurt early on,
you can get around this dilemma
of needing special initial conditions.
And just as they say,
actually no one watches TV,
but remember the old commercials,
but there's more, and the more is,
remember I mentioned that
in order to understand
galaxies and structure in the universe,
you need lumpiness, you need the matter
to be distributed not uniformly,
you need there to be more
matter in some places
and less matter in others.
And so what inflation
does, remember what it does
is it blows things up.
So where is there natural
lumpiness or variations?
At the subatomic scale they're
called quantum fluctuations,
things are jitterbugging around,
but the subatomic scale is
much smaller than a galaxy,
so how can that work?
Well, inflation stretches these
subatomic quantum fluctuations
into fluctuations of enormous wave length,
and they end up being places
of more matter and less matter,
and they become the seeds
for the large scale
structure in the universe.
So how did this happen?
So when we used to explain this, we said,
well there's this scaler field,
and we start with a state of false vacuum,
and we didn't know any scaler fields,
and now we know one, the Higgs,
so the Higgs is scaler field,
so there's a field that
might be the Higgs,
probably not, but is a cousin of the Higgs
that drives inflation, and
so this early growth spurt
is driven by a scaler field,
related hopefully to the Higgs field,
tremendous amount of expansion,
and when this false vacuum energy decays,
it creates the quark soup.
That's idea number two.
And Stephen Hawking,
I think everyone recognizes
Stephen in this picture,
and I'll let you find me in this picture,
I'm the one with the good legs,
so that's just a little hint.
So Stephen Hawking had
the world's most amazing
workshop in June of 1983,
where most of these
details were worked out.
I guess Jim Bardeem is smiling,
and Stephen is smiling,
and some of us look more,
well Paul Steinhardt is not smiling,
but it was a fantastic workshop
where work actually got done,
and the details of this got worked out.
So now let me bring you to dark energy,
which Saul mentioned, and
so Sandage carefully defined
the deceleration parameter,
because we know the
universe is decelerating,
not accelerating, so you have
to put a minus sign in there,
and of course once Saul and
his colleagues measured it,
it turns out that the universe
is actually speeding up.
So how can that happen?
Well, repulsive gravity is a
feature of Einstein's theory,
and I don't mean that Einstein's theory
is repulsive to study, but in it
you can have forms of energy
that have repulsive gravity,
and they're called dark
energy as Saul explained,
so that's the definition of dark energy,
so what would be an
example of dark energy?
So the simplest example of dark energy
is the energy of quantum nothingness.
So I know this is California,
so this is the zen part of the talk.
So what is nothing?
Nothing is something,
it's filled with particles
living on borrowed time
and borrowed energy,
and so the quantum vacuum is alive
with these virtual particles,
and I can prove it to you,
but I bet you're willing to trust me,
although you should never trust us,
nullius in verba, take
no one's word for it.
The gravity of quantum
nothingness is repulsive.
And so this is a great theoretical triumph
that the quantum energy of the vacuum
explains cosmic acceleration,
give or take a factor of ten to the 55.
Okay, we'll whittle that down,
so that's one of the puzzles,
we'll come back to that,
so let's see, so cosmic acceleration
is caused by the repulsive
gravity of quantum nothingness,
so this quantum nothingness
has another name,
and it's Einstein's cosmological constant,
so he invented this by accident,
which is why his picture was on the cover
of that science magazine.
Any questions?
Well one was phoned in
by Sir Arthur Eddington,
you may remember, he was
one of the early adopters
of general relativity,
and there's a wonderful
story about Eddington.
So he's a real expert on
it, and he was interviewed,
I think by the New York
Times, and they said
that only three people
understand general relativity,
and he said, "who's the other one?"
Anyway he says, "no experimental result
"should be accepted until
confirmed by theory".
And so what he's really saying
is science is not just a book of facts,
but it's understanding,
and so we've gotta resolve,
within ten to the 55 is not good enough.
So we've got a bit of a puzzle there,
so we put all of these pieces together,
and this is our story of
the universe right now.
We have a pretty name for
it, it's called Lambda CDM,
so Lambda is the symbol
for Einstein's cosmological constant,
and then CDM is that dark
matter is slowly moving,
so we call it cold.
So here's our story, a
jiffy after the beginning,
there's the definition of a jiffy,
we have a tremendous burst of expansion,
that was the inflation,
that smoothed space time,
created the hot quark soup,
and turned subatomic fluctuations
into the seeds for galaxies.
And then up until 1/100,000 of a second
we had the quark soup era,
during which ordinary matter
and dark matter were created.
From 1/100,000 of a second to 300 seconds,
the neutrons, protons, and then the nuclei
of the lightest elements were created.
And then from about 100,000
years to five billion years,
the gravity of dark matter
builds cosmic structure
from the quantum seeds
that I talked about.
And then at five billion years,
the universe starts speeding up,
and dark energy takes over,
speeds up the expansion,
the structure formation is over.
So that's our story today, very different.
So I showed you this picture earlier,
so indeed interesting
things were happening
back here during the quark soup phase,
that's where the dark matter
and ordinary matter evolved,
and this inflation happened.
So it kind of set, it established
some of the most important
of the universe today.
So we've got these seeds that
were created by inflation,
and then gravity, this is an easy theory,
the rich get richer,
and the poor get poorer,
so where there's more matter
gravity pulls more matter in,
and you get galaxies, and
where there's less matter
nothing happens.
So structure gets built up by gravity,
and the way the gravity gets built up
is small things like galaxies form first,
and then larger things form later,
and this theory is highly predictive,
better than this cartoon,
which shows time going down,
much more predictive theory
than this cartoon would suggest.
So I know it's a bit quaint,
but evidence still counts in science,
so you can't just have a good story,
you have to have evidence
that backs it up,
and so there's a wealth of
evidence that backs this up,
and so I'm just gonna quickly
go through some of it.
So this is a graph that I
ask you to bear with me on,
this is a wonderful graph that testifies
to how powerful our instruments are,
so this is the rate at which
stars and galaxies form,
actually it's the log rhythm of the rate,
but don't worry about that,
and since this is from
a Hebrew manuscript,
it reads from the right to the left,
so here's time zero, one billion years,
two billion years, three billion years,
ten billion, and then this
last little tick is today.
And so it shows the
formation of stars peaking
at about the time that this theory
called dark matter says,
and then falling off.
And to me this explains a lot,
because this is a log rhythmic scale,
so star formation has fallen off
by more than a factor of 30,
so a lot of the evidence comes from
the cosmic microwave background,
so I wanna talk a little bit about that,
so here we are, we look out in space,
we look back in time,
so here are some of the
very distant galaxies
that are seen in the Hubble deep field,
then there's a time we can't see back to,
because stars hadn't lit up yet.
We call that the dark ages,
and then here is where those microwaves
that Penzias and Wilson had discovered,
so they're coming to us
from when the universe
was about 400,000 years old,
before there were stars,
before there were galaxies,
and it reveals the
distribution of the matter.
It gives us a snapshot
of the baby universe.
So now let me show you
what that looks like,
and again, I have to come
back to Berkeley here,
so the Cobe satellite, a
team led by George Smoot
discovered the variations in the intensity
of the microwave background.
That was announced in 1992,
and so the blue spots are
where the density is lower,
and the red spots, well
none of them here are red,
are where it's higher, I'll
come back to that in a second,
and so you're seeing the
distribution of matter
in the infant universe.
And then the WMAP satellite
that was flown by NASA,
and then most recently,
the Planck satellite
has given us our best view of this,
of the infant universe.
And I wanna just point something out here
that is absolutely remarkable to me.
So you all know about product placement,
it's really important,
SH, Stephen Hawking,
you wanna get his agent.
Product placement on the
microwave background,
how did he do that?
So this is the best picture we
have of the infant universe,
and this is a test for whether
or not you're a cosmologist.
If you're a cosmologist, you look at this
and your heart goes pitter patter,
you just get really excited.
If you're not a
cosmologist, you look at it
and says that looks like white noise,
which is really what it is.
So let me tell you a little bit about it,
so it's a color scale, and where it's red,
the intensity of the microwave background
is a little bit bigger.
How much bigger?
.001%.
Where it's blue, the microwave background
is a little less intense by .001%.
So this is the distribution of matter
in the universe before
stars, before galaxies,
when it was 400,000 years old,
and so we just stare at
this and ask ourselves,
is this was is this what
inflation plus cold dark matter,
is this what Lambda CDM predicts?
So we're really good at staring,
well that's not quite what we do.
So what we do is we measure
the difference in temperature
between two points on the sky,
separated by an angle
of a tenth of a degree,
2/10, one degree, 18 degrees, 90 degrees,
and this is the temperature difference,
and these are the measurements,
and the curve is not some curve
that I carefully paid an undergraduate
to draw through all the points,
that's the prediction of the theory.
And so our universe,
this is really amazing,
our universe is described,
this curve has six parameters,
six numbers describe our universe.
The last time I checked
it took ten numbers
to do phone number in the United States,
and then you gotta add
the international codes.
That's pretty good.
So that's the evidence, and I think,
I had to look very hard,
Wick and I ended up with
the same picture of Oppie
at the blackboard showing as a theorist,
it's very hard to find a
picture of him smiling,
but when he saw this data,
there he was smiling.
So this is the kind of thing
that makes a theorist smile.
And so if this story I'm
telling you is correct,
and I've given you some of the evidence,
that means when you look at
the microwave background,
you're looking at quantum fluctuations
that were imprinted on the universe
when it was a jiffy old.
And these quantum fluctuations grew,
these are on tiny, tiny
scales smaller than a proton,
and they grew into the largest
objects that you can imagine.
So is that a connection between
inner space and outer space?
This slide is my elevator speech
about inner space outer space.
For Allan Sandage, yes indeed,
we measured H naught, he would
be a little bit disappointed
that it was Wendy Freedman who did it,
but that's okay.
And the deceleration parameter,
you carefully defined it to be positive,
but it's negative, so the
universe is accelerating,
and so I think if he were still with us,
he would just be spinning around.
Back to this picture of the
destiny of the universe,
so how does that work, 'cause I know
you all heard this on your mother's knee,
about the three kinds of big bangs,
and the universe is slowing down,
and mother's never lie, but
as you were falling asleep
your mother said, well,
if there's dark energy
the story's a little bit different.
And so here we have an
accelerating universe,
and so we don't know what it's destiny is.
It could continue to accelerate,
and then we have a cosmic red out
about 100 billion years from now.
It could re-collapse, the
dark energy could go away,
until we understand
what the dark energy is,
we can't say anything about
the destiny of the universe.
So we have this beautiful theory
built upon these three mysterious pillars,
dark matter, dark energy, and inflation.
And so here are the big questions today,
and I'm gonna get to the one
that I know you all wanna know.
So what is the dark matter particle,
or is that even the right question?
'Cause often we ask the wrong question.
What is the nature of the dark energy
and our cosmic destiny?
When did inflation took place?
And tell me more about
that scale of field.
And the ordinary matter,
how did that ordinary matter originate?
And then what happened
before the big bang?
Actually, there's even a bigger question,
which is more important to the
young people in the audience,
what will change the conversation next?
These are our questions,
these are not the ultimate questions.
There's gonna be some more
questions down the line.
So dark energy, my colleagues
accuse me of wandering around
talking about this being
the most important problem,
profound problem of all time,
and I went back and looked at that tape
of Katie Couric interviewing,
yeah now who was that?
Sarah Palin, and great minds think alike.
You betcha Katie, I
believe in dark energy,
we can see it from Alaska.
Now what I wish she could see from Alaska
is WFIRST, so this is the satellite
that NASA was on schedule
to launch in the early 2020s
that we heard a few weeks
ago might have been canceled,
but I don't think it's gonna be.
After this lecture, it can't be canceled.
Dark matter, so we got the
full court press on this,
so if it's a new particle,
can't we produce it at the LHC?
They're trying.
Our halo is full of these
particles, can't we detect them?
One of your own faculty
members Bernard Sadoulet
has spent the last 20 years of his life
trying to detect these particles,
and they're very shy, and you
have to go deep underground,
so they are currently in
an iron mined in Sudan,
so they're trying to detect
these dark matter particles.
My colleagues, this again is
the advertisement for Chicago,
if you wanna be a graduate student,
do you wanna go to Minnesota,
or do you wanna go to Italy?
And so my colleagues are using Xenon
in the Gran Sasso tunnel
to try to get the dark matter particles.
Before the big bang, is
everybody still with me here?
I'm gonna give you three ideas,
they're all wrong, but
that's not the point.
The question is now in play,
it's within the realm of science,
and I've selected these answers
to show you how clever nature is.
The answer to this question is
not gonna be someone sneezed.
So let's go ask Einstein.
So here's everything I told
you about the big bang,
the quark soup, the neutrons and protons,
structure formation,
and here's the big bang.
So what does Einstein say?
So Einstein says that the big
bang was a singular creation
of space, time, matter, and energy.
So there is no before the big bang.
Now that's pretty good,
that's neat and tidy,
but his theory is highly suspect
at this point in time, because
his theory has something
called a mathematical singularity,
and his theory doesn't
incorporate quantum mechanics,
so we don't think he got
the last word on gravity,
but the wonderful thing about science
is sometimes you can get the right answer
for the wrong reason.
So maybe the string
theorists are gonna save him.
So maybe this is such a nice idea,
the big bang is the
emergence of space and time.
Now don't look at me like that.
I have no idea what that means.
The emergence of space and time,
what would it mean?
Well Saint Augustine understood this
when he was asked, what did God do
before he created heaven and earth?
Do you know the answer he gave?
He created hell for those
who would ask that question.
But it's such a neat and tidy answer,
he said, "Well you
wouldn't want the creator
"sitting around forever
waiting to think about,
"so he created time at the same time".
I didn't wanna say it that way,
but you know what I meant.
So maybe he got the right
answer for the wrong reason.
So here's another one, so that's one way,
it could just be neat and tidy
that the big bang, there
is no before the big bang,
it was the creation of matter,
energy, space, and time.
So I told you about inflation.
Here's this little big bang wedge,
so you might have asked in that picture,
so you blew up a tiny
little bit of the universe,
what happened to the rest of the universe?
And that's called the multiverse
that there wasn't one beginning,
there were an infinite
number of beginnings,
so in this picture, this
is a Monet, quite valuable,
this is the cosmic river of time,
and so there is no beginning.
There were an infinite
number of beginnings,
so there was no beginning.
And so you all know about the multiverse,
and 'cause if you marry
this to string theory,
each one of these things
could be very different,
so they could have, here's ours,
here's one that has a
different number of dimensions,
that one was a dud,
and so the universe is infinitely
bigger than we thought.
Now would you bet against the universe
being smaller than we now know?
No.
So the dilemma of the multiverse,
and I know when I speak on the left coast,
I have to be very careful,
because the multiverse,
I have heard that it's been
proven on the west coast,
so the multiverse dilemma
is how can we test this,
because these different
pieces of the multiverse
are supposed to be incommunicado.
So this could be the most important idea
since Copernicus, but it's not testable,
so is it science?
And so I would suggest if you
think about the multiverse,
you either take aspirin,
or drink multiverse beer.
And so the last one, which
is completely different,
so you all know that in string theory
there's all these extra dimensions
that we don't know what to do with.
And so in string theory,
we're supposed to live
on a three dimensional brane
in an 11 dimensional space,
and so maybe these branes collide
and pass through one another,
and we're the bouncing universe
that bounces and bounces, and is cyclic.
So I have no idea if any of these ideas,
in fact I'm pretty sure
none of these are correct,
but this is now a question that
we can start thinking about
and the first step is asking questions,
and trying to test our ideas.
So let me finish by saying
the Oppenheimer Lecture
is where theorists get to gloat,
is that right Wick, we get to?
Good.
And theorists say that ideas matter,
and this idea of the deep connections
between the quarks and the cosmos
changed the conversation.
So the conversation used
to be about two numbers,
now it's about dark matter, dark energy,
and the unification of particles.
Thank you very much.
(audience applause)
- [Male Voice] So I think we may just have
some questions after that for Michael.
That works.
So I see a few of them, so let me start
with one in the back right there.
(man speaking off mic)
Microphone coming.
(quick footsteps)
- [Male Audience Member] I
wanna ask you this question.
At the very beginning of the lecture,
you said that the galaxies
were not expanding
in a preexisting space,
that space was expanding,
and the galaxies were just
floating along in space.
Now I wanna ask you this,
suppose Joe Blow comes along,
and he tells you BS!
Can you do an experiment to distinguish
and show that it's space expanding,
and not the galaxies blowing apart,
or the other way around?
What is the experiment to distinguish
between those two possibilities?
Even a Gedanken experiment.
- So I think the best
evidence that we have,
the best description
that we have of the data
is that space is expanding.
So the best description we have
is the theory that I gave you,
and it fits all the data,
but let me just give you one
thing that might convince you,
and that is that the light
from these distant galaxies
gets stretched as well.
So the light from these
very distant galaxies
gets redder and longer in wave length,
so everything is being
stretched with the expansion,
and so that's our best
description, it fits all the data.
And you're free to come up
with a better description,
but it has to fit all the
measurements that we've made.
- [Male Audience Member] What
measurement is that fitting,
by assuming that the galaxies
are expanding in a preexisting space?
- Well let's see, you
have to tell me more,
which is what do you do about gravity?
So how does gravity come into play?
- [Male Audience Member] The
way it came in in the 1930s.
- Let's see, 1930, well
1930 was general relativity,
so that's the story I just told you.
So one of the great triumphs,
one of the great things that came along
that Einstein introduced his
theory of general relativity
about the time that Hubble discovered
the universe was expanding,
is that Newton's theory of gravity
cannot describe the universe.
His theory of gravity is not good enough
to describe a big universe like ours.
- [Male Audience Member] Yes,
when these colliding branes,
so you're recycling
old universes that way,
and so can black holes survive
from one collision through
and be in the next universe?
- So I think the details
of the cyclic universe
are not good enough to give
you the answer to that.
One of the nice features,
not that the cyclic universe
is ready to be tested,
but one of the nice
things that people like
about the cyclic universe
is one of the tragedies of our universe
is that eventually the universe,
if it keeps expanding, gets very boring.
All the stars die out, all
the free energy goes away,
and it has a thermodynamic death.
And so one of the things
that people find attractive
about the cyclic universe is you get to
start things all over again.
But the details are not
worked out well enough
to make a prediction like
well can black holes
go through that bounce?
- [Male Audience Member]
Hey, thanks for the lecture.
I wanted to ask you how you feel
that according to Wikipedia,
you coined the term dark energy,
the ultimate sci-fi term,
which probably influenced physics a lot.
- Well Saul told part of the story,
and let me tell you the rest of the story.
So astronomers could not believe the magic
that the dark energy provided,
we didn't talk about
the universe being flat,
but one of the predictions of inflation
is that the universe should
be flat and uncurved,
and about the time Saul came along
with his discovery of the
accelerating universe,
we were running short by a factor of three
for the energy to make a flat universe,
and Saul's accelerating
universe solved that,
so that was terrific.
And so the astronomers said
we're done, it's Lambda,
and so had we allowed
them to call it Lambda,
then all we would do is measure
how much Lambda there is,
instead of asking the bigger question,
is it really just Lambda,
or is it something much more interesting?
And so part of the
reason to use dark energy
was to avoid people using
the cosmological constant,
to say no, we don't know
that it's the cosmological constant,
it could be something
much more interesting,
and let's measure the
properties more carefully.
Right over here, we have
the father of WFIRST,
he named it snap, he
doesn't even remember,
he's invented so many good things,
and snap was supposed to be the mission,
it's now become WFIRST to figure out
is this really just Lambda,
is it just quantum vacuum energy,
or is it something much more interesting,
and as that slide showed,
I go wandering around the hallways
thinking that dark energy
is really profound,
that it's a big mystery,
and it's not just as simple as Lambda.
Maybe it is, but if it's
as simple as Lambda,
but we have to be able to
calculate what the value is.
And so the purpose of giving it that name
was to say, look, this isn't just Lambda,
this is a much bigger puzzle,
thanks for asking the question.
- [Male Voice] We have some
other students who are waiting.
- [Male Audience Member] Hello.
So as a physics student, I
actually wanted to ask you
more of a philosophical question,
and that is, are you hiring?
(audience and Michael laughing)
- That was a good pitch.
We'd love to have you at Chicago,
you're an undergraduate?
Okay, you know my email.
Do you wanna be a cosmologist?
Did your heart go pitter patter?
Okay.
You had to much of Berkeley,
you're ready for Chicago?
Okay, good.
- [Male Voice] Any other students
who actually wanna stay here?
(audience laughing)
(garbled talking)
- [Male Audience Member] Hello.
Does quantum entanglement play a big part
of the theories about the big bang?
- Say it again.
- [Male Audience Member]
Does quantum entanglement
play any part in the
theories of the big bang?
- Not yet, but it could.
So let's see, boy, I thought
emergence was hard to say,
I'm just gonna say the words,
I don't understand them,
but some of the people
studying quantum entanglement
say that quantum entanglement
is what space time is,
that space time is made
of quantum entanglement.
That's all I'm gonna say,
I'm not gonna say any more about that,
but I will say a little
bit more about this,
that as I was telling
the students at lunch,
that when you're solving
really big problems,
like what is space time,
you need a crazy idea.
It's not gonna be, oh yeah,
space time is just a bunch
of letters and matches,
and stuff tied together,
it's just a lattice,
it's gonna be something that
at first glance seems crazy.
Now, 'cause I know you
can all find my email,
listen carefully, not every crazy idea
is the solution to a profound problem.
Most crazy ideas are
crazy, and so sorting out,
finding that one little
diamond in the rough.
But when you're looking at very very big,
I'll just give you an example
of general relativity.
Newton's theory had one teeny tiny flaw,
43 arc seconds in the procession
of the perihelion of Mercury.
His theory was there for 250 years,
this one little flaw, it
could be a measurement error,
who cares about Mercury?
It's not that interesting,
we don't live on Mercury.
And look at general relativity,
it couldn't be more different
than Newton's theory.
So Newton's theory talks about
the inverse square law of force,
so the new theory wasn't oh
it's not inverse square law,
it's one over R to the 2.1,
no, it's that space time is flexible.
And so these new ideas to
explain the big puzzles
look crazy at first blush,
and so when my colleagues
who are studying the
fundamentals of quantum mechanics
say that space time might be a construct
of quantum entanglement, who knows?
(man speaking off mic)
- [Male Audience Member]
You didn't mention
this particular question,
I don't know if you
consider it interesting,
but in this context the question arises,
why is there something
rather than nothing?
And is there any progress
on answering that question,
or in other words, the preponderance
of matter over antimatter,
or however you would couch that question.
- So the latter question,
let me answer the question,
it's the presidential news conference,
so I'll answer the second question,
'cause I can answer it.
So I didn't tell you about
the origin of ordinary matter,
and the big puzzle there
is what you alluded to,
is in this quark soup
there were equal amounts
of matter and antimatter,
and so why is there matter today at all?
It should have all annihilated.
And so one of the things that happened
during that quark soup phase,
is an excess of matter
over antimatter developed,
and not all the matter particles
had an antimatter particle
to annihilate with,
and so you're left with
a little bit of matter.
But the why there is
something rather than nothing,
I think you meant the bigger question,
why is there a universe
at all, why are we here?
- [Male Audience Member]
I was at the point
whether there was
progress in understanding
the preponderance of matter.
(garbled audio)
- Good.
I'm glad, let's forget the harder question
of why there's something
rather than nothing.
So we have a general framework for that,
that was that word baryogenesis,
and so it's related to a
discovery made by Jim Cronin
who was at the University of Chicago,
that's interesting.
He discovered that there
was a slight assymetry
in the laws of physics
for matter and antimatter,
and so we have a hint
as to how this works.
We now think it also involves neutrinos,
and so we're here because of
matter antimatter assymetry
in the laws of physics,
and because of neutrinos,
but the rest of the details,
we haven't worked out,
but that's how science
works, is you get a toehold,
you get a germ of an idea,
and so that used to be
something where we had to say,
well the universe has to start
with more matter than antimatter,
and now we can say no it evolves that,
but we don't know the details.
And so that's why I
didn't feature it here,
whereas dark matter, we think
we might be actually close
to discovering the dark matter particle.
- [Male Voice] So let's go over
just a couple more questions,
and there's one over here.
- [Female Audience Member] Hi, first off
thank you so much for the great lecture.
I think you mentioned that
you have some grad students
in Italy searching for
evidence of dark matter,
or something along those lines.
So what does it mean to
search for dark matter,
or really my question is deep down inside,
what do you think you're looking for
when you're trying to
describe dark matter?
- Good, so we think dark matter
is a new particle of nature,
and it's a particle of nature,
so what makes it different than atoms?
So the whole world that we know
is the world that interacts with light,
so atoms are made out
of charged particles,
and charged particles, you
must be a physics student,
so charged particles can
absorb light or give off light.
So the dark matter is not charged,
and that just makes it
really hard to detect.
I was gonna say see, but
that's sort of the same idea.
So these dark matter particles
can bump into a nucleus,
so that's what these
experiments are looking for.
These dark matter particles are very shy,
but occasionally they
will bump into a nucleus
and leave a little bit of energy,
and so now the goal is to detect
that little bit of energy,
and to be able to say
that little bit of energy
didn't come from some radioactive decay
in the detector or a cosmic ray.
And so that's why the
experiments are deep underground,
and so these dark matter particles,
you've heard of the neutrino,
so neutrinos are very shy,
and they're not charged,
but we can detect them.
And so the hope is that we
can detect these particles,
that they're just regular old particles,
but they're not charged.
And it would be great
to solve that puzzle,
'cause this story is so good,
but it's not about the best story,
so I hate to say this in a talk
where we're glorifying theorists,
but beautiful theories are killed
by ugly experimental facts,
and so at the end of the day,
even though the theorists are smarter,
more brilliant, better looking.
Did you hear the late laughter there,
so that's the experimentalists,
they're a little slower.
(audience laughing)
They get the final word,
they get the final word,
'cause it's not about how
beautiful the theory is,
it's about does it agree with the facts,
and so you've actually, although ideas,
I can't let go of this,
ideas drive the field.
But at the end of the day,
the experimenters get the final word.
- [Male Voice] I won't
take the final word yet,
but I want to go for at least
one or two more students if I could.
We have a student, okay.
- [Male Audience Member]
Hi, I know you didn't wanna
talk too much about the big fancy tools
that are being used, but I was wondering
if you could expand a little
bit on what could be measured
that isn't being measured,
and what could be measured
that isn't being measured could mean
for answering any of this?
- Oh, so what's my wish list
on things to be measured?
- [Male Audience Member] Sure.
- Well, so number one on the wish list
is that beautiful satellite flying over,
actually I don't think
that's the orbit you wanted,
would it go over Alaska?
I don't know.
(man speaking off mic)
No, it goes out to L2.
So WFIRST is the mission
that we'd really like
to better understand what's going on
with the acceleration of the universe.
So we want WFIRST, so that's
$2 billion, or is it $3?
Well, if you have to
ask you can't afford it.
So dark matter, so I feel like
we're really close on the dark matter,
and so I'd like more
dark matter experiments.
So the range of the dark matter
space that we can explore,
we've got one more good go.
If we build detectors that aren't one ton,
but are more like ten tons.
So we wanna do that.
That's next on my wish list,
and you got your checkbook out?
Yeah, I think those are only $200 million,
so you could do a couple of those.
Let's see, what else would we like?
I want a surprise, that's
what I would really like.
I think that's what we're
really missing is a surprise.
So we're going along,
everything fits too well,
we want a big surprise, we want something
that's completely unexpected.
So can you build an instrument
that will provide that?
(audience laughing)
- [Male Audience Member] I got you.
- That would be priceless.
In science we like surprises,
because we get to the point
where we think we have nature cornered.
It's dark matter, it's dark energy,
but that may not be where it is.
We need a surprise to jar us a little bit.
Saul jarred us a little bit
with finding that the
universe was speeding up
and not slowing down.
We need another one of those.
- [Male Voice] Last question,
and I saw there was still a student
that was waiting in the back.
- So you said that you felt
the last three theories
that you presented on
your slides were wrong,
I wanted to know what do you think
the beginning of the universe was,
and should we even keep
looking at these theories
if we can't test them, or
should we start completely fresh
with a brand new experiment,
and see what where we get from there?
- Were you asking me
the multiverse question?
Was that it?
We call it the M question.
So first of all, you
should not listen to advice
from anyone like me.
That would be a very bad thing to do.
And I'm really just giving you
the dilemma on the multiverse,
and I should've phrased it
a little bit more carefully,
so our best understanding is that these
different pieces of the
universe are incommunicado,
and if that would be true,
boy that's a tough one,
how would you ever test that?
But how do you know they're
really incommunicado?
So don't take my word for it,
so maybe we don't understand
the multiverse theory well enough.
So maybe there is some way to test it,
and it's really high stakes.
I say this, some of my friends know
that I'm not the biggest
fan of the multiverse,
but I say, honestly it could be
the most important idea since Copernicus,
but it's really a dilemma,
because I don't know if it's testable.
The science brand is, it's
not how we want it to be,
it's how it is.
That's what science is all about.
And so I think it's great that people
are studying the multiverse
on the left coast,
I think that's good,
and in the third coast
we don't have to study it,
and so we have a portfolio,
we don't want everyone
doing the same thing,
so you have to make your own decision,
but it's really high
stakes, and when I got in,
when I came to Chicago, my
mentor Dave Schramm said,
"You know, I think there's something
"in bringing together the
very big and the very small",
and my PhD advisor, who was a great guy,
said, "I wouldn't do that,
I think that's too risky,
"you oughta do something
like gravity waves".
Well that turned out to
be pretty good advice,
but I would've had to wait slightly longer
for something to come home.
My advice to young people
is it has to sing for you,
it has to sing for you,
it has to be something
that you're willing to
be passionate about,
I mean look at Saul here,
so he worked so hard
to make this measurement
when people were selling,
this is a dumb thing to
do, it'll never work.
And he had a passion about doing that,
and passion doesn't guarantee
that it's gonna come true,
but that's what science is all about,
is pursuing an idea that
you think is important,
and that you enjoy working on.
And so maybe you'll be
the one who figures out
how you test the multiverse.
Thank you very much.
(audience applause)
(upbeat music)
