I had the pleasure of interviewing cosmologist Brian Keating recently. He and i have a bit of a
kinship because we're both youtubers who admire each other's work, and we both love to ask the
big questions about life and the mysteries of the universe. But brian is eminently more qualified than me
on this subject. He's a distinguished professor of physics at the University of California, San Diego
He's the author of two books, and host of a popular science podcast. Check out and subscribe to his
youtube channel at the link in the description. He's done some fascinating interviews with some
very prominent scientists. So i think you're really going to enjoy his channel. You'll find links to
his books and podcasts as well. Now, having done several videos on the cosmic microwave background
or the CMB, i was really interested in talking to Brian because that's his area of specialty,
more specifically, the polarization of the CMB. Now, Brian is going to describe
what this is in this interview, but i think what's absolutely fascinating is the idea that
by studying this aspect of the cmb, we may be able to detect gravitational waves from the time of the
big bang. This could inform us about the earliest history of our universe and shed some light on
some deep mysteries. Now stay tuned to the end because Brian has a special offer that he wants to
make to Arvin Ash viewers. I have to admit an embarrassment. I don't do many interviews so i made
the amateur mistake of not recording my own camera. So you won't see my face on this interview, but
brian's dialogue is much more interesting anyway. So now i give you Brian Keating
I study the cosmic microwave background radiation which is the oldest fossil heat
left over from the big bang. And it traces the composition, the properties, the evolution
and perhaps the origin of the universe could be revealed in it i like to think of it as kind of -
remember those old-fashioned films you used to take to the to the drugstore and you'd have
them exposed and and so forth. So the the CMB is actually like a type of film onto which we hope
to expose waves of gravity if indeed the universe began with an inflationary epoch, as I know
you've talked about in the channel many times. So it's really a detector and it's a signal.
So it's kind of unique in that way, and so i find it fascinating. I think it's
the most interesting thing you can study, but I'm kind of biased. It's been my whole career.
Yeah, so polarization is the unique interaction between light and matter that can be traced to
determine either the properties of the light, or the properties of the matter. So if you've ever
used polarized sunglasses, you know that they suppress one of the two linear polarization
states of light. Ao light is a transverse wave. It means it oscillates up and down as it progresses
in a direction from the source to the observer. And when it interacts with matter it can get
some of the imprint of the light source can be changed by the properties of the matter -
either what it's made of, or how its dynamics are behaving. Ao in the case of the cosmic microwave
background we have this early universe as a fusion reactor, as a as a soup of primordial plasma. And if
there were waves of gravity in it, the photons that are in the plasma as they interact with
the matter and bounce around, they will inherit some of the properties of the underlying spacetime
in which the matter is contained. Ao it's kind of a diagnostic. The polarization uniquely
allows us to see the imprint of the, perhaps the impact of these waves of gravity.
And what's so exciting is we know since 2015 that waves of gravity exist thanks to LIGO, and
LIGO measures objects at billions of light years distance, billions of years ago. We're trying to
measure 13 billion years, 13.8 billion years ago, when the first matter really came into existence.
So it's a lot more challenging to do, and as far as we know this is the only way to use the technology
that's available in the foreseeable future. We can only detect these waves of gravity,
using this CMB itself. And the waves of gravity will only be there if inflation took place. There
are no other models that predict, robustly so, a background of waves of gravity in the
early universe, in other words, a cosmological background. The black holes that LIGO detects,
those waves, those are astrophysical sources. Those are not cosmological. Those are not coming from the
big bang, or from the origin of the universe. They're very interesting. They're exquisitely
beautiful laboratories for learning about gravity. We want to learn about the universe using
those waves of gravity as our tool. There will be CMB polarization, but there won't be this type that
reveals the presence of gravitational waves. That will be absent in all models except for inflation
So inflation has a lot of circumstantial evidence for it. It has a very good ability to reproduce
some of the most, kind of baffling aspects of cosmology. There're many pieces of evidence
for inflation that are supportive of it. It hasn't been ruled out. It could have failed
certain tests already. It hasn't. For example, we call the we say the universe as flat,
meaning that any three points in the universe, no matter how far away they are,
that comprise a triangle, the interior angles inside that triangle will add up
to 180 degrees, just like they did for Euclid on a piece of paper, you know, 2400 years ago.
So dark matter really can fall into two different categories. It could be a new form
of matter completely unlike the baryonic matter that we're made up of, the ordinary matter that
we're made up of. It could also be a modification of our understanding of gravity.
Those are the two main classifications of what potentially could be happening. We actually know
of one form of dark matter. I have a video on my channel about this - like dark matter has already
been detected, because there is a form of matter that has mass that is abundant in the universe,
and doesn't interact with matter, and doesn't produce or generate or interact with light.
And those are called neutrinos. There's actually trillions of them going through each one of us
right now. And the neutrinos have really, some call them the most interesting particles
of all the elementary particles. They don't decay, but they oscillate, and they change their
flavors, from one kind to another kind. As they travel, they behave differently in highly dense
media. They're participating in radioactive decay but they don't interact with light
and they have very very very very very tiny masses. A video out about the first laboratory measurement
to get to below what's called one electron volt of energy. I know your viewers know are very
conversant with it, i think because you always talk about what is an electron volt. So an electron
itself has an a mass according to E = m c^2 , a 511,000 electron volts. The neutrino
mass measured by the Katrin experiment in Germany has to be lower than one electron volt.
It can't be any bigger than that or they would have seen it. It's called an upper limit. We also
have, from neutrino oscillation experiments, we know there's a lower limit. The neutrinos can't be
smaller than a certain mass limit. Well that mass limit is 15 one thousandths (0.015 ev) of an electron volt. So
the electron, which is the lightest of the common elementary particles, is millions or maybe billions
of times heavier than these neutrinos, and yet we don't know their exact mass. So that's a form of
dark matter of a material kind. Turns out that's not sufficient to account for the observed amount
of dark matter there is. We don't know what it is, but we know how much of it there is, if it's matter,
if it's in the form of these types of particles. So there are many many projects currently undergoing
measurements now to look for what are called Weakly Interacting Massive Particles, or WIMPs.
Now, we've ruled out in the last two decades, we've ruled out primordial black holes as
being a type of dark matter that account for how much we see. We see about five times more
dark matter than ordinary matter like protons neutrons, or my favorite particle the "crouton."
It's the only particle you can eat! Those particles are outnumbered five to one by
dark matter. And then dark matter and matter are outweighed by about two to one by dark energy,
which we know absolutely nothing about. So there are many people including our cosmic microwave
background experiment the Simons observatory that are looking for both ordinary neutrinos and trying
to get their masses cosmologically. And we're also looking for exotic particles called axions,
which are kind of like heavy photons, but they're not photons. They don't interact with light,
so i would say those are conjectured by physicists here in California. And
Frank Wilczek has made a lot of good contributions to that, as well Peccai-Quinn
were the original, two kind of founders of this. Ao this axion is a good candidate.
And then on the changing gravity, there's a whole other theory called MOND - Modified
Newtonian Dynamics, which says that in galactic scales you can't even use Newton's laws. You have
to modify those, and the laws of relativity that recapitulate those, need to be modified as well.
And we just don't know right now. There's a lot of evidence. And i would say most of my colleagues
believe that MOND is incorrect, because it can't account for several things like these colliding
galaxies behind my shoulder over there, the two galaxies in the whirlpool. There's certain
galaxies called the bullet cluster - it can't account for how they're interacting appropriately.
But then other supporters of MOND will point out, well, the ordinary model can't predict for
the high velocities that these two galaxies are merging. So it's a very interesting and open
question. And i think the most dangerous words are, you know, "what's your favorite, you know, choice?"
It's it's really hard to say. I mean, I mean the best thing to do is that, i mean it's
actually a good thing, because that means that there's multiple angles of experimentation that
my team and i can look for to explore this. So we can see neutrinos which would be the kind of
matter particles, but we could also potentially detect violations of relativity as well.
And actually, you know, no one would be happier than than someone like me if we discover that
Relativity is wrong on cluster scales, or you know, intergalactic scales, because that is just
incredibly fascinating. And all of modern physics is underpinned by aspects of
Relativity or what's called Lorentz invariants. And so there's a lot more speculation that
that could be had. And again, my job like where i get my most, where's my happy place? You know, where
do i get enjoyment? It's from, it's from like making or getting a number, a data point that's the result
of years perhaps of building hardware and blood, sweat and tears, by me and my students and my team,
and then getting this number and then saying well, this now tells us something we never knew about
the universe, and tells us how we were wrong, and what we used to think. So I can't take sides.
Either one would be really interesting - right, I mean either some new particle that
is like maybe there's a dark periodic table, maybe there's this shadow world of
non-existent - Supersymmetry Maybe? Maybe yeah, it could be supersymmetry, or you know maybe there's a
modification that Einstein was wrong, yet again! You know he had like you know seven pretty big
blunders in his life. And and again he ended up you know with tenure so that's okay in
my book! but uh you know he could be wrong! He was a nobody! yeah yeah he wasn't a nobody.
Yeah, I'm kind of a contrarian about it. I don't believe there's life in the universe. So i did
an interview with Lee Cronin. I've done interviews about aliens with some of the biggest proponents
of aliens. I believe right now if you just weigh the evidence, that's insufficient to say
the capacity for life is overwhelmingly this positive that there is life, and i give the example
of Antarctica where i've been twice. Antarctica is one-seventh of all the continents on Earth. It's,
in terms of total land mass, it's even larger in some sense. We didn't know about Antarctica for, you
know, thousands of years, discovered it. There's like no life there. But if you just purely said life
depends on how much available face space there is for - and life can exist are there's birds and
fauna and stuff, but it doesn't it really doesn't exist. There's no intelligent life etc. Again it's
not based on what i believe, like i have a video on my channel, "I don't believe in gravity" it's called.
I have evidence for gravity. You don't need to believe until you evidence. We have no
evidence for life in the universe. And we actually have evidence through what's called panspermia,
that meteorites travel through our our solar system, and there's no evidence for life from earth
on mars, even though there's meteorites on mars from earth. So life is very, it's very touchy.
It's very difficult. I'm not arguing, you know, god this that. I just think the probability of
it is very low. Certainly for technological life. the bar is so much higher. So imagine you say there's
10 different things that needed to happen to have life on earth so that you and i could
have this conversation. The universe has to form. Solar system has to form. And then you
have to go from hydrogen and carbon and silicon, and eventually have to get DNA and everything.
Then you have to survive this late heavy bombardment - the earth was pummeled. Then you
have to have dinosaurs that are roaming around. And then dinosaurs have to be killed off. Then you
have to have enough, you know, biotic matter to make oil to make semiconductors, to make the
transistors that make the computer that you and i are talking. Again i'm never gonna say there's
no life. I'm just saying there's no evidence for life. And I'm not sanguine that we're
gonna rapidly find evidence for life. In other words, the hype surrounding the existence of not
only - remember what's being claimed is that we're visited by alien technology - my friend Avi Loeb and
others you know. So again i skipped ahead to that, but to get there say there's 10 things that
have to happen, even for for slime mold. You know, if you find slime mold on, you know, Proxima Centauri B,
the different hurdles that that planet would have to sustain to get to that point -
let's say there's ten of them. and let's say each one has a has a probability of one in a thousand.
Ao you know, that means you have a one in 10 to the tenth chance of life happening on that particular
planet. That's about 10 billion to one! Now, i think there's a lot more than that. You know,
you need to have RNA. maybe do you need DNA first? How does all this stuff come together?
How do you have enough nutrients? How does it survive - all these different things for there
to survive to be there. And again as i said - I don't know if you remember in 1996 there was
a press conference held on the White House lawn. It's actually featured in the movie "Contact," which
is written by Carl Sagan, and one of my guests Ann Druyan, his widow. And that's a real video.
President Bill Clinton is saying we've discovered this amazing signs that scientists say could be -
like that was peer-reviewed, accepted had to do with meteorites found on Antarctica's continental
shelf, that originated from Mars. And there was a Martian meteorite that had allegedly byproducts of
respiration. Arvin do you know that that's never been retracted? That paper. the conclusion have
never been retracted. It's never been confirmed. And so you have this thing standing out there for the
last 30 years almost, that was never confirmed. And it's like people think of it as the most important
thing in human history. If it were true, in other words, we're always looking to the future - oh
we'll find life next week, next month, next year. But we already have this thing - and
you know, yes the average human being, they don't know anything about it. And all i'm saying is that
the conditions in which life originates ab initio, are exquisitely well tuned.
And some of them were done by people that used to be at UC San Diego, Miller and Urey,
and their famous chemistry early earth chemistry experiment. There's been very little progress in
that front, and there's a lot of kind of talk about things like extremophiles and other
types of life, and even people like, you know, Max Tegmark and others talking about digital life.
Like we're not even going to have - forget about like slime mold. There's gonna be like artificial intelligence
is the preponderance of the universe, or even as one of my guests David Chalmers said, we're
in a simulation. So you see the the goal posts shifting, which to me as a scientist tells me
the bedrock foundation may not be that stable. I really appreciate this time you spent with me.
You've done some fascinating work. Your book look fascinating. So i'm excited to finish
this video and put it up on my channel. Awesome, i can't wait. Thank you so much Arvin it's been
a pleasure. And thank you for mentoring me and i know there's many like me that really,
i love your videos and you're the one that people always say - I know, I know i did a good job
when somebody on the channel in the comments says, "oh this reminds me of Arvin Ash."
Oh really? Okay. Thank you my friend. appreciate it. Take care. Bye. Tanks Arvin. That was
a big bang blast for me, and i hope for your viewers too. And a special offer for your viewers
in the United States of America - and that's you can get your own piece of the villain of my book,
"Losing the Nobel Prize" - that's right cosmic space dust, space schmutz, the fragments of an ancient 4.5
billion year old meteorite that fell in Argentina some 5000 years ago. I've collected samples
of this ginormous piece of space schmutz, and I will send you a tiny little fragment of your own,
if you join my mailing list, which you can reach at briankeating.com/ash