Into the Impossible With Brian Keating - Marc Kamionkowski: Crises In Cosmology (#312)

Episode Date: April 23, 2023

Watch the video of this episode here:  https://youtu.be/RVLMnBsJgKI?=sub_confirmation=1 Marc Kamionkowski is a theoretical physicist, who’s research is in cosmology, astrophysics, and elementary-particle theory. His main focus has been on particle dark matter, inflation the cosmic microwave background, and cosmic acceleration. His 1999 paper, A Polarization Pursuer’s Guide inspired Professor Keating to create the BICEP experiment. He is the William R. Kenan, Jr. Professor of Physics at Johns Hopkins University. 00:00:00 intro 00:04:39 The BICEP 2 Press Conference St. Patrick’s Day 2014 and how Professor Kamionkowski inspired the BICEP collaboration and the story of the well known cosmology paper: A Polarization Pursuers' Guide, 1999 ( https://arxiv.org/abs/astro-ph/9909281 ), the inspiration for BICEP.  00:06:58 Did you realized the implications of your paper for telescope design at the time? Marks’s proposition to measure the amplitude of primordial gravitational waves, even with a small aperture telescope. The origins of BICEP and the Simons Observatory. 00:15:40 Optical surveys are still a cornerstone of observational cosmology like weak gravitational lensing and comparisons to E/ B mode curl components measurements. 00:28:50 Is a theory of everything possible? Are physicists “lost in math”? What to you think make good mathematical models? Little attention has been given to alternatives to symmetries in string / super-symmetry theories which have not been productive? Behold the examples of Bohr and Balmer’s formula and the breakthroughs of the 20th century. The luck of 20th Century Physics. The price tags and time scales are much bigger now. Don’t abandon the notion of symmetry!  00:34:53 The cosmological principle; should it go away? What would you do if it did? All models are approximations. We have good descriptions. 00:41:00 The social contagion of Eric Lerner and the controversy over the refutation of the Big Bang Theory. https://iai.tv/articles/the-big-bang-didnt-happen-auid-2215 Does it make you re-evaluate the standard model of the Universe? 00:45:5l0 About the Hubble Tension. What is it? Why worry? Or not! 00:56:00 Professor Kamionkowski’s explanation of early Dark Energy and his 2018 paper. 00:59:10 Anti-helium and anti-matter clouds 01:01:10 What theoretical physics “crisis” or anomalies should we most focus on? How do you choose? Let’s not all focus on the same problems! What about the cosmic optical background found by the New Horizons Long Range Reconnaissance Imager? 01:10:35 Is there an Axion Persurer’s Guide to be written? 01:12:00 What is the status of the theory of Inflation and where will it go? A field Marc helped initiate. 01:17:50 First existential question: What would you put on your monolith? 01:21:20 What have you changed you mind about? Subscribe to the Jordan Harbinger Show for amazing content from Apple’s best podcast of 2018! https://www.jordanharbinger.com/podcasts  Please leave a rating and review: On Apple devices, click here, https://apple.co/39UaHlB On Spotify it’s here: https://spoti.fi/3vpfXok On Audible it’s here https://tinyurl.com/wtpvej9v  Find other ways to rate here: https://briankeating.com/podcast Support the podcast on Patreon https://www.patreon.com/drbriankeating  or become a Member on YouTube- https://www.youtube.com/channel/UCmXH_moPhfkqCk6S3b9RWuw/join To advertise with us, contact [e-mail] Learn more about your ad choices. Visit megaphone.fm/adchoices

You know, ultimately what we do is physicists, as scientists, is construct mathematical models to explain results of experiments and observation. But you want that mathematical model to be mathematically self-consistent, and you also want to satisfy certain basic requirements. And the basic requirements, you know, are consisting with the symmetries that are either assumed or observed. And throughout the 20th century, we were lucky. We were able to very rapidly uncover, you know, a variety of layers. We had a lot of experimental data that guided us and told us what the cemeteries were. You look at the data, and there are the patterns. Welcome everyone to this cosmological episode of Into the Impossible with theoretical physicist Mark Kamiankowski.

This episode gets personal. You'll learn how Professor Kamankowski's insightful work inspired your host, Brian Keating, to embark on his scientific quest to reveal the secrets of the Big Bang, including cosmic inflation and the measuring of the primordial gravitational wave. A story told by Brian in his book, losing the Nobel Prize. It's a journey that began with the Bicep experiment in Antarctica and is unfolding even now with the completion of the Simon's Observatory in Chile. Has the quest for a symmetrical unified theory gone too far?

What are the next frontiers in cosmology? Stay tuned to find out. Please keep into the impossible in your feed by subscribing and following. For some extra credit, jump over to our YouTube channel at Dr. Brian Keating, that's DR. Brian Keating, and subscribe there too, where we just broke the 100,000 subscriber milestone. And let us know what you think of the show in the form of a review like this one. from Jonathan Millis. One of the most fascinating science podcast out there.

What sets it apart is the way it tackles some of the most complex and cutting-edge topics in science without dumping them down for a popular audience. And now, let's grapple with some of the biggest questions in physics in this cosmology episode of Into the Impossible with Mark Kamankowski and your host, Brian Keating. Any sufficiently advanced technology is indistinguishable from magic. Open the five-bay doors, please help. Welcome everybody to another exciting, titillate into the impossible adventure with one of my longest-term friends.

I can't call him an old friend. He's barely older than me. But he has been a mentor and inspiration and really set the tone for the field for many, many decades now, unbelievably. And that is Professor Mark Kamienkowski, who is the third guest, who is a professor at Johns Hopkins University. after Adam Reese and recently Sean Carroll. And maybe, well, I don't know. You don't consider Mario Livio to still be there, right? He's no longer affiliated in any way, is he?

I think he's retired from Space Telescope. Yeah. So the Baltimore District, yeah. So it is Mark Haminkowski, renowned cosmologist and theorist. And really, the reason that I'm probably having this podcast, if it wasn't for him, I'll get into that in just a minute.

Mark, how are you doing today in good old Baltimore? Pretty good. It's like in the 60s here, which for us is a very big deal. Yeah. Yeah, it's a nice day. Good day for a crab cake luncheon out there. Yeah, I'm suffering through 57 degrees here in San Diego. So a rare day when it's warmer in February out there than it is here. So today we're going to talk, this episode is tentatively titled, Mark, I should have told you beforehand, does cosmology need a therapist?

And it's because of all these tensions, anxieties, crises that cosmology is allegedly suffering from. But before we go into that one, which will be the substance of this conversation, I wanted to just bring my readers on an adventure. As you may know, if you've listened to the podcast before, seen it before, I always start off with authors. And I ask them to judge books by their covers, which is you're never supposed to do that, but what else do you have to go on? So we're going to judge this book, Mark. It's called Losing the Nobel Prize.

You may have heard of it. There are many chapters dedicated to Mark Kaminkowski. But I talk about the time in 1999, before I met you, I knew of you, but you were still at Columbia at the time, and I was destined to meet you when you became a professor at Caltech and follow your career ever since. And in this particular vignette, I'm describing how I spoke to you the day before the famous Bicep Two press conference, which occurred. now it's going to be what nine years ago.

10. Oh, yeah, nine years ago. On St. Patrick's Day, 2014, where Mark was at the famous press conference, and I was not, and I remember you telling me on the phone that there'll be other press conferences for you, Brian. But actually, the time I want to go back to in the book is when I first encountered you. And really, the reason that you were there at that press conference, perhaps, is because you really inspired the Bicep series. of experiments, indirectly or directly, via a paper you wrote with a good friend of mine, as well as collaborator, Andrew Jaffe, and Lemon Wang.

Was he your grad student? Lehman was a postdoc. He was great. Yeah. I mean, he was a spectacular scientist. He was one of the adventures of contestants when he's a grad student, the University of Pennsylvania. He came, we got him at Columbia because he had family reasons to want to be in New York City. Mm-hmm.

and we wrote that paper, we wrote several others that people still read and pay attention to. He was great, but then the reasons that he had to come to New York City for a postdoc were also reasons he wanted to remain in New York City. And it's not easy to like navigate an academic career when you're limiting yourself to one small, tiny little town. Yeah, New York has its charms. A lot of people have really, have really. located from New York City, but we're not going to get into those details now. I want to discuss the paper that you guys wrote together, which was called the Polarization Pursuers Guide, or PPG.

And for me, it became another version of an inspiring manuscript like the version of Jay Passacoff to late grade. Unfortunately, Jay passed away just a couple of months ago. He wrote the field guide to the Stars and Planets with Donald Menzel at Harvard. is one of his advisors. And that book inspired me when I was 12 years old to get my first refracting telescope and become an astronomer of some renown trying to follow in Galileo's footsteps.

By the way, today's Galileo's birthday, February 15th, we're recording this. Happy birthday, 486 years old. He looks great. He looks great. But anyway, this paper that you wrote inspired me. And the reason it was is because it was the first time I or anybody else really heard,

an inkling that one could measure the B-mod polarization of the C&B and do it experimentally. And the extrapolation, which I drew from the paper, was that you presented a series of graphs, and we'll show those in the B-roll here. But you presented a series of diagrams, and those diagrams presented how well could a given-sized aperture telescope constrain the amount of inflationary gravitational wave energy or the amplitude of primordial gravitational lines. And I saw that it was almost independent of aperture size. And that really lit my fire because, as many people may or may not know,

a telescope's cost scales basically with the cube of its diameter, some high power of the aperture. So you were basically telling me at that time, and anyone else who would listen, that a 10-meter diameter telescope was not necessary to detect the primordial gravitational wave background. and that really inspired me and I stopped working on the projects

I was working on for Sarah Church and she promptly fired me which then brought me down to work with your friend and my mentor, Andrew Land. So you were Stanford before? Yeah, I was at Stanford in 99, miserable, hated working on living in Palo Alto on a postdoc salary of $32,000 during the dot-com

boom when Google was getting founded down the street. I had no money, no prospects, really wasn't interested in the science that, you know, Sarah had, you know, she did nothing wrong, but I was so distracted by some of the ideas that I'd read about in your paper and others and really became infatuated that I wanted to do this and I wanted to study the B mode polarization on the microbecker. And that later became the impetus for the bicep experiment. So bicep, we can have, actually here is a replica of the bicep lens that we use, the primary aperture lens for one of the bicep prototypes that we built back at Caltech where I was a postdoc and you were a professor.

And this telescope was very cheap. I mean, we got started with a $1 million grant from President David Baltimore. I think that was one of the nimble features of a small institution like Caltech. In addition to teaching people how to weld and do technical college things, Caltech's very nimble. I don't know if UCSD or Johns Hopkins is like that. But at any rate, that paper inspired me. to go on this adventure. And since then, we've had four generations of BISA, and now we're in the third generation of the Simon's Array and Polar Bear. And it's very similar. It's on a refracting

telescope. But at your university co-member colleagues class and then, of course, Simon's Observatory, which I lead with my friends at Berkeley and Princeton and UPenn and Chicago. So anyway, Mark, I want to thank you for that, but bring us back to that time. Did you realize the implications when you guys are working on this paper, were you mainly trying to motivate why it would be interesting or how one could study it? Or did you really want to parse the differences between a large expensive telescope

and a small, relatively inexpensive telescope? I think that what happened there, if I remember, is that there was sort of this mindset at the time. you know the you know the big C&B experiment at that time

the most successful one was Kobe and you know we all knew Kobe we understood how it worked we had looked on the analysis worked and you know I was a grad sorry a post hoc

in the mid 90, early 90s and I started getting interested in the C&B and I started to work on the CNB I went through a whole bunch of calculations I gave myself exercises. So I could sort of understand what's going on. And, you know, Kobe worked by scanning the entire sky. And we sort of had this mindset that a cosmic microwave background experiment to be successful

had to scan the entire sky. And it turns out that Kobe was the best strategy, that full sky strategy, was the best strategy for the signal that they were trying to detect, which the temperature fluctuations. And if you look at the power spectrum for CNB temperature fluctuations, it peaks at large angular scales, and the fluctuations get become much smaller

amplitude at small angular scales. And so, you know, I wasn't around when they designed Kobe, but in retrospect, that was the best way to actually discover what they wanted and ultimately discovered. But then, you know, in the mid-90s, I and Arthur,

and Albert Stevin's and Uroche and Matias and other people were writing papers about the polarization. And one of the things that was striking about the polarization is that the fluctuations in the polarization are larger on small-angler scales than on large angular scales. And so we did a straightforward calculation of the paper that you're thinking about, which was essentially just a generalization of like

the kinds of exercises that I and other people had given ourselves, you know, to learn about how these measurements are done. but it was pretty clear just looking at the polarization power spectrum that since it peaks at smaller angular scales, you don't need the full sky and you don't need

it also not all peaks on smaller angular scales, sort of peaks at middling angular scales. They also didn't need, you know, the extremely high angular resolution that we were pushing for in our efforts to like, you know, advocate for experiments like WMAP to measure

to measure cosmological parameters. So it was a pretty straightforward exercise. The conclusions in that paper probably could have been reached just by looking at the polarization power spectrum without actually any detailed calculation. But I think putting in that, the intent of putting in that paper was to draw attention to this. As you know, I'm not an observer.

I was even less of an observer back then, but I did know enough to know that you don't need a big telescope to do, you don't need particularly good angle resolution. and I also know enough that it's easier a point of telescope or small part of sky than the entire sky. I think that we took the title with that paper from a book that had been written called The Higgs Hunter's Guide by a four article theorist.

Gunnion, Haver, Sally Dawson, and I'm going to get in trouble with Kane. Yeah, I think it was Gordy. Yeah, I have that's one of those books you buy and you never read. But because I thought it was slightly more practical to build something to look for gravitational waves, you know, on a tabletop size, then look for the Higgs. But we'll get to the Higgs and we'll get to other challenges and crises in cosmology. Just a quick pause to ask you for a small favor while my thumb is occupied with old Albert on it, yours is presumably freed up to leave a thumbs up on this video. It really helps me a lot with a good old-fashioned YouTube algorithm.

But now back to the video. But I guess the question I had is, you know, back then you were also responsible for the formalism, which I think is both more poetic. I fight with Matthias about this all the time. You know, EB versus grad curl, I think it's more evocative, more descriptive to use the description you and Arthur. And Stevens came up with. But the kind of milieu, if I remember from middle of my graduate school in the mid-90s, late 90s, that was also concomitant with looking for, you know, cosmic shear or looking for galaxy

shear and correlations, which I want to ask you about that because I don't really hear so much about, I mean, we hear about gravitational lensing and even in the CMB, but these were in like kind of optical surveys, if I recall correctly, where you first really, and maybe it was Stebbins, you know, who had with Nick Kaiser, if I recall correctly and others, that really started to look into these, you know, grad curl type phenomena. But in contradistinction to the CMB, I almost never hear about those types of measurements. What happened there? Did we just solve that field or did it get superseded in some way?

You mean, weak lensing of galaxies? Yeah, just optical, you know, surveys of weak lensing. And in the formalism of Brad Carl, you know, presenting it in that way. People do that. It's huge. It's one of the cornerstones of, you know, the DES dark energy survey analyses, cosmological analyses, that galaxy clustering. They got barium acoustic oscillations,

but they also have weak lensing. So that's huge. Are they using the gradual formalism? Or are they, like, what is the kind of metric or rubric that they're using? Because I remember back then it was all G's, you know, grab and curl. So they're looking for, they're using weak lensing to measure the mass distribution.

And for them, it's just the grad or the e-mode. They don't really need the curl. there's no reason they don't really need the curl for anything or the B mode. You can use it, you can measure it with the experiment, and I think they do is a null test. It's a very good null test because it's the, you know, the whole analysis pipeline that you develop to measure the E modes. You can just change essentially one line to code, just rotate everything by 45 degrees and then do the same measurement that gives you the B mode or the curl component. and if you're doing everything right, that should be zero. Right.

So it's an important thing. Yeah. So they do, they use it, but they don't use the language of E versus B because it's not really, they just have glensing. Now, that's tracing matter distribution. I mean, what to what does that owe itself too? Is it too dark matter at low Z? Because obviously, you know, Plank and other C and B act and SPT and so forth. and polar bear can measure, you know, gravitational lensing at high redshift and trace things

along the line of sight and there's a redshift kernel that is involved. But what is the, if you had to rank kind of the DES and other surveys, you know, kind of motive force or motivation for them, I mean, what, to what extent does weak lensing, you know, hold a candle, no pun intended to things like barren acoustic oscillations and other phenomena? I think it's right up there. I mean, it's not better or worse. it's different. If you look, there's been a lot of attention

to this Sigma-8 tension in recent years. And you can look at the papers, or you can look at the summary plots that people show in conferences, and there's a whole bunch of different data points, measurements of this amplitude of clustering in the current universe.

And some of those come from weak lensing, some of them come from galaxy clustering. And they're all falling more less in this a little bit low compared to what you'd expect from the CMB and they all have comparable air bars. So, yeah, weak lensing of galaxies is, I think, right in there. It's one of the cornerstone, you know, physical cosmology measurements that people are doing that.

So we've had a lot of guest on recently talking about alternatives to things like inflation, to things like Lorentz invariance as a, as a, you know, conserved symmetry. We'll get to those. but the one I want to turn to first in our list of crises, which goes along, you know, hand and glove, perhaps with, you know, weak lensing that we just discussed, are alternatives to particulate dark matter. And those are things like Mond. So I've had on Stacey McGa from my alma mater, undergrad alma mater, Case Western,

and also from Mordecai Milgram from Israel. So I had both of Mont to discuss there, and it seems to me, and maybe I'm wrong, but there's almost, it seems to be like a renaissance now with people looking at Mond. But of course, you know, you're not bound by any, you know, desire to play politics. You'll tell me what you really think.

How seriously should I take Mon? I'm just a simple, humble, experimental cosmologist, Marr? So break it down for me in my audience. What do you, as a National Academy, you know, one of the most respected cosmologists alive, what do you make of Mond on a practical basis? Has it cleared any hurdles that would cause you to say, put your money or the NSF's money where their mouths are and put a grad student or a postdoc, sick them on a problem?

Honestly, I don't like Bond. I don't, whether I like it or not, I don't pay attention to it. And I'm going to say something that I often say in small groups. Don't worry. There's only 100,000 people subscribe to this. Don't worry. I just, I don't think it's good science. So Stacey does these analyses that I think are interesting.

You know, Stacy's got a whole bunch of galaxies for which he has well-measureed rotation curves. And then he fits, you know, semi-analytic curves to those data. and I think that that's interesting and I think it's a useful piece of information or a set of a data set that theories for galaxy formation and galaxy structure

should in principle be able to account for I don't however like the idea of Mond as an alternative to dark matter and the reason is it's just not the theoretical physics. We've been developing, you know, our modern model for physics for a long, long time.

It started, you know, quantitative descriptions of nature started with Isaac Newton. They were developed further by assorted mathematicians and physicists through several centuries. You know, Einstein then took things further in terms of a relativistic description, and it didn't So, you know, it didn't rule out to replace Newtonian gravity, but expanded the realm of applicability and clarified the realm of applicability. And then, you know, the big one was we found quantum mechanics. We found that there's, you know, a certain mathematical framework that describes the behavior of fundamental particles. Now, the mathematics that underlies all these things is complicated, but it's always motivated by the most simple physical principles.

and the most simple ideas that we have in nature, the most elementary things that you can think of, are firmly encoded in those mathematical theories. So, you know, one thing that we start with when we develop a mathematical model for physics, you know, the workings of the universe, is we say it should be universal. We shouldn't have one theory that works on Earth,

another one that works on Mars, one that works on Tuesdays, we should have one physical theory that explains phenomena everywhere and at all times and so that notion of the invariance of the laws of physics under time translation and spatial translations

gives rise to conservation of momentum and energy we can then generalize those to the relativistic context that Einstein brought us to and again that gives us additional symmetries of the laws of physics for the constraint on the mathematical structure.

And in quantum mechanics, we have internal, we have rotational symmetries, spatial translation symmetries, you know, all these very simple common sense. Very basic common sense. The laws of physics shouldn't depend on whether I look in that direction or that direction. That gives us conservation of angular momentum.

And Monge just doesn't have these symmetries built into it. The mathematical structure is sort of, we'll try what works here. And over here, we'll try something else. And it's just, I don't like it. So it says it's not only philosophic, it's not only sort of, you know, based on philosophy. But, you know, as they say, the Gustabus es nonest disputandum, you know, you can't really account for taste.

But just to push back with my trademark love and respect for you, aren't the most interesting things in physics, the result of broken symmetries, not not perfectly. If symmetry was absolute, you want to be. Yes, yes, that's a very good point. But the broken symmetries that we have in nature are manifestations of situations. The underlying symmetry is still built into the mathematics. So, for example, the Electro Week standard model, the theory has built into it certain internal symmetries that we refer to as SU3 cross-SU-2 cross-E-1. the SU2 cross

U1 symmetry, the Electroix Standard Model, is spontaneously broken. So when we discuss the low energy observational phenomenological consequences of theory, they are in this

broken symmetry phase, but the underlying symmetry still is apparent in the mathematical structure. I mean, another example is when we look at condensed matter physics. According to what I said, the laws of physics should be invariant under translations.

But when you look at a crystal, you know, in Conantzumatter of physics, you've got a regular periodic array of atoms. And so you no longer have, you know, spatial translation symmetry unless it's by that certain lattice separation. But still, the underlying physical theory is still invariant under spatial translations, but subject the, you know, but describe the particular physical configuration if you're looking at. Even when we have spontaneously broken symmetries, in nature, the underlying symmetry is still built into the... It's still respected. I see. So what about I was speaking on a podcast with my colleague, Dan Green, who is, you know, renowned in astroparticle physics and kind of making a slow conversion from, you know, string theory as a, you know, daily practice. or the daily homage to string theory

and really getting into observational signatures for experiments like the Simon's Observatory. But, you know, I asked him yesterday, I'll ask you later, you know, what are some of the most foundational things that you've learned are facts about the universe that you'd want to brag about and put on a monument,

a time capsule to last a billion years? We'll get to that for you later. But he was basically saying, like, effective field theory, you know, is extremely, is extremely productive. And it's led to multiple discoveries, high energy physics and so forth. But it made me think of this fact that we hear things from people like NEMA up the road from you at Princeton and others that, you know, space time is doomed.

And there's really nothing, you know, I think, I think, yeah, I can't really repeat what he said, but because it's a PG, no, he hopefully will come on the podcast. But, but, you know, essentially that, you know, it's, it's only, we're only seeing kind of a a shadow of some low energy limit of some higher energy effective field. It made me think what is so crazy about thinking about Newtonian dynamics? I mean, why is that so sacrosanct? The symmetry is in it we knew since the time of Isaac Newton, who we both have great affinity for, but that we knew since, you know, that there were flaws in it and inherent contradictions

that needed to be revealed and corrected by a true but still effective theory like GR, And so why hold sacrosanct, you know, these prints, or the Newtonian physics, you know, all the more so, you know, if we aren't really sure that we have a final true theory, only an effective theory? What do you say to, you know, kind of those complaints? I have, I agree with Dan that effective theories have been very, very successful. But the reason they've been successful is the idea of effective field theories is to identify the symmetries in the system and then construct a clitorial. class of mathematical models, general class of mathematical models that are consistent with those symmetries.

But Monda does not do that. It doesn't, in some sense, it's not mathematically self-consistent. You know, I don't want to, I probably can't get through it to all the details. But with Mon, if you sort of start with over here, and then you go over here, and then you go over here, and then you go over here, and then you go over here.

It's like a game of telephone, you know? Yeah. You know, tomorrow is the Super Bowl Sunday. And then by the time it comes back, it's like, you know, Franklin Delimer Roosevelt is about to be resurrected. That could be something super bowl. I don't know. It doesn't hang together. Yeah, there are issues with, you know, kind of, I think, super positions and linearity and stuff.

But let's take the opposite tack. Now, let me get your person's about a highly symmetric theory. And some would say it's super symmetric theory. In other words, you know, particle physics, we, you know, we've been kind of living under this notion that there's some unification that's possible and that, you know, there's a theory of everything that lurking perhaps for models that basically ape or replicate, you know, very simple symmetries from things like relativistic Klein Gordon equations and make those, you know, operate on manifolds with vibrating string. I mean, that's very symmetric, right? And there are those past guests, you know, Sabina Hossenfeld or Neil Turak and other. others, we've argued that we've been led astray by beauty and the symmetry, and that it's no longer, you know, in the last 50 years, pursuing that was very fruitful for the preceding 30 years, but, you know, until the time of your fellow professor, Galman at Caltech, you know, I don't see that it's been as productive as to warrant, you know, the attention to it versus the attention,

the, you know, pitiful amount of attention to something like Mon, which I agree is, doesn't have those symmetry. So how do you reconcile those two sides, you know, where you're advocate of pursuing things that have inherent properties, beauty, symmetry, et cetera, and yet in strength theory and super symmetry, they haven't borne any fruit, at least not yet. I think the issue is that, you know, ultimately what we do is physicists, as scientists, is construct mathematical models to explain results of experiments and observation. And the simpler the mathematical model, the better. but you want that mathematical model to be mathematically self-consistent, and you also want to satisfy certain basic requirements,

and the basic requirements, you know, are consisting with the symmetries that are either assumed or observed experimentally. And throughout the 20th century, we were lucky because, you know, for various historical societal reasons and just, you know, technological advances and the capabilities, we were able to very rapidly uncover a variety of layers

first going down to the atom and then to the constituents of the atom, the nucleus and the electron, protons and neutrons, the quarks, you know, etc. And we had a lot of experimental data that guided us and told us what the

symmetries were. You look at the data, and there are the patterns. We had tons of information. You know, when Boer came across, you know, came up with the, you know, his model for the hydrogen atom, chemists and physicists have been measuring spectral lines from various types of gases for 50 years. But like huge, huge tables of all these numbers. And all of a sudden, you know, with the board's model, you start to, you start to have some insight on where those numbers came from.

You know, Balmer, I think it was an 1860s or something like that when he came up with this formula? Yeah. That was the one paper that he wrote. But still, it took, you know, 50 years from that to, you know, a model. But then after that, then, you know, what's wrong. I mean, the bore atom is not the true description of the atom, but it's remarkably effective at a plain, explain.

It was a phenomenon. It was a simple mathematical model to account for the, you know, some of the observations and then it led the way, you know, with more data, more insights, more measurements to, you know, a more fundamental, what we believe now is a more fundamental description. But we got lucky in the 20th century. We had nuclear physics. We had protons and neutrons. We had beta decay.

We had all these different nuclear-bating decay. Then hadron spectroscopy. We had neutrons and protons and protons and pions and caons and romezzons. It was just like all over the place. And then, you know, we had accelerators. And we had the W. We had the Z. We had precision tests of, you know, QCD.

You know, we had a, what's it called Reggie. trajectories, is that what's called? We had, you know, the Partham model, deep in elastic scattering. So there's just a huge amount of information. And so our mathematical models were guided. You know, we like to think that we're, you know, everything was because of, you know, some type of, like, genius insight. The genius insights were pretty elementary.

It's got to be mathematically self-consistent. It's got to account for the observation experiments. We had so much data and, you know, guiding us. but you know now we've kind of you know I don't know if we haven't hit a wall but we're getting slower the you know the the sizes and price tags for accelerators

are going to take us to the next level keeps getting you know bigger the time scales price tags are bigger time scales are longer and so we just don't have the same kind of guidance from experiment that we did you know 50 hundred years ago I don't think that you know

actually lead us to abandon the notion of symmetry it's just that we just don't know what the what those symmetries are. And so what's been happening over the past 30, 40, 50 years is largely guesswork. We try guessing some symmetries. Maybe there's a left-right symmetric model.

Maybe there's super-symmetric models. Maybe there's generalized symmetries. And we see if those, you know, if we can get anything from that. But ultimately, we're limited because we don't have data. So, of course, the ultimate of all symmetries, and at least in cosmology,

is the cosmological principle. And lately, you know, the first kind of crisis we're going to talk about is the notion of claim at pretty high significance by many other, by many people, but in particular, Subir-Sarcar and group that Oxford, I think, where he's out, but other ones that claim that the cosmological principle should be not overthrown, but needs to be evaluated in the context of the distribution of radio galaxies versus the CNB Dipol versus other tracers, KSZ, things like that. What do you make of it?

I mean, first of all, would you know, would you just quit and go back to, you know, slinging pizzas in uptown Manhattan? What would you do if the cosmological principle needs to be jettisoned? I mean, would we just go into like apoplexy or what? And then second of all, what sort of mental energy do you expend on such claims? This episode is brought to you by Netflix. Most valuable promotions in Netflix are hosting a blockbuster triple headliner Saturday, May 16th. Rhonda Rousey returns to face fellow woman's MMA pioneer Gina Carano in the main event.

Plus co-main's Nate Diaz versus Mike Perry. And the best heavyweight in the world, Frances Ngano versus Felipe Lins. Watch Rhonda Rousey versus Gina Carrano, live only on Netflix. Saturday, May 16th at 9 p.m. Eastern Center time, 6 p.m. Pacific time. I actually think these kinds of tests are very important and very interesting. I think if we found a violation of the cosmological principle, I wouldn't think of that as the end of the world or the end of the universe. In some sense, we might even expect it at some level.

One thing I tell my students is that in physics, there's no such thing as an integer. There's no such thing as an irrational number. there's no such thing as zero and there's no such thing as infinity. You know, ultimately, all of our models are approximations to the reality, to reality. And again, the cosmological principle is great, is a, you know, when it comes to assembling our model of what, you know, as a essential tool in guiding the development of our current cosmological model. But, you know, our notion of inflation is that the universe is not perfectly homogeneous. There are variations from one point to another, and we know that.

We've got galaxies, we've got primordial perturbation, the cosmic microwave background. And there's no reason to expect that on super horizon distances, which we can't access to observationally, that there might be departures from perfect homogeneity and isotropy. And so if we did find that the cosmological principle was violated, if we did find those a preferred orientation in the universe, I think that would be great. It would be great now. Because there's a limit to what we can infer from whatever observations we have. And there might be subtle departures from the things we've always assumed that are going to lead us in that direction.

Yeah, I mean, I'm thinking of these kinds of tests. I think we should always be testing, you know, all of the assumptions that we've made. We shouldn't hold anything, you know, sacred or holy. So pushing those. Well, let's say, you know, God hands you, you know, a letter and it says, a cosmological principle is not valid, you know, on this scale at, you know, at 5 sigma, seven sigma, whatever. Correct me if I'm wrong.

I mean, that really wouldn't affect, I mean, we wouldn't like change the, you know, the B mode power spectra. You know, for example, it wouldn't undo in the relevant, you know, cosmological epochs surface of last scattering, even B.A.O, even epoch of, you know, Lambda domination. would it really have it like would you have to change you know cam or CMB fast as we used to use it would there would be any practical implication on a daily basis

other than like cosmologists don't know what they're talking about how would it affect your life or my life as working cosmologists if at all I think if it was if we did find there was a preferred orientation preferred direction in the universe ultimately it would affect the calculation of cosmological observables and we do know that any departure from homogeneity or isotropy

are very, very small and so it wouldn't be like a huge you wouldn't have to throw cam away completely but there might, I mean hopefully if we're doing things, you know, if we're making progress sooner or later there would be some type of tweak of cam or class we'd have to implement so.

But that would be a good thing. Yeah. Yeah, but I mean, suppose somebody came in and I said, you know, the earth, you know, Columbus, Christopher Columbus, comes in your office one day. Okay, in the 1400s. And he says, the earth is round. He's like, get the. And then he like sails around. He says, okay, watch, I'm going that way.

He leaves. And then, you know, six years later, he comes back from that side. I'm like, yes, it is wrong. You demonstrate, I believe it, it's round. And then you go down the hallway to, you know, your theoretical physics, group, and you say, look, Christopher Colomis has found that the earth is round. He went that way,

and he came back this way. And then for the next 50 years, people decide the earth is round. And that is, we have the Earth is round principle, which is a fundamental principle of, you know, of Earth studies. And then somebody winds up taking a trip to the Himalayas.

And they see that the Himalayas are really big, and they come back and say, the Earth isn't round. The Earth is not round. It's got bumps in it. Yes. But it's still round. It's not perfectly round, but it's pretty damn close.

Those bumps are interesting. They're interesting. They tell us a lot about the history of the earth and its evolution and its structure, but it does not eliminate the Earth is round principle. I think that's where we are with the cosmology. We have this cosmological principle. The universe should be homogenous and isotropic. But we know that it's not perfectly

homogeneous, it's not perfectly isotropic. We've supplanted that now with the notion of statistical homogeneity, statistical isotropy, and those are very, very good descriptions of the universe, but there's no reason to expect them to be perfect, and if we find violations, that'll be great.

Because any such violation is not going to overturn the entire structure of cosmological theory, but it'll tell us, it'll give us a lot more clues about where the universe came from. Yeah, as another shout out to a famous Isaac, and we already talked about Isaac nude, but Isaac Asima said, you know, if you believe the earth is flat, you're wrong. And if you believe the earth is a sphere,

you're also wrong, but you're less wrong. And that's a guiding principle, I think, for what, yeah, good science should be. And I want to pivot from that to the, you know, to maybe moving forward in time from, you know, the Big Bang itself, which we'll get back to maybe we talk about inflation later on. But, but there was a, a kind of a social contagion that went on over the summer where there was a lot of attention paid to an article written by a person who went to Columbia. He might have even been there when you were there named Eric Lerner, who's a plasma physicist. He's interested in fusion, all sorts of fun things. Not a PhD, not a professor. But he has this book from the 90s

called The Big Bang Never Happened. And this article went around based on the web telescope data of early spiral galaxy observations, that the, you know, he claims there's not enough time since the Big Bang to generate this spiral phenomena and that it's in conflict with other things. So he believes in a steady state, a static universe, which has myriad problems. And I debated him, I kind of had an asynchronous debate with him

and I had Garant Lewis on, and he and I spoke about this gentleman's work. But anyway, what do you make of this? If let's say we were to really, and as I think it is true, that we don't understand why these galaxies observed by Hubble first in the 90s when he wrote the book the first time, or web galaxies, which are higher redshift and the redder and easier to see with web than HST, but still some of them are seen by Hubble. Why is it that, you know, people, you know, what would that call into question? or if anything, does it cause us to reevaluate Lambda CDM? Does it cause us to reevaluate only, and I say only in quotes, you know, galaxy structure formation? What do you make, did you hear about these claims?

What do you make of them if you're hearing about them for the first time? I didn't hear about these claims, but claims like this come around all the time. Yeah. I mean, I remember when I was in graduate school, post-up, people were starting. discovered galaxies of redshift close to one. And then this rolled out the technological model because how can you

make a galaxy all the way by reds, not actually, there's a cluster of galaxies and redshift of one. And then like quasars start appearing at higher redshift. How can you make the quasars? There's just not enough time for it. There's also this issue of people that were ages for stars. People had

stellar ages of labored, stars and labrower clusters that were older than the age of the universe. how's that happen that's got a rules, rules out there but I remember you probably didn't know David

Schramm David Schram was a larger than life figure in which is Chicago I met once yeah yeah and I remember

there was one of these debates going on at the time and you know it came to in the class and he said you know the earth is round

we don't understand how tornadoes form very complicated we do not have a successful theory of tornadoes that consisted with around Earth.

But that does not mean that the Earth isn't round. It means we don't understand how tornadoes form. It's the same thing going on here. Galaxies, especially these high-wrenching galaxies, are very complicated.

I mean, the high-res-of-cats are not more complicated, but they're not as well-observed, measured, you know, as local galaxies, but they're very complicated objects. I was just at University of Illinois, the UIUC last week. I was talking to Stuart Shapiro.

and I was asking him if he knows how supermassive black holes are formed. So BC Quasars, a very high red shift with very large mass. Quasers get up to 10 billion solar masses. You know, total 10 solar...

And it's not clear how you get so much mass in such a small volume. How you produce such a massive black hole in such a short period of time. But their ideas about this, how this might... happen and it doesn't violate any fundamental physical, you know, theorem. I don't know how these supermassive black holes are formed.

To me, that's the most interesting puzzle, but it doesn't, I've never worried that it invalidates the our cosmological models. No more so than our inability to predict weather patterns invalidates our, the Earth is round principle. So I wanted to now pivot into more maybe, I always say red meat, but I'm going to say, you know, vegan white tofu for my vegan listeners. And that's something near and dear to both of our hearts. And that's the so-called Hubble tension, which is one of the more prominent tensions,

at least in observational cosmology. And I had on Adam Reese, your colleague there, I had on John Mather, also. colleague there. And, you know, we discussed some of these, some of these issues. But I'm tired of the blandishments, Mark. I'm tired of, well, we need more data. I want somebody to come out, tell me what the heck's going on and not postpone or say, you know, if we don't understand it, that would be really excited. It's like, remember, like, in the 90s when they said, we're going to build the LHC and or the late, you know, late 90s or we're going to build the LHC. And if we don't find the Higgs, that'll be really exciting. Like, if you don't find the Higgs, you're all going to be out of a job.

You know, so let's talk, you know, brass tax here. What's going on? And who's right? What does? I know you're a man of very strong opinions and you won't weasel or waffle out of this. Who's right, Mark? Tell me, I need to know. Really?

Honestly, I have no idea what's going on. If you had a bet, if you had to bet your new dog, your Rottweiler, I don't know. First of all, can you outline from your perspective, you know, why this? This is important. First outline at, you know, upper level undergraduate sort of level from my brilliant audience. But what is the Hubble tension? Is it a problem? You know, we have exquisite measurements from two different camps. They don't agree. But what are the implications for cosmology? I mean, I get asked this all the time. You know, what's going on? Talk straight to me. I can handle it, Doc. I don't know. I mean, if I actually knew that there was something wrong with the CMV analysis, they were just, you know, they forgot to like, you know, you know,

their C code. They just forgot to, like, put the right compiler flag on it or something. Or if they just missed a factor of two somewhere, if I knew that I would have, I would have published it. I would have told the world that we wouldn't be worrying about it. Same thing with the supernova data. If I, like, went in there and realized, oh, you were just pointing the telescope with the wrong,

except the variable, you know, that's the one you're supposed to not going to. Then we

wouldn't be worrying about it. I mean, I really don't know. I mean, C and B analyses I know and understand,

and there's nothing wrong with them. A lot of people have looked at them. We've got data from several different telescopes, that data has been

analyzed and reanalyzed by a variety of different people and groups and, you know, the, Hubble parameter that we infer from all those measurements is low.

67, 68. And then they're the supernova measurements. And I'm kind of in a, probably have a different opinion or view of this than most other people. Because when I go to work, I walk past Adam's office in the morning. And I see him. And he's always in front of his screen actually calculate him.

Okay? He's not like a, just smoke. and cigars and like having the people down the dog and things like bring him things he's actually like something and you know

every couple days or every couple weeks on archive there's some paper that appears or someone says well they forgot to take into account

the metallicity evolution or they forgot to take into account and then I go past Adam's office I'm like hey did you see this paper

on an archive about the metallicit and he'll say well actually yeah you know what they said is correct you have to take an account

the metallicity evolution but look we did it and then he'll show me, you know, I'll go to a screen. There are results. He said, okay, this is the analysis, you know, without it, and this is the analysis with it. And they're right.

It does move things down, but it's half a sigma, and it's already in the analysis. We already take that into account. And so, you know, all these, like, you know, things that people, you know, you know, lob at the measurements. He backs them all the way. And so.

And he also does the analysis. Like, he does the CMB analysis. You know, I couldn't do the supernova now. He's a very important. impressive scientist. Yeah. And it's not just that. The other thing,

so I told you I wrote this in Rev article on Hultonion and Dark Energy with Adam. And I'm familiar with the observations that people have done, but in the process of writing the article and actually like, you know, Adam wrote most of the observational part. But, you know, I want to read through and make sure everything hangs together and, you know, and understand.

And also, at the same time, I'm across the street from the Space Telescope Science Institute. And so I see space telescope, you know, scientists there. And one of the things I've come to appreciate is that, you know, there's a huge amount of calibration and benchmarking and bootstrap tests and engineering infrastructure behind HST. And it's the same telescope that's been making all the measurements that they use for these Hull-Prameter measurements, you know, over the past 30 years. and so it's not like you know, you're using one telescope to observe this system

and another telescope to observe that system and then trying to figure out how to calibrate this one against that. There's a lot of, you know, it's all calibrated against itself currently calibrated. And so it's not that, you know, someone's just being sloppy or forgetting to do something. This is as careful of measurement, I think, you know, as any that you would find in physics.

And so it's not something that's just, easily waived the way. And so when people ask me, you know, what's going on? You know, who's wrong? I just, I don't know. You spoke here remotely at least two months ago at UCSD and Berkeley. We have this kind of joint critical, high energy astropartic. And you spoke about possible solutions to it.

And I brought up my favorite, personal favorite. And I beg your indulgence just to hear the reason why. Of course, you're very familiar with primordial magnetic fields. but that's my preferred explanation for it, you know, based on work by Levan Pogosian and another colleague of his, whose name I'm forgetting right now, but I did a video about how their paper basically, you know, could lead to a possible solution of the reconciliation of the tension without costly psychotherapy. And the argument, you know, could be better recapitulated by you. But nevertheless, the reason I like it are philosophically attracted to it is that we know,

magnetic fields exist. And we don't know exactly how magnetic fields the size of a micro-gauss come to be in the Milky Way galaxy, or, you know, nanogouse and the intercluster medium. But we've never detected, correct me if I'm wrong, a truly primordial magnetic field. And yet we see the, you know, kind of the sprouts that must have emerged from some primordial seed. So what do you make of the solution via the primordial field, since there's an infinite number of possible resolutions, theoretical explanations for the Hubble tension, what do you make of that argument that the primordial magnetic field energy plays a role? And then what do you make of your own model or suggestion that it might be due to evolution of some primordial field or so forth?

But you'll be better equipped to deal with explanations about it. So first, what are your you know, kind of straw man and steel man, the primordial magnetic field, and then the models that you've worked on. I like the primordial magnetic field idea because as you say, it's economical. We don't have to completely reinvent fundamental physics

or come up with these scalar fields with wacky potentials that we had no idea why they would be there. The only, it's not an issue. I think the limitation with the magnetic fields. So the only reason I don't just jump up and say, I think it's going to be magnetic fields

is that it's very difficult to calculate fully the implications of these primordial magnetic fields. It's fundamentally nonlinear. You know, the standard cosmological model, when we describe cosmic background and isotropics, we got lucky. It's a simple system. The fluctuation amplitudes are small, and so we know how to calculate.

You know, a priori, it didn't have to be that way if the primordination amplitude was more like 10 of the minus 2 instead of 10 of the minus 5, which is as likely from a theoretical point of view as 10 of the minus 5, then we would have had a much harder time actually, you know, interpreting the data. In primordial magnetic fields, the theory is fundamentally nonlinear, and so it's just difficult to calculate. you know, it's probably, it probably more easier, right? With CMB polarization. Yeah. I think it probably warrants more attention and more effort,

but it's just not something that I have yet done. I think it is interesting and important and someone should do it. Maybe I should do it, but it just haven't yet. And I'll talk about the model you discussed on our seminar, yeah. I mean, early dark energy. You know, the minus is that we introduced this, we've introduced a scalar field with features and parameters that come out of nowhere. The advantage is that we know how to calculate.

It's the same type of perturbation theory. And so we can, you know, write down the mathematical model and then evolve it, calculate it, you know, figure out the observational implications. And it works. I don't know why it works. I can't say, look, it's just what the doctor ordered,

and, you know, this is, you know, this is exactly what we would have expected. It's kind of a dramey model. And from the point of view of, you know, what, you know, your particle theory friends would call a UV completion. I mean, we don't know where this comes from, but it does work.

And I have to say when we wrote that paper in 2018, I did not expect it to work. I thought we would write an upper limits paper. You know, we tried to do this. And in this paper, we showed this ridiculous idea. In fact, as you might have expected, doesn't work. You move on with your lives. But, you know, it turns out that it did work.

It was surprising. And I found that, you know, interesting that it could work because none of the other solutions were if all the late-time solutions, they don't work. So to me, this was a model. a ridiculous model, but at least it works. Once you're willing to take this bitter pill, everything else follows. And other people get interested in well, as well.

And I think until we have anything better, or until, you know, somebody comes in and, you know, shows that the, you know, line 683 in the C code that they've been using to analyze the act data, you know, was missing a comma, that changes everything. Yeah. In the meantime, I think it's... Probably worth exploring or thinking about,

but I don't proselytize. I don't think it's the truth. So it turned out to be more interesting. And then we got lucky. I don't really understand it. Then, you know, Act came out with an analysis two years later. And, you know, the lead author was Colin Hill. And Colin is like, like, really knows what he's doing with data and is unbiased.

You know, he had written several earlier papers analyzing large-scale structure, showing that it was disfavored early dark energy. And then he was the first author on this Act collaboration paper, but they looked at the data fully objectively without any intended consequence, without any biases. And they found that the Act data was more consistent with early Dark Energy than Lambda CDM, which I don't, I mean, a lot of uncertainties and issues, you know, that in some ways, that's a very preliminary analysis. I don't think it's at all the last word. It was done on a fraction of the act data. It was done fairly early on. And as you know, whenever you do a CNB experiment,

you don't just get straight to the science results. You discover the science simultaneously with the instrument. That's right. And bonds of that very valued collaborator on Simon's Observatory, and of course he'll be having a lot more to say when our instrument gets first light next year, over there in the Atacama Desert, pivoting back to where we began with broken symmetries.

I mentioned, you know, if not for the broken symmetry between matter and antimatter, you know, you and I wouldn't be having this conversation. And yet it's a very tiny asymmetry, but it's, you know, hard to think of something more impactful. And I was reading a paper which, you know, I remember when it came out because I remember the events by the alpha magnetic spectrometer on the space station back five, six years ago. And then remember the paper that came out that Vivian Poulan wrote with you and several others. including Joe Sill. And that was entitled, you know, where do these anti-heelium events come from? So we won't talk so much about the results, although I'm not sure that they did stand up to, you know, further reanalysis or where they confirmed.

Can you first say something about that? And then can you talk about these anti-heelium and anti-matter clouds that are existent in this model and how they could provide the source of some of these, of these particles that seem to be observed at least by the AMS on the ISS. So, first of all, are these measurements still, you know, are they still credible, or do we have further, you know, disconfirmation about that? You didn't warn me that you're going to ask me about this. Sorry.

Your paper, you're over anything you put your name on. This is a cool paper. Yeah, yeah, yeah, I know the paper. I remember the paper. I haven't kept up, though, with it. That's the thing. So when we wrote that paper, the anti-healing results were not yet refereed. There were sort of talks, and it was understood that it was preliminary.

But even though it was preliminary, there were certain interesting things about it that were unusual on cutter eye. So I don't really know what the status of that is. I have not heard a lot more. The anti-clouds were kind of a crazy idea. and I don't think that, you know, when I looked at that paper in that model, I didn't necessarily put it forward as a model of what I think is actually going on, but sort of as a model of how crazy things would have to get if this result holds up. Right.

So, I mean, how much do we, because this I want to pivot to the extremely early universe and Sakharov conditions and whatnot. So how do you, you know, kind of get your attention drawn to an anomaly or a crisis, you know, in cosmology versus particle physics? And, you know, how much progress could we make the, you know, barion, anti-barian asymmetry problem from pure cosmological, you know, insights, observations, data, pure theory? You know, how much of a concern is it that, you know, I mean, the critic will say, well, you have this edifice built on. sand, you've got all this, you know, or anti-sand, you've got all these dark forces and fields, you know, 95% of the universe is completely alien to us if they exist at all. Some people say, like, Milgram, it doesn't exist. And even people say that dark energy doesn't exist. I think

Sarkar had some papers about this, you know, prominent people. So what do you say to people that, like, how can you predict, you know, that we'll see fluctuations in the CMB from inflationary, you know, gravitational waves? If you don't even know why there's matter, versus antimatter in the universe. To what extent did that type of tension keep you up at night? I think there are two things that I think that interest me. So one of them is that in cosmology and particle physics, there are tons of anomaly.

Just tons. And any given day, there's like tons of measurements that disagree with what we would have expected based on the standard model or our modeling of astrophysical. systems. And then there are tons of theorists thinking about things. But for some reason, the vast majority of theorists tend to gravitate or cluster around a very narrow range of anomalies. And I think to a large extent cosmologists are bosons. And if somebody is thinking about the Hubble tension, they will also think about the Hubble tension. They're not going to think, okay. There's 16 people thinking about the Hubble tension. That's good. That's a very

very important tension. We don't understand it. Someone should be thinking about it. But then over here, there's this other tension. And maybe we should have, you know, eight or nine or ten people thinking about that. And then, you know, there should be, you know, if this was a business, you know, we would have a manager at the top and says, okay, there's this tension. There's this tension. There's this tension. Okay, Kimi-Kowski, you choose five people to be in your team. You think about this tension. Daldar Yaga, we got this tension over here. You pick five of your friends. go think about that. Kazowski,

we need you guys in Pittsburgh. We look about this tension. But it doesn't work that way. Everybody decides what they're going to do, and everybody winds up focusing in a very narrow range of problems. Then there's a question, you know, when do I choose?

How do I choose what to work on? I don't really know, but I think, I think, you know, to some approximation, I have some students and stocks and have collaborators elsewhere. We sit around and we brainstorm and we talk about

things and we read papers and occasionally, you know, I mean, often we'll talk about some anomaly that appear in the data. We'll try to understand it and try to figure out, you know, is there any simple obvious explanation, you know, in the analysis

or in the interpretation? And, you know, most of the time we'll conclude, yeah, it's an anomaly. We understand what's going on. And that's it. We don't have anything else to say. But sometimes we'll see something like that, and we actually have something to say. So one example is there's a paper that showed up almost a year ago, an archive by Mark Postman and Todd Lauer and the New Horizons team. Right.

And it was a very, you know, the style of the paper was very astronomical. It looked like, you know, an apt-j abstract, the language. which was very astronomical. And so I think it just passed a lot of people by. But I know Mark Postman, because he's a space telescope science institute, and I see him all the time. And so I read, you know, through it. And as it turns out, they did this incredible measurement.

So you know about New Horizons. Yeah, that Pluto space. Yeah. So I took a picture of Pluto and Karen. And it was like incredible, absolutely amazing. that something that humans built got that close to Pluto and took such detailed pictures of Pluto and Keron

less than a lifetime after Pluto was discovered. Yeah, and less than a human lifetime. And then, many years after launch, right, yeah. Yeah. And then, but it didn't have any breaks on it, right? They just sent it out there. Then, you know, it sailed past Pluto, take a bunch of pictures.

Yeah. But we can't, but then it kept sailing on. And then a couple years later took a picture that asked that Hyperbilt object. peanut shape thing. But it's still out there, and it's moving, you know, it's going for, it's like 70 AU from the sun.

So it turns out that nobody has ever been able to measure the cosmic optical background. So you look at the sky, and it's dark. Nobody's actually ever been able to measure how bright the sky actually is in optical. We know it radio frequency,

that's the cosmic microwave background. Nobody's ever been able to measure the cosmic optical background because there's so much scattered light from the sun. So even HST and JWST, they're above the Earth's atmosphere, but they're still, you know, they can't do this measurement because there's still the solar system. And there's a lot of scatterlight from the sun. So this, you know, New Horizons, the camera was not that sophisticated.

It wasn't the greatest thing that camera that anybody's ever built. It's not a JWST camera. But it was out there, 70AU from the sun, where the scatterlight from the sun, where the scatterlight from the sun is reduced by four orders of magnitude. And so Mark Postman and Todd Lauer went to the European Horizons people like, just point it at nowhere. You're doing nothing else with it.

It's going to be a while to find another Khyber Belt object. Just point it at nothing and take a picture and see what happens. And so they did that. And they measured the cosmic optical background. They got the first high signal-to-noise measurement of the cosmic optical background. And the interesting thing was that Mark Postman and Todd Lauer,

you know, Mark Postman was involved in the original Hubble Deepfield. He knows more as much about galaxy populations at high redshift, at low redshift, as anybody. Yeah. And so they had an expectation for what the cosmic optical background would be

due to the integrated light from all the unresolved galaxies that we know to be out there. And it turns out that the cosmic optical background they measured was twice what they expected from all the galaxies, known galaxy

populations in the universe. So for every photon that comes from some star that we know about somewhere, there's another photon coming from God knows where. So the reason, so we wound up writing a paper, and the reason we wrote a paper is that an obvious, you know, exotic physics explanation

is decay of an axon particle. Two photon decay of an axiom. And my group had been working on this new type of cosmological measurement called Line intensity mapping. And JPL, your friends,

you know, Jamie Bach. Jamie Bach, yeah. Yeah, Jamie's got this project called Spirx, which is going to be launching, you know, the next year or two, and it's going to do light intensity mapping. And we realize that if that Cosmic Optical

Background Access is, in fact, due to decay of an exotic particle, it's going to show up in Speorex at, you know, the many thousands of signal. So sphrex is just It's like Going to be like a

Taking candy from a baby for spherus to You know Verify or disprove this hypothesis So that's the only idea we had the idea that it might be did a two photon to give an accent That is not at all profound That would be an embarrassing paper to write But we wrote the paper because we were able to We knew that this idea would be tested

It was a great target for spirox Yeah And as the Hubble tension goes I mean I've been I heard about it a lot because, you know, Adam's at and Chuck is right down there next to him. But here, you know, think about it a lot.

And in 2016, I wrote this paper with Tom V. Carwall, who's a graduate student. The basic idea behind early dark energy, again, is not that profound or it's pretty simple and obvious. So we did write a simple paper about that in 2016, but it took two more years to actually do

the complete analysis. The to figure out whether this idea could be made for. Would that then have, you know, we, as you know, look for a time-dependent, but not, but spatially isotropic, cosmic pyrofringens, polarization rotation of e-modes or grad modes into curl modes, as I will always call them. And we look for a time to put so far.

We haven't seen that. Bicep hasn't seen them and so forth. With this signal, I mean, is there any kind of mutual constraint or concomitant limit that could be put on, let's say you accept these at face value from New Horizons, would that give any kind of hope for you to write a paper called the Axion pursuers guide or something like that? I don't think we need to write that paper because axions have just become the preferred, you know, workforce for theorists thinking about exotic new physics and dark matter and dark energy and early dark energy. Um, I don't think I'd be the person to write that.

I've written some papers that have accents in them, but I'm a bit player in the whole. All right. All right. Well, I had on, uh, you know, not too long ago, um, it was David, David Chalmers, who's, I think, well, he's in New York. I think he's at NYU, actually, not a club. But anyway, or maybe he's a club. I forget. But the point is, he's Australian.

He's originally from Australia. I said, you know, you're well known, uh, for all these, you know, the heart. hard problem of consciousness. You know, and, you know, when I have ACDC, also from Australia, on The Into the Impossible podcast, I can't not ask them to play, you shook me all night long. It's just, it's just, it's not fair to them, to their uvra. So I'd ask you, you know, is that really the pioneer in a lot of these ways of thinking and the detectability of inflation or its constraint?

You know, what is the status of inflation from Mark Kamankowski's perspective? of 30 years, you know, after we met or, you know, you really were initiating a whole field, which would become my, you know, my source of where my bread gets buttered. What do you view as the status of inflation? Is it stronger than ever? What kind of grade would you give to inflation at this point? And what kind of perspectives do you have for prospects for what we're going to do in the future? I have to say that, I mean, the basic status of inflation, the basic idea, I think, is the same as it was 30, 40 years ago.

There have been a lot of theoretical developments that are interesting. A lot of them done by people like Dan Green, but also Lanaro Cennatore, Mathes Alder Yaga, Daniel Bauman There's been this whole Jared Kaplan at the Infitzpatrick There was a You know starting about 15 years ago

There were slew of papers on effective field theory descriptions of inflation Which I think are important Because they puts inflation model building On that level of mathematical self-consistency

Symetries built in that I think is, you know, one of the things we're supposed to be doing in theoretical physics. In terms of observation experiment, I have to say that inflation is doing far better, I think, than I ever would have expected 30 years ago. So it's almost 30 years ago that I started writing papers on CNB tests of inflation. And, you know, I was a postdoc and an assistant professor, and I was just trying to write papers that made me seem clever so that I'd get a job and then get tenure.

And I remember once, you know, I was giving a talk about cosmological parameter determination with the CNB. This was, you know, 1995. And it was before WMAP was selected, but they were proposing it. It was MAP at that time. And I remember talking to David Wilkinson, who was the W from it. And he said, you shouldn't be so, you know, we wrote these papers. We were thinking, in the best case, in the best case

if they get all the money in the world and they have genius instrument builders and the thing doesn't blow up on the launch pad and it makes it, you know, they get the funding and they make it normal. In the best case, they should be able to make this measurement. I remember David Wilkinson came up to me afterwards.

It's like, it's really not that difficult. He's like, you know, it's not the, we can do this. And I was like, really? Because, you know, Kobe, we were coming off of Kobe. and, you know, Kobe took more than 20 years from conception to launch. It's all I was thinking. In the best case scenario, we have an experiment like the one, what we had in mind is actually less than what map turned out to be

after a few years of observation. And I had, in my mind, this would take another 20 years, you know, before this happened. But as it turned out, you know, the first results, the first, you know, results on the, you know, the first acoustic, peaks in the C&D power spectrum came from Boomerang in spring of 2000. And then a year later, there was further measurements from Daisy that lined up right on top of each other. And it just, it was astoundingly good. We had no idea if there would be reanization.

You know, there was a really good chance. They would all be completely washed out by realization. And we always thought, you know, maybe for some reason the universe could get reanization. but probably, you know, it's important to measurement to make just in case probably I'm not going to see anything. You know, but it turned out to be, the experiments

turned out to be much better than I thought. And the agreement of the theory with the model is, again, much better than I ever expected. You know, we see a power law over three decades. We see a spectral index which is close to, but not exactly,

equal to one. You know, if it was exactly equal to one. Suppose, you know, it was 2003, we had plank, we had WMAP, we had AC, we had SPT, and all the data said that n-sum-s is equal to 1.00 plus or minus 0.01. I don't know if we're still thinking about inflation. We just say, well, you know, that's a scandal of variance back, and that's what you expect. But inflation is a physical model, and it predicts that it's not exactly equal to one. It predicts that's close to one, but not exactly equal to one. So that, you know, when that started emerging, to me that was remarkable.

And now we have measurements of the mass distribution from lensing. Again, we were writing papers about this years ago. But, you know, when it actually happened, it was spectacular. I think the status of inflation is that the, you know, it was a great idea 30 years ago, one that

should have been taken seriously 30 years ago. But I think it's a, you know, it's harder to disregard it. Much much harder disregard it now than it was. 30 years ago. Well, Mark, you've been so generous with your time and your attention, all these many years to little old me. I can't resist to do what I do with all my guests that honor me by coming on the podcast and ask you just two existential questions.

We have time for two of my patented fantastic final four. And the first one, I'm going to ask you about, they're both related to Sir Arthur C. Clark. And the first one has to do with his famous statement. that any sufficiently advanced technology is indistinguishable from magic. And the way I like to kind of put a spin on it, the Keating spin on it, is to ask you, what discovery in all of science, maybe just in your local neck of the woods of science, would you most want to kind of trumpet to the universe and something that will endure as a byproduct of the magic of science and technology that human beings or you have created

and sort of give us a little swagger for all humankind. Swagger for all human kind for science. From science, yeah. I'll give you a minute to think, but Feynman, who is Sean Carroll's previous office occupant at Caltech, he said the most astonishing thing and the shortest, fewest amount of words is the atomic hypothesis, so that everything's made of Adam. So I wonder from your perspective, what is the most astonishing thing that humans have discovered about the universe, about science,

anything. I think this cosmological model that we have is pretty remarkable. I think that's a confluence of a number of things. You know, ideas in theory, but also the technology that allows us to make the measurements.

But it's also a product of the fact that the universe has cooperated. You know, as I said, the fluctuation amplitude is small, which means that we can treat the perturbations with simple calculations. And, you know, the universe is very, very close to isotropic and homogeneous. And it turns out it's a very simple universe.

You would have never, you know, if someone 150 years ago told you that, look, in the next 150 years, people are going to understand the largest scale structure of the universe, you wouldn't have expected that the thing would have turned out to be so simple. That's right. So we got lucky, you know, with the cooperation. you know, through collaboration of theory, technological advancements, you know, really bold and talented experimentalists, like, you know, you and people that you work with and have work with. And the cooperation in the universe, we've assembled this incredible model so we can, you know,

say with some confidence what was going on, you know, just a few seconds after the big thing. No. No. It's not something that's the standard model of elementary particle theory. pretty remarkable. That's a, to me, I've been teaching quantum field theory for a couple of years now.

And every year I've tried something a little bit different, so I keep learning. And it's a, the mathematical structure of quantum field theory is absolutely remarkable. So Mark, with that, I want to ask one final question.

Also kind of provoked by Sir Arthur C. Clark, he said a lot of fun things that are, really enjoyable to whip out at faculty meetings, such as for every expert, there's an equal and opposite expert. But one of his quips I want to lay on you right now is our final question, then we'll wrap up. And that is when a elderly but distinguished scientist says something is possible, he or she is most likely right. But when he or she says something is impossible, they're most likely wrong. Now, I'm not calling you elderly, and you're only a couple years older than me, I think, But you're distinguished.

I want to ask you in that context, what have you changed your mind about? What have you been wrong about, if anything? Oh, I've been wrong about lots. It's kind of interesting. I think, you know, having, I started as a professor 28 years ago. And I had certain notions about how things work and how scientists work that I now realize they're completely wrong.

I had notions about how graduate students should be trained 30 years ago and my notions about how they should be trained now are completely different. In one way, give me a quick example.

How have you changed? What's something you changed with regard to graduate education? I think I was a, you know, when I first started at Columbia, I was probably a real hard ass about all the classes

that students need to take and all the things things, technical things that they need to master before they can really be successful in research. And I still think that all those technical skills in mastery are important. But now, you know, now I think that the most important thing that graduate students do is get involved in research as soon as they get into graduate school. I mean, it happens with anybody who's ever had a graduate student. Do you have a graduate student that come in?

The first date, they don't know anything. They don't know why the sky is blue. They don't know why the grass is green. they don't know, you know, where to find their office. They don't know anything. They can't, they don't, you know, how to do, you know, how to calculate anything. And, you know, within three years,

you're, like, sitting across the desk for them, or, like, you know, talking about what they're working on, and you realize that are, like, explaining things to you that you never thought about. And it doesn't happen because you're, like, sitting there, like, giving them lectures and saying, do this problem, do this problem, do this problem, then come back and show me your solutions.

I don't do that. But the most important, it's like, you know, teaching people to swim. You know, when I was a kid, take swimming lessons. We said to the side of the pool and perfect our strokes. You know, they give us feedback. Yeah, that's good. That's good. That's how you do it.

And perfect the stroke. And then I get into water and it goes completely worthless. That's right. Theory and practice are very different. Well, Mark, I want to thank you so much personally for being such a, just a mentor, a friend. I always think, you know, when I hear some crazy idea, what would Mark think? And it's not always the sober voice of reason that you often provided me in my career,

but it was the encouragement to do things like come up with, you know, how we would actually do Bicep and see it through to fruition. And now to see 22 years later, you know, Bicep Array is still operating at the South Pole. And we have a $10 million project called the Simon's Observatory, which features three, you know, basic. direct descendants of bicep type ideas, which trace themselves back to your paper with your colleagues, Andrew Jaffe, good friend, and Lemon Wang. But that's just one of many ways you've influenced me personally. You don't have to respond. You don't have to rebut this.

But I want to thank you on behalf of my audience and me in particular. And I hope we'll get to see each other soon out there in Balmy, Baltimore or out here in Sunny San Diego. Well, thanks to you from actually making Bicep happen, for making Bolar Bear happen, for making for making Simon's observatory happen. As I said, you know, science and physics

is mathematical models for experiments, results of experiments and observations. And so there's really no point to anything that I would ever do with all the things that you and your colleagues are doing.

Oh, thank you, Mark. Have a great day. I'm not just saying that. I'm not just saying that. I know. I know you're not.

You're not the sunshine in roses type. Mark, thanks again. Any sufficiently advanced technology is indistinguishable from magic. Thank you for listening to Into the Impossible. Keep in touch by signing up for Professor Keating's Monday Magic email at Briankeetting.com slash list.

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