Into the Impossible With Brian Keating - What Happened AFTER the Big Bang? Bruce Partridge (#375)

Episode Date: December 8, 2023

What happened after the Big Bang? To answer this question, I invited a true pioneer in the field of cosmic microwave background, Bruce Partridge! Bruce Partridge is an emeritus professor of astronomy in the science department at Haverford College. He has served as an Education Officer of the American Astronomical Society, president of the Commission on Cosmology, International Astronomical Union, and President of the Astronomical Society of the Pacific.  His research interests lie in the intersection of cosmology and radio astronomy, and he spent most of his career researching the cosmic microwave background. Join us as we embark on a captivating journey into the early Universe! Key Takeaways:  Intro (00:00) Judging a book by its cover (01:27) Coupling together theory and experiment (04:18) The discovery of the coming microwave background (07:23) Patience and perseverance in scientific research (15:01) Nerve gas and rabbits in Arizona (18:27) Why we need to listen to theorists (21:05)  Inflation and the dominance of a theoretical paradigm (24:59)  The Big Bang, CMB, and the lithium abundance problem (33:33) Bruce's philosophy of pedagogy (47:40) Outro (52:48) — Additional resources:  📢 Ownership of your health starts with AG1. Try AG1 and get a FREE 1-year supply of Vitamin D3K2 and 5 FREE AG1 Travel Packs with your first purchase 👉 https://drinkag1.com/impossible ➡️ Learn more about Bruce Partridge: https://www.haverford.edu/users/bpartrid  ➡️ Follow me on your favorite platforms: ✖️ Twitter: https://twitter.com/DrBrianKeating  🔔 YouTube: https://www.youtube.com/DrBrianKeating?sub_confirmation=1  📝 Join my mailing list: https://briankeating.com/mailing_list  ✍️ Check out my blog: https://briankeating.com/blog.php  🎙️ Follow my podcast: https://briankeating.com/podcast  — Into the Impossible with Brian Keating is a podcast dedicated to all those who want to explore the universe within and beyond the known. Make sure to follow so you never miss an episode! Learn more about your ad choices. Visit megaphone.fm/adchoices

Bruce Partridge, Emeritus Professor of Astronomy in the Science Department at Haverford College is a true pioneer and hero in the study of the cosmic micro-rate background. He's one of the OGs. He was involved in the first measurements of the C&B spectrum to confirm its true cosmic origin. That result decimated the steady state theory. He was also one of the first scientists to look for the small-scale temperature fluctuations, which provided us with detailed insights into the distribution of matter in the early universe. He's made major contributions in both theory and experiment, helping us understand the cosmos, turning cosmology into a precision science. Join us for an exciting episode as we explore the early universe. Any sufficiently advanced technology is indistinguishable from magic. Welcome everybody to another exciting episode of the Into the Impossible podcast featuring a friend, a colleague, a collaborator.

and most importantly, a mentor in the space of education of my field, cosmologists, generations of them. And that's Bruce Partridge, who's an emeritus professor at Haverford College in Pennsylvania. How are you today, Bruce? Doing well. You're eager to talk to you. Yes. Maybe even at you. Yes, the internet is quite amazing.

It allows us to do these things. And I am talking to Bruce because of many things, first of all, he's a great. an incredible scientist and amazing knowledge about the field. It's past, present, and maybe even its future, having been involved with some of the greatest experiments of all time, including perhaps, you know, one of the first or second experiments to really go after the detection of the CMB and its properties. And Bruce was involved with my grand advisor. So my grand advisor was David Wilkinson.

and he advised Peter Timby, and I'm still, Peter Timby is soon to be hopefully collaborating closely with us in the Simon's projects as well. So as I talked to you earlier in the week, we always love to do a segment on this podcast that represents something you're not allowed to do. You're not supposed to do, which is to judge a book by its cover. And you have two wonderful books,

one of which I read 30 years ago, which is called 3K. So I've always been eager to ask you how you came up with the title. and the cover design because it depicts the horsehead nebula, which to my knowledge has nothing to do with the 3 Kelvin background, but maybe it does. So, Bruce.

The clever title, 3K was mine. I figured it was a nice abbreviation. The damn cover was designed by Cambridge University Press. It's part of a series, and they all show the horse head nebula, which you're right has nothing to do with the microbe background. I was thinking we could talk about the nebulae

just for a minute in that it's often said that I think it was McKellie. had detected properties of cyanide in the interstellar medium. And that supposedly that was, you know, revelatory of a 3-Kalvin background. What do you make of that? Did you know about those measurements? What do you think about those measurements in the early days? 1940.

The situation is following. These little cyanogen molecules, CN, and float around in space. But they appear to be excited as though they were bathed in a roughly 3-Kelven field of radiation. They're not at zero temperature. They're at 3 Kelvin, 3 degrees above absolute 0, or roughly 5 degrees Fahrenheit above absolute zero. This is written down back in the 30s and 40s, and it was described by the discoverer as a being of some interest. But George Field, among other people, is remembered reading that paper. And then when Penzias and Wilson found the 3 Kelvin radiation, he recognized that that 3K, 3 Kelvin radiation.

might be responsible for the excitation of cyanogen, and that gave us a measurement at a particular wavelength of 2.6 millimeters. It wasn't very precise, but it sure helped establish the cosmic nature of the radiation that Benzius and Wilson found. That's right. Now, I look at a lot of your research, and you have an H index.

I think it's the cube of mine or something like that, or a number of papers and citations, that number close to 100,000, is just astounding. And I've gone through many of them because they're all treasures and little diamonds and they're not so rough. Many of them are incredibly readable. But I want to ask you about when I think of the Bruce Partridge brand, I think very high quality theory, but always attached and never divorced from experiments from the very beginning. Can you talk about your philosophy as a scientist to couple together theory and experiment is very hard to do?

but you managed to do it. Can you give us tips to mortals like me? How did you manage to cultivate that? Is that intention by intentionality? Experiments like Plank, Act, now the Simon's Observatory. What is that philosophy that's as guided? In terms of the theory side, I was interested in a field that was interesting, but fairly simple. If you go back to the 60s, cosmology was simple.

We didn't know anything, so it was a very simple subject we get into. And that extended also to my abilities and interest in the experimental side. When I showed up at Princeton as a postdoc, there were two experiments going on. One was the most famous one, namely looking at the microwave background and trying to establish that it was cosmic. And the other was measuring the shape of the sun, because Bob Dickie had a theory that would call on the sun to be somewhat oblate, squished in its properties. So I went down to look at the solar abladeness experiment, a whole room full of electronics. Too complicated. I went to look at the microwave background.

There was a horn, went into waveguide. I knew about wave guides. Went into a detector. I knew about detectors. So I signed up for that. There was this sort of search for simplicity and stuff that I thought I could do. And those early experiments when reputed, what year did you arrive at Princeton as 65? It was right around the time of the three months after the paper was published that established the microwave background.

So it was early days. Now, I've read that paper, you know, many times, not, not, and the companion pay, I always call the Penzi and Wilson paper, the companion paper. Because the companion, the Penzies and Wilson paper is only, I think it's less than a full page in the App J. It's very short. I mean, they were being very careful. I said, yeah. You found this signal. It's as though everywhere we look, we're looking at a surface of three degrees above absolute zero, not zero, but three degrees above.

And they didn't interpret it. The crucial moment, as you just pointed out, was the interpretation that this is the heat, cool down heat left over from the Big Bang. And that was in the Dickie People Roll in Wilkinson paper that you probably probably million times as I have. That one is incredible. And many times when I read it, I point. out it doesn't nowhere do the words Big Bang appear, but instead the collapse from a previous epoch appears almost as if they kind of thought that it might be more likely that there was a obviously formation of the nuclei, but they didn't necessarily believe that it was the origin of time

or perhaps something like that. Take us back to that year, that magical year in cosmology. We're coming up on the, what, 60th anniversary? I can't believe it. Oh, close to it. Yeah. Yeah. So tell me, what was that? You were roughly speaking. What was going on the zeitgeist, the spirit of the times back then? So going back to the 60s, there were basically two competing theories. Other speakers in this series may have mentioned that, but one was steady state in which the universe was always the same, everywhere the same and always the same.

And in order to keep the density of the same electrons and protons up out of nothing. And competing with that was the Big Bang theory. The universe had a finite beginning. It just started. And the suggestion was, most proponents of the Big Bang Theory accepted this, it would also be a hot Big Bang. So those two things were in the air. And Dickie and his colleagues were in a sense trying to push them together a little bit

by imagining an infinite universe in time that simply cycled. It expanded, then it contracted, then it expanded, then it contracted. And that universe had to be hot for the following reason. In any one of these phases of the universe, stars make heavy elements. And after many cycles, you'd have nothing left but heavy elements. The universe would consist of nothing but iron and nickel. And it doesn't. So to get rid of the heavy elements, you have to have a hot big bang, which boils them away,

turns them back into their constituent neutrons and protons. So there's a built-in, you had to have heat in this model. And what's interesting was that the Brinson guys were actually setting out to find this. They had built a piece of equipment specifically designed to look for heat leftover from the Big Bang when the fateful telephone call came from these two guys. Excuse me, I'm just going to be informal. Hold up a picture here. Of course, no, there they are.

These are the two guys, Pendius and Wilson. and behind them the horn radio telescope that first noticeably detected the radiation. So they got in touch with the Princeton group, and the story repeated in your book, Brian, is that Dickie was meeting with his young colleagues. This is before, just before I got there, put his hand over the phone and said, well, boys, we've been scooped.

Benjus and Wilson had found a signal that looked like It might be heat left over from the Big Bang as Dickie and Company were predicting. Important is that the Princeton experiment was specifically designed to look for this heat, so very quickly, within a year, it had produced better results than Penzius and Wilson, and consistent with the original discovery. But, again, Brian, as you point out in your book, the Nobel Prize went to Penzias and Wilson, and not to Dickie and Wilkinson and Peoples. Well, People's got his later.

Yeah, that's right, recently. And People's, of course, is the co-author. And one of your early papers, we'll talk about that in a minute. But I've always found the saddest story, the saddest person in the whole affair was this guy, Ed Ome. Oh, I don't know much about him. But other than that, he used the very same horn antenna at Holmdel, which is a national historic landmark. And also did several of the same types. of experiments that use similar types of radiometers. But the one thing he was missing was a

internal calibrator that could check at rapid rates to get rid of the one over F signal. And of course, we know that by the name of your advisor as a Dickie switch. And so they employed that so the dicky switch really is the thing that, but Ed Olme is not blameless in this whole affair because if you go over his technical report in the Bell Labs telephone systems journal, which I read many times many years ago, he does a thorough error analysis, and then there's a three Kelvin term, and he accounts that to the atmosphere, to the antenna temperature, it's really not clear to me. I think Novakov and others later point also saw that term even before Penzi's and Wilson. So they're kind of a lesson that I teach to my undergraduates that error analysis seems

annoying, but it's very important you get it right. And that you account for all those errors. And that's one of the things that Penzison Wilson did very, very well. They saw this signal. They didn't say, we've seen a signal. I'm going to publish it in the astrophysical journal. They busted their butts trying to show that it was not radio stations from New York or pigeon poop in that horn, which would also radiate and cause a signal. They were very careful. Ome, I think, didn't make those same steps. And the Russians, who read Ome's paper, unlike the Princeton group, made the mistake of assuming that what Ome was seeing was the atmosphere. Where it wasn't, it was in addition to the atmosphere.

So, 1930s, cyanogens floated ground in space, kept warm by something. Nobody paid any attention. Ome, Desper Wall, did a radioistrored. experiment in which looking at the spectrum of emission from our galaxy seemed to show that there was a sort of additional term that he couldn't explain equal to 5 Kelvin. So there were hints, and I like to make the point that what changed from hints and so on to a prediction was that paper by the Princeton Group. they went out on the limb and said, this stuff is cosmic in origin. And then the next couple of years, Dave and I and other people, worked to try to pin that down by doing two tests, if I may go on for a moment.

Of course, it was the spectrum. That is, if there's heat left over from the Big Bang, you should get the same temperature, 3 Kelvin or whatever, at every single wavelength you measure. And we set up a series of experiments that proved that you did. and incidentally got a better value for the temperature. It's now 2.7 is closer. And the other is that if this stuff is left over from the beginning of the universe,

the beginning of the universe is everywhere around you. In any direction in which you look out, you're seeing back in time. So this radiation, if it's cosmic and original, to be isotropic. That is the same in all directions. Penzies and Wilson had checked to see that wasn't coming from New York City or Philadelphia or the center of our galaxy. But the limits they set on it, it's taught to be, whether it's the same in all directions, were pretty poor. And Dave and I recognize it with a fairly simple equipment, we can improve it by a couple of orders of magnitude.

And we get. Hey there, fellow Voyagers into the Impossible Tiz Eye, your fearful host. Professor Brian Keating here with a tiny little homework assignment before we get back to the episode. And that's that make sure that you're subscribed to the podcast, either following it or subscribing to it, depending on your podcast, catcher of choice. I did some research of my own and found out that only about half of you are actually following or subscribing to the podcast. So please do that. And for some extra credit, if you're looking to boost your position on the grading curve, please leave a rating or review. It really helps us out tremendously. Do it. Do it now. Before you forget, let's go back to the episode.

One piece of advice I'd love to get. We have a lot of young listeners, PhD students, even graduate students. I've been working in the field of CMB-B mode polarization for 25 years almost by now. And we have yet to see, well, we saw a signal in 2014, but of course we had to recant that signal now or the interpretation of it. It's still accurately measured, highly accurate and dominated by astrophysical, not man-made or earthbound systematic. So it's an incredible accomplishment. Still is the most sensitive measurement. How did you go through the years?

So this is partially a question from one of your former students by the name of Professor Stefan Alexander. And I asked him for a question for you today. And he asked me, essentially, how did you have the sort of courage or how did you have the patience to do the first sorts of antisotropy measurements as you did, to see if it was isotropic and not really see fruition until, David Wilkinson and George Schmoot and others measured the antisotropy convincingly. I would say the spectrum was known by you to be very close and others to BlackB or it was

very easy. But the antisotropy was completely upper limits after upper limits for almost 30 years. How did you have the courage and patience to deal with that? Give me advice to kind of keep patient. Because it's been longer since between the detection of the CMB and its first antisotropy than it has been from its first antisotropy to measuring B-Mote polarization. How can I have patience or what can you advise my students and I to do in terms of coping with decade after decade perhaps of upper limits?

When do we give up? Don't. This is the one word advice. But remember, back in the 60s and even into the 70s, the idea was not defined antisotropies because, frankly, we weren't listening to the theorists and didn't really understand how rich the field of antisotropies could be. Instead, it was a different aim, and that is to show that the radiation was, in fact, isotropic. It's easy to imagine, let's say, starlight being thermalized by dust and emitting at the three Kelvin level. It's easy to imagine, indeed it was suggested by many

people, but that would tend to be brighter towards the plane of the galaxy than perpendicular to the plane of the galaxy. So our aim was not initially to find anisotropies, but not to find them to set better and better upper limits. And if I can hold up another thing here, here's a plot. This is, again, this is rather informal, but a plot of measurements of temperature. And you notice the scale over here is in thousands of the Kelvin. Yeah. And this was a very crude experiment. with lousy dicky switching, which we set up first on a tall building of the Princeton University campus and then realizing that New Jersey weather is not ideal.

We took it out to Arizona and ran it. It was run remotely for a couple of years. The Arizona location involves some interesting stories. De Wilkinson discovered that Yuma, Arizona is the sunniest place in the United States. I discovered through my military father that there was an army base there. It's right. Proving ground. The Yuma Proving Ground and further research showed that there was a very secure area

where we could put this piece of equipment about the size of a small hut out in the desert and not have it bothered. And it was secure because the Army was busy testing nerve gas shells. The idea was you build big wooden racks, put a bunch of nerve gas shells in and wait to see if they leak. Needless to say that area was fenced and patrolled. So I shouldn't feel bad about sending my graduate students to Chile for three weeks with their active minefields. We were issued gas masks and we were told that there were certain physiological signs. And if you noticed those, it was probably too late to put on the gas mask. So instead, the monitoring system was rabbits.

I promised you to talk about the rabbits. Yes. So the rabbits were stationed in hutches around these nerve gas shells. And the idea was if the nerve gas started to leak, the rabbits would die. Well, about halfway through our time there, the rabbits started to die. So there was a big fuss, all kinds of tests. We weren't allowed in for a while. It got quite complicated.

And it eventually turned out that the nerve gas wasn't leaking. But the army and its wisdom had bought three dozen rabbits all of the same age. So we happened to have been there at the time when the rabbits reach three score in ten years and we're beginning to crow of natural. What we were able to show is there's some scatter back and forth, but there are no excursions that are bigger than about a third of a percent of the microwave background. So no evidence that the radiation was coming from a particular.

place. Strong support for the cosmic interpretation by 1968. It's peak pollination season and my business is scaling fast. To keep the nectar flowing, I need a phone plan with top priority data speeds. That's why I chose GoogleFi wireless. My connections stay strong even when the hive is buzzing. Plus, unlimited plans started $35 a month. Now that's a deal that doesn't stay. Explore Google FiWireless plans today. Plus taxes and government fees. GoogleFi wireless is not subject to data traffic deprioritization during times of high network usage. And the original paper, Penzies and Wilson and subsequent ones by by you guys at Princeton, the topic of polarization was broached, actually,

as early as in 1965, Penn Zies and Wilson set a limit of 10% or unpolarized below 10%. And then in In 1967, I believe it was, Martin Rees, Lord Martin Rees now is a three-time guest on this podcast. He came out with a paper that suggested the CMB could be polarized. In fact, it could be highly polarized. And that was based in the model that the Big Bang or the Hubble expansion could be anisotropic. It could have an isotropic to it that would generate a quadrupole moment in the photons. So it would be a huge quadrupole moment in the... CMB's antisotropy, and that would generate a large amount of polarization. And I like to point out

when I talked to him that, you know, he was right, but for the wrong reasons. But that that actually has a lot in common with a lot of what science is about. For example, Galileo believed that the Earth orbited around the sun. We know that's true. But he used the tidal pattern of the Earth's tides as a piece of evidence for sloshing and swirling of tides and has nothing to do with that. So can you comment on, you know, how sometimes incorrect theories can generate useful scientific tests and sometimes detections? And obviously I'm going to pivot to inflation and dark matter and string theory in just a bit. But talk about how much should an experimentalist listen to a theorist? My first answer would be in this field, at least not enough. And I'll come back to that.

But first, let me talk about the polarization business. The detector that Dave Wilkinson and I used was intrinsically polarized. So had there been a huge signal in polarization, we would have seen it. In addition, in Reese's paper, in order to make a big polarized signal, not a tiny one, you have to have an anisotropic universe. And that would have resulted in a sort of dipole, potato-shaped, sausage-shaped temperature distribution. in the sky, which we didn't see. The polarization that we do see now is from a much subtler effect.

There is a small quadruble moment, which we do expect, and that produces the roughly tens of a percent type polarization that we detect in the migraine background. I said earlier that we should have listened to the theorists a little bit more. Because so many of the early people in this field came out of Bob Dickie's group and Bob Dickie was an absolute master at null experiments, showing that such and such was smaller than certain value. The time rate of change of the gravitational constant was below one part and ten of the twelve and so on and so. A lot of our experiments were designed to be null experiments, and we weren't particularly interested in finding something,

and we didn't particularly pay attention to the theorists who were telling us, If you're looking for small variations in the temperature, you ought to be looking on scales of the order of a degree or below. And that's reflected in the design of the Kobe satellite, which you know about. The experiment that won George Smoot, his Nobel Prize, was consciously designed to look with small changes in temperature of different parts of the sky, but at the wrong scale. At 10 degree scale, instead of 1 degree scale, we could have done much. much better might even have found the antisotropies earlier had the experiment been designed better and had George and the rest of us listen to the theorists. We were busy trying to get lower and lower limits.

Yes, it's natural to do that. I guess the question, you know, that comes up all the time with me and there seems to be, obviously there is groupthink in any organization of individuals just because they have incentives to maybe combine or be related to those in their field that are setting the trends and so forth. So nowadays, you see a lot of more string theorists than people looking at things like loop quantum gravity or some other alternative that could be plausible. So, too, I worry that there are an awful lot of people invested in inflation. And I wonder, are there parallels that you see as an observer both then and now between the

dominance of a theoretical paradigm and the cultural pressure for young people to go into that field, either as experimentalist in my case or as theorist in others' cases. I don't buy the argument about the social pressure. There's a sort of standard view. Yeah, inflation is important. And of course, it is consistent with a lot of things we're finding, including isotropy. But when I read of a new experimental result, my very first reaction is, how can I show this is wrong? Can I do a simple experiment to show that it's wrong? I'll give you an example. I will send a paper to review, which claim that because of some complicated theory, there had to be a strong antisoptery in the gamma-ray background.

So I did the calculation and discovered that if I simply held up a plate full of raw eggs, the gamma rays of this guy was predicting would be present, would cook it instantly. I think a lot of us have that sort of skeptical, how can I show this is wrong attitude and are not terribly hidebound by the sort of prevailing orthodoxy, let's call it. And you look at your advisor, Dickie, I don't think he gets enough credit for the contributions. First of all, he was an exemplar of what I think of as the paradigm of a physicist. like a Fermi or a Galileo in that he knew the theory and he could do experiments too. And that's extremely rare. We'll talk about later your philosophy on pedagogy. But one of the things that

Dickie contributed to the theory of inflation was, I think he pointed out, and correct me if I'm wrong, to a young Alan Goose that there was this, you know, kind of cosmic coincidence of the flatness of the universe. Not knowing that it was exactly flat, but knowing it was within an order or magnitude of being flat. Can you talk about that, that kind of those notions and why it wouldn't be inflation that I would first think to sort of want to explain? It would be probably the missing, you know, barons or missing matter. What made that stand out so much to your advisor to Bob Dickey?

If you can speculate, obviously he's not here anymore. I will have to speculate, but it's the following. take two parts of the universe that are very far apart. Suppose one part of the universe wants to tell another part of the universe what to do. For instance, point A wants to tell point B what temperature to be. That information can't travel faster than the speed of light. So, on very large scales, there's no way that one part of the universe knew to be 3 Kelvin and another part of the universe needed to be 3 Kelvin,

unless it was an initial condition. And you don't like initial conditions. You don't like to have to say, well, a universe started out in just such a way that it's now 3 degrees Kelvin. So how do you explain that? And that worried Dickie. He was worried about that.

He was worried about Mox principle and some other things that have to do with these large-scale properties and puzzles in the universe. And what Alan Goose and company did was basically to explain it. And that is to say that at some earlier time the universe was so small that regions that are now too far apart to talk to each other were perfectly happy in confabulation early on. And then the universe expanded exponentially, which we call inflation.

So the fact that the, back to this picture, which I keep shoving. Yeah. This picture shows you that the universe is pretty much the same in all directions. Well, how did it know on a large scale, but be the same in all directions? It had to be in contact, causal contact, to use a technical word at some early time. And that's what's behind inflation, is to get that done. Going back to the same year in 1967, I pulled up a paper, which is still getting citations from a young Bruce Partridge and young Jim Peebles. And it's called Are Young Galaxies Visible?

And you talk about the purpose of this paper is to assess the general population possibility of observing distant, newly formed galaxies. To this end, a simple model of galaxy formation is introduced. And you talk about star forming and their luminosity. And then you say these bright phases would correspond to an epoch of a few tens of hundreds of millions of years, corresponding to a redshift between 10 and 30. I want to talk about recent so-called claims or discoveries or controversies, as our British friends might say, regarding the seeming observation of very mature galaxies at very high redshift, much higher than ever anticipated. And for this, I am old enough that I can actually remember the controversies that similarly seem to erupt after the Hubble Deepfield was released in 95 or so. that was in the middle of my graduate student career beginning of it. So I want to ask you, what do you make of these findings and controversies? I mean, are they just not reading your paper?

This paper that you wrote, in other words, these scientists are saying that the universe must be much older than we previously thought, possibly even eternal, because the galaxies that we see are two highly organized grand designs and spirals and so forth. You showed almost, again, 60 years ago, 54 years ago. that this was possible. What's going on here? Okay, well, this goes back to the previous discussion where we talk about a sort of orthodoxy. The orthodoxy these days on galaxy of formation,

it's probably correct, but let's question it, is that galaxies are built up by mergers of little things. So you start with a bunch of little things, they merge together, that blob merges with another blob, and pretty soon, you've got a galaxy. The problem is that you've got to do that really, really fast, to explain mature galaxies very early in the history of the universe. Approach that Peebles and I took was very different,

and that is a blob of gas of galaxy, galactic mass, collapsed in on itself and started to form stars. So you went from nothing, or relatively smoothly distributed gas, to a galaxy, not by merger. Maybe there was something in that, after all. Maybe that's how these mature systems do form. It's always interested me that the way, way you find that a galaxy is at large redshift and is star forming is to look for a sharp

discontinuity in the spectrum introduced by the Lyman Breit, which is in that paper. What may be going on is that galaxies form in special places, more like the Partridge People's model, but not universally, and that mergers are responsible for most galaxies, but not the ones that the is finding, or that these galaxies look bigger and more massive than they actually are. And that is a possibility. But it is sort of fun to argue with the conventional orthodoxy, because if you start with things that are, let's say, a million times of mass of the sun, you merge two of them, you get something that's two million times of mass of the sun.

And then you have to merge again and get something that's four million times of the sun. mass of the sun and then eight million. And how do you get something that is pushing a billion times the mass of the sun in the time that's alive? Your summer starts now with Memorial Day deals at the Home Depot. It's time to fire up summer cookouts with the next grill four-burner gas grill on special buy for only $199 and entertain all season with the Hampton Bay West Grove seven-piece outdoor dining set for only $499. This Memorial Day get low prices guaranteed at the Home Depot. While supplies last, pricing invalid May 14th or May 27th, U.S.

only exclusions apply. See Home Depot.com slash price match for details. You're, uh, have more on the iconoclastic or Maverick side of things, which is yeah, enjoy it. Yeah, which is, which is fun to do, but it's, it's tough to, first of all, you have to have the prerequisites to get to that level. And I feel like these guys that are criticizing or. saying the Big Bang never happened, like Eric Lerner and even Rajendish Gupta at University of Ottawa,

you know, published the universe is 26 billion years old. They all sort of relearning on, you know, kind of a series of just so stories, but they can always point to flaws in the, in the Big Bang, especially in the early universe cosmology, because every model will have its lacunae. And I think, obviously, you know, the Big Bang does too. I would say of all the ones that are pointed out by Lerner and Gupta and others, the one that still is sort of in question that I'd like to get your take on, although, you know, I don't think this has been a field of study for you, but it's the lithium abundance problem,

that there seems to be the largest gap between predicted abundances in the BBN, you know, kind of taxonomy and observed. the biggest one extant is in lithium. Can you talk about that? Is that something we should be concerned about? Or is this just messy nuclear physics that the guys that operate, you know, giant vandigraphs will someday figure out? What do you make of the lithium problem?

As this proves, the Big Bang never happened. I think it's a very weak read on which to claim that you've disproven the Big Bang. Just to set some context. The early universe starts out. It's hydrogen, neutrons, a little bit of helium, and a tiny, tiny amount of lithium is produced as a sort of byproduct. But lithium is a fragile nucleus. It can be made in cosmic ray interactions.

So it's not all that convincing as a proof or disprove for the Big Bang. The Deuterium abundance, on the other hand, is very important. And what's interesting to me is that nuclear physicists, guided by people like Jim Peebles and Bob Wagoner, we're predicting how much deuterium and how much helium should emerge from the Big Bang, and we discover exactly that amount. And the amount of deuterium is consistent with a very small amount of ordinary matter in the universe, which the microwave background also emphasizes.

So lithium is sort of a, to me, a side issue. It can be made, and can be destroyed in stars, So it's a little, again, just a weak read on which to undermine so much other observational evidence. On your website, which we'll link to in the video description below, you have a nice discussion of the research interests that you have had and maintained. And it concludes with one statement that careful measurements of these C&B fluctuations, both from space and the ground, have turned cosmology into a precision science. I had Mike Turner on, how I know you know, and he said, not about you, but he's famous for saying, you know, precision cosmology is nice, but accurate cosmology is better.

I wonder if you can talk about, are there things that are still outstanding, maybe not mysteries, but there's further research in areas of the CMB that might be considered to have been a closed book? And I'm thinking about distortions. I'm talking about Compton Y. I'm talking about chemical potentials. Are there still things of interest that a young student might be able to contribute to in that particular field? Yes, I think so, both in terms of spectral distortions, which is what you're mentioning. But to me, much more interesting in a sense is pushing harder and harder and harder on the visible antisotropies. if I can just scoot aside for a while.

Here's a map of the sky. And these regions of red and blue are slightly higher and slightly cooler regions of the microwave background. Studying those has proven to be an absolute bonanza in terms of refining cosmological theories. As an instance,

if you look at that picture carefully, you'll see that this quite a lot of structure at roughly the one degree scale. Yeah. Less at two degrees and less at a half a degree. Well, why should that be? Well, it turns out that that is exactly what you expect from the size of the universe at the time we're mapping it, provided the universe has a flat spatial curvature and not otherwise. So simply finding where the peak is in terms of the distribution of fluctuations tells you about the curvature of the

universe. You've already mentioned the B modes. We're looking for those. At the small scale end, the way structure forms in the universe can distort the microwave background fluctuations a little bit, not much. But because the measurements are now so good, we can put constraints on things like the speed at which gravity pulls matter together to make galaxies and so on. And there are, fortunately, for young people in the field, still some interesting tensions. You probably talked about this before, but if you ask how fast the universe is expanding, if you'd ask that question in 1960, you'd get two answers from two warring groups, one claiming it was expanding twice as fast as the other.

And it got to the point where if you ever had a meeting dealing with cosmology, I'd invite one person from each group where they'd get p-oed. Now, the debate is between the supernova guys who are claiming a number that's about 10% different from the number that Brian and the CMB folks are claiming. I don't think we're at the point where you have to have one from each school at each cosmology rule, but there's a real tension there. The difference between 67 and the standard units and 73 in the standard units is three or four times the error. So something isn't right somewhere, and that needs to be sorted out. And the rate of growth of structure, how fast gravity pulls things together, is also somewhat in dispute. Maybe.

Or Mark DeBry. This is the S-8, Sigma-8, top of growth. So there's still work to be done. Yeah. And I see that as yet one of many tensions. And I just had the opportunity to visit my alma mater, which is Case Western last week. and I met with a friend of mine who wasn't a professor until a couple years after I graduated, and that was Glenn Starkman.

And he is making a very convincing case that based on that image behind you that you helped to make, I believe that's from Plank. And you were a WMAP, I'd say, but. Oh, that's WMAP. Okay. Plank did the very, very upgraded and beautiful and complimentary and also in strong agreement with the WMAT map. So there's Plank. Yeah, it's good.

I'm partial to WMAP because it has my grand advisor's name as the first, and I'm sure your friend, David Wilkinson, is nice to be located in L2. I pointed out, he'll probably be orbiting the universe forever, his namesake instrument. But Glenn has pointed out that if you take that image behind you and you put it, that's in galactic coordinates, I assume, but if you kind of rotate it 45 degrees, it turns out it's an ecliptic coordinates. And he says that if you take and you make a power spectrum of our correlation function, not a power spectrum, but of the data in the northern ecliptic hemisphere and you compare it to the southern ecliptic hemisphere. And this was pointed out by our good friend David Spargel back in

2003 from those data behind you. So I know that for a fact, that there's an asymmetry. There's a big asymmetry between the statistical properties of the north and south hemisphere. Barely visible here. but this looks a little redder than up there. That's exactly right. And there are things like the cold spot. Interestingly enough, the axis of evil, so we'll talk about that in just a second, but the cold spot is in the southern ecliptic hemisphere, and that seems to agree with what you'd get from a Gaussian random simulation based on Lambda CDM.

But the north isn't. The north you only get in, if you account for everything, I think with the latest plank data, Glenn student, and Joanne was showing me this last week, there's only a 0.02% chance it arises at random. If you've been around this a long time, what do you make of these kind of these asymmetries? Are we trying to demand too much of this Big Bang bonanza that is the CMB?

Is it really fair to ask for it to be accurate and precise at the 200th of a percent level? That may be pushing it. And again, as you well know, the sort of standard explanation for the hot spots and the hemispheric asymmetry is basically goes back to playing poker. Any given hand that you're dealt is highly unlikely. I mean, not just a royal straight flush, but two of spades, a three of clubs, blah, blah, blah. Any particular thing is unlikely, but it has to be something. Yeah. And so some of that 0.02% is covered by cosmic variance.

Just the universe happens to be that way. So it doesn't keep me up at night. Well, I would love to see someone actually improve the measurements or figure out how to beat cosmic variance to see if there's something that's statistically odd about the microwave background at large scales. So again, I'm like kind of clasily, but not losing sleep over that. unlike losing sleep over the rate of expansion of the universe and the growth of structure. Those worry me. Are there other explanations that you prefer for, say, explaining the Hubble tension? I'm quite partial, and I want to explain my reasoning because I'd love to get your opinion

as one of the heroes and legends in the field. But my philosophy of experiments and even theories is that you should always do very extremely risky science on the one hand with one of your hands. But the other hand, you should do something that's known to exist and known to be there such that the whole thing is not an empty pursuit. I always laughed when my colleagues in high energy physics down the hall would say the most exciting thing we could discover with the large Hadron Collider is nothing. And I would say, yes. And then you will discover unemployment. So it was a big gamble. But it was also safe, on the other hand, that we sort of had a good idea. I like to do searching for the cosmic microarray backgrounds B modes

because they may be there. It's extremely high-risk science. They may not be there, even if inflation took place. And then on the other hand, I like to do very low-risk stuff. And one of the topics that you've worked a lot on when you are with the ACT team folks, and you still are contributing member that many of their papers, is look for the mass of neutrinos. I want to ask you, sorry to keep saying. I was going to say as a legend, I'm going to keep saying, stop saying that. I'm just to say, as someone who's been in the field for a long time. I'm not yet. As an observer of this field for a very long time, let's say we are successful, we meaning us on the Simon's Observatory, and we measure the mass of cosmic neutrinos

for the first time ever. We have lower limit, we have an upper limit, we don't have a detection. Will our colleagues in high energy physics department circles, will they believe us, Bruce, based on your knowledge of history and thought of the philosophy of this field? I think frankly it's touch and go unless it's a really clear measurement. Going back in the history, one of the things that you can use both cosmic nucleus synthesis, say the formation of helium and deuterium in the early universe to tell you is the number of neutrino species. And it was not clear whether that was three or four or five back, let's say, in the early 70s.

Dave Schramm and others interpreted the astrophysical data and said, no, it's got to be three. Eh, I wasn't clear that anybody believed that. We now know that it's 3.05, roughly speaking, so it's not four, it's not five. A little bit later, I use the astrophysical data, just pure CMB and some other stuff, to point out that the lab measurement of the lifetime of the free neutron was not right, didn't agree with the astrophysical data. To say that was a stone that sank without a ripple would be an understatement. But later the lab experiment showed that I was right and so on. So it takes a lot of effort. If we publish a, let's say, a three sigma measurement that the neutrino mass is

0.057 plus or minus 0.02. Will people get up in arms about it and try to improve the the lab experiments to justify this or to confirm it, I don't know. There are people like Mike Turner who work, and many others, who work at the interface between cosmology and particle physics, who I think would take it seriously. But whether your colleagues down the hall who are big accelerator guys will, I don't know. I hope to do the experiment. That is, I hope we come up with this number and publish it and say, there it is, guys. Bruce, before I have to go and teach myself, I want to ask you about pedagogy.

You are one of the best educators, not just like cosmology, but you're dedicated to your life at a predominantly undergraduate, at an undergraduate serving institution that's had a host of eminent scientists come out of it, out of your classes, and you have sort of revolutionized and enhanced the teaching of cosmology at the undergraduate level. I want to ask you about your theory of pedagogy, and in the following sense, I teach a lot of undergraduates, and I teach graduate students experimentalists. I've had a few theoretical, you know, graduate students who are only doing theory, not experiment. What is the theoretical minimum, or shall I say the experimental minimum? What should an experiment, a theoretical graduate student know about experimental physics or experiment, let's just stick to cosmology? What should he or she know? starting off, she's really excited to come up with an explanation for the hemispherical asymmetry, the some sterile neutrino signature and the CMB, a large extra dementia.

But what should she know about experimental astrophysics before she goes and does everything she's going to do in theory? I would say that the main lesson to take away, and I harp on this when I talk to theorists, is just how damn difficult these experiments are. They're not easy. You have a big piece of equipment, the size of your lab or bigger, sitting at a temperature of 300 Kelvin, and you're trying to make measurements of the order of 10 microcalvin with that piece of equipment. It's not easy, guys. Given that, theorists pay real attention to the issue of systematics and instrumental effects.

Don't leave that to the instrumentalist. Think about it yourself. If I see a signal, suppose I suddenly discover a hemispheric asymmetry. Are you really sure that doesn't have to do with the way your instrument is designed and the fact that it happens to be in the southern hemisphere and not the northern? It may be that the answer is okay, but think about it. That's what I would tell there is. We always end with a comment from the guest on a quote from Sir Arthur C. Clark,

who is the namesake of the foundation that endowed the center that, that I'm affiliated with here in San Diego, the Arthur C. Clark Center for Human Imagination. And Arthur, good old Arthur, I don't know if you ever knew him or met him. I didn't. I've read his books. Yeah. So he had many, many quips and sayings, one of which is the only way to know the limits of the possible

is to go beyond them into the impossible, and that's the origin of the name of this podcast. Another one that I like to use on my colleagues who think too highly of themselves, is he used to say, for every expert, there's an equal and opposite expert. But the question I want you to comment on is the following. He said, when a distinguished older scientist says something is possible, he or she is very likely to be right.

But when he or she says something is impossible, they are very much likely to be wrong. But I want to ask you, not if you agree, but rather, what have you changed your mind on in this field of cosmology? as our final question, have you been wrong or have you changed your mind about something that you held very firmly in your youth? And yet, change came to your mind. The business of galaxy formation. We had, Jim and I had a particular model in mind. And most people don't believe that. So I've been sort of forced to change my mind, although I haven't

really given up on it. The other is dark matter. When people started talking about dark matter, It seemed to be absolutely and totally ridiculous. Stuff that we know nothing about somehow is important in the universe. And I simply refuse to believe that, despite all a good work of Vera Rubin and people like that, showing that it probably, there is something out there. And what finally got me to believe in it was a bibulous conversation with Jerry Ostereriker, drinking beer on a boat in Lake Ontario. And he said, Bruce, Goddammit,

if you don't see fluctuations at a level of at least 10 to the minus three in the microwave background, it's all over. Well, I'd already done an experiment throwing the upper limit was less than that. So what was going on? Well, what's going on is that the fluctuations in the microwave background are produced by the barons, and the gravity is mediated by the dark matter. So the dark matter can be happily gravitating away. and not make the fluctuations that Osteriker insisted we should be seeing.

So in a sense, my own work came up behind me and kicked me in the butt. Maybe that's a good play to say, and this. Well, I want to thank you for many things, not the least of which is inspiring me as a young graduate student with that wonderful book, 3K with that horrible cover. But you made up for it with your book with Jim Peebles and Lyman Page, past guest on the podcast, finding the Big Bang.

We'll put a link to those books in the show notes. And Bruce, I just want to thank you from the bottom of my heart for being an exemplar of what a good cosmologist should be and being a mentor and through all your years of service, which we also didn't get to talk about. Maybe we'll do this in person someday, part two. But Bruce, thank you so much, and I hope you enjoy the rest of your weekend.

Thank you. And let's join in thanking the Simon's Foundation. Absolutely. Thank you, Bruce. Ball. Pay off your home. travel for life drive a Ferrari. In celebration of the world premiere of the Monopoly

Big Board Buckslot Machine by Aristocrat Gaming, Yamava Resort and Casino at San Manuel is giving one person a $1.6 million dream package. The biggest prize in Yamaba's history. Club Serrano members can earn daily instant prizes and secure a spot in the finale May 29th. Don't pass go and own it all. Only at Yamava, celebrating its 40th anniversary.

You win? Details at Yamava.com must be 21-20. Please gamble responsibly. Monopoly is a trademark of Hasbro. Hasbro is not a sponsor of this promotion.