Andreas Albrecht
QMAP Logo
Description:
Andreas Albrecht is a professor of theoretical physics and the director of the center for quantum mathematics and physics at the University of California, Davis. His research focuses on the field of cosmology, which includes fundamental questions about cosmic inflation, dark energy and the formation of cosmic structures. In this episode we talk about a wide range of topics in physics from defining quantum states to explaining the origin of the Universe. Professor Albrecht shares the beauty of studying some of the most abstract and theoretical topics in science and how modern technology is opening the door to new breakthroughs.
Websites:
Center for Quantum Mathematics and Physics (QMAP)
Publications:
Cosmology for Grand Unified Theories with Radiatively Induced Symmetry Breaking
Holographic Bounds and Finite Inflation
Quintessential Cosmological Tensions
Cosmic Inflation: The Most Powerful Microscope in the Universe
Resources:
Professor Albrecht's Youtube Channel
UC Davis Cosmology Meetings and Seminars
Courses:
Show Notes:
[0:00:01] Introduction and Background of Professor Andreas Albrecht
[0:04:05] The Concept of Uncertainty in Quantum Physics
[0:07:37] Overview of the History of Quantum Physics
[0:10:40] The Weirdness and Challenges of Quantum Mechanics
[0:12:18] Two camps: Embracing multiple outcomes vs rejecting multiplicity
[0:16:07] Visual interpretation of multiple worlds, personal perspectives, and philosophy
[0:19:23] Quantum computers bring different worlds together for parallel computing
[0:23:08] Overcoming Separation of Worlds: Engineering for Reunion
[0:27:48] Exploring Quantum Cosmology: Understanding the Universe's Origins
[0:28:55] The Observable Universe and its Size
[0:38:10] The Success of the Big Bang Model
[0:41:51] Exploring the use of microwave antennas in telecommunications
[0:46:04] Cosmology: Datasets and Public Analysis
[0:54:21] Exploring the Many Meanings of Multiverse
[0:56:54] Energy Conservation in General Relativity
[0:58:03] Tempted to Explore Different Perspectives
[0:58:18] Gravity as Curvature of Space-Time
[1:02:14] Metric: Shape of Space and Curvature of Spacetime
[1:05:53] Exploring Dimensions: From Four to Nine?
[1:09:29] Defining Matter and Antimatter in Quantum Physics
[1:18:13] The Arrow of Time and Entropy
[1:22:22] Pondering on Interrelated Mysteries in Physics
[1:24:16] Embracing Failure as a Learning Experience
[1:25:26] Reflecting on Failure and Learning from Mistakes
[1:28:33] The Vision and Growth of QMAP
Unedited AI Generated Transcript
Introduction and Background of Professor Andreas Albrecht
Brent:
[0:01] Welcome, Professor Andreas Albrecht. Thank you for coming on today.
Andreas:
[0:04] Yeah, I'm happy to be here.
Keller:
[0:06] We'd love to start off by hearing a little bit more about your story.
How'd you get to Davis and what got you interested in quantum physics?
Andreas:
[0:13] Oh, there's a lot to that story. Where, how do I start? I, I, um, well, okay.
I, I, um, in high school, my big dream was to be a professional violinist.
That was my thing. I worked very hard, practiced many, many hours a day.
And then I took my high school physics class and it just turned me around and I just became really excited about physics.
I think it was taught differently than my other science classes.
I hadn't been that excited by science before, but it was taught a little differently.
And I think something about physics itself, you could work on problems that once you got the answer, you knew you had the right answer and you could think all you wanted about it.
A lot of other science classes were taught, at least at the, you know, these lower levels, was more kind of multiple choice, sort of learning lists of facts and there's sort of ways you can getlost in that and it doesn't feel that solid.
So I really just liked what it felt like to study things from a physicist's point of view.
And then quantum physics actually, yeah, you had mentioned that in your questions.
[1:32] I actually found my way to the back of it. So, quantum physics wasn't covered in my high school class, but there was something in the back of that textbook about it, an appendix oran extra chapter or something that we didn't cover.
And I became really fascinated with it. And I think, so that really was already the beginning of my fascination with quantum physics.
And I think the way, probably the way to describe what it was like is that the guys who discovered quantum physics, they weren't necessarily trying to create a revolution.
They were just trying to understand these stupid atoms that weren't making sense with the physics that they knew. They were just trying to fix that.
But they ended up creating a revolution. And I like that mix of, you know, methodical tools, just trying to get to the bottom of things.
And sometimes that can just totally blow your mind.
Brent:
[2:27] Pete Certainly. So, could you describe what quantum physics is and then also maybe link it back to what, how it differed from those original problems that it wasn't able to fullyexplain how these atoms interacted or? Yeah, so.
Andreas:
[2:48] Quantum physics is a different way of describing the matter and the energy in the world.
We're used to there being hard facts, so the table is the table, it's right here.
Quantum physics deals fundamentally in probabilities.
[3:08] So if you ask from the quantum physics point of view, where is the table?
Well, maybe it's here, maybe it's there, maybe it's somewhere else.
Now, for actual tables, we think quantum physics describes everything now.
It was a hundred years ago, it was a radical thing and no one was quite sure where it was going, but now we think it describes everything.
And so it's just the quantum physics prediction for the table is very, very sharp, very narrowly predicted to be right where we see it.
But as you get down to the atomic scale, the probabilities get very vague.
And so, when you ask where is an electron in the atom, it's all over the place.
And there's still mathematically concrete things you can say about the way it's all over the place.
And it could be sort of this distribution or that distribution, but it's a very different way of talking about matter and a certainly radical thing.
The Concept of Uncertainty in Quantum Physics
[4:05] The other piece, so that's one piece of it, And the other piece is that certain things we take for granted, like you can take an object like this cup, and you know exactly where it is andexactly how fast it's moving.
And that's something if you've taken any physics class, you've probably seen equations like Newton's laws, that you assume that kind of thing.
[4:31] So for motion, we fundamentally talk about momentum.
And in quantum physics, the momentum and the position of something can't be perfectly specified together. And that's known as the Heisenberg uncertainty principle.
And that's a radical thing too. Like, you know, if I have, if I throw a ball, I got to know where it is and I got to know how fast I'm throwing it.
And that'll, we do that. But again, when you get down to atoms, um, there's a lot of uncertainty about where something is and how fast it's moving.
And that seems to be the foundations. So, so all these things like the balls we throw and the table we put things on are all made out of quantum objects.
Actually, one of the, one of the curious things is exactly how all that weird quantum stuff hides away when, when we build balls and tables out of it.
Brent:
[5:29] Yeah, and then When we talk about uncertainty at the atomic scale Are we certain that the electrons are somewhere in that atom but with where within it were uncertain.
Andreas:
[5:43] Or to an extent? Yeah, so there's a mathematical description and the further you get from the atom, so if we're talking about a single atom, then the further you get from the atom, themore sure we are the electron's not there.
But it's never a perfect certainty.
So there's a tail to the distribution.
But when you make certain kinds of like metals out of atoms, you lose, the atoms get less and less associated with the given nucleus.
So all kinds of other things can happen for other materials.
Brent:
[6:23] Yeah. And that's how electrons can like flow through metals?
Andreas:
[6:26] Yes.
Brent:
[6:26] Okay.
Andreas:
[6:26] And it gets even more, so if you've heard of superconductors where electrons can flow without resistance, that's a quantum effect where the quantum state of these electrons gets sodisconnected from the normal classical picture that they can flow with ease.
Brent:
[6:46] Yeah. And then a quick definition, what does it mean to be quantum?
Because you said, oh, everything's made of quantum objects. So, what is that?
Andreas:
[6:54] Yes. So, really, when I speak that way about it, I'm talking about things that obey the equations of quantum mechanics and things that, therefore, can most fundamentally bedescribed.
Only through probabilities and only with things like momentum and position not being specified together with perfect precision.
So these properties, so they can only, the fundamental understanding of matter as we know it is described by equations that have these properties.
They're about probabilities and they don't let us specify things like momentum and position together.
Overview of the History of Quantum Physics
Brent:
[7:37] That makes sense.
Keller:
[7:38] Pong And before we keep going, could you give a brief overview of, I guess, the history of quantum physics in terms of when was the idea first brought out and how did it becomepopularized? Where does it kind of stand now?
Andreas:
[7:51] Daishi So I would, I'm not gonna, I'm not a great historian of science.
I'm not, there's something I could help you look up and get the exact dates right and all that.
Ago, people started realizing, a little more than 100 years ago, people started realizing, there was something wrong with physics as we knew it then applied to the atom.
And there was a sense that the physics as we knew it, the atom wouldn't be stable.
So, people knew the atom had a nucleus and they knew it had an electron around it, But why didn't the electron just fall right into the nucleus?
The physics of the time would have had that happen in no time.
So, it was really a mystery. And there were lots of pieces to that story.
[8:44] There's something called the Bohr atom, developed by Niels Bohr, which just guessed, what could be different?
How could we fix this? And it was really, in many ways, looked like a very rough guess, especially from the point of view of where we see things now, but it actually got some criticalthings right.
And so, that was the start of it.
People saw…so there's something called Planck's constant that's absolutely critical for our understanding of quantum physics.
When I say that position and momentum can't be determined together, it's Planck's constant that tells us the limits, that sets the limits.
Planck's constant was, we know it by the letter H.
[9:40] And the letter H comes from the German word for fudge factor.
And that's what it was initially.
So there were explorations of phenomena with photons, photons interacting with atoms, and something, they were developing a very rough theory of how this all fit together. And theyrealized they needed a number.
And they said, well, let's just call it H, the fudge factor.
And then that's turned out to be a really fundamental number.
So, it's sort of like a lot of things in physics, it came together in bits and pieces.
Brent:
[10:17] And then how close are we now to understanding all of these different aspects at a holistic level kind of meaning how many questions are still out there?
Andreas:
[10:32] So that is a really fun question because especially regarding quantum physics.
The Weirdness and Challenges of Quantum Mechanics
[10:40] So quantum physics is so different that.
[10:47] Even when it works really well, people have trouble swallowing the implications.
[10:55] And maybe you've heard of the famous Schrodinger's cat. The idea is that according to quantum physics, things can be in two different states at once.
A cat can be dead and alive, and so on.
And physicists, even though we know exactly what what equations to solve, and we know exactly how those, for many things, you know, so we can take some situation in the laboratoryand work out the equations and see that quantum physics is working wonderfully.
Physicists actually get pretty bent out of shape as a community, dealing with these weird, dealing with the weirdness of quantum physics.
Which is fun, part of the fun of that is that our culture as physicists is sort of we don't get bothered with fluffy talk because we can turn everything into equations and make everythingreally solid and focused and stay true to the pure logic of our theories.
But quantum mechanics is so weird that we can't stay true to just following the math and taking pride in the rigor of our work.
People get distracted by these sorts of questions.
Two camps: Embracing multiple outcomes vs rejecting multiplicity
[12:18] And we don't really know where that's headed. So there's sort of roughly two camps, two broad categories.
There's people who say, yeah, we should just believe the equations.
We should allow for different outcomes, different outcomes to coexist. So there's a, You know.
You know, we flip the coin and I decide, you know, heads, I get impatient and go storming out of the interview.
Tail, we stay around for three hours.
[12:56] We, you know, the so-called many worlds description would say nature has both of those stories to tell and they're both happening that was real in some sense.
[13:10] And that's more or less the camp I'm in.
And the appeal of that, so the obvious thing you could ask is, well, how come we don't notice the other part, right? So how come we don't, those two things seem completely disconnected.
And the thing is the equations actually have an answer for that.
So you can technically ask, what would it mean to communicate among those different worlds?
And you'd find out you couldn't. It's not that you couldn't, you absolutely couldn't, but the efficiency of communication would be so suppressed by physical processes that you really can'tcommunicate.
You can't have an awareness of these other worlds.
And so, for someone like me, that's really exciting that there's this mystery, but it has a technical answer that you can calculate stuff and say, okay.
And then by comparison, if you say, well, there's different worlds in the atom where the electron's either here or there, the communication among those worlds is really efficient, so youcan't think of them as separate worlds.
The electron's this big, mushy mess in the atom, and it's not in separate positions, going off in separate worlds. And so, something happens when you go from one atom to many atoms likeus.
[14:39] Changes things and changes the way the different worlds can communicate and all of that. So, so that's one point of view.
And the other point of view roughly is, oh, come on, that's just nonsense.
How, how, how can you possibly, you know, if like, if someone comes in and sees me calculating something and, and, and they say, what is all that stuff you're calculating? I'd have to say,well, most of the things I'm calculating are the things that could have happened, but didn't.
Like, why would you have a theory? Busy, like most of the work of quantum physics is to calculate the things that could have happened, but didn't.
But didn't to us, and then, you know, then you say, well, but they're happening out there in other worlds.
But that just seems so weird. Like, since when, you know, since when do hard-nosed, practical-minded people like physicists buy into that kind of nonsense, right?
So then there's other people who said there's got to be some better equations that don't make us tolerate all this multiplicity and everything.
And the interesting thing, from my point of view, is that people have been trying that for many decades and haven't found anything good, as far as I'm concerned.
So I think if someone could find something really compelling that did that, it'd probably be pretty hard to resist.
But quantum mechanics has stood its ground and it's not yielding to that kind of thing, at least so far.
Visual interpretation of multiple worlds, personal perspectives, and philosophy
Keller:
[16:07] Peter And visually, how do you interpret the idea of there being multiple worlds?
Or do you not interpret that in a visual sense?
Andreas:
[16:16] Pete Me, I'm not sure I have a good visual at the moment.
I'll probably, I've not been asked exactly that question, but I will say I take those other worlds seriously in the sense that I wonder, you know, different paths I've taken, different, youknow, things that have happened with people I care about, you know, kind of wonder, like, what it's like in these other worlds.
So in that sense, You know, I take it pretty seriously.
Brent:
[16:47] And it just seems like a quantum physics is a decent blend of somewhat philosophy backed by a lot of hard science and equations.
That's a very interesting thing to think about because those worlds are often separated.
Andreas:
[17:02] But is the analogy- We struggle with that relationship too because a lot of physicists don't want to admit they're doing philosophy.
They wanted to be all about solid equations.
But yeah, so each probably each physicist has their own their own perspective on how much philosophy they're ready to contemplate or how much they're willing to admit they're thinkingabout philosophy.
Brent:
[17:26] Yeah. and, if this, like, correct me if this understanding is probably wrong or not, but is it basically saying there's all these options on the table, but we are only able to observe one?
That doesn't mean the other ones aren't happening, but kind of similar to if you press play on the phone for this podcast, but you don't have headphones in and your volume's off, doesn'tmean the podcast isn't playing.
It's just you're not perceiving this.
Andreas:
[17:53] Pete I like that. I like that analogy, actually.
Brent:
[17:56] Yeah.
Andreas:
[17:57] Yeah. You're not perceiving it. And then there's another copy of you on the other branch not perceiving you.
So, there's this mutuality, like everyone's off in their world, but there's different copies.
So, like, we flip the coin and make that choice, both me's and all of you's.
So, actually, that's a good illustration. So, the thing that's not going to happen is, and this is something you can see with the equations, is it's not going to be where we flip the coin.
Like we share a world where I think it was heads and you think it was tails.
There's going to be the heads world and the tails world and the decisions we've made based on that going forward, but we're not going to get in arguments about whether it was heads ortails, at least if we've done a good coin flip.
And so, those options where you think, oh, everything's confused, nothing's solid, that's where it gets solid, is that when you flip the coin, we all agree what it is.
There's two copies of all of us. We all agree in each world.
Brent:
[19:04] So, in that standpoint, I guess visually it could be a lot of forking in the road.
Andreas:
[19:11] Yes, yes.
Brent:
[19:11] So, because it's a heads or tails example, there's two possible outcomes, there's two possible roads.
Andreas:
[19:17] If you rolled the dice, there'd be six.
Brent:
[19:19] Six, yes. Okay. That makes more sense.
Quantum computers bring different worlds together for parallel computing
Andreas:
[19:23] And some point, it wasn't on your list of questions, but since we've gone this deep in the subject, quantum computers are a good topic to mention. Yeah.
Brent:
[19:32] Yeah.
Andreas:
[19:33] And I could do it now if you like. Yeah, I'd love to. So the essential idea of quantum computers is to take these different worlds and bring them back together.
Let them part for a while and then bring them back together and then use all those different worlds for basically parallel computing.
So if you have a computer, you think of it as one thing, but if you could let it branch out and be many and then pull it back together and use that as a tool for parallel computing, thatwould be incredibly powerful.
Keller:
[20:10] Yeah.
Brent:
[20:12] And that is possible because quantum computers are computing on atoms at roughly zero Kelvin?
Andreas:
[20:22] Good, exactly. So, then the question is what, But... Um...
Right. So if we made quantum computers out of objects in this room, you couldn't do it because of the things that hold the many worlds together.
If you made it out of single atoms, potentially, but then you need at least one atom can't compute very much.
So basically, the engineering side of quantum computing is, well, the physical, electrical engineering, if you want to call it that, side of quantum computing, is how do you assembleenough atoms to do something interesting without having all the phenomena that keep the world separate for good, for practical purposes, without letting all those phenomena take overand ruin the chance to bring world back together.
So it's a lot of engineering, a lot of quantum, a lot of, you know, looking for the middle ground between the atom, which is very quantum, but not that interesting, or like a supercomputerof our era was just too classical.
We use the word classical for things that where the quantum effects are hidden and things that are large enough for the quantum effects to be hidden.
Brent:
[21:43] And because you're operating still on atoms and they're, you can't touch them, you can't move them, you can't, they're at, are they at zero Kelvin, are they near zero?
Andreas:
[21:54] Well, sometimes they go to zero Kelvin, other times they go, I mean, there's different approaches to try to simplify.
So, you basically need to simplify the physics enough that there's not all these different phenomena that are ruining the quantum effects.
Brent:
[22:09] So that's when it becomes computing because you are able to implement that change and then watch that change occur.
Andreas:
[22:15] Well, then the other piece, yeah. But the other piece is then if you, suppose you achieve this branching and then bringing the branches together, what computations can you do withthat?
Yeah. And that, you know, one piece of that story is algorithms.
Like, what if I have these tools so I can do these things, what, you know, how do I write code for that?
How do I, how do I, you know, how do I actually benefit from that efficiency, that potential efficiency? And And there's a lot of work going on with that as well. End.
Brent:
[22:54] Would the coming together occur naturally?
Andreas:
[22:58] No, it would be hard. Like we, our worlds, we flip a coin, we'll never come back together on that one.
Overcoming Separation of Worlds: Engineering for Reunion
[23:08] And so, you have to engineer something so you do come back together.
And the way these different worlds tend to be separated, it turns out it's really overkill.
Like every single photon that strikes us is keeping the worlds apart.
So like if one photon hits my head and goes flying off into space, to bring the worlds back together, we'd have to go catch that photon and reflect it back and then collect all the photons.
Like who can do that? We can't do that.
And so what you do, you have to keep those photons out to begin with.
And you have to just really isolate the system. So it's only interacting with the different elements of the computer.
Brent:
[23:54] Yeah.
Keller:
[23:55] Are there particular models that they're trying or algorithms that they're trying to use to design these?
There's lots. Are they building them for the purpose of particular models that they want to run or just to build them for the sake of getting there?
Andreas:
[24:08] Sometimes. So there's all of that's going on. So the answer is yes to everything.
People are trying all kinds of things. People are...generally, the idea of a computer is it's...
Has a lot of, you can program lots of different things on it.
And some people are sort of thinking about it that way.
Other people are thinking about very task specific computers and that sort of every, like, you know, a thermostat, I just thought, I just looked at the wall, a thermostat is a computer.
And when I was a kid, thermostats were really basic things, you know, made out of heat sensitive metal and little, you could open it up and pretty much understand how it works.
Now they have little microchips in them. And their computers.
So, that's sort of an illustration of both approaches.
Early thermostats were purpose-built, you know, built to run a certain algorithm.
Modern thermostats have microchips that could be programmed to do anything.
And then, like, what decides how to build a thermostat is sort of the economics, you know, it's sort of an engineering question.
What have you got? What tools have you got available? You know, when people, when there's only one microchip in the world, you're not going to go build thermostats out of it. Now youcan, you know, pick them off the floor.
Totally different.
Brent:
[25:34] ________________ And for the listener who may be completely unfamiliar with quantum computing, is a crude simplification one saying, the world is full of quantum computers,is just called nature.
We all are operating with biological atoms, like molecules.
Our body is a massive quantum computer just operating in a different way. P.M.
Andreas:
[25:58] Yes, and I like saying that. The difference is that it's a quantum computer that's not exploiting the potential of the many worlds.
[26:11] And maybe a way, yeah, I like saying the whole universe is a quantum computer.
And the thing, I'm trying to think if I can do this in a simple enough way, but basically, if I want to describe the math of a single particle moving along a line, I need two numbers.
I need its position and momentum for classical physics.
For quantum physics, I need an infinite number of numbers to describe the probability of finding it anywhere along the line. And, that's a lot harder. So if you tell me, go calculate, gowrite a program to calculate, solve the equations for a single particle, if it's a classical particle, it's trivial. I just, in no time, I've got two numbers, I have an equation for them. That's veryeasy stuff.
Once you have an infinite number, you can't put an infinite number of numbers on the computer, so you have to start making approximations and all that.
But nature, when nature moves a particle along the line, it's doing the hard calculation. And it's doing it in real time.
So nature's doing all this hard work. For classical computers, engineers work really, really hard to keep the quantum effects out and to keep it simple.
So to make the ingredients of the computer pretend they're as simple as a single particle on a line.
But nature's doing the hard work anyway. So why not harness that.
Brent:
[27:40] Definitely.
Keller:
[27:42] And stepping out a bit from quantum computers, could you talk about your work
Exploring Quantum Cosmology: Understanding the Universe's Origins
[27:48] with quantum cosmology?
Andreas:
[27:49] Sure. So, maybe we should just start with plain old cosmology, which is, you know, how did the universe begin? How did the galaxies form?
What does all that look like?
Brent:
[28:02] Or maybe some basic facts or stuff like that. that. Yeah.
Andreas:
[28:06] We can talk about facts. I know you asked me about sizes and numbers and well, I did, you know, I have ways of talking about these numbers professionally that maybe are hard torelate to and I'm not sure.
So, okay, the universe is 14 billion years old, like what does that even mean?
Like to creatures that live, you know, maybe up to a hundred, what does 14 billion years mean?
I don't, you know, it's hard to even picture that. And then what that means is just like the period of time in the universe where we think we understand its history is 14 billion years.
But we have no reason to think there wasn't something there beforehand.
The Observable Universe and its Size
[28:55] For related reasons, the observable universe is about 14 billion light-years across.
But that's sort of just as far as light has had a chance to travel since the beginning as we know it.
And so, it's just like as far as we can see. It doesn't mean there isn't a lot more out there, but it's as far as we can see.
So, those are some numbers. There, are…, We use the math, the mass of the sun is like 10 to the 30 kilograms.
What does that mean? Like, how do you do 10 to the 30?
One thing I didn't bring with me, in public lectures I've said like, okay, if we want to do a distance, yeah, I think I'm remembering this one correctly.
So if you want to cross the size of the universe, go to a mountain range, pick up a grain of sand, walk a kilometer, pick the next grain, walk another kilometer, and when you've cleared thewhole mountain range, you've got to the other side of the universe.
So like, wow. It's really beyond normal comprehension.
[30:15] We use powers of 10. So, it's more available, but I will say that to this day every now and then, and I've been doing this my whole adult life, to this day I'll stop now and then andthink, wow, I'm really working on this.
Brent:
[30:32] PW. Yeah.
Keller:
[30:35] Is there a shape associated with the universe?
Andreas:
[30:39] I really like that question too, because it's really simple.
The shape as we know it is just simple, like it's the same in all directions and very, sort of as far as we can see, sort of unremarkable and the most unremarkable shape you can imagine.
A colleague of mine, so for a while, several decades ago, people were working on alternate shapes and I was thinking, Oh, that's just so...
[31:10] Too quirky for me until I thought about and realized the only reason I thought that is that I was sort of used to thinking like I could just fall into a groove and thinking the standardway. And it's actually, it actually was a really interesting question.
Like why, why would it be one shape rather than another? And the thing is general relativity, which is our best theory of gravity, Einstein's theory of gravity, will allow for all kindsshapes, all kinds of really weird shapes.
So, it's a really great question, what is the shape of the universe?
[31:43] And a friend of mine who worked quite a bit on that tells the story of how he… So, he was working on, at the time, the biggest, best data set on the universe, and he had helpedcreate it and he'd helped sort of analyze it and bring it to a workable form.
And he thought, okay, now it's time for me to do the shape of the universe test.
And he set it all up and he's pressed go, and he got this result, like the universe has a very complicated shape.
And he was living on cloud nine for about a day thinking he'd made this radical discovery, until he realized that he had run the test not on the real data, but on the sample data he'd createdto explore what would the data look like if the universe had a radical shape.
Brent:
[32:41] Paul That makes a lot of sense. Just kind of thinking about that idea, if we observe the universe from light coming in from light years away and we operate on what is basically thesphere, not like perfectly, but.
It would seem from our perspective, it would be spherical. Yes.
Andreas:
[33:02] Yes.
Brent:
[33:03] But that's because it's our perspective.
Andreas:
[33:05] Yes.
Brent:
[33:07] And because everything is coming to our centralized point.
Andreas:
[33:11] So, I have an analogy I like to give with that and I'm gonna let you guide me a little bit how much- Sure. Oh, you sure? Should I go into that?
Keller:
[33:18] Yeah.
Andreas:
[33:21] So, imagine we go out to the massive desert as far as the eye can see and we set down a grid of, I don't know, every kilometer, a grid, a point on the grid.
And then we take some really noisy thing. When I was a kid, we were fascinated by cherry bombs, which are big firecrackers.
You see, I'm like, you've heard of those. So they're sort of the biggest firecracker you get, and they weren't legal. You know, they were for scaring birds off of cherry trees.
Brent:
[33:46] Oh, okay.
Andreas:
[33:47] That's why they're called cherry bombs.
So, you put a cherry bomb on every point on the grid, as far as the eye can see.
And then you set it all up so they both, they all ignite at the same time.
So there's this big boom, but what do you hear?
Well, first you hear the ones nearby, then a little bit later, because the sound takes time to get to you. Then you hear the ones further out and so on.
And so at any given moment, there's sort of a circle around you, which are the ones you're hearing at that moment, the one ones where the sound has got to you just then.
And it's the same kind of, so that's in two dimensions of the plane, and then you take that to three dimensions, you get a sphere.
That's just what you were talking about a minute ago.
Keller:
[34:32] Paul And then with regards to the data, you said your friend was working on this data model. What is, if it is simple enough, what is some of the data points that they're collectingfor these models?
Andreas:
[34:43] Phil So they're looking, actually, it's a good thing we're talking about the sphere because they're basically…so the universe is known to be expanding, and as it expands, cools andbecomes less dense. And one of the dramatic events in that sort of history is the universe at early times was very dense and totally opaque.
And then at some point, it diluted enough to become transparent.
So there's this moment of transition to transparency.
And so when you look deep, you can look deep enough, you can see the edge of transparency.
[35:23] And it's like an edge. Like you can't see past it because the universe is opaque at that point.
And so, that's called the last scattering surface because the opaqueness is about photon scattering off of things and not just passing smoothly through.
So, it's the moment of last scattering where each photon has its last scatter off of something, which is colliding with whatever electrons or whatever collides from, and then it just passessmoothly to us.
And that's called the last scattering surface.
And those photons, when they last scattered, it was something that was roughly like the surface of the sun.
And lucky for us, as those photons travel through the expanding universe, they cool off.
And so, now it's just three degrees above absolute zero.
If, which it's a lot, imagine something that's like the surface of the sun all around us, we'd bake in that time, right?
So we're lucky about that cooling. And we've detected that. In fact, this ball I have up here is a map of that surface. So we see it from the inside, that's harder to make.
So they put the map on the outside. That's an actual map of the distant universe 14 billion years ago as the photons were leaving, having their last scattering.
Brent:
[36:48] PW. And for the listener, it looks like a globe with a red ring around what would be the equator kind of representing the… BD.
Andreas:
[36:56] And the red ring is actually the galaxy.
So, that's not looking deep. So, you might think studying the galaxy is this adventurous exploration of the deep, but for that project, the galaxy is just something that gets in the way oflooking way deep into the universe.
Brent:
[37:16] CB Very interesting.
And a lot of your work is focused around the origins of the universe, correct?
Andreas:
[37:24] BF Yes.
Brent:
[37:25] CB How would you describe the origin?
Andreas:
[37:28] What do we know about the origins of the universe? Well.
Brent:
[37:33] Real quick, what do we know? And then where is your position on the things that we might not know for certain?
Andreas:
[37:39] So we have Since decades ago, so well well before the beginning of my career which which started in the early 80s There's been the Big Bang Theory and That's about theexpanding universe.
It's about you know, that's some expanding universe is something that can be understood very well in terms of Einstein's theory of gravity, which is our best theory of gravity.
The Success of the Big Bang Model
[38:10] Against this picture of an expanding universe, we can load up all the known physics that's, you know, as we look back in time, the temperatures are higher, the physics is, you know,higher energy physics is relevant to those eras.
And you can piece that all together, and that's really become a marvelous success story, where even predicting this microwave background was at one time a radical thing.
There were people who didn't believe the universe was ever that hot to be opaque.
[38:46] In fact, the Big Bang model was a term produced as an insult by someone didn't think it could ever be that way. Oh, you're a big bang model, he said.
But now it's our basic understanding, the microwave background, we've seen it now, other things, the formation of nuclei in the universe, all kinds of things fit really nicely into the model.
There's a question about how that got started, what the origin of the galaxies is and all kinds of things.
There's something called cosmic inflation theory, and that's something I've been involved with since the very beginning, which is now widely embraced as the right way to describe howthe big bang got started.
[39:44] It's so productive. It's a theory that does a great job of – you can collect all this data, like there's amazing data sets.
They don't just put them on pictures on balls, they're really high-powered data sets that you can do all kinds of things with.
You can take those data sets, you can use them to fit – you can use inflation theory to fit what you see, and that's what physicists love to do, is have data and theory and fit them togetherand all that.
So, cosmic inflation theory has been really productive and rewarding to people who like to do that, which is all physicists.
But there's also some really interesting open questions with that, which I'm fascinated with. And it's much more tricky.
The relationship between the field, the community, and those questions is much more complicated.
I think a lot of people just want to hunker down and have curves to fit their data, and then other people are absolutely thrilled to be curious about this.
Brent:
[40:59] And then when you're talking about the data sets, could you give like maybe one or two examples of like what a data point would be?
Andreas:
[41:06] P.H. So, let's talk about the cosmic microwave background again.
CB So, you have, so, it's called the microwave background because these photons which started more or less in the visible.
Exploring the use of microwave antennas in telecommunications
[41:51] Range have cooled, and as they cool, they change their wavelength were experimenting to understand what kind of backgrounds from the space were going to interfere withtelecommunications.
So, you use a microwave antenna, and they don't have to be as big as that.
There's a whole technology for that.
You use a microwave antenna, you do everything you can to avoid interference from Earth. The best ones are launched into space and sit far from the Earth on satellites and then, youmeasure the voltage of that antenna. You look around the sky and you measure the voltage, and then you measure it at different frequencies, and you analyze that and interpret it as atemperature, which is the natural sort of way to interpret that because it's a temperature variation.
So, after digesting all these voltages as a function of… So, it's fundamentally voltage as a function of direction that you're pointing and then that gets shaped into a temperature as afunction of the spot on the sky.
And then eventually that gets shaped enough that theorists like I can know how to work with it.
Brent:
[43:10] And then how would cosmic inflation, what does it say? What is the theory?
Andreas:
[43:17] So, it says that the variation in that temperature has a very particular origin, and certain patterns in that variation are expected to be found.
And that's getting a little hard to describe in words, but there's an analogy.
So, one of the really fun parts of my career certainly has been developing that, but also developing an alternative theory and understanding how to best compare those two alternatives.
[43:56] And the analogy I give, so there's these patterns in the temperature maps, and I'm going to just talk about an analogy with that.
So if you've ever taken a pot of water and just banged the side with a spoon, maybe I'll, just to be clear, I was once an undergraduate.
I had jobs in the kitchen and I would do that. I didn't always, my manager didn't always appreciate the distractions I found.
But if I had the job doing pots, you know, there's some honking big pots they have in these college cafeterias and you can get some amazing standing waves.
I recommend you wander back and talk to your friends who are working in the kitchen and check it out because there's some pretty amazing standing waves.
[44:39] That's what inflation predicts basically, is this pattern of standing waves in the temperature fluctuations in these microwaves.
The alternative theories, which were cosmic strings and related theories, a whole different story, I could get into that if you want, but the upshot was that.
If you take that same pot that has those beautiful standing waves, and instead of banging it once, just keep shaking it, shaking it, and shaking it, you'll never see the standing waves.
You'll see lots of waves, but if you just keep shaking it, it won't settle into the standing waves.
And that was the alternative theory, is that there were basically these amazing radical strings whipping through the universe at nearly the speed of light, just stirring and stirring andstirring.
[45:32] And so, and these were things we worked out before the data was in.
So, we knew it was going to be one or the other. CB.
Brent:
[45:39] Okay. PB.
Andreas:
[45:40] And then over time, the data emerged and we learned that inflation, that these standing wave patterns were there and the cosmic string ideas were ruled out and inflation wasworking.
Keller:
[45:53] PW – And are physicists testing their theories on the same dataset? PW – Yes.
Cosmology: Datasets and Public Analysis
Andreas:
[46:04] So, with cosmology, we're at a stage where we really – there's these huge datasets, and there's people who devote their careers to being as good as possible at getting the bestpossible datasets.
And then that at some point, and sometimes they have, typically they have a head start of working out the implications of that dataset, but at some point it becomes totally public andeveryone can work with it and analyze it their way and, you know, visit different ideas with it and so on.
Brent:
[46:39] So, at a higher level, cosmic inflation is saying the universe is expanding or- No one argues with that. Okay.
Andreas:
[46:50] But it's a detailed, I haven't told you much about exactly what inflation does.
It yields these predictions about the standing waves.
But the whole, the picture is actually one of accelerated expansion.
[47:06] And now I'm trying to think if I can work my way, work another part of the story in, because it's actually, I'm going to try, okay?
Because I think it connects a few things.
So, one of the remarkable results from quantum theory when it's applied to elementary particles is that, um...
So, we tend to think of a vacuum as just an emptiness with nothing in it.
But from the point of view of the quantum field theories we use to describe fundamental physics, the vacuum is just another thing.
It's not, it's, I mean, technically we call it the absence of particles, but in terms of the fields that we use to describe those particles, it's just another state of those fields.
It's not all that different from a state with one particle or two particles.
They're all interrelated in a pretty simple way.
So, the nothing in between the things is just a known state of matter predicted by just how we understand the fundamental nature of matter.
Brent:
[48:27] Is that anti-matter?
Andreas:
[48:28] No, well, it's a different part of the story.
So, the idea of anti-matter emerged as another piece of quantum field theory that sort of is needed to pull everything together.
[48:46] But the vacuum is this well-known state of matter.
And what inflation does is it has this period of very rapid expansion, and it takes that vacuum state.
That sort of sits between the particles and expands it to all observable scales of the universe.
And so, what it does is it gives a very specific prediction.
If you want to know what it's like out there, you take the vacuum state, which is a known thing.
Instead of asking, gee, what is the state of the, what is the universe like at the beginning? It could be this, it could be that, it could be anything.
Inflation says, it's one thing.
It's the vacuum state stretched out to all scales.
And so it gives a very concrete answer to how things started, how things looked at the beginning.
And that's where these standing waves come from. That's where a bunch of things come from. It turns out there's still dials you can turn so you can get different results and that's where thedata helps constrain things.
But that's sort of this very fundamental starting point is saying, you start with this vacuum state, you stretch it to all scales, and then that's where the regular Big Bang takes over and doesall the other stuff.
Brent:
[50:02] So it's a theory that once we got the data, we could test it against multiple data points. Yes. And then be, okay, that does hold true.
Andreas:
[50:12] Yes, and that's held true. Okay. And then different people have different feelings about, so there's the remaining dials.
So some people say, well, if you have dials, you can turn.
How much of a prediction have you made?
And for me, the contrast with the cosmic string model was the big turning point where we really had two competing ideas and one of them failed in inflation.
Brent:
[50:40] Is the cosmic string model string theory?
Andreas:
[50:43] No. Although there was a while when string theorists were especially curious about that connection. It's not, um, it's for the most part quite different.
Brent:
[50:59] Paul Okay.
Keller:
[50:59] Jared And within the vacuums, do we, are we able to predict those accurately?
Andreas:
[51:05] This might be part of it because it's like- Paul So, the vacuum is something we think we, in this regard, we understand it very well.
Jared Okay. Paul And it's very quantum. So, you were asking about quantum cosmology.
That's part of how we end up thinking about the universe in a very quantum way, is that it's the quantum vacuum that starts it all.
And in fact, probably it's fair to say a big driver for me getting involved in all this quantum stuff that we were talking about earlier was how to make sense.
So if the universe is so fundamentally quantum, and if the origin of the galaxies is so fundamentally quantum, and the quantum saying, well, it's all probability, so the galaxy could behere, could be there, how does that turn into, I see a galaxy right there?
And so, wanting to feel I really understood how to picture that is what drove me initially to really looking at some of these quantum questions I was talking about earlier. Okay.
Brent:
[52:17] And then at a higher level, thinking about the quantum states at a very, very small level, just because like an electron might be in multiple places, if you take that scale and reallypan it out to a, at the earthly level or at the universal level, It can both be true that the quantum thing may be having some variations at a small scale, but when we start zooming out, thatvariation is so small, it's basically saying, it's right there.
Andreas:
[52:51] Well, good. So what happens?
So we talked about flipping a coin, and how we...
Could then create two worlds with different narratives, different things happening, and those worlds couldn't communicate with each other.
What happens in the case of the universe and the quantum vacuum going to large scales is once it gets to the large scales and once all the complicated stuff starts happening, like galaxiesforming and all these things, that same complexity that keeps our worlds apart that we were just talking about will keep those different possibilities apart.
So they'll all be there in my way of thinking, but they'll become inaccessible.
So whereas the electron in an atom needs to know about all the other possible places as it could be to experience its physics.
The galaxies don't know about the other possible places for the galaxies.
Brent:
[54:01] Paul Okay. So, they could both be true at the same time. Yeah, that makes more sense.
Keller:
[54:06] Paul And so, how does the idea of like a multiverse fit into all of this?
Does that exist within what we've been talking about, about the quantum states, or is that a distinct?
Exploring the Many Meanings of Multiverse
Andreas:
[54:21] So that's a good place to start. So people mean many different things by multiverse.
One of the places they start is the many worlds of quantum physics.
There's also ideas. So then where we haven't gone yet is, well, how did inflation start?
And it turns out that's a can of worms.
And that's a pretty challenging topic and there's sort of lots of ways you could go with that. And And one of the ways is that the universe actually exists in a state.
Where many starts to inflation can happen.
In one point of view, inflation is constantly happening out there, and it's more like, how do you end inflation?
How do you find a way out of inflation?
In a popular point of view, inflation is always happening, and then different regions are ending inflation at different times and it just keeps persisting.
So, infinitely many universes are created from this sort of infinite resource of eternal inflation that's called.
So, that's a picture of the multiverse.
Then that can get even more complicated, depending on which theory you're working with.
Brent:
[55:46] KP. Would observing the universe end that line of inflation?
Or like observing, if things are constantly breaking apart, going different directions.
When we take that data point, we observe that photon coming back and hitting us. Is that the end of that one line?
Andreas:
[56:07] CB So by the time the photon's hitting us, the brand…oh, I think I see what you're saying, Yeah, so is that no longer…it's definitely not going to…well, now we're getting to thepoint where there's different ideas about what the future holds and all of that. But yeah, observing a photon helps pin things down.
Just like when we flip a coin, we all agree what it was and that pins down what happens next.
Observing a photon is like that in the cosmos, absolutely.
Keller:
[56:40] Paul And then another broad question, if energy can either be created or destroyed, where did it come from?
Energy Conservation in General Relativity
Andreas:
[56:54] CB So one thing is that we know of energy being conserved and not created or destroyed, but in general relativity, that's not true.
You can create energy and destroy it.
So it's only approximately true in the world around us, because basically, the world around us, there's not much general relativity going on.
And so, we're sort of safe from some of those phenomena in terms of everyday experience.
But it can be created and destroyed. It doesn't mean there aren't – so, I sense that you're bringing that question up as sort of a mystery of the beginning.
Doesn't mean there are still mysteries about the beginning, but we don't have to worry about the bookkeeping for energy.
Keller:
[57:48] Yeah, okay. And then could you explain briefly the theory of relativity and Einstein's theory of gravity because we mentioned that a few times?
Tempted to Explore Different Perspectives
Andreas:
[58:03] So, yes, I'm tempted, I'm trying to focus this because there's lots of ways I could go with it. Einstein.
Gravity as Curvature of Space-Time
[58:18] Proposed and seems to be true, that the phenomenon of gravity as we know it can be described through the curvature of space-time.
So, you take space, the three dimensions of space, add a fourth dimension of time, describe that in using mathematics that can describe curvature of those in that space.
And there's a way to systematically interpret gravity as curvature.
And so, you might have encountered Newton's laws, where you say that without forces, particles move with constant speed.
So in general relativity, gravity is not a force.
Particles experiencing gravity travel freely, but they travel freely through curved spacetime.
And it's that curvature that changes their path in a way that we think is the gravity.
We routinely think of that as the gravitational force, but Einstein said, well, let's change that and let's think about that as free motion in the curved spacetime.
Brent:
[59:36] Time. So, that could an analogy be if you were sending a ball spinning around a bowl and it's a frictionless bowl and that ball's going around, that's operating in a differentdimension, but that idea that the ball is moving on that path because of the shape of the bowl.
Andreas:
[59:53] Yeah, I like that, yeah. So, that's, yeah, it's a very rough analogy, but yeah, it's, it's, the ball is just doing its thing.
Normally we would say, it's very rough because normally we would say, well, there's force of the ball of the bull on the ball.
But if you weren't so analytical about it, just say, oh, that's naturally moving in a circle because it's a bull, that's sort of a reasonable analogy, yeah.
Brent:
[1:00:24] And then with that, what makes up space if we're talking about it kind of being a surface that the things are traveling through?
Andreas:
[1:00:35] So, in Einstein's theory, that's a fundamental thing. It's called the metric and the metric is what tells us the shape of space and it gives all the information about how curved it is ornot.
And the metric is, so just like in Newton's equations, the position and momentum of a particle is the sort of fundamental thing you work with.
In Einstein's gravity, the metric is the fundamental thing you work with and the metric itself can change as a function of time and it's a dynamical part of nature.
Keller:
[1:01:13] PW Is the metric the way that people should generally think about space-time, or the space-time continuum?
Andreas:
[1:01:22] BF Well, if they're digging that deep, yes.
You know, if you're trying to get to the corner store, maybe it's just better to think of the city map.
But yeah, so, right.
So, one of the things the metric, Einstein's theory helps us work with is if it's normal to ask if the universe is expanding, what is it expanding into?
And the right way to to look at that from Einstein's theory point of view is that space is actually being created between things.
So it's not expanding into anything, it's just spaces being created between things.
Metric: Shape of Space and Curvature of Spacetime
Keller:
[1:02:14] Yeah.
Andreas:
[1:02:14] And things are getting further apart because of that. So that's one example.
Now, there's also ideas that maybe the metric's not the fundamental thing and then there's the layers down to go and that's where string theory comes in and lots of other ways of thinking.
Brent:
[1:02:31] Yeah. Yeah. And is there a way to, probably not, but is there a way to like prove or test these theories in a way that, so like when Einstein first came up with this, did he see aproblem that original ideologies of gravity had, comes up with this new idea and said, hmm, I see multiple different things here that verify this idea?
Andreas:
[1:02:55] Yeah, that was very concrete. So he predicted certain phenomena in the solar system, which were then measured.
And so the very concrete tests were made. And by now, many, many concrete tests have been made, and Einstein's theory has been very, very successful.
It's normal in physics these days to expect your fundamental theories of one decade to become the derived theories from something more fundamental in some future decade.
[1:03:34] Remarkably, and that's happened in particle physics a lot. So we still think of electrons as fundamental, protons and neutrons, not at all.
They're made out of quarks and gluons and that story sort of seems to continue.
But remarkably, Einstein gravity is not tolerated. So people have proposed lots of variations on that theme, and none of them, all of them have been proven wrong.
It's been very hard to be successful with that.
And I remember at a conference when someone who made his whole career of trying to look beyond Einstein's theory, and it was very, very, sort of a, someone who was very invested inthat, I know could take very strong positions about it.
At some point, he got up and he just said, boy, Einstein's gravity is a tough theory to beat.
I've been trying to do it my whole career and nothing's worked.
And that's partly because people have lots of good data to test these alternative ideas.
Keller:
[1:04:42] Paul And more like on a broad scientific as labeling, is there any way in which that theory would become a law?
Andreas:
[1:04:48] CB Well, that's a great question. I would say…, um, I would turn it around and say any law might be superseded.
And there is no such thing as a law that couldn't be superseded.
What tends to happen is, what we expect is that when a theory is very well-established in a certain domain, we expect its successor to reproduce the result.
So there should be a way of understanding. So, with Einstein's gravity, there's a way to see how Newton's gravity works in certain limits.
And that's generally, and with quantum physics, there's a way to see how classical physics works in certain limits. So, and that's all there is to laws, our best theories of the time. Yeah.
Keller:
[1:05:48] And then you mentioned that Einstein's theory was built off of four dimensions. Yes.
Exploring Dimensions: From Four to Nine?
[1:05:53] Can we be certain that there are just four? Because in our preparation, we were watching some videos on string theory and different things that are extrapolating out and some ofthem were like, oh, this model is built on- Nine dimensions.
Nine dimensions, yeah. Assuming a given amount of dimensions and then tailoring that in. Could you just talk about what that means?
Andreas:
[1:06:12] Yeah. So, generally, people who work at the cutting edge of physics are always asking what's next?
What could be adapted? And the idea of additional dimensions is more or less as old as Einstein's theory.
People worked on adding dimensions a hundred years ago.
[1:06:35] The idea is that here's this beautiful theory, you can add dimensions and add extra ingredients to make the dimensions.
There's a way in which some of those ingredients look like they might show up as other things like the electric and magnetic fields or something.
There's different ideas over history about how that could work.
[1:07:01] But then you have to also hide, then the fact is we don't see other dimensions, so you have to hide that.
So, it's been a pretty fun ride trying to investigate that.
And yeah, right now people, for the most part, you know, string theorists are very, very focused on lots of different numbers of dimensions and then you need, you know, you can see whatthat does for you that there's very clear benefits and in sort of theoretic from the theoretical considerations, but also you have to find ways to hide those dimensions from us.
Yeah. And there's a couple of different things you can try with that.
It's not, it's now normal to think that there's interesting physics that's hidden from us. Quantum physics, you know, however long humanity's existed, we've only had to understandquantum physics in the last hundred years.
So, we're used to things being hidden from us. People didn't know if there was much of a universe outside the earth or outside of the solar system or whatever.
And now we know it goes for billions of light years. So, we're now used to having all kinds of cool stuff hidden away.
So, then the question is what's the next hiding place?
Brent:
[1:08:15] Yeah. And for the listener, a great visual representation of that video that we were referencing there was, if people are relatively familiar with a three-dimensional graph where youhave like the X, Y, Z axis, one of the hypotheses was a particle spinning around an axis is a different dimension, but it's still going from our perspective along that y-axis or along that x-axis.
So, from our perspective, it wasn't...
You don't observe a different dimension, doesn't mean there isn't one there of like the rotational one around that axis.
Andreas:
[1:08:51] Pete One way people run with that is say, imagine an ant crawling along a thin straw and the ant doesn't, you know, in some sense can't really explore the radial dimension, but cango, sees it as a linear thing.
And another, that's one approach it's called compactifying dimensions.
Another approach is to sort of have the laws of physics so they just stick to lower numbers of dimensions and it's just harder, it's hard to get off your part of the manifold you live in.
Defining Matter and Antimatter in Quantum Physics
Keller:
[1:09:29] Yeah. And then stepping back a little bit, could you define matter and antimatter in the space of… Phil Yes, yes, because you had asked about that earlier.
Andreas:
[1:09:49] Yeah.
So, you might've encountered special relativity as a conversation, starting with a a conversation about different reference frames and how things can look one way from one frame andanother way from a moving frame.
And basically Einstein's theory of special relativity tied all that together in a really cool way.
It turns out that when you take special relativity, So special relativity is special because it doesn't yet include gravity.
It's just So it's just understanding changes of reference frames before you get to curvature. So, when you.
[1:10:38] Take the special relativity point of view of changing reference frames, and you apply that to the quantum physics of elementary particles, you discover you need the idea of anantiparticle to comprehensively understand how things hang.
So a particle might look like an ordinary particle in one reference frame, and like an antiparticle in another reference frame.
And there's a whole elaborate scheme for keeping track of all of that.
So, because of special relativity and quantum field theory, particles need antiparticles, too.
So, in some cases, the antiparticles are the same as the particles, and in other cases, they have, like, the photon is its own antiparticle.
The electron has an anti-electron with opposite charge.
So there's sort of a whole scheme of keeping track of these antiparticles.
But it's part of how particles work thanks to the effects of special relativity.
And the different perspectives. So you can't really have a particle with how, if you didn't have an antiparticle of some sort, special relativity would break down.
Brent:
[1:11:58] And we have shown special relativity to like- And we found all these anti-particles.
Andreas:
[1:12:05] So, anti-particles are known things and accelerators are not just theorized at this point.
Okay. So, there's ways of measuring- Yeah, you can find them, you can create them. Wow.
Brent:
[1:12:14] Okay. So, are they currently all around us?
Andreas:
[1:12:17] Adam- So, in some sense, the actual matter of the universe is…so, you could…, ask, could there be equal numbers of particles and antiparticles?
And that's not the case. The real universe is made almost entirely of matter, not antimatter.
But there's antiparticles floating around, and there's also subtle ways they show up as quantum effects on smaller scales.
And that's actually one of the puzzles of the universe, is exactly how that imbalance was created.
There's ideas of how that, it's not a radical puzzle in the sense there's lots of good ideas about how that could happen, but it's not clear which, if either of the known ideas is what theuniverse chose. So.
Brent:
[1:13:08] Pong And does that same mindset extend to energy versus dark energy of the idea that if energy is acting in this way, in order for that to be true we have to have dark energy? PW.
Andreas:
[1:13:21] Yes. So, whereas there was a question earlier about energy and about conservation of energy and I knew just what to say because we know we understand energy very well.
So, I saw this question you had sent me your list of questions.
So, I was getting ready to say, um, we understand energy very well.
We don't understand dark energy at all.
And it's sort of dark energy is a label for energy for, for stuff.
We don't know stuff we see in the universe that we don't really understand.
And so it's got a label, but we don't really know what it is. Oh, okay.
But there's a, there's a glitch in that simple commentary I tried, which is the, um, I talked about the vacuum.
The vacuum has energy and we don't understand that at all.
What is the normal energy of the vacuum of elementary particles?
[1:14:20] We're pretty confused about exactly what to make of that and it's very closely tied to the dark energy.
It can have a similar effect.
Basically, we think there's dark energy because the expansion the universe that we know is there has now been determined to be accelerating, speeding up.
And if you think about, so the standard way we were thinking until 20 years ago when this, more now, 25 years ago when this was discovered was, well, the universe is expanding, but it'smade out of matter that we know, and gravity pulls things together.
So gravity should be slowing down the expanding universe, but instead it's speeding up. So it's like I throw a ball in the air, and instead of it coming down, it goes zooming off into theuniverse, You know, faster and faster.
I can't throw a ball out of orbit of the Earth.
Suppose the ball on its own, just took off. And that's what the universe is doing. So something's different.
[1:15:28] Something's, some anti-gravity kind of thing is going on. And we don't really, we don't know what it is.
There's lots of things it could be. It turns out it's not that hard to modify the known equations for the universe to get that phenomenon.
But, so it's not hard to come up with ideas, but it's each one has certain mysteries.
It's not like an easy, okay, this is it.
We know it's got to be this. Even just from a theorist's point of view, each one seems very mysterious and problematic in its own way.
And then we don't really know which one's right at this point.
Keller:
[1:16:07] Paul Yeah. And within the vacuum, how do we know that it is energy if we don't know how to define it exactly?
Andreas:
[1:16:14] So you mean if it's not conserved and that kind of—oh, so the vacuum—so if we take—so if I have an electron, I know exactly what to say about its energy.
If I have two electrons, I know what to say about its energy. 5, it's energy compared with the state of no electrons. So, if I take the state of no electrons, the vacuum, that's got some energyI don't understand.
It's technically infinite.
If I just take the simplest ideas seriously, it's infinite. We know it can't be that, so we typically just subtract infinity from it to say it's zero.
And then we know if we add one electron, we know what that is compared with zero, compared with the zero point, and so on. So, we know the relative energies.
And the thing is that until we go to general relativity, it's only the relative energies that mean anything.
[1:17:16] So, I can say this pen has a certain potential energy rising above the desk, and I can drop it, and that energy is released into kinetic energy.
But I don't need to know like where the zero point, I can do all of that analysis without knowing where the zero point is. And I can say, actually, way up here is the zero point of energy.That's fine. I can still do the same equations and work it all out.
But for Einstein gravity, then that zero point means something.
And it shows up in Einstein's equations in a particular place, and it changes how things operate.
And so, basically, one of the ways you can accelerate the universe is have the zero point have just the right value.
But we don't know why it should have one value or another.
So, that's where we admit, if we're being honest, we admit confusion.
The Arrow of Time and Entropy
Keller:
[1:18:13] Paul Yeah. And one quick question, I know we've been going on to some other points we want to get too before we wrap up, but could you explain the arrow of time briefly andwhy time travels in what seems to be one direction? So, um...
Andreas:
[1:18:30] So, your starting point is you seem to have noticed that it does.
So, you break a glass or whatever and it doesn't just hop back up.
So, the laws of physics as we know them say, if I were to take a movie of the glass falling down and include all the microscopic particles, a movie of the reverse is just as legitimate fromthe point of view of the equations we know.
Know. But somehow, it's hard to turn it around. Just like we talked about that photon going off into space. How do we get it and turn it around?
And it turns out that all of that boils down to how the universe began.
So, one of the usual ways we use to track the era of time is entropy, which is sort of loosely known as disorder or all kinds of things.
So, the beginning of the universe was in a very low entropy state, and it's been going up ever since.
And basically, it's very hard to take high entropy and turn it into low entropy.
Keller:
[1:19:40] Okay.
Andreas:
[1:19:41] And that's, but then comes the question, well, if it's hard to turn something into low entropy, how did the beginning of the universe manage to do it?
And that whole nice story turns into a big mystery.
And that's a whole thing. You know, I could go on and on about that.
But you can see how that ties in to cosmology, ultimately. Definitely.
Brent:
[1:20:06] And then we were also talking earlier about how laws are kind of just very well-tested theories in a way.
How confident are we that the constants that we observe in the world, the speed of light, the speed of sound, are actually constants?
Or does it matter if they truly are that the speed of light is this one speed.
Can we say that with certainty?
Andreas:
[1:20:35] No. We always question that. So the speed of sound is actually very well known to vary.
So what sound is, is the speed of certain kinds of waves traveling through air.
But we can also, I'm not sure you want me to actually pound the table with all these microphones here, but I can pound the table and that will create waves in the table.
Or I can pound on the wall or make sound waves in water travel at a different speed.
And so all of that, and there must be examples where, well, a sonic boom.
So, well, that's not quite the same thing, but a sonic boom is when an airplane is traveling faster than the speed of sound, and that can be… Anyway, so the speed of sound variesdepending on the medium.
[1:21:26] Remarkably, we have no evidence that that same thing is happening.
Well, No, the speed of light also, there's a sense in which the speed of light varies in the medium and that's what makes diffraction happen and all of that.
So, there's still, there's still, even when you say there's sort of the effective speed of light in a medium, but the speed of light, there's sort of a fundamental quantity in the equations thateven describe a diffracting lens that's the true speed of light in a vacuum.
And that doesn't seem to be varying, but people try it.
So, as I said earlier, there's the lesson physicists have learned is that there's always something new to, there's a new, deeper way to think of things that sort of expands our horizons andallowing for the possibility that the so-called constants of nature actually vary is one of the ways people explore.
Pondering on Interrelated Mysteries in Physics
Keller:
[1:22:22] CB We've been talking about a lot of different mysteries that exist within physics.
Is there a particular part of that puzzle that to you is the most fun or enjoyable aspect to ponder on?
Andreas:
[1:22:38] Well, what's coming up to me is sort of all the things we've talked about, and partly because I think they're interrelated.
So, we've been talking about the beginning of the universe, we've just sort of arrived at the connection to the arrow of time.
The beginning of the universe is connected with quantum physics, connected with the emergence of classical behavior from quantum.
I have a recent paper where I've been really digging into, well, how does this whole arrow of time thing look from a quantum point of view?
How does the beginning, you know, if you have a true quantum description, is there really meaning to the beginning?
And in what sense is there meaning to the beginning? And in what sense can you extract an arrow of time from that.
[1:23:34] We've talked about quantum worlds and we've talked about, many possibilities in quantum physics. So in some sense, it seems like an arrow of time is always a possibility in aquantum world, even if the full picture doesn't seem to have an arrow.
So that's been a lot of fun. So I think probably all of the mysteries that we talk about, at least at some point to me seem interrelated.
And so, I love sort of surfing among them and finding ways to connect them and who knows what, where that will lead.
Embracing Failure as a Learning Experience
Keller:
[1:24:16] In transitioning out, we have a few questions more so, I guess that are more tangible, starting with what's been the biggest failure in your career?
Andreas:
[1:24:26] Oh, I saw that question, and I thought...
You know, I think at this point, so I'm 65 years old, I've been through a lot, and I think everything that you could call a failure has also been something I learned something from, andalmost like enriched by the learning.
So, and maybe if I, you know, maybe that's a message to your listeners is the more a so-called failure is also a learning experience, the better.
Because I think picking up and going on, I think respecting the pain of something that feels like a failure, but then also finding a way forward is not a bad way to try to do it.
I'm not saying it was always easy.
Reflecting on Failure and Learning from Mistakes
[1:25:26] Long ago, I had a position. My first, it was at a national lab, but sort of like a faculty position. And I didn't get tenure.
And I was pretty annoyed about that. But I also took that as a chance to think, well, what went wrong?
And I don't think I was promoting my ideas well enough. I don't think I was, people really understood what I was getting up to in my research.
And so, I tried to get better of that, and that helped.
But on the other hand, the stuff I was doing then that people didn't really understand, I'm actually really known for now, and I've received honors recognizing that.
And a lot of my grant support now is based on the stuff I was wrestling with then. So it wasn't, you know, there were sort of many sides to that.
And I think, let's see, I had another thought about that, that you, Oh, I've lost it now, so maybe it'll come back. Maybe I'll think, but there's a lot of different kinds of failure.
And try to learn from it.
Brent:
[1:26:44] Certainly. And then what is QMAP and your role as director?
Andreas:
[1:26:52] So QMAP, so some years ago, then Provost Ralph Hexter had this idea that the campus was growing a lot and he thought, well, why not take a fraction of the positions we wereadding, faculty positions we were adding, and do something really new and different with those.
And there was a competition, a campus-wide competition for different ideas, and people in the physics department and the math department put together an idea of bridging those twodepartments, which is something that, now, I think a lot of people think, well, how can there be physics without math?
To really show you what more bridging can be done.
But the cultures of the different fields are quite different.
And so, the math we typically, the math the typical physicists use is just boring old hat for mathematicians.
[1:27:46] It's not research-grade math. There are known areas, like in string theory, where there are interesting links.
And so the idea was to create a community, hire some people to bridge those kinds of areas.
And that was successful, and we brought in some really exciting people.
And they said, let's think bigger than just this little group of four people that came in.
Let's build something bigger. And so that's what became QMAP.
And I was invited to be director, so I was not one of the new group that came in.
I've been here for a while, but I was invited to be director.
And I would say, um, you know, in terms of, I think we're all still learning what we, what we really want to do with it.
The Vision and Growth of QMAP
[1:28:33] I, I know, I mean, what we want is the, to have the most vibrant, exciting place possible to, to, to work in all these exciting subject areas.
And I think we, we already have that in the sense of all these individuals doing great research and it's fun to to be in the same space with them and it's fun for our students to have chancesto run into each other and for us to run into each other.
[1:28:56] Rather than cycling between different buildings and all of that.
And we've had, you know, great workshops bringing people in from around the world to, you know, to work on the latest things, and we have a lively visitor program, people comingthrough.
I personally, I think we're still learning how, what all we can do with that, it feels like just the beginning to me.
You know, this building came into, we were in separate buildings until the space was created.
And this space opened up, technically opened up in summer 2020.
But no one was coming into work in summer 2020. And it's actually been this slow process.
And I'm even noticing just like this quarter, or maybe last quarter, finally feeling like this space is really starting to feel like there's people here and there's people milling around andcoming and going.
So, I think we're just at the beginning and I think there's a lot of cool things coming from that, but it's already been a lot of fun.
Brent:
[1:30:02] Yeah.
Keller:
[1:30:02] Yeah. And could you briefly describe the logo? Yes. Because it's on the website.
It's a beautiful logo. We'll link it in the website, but- Yes.
Andreas:
[1:30:10] It's not part of the- So, if you go actually to the QMAP website and there's a section called science, if you click on that, it actually deconstructs the logo into the different.
So it's a series of overlapping images. One of them expresses gravity and through the image of a black hole, one of them expresses something called holography, which is sort of an ideathat's emerged from string theory and about the relation, actually relating different dimensions.
We were talking about different dimensions and very interesting relationships where what's going on in one dimension might be showing up in another, and ideas, of…, uh, interestingnew ways of thinking about the quantum physics of particles called amplitude, the amplitude hedron.
And there's sort of a variety of different, so images taken from a variety of the sorts of physics we work on, and then superimposed in a beautiful way.
So professor Hubeny as, um, as the designer of that, and it's really great.
And I don't, um, I don't see it, we have various bits of swag I don't have with me right now.
I should have worn my QMAP t-shirt to the interview.
Brent:
[1:31:28] And then real quickly, what does QMAP stand for?
Andreas:
[1:31:31] The Center for Quantum Mathematics and Physics.
Brent:
[1:31:34] Okay, perfect.
Andreas:
[1:31:35] So, I don't know whether the A is from mathematics or from and.
Brent:
[1:31:42] And we also noticed on the website, you say you typically do trial periods with graduate students.
Andreas:
[1:31:48] Right. So that's my own personal style, which is very common physics. Yes.
Brent:
[1:31:53] What are you looking for during that period?
Andreas:
[1:31:57] So that's a really great question. And it's something I, I, um, I would say a graduate student passes their trial period.
They don't all do it by doing the same thing, but where I see enough elements of promise, I would say.
And it could be sort of showing independent initiative, it could be showing technical skill, you know, usually some mix of all those things, showing curiosity, showing commitment,showing willingness to really dig in and work hard.
You know, there's probably a personal element like just do we click as a mentor and student.
Brent:
[1:32:44] Thank you.
Keller:
[1:32:46] What do you hope the listener takes away from the conversation today? P.H.
Andreas:
[1:32:51] Oh, I hope the listener gets a flavor for what an exciting adventure this is.
And I think there's something about our human nature that loves adventure.
And there's many places to have adventures. It doesn't have to be physics or cosmology, but this is one of them. So I hope I've tickled your sense of adventure and in whatever form youenjoyed it.
Brent:
[1:33:16] Yeah. Yeah. I think you did because I feel like as many questions that were answered were also brought up new questions and left unanswered.
So there's definitely a lot more adventure to be had.
Andreas:
[1:33:28] Absolutely.
Brent:
[1:33:28] And as we part here, do you have any other words of wisdom, advice, things you want to share?
Andreas:
[1:33:35] BF Yeah, I think what I'd like to think is that the sense of adventure we experience at these kind of frontiers can inspire people to feel a sense of adventure in whatever they do.
And I think one of the lessons from science is to stay curious and to, you know, like today's fundamental constant, maybe have some totally different explanation in the future.
I think it helps to think about life that way. You know, the way you look at life now, you may be curious and discover new ways of looking at it.
Maybe this is too ambitious, but if I think about the polarized politics we live in and all of that, maybe each of us having curiosity about the other side and trying to learn, trying tounderstand where people are coming from, And maybe that same kind of, maybe that curiosity can extend in helpful ways in lots of parts of life.
Brent:
[1:34:35] Pong Certainly. I don't think that's too ambitious.
Keller:
[1:34:37] Professor Elbrecht I hope not. Thank you. Pong Well, thank you very much, Professor Elbrecht. It's been wonderful. Professor Elbrecht Thank you.
Brent:
[1:34:41] Yeah, I've really enjoyed our conversation.
Andreas:
[1:34:43] Thanks a lot.
Brent:
[1:34:44] Thank you.