Is the universe igniting extra dimensions we can't see? Could a graviton, a particle we don't even know exists, change everything about the cosmos?

The only particles that can move through the extra dimensions of space are the gravitons.

And what does the future of physics hold if the standard model should happen to fail?

It would actually surprise me if the standard model of cosmology holds up to scrutiny over the next decades as we learn more and more about this piece of time.

I had the pleasure of exploring all these advanced concepts and more with the renowned cosmologist and physicist Dan Hooper in his former office at the University of Chicago. Now he's moved to the University of Wisconsin Madison, go Bang, where I spent some time at the end of my graduate student career. In this thought provoking conversation, Dan and I challenge and explore how hidden dimensions and mysterious particles can fundamentally challenge our understanding of the universe. So let's dive deep into the fabric of the cosmos.

Welcome to a very special episode of the Into the Impossible podcast with a colleague and friend and a past guest on the podcast, doctor Dan Hooper of the University of Chicago and Fermilab for now. Can we say what else is happening?

It'll be announced next week.

So something else is happening. By the time this comes out, it'll be out there. We're actually in person even though it looks like we're recording on Riverside. Say hi to Dan. There he is. So this is dueling laptops across the beautiful dot eduroam network. So we have a new tradition since you've been on for your last book,

At the Edge of Time. What was it?

At the Edge of Time. Yeah. Yeah.

Phenomenal book. Everybody should pick that up. 1 of your how many books have you written now?

3 plus the textbook.

Awesome. And then the textbook is right here, and I was gonna buy a copy, but you saved me $75. This is an incredible, addition to the oeuvre of graduate student level cosmology bang actually covers and updates a classic that we've talked about before, which is, Colvin Turner. And I'm interviewing your colleague, Rocky Colb, tomorrow on the podcast along with Wendy Freedman while I'm here. You guys are blessed. So what we do on the podcast is we love to do what you're not supposed to do, which is to judge a book by its cover. So Dan, take us through this wonderful book's title. And, there's no subtitle, but what does this cover? Are these epicycles? What's going on?

You know, I don't know if it's, like, literally Keating. But so Fermilab for many decades had an artist in residence, Angela Gonzales. She did many of the posters and much of the artwork around the lab. But she retired and then passed away years ago. But this is actually a piece that she did before working at Fermilab. And to me, it just struck me as evocative of cosmology, even if I can't point to the objects in the painting and say, like, these are such and such. You know? Yeah. It's more Yeah.

More abstract.

I've been looking through a couple of your recent, research. I should also mention you're the host of the, of the Why This Universe. Mhmm.

Along with Shama Wegman. Yeah.

Shama Wegman. She's in Columbia?

Well, she's in New York, but, she she's, working in tech these days.

Oh, she is? Okay. Great. I'll put a link to the podcast down below. You should all subscribe. It's one of my favorites. But today, I wanna talk about a research paper that we read about as a way to kind of do, do the impossible, which is to kind of break down some of the most advanced concepts, which actually have some of their origins a 100 plus years ago. And that's a Kaluza Klein theory in this new paper that you have about extra dimensions and gravitons in the early universe and how they could potentially decay. And I wanna ask you, first of all, Kaluza Klein, can you explain that in, you know, relatively straightforward terms? What is it what were Kalusa and Klein trying to do, and what has their legacy been?

So it goes back into the 19 twenties. These mathematical physicists, Theory Kalusa and Oscar Klein, independently made contributions to this idea that you could maybe fit the equations of electricity magnetism, what we call Maxwell's equations, into the general relativity framework that Einstein had for gravity. But to do this, you needed a 5th dimension. So the 3 plus one normal dimensions of space and time along with a 5th dimension. Now if you casually look at our universe, it doesn't seem to have an extra dimension of space. So they tried to to make this all hold together consistently by saying, well, that that big dimension is curled up in a little circle. So imagine that we're taking our macroscopic universe and imagine that if you went far enough in that direction, you'd eventually come out the opposite side. Okay? So that's what we call compactifying a dimension.