StarTalk Radio - Dark Universe Decoded with Katherine Freese

Episode Date: March 17, 2026

What are the main candidates for dark matter? Neil deGrasse Tyson and comic co-host Chuck Nice sit down with theoretical physicist Katherine Freese to tackle fan questions about dark matter, dark energy, and the dark universe at large. NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here:  https://startalkmedia.com/show/dark-universe-decoded-with-katherine-freese/ Thanks to our Patrons Yasin Hasbay, Joe Hudson, Marcelo Morales, Jeffrey C, Quentin Kelly, Mark Hobden, Shawnie Brisbois, Nathan Williams, Christian Etel, Adam, Andrew Foss, Christopher Lauer, Mike Smith, Gloria Goungo, Dennis Poggenburg, Wild Cat93, Tilly, Alon Gutman, Philip Sun, Dave Mulder, Neil Cameron, CuriousHairlessApe, Not Pensive, Thanh Ho, Aaron, Amy, Brandon Rhodes, Jeffrey Otterman, Space Hendrix, Mango, Yoni, Christopher, Cody Motycka, James Astley, Ryan Dimery-Seek, Alec Scott, Joshua Dobelstein, JP, D.K. Mola, Matt Sumner, Jordan Smith, Case Torres, Tiffany Jones, Josh Middleton, Christopher Crain, Abdul Sudi, Quyen Nguyen, Rahul Varma Sikinam, Nathaniel Gonzalez, Jonathan Negron, Adam Bauman, Sean McAll, Taylor, Lora White, CrunchySciFry, Robby Satterfield, James Simpson, Samantha Kasper, Isahn Mejia, Cameron Smith, Ray Nobleza, Mike Gibbs, Paul Stumbo, Ruben Wilberg, Anish Dube, Manolis Sensi, Arnab Deka, Rich, 4d916, Oon Thian Seng, Temo Chavchanidze, Vikas Rawat, Korin, Gene Hannon, Edward Marwood, Catherine Fiala, Matt F, Elijah Flippin, Bharath Kumar, Tuyaa, Furry Combat Wombat, Lexi Chivers, Vincent Franchino, R Tillery, Matthew Pitts, GAME MASTER, Lawrey, Chris Fro, Adam, Diesel Haphazard, Anthony Calomeni, Mike G., Victor Acevedo, David Wall, Jaime Rivera, Reginald Hill, Devin Jansen, Tushar Vashisht, Lisa Mc Guire, and Ian for supporting us this week. Subscribe to SiriusXM Podcasts+ to listen to new episodes of StarTalk Radio ad-free and a whole week early.Start a free trial now on Apple Podcasts or by visiting siriusxm.com/podcastsplus. Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.

We are growing our stable of cosmologists. Yes. Got Katie Freeze coming in. That's right. It talks about dark matter, dark energy, big bang, rocking. Yep. The only cosmologist who sounds like a Batman villain, Katie Freeze. Coming up on StarTalk.

Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk. Neil DeGrasse Tyson, you're a personal astrophysicist. This is going to be a Cosmic Queries edition on Cosmology. There's no end of Cosmic Queries we can do on Cosmology. I suppose there is not.

This is Chuck Nice right here. That's right. Professional comedian, stand-up comedian. There is an end to me. So, cosmology. Yes. So we're broadening our stable of cosmologists to whom we can reach out. for our queries.

Right. And today we have a second timer. That's right. The one and only. Katie Freeze. Katie, welcome back. Yay! Welcome back to StarTalk.

Thank you. Thank you. Last time you were here, I think we talked about the search for dark matter. And what? We did. We did. Because that's cosmology writ large. And we just, we poked your brain about all manner of things.

And this is going to be a cosmic queries where we have told our. Patreon supporters that you're going to be on. And they're fans of yours. And they've written in, or they became fans of yours when they saw your expertise. That's right. And they wrote in, and the questions are here. Well, thanks a lot. I haven't seen these queries.

Well, neither of I. He's the only one who's seen him. Yes. Okay. And I'm the only one who can't answer them. That made me true. That is kind of funny. The only people can't answer them and haven't seen it.

And the one who can't answer it. They have it. So a couple of times people have asked questions that no one has been able to answer. Like with the quark one going into a black hole. We still don't know the deal. We still don't know that one. Everybody says that. Maybe it's Haiti knows.

We can find out. But let me get your bio here. Director of the Weinberg Institute for Theoretical Physics, UT Austin. That's Stevie Wonder, Stephen Weinberg. Right? So Steve Weinberg, my hero, one of the founders of the standard model of particle physics. Yes. He was the greatest physicist of our time, in the opinion of many, including me.

His office was three doors down from me. He recruited me to UT Austin. Maybe that's why I think he's the greatest living physics. That helps. Who gave you the good job, right? Yeah, yeah. No, seriously. It was only named in his death, obviously.

Yeah, he died about three years ago. Yeah, okay. And we started the institute in his honor. And now he's more a hero for me than he is for you. Why is that? Because he went to my high school. Oh. Bada bang!

Oh, Bronx Science. The Bronx High School of Science. Both he and Shelley Glashow went through, we're in the same class. They were classmates and both shared the Nobel Prize. Okay, so the moral of the story is, when are you getting your Nobel Prize? I didn't mean to set it up that way. That was not. So what else do I have here?

And you spent some time at Stockholm University. And that's ending coming up very shortly. 10 years. They gave me a really, the Swedish government gave me a $15 million grant over 10 years to do cosmoparticle theory. And that was so much fun. Wow. Oh, wow. Did you have students too and everything?

Oh, I did. With a budget to go back. I did, yeah. So I had students and I had postgraduate fellows and everybody running up and down the halls, having great ideas and having fun. It was awesome. Wow. Yeah. Okay. Because I think when we last interviewed you, you were like fully up and up and running with them. And what else? Oh, and I'd love this back now 10 years ago. The Cosmic Cocktail.

Ooh. Can you get a better title than that? Shake it. I don't think three parts dark matter. Ooh. That's about right. That's pretty cool, man. You know, the amazing thing about that book is that I still give public lectures about it, and people are still buying lots of them. In fact, Amazon ran out again. Whoa. And that was a book I wrote 10 years ago, so I guess it was a good one. Whoa. And you wrote a blurb for it.

You said, what did you say, I don't know, three parts, dark matter, seven parts memoir, or something like that. Oh, right, because it was folded into your life. It was. Yes, very important feature of that. Thanks for reminding me. Yeah. It just made it a much more interesting account. Yeah.

Right, right. Cool. Here's another plug for it. Thank you. Amazon right out of the game. So, we went to chat for a bit before we go to Q&A. Okay. Catch us up on a couple of things.

The James Webb has been a lot of talk about these early galaxies that it has discovered in a zone of the early universe where you're not supposed to... So wait, you're talking about the James Webb Space Telescope. Yeah. Yes. Yeah. Yeah. Not the administrator of NASA during the 1960s.

Yes. After whom the telescope was named. Yes. You know he was an accountant? James Webb? Yeah. I did. One of the rare non-scientists

after whom a telescope is named. An accountant? I think that was his main training. That's pretty wild. I got to say. I guess he was, what was he important for in NASA? He was. What's wrong?

Was the head of HR taken? While we went to the moon, he was head of NASA. So it was a give a little back to that. Look at that. Fact, because you need good administrators, not just good scientists, to make stuff happen. When you're in the bureaucracy.

I'm a good administrator when they start naming stuff after you. So what's this we hear about paleo detectors? What is that? Is that a thing? Yeah. What is that? Well, the paleo part means that they've been around for a billion years. And so let me back up.

We're trying to figure out what dark matter is made of. And we think it's some kind of particle we haven't identified yet. Yes. And most of the experiments now involve these giant tons and tons of. of liquid xenon. And so the idea is, okay, instead of having... That's what xenon has some probability of interacting with a dark matter particle.

Yeah, yeah, dark matter particles flying around in the galaxy. And by the way, there would be billions going through your body every second. Yeah, yeah, but it's okay. Only one a month hits you. I thought I felt tired for a reason. And so... Wait, you know, there's a lot of elements on the periodic table. Why do you know that xenon might work

when we otherwise know nothing about dark matter? The way these detectors work is the dark matter comes along, hits one of these xenon atoms, deflects off of it, and the xenon gets some energy deposited in it, and they're able to detect that. So you have to have a detector design that works, and with xenon, we know how to do it. Okay, so it could be any particle that that would happen to, but xenon has some other convenient properties? So the kind of interactions we're looking for is from the weak force, very, very weakly.

interacting particles. Hence the name. Hence the name, weekly interacting massive particles. And there's people need to build detectors that are, that they know. You need to know how to build the damn detector. I don't know how to answer this one, Neil.

No, so let's say differently. A neutrino detector, for example, that uses vats of liquid uses like some kind of chlorine molecule, but not xenon. So where are these xenon? detectors. They're deep underground. Okay.

One of them is underneath the Appanine Mountains outside of Rome. Okay. You know, the Appanine Mountains on the moon. What? Named after those.

I was going to say that you've actually said that. They're named after the mountains here. The reason why I know them and the reason why they are important is the phase of the moon that's best for telescopic views is half moon.

Okay. Because shadows are the longest. And the Apennine Mountains crosses the half-moon divider, the Terminator. And so Apennines just pop on a first sighting of the moon. Oh, cool.

So to me, the Appanai Mountains are on the moon, not in Italy. All right, okay. Well, if you could build something on the moon, that would be even better because the reason you have to go underground is to get away from cosmic rays. Okay.

Right. And there's a million cosmic rays for every one of these dark matter particles if you're on the surface of the earth, so we go deep underground because the cosmic rays don't make it down there. But the dark matter particle would. But the dark matter particles would.

Okay, based on what we think dark matter particles would be like. Well, because they're only weekly interacting. Okay. Normal particles would interact electromagnetically. If you and I collide, we're not getting very far. No, that's right.

We don't pass to each other. We don't pass to each other. Right. I'll tell you something about xenon. Makes a hell of a headlight. Just wanted to contribute something, I don't know.

I'll tell you, one here? Another something about xenon? The other thing about xenon, it's become very expensive because the xenon experiments have bought the entire world supply. Get out. No, I'm serious.

Wow, I wish... I'm serious. Now you tell us, you should have told us before these experiments started. We could have got it on the cornering of the xenon market. Oh my God, that's true.

Yeah. Which is why we want to propose an alternative. So instead of these, Instead of giant detectors, we're going to dig up little rocks from deep underground, and they've been collecting dark matter tracks for a billion years. So we're replacing volume with time. Wow. Isn't that cool, hence, paleo?

Okay, now that is, first of all, that's very smart. Thank you. Wait, wait, so how do you know which rock to get, or any rock? Oh, well, we had to talk to a lot of geologists. And, you know, this was the first of paper with a few theorists in 2018. and next thing you know So in 2018 that was only a proposal It was yeah, we wrote a bunch of theory papers

Not every day Does this stuff turn into reality I've done it twice now You know the underground detectors I wrote papers I got that going And now with paleo detectors That's actually becoming a major experimental effort Isn't that cool?

And it's a cool name for a detector too Yeah Yeah yeah yeah yeah so they tell you Which rocks would best respond to this Yes and the answer is olivine Oloving Ollivine I know olivine You do

Yes. Oh, okay. There's a class of meteorite called palisites. Where? Oh, my gosh. So where do you get a meteorite from? It's a smashed whatever it used to be. Right.

Right. Okay. So if it's a proto planet, it partially, as the geologists would say, differentiated, because at some point in its formation, the heavy stuff would fall to the middle, the lighter stuff would float to the top. Right. Okay. If, however, it cools before it fully segregates.

then the metallic innards can trap olivine crystals. Oh, wow. Within it as they were slowly bubbling their way up to the top. And so a slice of these meteorites rear lit, if it's thin enough, the thickness of an olivine crystal, you see the metallic meteorite and these green crystals glowing through. And we have a sample of one in our whole of the universe. Oh, very cool.

It's called a palisite. Oh, I got to see this. I'll take you down right after this. Very cool. Very cool. So, in other words, it's rare because the boundary layer between the dense middle of a protoplanet and the lighter things that float up is very thin. And so when you smash the whole thing, you have a lot of rocky stuff, less metallic stuff, and even less at the boundary layer.

Well, can we borrow your olivine to look for dark matter tracks, please? You gotta know somebody. Okay. You gotta know somebody who works here. Thought I did. Yeah, no, we can totally explore them. That could be the key sitting under our noses. It's been here for 25 years.

Well, then it's been collecting cosmic ray tracks. Oh, no, we didn't have it. Sad. Yeah. Do you guys have any, like, deep under the earth here? Like, is there a... But it still has to get through the building. Yeah, we want to know about the sub-basements in the building.

It still has to get through the building, though. The cosmic rays have to get through the building. Yeah, well. That'll block some of them, right? All right. So, congratulations on this. Thank you. Thank you. This is now a burgeoning next step in this.

So why a billion years and not 100 million or 50 million? Does it matter? Well, we have to go deep enough to get away from cosmic rays. And that's actually like five kilometers. Oh, that's deep. It's deep. And then the other idea is if we get rocks from different ages, we also can study neutrinos, because neutrinos will also leave tracks. The tracks will be different, okay, so you can tell the difference.

But then you can figure out how many supernova went off in the galaxy, if you look in the past, a different amount of time. Isn't that cool? Wow. And that is because the supernova, that's where the neutrinos come from. Copious immemites of supernova. Oh, I forgot to say that. Yeah.

Neutrinos give off a lot of supernova. No. No, no, no. Supernova give awful lot of neutrinos. And so you, supernova, which are dying, exploding stars. And you can look for the neutrinos from the supernovae. Right. Cool, man.

And neutrinos are, once again, you're a weekly interacting. Yeah, they are also weekly interacting particles. Yeah, yeah, yeah, yeah. Most unfortunate. Now, the other thing you can do with... Weekly intermating particles, yeah, okay. Well, we know who named him that. Who named him? I forgot.

Mike Turner. Is that right? Mike Turner. See, that would have made sense if you said, Ike Turner. Whoa! The word eponymous comes to mind. I'm Nicholas Costella, and I'm a proud supporter of StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

So I got one more question before we go to Q&A. Some of the results of the James Webb Space Telescope and other sources suggest that we cannot reconcile the age we have derived. for the universe by these different methods. One of them is from the CMB, cosmic microwave background, others is from galaxies at other times. And it has been suggested

that you can reconcile them if dark energy changes over time. The biggest evidence for dark energy changing over time comes from a different experiment, the DESE experiment. Okay. And what they're looking at... Lucy.

and Desi No Dark matter You got some explaining to do Oh that's good That's good But Desi

So other than Lucy and Desi What does Desi Desi stand for astrophysically? The dark energy spectroscopic instrument

Okay All right Clean and simple And what does that tell us? What they're looking at is based on some physics

from the early universe And there were waves Which froze out at the same time the cosmic microwave background was produced. That's 400,000 years after the Big Bang, which is like, I don't know, thousands of a percent of the age of the universe today.

And what those waves did was leave an imprint that throughout the rest of time, galaxies form in these spheres left over from those waves. And so as time goes on, you look at how big are those spheres, and that tells you about the expansion of the universe. Yes. And what they're saying is,

fears would grow with the universe. Yeah. Yes. Yeah. And so by studying that, you can figure out what the expansion is doing. Is it accelerating? What is it doing? And what they claim is that the dark energy, which everybody, the vanilla model is that it doesn't

change in time. But it definitely affects the overall expansion of the universe no matter what. It's causing the acceleration, so we think. And what they're claiming is that the acceleration is slowing down. Oh. So it's a decrease. in the dark energy contribution to the universe. So now can I put it in a plug for my own work?

Please. So my collaborator, Yun Wang and I, we looked at the same data, and we looked at it differently, with a simpler way of interpreting the data, and we do not find that evidence to be very strong, actually. So I don't think it's happening. Big picture, there's a big debate. Is it real?

Is the dark energy changing with time or not? Is it time varying or not? And different people have different opinions at this point. simpler way to look at it, where the effect goes away. Yep. And we were betting on the likelihood of one truth or another. I'm betting with a simpler explanation. Thank you.

Well, me too, obviously. I mean, that taps Occam's razor. Well, from the data, we're directly extracting the dark energy density, the amount of dark energy. Instead of going through a... A secondary thing, which is called the dark energy equation of state. So we're doing it more directly. So that's why I like what we're doing better.

So you know about Occam's Razor? You've heard of? Let me just think. Removing all other considerations, the simplest answer is the most likely? That's a modern interpretation. What he actually said was, Go ahead. Multiplicity ought not be posited without necessity.

Oh, wow. Wow. Damn. So Occam, named for William of Occam, he goes way back. Okay. Yeah, like 700 years. Wow. So he had some insights into nature that persist to this day.

William of Occam. Sure enough. He knows how to turn a phrase, that's for sure. So I'm betting on Katie on this one, definitely. Very cool. But let me exit this before we get to the questions with a related question. Okay. You said the vanilla version of dark energy is that it does not change over time.

Yeah. That's how it appears in Einstein's general relativity. Yeah. It is a constant. Yeah. It's cosmological constant. Right. If you want to start making that not constant,

then it's no longer Einstein's general theory of relativity. It's some modification to it. No, it doesn't. How does he accommodate? How can his formulation of general relativity accommodate a cosmological constant that's not constant? I just want to say about dark energy, it is a complete mystery to all of us.

We have no idea what's going on. To be honest, okay? We could call it gobbledygark. I've already named it. Dark matter, dark energy, or Fred and Wilma. Okay. Because it doesn't have any bias at all. They're just two words.

Well, I don't know, because we know dark matter exists. I'm not so sure about dark energy. I want Wilma to exist. But anyway. But so dark energy, there's two possibilities. One is, as you said, you have to modify Einstein's equations. And that feels wrong to me. you know, I actually had an idea for how to do that in 2002, but let's not go there.

I want to talk about the other way, which is we stick with Einstein's equations. Wait, in 2002 you had a way to modify Einstein's general theory of relativity. Well, more specifically, the evolution equation for the universe, the Friedman equation for the universe, we had been working in extra dimensions. If you have string theory. As one would do. As one would do, because as one does. As one does.

In string theory, you have to have 10 spatial dimensions instead of the X, Y, Z, the normal ones that we usually work with. And if you do that, it's possible that, well, our universe is a three-dimensional surface in there. And there could be another one. And the stuff in between, which we call the bulk, is pulling on our surface and causing the equations to change. Oh. Interesting.

So we posited. Okay, so the equations would be sound within the universe left to its own devices, but influence outside of it, you got to give it some slack. Yeah, you do. You got to add these other terms into the equations, which describe the evolution of our three-dimensional universe. She just called our universe a slice. I did, yeah.

I believe that. It's kind of an interesting slice. I like it. Yeah. It's a dimensional slice. Yeah. That's a dig if I ever heard one. I don't know.

Like, during my ayahuasca trip, I met some beings that told me that there were dimensions alongside of our dimension, like, more than we could ever know. Dimension, dimension, dimension, and that there were dimensions above and dimensions below. Anyway, I don't even know why I said this. But yeah. But you know what they're called in physics? They're called brains. B-R-A-N-E. Okay.

Which is short for membrane. Yeah. It's short for membrane. Yeah. Yeah, just like, yeah. Yeah. Like thin little dividers. So the question you're asking, do some other of these brains contain B-R-A-I-Ns?

Mm-hmm. And we don't know. Because we know ours does. Right. I mean. I think so. I was going to say, if you want to call it that. We use the term loosely in our dimension.

So on the, can I tell you what I called this theory? What? I called it Cardassian cosmology. And the reason is that Lisa Randall was going on about the warp factor, which I thought... It's another physicist up at Harvard. Oh, yeah, she's great. And so she was talking about the warp factor in her theory, and I thought it came from Star Trek, but actually it's just a relativity term that I had heard called something else.

And so I thought, well, I'm going to go to Star Trek, so I went for the Kardashians. So I called it Cardassian expansion because everything would be made of ordinary matter, ordinary radiation, ordinary stuff. no weird dark energy, but the equations would be different. And so like the Kardashians, they're weird looking, but they're made of the same.

But they're two, bypassed like we are, and their goal is accelerated expansion of their evil empire. That's right. They're quite draconian, and their whole purpose is to take over everything.

Yeah. Well, Kardashian. Yeah, they're the Kardashians. Yeah. All right, so you got questions for you. We got, let's get to it. Let's jump right in. These are directly for...

And you haven't seen these questions. No, that's not fair. Why? What do you know? Well, I don't know. That's the whole thing here. All right. Well, this first question is from Anthroposomic Dillon, who basically says, hey, yeah.

He says, how do dark stars work? What would they be like to visit? And how do they impact extra solar systems and potentially astrobiology? So he's just, he wants you to just answer everything. Answer it all, Captain. Let me prepend that. Go ahead. In, was it the 1800s or late 1700s,

there was a calculation done by a physicist who said to himself, the gravity on a star is whatever it is, but if the star shrinks, the surface gravity goes up. There'll be a point where the surface gravity prevents life from escaping, and the star will disappear from the universe. In other words, what we call now a black hole. Exactly. So it was like the first attempt at thinking about what we now would call a black hole.

But so that technically would be a dark star But I don't think that's what this question is about I think they're asking if matter can make planets Can dark matter make planets? No, I mean, I think he's asking about my work on dark stars Oh! And dark stars are not made a dark matter. They're the first stars that form

And they would be made of ordinary stuff, ordinary hydrogen, ordinary helium Almost entirely But they're powered by the dark matter that's inside them But it doesn't, so it's ordinary matter powered by dark matter. This is one of your early papers. It's instead of by, there's no fusion, it's dark matter power. Wow. Yeah.

That's some crazy, innovative stuff. And these things, if they exist, these things, I'm so excited because we have candidates for them in the James Webb Space Telescope. I'm so excited. They would start out at about the same mass as the sun, but then they would grow, grow, grow, until they become a million times as massive as the sun and a billion times as bright. They grow because they're absorbing dark matter. No, because they're absorbing ordinary matter. Normal stars can't keep growing because their surfaces are hot.

You know, they have fusion. Fusion's hot. Right. And then so they blow stuff off. But dark stars are cool. Oh, in radius, they're 10 times a distance between the earth and the sun. So they're huge. They're huge and they're cool, which means they can keep accreting mad.

They grow, grow, grow, and they get really, really big. So there's no pressure on the outer surface to prevent new matter from accreting to it. Yeah, exactly. Exactly right. Yeah, yeah. So they can get really big. and we have candidates in the James Space Telescope for some of those really early objects

that are super bright and they don't know how to explain him. Well, we'll take them. You'll take him. We'll take them. Whoa. Yeah, I'm excited. When you win your Nobel Prize,

will you come back on their show? Was that a kiss-off? No! Okay. Can you read the body language? That was a very, very... Oh, no, I'm sorry. No, he's still learning social cues.

Oh, no, no. I'm at the opposite. Oh, okay, cool. Yeah. I'll tell you this much. He's right, that is Nobel stuff right there, man. That's fantastic. You know, the thing about Astro about my field is that you can have a great idea. And let me back up.

Usually, when you have a great idea, you kill it in 10 minutes because it violates some observation. Occasionally, it not only survives those first 10 minutes, but then people start telling you, did you know you solved this problem? Did you know you solve that problem? And that's what's going on here. We keep solving problems. So dark stars could explain a lot of things.

They could explain, once they die, the supermassive black holes that you see in the early universe. They could explain the blue monsters and they could explain the little red dots. And I figured you'd like those terms. Wow. Yeah. These are all, they're very bluntly descriptive stuff we see in the early universe. Because there's nothing nearby that we have a counterpart to. It's a red dot.

Okay, so we call it a red dot. Now what about the blue monster? And wait to get that reference. Blue monsters are really, really, really bright objects way early in the history of the universe. Yeah, it should be like the formation of galaxies. I mean, we know they're blue. They don't look blue.

They look very infrared because that blue has been redshifted to the sweet spot of the James Webb Telescope. Yeah, yeah. Oh, yeah. Oh, that's very cool. Mm-hmm. All right. Okay, well, hey, what a great question, Anthropocos.

So she said she's coming back after her Nobel Prize. Well, absolutely. Now, here's the next question. Can I wear your Nobel Prize when you come back? So here's the best line related to that. It was from Hoop Dreams. Do you know the line? I don't know.

You know this line? You know the movie? I don't think I know Hoop Dreams. Hoop Dream. Dude. It's a documentary. Oh, you don't know Hoop Dreams. I do not know Hoop You Dreams, but go ahead.

Yeah, it's a documentary of following high school students, some who have ambitions to play in the NBA. Oh, okay. And the social dynamic that surrounds it. It's a documentary. But here's the line. When you're rich and famous, will you remember us?

As one of them goes off. And he says, if I'm not rich and famous, will you remember me? Oh, that's good. That's good. That's really good. I'm going to tell you, the answer to both those questions is...

Ouch. No. The answer? No. And to both. All right, let's move on. This is Nate. And Nate says, hello, Dr. Tyson, Dr. Freeze, and Lord Nice.

This is Nate from Southern. Idaho, if dark energy has gravitational effects on everything just like regular matter does, why does it not coalesce and push away from itself? This seems counterintuitive considering the fundamental nature of gravity is to pull things together by bending space time. Does dark energy abide by its own rules where it can cause gravity, but it isn't affected by it? This would imply that it is not influenced by the curvature of space time in which it causes. This guy did some thinking here. Fucking Nate, bro.

Whoa. Dude. Whoa. So let's start from scratch. Yeah. We're calling it dark energy because it's a placeholder term. We don't know what the hell it is. Right.

But if it's energy at all, then it has a mass equivalent and it should have gravity. So does dark energy have gravity? The definition of matter is that it fuels gravitational attraction. Mm-hmm. So that's true for ordinary matter. That would be you. And me and you. I was going to say, thanks.

He's not ordinary matter. He's not ordinary matter. And it would be dark matter, so all of that stuff clumps together is attracted together. And energy contains a matter equivalent. No, you know, for ordinary matter and energy, that is true. But for dark energy, it is completely different from matter. It is something that's causing a repulsive behavior. It's pushing things apart from one another.

That's why we should call it just Wilma, something that doesn't have the word energy in it. Yeah, yeah. So it's confusing because matter and energy in the ordinary world are related, but dark matter and dark energy are probably not. Okay, so the foundation of this question is not valid because it's assuming that it's participating in the curvature of space time, and if it's helping to make it, why isn't it responding to it? Why is it spreading things out rather than pulling things in?

Well, I mean, it does fit into Einstein's theory of general relativity. It's just that if you have this vacuum energy, it causes repulsion rather than attraction. It causes acceleration. So it's a completely different type of behavior. Yeah, but that fact, we calculated with that and you're off. Oh, 10 to the 120? Power.

Yeah, in the exponent. Yeah, that's true. Well, I'm not saying we understand it. I'm not saying we can calculate it. That's funny. Isn't that the biggest mismatch between a theory and a calculation ever? Yeah, it's really, it's just unbelievable. Vacuum energy, what does that mean?

well, what it means... By the way, there's vacuum energy in this room that you could measure. There are particle... It doesn't mean there's nothing. It means particle, antiparticle pairs that pop into existence. Yes.

They last infinitesimal amount of time and then they disappear again. But that serves as an energy. And it has been measured. There's been two plates that are... This is not the Kazimir effect. Yes, the Casimir effect. It is?

It's the Casimir effect. Absolutely. This is where two... In a vacuum, two parallel plates, you bring them very... very, very close together. And there's a point where there... They just attract, right?

Yep. Yep, yeah, yeah, yeah. Yep, yep. It's the same vacuum. The same, exactly the same thing. That's pretty wild. But if you do the mathematical calculation, your answer is too big by 10,

to the 120 in the exponent. So if you add up all the contributions from all those particles, it gets the wrong answer. And that's considered one of the biggest... It gets the very wrong answer. Yeah, okay. One of the deepest unsolved problems in all of physics. All right.

Wow. And it gets worse. People thought, well... It gets worse. It gets worse. People thought, you look, somehow, somebody will figure out how to bring that number down to zero and will be good. No. All of a sudden, it looks like there's a small amount left over.

Well, it's not that small for our universe, but compared to 10 to 120, there's dark energy, which means there is some vacuum left over that's driving acceleration. It's neither the big answer nor is a zero. It's somewhere in between. What the heck? All right. I'm talking too much. No.

No. We love it. That's the whole point of why you're on here. Exactly, yeah. Ooh, wow. If you're talking a lot, it means I have less to add. Oh. So it is, your words and ideas and brilliance are gracing the stage.

You're a real expert. All right, all right, all right. On some things. All right. All right, let's go to Sumit Sharma, who says, hello, Dr. Tice and Dr. Frees-Lord Nice. This is Sumit, from Delhi. I am a new member here.

Nice. Okay. Welcome. Welcome. Well, go ahead. You do it. Welcome to the universe. There you go. You got an official welcome there. In my Cosmos voice. That's right. I want to know where does the scientific consensus stand on WIMP as an alternative hypothesis to dark matter

today. I don't understand that. But anyway, I don't understand. WIMP is the abbreviation. I know weekly interacting mass and particles. It's a candidate for the dark matter. Oh, okay. But it can't be a substitute. But anyway. No, it is a type of dark matter.

It's a type. That's the answer. That's the answer. It's a type of dark matter. Also, since dark matter is invisible and hard to detect directly, what indirect properties or effects of dark matter are scientists currently studying and by what methods? I love that. Like, yeah.

So what's the deal? It doesn't interact with anything. How are you guys measuring it? How are you figuring out anything about it? You know, the thing about dark matter is we've got about 20 different candidate particles. that it could be. Okay. Some of them are well-motivated, and some are not as much.

So my favorite three would be Wimps, Axions, and Primordial Black Hole. Okay. So Wimps, the weakly interacting massive particles, they do have an interaction, which is the weak interaction, the weak force. Okay. And axions, what they do is that they can actually, in the presence of a magnetic field, they turn into photons, into light. so they can switch axion photon, axon photon,

and then you can detect that light. Now, primordial black holes, they would be black holes that formed very early in the history of the universe. They don't evaporate right away? Some of them do, so they have to be bigger than the smallest ones do. But there would be some left over,

and they form wherever there's some region of the universe that it has more an excess of stuff in it, and over-density that collapses into a black hole, And that, for example, could be at some phase transition in the early universe. This is like when water boils, it switches from liquid to gas. And that's where you get these fluctuations, and boom, you would make primordial black holes. And the reason people care nowadays is because gravitational wave detectors are seeing merging black holes. And some of those could be primordial black holes.

So people got all excited about primordial black holes again. Okay. As far as Wimps go, there's, oh, you can either to find them, you can make it, shake it, or break it. Right on. Go ahead, do your fan. Shake what your mama gave me. Let's talk about the make first. Make it or break it.

Make it, shake it or break it. So the make it is in particle accelerators, such as the large Haddon Collider at CERN, you shoot, really rapidly moving protons into each other, moving nearly at the speed of light. come potentially dark matter particles like WIMPS. And you look for them that way. No discovery yet, okay? So it would have a signature that you couldn't otherwise identify and you would describe it to dark matter. Yeah.

Because you otherwise know what you're supposed to get out of it. Yeah, if it's ordinary stuff, then you know what to expect. But if you're making some kind of new particles, then they might escape from the detector without, and you'd see that as missing energy. Okay. You'd add up all the energy of all the particles coming out and put there be some missing energy. All right, right on.

Okay, there you go. And do you want to hear about the shake it? Yes. Yeah, yeah. And break it. I mean, yeah. Now, we've got to make it. You can't leave without shaking it and breaking it.

All right. Okay, so the shake it is you've got your detector deep underground. And the particle comes along, hits your detector, gives it a little bit of, energy and you look for that energy deposit. So it's shaking that nucleus. It's like a little vibration. Exactly. In some cases, that's exactly what they're looking for in some cases.

Gotcha, gotcha. Or some light that comes off or whatever. So that's what they're doing. Okay. And then the break it, that's called indirect detection. And that's when, well, dark matter particles, these whims can be their own antimatter. And that means when they hit each other,

they annihilate and turn into something else. And what you've got to do is measure that something else. So people are looking for neutrinos, you know, where those detectors are? Underneath the ice at the South Pole. That's Ice Cube. Ice Cube. Yep. Two miles down.

Straight out of Compton. I mean, straight out of South Pole. Oh, that's good. That's good. That's good. Because Ice Cube was in straight out of Compton. Yes, he was. The actor, yeah.

Yeah, yeah, that's good. The rapper. We like that, yeah. All right. Yeah, that was great. What a great question, Sue Me, for your first time asking anything. thing here on StarTalk. From Old Delhi.

From Old Delhi. Make it, shake it or break it. Just remember that. All right. This is Chris Hampton. He says, Dear Lord Nice or Baron. Christopher Hampton, that was a playwright.

It's a playwright. Really? Okay. I'm not familiar with him. Yes. Oh, very cool. Is it a living playwright? I think so.

Okay. So it could be him. Mm-hmm. Okay. Treat him nice. There you go. He says, Dear Lord Nice or Baron.

No, actually you dubbed Paul Mercurial Barron. So it's just, which by the way, I found out there kind of the same, the titles, which, you know, we're going to have to demote Paul. I'm joking, I love him. Could dark energy be caused by a constant inflow of spacetime itself, perhaps through black holes from a parent universe? In other words, we're bringing more in than there is flowing out like a Britta flat iron system. Okay. Oh, wow. I'm not sure how to answer that one.

Britta flat iron system? Yeah, what the heck is that? I don't know what a Britta flat iron system is. I have a britt of flat iron system is. I put water in it. And it flows through and then I drink it. You know what Einstein had to do to get a static universe? He had to have

material somehow bubbling into our universe and appearing out of nowhere on a regular basis. So that is not an insane idea. People have thought about that. He knew what Isaac Newton's solution to that was. Go ahead. It was, if the universe were just finite,

then all the galaxies would collapse to each other. Okay. Okay. He didn't think of the universe is expanding. Right. But he said the only way out of this is if the universe is infinite. Then you can't favor one point or another. Oh, really?

Newton said that? Yes. Wow. Smart guy. You think? Damn. That's why he's sitting right over there on my desk. Did he know the universe?

Oh, well, that's because he didn't know the universe was expanding, right? No, no, no. No, no. No, no. That was 1929 that they figured out. Expanding universe. Einstein did not like it. Yeah.

Expand universe was too weird for everybody. For everybody. Yeah. He did not like it. What did Einstein say? Something about God or playing? He's always talking about God. That was quantum mechanics.

It was quantum, God playing dice. But the expanding universe, yeah. He didn't like the quantum mechanics. He didn't like the expanding universe. Isn't that interesting? That's wild. Which a lot of this is, these are fields of physics that he started.

He created. He's created. From the stuff that he was just like, the Nobel Prize is given to crumbs that fell off his plate. Well, I don't know what the hell this is, but whatever. Let's move on. That's him.

Wow, that's amazing. That's pretty well. All right. But when he says a constant inflow of space time itself. No. No. That doesn't make any sense to me, so I'm going to just say no. So space time can't come from another brain.

Right. Space time, to me, wouldn't clude all of that stuff. Gotcha. We're all living within space time. Okay. Okay. I'm a little uncomfortable with that notion. Okay.

Listen, I'll accept that because we are all living in space time, so, you know, that's pretty simple to accept. Greetings, STEM nerds. Yes. Mike from... Good. That's a compliment. Yeah, there you go, buddy.

Mike from Colorado here. Since the time of Edwin Hubble, we look at distant galaxies and calculate their speed based on the redshift we measure, which we attribute to the Doppler effect. However, we also know that photons lose energy when traveling out of the... the gravitational field, which also exhibits as a red shift.

Given that dark matter accounts for some 80% of the gravitational in the universe, how do we know how much red shift is due to the Doppler effect and how much is due to gravitation? Is it possible that the speeds we calculate for distant galaxies are just an upper bound on their actual speeds? Well, there are, on the average, galaxies are moving apart from. from one another, that's the Hubble expansion. That causes light between some distant past and us now

to stretch, the wavelength of light stretches. However, there's no question when you go, for example, some of that light, if it goes through a galaxy on the way here or goes through a cluster of galaxies, that also changes its wavelength. And in fact, we use that to figure out where a cluster is or what a cluster is doing. So it's useful information, and we're very,

very aware that you have both effects going on at the same time. So if you're inside our galaxy, like in this room, we're not feeling the expansion. We're not feeling it. I'm feeling it. Yeah, you're feeling it. So this reminds me of what they used to call the Tired Light model. The light is too tired. Right.

Come through. I've been through a lot, y'all. I'm telling you, traveling between these galaxies. I don't know. This is... Who Lord is killing me, man. Killing me. So tired light.

Because it would... I don't even have masks. I feel so damn heavy. Oh, y'all don't know. Y'all don't know. So... Okay. So tired light would be reddened.

Right. Okay. It would be reddened. However, there's also spectral features of elements within the spectrum. So, You could take regular light and it would redden, but if it's the expanding universe and it's Doppler shifted, the lines would shift. Yeah, yeah.

They would shift and had nothing to do with red or anything. They would just shift. Gotcha. And they shift. Yeah, they sure do. They sure do. Gotcha. And so you can still have tired light, but you can't blame that redness on the expanding universe.

Very cool. That's a good answer. And if we animate StarTalk, you will be the voice of the photon. I don't have a hug, dead. Wait, now, who's going to be the Wimp? Oh, and then, of course, before that, there were the machos. The machos. Massive compact halo objects.

So for a while we had machos. Mato and Wimp. Yeah, we did. Just show you that men were naming things. Yeah, right. And the experiments looking for machos? Ogle. Agle, yeah.

Aros. Ogle, Aros. And Machia. Yeah. Okay. Ogle. Optical gravitational lens experiment. Okay.

Eros. E-R-O-S. What did that stand for? I don't know. The God of love, like, stupid. Yeah, yeah, yeah, yeah. It's the only one I like. What's wrong with Venus?

Well, first, you, Agle, and that causes Eeros. We got time for one last question If you can answer it fast Okay go Okay here we go This is Brian Wheelan It's a test of view Brian Willen says

Hello Dr. Tyson Freeze and Lord Nice Captain Ben from Sag Harbor here Reaching out 30,000 35,000 feet in route home Oh he's Nice He's actually in the cockpit

sending us this message Oh because he's captain He's captain Wow Should you be flying a plane Well no At 35,000 feet The plane fly

itself. He's got time. He goes... Still. Yeah, still. This doesn't inspire confidence, okay? That's all we're saying. Okay, okay.

I'd rather you be drinking. Stop! All right. Drink it, but still paying attention. Exactly. He says, listen, I've been wondering, does dark matter coalesce and condensed similarly to regular matter? And if not, why not?

It doesn't interact electromagnetically, but would gravity do something similar? sending this message also on my birthday. Happy birthday, Captain Wheelan. Captain Wheelan. There you know. So that had some overlap with the previous question, but let me tune that a little better.

All right. If it interacts weekly, that's still an interaction. So why doesn't it just make weak planets instead of regular planets? Well, I'm going to say something else first, which is that without dark matter, we wouldn't exist.

It had to collapse and clump and make proto-galicies before, or, Ordinary Matter could do it. And then ordinary matter falls into those things. You're telling me that there are protogalactic dark matter galaxies out there? There were in the early universe, and then ordinary matter felled in there. But is it possible there are some purely dark galaxies that don't have any stars in them? Yes, and people are looking for that for sure.

Wow. Isn't that cool? Wait, wait, wait. Okay, yes. Very cool. Very cool. So it wouldn't so much be dark, because that would imply it would absorb. but they don't interact with light.

They would just be invisible. Well, made a dark matter, right. So there's nothing to see. There's nothing to see. Well, except that... No, no, no. If it doesn't interact with light, then light just passes through,

rendering them transparent. No, because of Einstein's Lensing, gravitational lensing. Oh, you see the lensing effects. You see distant galaxies, the light from behind the dark galaxies will get bent. Okay, so it gets bent. So you'll see that.

But the galaxy itself, or the dark, matter thing itself would be invisible to you right you could just walk through it and you wouldn't even know yes oh that's cool there's some serious science fiction material there is yes yes interesting i love it chuck have you met my dark matter friend oh well he looks like a black rabbit what's a black rabbit harvey the rabbit there you go oh harvey was a white rabbit he's dark matter It's a black rabbit. Oh, sorry. I just went too far too fast.

I went too far too fast. This is what happens. Well, Katie, thanks for joining us again. Thank you. That was fun. It was good. It was really fun. Another great show.

Now, if I remember correctly, you have kin in the city, so you get... My boy, my son. Your son, so you get through town every now and then. I do, all the time. We will nab you 100% of the time. I have a rent-stabilized apartment. I just signed a two-year lease, so I'll be here. Whoa.

All right. Whoa. Yeah. Okay. Okay, we will, every time you come back here, you're coming right here, you're going to sit right there. And actually, those queries were fun. See, even though you hadn't heard and were seen them before. That's right.

Yeah, okay. We're good. All right, good. Well, the audience knows you now, so believe me, they got a lot more questions for you. You got it. Sounds great. And you guys are so much fun. Oh, well, thank you.

Yeah. Well, there, let me pick a bit fist bump on that. All right, all right. We'll take it. This has been another StarTalk Cosmic Queries, a cosmology edition. I'm loving these. Nice. And how many cosmologists we got?

We got Jana. We got Brian Greene. Oh, Jan 11, just so you know, was my first graduate student. Whoa! Whoa! Yeah. Very cool. Look at that.

Okay, we have the two Bryans. Yep. We had Brian Cox and Brian Green. What more do you need? Yeah. We got Chuck Blue, too. Oh, Charlesville, but he's not deep cosmology. He's an extra galactic guy.

He's an extragalactic guy. Yeah, yeah. All right. We got enough. Yes, enough, definitely. Anybody else out there, come on. All right, we got to call a quits there. Chuck, always good to have you.

Always a pleasure. Katie, you're going to be a regular from now on. That sounds great. All right. Love it. You got it. Neil degrass Tyson, you're a personal astrophysicist, as always bidding you to keep looking up.