StarTalk Radio - Cosmic Queries – Stoner Edition with Janna Levin

Episode Date: March 8, 2022

Is anything real? Is time just a construct? On this episode, Neil deGrasse Tyson and comic co-host Matt Kirshen answer your far-out questions about black holes, dark matter, and the universe with astrophysicist Janna Levin. NOTE: StarTalk+ Patrons can watch or listen to this entire episode commercial-free here: https://www.startalkradio.net/show/cosmic-queries-stoner-edition-with-janna-levin/Thanks to our Patrons Ivan Masjuk, c, Nathan Mitchell, Conner Kemmsies, Dustin Dewayne Hart, Kyle Reinsberg, Andrew Magri, Virginia Cohen, Cathleen Corrie, and David Claassenfor supporting us this week.Photo Credit: Les Bossinas (Cortez III Service Corp.), Public domain, via Wikimedia Commons Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk. Neil deGrasse Tyson here, your personal astrophysicist. We're going to do cosmic queries today. Everything black holes in space time. I got with me my co-host Matt Kirshen. Matt, welcome back, dude.

Thank you. Thank you. I'm joining you from my family's spare bedroom in London right now. Oh, you mean your parents' basement where you live. That's exactly it, yeah. I commute to L.A. every day from the basement where all my toys and games are. Every day from the basement where all my toys and games are. I knew you were a full geek, but the whole story is still in your parents' basement.

That's it. You can confess that. You're in safe grounds here. This is no judgment podcast. No judgments at all. Good to have you back. And you're the host of Sometime Science? Probably Science, Neil. Probably Science.

Probably Science, on which I have been a guest. You have indeed. I have, and I enjoyed my time there. So, Matt, while I know a little bit about black holes and a little more about space-time, I don't count myself among the world's experts, but we have a friend of StarTalk who is, of course, that's Jana Levin. Jana, welcome back to StarTalk. is, of course, that's Jana Levin. Jana, welcome back to StarTalk. Thanks. I'm glad to be here. Yeah, yeah. Jana, you're like a neighbor up the street from the American Museum of Natural History. You're a professor of physics and

astronomy at Barnard College of Columbia. And it's just great to have you, just a friend of what we do and a supporter of all of this. Yeah, I love being here. And to lend your expertise. You're not lending it because we're not giving it back. You're giving us your expertise on black holes, cosmology, the space-time continuum, and all that goes with it. So just before we start off, I just want to alert people that in your spare time, you actually are one of the founders of a marvelously conceived project, Pioneer Works, over in Brooklyn across the river. You merge art and science in highly creative and imaginative ways. I just want to congratulate you on even going there.

And you've been at it for like years now. Yeah, I really appreciate that. We have a live programming where we feature scientists in conversation. You've been over. We've had parties with you, Neil. But you haven't put me on the stage. No, I'm waiting for the right time.

I have also been there and not on the stage. They didn't want my expertise but I went to... Matt, you and I don't cut it. Not there yet. Good enough for the audience, but not to actually do it. I mean, I think I'll get there eventually, but I'm not so sure about you, Neil.

I've got some deep expertise to share. I'm happy to put you both to work. Be careful what you wish for. So the big project there has been lately broadcast, Pioneer Works broadcast since the pandemic, which is our virtual manifestation. It's Pioneer Works Beyond the Walls, where we cover art, science, music, tech, kind of multimedia extravaganza. Excellent. So now you can reach a far greater audience than who shows up in Brooklyn. All right. So Matt, you collected questions from our Patreon members.

They have exclusive access to our Cosmic Queries format, and everyone else gets to hear their questions. What do you have lined up for us? There's a grab bag of black holes and stuff. Yeah, there's a really nice assortment of questions. I'm going to start off with this one

from Matthew Power, my kind of superhero namesake. That's, uh, but, um... You're Matt Kirshen, and this is Matthew Power. This is Matt from New Jersey, who is also currently reading Black Hole Blues, which is one of Jana's books. I've read that. It's an excellent book,

and Matt is also enjoying it. And Matt says, my question is, if there were two black holes orbiting one another and generating powerful gravitational waves, is there a possibility that a small object, he says perhaps a ping pong ball, could actually be carried away by the waves,

thus making gravity a repulsive force in this particular case? Wow, this is like a surfing ping pong ball. Wow. I love it. That's, what do you think, Neil? Oh, I love the idea. So because probably he's thinking deeply because if you're surfing on a wave in the ocean, the water isn't actually

moving. It's just going up and down and you're somehow exploiting this fact. Moving with it. Yeah. I think it's a subtle question. I've wondered about this, but I haven't ever really worked it out. I'm sure somebody might off the cuff know the answer, but definitely what you're doing in space time, if you're near those two black holes, is you're falling freely. We literally call it free fall. So you're falling freely on the natural curves in the space. So if those curves are changing, that's certainly going to change your fall. For instance, the earth is falling around the sun on a curve, on a circle. And if the sun were to disappear tomorrow, the gravitational

waves would radiate out, taking the time it takes until it reaches us. And then we'd go in a straight line as though the sun was gone, right? So in some sense, we are definitely moving with those waves. But thinking of it as like surfing, it's cool. I don't know. Right.

If we're not so heavy as the earth, let's say, or something as responsive as a ping pong ball, wouldn't the waves, wouldn't the expanding gravitational wave from the disappeared sun or from the collapsed black hole, will that have any effect on us at all to push us? How can a wave move out, but we can't now move with it? Yeah, I mean, the gravitational energy in the wave can be quite powerful, right? The collision of the two black holes was the most powerful event human beings have detected

since the detection of the Big Bang, right? And all of it came out in the gravitational waves. But actually, I think their effect is really quite weak. In the sense, you would feel the squeezing and the stretching as you kind of bobbed around on the wave, but I don't think it would have enough power to actually carry you along. But we also do know, I think the question was also about repulsive gravitational forces. And actually we do know that gravity can be repulsive. So for instance, the dark energy in the universe

creates a repulsive effect on the expansions. The universe is expanding. Things are getting farther apart because of the dark energy, and that's happening at an accelerated rate. Yeah, but you're calling that gravity, and are we allowed to do that yet? What do you mean? In what sense? You say, well, there's this dark energy, and it's actually the opposite of gravity. So are you legitimately calling it negative gravity? No, I'm not calling it negative gravity. I'm saying that when we think about curved spacetime, that coming together is not the only possibility.

Although that is with Newton's laws. In general relativity, when I think of dark energy as a particular source for the way it deforms spacetime, we see a very clear example where its effect on space-time is expansive. Oh, wait, wait. I got a good answer. I got another good answer. Can I raise my hand? Jana, I'm raising my hand in the front row. You're the boss. You're the boss. Okay.

Kneel. Kneel. Thank you. Thank you, Jana. So just thinking about this more holistically, the very expansion of the universe is carrying galaxies in the fabric of the expanding space-time. So in a way, we are moving, in a sense, not through space, but with space. And space is carrying us yeah i know it's not a gravitational wave but it's uh i'll take it as something it's sort of surfing even if it's not yeah that's excellent the dark energy is just a particular example of that causing the expansion in an accelerated way but lots of things cause the universe to expand like the fact that it's full of light and energy

in all directions causes the universe to expand. And I think you really hit it on the head, Neil. We are moving with the expansion of the space. We are not moving with respect to our local area, right? So that is like the surfer riding the wave. Yeah, yeah, cool. All right, Matt. Well, I'm going to jump from a question that is very theoretical to one that I know you have a good answer to, because I know this is something you've both been asked before.

Alexander Newhouse wants to know, what is the universe expanding into? Yeah, Jana. Anybody wants to know that? I know you've done this a bunch of times no no i just make stuff stuff up what i think what i've read but you actually work on these problems yeah so let's hear it out of the horse's mouth well uh if let's take it as though the universe was expanding into something just pretend Then we would be saying, oh, there's some distance the universe has traveled into this other space. But what we mean by the universe is the space. So there's really no logic to thinking of it expanding into something else. The universe is the whole space.

There are some relational possibilities that you can think of where the expansion of the universe is like a map of the universe where we're only reading the legend between things as changing over time, but the map itself doesn't move into anything else. That's one kind of very strange relational way of thinking about it. But no, we do not need to nest the universe

into another universe to have it expand But no, we do not need to nest the universe into another universe to have it expand. Okay, I get that. But, but, who, what, okay, so let's up this game a notch. What conditions would, what dimensionality, what location, what state of existence must one have to observe the entire expansion of our universe? Well, you, okay, that's... From the outside. So there is no way to stand outside the universe. No, not really, but so what?

I think you're trying to disprove the existence of God with me right now. What kind of trouble are you getting into? I don't think I really mentioned God in that. Nobody can see and know the entire universe at one time. There's no way of... Yeah, who are you to say that you can't, there is not some platform, some vista outside of everything we know and see that can just simply observe what's going on.

Well, by observe, we mean collect particles and interact. And we do that through POWs in space time. So if you want to literally be in a position where you're gathering lights so that you can see the universe and deduce what's happening to it, you're really talking about interacting with something. And that requires that we be in the same universe. Now, I mean, you could fundamentally say. You're no fun. You're no fun. We could say things that I think are actually quite.

Matt, she could have said, God is out there and he's watching us all, right? Or Santa Claus. He knows when you are bad or good. And then we sing some hymns and then roll credits. So it is interesting to push this idea and to say, look, these ideas about space being infinite or being finite or expanding, these are just ways of talking. infinite or being finite or expanding. These are just ways of talking. We could also talk differently about the entire universe only as relations, only as interactions. And that's the only thing we understand, that interactions happen over a certain span of space and time. And there's no need to even think about geometry at all or to think about the universe as a space at all. It just appeals to our intuition. Wow. Okay. You're looking at me like I've had this woman on the show

many times. Okay. Matt, she's crossed over. I crossed over. And I don't know that they're bringing her back at this point. Okay. I mean, and we know that we're often fooled by these interactions. So right now I have the illusion that you're a solid person, that Matt's a solid person, but really you're mostly empty space. These are illusions that we cling on to to more easily comprehend the world, but we know that they're not true. Matt is mostly empty space. Yeah, a lot of people say that about me. I'm solid. Neil is solid.

I'm solid here. There's nothing going on in here. So, Janet, you're referring to the fact that atoms are mostly completely empty. Right. And then even if you look at fundamentally what the fundamental particles are with atoms, we only understand them in terms of the way in which they interact with things. That's the meaning of an electron, is the way it interacts with things. So, in some sense, we're just these sort of lists of interactions.

Yeah, she got all philosophical. That's making me very much... Quickly, go to the next question before this gets worse. Because you got so philosophical, I'm going to jump onto Scott Allen's question because Scott from Arlington, who, by the way, gives the caveat

that Scott is stoned right now. Okay. I'm putting that right in there. And if Scott is still stoned trying to listen to these answers I think we're going to put him into real trouble we should do a stoner version of this show I'll host it and just get my

I mean that basically is my podcast that is probably why we're just winging it star talk for stoners oh my gosh we get all the topics best best suited for when you're high. Oh my gosh. You know, Janet, we'll bring you back.

That's going to be a show. I promise our audience, that's going to be a show. I just fall asleep. It'll be a very boring show. While you're eating potato chips. So Scott says, is everything just a form of energy? Is time just a human invention? Combining the two ideas is what we call life and everything we can

observe and understand with our limited senses and minds simply a flow energy constantly changing form. There is no beginning, there is no end, there is no past, there is no future. There is just the present in whatever form of energy we can sense and understand with our mind. That is Scott's question.

Make of that what you will, professional scientist. Yeah, okay. Wait, did you just give the answer and you said definitely, and now you can move on to the next question? I think the answer is yes, and everything's fine right now. I just think he's definitely stoned. That is such a stoner question.

But let's think about this. What confidences do – I'm going to rest stoner question. But let's think about this. Is, is, how do, how, what confidences do, I want to restate the question. What confidences do we have, Janet, can you and I offer as scientists that there is a physical reality? And just, we're not all just perceiving ourselves in the moment. Yeah, I mean... What evidences do we have? I think you made it worse for me, man. The universe has meaning and existence outside of our perceptions.

Yeah, I mean, which one of us is the one perceiving? Am I in your mind or solely? Or are you solely in my mind? Or are we both in Matt's mind? Which one of us is the genius? Or are we both in Matt's mind? Before Scott started combining his ideas, there are two questions

at the beginning that I don't are more grounded in, I think, physical theory that is everything just a form of energy and also is time just a human invention? And I think those two are questions that are potentially

more answerable. Well, to deal with the first one, yes. I think matter and everything is a form of energy that interacts in described ways. Wait, Janet, you just don't think that. You know that. Janet, be careful how you use the word think, okay? Like, you think it't think that, you know that. Janet, be careful how you use the word think, okay?

Like you think it might rain tomorrow, but you know matter is energy, okay? Right, it's true. We know that matter is definable essentially. Yeah. And that is interesting. I mean, I think that's also related to this kind of tangent we went on, which is that what does it mean to have atoms in your body? What does it mean to be made up of atoms?

It means that you have a certain amount of energy and that those particles interact in very prescribed ways. That's what makes an electron different from the positron, is just the prescribed interactions, if not their energies. So, yeah, that's really all we are. It's beyond that to say what's real. It's, again, part of this illusion we have to cope with our perceptions of the world. We'll take a quick break, and when we come back, we'll pick up the second part of that question, whether time is just some kind of a human construct, with the help of Jan Eleven, giving us her insights into the universe on StarTalk Cosmic Queries. I'm Joel Cherico, and I make pottery. You can see my pottery on my website, CosmicMugs.com.

Cosmic Mugs, art that lets you taste the universe every day. And I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson. We're back. StarTalk Cosmic Queries. I got Matt Kirshen as my co-host. Matt, how do we find you on social media? I'm Matt Kirshen on Twitter. I think Matt underscore Kirshen as my co-host Matt, how do we find you on social media? I'm Matt Kirshen on Twitter I think Matt underscore Kirshen on the Instagram I very rarely use Twitter's the main place I am Okay

And if you don't know the spelling just kind of get vaguely close and Google will find me Yeah, okay And we'll find you on Twitter then without the underscore because that's where you mostly are That is, that's me

And Jana, tell me about your social media footprint Yeah, I find you on Twitter then without the underscore, because that's where you mostly That is. That's me. And Jana, tell me about your social media footprint. Yeah. I'm more on Twitter, at Jana Levin. Two N's, like Anna. And I'm on the Insta, same handle. I sort of treat them a little differently. On Instagram, I kind of post my personal stuff, my personal business. And on Twitter. Okay. We want to get all up in personal business. And on Twitter.

Okay, we want to get all up in your situation when we go there. Okay. You know, yeah, exactly. You know, not exactly what I had for lunch, but yeah. So, but Twitter, I have pretty serious conversations with people if they want to ask questions, I'm there. I love answering questions when I'm in the mood, at least, you know. Okay. Very good. Very good. All right. So, we left off. What's the name of that last questioner? So Scott, we left off his part of the question was, is time just a human invention? Yeah. So Janet, the only thing I can say about time is a quote I remember from Einstein or from his student, John Archibald Wheeler, was it, time is invented to make motion look simple.

Have you heard that? I have heard it. I feel like it was Wheeler because he said lots of witty things. I also think it was Wheeler. He said time is what keeps everything from happening at which is a good one yeah okay um so and just just i gotta throw it throw it in here um i first noticed the woman who would become my wife in a class taught by john archibald oh wow no way i didn't know that yeah we took the class together yeah i was sitting in the back row she was in the front row so i i don't, she probably didn't notice me, but I noticed her. I can say I noticed her in the space-time continuum on the chalkboard. Right. Okay. So what do you have to say about his comments? Well, I think, I definitely don't think it's a human construct. Whether time exists in this

kind of block time model of the universe where the past exists, the future exists, every bit as much as left and right exist. But we're confined on a particular path through this four-dimensional space where time is the fourth dimension. That wouldn't be just human beings, though. That would be everything would be confined to that space. I presume my cat's death comes before it's, you know, after its birth rather. And, you know, I just presume flowers die after they bloom and that those are things that are happening to everything in the universe. There are other models that time is sort of not an invention of the mind, but it's like it emerges from very subtle processes and that in some sense it's not fundamental. But I think that, again, it's a very good thing to talk

about. So if we want to meet, we don't just specify a point in space. We have to say a moment in time and it's very convenient that we all are able to find that moment in time and collect and get together at that moment in time. So that suggests it's not just a figment of our imagination or a human construct. So maybe I should save this for the stoner edition, but if you could find a region of the universe where nothing changes, then time cannot possibly have meaning. Absolutely. And in fact, that's kind of a death of the universe model.

That the universe will, everything that can fall into black holes will possibly, if the expansion doesn't dominate. And those black holes will evaporate into random particles. And then the expansion will just make it so that there's only one particle in the entire observable horizon that, you know, and that's disconnected from all the other particles. And so there will be no meaning to time passing. I mean, even for me to experience time passing, there has to be change, which is my thoughts changed, my breath accumulated. There's actual measurable change that I experience as the passage of time. true that we do have internal clocks, but they are very well aligned with our external clocks, making it seem as though there is something external and universal. Well, while we're talking about external and internal clocks, Jeff Johnson wants to know, why does gravity or high speed cause an entity to move faster through time?

Oh, I see the question. Time dilation is the question. Yeah. Why does time? So, um, but first, first he got it backwards. So gravity slows down time and that speeds it up. Yeah. So it doesn't actually slow my experience of time. So my experience of time, if I'm standing near a black hole is exactly like very ordinary. My nicely made watch that I had once synced with my friend back at a safe space station is working perfectly well. It's still matching the number of breaths I take. Time seems to be passing completely normally.

Your heart rate, everything. My heart rate, everything is absolutely normal. I don't get any benefit out of this dilation. The dilation is only relative to somebody far away. And to somebody far away, I look like I'm moving slowly, like I'm breathing slowly, like I'm aging slowly, like my watch is ticking slowly. So it's only relative to them that it looks odd. But in my experience, it's quite normal. I think the deeper question is, why does this happen? And we can think of both gravity and moving quickly as creating rotations between the space times of two observers.

So if one observer thinks that this is left and another observer is facing them, they understand that they're going to disagree about which way is left. They're not surprised. But they know they can just rotate their systems and then they'll agree, right? So in some senses, you go closer and closer to the black hole. It's as though you're rotating in space-time.

So some of what you were calling space is folding into some of what your friend was calling time. And that leads to time almost as though you're rotating left into right, almost as though you've rotated time away entirely relative to your other observer. So Matt, we should

just rename this show Star Talk for Stoners. I don't think it's fair that we got stoned. It is happening in front of our eyes, Matt. There is a beautifully related question as well on this note. Wait, wait, wait, Matt.

I just got to wrap my head around what Jana just said. So, Jana, what you're saying is you use the left-right as an interesting analog to this. What you're saying is when you are moving faster in the vicinity of a black hole, your time coordinate is, let's use the term, rotates in such a way that it's giving of itself to a space coordinate. That's right. So one is losing time relative to the other. Exactly. And just like you can rotate left all the way into right, at the edge of a black hole in particular, you've basically rotated your time away entirely.

And in fact, when you cross the event horizon, what your friend far away thought was a region in space, a center of the black hole, is for you a direction in time. So you've rotated it completely by the time you cross the event horizon to the point where you think that the dire singularity at the center isn't a point in space at all. It's in your future. And it is as inevitable that you will crush into that singularity as the passage of time is inevitable. So you can't dodge the singularity of the center of a buckle. That was Roger Penrose, wasn't it? Yeah. Actually, I wrote this little article after he won the

Nobel Prize for that beautiful work in 1965 for Pioneer Works broadcast, actually, because we do this series called Picture This, where you draw, we scientists write about technical articles, like technical drawings. And Roger Penrose has the most wonderful drawing that he drew in this 1965 paper where he shows basically time starting to move in a spatial direction.

He shows that rotation. And he proves that at the event horizon, what's happened is basically time is starting to point inward towards the black hole. It's quite beautiful. And I love the left-right starter analogy there. You know what that reminds me? So Matt, have you ever heard this joke?

It's funny. It says, so someone says, well, two wrongs don't make a right, right? But then you can say, but three rights make a left. You ever try that? Just try it. Make three left turns, you just turn right. If you do the geometry on that, it works out. All right, cool.

Jana, thanks for that answer. I think we should rebrand this for stoners, a.k.a. for stoners. The right, cool. Jana, thanks for that answer. I think we should rebrand this for stoners, aka for stoners. The stoner edition of Cosmic Queries. Matt, keep them coming. Well, so Frederick Johansson asks, and this is related because you just talked about the difference of effects of both speed and gravity. Frederick wants to know, if I stand on the equator, my head would age less compared to my feet due to the speed difference. But wouldn't we have the opposite effect due to gravity?

Would my feet or head age more in the end? So I believe he's asking that if he's standing on the globe, his head is moving faster than his feet because it's further out, but also his head is moving faster than his feet because it's further out, but also his head is further away from the gravitational center of the Earth than his feet.

So do these two things both have an effect on the time perception of your head and your feet? And if so, do they cancel each other? I would have to actually do the calculation because both are pretty tiny, right? But I can tell you that with like the GPS units, we see the effect of the time dilation when we send signals to satellites and back again, and they have two effects. One is you're deeper in the gravitational potential. So let's say we take the twins, like one astronaut that was in the ISS and the other

twin astronaut who stayed on Earth, the Kelly twins, which one actually was younger, the one who stayed on Earth deeper in the gravitational potential well or the one who was traveling and very quickly in the ISS? And it's actually a known answer. And I forget which one it was. I think the speed of the ISS dominates over being on the Earth in that case. I'm pretty sure. Okay. However, with GPS satellites, the fact that they are much farther away from Earth than the International Space Station, much farther away from Earth than the International Space Station, that they experience much, much less strength of gravity,

which speeds up their time relative to us. And so their time that they send us is pre-corrected to accommodate the fact that their clocks tick faster. So, right, Janet, you have to do the math, right? Because there are two competing effects to know for sure. But I agree with you. Everything I know about the orbiting astronauts, which are in low Earth orbit rather than middle Earth orbit. Matt, it's not middle Earth, like, you know.

Right. Okay, just to be clear. Orbit. Key word there. It's not a basement, Neil. I'm not in a basement. It's Leo, Mio, and Gio, right? Low Earth orbit, middle Earth orbit,

and geosynchronous orbit. So when you do the math there, the lower gravitational field wins out over what effect their speed has on their timekeeping. Oh, interesting. Yeah. Interesting. So thinking about the GPS, we could also think about how if we didn't correct for the time dilation, we would never be able to catch our Uber because it wouldn't be in the right location. And I learned this from Neil recently, that it's actually the rotation of the Earth that's the issue. That if the satellite, and let's suppose we lost a second, if the correction was never made and the error accumulated up to, let's say, a second, then if you consider how quickly the Earth is rotating and that the grid would be changing, you would find that we could be off by several blocks.

So you'd be trying to catch your Uber in Chinatown, and it would be in Little Italy. Which is five, six blocks away. My Uber's never where I need it to be. These are adjacent communities in Lower Manhattan. Yes, they're adjacent neighborhoods. Yes, yes, they are. For those who are not native to the city. Let's take a quick break, and when we come back, more Cosmic Queries. Stoner edition with Jan O'Levin.

We're talking about black holes, cosmology, and the space-time continuum. And I got Matt Christian to help me. We'll be right back. We're back. Third and final segment of Cosmic Queries, Black Holes in Space-Time Continuum Edition, which we are dubbing Cosmic Queries Stoner Edition based on the answers we've been getting and what kind of state of mind we have to be in

to even follow them, much less understand them. So, Jana, again, it's always good to have you here. Your last two books, so one of them was The Black Hole Blues, published by, was that Knopf? Yeah, by Knopf. Is that right? Yeah. Yeah, yeah. Black Hole Blues. I didn't know black holes had emotional states. Yeah, black hole blues. I didn't know black holes had emotional states.

Well, the people who were searching for black holes had emotional states. Oh, okay. They had the black hole blues. They had the black hole blues. Oh, I got you. So this is a story of black holes in our field of astrophysics and the relationship we have to them. Got it, got it. And more recently, you have a book called The Black Hole Survival Guide,

which is like a pocketbook, fits right in your coat pocket. And how useful did you, how soon do you think such a book will be useful where everyone has to have one? Yeah, they have to have a survival guide. Well, I hope not very soon at all, but we are in orbit. But for the sake of the sales of your book.

Let's stoke some worry in the public. I have a spoiler alert. It doesn't end well. The survival guide doesn't go well. It's pretty much many ways to die. We'll keep a copy of this in our go bag, right? When you're in disaster strikes. Don't you have a book titled Death by Black Hole? I've always wanted to steal that title from you. Oh, Death by Black Hole. Yeah, yeah, I do. It's one. So that title is the title of one chapter in a book that goes a lot of different places. Right, it was this collection of essays, as I remember.

Yeah, that's right. That's right. On all manner of things in the universe. Yeah, so the survival guide could also be called, like, Death by Black Hole. Okay, all right. So it's the non-survival guide. It's death by black hole. All right, Matt, what more do you have for us?

Well, I'm going to turn this to some black hole survival questions because we've got a few and they're great. So from the Czech Republic, Patreon patron Jindrik Prokupek, I hope I've got that close to correct, asks you, I read that black holes are almost zero Kelvin inside. Why are they so cold and not very hot due to a high pressure caused by enormous gravity forces and lack of heat escape? And is there a temperature gradient between a black hole center and its event horizon?

And what's zero K anyway, Janet? Oh, literally it just means particles are so cold. They have so little energy that they're just not moving. It's as though, you know, we experience temperature. What we're really experiencing is the collection of atoms moving at a certain rate and a certain speed on average. And that creates the temperature. And the faster that they're moving, the hotter it feels. And the slower they're moving, the colder they are. And it is true.

There's an expression PV equals NKT that, you know, in highly pressured situations, the temperature can go up. Right. That's the thing. The level of physics that I understand, like a bicycle pump gets hotter. And if you spray one of those compressed air canisters, they get cold because you're... Yeah, exactly. Jenna, I can't believe you wrote it on the chalkboard. I love that Jenna's in front of her. The people who are audio-only are not aware

that Jenna is... You look like you're posing for a professor photograph right now. What were we talking about? Oh, do you know what I'm talking about? We were talking about the compression of everything. Matt was sharing his life experience that in a bicycle pump,

you, because he's living in his parents' basement, he doesn't own a car, he just has a bicycle. So in his bicycle pump, the valve gets hot. All I've got is compressed air

to keep me happy. Right, and a spray can as the air releases, the nozzle feels cold. So the pressure can heat up or cool it, depending on which way it's going. So what's happening inside a black hole? Is the person right

about it being zero? No. But they're not right for a very interesting reason. So we know that as the core of a remnant star, what's left after it goes through some very violent throws at the end of its life, continues to collapse and is in fact extremely dense and probably absolutely an unusual, which aren't even black holes. They're a step on the way to black holes. They don't quite make it there. And we know that they're incredibly unusual in terms of their composition.

But once it makes it to be the black hole, so it has created a curve in spacetime that is so sharp that we know not even light can escape. That's what we mean by the event horizon. sharp that we know not even light can escape. That's what we mean by the event horizon. And you might think, therefore, the event horizon, the black hole is full of dense stuff, but it's not actually because the star can no more sit there than it can expand outward at the speed of light. You can almost think of space time as like a waterfall raining into the black hole, and it would have to swim against the waterfall just to stay at the event horizon. And it can't do this, so it just continues to get dragged in with the waterfall of space-time. And, you know, this is the great mystery. What happens to the star? We don't know. But it's gone.

The star is gone. So black holes are cold because they're empty. So if I go up to the event horizon of a black hole, nothing's there. There's no dense object. There's nothing solid. It's empty space. So I like to say, you know, and I've said this, I'm sure, on your show before, black holes are more like a place than they are a thing. They're like a place in the universe, but there's really no matter left. But you can measure the gravity that it has, right? So something's got to be there.

Yeah, that's right. It has gravitational energy in the curvature of the spacetime. There is energy in the curvature of the spacetime. That is a gravitational energy. So it's often really hard to define gravitational energies. But in the case of a black hole, I can actually have a well-defined mathematical prescription for measuring its gravitational energy, and it happens to equal, not surprisingly,

the mass of whatever fell into it. So it's as though the matter throws its heft into the gravitational imprint, but the stuff is gone. Now, there's another question you could ask about temperature, which is about the Hawking radiation. So at the event horizon, we do think that through this very subtle quantum process, black holes do have a temperature, actually, and they are radiating, actually.

But the bigger the black hole, the colder they are. And the smaller they are, the colder they are. And the smaller they are, the hotter they are. So they're very cold. They live their lives absorbing things, not emitting. But at the end, in the very, very far, far, far future of the universe, those black holes will eventually evaporate away, and the final stages will be explosive. Yeah. In fact, if I remember correctly, the original paper that described this phenomenon by Hawking explained these as that they would be bursts of high-energy gamma radiation because right at that last moment would be at its hottest and very hot things emit gamma rays.

Exactly. And so it's interesting. Yeah, so, you know, if you, if you are foolish enough to try to make a black hole in the laboratory, it will explode on you because the smaller they are, the more unstable they are. And you can kind of figure out like, how big would it be if it was like kind of a stick of dynamite versus what you're describing gamma rays or nuclear weapon grade. And, and you, so you're kind of ill-advised to make a small black hole. But if you do, you should start with a bigger one just for safety. Well, then you're going to fall in. So you got to, you know, it's a real, so I tried to.

Wow, what a trade-off that is. And Earth, it could suck in the Earth. So yeah, that would ruin your day. That would ruin a lot of days, people's days. So we can't, so Janet, we can't call a black hole an area of nothing if it contains the severe curvature of the space-time continuum, because that is something. Yeah, I guess, right, that's fair.

We can say, what do we really mean by nothing? Man, notice how she didn't say it was right. She said it was fair. You're absolutely right. Space-time is something, and space-time has energy. It's a thing. Space-time moves, and it's a thing. And in that sense, it's a thing.

But it's also, by definition, space, which is a place. I'll take that they very much act like things. Black holes move around. They orbit. They can move around. They orbit. They can fall together. They can collide, you know. But when we talk about the size of a black hole, we're talking about a shadow.

That's all we're talking about. We're talking about a shadow, like the shadow of a tree. And there's nothing there. No matter. While we're talking about matter, so listen to Gonzalo Castilla from Mexico. And Gonzalo mentions black matter. I'd imagine this is what we would also call dark matter,

unless there are two different things. I think it's probably dark matter. So I'll say dark matter for this. I'd imagine that's a language thing. But if dark matter can interact gravitationally with normal matter, it is attracted and eaten by a black hole just like normal matter, right? What happens with the dark matter as the black hole evaporates? Could there be a dark matter version of Hawking radiation or it only radiates normal matter and a black hole has some sort of mechanism that transforms

this dark matter into normal matter? So, Jana, that's a really interesting question. Oh, my gosh. But as we're running short on time, can you like soundbite that answer? Is that possible? Yeah, absolutely. The black hole will figure out how to radiate all of the information that went into it, if this works. So, that includes dark matter information. So the fact that it was dark would come out in principle. Everything comes out. Okay, so Hawking radiation, that calculation does not discriminate between ordinary matter or dark matter or any other kind of matter.

Nope. It can be electrons and positrons. It can be light coming out in the Hawking radiation. It can be dark matter pairs, pairs of dark matter. And that assumes, so everything you said assumes that dark matter is actually comprised of matter and not some other mystical substance. Right. Okay. Right.

And there are people who think that black holes themselves might be enough to explain the missing mass and the dark matter. Yeah, I'm not among them. So that's not a particle answer at all. Yeah. Yeah. Okay, Matt, keep them coming. All that's not a particle answer at all. Yeah. Okay, Matt, keep them coming. All right.

So Dylan, there's a couple of faster than light questions. So Dylan asks, I've heard a lot about wormholes on this show and have a question. How would we open up a wormhole? I know as of right now, they're impossible, but hypothetically speaking, what steps are taken? How much energy would it take? And could we just use a black hole? How do we cut space time? Yeah, Janet, we're waiting for this. And why aren't you giving us the wormhole?

We're so disappointed. I know. I'm busy. I'm going to do it in the future and then come back. Oh, that's... I'm going to do it later. Good answer. Good answer. Matt, that reminds me, during the science march, which is sad that in the United States we needed a march to defend science back several years ago, one of the placards said, what do we want? Time machine. When do we want it? It doesn't matter. That's perfect. I think MIT once scheduled a time traveler conference for the previous year. They were like, let's meet in 2019 and have a time traveler conference. Nobody showed up.

Nope. Yeah. Time travelers didn't show up. Yes. I can tell you this about the wormhole. We absolutely, on paper, know how to make a wormhole. So basically what you do is you write down the shape of the spacetime you want, namely a wormhole shape, and then you force matter and energy to create it. And you ask then, well, what does the distribution of matter and energy have to be to create this shape? So you can go backwards and deduce what kind of matter and energy would be required. The problem is it requires negative energies, and that's not something we see in our ordinary experience. Everything has positive energies.

Negative energies are super weird. Some people think that they're forbidden in nature. The one circumstance in which you can get negative energies is in some strange quantum situations. I've actually wondered about this. Could we create where you have like finite spaces made out of metals and the quantum oscillations or the quantum vibrations create a certain negative energy between like these strange geometric configurations. So you need the negative energy to pry open a hole that would otherwise on its own want to collapse and just make a black hole, I guess. Yeah. It just wants to keep pinching closed.

So that sounds really dangerous to enter one of these because suppose you're in one and then it collapses on you. That's a bad day. That would be really bad. Okay. So we're nowhere near this now, even though you can make it happen on paper. Yeah. I mean, you know, people like Kip Thorne, they were writing down wormhole solutions decades ago and they just looked around and said, well, we don't see any matter like that in the universe. So we got to go back to the drawing board and think of a new way.

Okay. So just because something is mathematically possible doesn't mean the universe is going to cooperate. That's really what it comes down to. There's other time machines that we know we can make. We can take two cosmic strings, which are literally strings of energy tension and energy density, and cross them in a very funny way that creates a kind of cut in space-time that allows you to do a little time travel jig. But the problem is, is they have to be infinitely long and take an infinite amount of energy. So there's never anything that seems compatible with the universe that we live in.

And even Kurt Gödel first, who was friends with Einstein, used to walk to the Institute for Advanced Study with him in the mornings to talk. And he was inspired by Einstein's work. And he wrote down a description of a hypothetical universe that was rotating, not our universe.

And he showed that you could travel in time in this peculiar space he invented. And Einstein didn't dispute it. It was correct mathematically, but we just don't live in those kinds of- Okay, just admit it, Janet. All we really need is 1.21 gigawatts. Okay?

That's really all we need. Just admit it. I believe it's pronounced gigawatts. Excuse me. So, Janet, I think we've got to call it quits there. We ran out of time. Oh, shame. It's always so fun.

Okay. So, Matt, with your permission, I don't want to call it the stoner edition unless we have total buy-in from the three of us. Can we call it that? I'm fine calling it the stoner edition. But anybody who knows me knows if I'm stoned, I'm asleep. Okay.

Synonymous. Stoning equals sleeping. And anyone who knows me knows I have a green card. That's right. Northern Europeans have green cards too. I have a green card, which means I can't get the other kind of green card. So we're good here. So Janet, thanks for coming back to StarTalk.

It's always good to have you. And continued good luck with, and it's not luck, it's your talent that helps make Pioneer Works what it has been and what it will continue to grow to become. So keep that going. Thank you so much. And Matt and I are still waiting for our invitation to be something other keep that going there. Thank you so much. And Matt and I are still waiting for our invitation to be something other than

in your audience. Now I can't wait. Oh, are you going to get an invitation? You got it. Matt, always good to have you, dude. Lovely to be here. Thank you for having me. This has been StarTalk Cosmic Queries,

Black Hole, Space-Time Continuum, which we dub the Stoner Edition. I'm Neil deGrasse Tyson, your personal astrophysicist. Keep looking up.