Cosmic Queries: Until the End of Time, with Brian Greene

Neil deGrasse Tyson, comic co-host Chuck Nice, and theoretical physicist and author Brian Greene answer questions from our fans about string theory, the fabric of spacetime, interstellar travel, free will, and the meaning of life.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Neil deGrasse Tyson?

  Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. StarTalk, Cosmic Queries Edition. Neil deGrasse Tyson here, your personal astrophysicist. And as is not always, but most of the time, Chuck Nice.

• 0:25Chuck Nice?

  Hey.

• 0:26Neil deGrasse Tyson?

  Co-host.

• 0:27Chuck Nice?

  Good to be here, man.

• 0:28Neil deGrasse Tyson?

  We just fist bumped in front of our guest.

• 0:29Chuck Nice?

  Yes, we did. There we go. Now we're doing a three-way fist bump.

• 0:33Neil deGrasse Tyson?

  Commuted property of fist bumps. Brian Greene is our guest.

• 0:37Chuck Nice?

  That's right.

• 0:38Neil deGrasse Tyson?

  We're doing Cosmic Queries Until the End of Time. I didn't just pull that out of an orifice.

• 0:44Chuck Nice?

  I was gonna say.

• 0:45Neil deGrasse Tyson?

  It is actually the subtitle of his book.

• 0:48Chuck Nice?

  That's the title.

• 0:49Neil deGrasse Tyson?

  It's not title.

• 0:50Chuck Nice?

  That's the title.

• 0:51Neil deGrasse Tyson?

  What's the subtitle? Mind, Matter, and Our Search for Meaning in an Evolving Universe.

• 0:56Chuck Nice?

  Nice.

• 0:57Neil deGrasse Tyson?

  That kinda means everything, right?

• 0:59Chuck Nice?

  It is. But doesn't the universe automatically elicit questions of what is my purpose? My meaning? Why?

• 1:08Neil deGrasse Tyson?

  That's why we have him here to talk about this for the show.

• 1:10Chuck Nice?

  Oh, cool. I thought we were doing a cooking show.

• 1:12Neil deGrasse Tyson?

  So, we solicited questions.

• 1:18Chuck Nice?

  Yes, we did.

• 1:19Neil deGrasse Tyson?

  About this book. I don't know, have people read your book already?

• 1:21Chuck Nice?

  Wow.

• 1:22Neil deGrasse Tyson?

  Is that possible?

• 1:23Chuck Nice?

  I'm looking at the questions.

• 1:24Neil deGrasse Tyson?

  I just know he's got a fanbase out there.

• 1:26Chuck Nice?

  He does. And there is several of the questions are people who have already, they say, in your book.

• 1:32Neil deGrasse Tyson?

  Okay, so Brian.

• 1:33Chuck Nice?

  Look, look at this one right here. Your book Until the End of Time brings me to the conclusion. Wow. Look at that. So, there you go, man.

• 1:40Neil deGrasse Tyson?

  All right. So, this is the Venn diagram that overlaps his fanbase with our viewers.

• 1:45Chuck Nice?

  There you go.

• 1:46Neil deGrasse Tyson?

  Because we solicited it from our viewers.

• 1:47Chuck Nice?

  From your base, yeah, great. There you go.

• 1:49Neil deGrasse Tyson?

  Our people, your people.

• 1:50Chuck Nice?

  I love that.

• 1:52Neil deGrasse Tyson?

  Alright, so Chuck, you got the questions.

• 1:54Chuck Nice?

  Yes.

• 1:54Neil deGrasse Tyson?

  Just to remind everybody how this works, it's Cosmic Queries. And, these are solicited from our fanbase.

• 1:59Chuck Nice?

  That's right.

• 1:59Neil deGrasse Tyson?

  I have never, not seen them, certainly our guest hasn't.

• 2:01Chuck Nice?

  That's right.

• 2:01Neil deGrasse Tyson?

  Chuck, you might have seen them.

• 2:02Chuck Nice?

  I've read them before.

• 2:03Neil deGrasse Tyson?

  And Brian Greene and I have very strong scientific overlap. Um, but we're gonna get his view on this, and I'll just sit back and listen. And if he's full of shit, I'll tell you. No you won't, no you won't. His guy will not sit back and listen. I've never heard that before.

• 2:22Chuck Nice?

  That was funny.

• 2:24Neil deGrasse Tyson?

  Plus, I should've said it differently.

• 2:26Chuck Nice?

  No you won't.

• 2:26Neil deGrasse Tyson?

  Brian Greene knows almost all the astrophysics I know. And I only know some of the physics he knows. So he can take my physics to new places. That is very gracious. I don't know if it's true, but it's very gracious, thank you. And, and he's a, he's, he's a good mathematician, too.

• 2:41Chuck Nice?

  Alright.

• 2:42Neil deGrasse Tyson?

  Yeah.

• 2:42Chuck Nice?

  I mean, I'm gonna say yes to that. Because he's an astrophysicist and a physicist.

• 2:48Neil deGrasse Tyson?

  Math is a language of the universe.

• 2:51Chuck Nice?

  Right, yeah.

• 2:52Neil deGrasse Tyson?

  In which he is fluent.

• 2:53Chuck Nice?

  Very cool.

• 2:54Neil deGrasse Tyson?

  I'm delighted to have an all-time friend and colleague.

• 2:57Chuck Nice?

  Alright. Well, let's do this, and as usual, we always start with a Patreon question, a question from our Patreon patron.

• 3:03Neil deGrasse Tyson?

  Oh, wait, wait, wait, I, excuse me.

• 3:05Chuck Nice?

  Go ahead.

• 3:06Neil deGrasse Tyson?

  Brian Greene is professor of physics at Columbia University.

• 3:10Chuck Nice?

  Wow.

• 3:10Neil deGrasse Tyson?

  And also joint-appointed in the Department of Mathematics.

• 3:13Chuck Nice?

  That's wow.

• 3:13Neil deGrasse Tyson?

  And, he and his spouse co-founded the World Science Festival here in New York City. Every year, where science and art and music come together to celebrate science.

• 3:28Chuck Nice?

  Wow.

• 3:29Neil deGrasse Tyson?

  That's right. He does this.

• 3:30Chuck Nice?

  Thank you. Incredible.

• 3:31Neil deGrasse Tyson?

  He's not just some person who's sitting between us right now.

• 3:34Chuck Nice?

  Right.

• 3:34Neil deGrasse Tyson?

  This is Brian Greene.

• 3:35Chuck Nice?

  I mean, he is still that.

• 3:36Neil deGrasse Tyson?

  He's still.

• 3:39Neil deGrasse Tyson?

  I didn't wanna undo the fact.

• 3:41Chuck Nice?

  Yeah. Let's not demote him from personhood.

• 3:44Neil deGrasse Tyson?

  And, I think this is his fourth book.

• 3:47Chuck Nice?

  That's right.

• 3:48Neil deGrasse Tyson?

  Okay, and his first book that anyone knows about was a mega bestseller.

• 3:53Chuck Nice?

  Mm-hmm.

• 3:54Neil deGrasse Tyson?

  Which was?

• 3:55Chuck Nice?

  The Elegant Universe.

• 3:56Neil deGrasse Tyson?

  The Elegant Universe. And he's one of our leading string theorists, and this was a way to... Share not only the frontier of his research with all the rest of us, give us a sense of hope that maybe one day we'll understand everything.

• 4:08Chuck Nice?

  Cool.

• 4:08Neil deGrasse Tyson?

  Or not, or not. So, that was a mega bestseller, and we shared publishers back then. We had the same publisher.

• 4:14Chuck Nice?

  Oh, Norton?

• 4:15Neil deGrasse Tyson?

  WW Norton. Then he got so famous, he found another publisher. And then he published another book after that, it didn't do as well as the first book, okay? I just wanna, just hang some publisher.

• 4:26Chuck Nice?

  You're just giving your publisher some cred right now.

• 4:28Neil deGrasse Tyson?

  Dirty laundry out here.

• 4:29Chuck Nice?

  There you go.

• 4:29Neil deGrasse Tyson?

  Okay. Brian Greene, Alfred Knopf, publisher. Let's do this.

• 4:36Chuck Nice?

  Alright, here we go. As I said, we always start with a Patreon patron because they give us money. And, uh, this is Michael Tobias. He says, "Hello Neil and Brian. I often wonder how far we will journey through space within our lifetime. Will we be able to achieve interstellar travel, or will the human race go extinct before we have the opportunity and technology?" Now, he started off with "our lifetime," but I think he means "the lifetime of the species of human beings." Cause "our lifetime," the answer is "no." And I am no, not, not, not an astrophysicist at all.

• 5:11Neil deGrasse Tyson?

  Okay, well then we're done with that.

• 5:12Chuck Nice?

  No, but within the lifetime of the human species. First of all, what is the lifetime of the human species? What would that be?

• 5:17Neil deGrasse Tyson?

  A few million years.

• 5:18Chuck Nice?

  Few million?

• 5:19Brian Greene?

  Well, that's a guess, right?

• 5:20Neil deGrasse Tyson?

  Well, if you look at the-

• 5:21Brian Greene?

  If you look at the historical trend, yeah.

• 5:23Neil deGrasse Tyson?

  The life expectancy of mammal species.

• 5:25Chuck Nice?

  Yeah, right.

• 5:26Neil deGrasse Tyson?

  I think one in three million years, somewhere around that.

• 5:28Brian Greene?

  Yeah, but we're so much special, right? I mean, we have this thing on top of our head that enables us to figure things out. So, so either that is gonna be our own destruction, because we can build things that can kill ourselves, or we'll be able to figure out a way of living beyond the traditional lifetime of many species. So, unclear. But, um, if you take-

• 5:46Neil deGrasse Tyson?

  But let me add to that question.

• 5:47Brian Greene?

  Yeah.

• 5:48Neil deGrasse Tyson?

  There's what's possible in the laws of physics, and there's what's within reach with our engineering.

• 5:54Brian Greene?

  Absolutely.

• 5:54Neil deGrasse Tyson?

  So, give me your, your, your read on that.

• 5:57Brian Greene?

  Well, the laws of physics constrain any speed of any spacecraft traveling through space to be less than the speed of light. So, if you're not gonna play games with imagining that, we can actually warp the fabric of space and have warp drive-

• 6:08Neil deGrasse Tyson?

  Stop playing games, that's real.

• 6:08Brian Greene?

  Yeah, well, you know, it's unclear that we'll be able to- I'm able to achieve that.

• 6:12Neil deGrasse Tyson?

  It's real in every movie I've ever seen.

• 6:14Brian Greene?

  I agree, I agree. But, but, but taking the speed of a craft to be less than the speed of light, then I mean achieving a great space travel is challenging, right? Now, the weird thing is, because time slows down when you have a spacecraft or a clock of any sort that's in motion, you could have a spacecraft going out near the speed of light and we on Earth would watch its clock and its clock would be ticking off time so slowly that to the person on the ship, they would be able to go much further than we would think they would be able to if we didn't take that into account.

• 6:49Neil deGrasse Tyson?

  Right.

• 6:49Brian Greene?

  So, so, you know, we could send, you know, some Intrepid Voyager out into space and they could go.

• 6:55Neil deGrasse Tyson?

  Near the speed of light.

• 6:55Brian Greene?

  Near the speed of light and they could go arbitrarily far in their lifetime.

• 6:59Neil deGrasse Tyson?

  In their lifetime.

• 7:00Brian Greene?

  Yes, so.

• 7:01Neil deGrasse Tyson?

  Then they come back home and everyone would have forgotten about them because hundreds of thousands of years would have passed.

• 7:05Brian Greene?

  Or millions or billions of years, he was absolutely right.

• 7:08Neil deGrasse Tyson?

  Right, right. So that's not, that's not what people are imagining when they're thinking of space travel. No.

• 7:13Brian Greene?

  I mean, so. But, but it really matters, you know, if we were to take, you know, a group of our species and send them out into space, it really would be within their lifetime that they'd be able to, according to laws of physics, go arbitrarily far.

• 7:26Neil deGrasse Tyson?

  Right.

• 7:26Brian Greene?

  And so it's kind of, now you're right, the people back on Earth, they perhaps would be long extinct, you know?

• 7:32Neil deGrasse Tyson?

  Wow, imagine, you come back and your species isn't even around. Right, yeah. And the roaches took over and the rats. Right. And they say, wait a minute, wait, you come back and there's a museum that the rats have and there're the skeletons of humans there. Right. That long ago, it's terrorized the.

• 7:51Brian Greene?

  Or they could even have, you know, an homage, an exhibit to the spacecraft that left, you know, a hundred thousand or a million years ago and you can sort of see the, uh, the, the origin of your own trip.

• 8:03Chuck Nice?

  That's kinda cool, though. I mean, you could actually, so.

• 8:06Neil deGrasse Tyson?

  Okay, so you can, but no one else can really participate in that.

• 8:09Brian Greene?

  Unless you're part of the literal journey itself.

• 8:11Neil deGrasse Tyson?

  Right, right, good answer.

• 8:13Chuck Nice?

  So now, what about this, in terms of, when you say, you put these people on a ship, alright? So you take a colony of people, you put them on a ship, and now, you're, they, they go, and they're looking for someplace to live, and now you're just seeding the universe, you know? Uh, or at least a cer- another part of our galaxy, because you can't really say the universe, you know?

• 8:34Neil deGrasse Tyson?

  Milky Way.

• 8:34Chuck Nice?

  The Milky Way, you know, because we're not gonna, how long would it take us to get out of the Milky Way?

• 8:40Neil deGrasse Tyson?

  Millions of years to the nearest galaxy.

• 8:41Chuck Nice?

  Oh, there you go. So, but, with that-

• 8:44Neil deGrasse Tyson?

  Oh, sorry, sorry.

• 8:45Brian Greene?

  Well, it's hundreds of thousands, you know, hundreds of thousands of light years across.

• 8:48Neil deGrasse Tyson?

  Just get the numbers right. So, our galaxy is about a hundred thousand light years across. So if we watch you travel at the speed of light, we, it'll take us a hundred thousand years to observe that, but you could live an arbitrarily short amount of time, depending how fast you're going. So, that being said, you in principle could go to the Andromeda Galaxy, two million light years away.

• 9:07Chuck Nice?

  Right.

• 9:07Neil deGrasse Tyson?

  We are long dead here, maybe, and unless we're as smart as Brian wants to believe we are. Um, and so, yeah, so you could go another galaxy. But in practice, you wanna, you wanna pass by stars, not the void of empty intergalactic space.

• 9:23Chuck Nice?

  Exactly, right.

• 9:23Neil deGrasse Tyson?

  Right.

• 9:24Chuck Nice?

  Yeah, you wanna go someplace where there's, where there is something.

• 9:26Neil deGrasse Tyson?

  But Brian's point that I take to heart is, when I think of these ships, I think that they're generational ships, and they have to be really fertile people, make babies, babies grow up. But I, what was odd is, you will be giving birth to children who will never have known Earth.

• 9:42Chuck Nice?

  Yeah.

• 9:42Neil deGrasse Tyson?

  And that's, that's kinda diabolical to me, because they would not have had free choice to have taken that trip. Do you have any moral sense of it?

• 9:49Brian Greene?

  Well, you know, I don't think any of us have free choice or free will. So if you wanna get into that part of the conversation-

• 9:54Neil deGrasse Tyson?

  That's another thing.

• 9:57Chuck Nice?

  Okay, let's just pull out two of those worms from that can. Ow! Holy moly! Alright, we'll get back to that.

• 10:04Neil deGrasse Tyson?

  We got, I can't, I can't-

• 10:05Chuck Nice?

  Yeah, that's a big one right there.

• 10:07Neil deGrasse Tyson?

  I don't have a certain bandwidth.

• 10:08Chuck Nice?

  Okay. Alright, so let me ask you-

• 10:09Neil deGrasse Tyson?

  No, I'm just, I'm glad to be reminded. That you can send a colony of people. Right. And they can get anywhere they want in their lifetime. Yeah. Provided they travel fast enough. Yeah.

• 10:19Chuck Nice?

  So now let me ask you this. Uh, let's say they wanna, they're, they're gonna go someplace even further, right? We're talking about true interstellar travel, right?

• 10:28Neil deGrasse Tyson?

  Intergalactic.

• 10:29Chuck Nice?

  Intergalactic, um, it's, cause they're going to another galaxy, alright? And then they're coming back, okay? And they have kids and kids. What would that do? And maybe this is outside of your purview, I don't know. What would that do to us as a species? Would, would they be that much different from not having any of the effects of being on this spinning rock? Going around this little teeny star that we live in right now?

• 10:58Brian Greene?

  That's beyond my purview.

• 11:01Neil deGrasse Tyson?

  No, I would say that it is possible to speciate. One of the ways you make, you split a species is you strand a, a variety of yourself in a place and then there's no more communication. That's why every fricking animal looks so different on, in Australia, okay?

• 11:19Brian Greene?

  But you still need sufficient time during their isolated periods. And in this case, it could only be even a handful of generations, right?

• 11:26Chuck Nice?

  Right.

• 11:26Brian Greene?

  But, but there still would be generations, as you said, who would never have experienced life on planet Earth.

• 11:30Neil deGrasse Tyson?

  But you also need pressure to select against some features and promote others. So that those features then become something else that have, are not recognizable to where you came from.

• 11:41Brian Greene?

  Okay, I got you.

• 11:42Neil deGrasse Tyson?

  So you need that. And if, if that ship is exactly the environment that Earth.

• 11:47Brian Greene?

  Right.

• 11:47Chuck Nice?

  Like if you create one G and you do all this stuff.

• 11:50Neil deGrasse Tyson?

  Yeah, yeah.

• 11:50Chuck Nice?

  You're not really creating a circumstance where there's a pressure to.

• 11:54Neil deGrasse Tyson?

  A pressure.

• 11:54Brian Greene?

  But if you create a reality show where it's Survivor on the ship, right? And, and then you have artificial pressures, yeah, you could drive the species into some different places.

• 12:03Chuck Nice?

  That's kinda, that's kinda wild, that.

• 12:04Brian Greene?

  Yeah.

• 12:05Chuck Nice?

  Yeah. I think we just came up with.

• 12:06Neil deGrasse Tyson?

  It wouldn't be natural selection, it'd be artificial selection.

• 12:08Brian Greene?

  Yeah, that's right. You just inject them from the ship that they, uh.

• 12:12Chuck Nice?

  All right, we're gonna space you. All right.

• 12:14Neil deGrasse Tyson?

  Next question.

• 12:15Chuck Nice?

  Let's do the next question. All right, here we go. Uh, this is Cheyenne Leo, who is also from Patreon.

• 12:21Neil deGrasse Tyson?

  Cheyenne Leo, that's a nice name, I like that.

• 12:24Chuck Nice?

  Hello, Mr. Green. I hail from Canada, and I love your books. I've been wondering lately, what is time made of? It might be a little out there, but I was thinking that it must be made of something, because presumably, it was created in the Big Bang, and it interacts with things like light and gravity. Light takes time to get there, gravity slows it down in extreme circumstances, et cetera, et cetera. So, if it can interact with other forces, shouldn't it be made of something?

• 12:54Neil deGrasse Tyson?

  I love that question.

• 12:55Chuck Nice?

  It's a great question.

• 12:56Neil deGrasse Tyson?

  Yeah, when is something more than just an idea? When does it become a thing?

• 13:00Brian Greene?

  Well, this is an idea that is starting to become a thing right now. Uh, so, it's certainly the case that the intuition of the question is right on target. When we look at ordinary material objects in the real world, they are made of stuff. They're made of molecules, made of atoms, made of subatomic particles. Could that idea be relevant for space and time themselves? And people have thought about this for a long time, but recently, there have been developments in a variety of fields, string theory being one of them, where we're starting to catch a glimpse of what the ingredients of space and time might actually be. And in fact, there's work that's being done that shows that-

• 13:36Neil deGrasse Tyson?

  You're not talking about a time particle?

• 13:38Brian Greene?

  Not really a time particle per se, but it's easier to talk about this in space, even though space and time are really the same thing. But we have some evidence that space itself may be stitched by the threads of quantum entanglement. So this idea of quantum entanglement, that links together distant objects in a way that makes it appear as though they're right next to each other in terms of their physical properties. It may be that the threads of quantum entanglement are the stitches in the fabric of spacetime itself.

• 14:05Neil deGrasse Tyson?

  Is this where you get to the idea that in the distant future, where dark energy accelerates us ever greater?

• 14:13Neil deGrasse Tyson?

  That it might accelerate us faster than quantum phenomenon can keep up, creating a tear in the fabric of spacetime?

• 14:21Brian Greene?

  Yeah, and in fact, you don't even need to know about the ingredients in the fabric of spacetime to come to that conclusion.

• 14:26Neil deGrasse Tyson?

  You didn't pause when I said that. That means it could really happen.

• 14:29Brian Greene?

  Yes, so, so the idea that the dark energy might get stronger over time. So right now, we all know that there is dark energy pushing the distant galaxies away.

• 14:37Neil deGrasse Tyson?

  We all know.

• 14:38Brian Greene?

  Everyone, yeah, we've spoken about this before.

• 14:40Neil deGrasse Tyson?

  We actually have. We actually have spoken about this before.

• 14:43Brian Greene?

  Exactly, exactly, right. So, so, but it's possible that that dark energy gains strength over time, which means that it would not only drive the distant galaxies away ever more quickly, but it would start to drive even planets away from their stars. And it would even drive electrons away from the nucleus of atoms, which would rip matter apart. And yes, you're right, depending on the very nature of spacetime, it could be that this dark energy growing over time might sunder space itself, might rip the fabric of space apart.

• 15:11Chuck Nice?

  That's amazing. You're talking about the actual tearing of the universe itself. I don't even want to think about that.

• 15:16Brian Greene?

  Now, I should point out that since you brought up the tearing of the fabric of space, a paper that I wrote with a couple colleagues years ago was the first mathematical demonstration within string theory that the fabric of space can rip apart in a manner that would not yield a catastrophe. The fabric of space would repair itself and it would just be a new behavior within the repertoire of things that space can accomplish that Einstein would never have thought of. But Einstein didn't think about quantum mechanics and the general theory of relativity. And when you unite them, as string theory does, you get new things that space and time can do. And one of them may be tearing apart.

• 15:49Neil deGrasse Tyson?

  And it repairs itself.

• 15:50Brian Greene?

  And it repairs itself. It may not be as catastrophic as you think.

• 15:52Neil deGrasse Tyson?

  An ointment for that.

• 15:54Chuck Nice?

  We have a salve.

• 15:58Chuck Nice?

  Put some ice on it.

• 16:00Brian Greene?

  But actually, it's not so much a salve. The strings in string theory can surround the tear and form more of a Band-Aid. So it's more that the strings form a Band-Aid that protects us from the rip in the fabric of space.

• 16:12Neil deGrasse Tyson?

  But see-

• 16:12Brian Greene?

  And there's math behind this. It's not like a crazy guy.

• 16:14Neil deGrasse Tyson?

  I was gonna say, because that is-

• 16:15Brian Greene?

  You look very skeptical at this.

• 16:16Neil deGrasse Tyson?

  I did too, because that sounds eerily like- And just because there's math, don't hide behind this math behind it.

• 16:21Brian Greene?

  No, I'm not hiding, I'm just trying to let you know-

• 16:23Neil deGrasse Tyson?

  I'm just saying, math can talk about some crazy stuff that had nothing to do with reality, and you know it, don't tell me there's math behind it.

• 16:29Brian Greene?

  No, no, of course, of course. No, no, but this emerges right from the most natural interpretation of the equations of string theory. So I'm not standing on my head to make this happen.

• 16:36Neil deGrasse Tyson?

  Okay. No, that's an important point.

• 16:38Brian Greene?

  Yeah, it is.

• 16:39Neil deGrasse Tyson?

  Because there's a lot of stuff that we think about where you have to go out in left field to try to get the explanation, but if this flows out of your stuff naturally, it's a beautiful thing.

• 16:46Brian Greene?

  Yeah.

• 16:47Neil deGrasse Tyson?

  Very cool, man.

• 16:48Brian Greene?

  Can I tell you what else happens?

• 16:49Neil deGrasse Tyson?

  Oh, please.

• 16:50Brian Greene?

  Black holes shrink down to a very small size, very small mass, and they transmute into elementary particles. So, black holes that you normally think as being kind of this big thing out in the cosmos, different from the fundamental constituents of matter, when space rips, the process that repairs it involves black holes turning into particles.

• 17:10Neil deGrasse Tyson?

  See, now, he just made that up. Yeah, but, no. You had me until the universe repairs itself.

• 17:15Brian Greene?

  I don't make anything.

• 17:16Neil deGrasse Tyson?

  No, no, no. No, black holes are the doctors and the nurses. No, I'm sorry. No, you're full of shit now. Oh, man, oh. No, we gotta wrap this segment. Oh, we gotta wrap this segment? No, I'm sorry, we're taking too long to answer this question. No, no, we're not, this is great stuff. When we come back- Oh, I wish we were here every day, Brian. Oh, that was amazing. More Cosmic Queries until the end of time. Questions from the heart of the cosmos when we return.

• 18:14Neil deGrasse Tyson?

  We're back. Startalk.

• 18:19Neil deGrasse Tyson?

  Cosmic Queries. We've got Brian Greene here.

• 18:23Chuck Nice?

  Yes.

• 18:24Neil deGrasse Tyson?

  The one, the only, longtime friend, colleague. Love this man to death. He's been a friend of Startalk from the beginning. From the beginning.

• 18:31Chuck Nice?

  Absolutely.

• 18:32Neil deGrasse Tyson?

  This is not his first rodeo.

• 18:33Chuck Nice?

  No.

• 18:33Neil deGrasse Tyson?

  With us here. So Brian, congratulations on your fourth book.

• 18:36Chuck Nice?

  Thank you.

• 18:37Neil deGrasse Tyson?

  And got a great write-up in the New York Times. Very enthusiastic write-up. And even when he was criticizing it, he was praising it.

• 18:45Chuck Nice?

  Yeah, right.

• 18:47Neil deGrasse Tyson?

  It's like, "Oh, it got complicated, but it needed that, and I kinda liked it. And it got me into it." You know, it was like, one of those kinda things.

• 18:52Chuck Nice?

  So who actually reviews your books? I'm serious. Like, you two guys, you write these books. Who is it that sits down and says, "Okay, let me go through here and see..." Brian's mother. That's so funny.

• 19:08Neil deGrasse Tyson?

  Intermittent employee for the New York Times.

• 19:10Chuck Nice?

  Right. Son, I have to tell ya, I don't know about this whole thing about black holes and particles.

• 19:17Chuck Nice?

  So, no, really, who is it? I mean, I would say there's not a lot of people that can do that.

• 19:22Neil deGrasse Tyson?

  There's science editors.

• 19:23Chuck Nice?

  Oh, okay.

• 19:23Neil deGrasse Tyson?

  That's their job.

• 19:24Chuck Nice?

  Alright.

• 19:25Neil deGrasse Tyson?

  If they can't handle it, then they don't review. There are plenty of newspapers that don't review science books.

• 19:30Chuck Nice?

  Oh, actually, the number of reviews of science books is going down.

• 19:33Neil deGrasse Tyson?

  Oh.

• 19:34Chuck Nice?

  Because newspapers are really winnowing the staff.

• 19:36Neil deGrasse Tyson?

  Yeah, they're cutting their staff, so they can't afford it.

• 19:39Chuck Nice?

  Wow.

• 19:40Neil deGrasse Tyson?

  So this, just to give him credit, because he's in the club. Dennis Overbee, longtime science writer and editor.

• 19:48Chuck Nice?

  One of the best, really.

• 19:49Neil deGrasse Tyson?

  For the New York Times. And he leans cosmological?

• 19:53Neil deGrasse Tyson?

  Although when we demoted Pluto here,

• 19:55Chuck Nice?

  Mm-hmm.

• 19:55Neil deGrasse Tyson?

  He wanted to dip into that. When I said, "This is not your beat." You know, this is too nearby for you. But I think he wanted some Pluto street cred.

• 20:04Chuck Nice?

  Right.

• 20:04Neil deGrasse Tyson?

  So he did a little Pluto article on our demotion.

• 20:06Chuck Nice?

  And was he for or against your postulate?

• 20:10Neil deGrasse Tyson?

  He was antagonistic.

• 20:12Chuck Nice?

  Oh, okay.

• 20:13Neil deGrasse Tyson?

  Yeah.

• 20:14Chuck Nice?

  All right, got it.

• 20:14Neil deGrasse Tyson?

  But anyhow, he's a long time editor and he has a book of his own.

• 20:17Chuck Nice?

  Oh, yeah.

• 20:17Neil deGrasse Tyson?

  So the real meta question is,

• 20:19Chuck Nice?

  And so did you two actually review his book?

• 20:23Neil deGrasse Tyson?

  I think he wrote a book, The Lonely Hearts of the Cosmos.

• 20:25Chuck Nice?

  Lonely Hearts of the Cosmos.

• 20:26Neil deGrasse Tyson?

  Which was about two astronomers trying to find the scale of the universe? Was that the book I'm remembering?

• 20:32Chuck Nice?

  I don't remember the details.

• 20:33Neil deGrasse Tyson?

  Okay. But it was biographical.

• 20:35Chuck Nice?

  Okay.

• 20:36Neil deGrasse Tyson?

  Astronomers who had access to big telescopes.

• 20:39Chuck Nice?

  All right.

• 20:39Neil deGrasse Tyson?

  And you're there at night looking up at the night sky with the telescope. And nobody else, Lonely Hearts of the Cosmos.

• 20:45Chuck Nice?

  Oh, okay. That sounds about right. Okay, no, I'm joking. All right, here we go. Let's get back to our questions. Uh, this is, um, uh, CS21.

• 20:56Neil deGrasse Tyson?

  Hold it lower so people can see your beautiful face.

• 20:58Chuck Nice?

  Oh, I'm sorry. Here we go. CS21, I forgot we're on camera too. Um, "Hey, do you think the laws of physics are finite and knowable? Can we ever fully understand the universe in its entirety? If so, what forces might we be able to manipulate uh, that are beyond us now?"

• 21:16Neil deGrasse Tyson?

  Ooh.

• 21:17Chuck Nice?

  That's a very, very cool question.

• 21:19Brian Greene?

  No, it's a deep question.

• 21:20Chuck Nice?

  Yeah, it really is.

• 21:21Brian Greene?

  Because, look, you look around the world and there are intelligent beings walking around, dogs, right? And they don't, we think, understand the general theory of relativity or quantum mechanics. So these are intelligent brains. Although when I say that, I always think the dogs are out there barking and say, "Oh, he thinks you don't understand general relativity." You know, but seeing if that's really the case, then why do we think that the human brain would be able to understand it all? We may have limitations on the deep truths that we're able to grasp. Now, having said that, there's no evidence that there's any limit to what we can figure out. We haven't hit the wall, right? We did develop quantum mechanics. We did develop relativity.

• 21:55Neil deGrasse Tyson?

  Wait, wait, wait.

• 21:56Brian Greene?

  You know.

• 21:56Neil deGrasse Tyson?

  Wait, wait. You and your compatriots have been at this string theory thing for thirty years.

• 22:01Brian Greene?

  Yeah, here we go.

• 22:01Neil deGrasse Tyson?

  Maybe.

• 22:01Brian Greene?

  Here we go.

• 22:02Neil deGrasse Tyson?

  Maybe that's the wall.

• 22:04Brian Greene?

  It could be.

• 22:05Neil deGrasse Tyson?

  Maybe you guys aren't smart enough. You found the wall.

• 22:08Brian Greene?

  But, but here's what I would say to that.

• 22:10Neil deGrasse Tyson?

  Let me hold a mirror to you here, okay? Who's the one who can't find, who's at the edge of the wall?

• 22:13Brian Greene?

  See, but that would only be the case if we were sitting here saying we can't make any progress in understanding the mathematics of string theory. We're making incredible progress, but the thing is, and the part that you're responding to, which is completely justified, we haven't been able to make contact with observation or experiment. But that's not all that surprising when you're dealing with a theory whose energy scale is like ten to the fifteen, ten to the sixteen times greater than that of the Large Hadron Collider, most powerful machine in Geneva, Switzerland. So, I agree that we have hit roadblocks, but it's not us theorists, it's the experimenters.

• 22:47Neil deGrasse Tyson?

  Oh!

• 22:48Brian Greene?

  There you go. And if I might chime in here.

• 22:49Neil deGrasse Tyson?

  Smackdown!

• 22:50Brian Greene?

  If I might chime in here, let me just add.

• 22:57Neil deGrasse Tyson?

  That's the dog saying, "We have a solution, but you just..."

• 23:01Brian Greene?

  There's your answer, guys.

• 23:03Neil deGrasse Tyson?

  You're neutering us and you're taking us too. And you're feeding me Alpo.

• 23:10Brian Greene?

  Okay, cool, man. Oh, that's a great answer.

• 23:12Neil deGrasse Tyson?

  So...

• 23:12Brian Greene?

  It's a great answer.

• 23:13Neil deGrasse Tyson?

  Wait, wait. So, let me...

• 23:14Brian Greene?

  But go ahead.

• 23:14Neil deGrasse Tyson?

  Let me give a nuance to that question and hand it back to him.

• 23:17Brian Greene?

  All right.

• 23:17Neil deGrasse Tyson?

  Okay. Do you believe there may be missing laws of physics that'll help us get further? Or that kinda all the laws of physics are there, we just need to be more creative with what we've got?

• 23:28Brian Greene?

  Hmm. Yeah, I think it would be hubris.

• 23:30Neil deGrasse Tyson?

  That's a little bit of that.

• 23:31Brian Greene?

  Yeah, it is, it is.

• 23:32Neil deGrasse Tyson?

  It's a different tack.

• 23:33Brian Greene?

  Yeah, to think that we really have it right now would be sort of the classic act of hubris, right? I mean, every time we thought we figured it all out, there was a new law, there was a new particle, there was something else to find. So, I would imagine at sufficiently high energy scales, we're gonna find new stuff, new particles.

• 23:50Neil deGrasse Tyson?

  New energy scales would be beyond where anyone has gone before.

• 23:52Brian Greene?

  Yeah, so right now...

• 23:52Neil deGrasse Tyson?

  Bold, too boldly go.

• 23:53Brian Greene?

  Yeah, so let's say we've basically gone on the order of, uh, ten thousand times the mass of a proton, roughly speaking.

• 23:59Neil deGrasse Tyson?

  Energy.

• 24:00Brian Greene?

  Energy, energy scale. And we haven't found anything new yet. But I would imagine that between that scale and the so-called Planck scale, which is where the fundamental laws of quantum mechanics and gravity come together, that's ten to the nineteen times the mass of a proton. So, that's nineteen orders of magnitude bigger than a proton, and we've only gone up to sort of four orders of magnitude bigger than a proton. So, in that range, I suspect there's gonna be something new to be found.

• 24:27Neil deGrasse Tyson?

  Okay, cuz they cuz just in all fairness to those who've come before us, they would be on working in a tabletop, right? And there'd be some phenomenon they don't understand, and then they'd experiment with it, and then they isolate it and name it and characterize it and mathematize it.

• 24:42Brian Greene?

  Yes.

• 24:42Neil deGrasse Tyson?

  And so, our basic known four forces of nature come out of that kind of experiment.

• 24:47Brian Greene?

  Exactly.

• 24:48Neil deGrasse Tyson?

  Kind of tabletop plus simple particle accelerators, right?

• 24:52Brian Greene?

  And astronomical observations.

• 24:53Neil deGrasse Tyson?

  And observations. So what you're saying is, that's a regime that manifested some aspects of nature that we have figured out in a tidy way.

• 25:03Brian Greene?

  Yeah.

• 25:03Neil deGrasse Tyson?

  But there could be bigger questions we don't even get to yet, cuz we haven't tested the regime, and that regime is not on our tabletop.

• 25:10Brian Greene?

  Exactly.

• 25:10Neil deGrasse Tyson?

  Okay.

• 25:11Brian Greene?

  Yeah.

• 25:11Neil deGrasse Tyson?

  That means the future of physics is big, big money, big accelerators.

• 25:14Brian Greene?

  Uh, that is one way.

• 25:16Neil deGrasse Tyson?

  The lone candle burning.

• 25:18Brian Greene?

  It's that, but I also like to think that if we're sufficiently clever, we might find indirect ways of probing realms that you'd think would require that big machine, but maybe we can be smarter about it.

• 25:29Chuck Nice?

  Okay. On Star Trek, it's just all computer simulations, so.

• 25:33Neil deGrasse Tyson?

  By the way, just as a signal to my people being clever, it was how are you gonna put a big telescope in orbit? Well, you can't put a, make a rocket that wide, no, so you.

• 25:45Brian Greene?

  Build it.

• 25:46Chuck Nice?

  Let's build it.

• 25:46Neil deGrasse Tyson?

  Well, you can build it in space, or you can get a mirror that unfurls.

• 25:51Brian Greene?

  Right.

• 25:51Neil deGrasse Tyson?

  All of a sudden, the engineers say, hey, I got this.

• 25:53Brian Greene?

  Right.

• 25:54Neil deGrasse Tyson?

  Let me be clever and figure it out.

• 25:55Brian Greene?

  Yeah.

• 25:56Neil deGrasse Tyson?

  So we've actually overcome many challenges that previously were considered intractable just by clever people.

• 26:01Brian Greene?

  Yeah, exactly.

• 26:02Neil deGrasse Tyson?

  I'm echoing your point.

• 26:03Brian Greene?

  Yeah, yeah, exactly right.

• 26:04Chuck Nice?

  That is super cool, super cool, super cool. All right, here we go. Uh, this is Janesh, uh, from Instagram, says, "Finding slash creating your own meaning is fine, but objectively, what do you think, Brian, is the actual meaning of this creation?"

• 26:21Brian Greene?

  Yeah.

• 26:21Chuck Nice?

  Ooh.

• 26:22Brian Greene?

  Yeah, that, that.

• 26:23Neil deGrasse Tyson?

  Because meaning is, that's a big part of where you try to go in this book.

• 26:26Brian Greene?

  Yeah. And, and the answer that I give to that question, which I had to develop completely and more, you know, more fully, I should say, not completely in the book, is that there is no ultimate meaning floating out there in the void, right? Throughout these-

• 26:40Neil deGrasse Tyson?

  I gotta go through all these pages and to find out that there's no meaning?

• 26:42Brian Greene?

  Well, I'm gonna, I'm gonna give you the-

• 26:43Neil deGrasse Tyson?

  I gotta read this so you can tell me there's no meaning?

• 26:45Brian Greene?

  Cliff Notes, Cliff Notes, right here. So the Cliff Notes are that we are the product of the mindless, purposeless laws of physics. We are all just bags of particles governed by those ironclad mathematical-

• 26:56Neil deGrasse Tyson?

  Ecoplasmic-

• 26:57Brian Greene?

  That's it. And what we have the capacity to do, which is remarkable, is impose order, impose coherence, impose purpose and meaning on the external world and the internal conscious experience. And so, it's not as though they're two things. The real answer that's floating out there in the void awaiting our discovery and sort of the internal one that we manufacture, it is only the internal one that we manufacture because there is nothing else.

• 27:23Neil deGrasse Tyson?

  Well, how do you know this?

• 27:24Brian Greene?

  I don't know this beyond my experience in a lifetime of working with the laws of nature, the particles of nature, and trying to give explanations for the things that we observe in the external world.

• 27:34Neil deGrasse Tyson?

  So the particles are your gods?

• 27:36Brian Greene?

  Well, I, you know, there is a place for religion.

• 27:39Neil deGrasse Tyson?

  You need to answer that question way faster than that.

• 27:41Brian Greene?

  No, no.

• 27:42Neil deGrasse Tyson?

  Oh, well.

• 27:44Brian Greene?

  No, no, if you really wanna go there.

• 27:46Speaker 03

  Let me think about it.

• 27:47Brian Greene?

  No, no, no, no.

• 27:48Neil deGrasse Tyson?

  My altar has some neutrinos on it, but-

• 27:51Brian Greene?

  Yeah. No, no, but, but honestly, seriously, I do think there's a role for religion that some of our colleagues step on and dismiss out of hand entirely.

• 28:00Neil deGrasse Tyson?

  And what would that be?

• 28:01Brian Greene?

  Well, it's not to understand the external world. No one can use any religious doctrine to calculate the electron's magnetic moment to nine decimal places, which is what we can do routinely with quantum field theory. But if you think about religion and the spiritual journey is something that doesn't illuminate the external world, but rather the internal world of conscious experience-

• 28:20Neil deGrasse Tyson?

  Which many people go to it for meaning and life.

• 28:22Brian Greene?

  Yes, exactly. Then there is a role for it. And, and you don't judge it by whether it can explain the external world. That's not what it's meant to do. You judge it by whether it is a satisfying way of trying to understand your place in the universe.

• 28:36Neil deGrasse Tyson?

  Ninety percent of religious people would say that, the other ten percent anywhere fundamental is.

• 28:39Brian Greene?

  Yeah, of course, go different direction.

• 28:41Neil deGrasse Tyson?

  Get their science out of the Bible.

• 28:42Brian Greene?

  I agree, and that's problematic.

• 28:44Neil deGrasse Tyson?

  Enlightened religious people are where you're coming from.

• 28:47Brian Greene?

  Right, I agree.

• 28:47Neil deGrasse Tyson?

  That's very good.

• 28:48Brian Greene?

  That was a little journey, I liked it, man.

• 28:51Neil deGrasse Tyson?

  I still think he's got an altar in his home.

• 28:54Brian Greene?

  A neutrino altar?

• 28:55Neil deGrasse Tyson?

  I'm pretty sure. He sacrifices to the particle gods. I'm pretty sure, I'm pretty sure about that.

• 29:04Brian Greene?

  Alright, okay, let's move on to, uh, Lee Bird, okay? So, Lee Bird from Facebook says, "Hello, Dr. Tyson and Dr. Green. My wife has asked, where, where does our universe end? Not how, but where does our universe end? And I would like to say, are there more than one ending? Is there an ending and then more endings? Are there levels of endings?"

• 29:34Neil deGrasse Tyson?

  That's a time ending rather than a place ending.

• 29:35Brian Greene?

  Well, that's what I'm saying.

• 29:36Neil deGrasse Tyson?

  But is this a place ending, that's what I'm hearing?

• 29:37Brian Greene?

  That's a place.

• 29:38Neil deGrasse Tyson?

  You think it's a time ending? Where, where, it's a place. So, there's a place ending?

• 29:42Brian Greene?

  Yeah, so it's.

• 29:43Neil deGrasse Tyson?

  Where's the sign that says?

• 29:45Brian Greene?

  Says, "Stop, can't go any further."

• 29:47Neil deGrasse Tyson?

  Bridge is out.

• 29:48Brian Greene?

  And look, the quick answer is, we don't know. But the possibilities are, space could go on infinitely far, in which case there never would be an end. That's a strange idea to us beings that live in a finite environment, but nevertheless, the math allows that is a real possibility. Or, space could be curved, which means you could go out in that direction and ultimately circle back and return to your starting point. So, there again, wouldn't be an end, but nevertheless, the space would be finite in its extent. So, these are sort of two big possibilities people think about.

• 30:19Neil deGrasse Tyson?

  Travel an infinitely finite space? Yeah, infinite, yeah.

• 30:22Brian Greene?

  You could go infinitely far, but it would be a finite extent.

• 30:24Neil deGrasse Tyson?

  Like the surface of the earth.

• 30:26Brian Greene?

  Yeah, like the surface of the earth, exactly.

• 30:28Neil deGrasse Tyson?

  So, the answer is, you don't know?

• 30:31Brian Greene?

  Neither do you.

• 30:33Neil deGrasse Tyson?

  You didn't ask me, you're asserting, I don't know. You didn't ask me. I can tell you this.

• 30:39Brian Greene?

  Yes.

• 30:40Neil deGrasse Tyson?

  We look out to the edge of the observable universe.

• 30:42Brian Greene?

  Okay.

• 30:42Neil deGrasse Tyson?

  And we see light that has been traveling for 13.8 billion years.

• 30:46Brian Greene?

  Okay.

• 30:46Neil deGrasse Tyson?

  That. Gives us evidence of the Big Bang for that part of the universe experiencing it at the time it emitted that light. That horizon continues to push out.

• 31:01Chuck Nice?

  Right.

• 31:02Neil deGrasse Tyson?

  As long as we keep seeing evidence of the Big Bang, we are still moving into a universe that's our whole.

• 31:10Chuck Nice?

  Yep, right.

• 31:10Neil deGrasse Tyson?

  Imagine the day where that horizon washes over the last bit of matter that experienced the Big Bang. Then the information coming to us about the Big Bang ceases. And all of what we know of cosmology would have no data set at that point. And at that point, you're basically the moving horizon, which gets one light year away from us per year.

• 31:35Chuck Nice?

  Right.

• 31:35Neil deGrasse Tyson?

  At that speed, would have overtaken the last matter of the universe, and that would be the edge of the universe. Do you agree with that?

• 31:42Chuck Nice?

  Well, there's a, there's a version of that that I think I can agree with more precisely, which is...

• 31:48Neil deGrasse Tyson?

  I meant no, but...

• 31:49Chuck Nice?

  Yeah.

• 31:50Neil deGrasse Tyson?

  Cause he's a guest on my show. He's a guest, he's gotta be polite.

• 31:53Chuck Nice?

  Wait, by the way, I am taking notes. I gotta learn to talk to my wife like that. I have got to learn how to talk to her like this. It's just like, would you agree?

• 32:01Neil deGrasse Tyson?

  Well, there's a version that I would agree with more precisely, dear. Everything but the deer.

• 32:07Chuck Nice?

  Exactly.

• 32:08Neil deGrasse Tyson?

  He didn't say deer. Can I get a deer out of that, please?

• 32:10Chuck Nice?

  Throw the brother a deer, at least.

• 32:15Brian Greene?

  So, so even right now, with the accelerated expansion of space, we can do calculations that show us quite clearly that the distant galaxies that we have used to figure out that space is expanding, they are going to disappear over the cosmological horizon. We will not be able to see them in roughly a hundred billion or a trillion years.

• 32:33Chuck Nice?

  Okay.

• 32:33Brian Greene?

  So, the evidence that we've used to even figure out that space is expanding...

• 32:37Neil deGrasse Tyson?

  Is going away.

• 32:38Brian Greene?

  Is going away.

• 32:38Chuck Nice?

  Right.

• 32:39Neil deGrasse Tyson?

  What you're saying is the matter that is giving us this information will overtake the, the moving horizon.

• 32:46Chuck Nice?

  Yes.

• 32:47Neil deGrasse Tyson?

  And then, then it's a moot point.

• 32:48Brian Greene?

  Yeah, yeah. It'll basically drop over a cliff at the edge of space, which is the horizon, because it's moving away so quickly.

• 32:54Chuck Nice?

  You're outrunning your headlights.

• 32:55Brian Greene?

  Yeah.

• 32:55Chuck Nice?

  Ooh. That's what you're doing.

• 32:57Brian Greene?

  Yeah.

• 32:57Chuck Nice?

  Yeah, that's cool, man.

• 32:58Neil deGrasse Tyson?

  Yeah, okay, no, we gotta take a break.

• 32:59Chuck Nice?

  Oh, really?

• 33:00Neil deGrasse Tyson?

  I know.

• 33:00Chuck Nice?

  This is so good.

• 33:01Neil deGrasse Tyson?

  I know.

• 33:01Chuck Nice?

  I forgot we were doing a show.

• 33:04Neil deGrasse Tyson?

  I know.

• 33:07Neil deGrasse Tyson?

  Plus, I did still get my deer out of that.

• 33:11Neil deGrasse Tyson?

  Deer.

• 33:13Speaker 03

  That's a different marriage. That's a real marriage.

• 33:21Neil deGrasse Tyson?

  All right, StarTalk, Cosmic Queries, Brian Greene, Chuck Nice. We'll be right back.

• 33:39Chuck Nice?

  Hey, we'd like to give a Patreon shout out to the following Patreon patrons. Jamie Bonnely and Evan Blackburn. Thanks so much for helping us bring the cosmos down to earth. We couldn't do it without you. And for those of you who would like your very own Patreon shout out, go to patreon.com/stargtloradio and support us.

• 34:11Neil deGrasse Tyson?

  StarTalk, we're back. Cosmic Queries, Until the End of Time. Search for meaning in the universe. And Brian Greene goes there. He does. And how many pages, Brian?

• 34:24Chuck Nice?

  Oh, it's only 300. Lot of end notes. That's why it looks so thick.

• 34:27Neil deGrasse Tyson?

  Oh, there you go. There you go. That's a nice picture of you.

• 34:30Chuck Nice?

  Thank you.

• 34:31Neil deGrasse Tyson?

  Yeah, nice picture.

• 34:32Chuck Nice?

  Oh, wow. And it's recent and handsome.

• 34:34Neil deGrasse Tyson?

  Five minutes ago.

• 34:35Chuck Nice?

  Not like a Tinder picture. Like, wait a minute, this dude is 23.

• 34:41Neil deGrasse Tyson?

  So Chuck, give us the questions. This is our last segment. See how many we can squeeze in.

• 34:44Chuck Nice?

  Real quick, we'll get a quick. Let me just ask a quick question for myself. All right, we're able, this is hypothetical, because we're not able to, but we're able to get beyond this horizon that you were talking about. We're able to observe that there, whatever, right? But now we are outside of the universe that was created at the Big Bang. What is time in that place?

• 35:04Brian Greene?

  Well, it could be the same as time here. So, so that, that cosmological horizon is, as, as Neil was pointing out, just the distance that we can possibly see because light has had the time to travel from it to us since the Big Bang. But it could be that time applies throughout this realm of space and it could be that it looks out there much like it looks in here. It's not as though you pass through it and you've been in some entirely new domain. However, it's possible that it could be different. Since we've never been there, the math suggests that it will be the same. But were it different, that would be shocking and wonderful.

• 35:37Neil deGrasse Tyson?

  Wait, wait, but Brian, I, I may take issue with that.

• 35:38Brian Greene?

  Yeah, please.

• 35:39Neil deGrasse Tyson?

  Dear.

• 35:44Neil deGrasse Tyson?

  The horizon is not a real place.

• 35:46Brian Greene?

  Yeah.

• 35:46Neil deGrasse Tyson?

  It's just a property of where we are and the speed of light.

• 35:50Brian Greene?

  Yes. So when I'm a- That's what I meant.

• 35:52Neil deGrasse Tyson?

  Well, when I'm a ship at sea-

• 35:53Brian Greene?

  Yeah.

• 35:54Neil deGrasse Tyson?

  And I go to my horizon, whatever 10 miles away, now I have a new horizon-

• 35:59Brian Greene?

  You do.

• 35:59Neil deGrasse Tyson?

  And I'm still at sea.

• 36:00Brian Greene?

  You're still at sea. Exactly.

• 36:01Neil deGrasse Tyson?

  So why are you telling me something different is gonna happen?

• 36:03Brian Greene?

  No, that's my point. I believe that that will be the case in the universe. But it's also conceivable-

• 36:08Neil deGrasse Tyson?

  That is not what he said.

• 36:09Brian Greene?

  No, no, but it's conceivable. You would agree that when you take your ship, it's possible that when you reach your current horizon, it could be that things are completely different. It could be the dragons are there. It could, it could be the gates of hell.

• 36:20Neil deGrasse Tyson?

  There'd be dragons.

• 36:21Brian Greene?

  You've never been there.

• 36:21Neil deGrasse Tyson?

  Or you'd have to presume that at exactly that distance and you were in the middle of where all those dragons were and that's kinda-

• 36:28Brian Greene?

  It's a very special space.

• 36:29Neil deGrasse Tyson?

  That's a very special space.

• 36:30Brian Greene?

  Very special space. That was the point. So if I said it, yeah, so if I didn't say it clearly-

• 36:34Neil deGrasse Tyson?

  Right.

• 36:34Brian Greene?

  I suspect and the math strongly argues that it will be the same-

• 36:38Neil deGrasse Tyson?

  Right.

• 36:38Brian Greene?

  -out there.

• 36:39Neil deGrasse Tyson?

  Fine.

• 36:39Brian Greene?

  But it's conceivable-

• 36:40Neil deGrasse Tyson?

  It's conceivable that it would be different.

• 36:41Brian Greene?

  That it would be different, yeah.

• 36:42Neil deGrasse Tyson?

  But I get, what I really get out of that and maybe it just helped me out here. What you're saying then is what we are seeing is a reference. That's what we're seeing.

• 36:52Brian Greene?

  Yeah.

• 36:52Neil deGrasse Tyson?

  We're not really seeing an edge. We're not seeing, we're seeing a reference is what we're seeing. Any more than a ship at sea. That's not the edge of the earth. You can think it's the edge of the earth.

• 37:00Brian Greene?

  Gotcha.

• 37:00Neil deGrasse Tyson?

  And it might be the edge of the earth. It probably isn't.

• 37:03Brian Greene?

  However-

• 37:06Neil deGrasse Tyson?

  Oh, gave him too much time to think.

• 37:07Brian Greene?

  Yeah.

• 37:08Neil deGrasse Tyson?

  The brain going.

• 37:09Brian Greene?

  I should point out. I should point out that in a universe where the spatial expansion is accelerating, that cosmological horizon would actually have a temperature. You're right, it's not a real location in space, but from that spot, we would have heat emerging that would give a background temperature that at the moment would be about ten to the minus thirty Kelvin. So it actually has a physical presence, even though it is in some sense just a reference.

• 37:37Neil deGrasse Tyson?

  It's a thing to measure.

• 37:38Brian Greene?

  Oh, I love that.

• 37:39Neil deGrasse Tyson?

  A thing to measure.

• 37:40Brian Greene?

  That is awesome.

• 37:41Neil deGrasse Tyson?

  I love things to measure.

• 37:42Brian Greene?

  Moreover, can I point out, just since we're going on this tangent, that temperature that comes from that distant cosmological horizon may imperil the future of thought itself. Uh-oh. So one of the things I describe in the book is that in the far future, any-

• 37:57Neil deGrasse Tyson?

  That's where the book ends, the thought ends.

• 37:58Brian Greene?

  Yeah, it is.

• 37:59Neil deGrasse Tyson?

  I thought it was my limit.

• 38:00Brian Greene?

  It's close, it's the end of thought. It ends like this, "I'm cold." Never hears the idea. So any cogitating being, through the act of thought, has to release heat, right? Second law of thermodynamics. And if it's the case that that cogitating being can't release its heat, it will burn up. And because of the heat emitted by that distant cosmological horizon, in the far future, a cogitating being will not be able to release that heat, and if it thinks one more thought-

• 38:24Neil deGrasse Tyson?

  But that's not very much heat.

• 38:25Brian Greene?

  I know, but in the far future-

• 38:27Neil deGrasse Tyson?

  That's all you got.

• 38:28Brian Greene?

  That's all you got.

• 38:29Neil deGrasse Tyson?

  Oh, that's all you got.

• 38:30Brian Greene?

  Yeah.

• 38:31Neil deGrasse Tyson?

  So you're saying, "Oh, this is scary, don't tell me this."

• 38:34Brian Greene?

  Yeah.

• 38:35Neil deGrasse Tyson?

  "Oh, now I'm sad."

• 38:36Brian Greene?

  Yeah. Now you're gonna read the book.

• 38:38Neil deGrasse Tyson?

  No, okay, no. Now, let me, let me repeat what I think you said.

• 38:41Brian Greene?

  Yeah.

• 38:42Neil deGrasse Tyson?

  That every act of thinking is a thermodynamic electrochemical process, as far as we know.

• 38:48Brian Greene?

  Yeah.

• 38:49Neil deGrasse Tyson?

  Okay? So that creates heat that needs to dissipate so that you can have your next thought.

• 38:53Brian Greene?

  Yeah.

• 38:54Neil deGrasse Tyson?

  If the bath, the thermal bath in which you were immersed-

• 39:00Neil deGrasse Tyson?

  Has a greater temperature than the temperature of your thoughts. Then your thoughts will back up and overheat and you can't sustain that.

• 39:11Brian Greene?

  Yeah, that's the basic.

• 39:12Neil deGrasse Tyson?

  Like an overloading phaser.

• 39:13Brian Greene?

  Yeah.

• 39:14Neil deGrasse Tyson?

  Yes.

• 39:15Brian Greene?

  Yeah.

• 39:15Neil deGrasse Tyson?

  Very good.

• 39:16Brian Greene?

  But now it's the brain of the thinking being.

• 39:18Neil deGrasse Tyson?

  That's actually doing that.

• 39:19Brian Greene?

  So it tries to think and it explodes.

• 39:21Neil deGrasse Tyson?

  Self-destructs.

• 39:22Brian Greene?

  Wow.

• 39:23Chuck Nice?

  All right, let's get back to this. Okay, because we're short on time. Okay, all right.

• 39:27Neil deGrasse Tyson?

  All right, what do you got?

• 39:28Chuck Nice?

  All right, here we go. Um, this is Juan91 on Instagram, 91. He says, hi Neil and Brian.

• 39:35Neil deGrasse Tyson?

  He's not 911, it's just.

• 39:37Chuck Nice?

  It is 911.

• 39:38Neil deGrasse Tyson?

  It is?

• 39:39Chuck Nice?

  It is.

• 39:39Neil deGrasse Tyson?

  Okay.

• 39:40Brian Greene?

  That is good.

• 39:41Chuck Nice?

  You were absolutely right, it's 911. Uh, and he goes, hi Neil and Brian and maybe Chuck. Uh, my question is the following. Hypothetically, if we were living in a universe where we can increase or lower the entropy, would it be possible to travel in time? Greetings from Montreal, I really love the podcast and it makes my commute all the better.

• 40:00Neil deGrasse Tyson?

  So let me reshape that so more people can be part of that.

• 40:02Chuck Nice?

  I understand.

• 40:03Neil deGrasse Tyson?

  So, as you know, and as you've written, um, the increase of entropy is one of the arrows of time. So if we somehow had control over entropy in the universe to reverse it, will that imbue us with powers over the arrow of time?

• 40:17Brian Greene?

  I don't think so. So, you're right, we often do think about entropy and its relentless increase as an arrow of time. But if it were to reverse itself, time would still carry on in the direction that it was always traveling. We would just see some weird things happening in the environment around us. We might see, for instance, eggs unbreak or candles unburn. But it wouldn't be time going backward, it'd be those physical processes going backwards.

• 40:44Neil deGrasse Tyson?

  Oh, okay.

• 40:45Brian Greene?

  Now, if everything went backwards, that would be something else, but that's not what the question is. It's just we're able to reduce entropy in some reason.

• 40:52Neil deGrasse Tyson?

  Okay, so if we're able to reduce entropy of the universe, because we know we can do it locally, that's what life is.

• 40:58Brian Greene?

  Yeah.

• 40:58Neil deGrasse Tyson?

  Life is a, is, is, um...

• 41:03Neil deGrasse Tyson?

  Life is organized matter, so it has lower entropy than it would otherwise have if life did not form. We're getting, using energy from the sun.

• 41:10Brian Greene?

  Yep.

• 41:11Neil deGrasse Tyson?

  Basically to do this. So, uh, if you, we somehow did have power over entropy of the entire universe, do you think that would have any consequences at all?

• 41:18Brian Greene?

  Well, yeah, I mean, it would radically change our predictions for what will happen in the far future. You know?

• 41:25Neil deGrasse Tyson?

  Yeah, yeah, yeah. Things that we, our understanding of nature is so intermixed, intertwined with an increase in entropy.

• 41:34Brian Greene?

  Yeah.

• 41:34Neil deGrasse Tyson?

  That if entropy systemically decreased, we'd have to rethink what would, what was cause and what was effect.

• 41:40Brian Greene?

  That's right. And we'd have to rethink where we are headed in the far future.

• 41:43Neil deGrasse Tyson?

  Yeah, yeah, okay.

• 41:44Chuck Nice?

  Dude, that's really cool. Okay. All right, let's do this one.

• 41:47Brian Greene?

  And I have to rewrite one of the chapters of my book.

• 41:50Chuck Nice?

  Team Forsythe, uh, Team Forsythe Observatory on Instagram would like to know, hello Neil, Brian and Chuck, what do you all believe would be the world's religions' response when we are contacted from another civilization outside of our own existence?

• 42:11Neil deGrasse Tyson?

  Give it to me.

• 42:12Chuck Nice?

  There you go.

• 42:13Brian Greene?

  Yeah, I don't think it will make all that much of a difference. I think the, the nature of, uh, reality for us scientists would change completely because now we'd have a second instantiation of life out there in the universe, which would be a radical moment, but I think for the world's religions.

• 42:29Neil deGrasse Tyson?

  Intelligent life.

• 42:30Brian Greene?

  Yeah, even better, yeah. You know, but for the world's religions, I don't think that there'd be much of a difference because they have a certain perspective on where we've come from and why we're here and what we're doing. And I don't think that the existence of additional intelligent life would really change things in any substantial way.

• 42:47Chuck Nice?

  Oh, okay. Let me, let me, let me just put, let me do this for both of you. Here's the deal. That same thing.

• 42:53Brian Greene?

  Yeah.

• 42:53Chuck Nice?

  But now, here's the deal. Those beings tell us, we put you here. Now, what do the religions do?

• 43:03Neil deGrasse Tyson?

  Well, so there's already religion about that.

• 43:06Chuck Nice?

  What?

• 43:06Neil deGrasse Tyson?

  They're called the Ray Aliens. What? I'm just, I'm just saying.

• 43:11Brian Greene?

  Is this true?

• 43:11Neil deGrasse Tyson?

  Yes.

• 43:12Brian Greene?

  Is this?

• 43:12Neil deGrasse Tyson?

  Really? There are aliens. So, so this religion is a religion where God is not God as imagined in the, in the Hebrew Bible, but God is an intelligent race of aliens that created us.

• 43:27Brian Greene?

  Really?

• 43:28Neil deGrasse Tyson?

  And so, there's strong overlap with a God, because if a God created us, and they're the external thing.

• 43:33Brian Greene?

  There's a creator and a whole deal.

• 43:34Neil deGrasse Tyson?

  Right, so the, so alien, so there's a whole religion that's already there, is my point.

• 43:38Brian Greene?

  So they would just be like, "Told you."

• 43:40Neil deGrasse Tyson?

  Exactly. But, but to your point, there are some religions where, or some branches of religions where it's very important to them that the universe was created for us and for no other life. They would have an issue with this. But most religions have gotten past that. And religions are more than just belief systems, they're also institutions. And institutions generally have their own survival as a fundamental part of what they do and why they do it.

• 44:05Brian Greene?

  And, and moreover, there are so many religions already practiced on planet Earth, and each one needs to deal with the existence of the others.

• 44:12Neil deGrasse Tyson?

  The other religions.

• 44:13Brian Greene?

  The religions, and they're able to do that by virtue of saying, "Ours is the real one and theirs is not." So I think we'd have that same kind of response if aliens came down. But to your point about ray aliens, if that's the name of it, there's also the simulation hypothesis, right?

• 44:27Neil deGrasse Tyson?

  Oh, right.

• 44:27Brian Greene?

  If we are all just a simulation of future supercomputer, then again, there's a godlike being, the kid in the garage who's fired up the supercomputer, and again, you don't have anything supernatural, and yet we would be the outcome of a creator's desires, wishes, whims, because that kid fired up that simulation.

• 44:45Neil deGrasse Tyson?

  Hmm, okay. So he has another altar and is a kid.

• 44:50Neil deGrasse Tyson?

  The kid god as well as part of the god.

• 44:51Brian Greene?

  That's not those altar. Right, got you. All right, let's, um, let's see if we can get another one in. This is.

• 44:56Neil deGrasse Tyson?

  I think we can.

• 44:57Brian Greene?

  Oskat.

• 45:00Brian Greene?

  He says on from Twitter, "Since the beginning of our civilization, the human mind and consciousness have evolved so much. Can the human brain figure out the human consciousness? In what ways can we confidently predict that we will acquire the ability to comprehend the majesty of the cosmos?"

• 45:21Neil deGrasse Tyson?

  So, do you get into consciousness?

• 45:24Brian Greene?

  I do, yeah, there's a whole focus on it.

• 45:26Neil deGrasse Tyson?

  So, we gotta go quick. What's your take on it?

• 45:29Brian Greene?

  My take is that consciousness is an exquisite physical process, but nothing more than a physical process. It is simply particles coursing through a gloppy gray structure inside our heads, again, fully determined by physical law.

• 45:42Neil deGrasse Tyson?

  Do you think it was emergent?

• 45:43Brian Greene?

  And it's the organization. Yes, it certainly emerged by virtue of the organization of this structure inside of our heads. I don't think there's anything else beyond the particles and the laws of physics required for consciousness to exist. I mean, do you?

• 45:56Neil deGrasse Tyson?

  No, no, I'm not convinced by so much of what's written about consciousness. I mean, the fact that there's so many books on consciousness and everybody's talking about it, it means no one knows anything about it. The evidence you don't know anything is people keep writing about it, right? How many people are still writing about Einstein's general relativism?

• 46:09Brian Greene?

  Yeah, of course, yeah.

• 46:11Neil deGrasse Tyson?

  Right?

• 46:11Brian Greene?

  Yeah, so it is, but I agree. I think everyone would agree. It is the grand mystery, you know, where does consciousness come from? And many take the approach that we know historically people use with life. People thought vitalism. It couldn't just be particles and the laws of physics. You gotta inject something else, a life force. Nobody talks that way any longer, right?

• 46:31Neil deGrasse Tyson?

  Some Christians will talk about a soul.

• 46:32Brian Greene?

  Right, but few scientists think that way any longer. Similarly, there are some scientists who think you have to inject something into the particles and the forces to get conscious self-awareness. I think a hundred or a thousand or whatever number of years from now, people will look back and smile at how quaint that idea was, but there's nothing more than particles and physical laws.

• 46:50Neil deGrasse Tyson?

  What was the question about consciousness, though?

• 46:53Chuck Nice?

  Will we be able to understand consciousness? And then using that, be able to understand or comprehend the majesty of the cosmos?

• 47:02Neil deGrasse Tyson?

  So let me reshape that. So, is there a level of consciousness that awaits us? That will enable us to appreciate the cosmos even deeper than we already do?

• 47:12Brian Greene?

  Yeah, I certainly hope so.

• 47:13Neil deGrasse Tyson?

  What a level of awareness, I guess.

• 47:15Brian Greene?

  Yeah, you know, I think as we learn more about reality, we reshape our sense of who we are and what the grand mysteries of existence are. And I think that's a beautiful journey that we've been on for thousands of years, and it will carry onward.

• 47:28Neil deGrasse Tyson?

  Ooh, cool. Those are some final thoughts.

• 47:30Chuck Nice?

  Those are very good final thoughts.

• 47:32Neil deGrasse Tyson?

  Yeah. Brian, you don't come by often enough.

• 47:35Brian Greene?

  Invite me, I'll be here.

• 47:38Chuck Nice?

  Dear.

• 47:39Neil deGrasse Tyson?

  We have to invite him more often than the rate at which he writes books. That's the problem, okay?

• 47:45Brian Greene?

  There you go.

• 47:46Neil deGrasse Tyson?

  All right, Brian, always good to have you.

• 47:47Brian Greene?

  Thank you, sir.

• 47:48Neil deGrasse Tyson?

  Chuck? It's a pleasure. My boy. My man. All right, this has been Cosmic Queries. I'll just have to say it, the Brian Greene edition.

• 47:57Neil deGrasse Tyson?

  All right, Neil deGrasse Tyson here, your personal astrophysicist. As always, bidding you to keep looking up.