SPEAKER_1: Welcome to StarTalk, your place in the universe where science and pop culture collide.
SPEAKER_1: StarTalk begins right now.
SPEAKER_1: This is StarTalk, Cosmic Queries edition.
SPEAKER_1: Of course, I got Chuck Nice with me to make this happen, Chuck.
SPEAKER_2: What's up, Neil?
SPEAKER_1: All right, dude.
SPEAKER_1: You know, it's not often we get one of my own people in a Cosmic Queries.
SPEAKER_1: That's just my kindred spirit.
SPEAKER_1: And today, we've got Professor Hair Doctor Brian Cox across the pond from the UK.
SPEAKER_1: Brian, welcome to StarTalk, dude.
SPEAKER_1: Not your first rodeo with us.
SPEAKER_3: No, it isn't.
SPEAKER_3: No.
SPEAKER_3: We've been doing this for a few years now.
SPEAKER_3: I think it was about 10 years ago.
SPEAKER_1: Plus, I've been a guest on your show.
SPEAKER_1: A couple of times I've been in the UK.
SPEAKER_1: I was there live.
SPEAKER_1: You got an audience and stuff.
SPEAKER_1: So that was fun.
SPEAKER_1: And so, let me make sure I get your bio.
SPEAKER_1: So you're a professor of particle physics, University of Manchester.
SPEAKER_1: That sounds very specific.
SPEAKER_1: It's not just a professor of physics, right?
SPEAKER_1: Particle physics.
SPEAKER_3: I mean, my research history is I've worked at the particle accelerators around the world, actually, including Fermilab in Chicago, DAISY in Hamburg, and CERN in Geneva.
SPEAKER_1: Yeah, the big one, CERN.
SPEAKER_1: The big one.
SPEAKER_1: Yeah, good.
SPEAKER_1: And so, out of the UK, you've hosted multiple TV shows.
SPEAKER_1: The one I remember most is The Universe.
SPEAKER_1: And you also did one on the Solar System, correct?
SPEAKER_1: Correct me if I'm wrong.
SPEAKER_3: Yeah, the Solar System.
SPEAKER_1: And you got another one.
SPEAKER_2: That was the local version of that travel show.
SPEAKER_3: Yeah, this is the bit that we might be able to make it.
SPEAKER_2: The greater travel show was The Universe, and you were like, by the way, check out this neighborhood.
SPEAKER_3: Yeah, we're going to do multiverses, I think.
SPEAKER_1: And you got another one, Brian Cox's Adventures in Space and Time.
SPEAKER_1: And for me, what's most important is that you have come stateside, you have crossed the ocean to give a multi-city staged theater tour of the universe.
SPEAKER_1: This is bold, hairy, and audacious.
SPEAKER_1: I love it, I love it.
SPEAKER_1: And by the time this posts, you're in the middle of the tour.
SPEAKER_1: This feels like a little bit, because you got that Beatles haircut.
SPEAKER_1: It feels a little bit like the British invasion, you know?
SPEAKER_1: Coming across the, you know, putting us in a new place that we didn't even know we could land.
SPEAKER_2: Nothing wrong with that.
SPEAKER_1: Yeah, nothing wrong with that.
SPEAKER_1: Very cool.
SPEAKER_1: So Chuck, you collected questions from our Patreon supporters.
SPEAKER_2: Indeed, we do have them.
SPEAKER_2: And of course, you know, our listeners are very excited to ask Brian questions, so do you want to jump in?
SPEAKER_1: Yeah, let's go straight ahead.
SPEAKER_1: What do you have?
SPEAKER_2: Yeah, all right, here we go.
SPEAKER_1: And I'll just shut up this whole time because I got nothing to add.
SPEAKER_1: If there's a little thing I'll add, Brian, I'll add it.
SPEAKER_1: If I'm not, Brian missed something, I'll come in, but otherwise, I'm just going to shut up here.
SPEAKER_3: Well, we can take them together, can't we?
SPEAKER_3: Because, you know, the answers are the same.
SPEAKER_2: Don't worry, Brian.
SPEAKER_2: You ain't got to take that serious for a second.
SPEAKER_2: Or, you know, but listen, it's a testament, Neil.
SPEAKER_2: It's a testament, Neil.
SPEAKER_2: Neil is so excited about the universe that he cannot contain himself.
SPEAKER_2: And I, I admire that.
SPEAKER_2: When anything, which I cannot believe, as long as Neil has been an astrophysicist, that he still gets this reaction, when something is said, you see him go like this.
SPEAKER_1: Oh, oh, oh, oh.
SPEAKER_3: I know.
SPEAKER_2: I'm like, dude, seriously, how long have you been doing this?
SPEAKER_3: I know what you're saying.
SPEAKER_2: Yeah, okay.
SPEAKER_1: It's like the third grade kid in the front row who knows the answer, but the teacher's not picking on him?
SPEAKER_2: Exactly.
SPEAKER_2: Hey, listen, that's cool though, man.
SPEAKER_2: That's awesome.
SPEAKER_1: If we got to do a nerd fight, you know, I sharpen my nerd utensils here, so I'll be ready for you.
SPEAKER_1: Okay, Chuck, give it to us.
SPEAKER_2: All right, this is Marcus Gustafsson, Gustafsson, who says, Hello and greetings from Sweden.
SPEAKER_2: If the strength of gravity happened to be a little stronger or a little bit weaker than it is, how different would our universe be?
SPEAKER_2: Ooh.
SPEAKER_3: It's a good question.
SPEAKER_3: And this is widely debated, actually, because there's a question of how much you can change the fundamental properties of nature.
SPEAKER_3: So, do you say the strength of gravity, the mass of the electron, the way the Higgs field works, all those things, such that you have a radically different universe.
SPEAKER_3: And actually, it's quite hard because you can change some things and then change something else and it kind of balances the change out.
SPEAKER_3: And so it's quite a controversial area, actually.
SPEAKER_3: But broadly speaking, if gravity were too strong, all else being equal, then things would collapse ultimately into black holes very quickly.
SPEAKER_3: So the early universe would not have formed extended structures like galaxies and solar systems, or stars may be very short lived and so on.
SPEAKER_3: So you can change the universe such that you would not have life in the universe if you increase the strength of gravity too much.
SPEAKER_3: But also you can decrease it too much and then stars and galaxies don't form in the early universe.
SPEAKER_3: And again, you probably don't have a living universe.
SPEAKER_3: Now, the complication comes when you say, okay, well, what if in the early universe, the slightly over dense regions were a bit denser, which would have something to do with a theory we called inflation possibly, or something that, you know, the way the big bang was.
SPEAKER_3: And then you turn gravity down a bit, can you kind of compensate?
SPEAKER_3: And it's true, you can.
SPEAKER_3: So it becomes an extremely difficult modeling challenge.
SPEAKER_3: And so you'll see research papers on this.
SPEAKER_3: How can you change the things and fine tune things?
SPEAKER_3: But broadly speaking, that's what happens.
SPEAKER_3: If it is too strong, then everything collapses into black holes.
SPEAKER_3: And if it is too weak, nothing forms at all.
SPEAKER_1: OK, so that's the physicist answer.
SPEAKER_1: OK, now we'll give you the astrophysicist answer.
SPEAKER_1: OK.
SPEAKER_1: In graduate astrophysics 101, OK, one of the first calculations we do is what happens to the luminosity of a star if you change the gravitational constant?
SPEAKER_1: OK, it's a calculation we do, all right?
SPEAKER_1: So what you do is you put a little parameter there and see what happens to that parameter as you run through the calculations for a star's luminosity.
SPEAKER_1: And what you find is that the luminosity of a star is extremely sensitive to the value of Newton's gravitational constant, to the seventh power, OK?
SPEAKER_1: So what's interesting about that is if the gravitational constant were different, slightly higher, earlier in the universe than today, as Brian can attest, there are whole branches of physics that think about and wonder and worry about whether the constants have actually been constant, all right?
SPEAKER_1: Forget whether we have godlike powers to just change it and see what happens.
SPEAKER_1: Were they always this great?
SPEAKER_1: Did they change over time?
SPEAKER_1: So, you can look at what, how sensitive it is and constrain how much it could have possibly changed because you would see stars of enormous luminosities living out their lives very quickly in the early universe, and you don't see that.
SPEAKER_1: So, it's to the seventh power of that term that the luminosity would be affected.
SPEAKER_1: And seventh power is that times that times that times that times that, okay, all through.
SPEAKER_1: So, we actually find that number in intro astrophysics graduate school.
SPEAKER_2: And can you define luminosity for me?
SPEAKER_2: Because if you're saying that it's not just brightness.
SPEAKER_2: Oh, yeah, yeah, yeah.
SPEAKER_1: So, here it is.
SPEAKER_1: It's simple.
SPEAKER_1: This example is rapidly becoming obsolete, but take a hundred watt light bulb, okay?
SPEAKER_2: Yeah, well, yeah.
SPEAKER_1: Okay, what is that, right?
SPEAKER_1: Okay, in the old days, there was like these bulbs that got hot.
SPEAKER_2: Okay, now here's what you do first.
SPEAKER_2: You dial up your grandmother on a rotary phone.
SPEAKER_2: No.
SPEAKER_1: So, the wattage is its luminosity.
SPEAKER_1: So, no matter what distance I put it from you, it will always be a hundred watt bulb.
SPEAKER_2: Okay, gotcha.
SPEAKER_1: As I get it farther away, it gets dimmer and dimmer and dimmer, so that would be its brightness, that's all.
SPEAKER_2: Right, so that's it, so okay.
SPEAKER_2: So, you're saying that gravity is like a string on the light itself, kind of like, that would be making it less?
SPEAKER_1: No, no, it would be like a knob on it.
SPEAKER_2: Like a knob turning it down.
SPEAKER_2: Yeah, yeah.
SPEAKER_2: Thank you, right, so instead of pulling it back, it's turning down a lot.
SPEAKER_2: Okay, that's cool, man.
SPEAKER_1: Yeah, so it's a dimmer, or a thing on the bulb itself, yeah.
SPEAKER_2: Yeah, let's make the universe sexy, baby.
SPEAKER_2: Let's dim the lights, hey, you know.
SPEAKER_2: How would you like a little cosmic champagne?
SPEAKER_1: Next, time to go to the next question.
SPEAKER_2: Time to go to the next question.
SPEAKER_3: I'm enjoying this, I did that.
SPEAKER_2: You like the sexy universe, Brian?
SPEAKER_3: I'm gonna use some, I'm making notes.
SPEAKER_2: All right, let's go to Sandra Bayani.
SPEAKER_2: And Sandra says, is it possible that the laws of physics change beyond our cosmic horizon so that all of our theories about multiverses stop working and stop making sense?
SPEAKER_2: Greetings, fellow Earthling.
SPEAKER_2: I cannot get enough of this show.
SPEAKER_2: Please, whatever you do, never stop this podcast.
SPEAKER_1: Oh, Chuck, did you just add that?
SPEAKER_2: No, I didn't.
SPEAKER_2: I really didn't.
SPEAKER_1: I love that question, because it brings in our horizon in multiverses and the very theories that predict a multiverse work in our universe.
SPEAKER_1: Why should they work in another?
SPEAKER_1: We're going to take a break, and when we come back, we will get right to the heart of that question with our special guest today.
SPEAKER_1: He's a special guest to me, Brian Cox from over in the UK.
SPEAKER_1: We'll be right back.
SPEAKER_2: I'm Joel Cherico, and I make pottery.
SPEAKER_1: You can see my pottery on my website, cosmicmugs.com.
SPEAKER_1: Cosmic Mugs, art that lets you taste the universe every day.
SPEAKER_3: And I support StarTalk on Patreon.
SPEAKER_3: This is StarTalk with Neil deGrasse Tyson.
SPEAKER_1: We're back, StarTalk Cosmiquaries.
SPEAKER_1: This is everything physics, because I got one of my people here.
SPEAKER_1: One of my science and education brethren, Brian Cox from over in the UK, who they call him a rock star over there.
SPEAKER_1: And we've said this on his previous appearances, but it's worth repeating that this man had a number one song on the pop charts in the UK.
SPEAKER_1: So you are literal and figurative rock star of science.
SPEAKER_1: Am I, have I overstated that?
SPEAKER_3: No, I think you've understated it, if anything.
SPEAKER_1: So what was the name of the song again that you performed?
SPEAKER_3: The most famous song is a song called Things Can Only Get Better, which you will say correctly is again, runs a counter to the second law of thermodynamics and you'd be right.
SPEAKER_1: Oh yes.
SPEAKER_3: So it's an inaccurate song, but yeah.
SPEAKER_1: Yeah, sometimes you gotta break some eggs to make an omelet, you know, as they say.
SPEAKER_1: All right, let's keep going.
SPEAKER_1: So Chuck, we left off with a brilliant question about, here we are in our universe that has our own horizon and we come up with our own theories of the universe.
SPEAKER_1: And one of them is that there might be a multiverse.
SPEAKER_1: So beyond our horizon, if it's not in our universe, why should we even believe that the rules that predict a multiverse would even exist?
SPEAKER_3: Yeah.
SPEAKER_3: So our horizon, first of all, that there is a limit to how far we can see, which is the fact that our universe is of a finite age, or let's say there's been 13.8 billion years since the Big Bang.
SPEAKER_3: And so there's a finite distance you can see because light travels at a finite speed.
SPEAKER_3: So we are very sure that there are galaxies way beyond our horizon, but essentially the light has not had time to reach us from them.
SPEAKER_3: Now, actually, as Neil said in the answer to the last question, you can say, well, observationally, do we see any evidence of the laws of nature changing as we look out to the most distant galaxies?
SPEAKER_3: And the answer is no.
SPEAKER_3: We have no evidence that they change in the patch of the universe we can see.
SPEAKER_3: So that's the observational point.
SPEAKER_3: But when you start to talk about the laws of nature in different regions of the universe, our multiverse, as you said, then it becomes more interesting.
SPEAKER_3: One multiverse, there are lots of different kinds of multiverse, but one of them is called the inflationary multiverse.
SPEAKER_3: So we have a theory called eternal inflation, which essentially leads to the idea that there are perhaps an infinite number of bubble universes of which ours is one.
SPEAKER_3: And the piece that we can see, the observational, the little piece we can observe is a patch in one bubble universe amongst perhaps an infinite number of bubble universes in the inflationary multiverse.
SPEAKER_3: And those theories do lend themselves potentially to the laws of nature in each bubble possibly being different.
SPEAKER_3: And the way I sometimes picture it is like a snowstorm with snowflakes, so every snowflake is different because it's had a different formation history.
SPEAKER_3: But there's something similar about them all which goes to the underlying structure which is to do with the water molecule itself.
SPEAKER_3: So there's something similar, there's an underlying framework but every snowflake is different.
SPEAKER_3: And the inflationary multiverse can be like that.
SPEAKER_3: So you can imagine that the laws we see, things like the strength of gravity, sort of crystallize out as these bubble universes form from the potential which is this thing called inflation that's potentially going on all the time.
SPEAKER_3: So it's possible that different universes have different emergent laws, things like the strength of gravity.
SPEAKER_3: I think most physicists probably all expect that there'll be some kind of underlying framework which could be something that we don't know what it is, right?
SPEAKER_3: Something like string theory or something which underlies the whole thing.
SPEAKER_3: So that, maybe Neil wants to add.
SPEAKER_1: I love your snowflake analogy, but suppose that...
SPEAKER_1: Do you have enough latitude in your eternal inflation, inflationary multiverse model to have a universe that has five pointed snowflakes instead of six?
SPEAKER_1: I mean, how much room do you have to just make stuff up?
SPEAKER_3: We don't know.
SPEAKER_3: This goes back.
SPEAKER_3: It links to something called the string landscape, which Leonard Susskind actually wrote a great book called The Cosmic Landscape a while ago detailing this theory.
SPEAKER_3: So when you look at string theory...
SPEAKER_1: Just remind me, Leonard Susskind is the one who's a big exponent of the holographic universe.
SPEAKER_3: Yes.
SPEAKER_3: That's the same guy.
SPEAKER_3: He's been at the cutting edge of physics for decades, right?
SPEAKER_3: And so in the string landscape, the idea is that in string theory, it turns out you can have...
SPEAKER_3: There's a number that they calculate.
SPEAKER_3: I don't know how they do it actually, but it's something...
SPEAKER_3: Well, I do know how they do it.
SPEAKER_3: It's something to do with all the extra dimensions being curled up and stuff.
SPEAKER_3: It doesn't matter.
SPEAKER_3: But essentially 10 to the power 500 different possibilities.
SPEAKER_3: So one with 500 knots after it.
SPEAKER_3: These are the different ways that you can produce laws of physics like the ones we see from the underlying theory.
SPEAKER_3: And that was seen as a really disappointing...
SPEAKER_1: That's a lot of wiggle room right there.
SPEAKER_3: But the way I see it, it's almost like saying we understand DNA.
SPEAKER_3: So in biology, we have a theory, we have these things AC, T and G, the four different bases that come together to form DNA.
SPEAKER_3: And it's like saying, okay, so there's an underlying theory.
SPEAKER_3: It's pretty simple.
SPEAKER_3: It's the double helix, it's chemistry.
SPEAKER_3: Out of that, it's like saying, right, predict a human being.
SPEAKER_3: So of course, you can't, because there are many different combinations of DNA.
SPEAKER_3: And we have no understanding yet of which ones would work and which ones wouldn't and which ones can be realized by evolution and which ones can't.
SPEAKER_3: You know, it's just...
SPEAKER_1: It's an astronomical number of combinations of just to make humans, let alone all forms of life.
SPEAKER_3: So it's like saying we understand the basic chemistry that gives us that thing, DNA.
SPEAKER_3: But then from that, predicting a particular instance of that, an organism, is of course it depends on its history.
SPEAKER_3: It depends on all sorts of things.
SPEAKER_3: And it's the same...
SPEAKER_2: However, can you...
SPEAKER_2: If you look at that like, I don't know, an alphabet to create a language, can you rule out the nonsense?
SPEAKER_2: For instance, if you know English, you know that HLPPP5 is not a word.
SPEAKER_3: There's a grammar.
SPEAKER_2: So are you able to kind of rule out the nonsense that, okay, these things would not happen.
SPEAKER_2: And so even though it is a possible combination, we know that it's kind of gibberish.
SPEAKER_2: How do we narrow that?
SPEAKER_3: Well, I mean, we don't know.
SPEAKER_3: We haven't got the expertise.
SPEAKER_3: We don't really know what the underlying theory is.
SPEAKER_3: But I mean, for example, you could imagine a bubble universe that forms and gravity is so strong that it just collapses again in a millisecond.
SPEAKER_3: There may be many universes like that.
SPEAKER_3: So that might be, you know, as you say, that might be a universe that we consider was just never got going.
SPEAKER_1: So it's a gibberish universe.
SPEAKER_3: It might just about form and then collapse again, for example.
SPEAKER_2: Eric, you'll know if you meet a life form from there, because there's this like...
SPEAKER_1: So not only are the laws of physics gibberish, so is their language, right?
SPEAKER_3: I just want to emphasize, this is speculative stuff.
SPEAKER_3: So the string landscapes, I said, Linda Susskind's book is great on this.
SPEAKER_3: And then the link, though, it's interesting, the inflation, which Neil will know about as well, that's a theory that was introduced initially just to deal with something called the horizon problem.
SPEAKER_3: You mentioned the horizon.
SPEAKER_3: It's essentially the unexplained point that if you look out, look in one direction out into the universe as far as you can and then turn around and look in the other direction, then you're looking at points that emitted light that we're receiving now, that now in the universe is something like 93 billion, I think it is light years away, right?
SPEAKER_3: So you're looking at points that in the standard model of things could never have been in contact with each other.
SPEAKER_3: And yes, are at the same temperature, so one part in 100,000, which is an observation.
SPEAKER_3: So that means inflation was initially...
SPEAKER_1: Just a quick thing, Chuck, I think we did an explainer on this.
SPEAKER_1: There was something where I was talking about that the universe has a more uniform temperature than different parts of the same room you're in.
SPEAKER_2: Well, that's because with that explainer, we were talking about redshifting is kind of how we got into it.
SPEAKER_1: Oh, that's how we got there, because I was saying you have an air conditioner in a corner, you have a heater over there, and you're fine if it's a five-degree range in a room that's talking to itself thermodynamically.
SPEAKER_1: And now we have across the whole freaking universe, and it's within 100,000th of a degree, which is completely mind-boggling freaky, and we needed a freaky explanation.
SPEAKER_3: So inflation was the idea that once upon a time they were in contact, and then the universe expanded very, very fast for probably a small amount of time.
SPEAKER_3: And so we thought that they couldn't have been in contact with each other, but in fact they were.
SPEAKER_3: And so that's why inflation was introduced.
SPEAKER_3: But it ended up doing several things that it was not designed to do initially.
SPEAKER_3: One was that the thing that drives inflation, which has got a fancy name called Inflaton Field, but it doesn't matter.
SPEAKER_2: It's a breakdown in the supply chain.
SPEAKER_3: Inflation?
SPEAKER_3: Oh, it makes that trivial.
SPEAKER_3: The two points were doubling.
SPEAKER_3: If you take the two points in the universe, then the distance between them doubled every 10 to the minus 37 seconds in the basic models of inflation.
SPEAKER_3: So it's much worse than we're going through now with prices.
SPEAKER_3: It's an exponential expansion.
SPEAKER_1: Much worse is an understatement, just to be clear.
SPEAKER_3: But in looking at that, Stephen Hawking actually was involved in this.
SPEAKER_3: And many physicists in the 80s found that these theories...
SPEAKER_1: We're just saying, Chuck, Chuck, last time we did this, he said, Stephen was involved in this.
SPEAKER_2: I know, yeah, he's cleaning it up this time, Neil.
SPEAKER_1: He's been a little better.
SPEAKER_2: Even Hawking.
SPEAKER_1: We got to hear the last name here.
SPEAKER_1: This time.
SPEAKER_3: So that theory was discovered, predicted, that there would be ripples in the density of particles in the universe through the Big Bang, as inflation drew to a close, which are the ripples that we see in the cosmic microwave background radiation, which you may have talked about, and also actually in the distribution of galaxies across the sky.
SPEAKER_3: So there's a distribution.
SPEAKER_3: They're not just completely random across the sky.
SPEAKER_3: There are patterns in the galactic distribution.
SPEAKER_3: And that was predicted before it was observed by this theory.
SPEAKER_3: So the theory is interesting and textbook, but you'll find it in cosmology textbooks, but the eternal inflation bit, which is kind of an add-on to that, ends up with this idea that inflation doesn't stop everywhere at the same time basically.
SPEAKER_3: So you get multiple bubble universes.
SPEAKER_3: And then that theory was noticed that that's a mechanism to realize the string landscape, which gives you the possibility of varying the laws of nature in each of those bubbles.
SPEAKER_3: So that was the history.
SPEAKER_3: It sounds fantastical, but it's not just like somebody just dreamt it up one day and said this would be good.
SPEAKER_1: I try to make that clear, because otherwise they think we're just pulling stuff out of our ass.
SPEAKER_1: And it's, even if it is out of our ass, it's very carefully withdrawn.
SPEAKER_2: By the way, that's one of the universes.
SPEAKER_2: Ha ha ha ha.
SPEAKER_3: Ha ha ha ha.
SPEAKER_1: With a central black hole.
SPEAKER_1: Yes.
SPEAKER_1: Time to go to the next question.
SPEAKER_2: I love it.
SPEAKER_2: Okay, here we go.
SPEAKER_2: Hiddy Wegmans says this.
SPEAKER_2: Hello, Dr.
SPEAKER_2: Tyson, Dr.
SPEAKER_2: Cox, and Lord Nice.
SPEAKER_2: And I bet you can't pronounce my name correctly.
SPEAKER_2: You win that bet.
SPEAKER_2: Get no argument from me.
SPEAKER_1: And the name is what?
SPEAKER_2: I was asking.
SPEAKER_1: What's the name?
SPEAKER_2: It's H-I-D-D-E-W-A-A-G-E-M-A-N-S.
SPEAKER_2: I said Hiddy Wegmans.
SPEAKER_2: And he's from the Netherlands.
SPEAKER_1: Oh, that helps not to pronounce that.
SPEAKER_1: Hiddy Wegmans, maybe.
SPEAKER_2: Hiddy Wegmans, okay.
SPEAKER_2: And yes, if it's Dutch, it's...
SPEAKER_2: He says, I'm asking myself after I watch the movie, The Atom Project, if you really can time travel with wormholes.
SPEAKER_2: By the way, oh, here we go.
SPEAKER_2: Chuck Hiddy is pronounced Hidden without the N.
SPEAKER_2: Who knew?
SPEAKER_2: Hidday.
SPEAKER_1: Hidday.
SPEAKER_3: Wormholes.
SPEAKER_1: You've got to read to the end so you can help you pronounce it.
SPEAKER_2: Listen, that is too much work, Neil.
SPEAKER_1: So, Brian, we're talking about time travel and wormholes.
SPEAKER_1: I presume...
SPEAKER_1: I think everyone knows with Einstein relativity, you can travel into a future, all right, or at least into the future of where you once were.
SPEAKER_1: So let's confine this to can you go backwards in time?
SPEAKER_1: Do wormholes enable this at all?
SPEAKER_3: Wormholes are getting increasingly interesting, actually, particularly in the study of black holes.
SPEAKER_3: We can get on to that.
SPEAKER_3: So, yes, wormholes are allowed geometries in Einstein's theory of general relativity.
SPEAKER_3: If you just take that theory alone.
SPEAKER_3: What do I mean by that?
SPEAKER_3: So they really are shortcuts through space and time.
SPEAKER_3: So you can imagine, you know, traveling from New York to Sydney, it takes a long time.
SPEAKER_3: You go around the surface of the Earth or you could tunnel through and you could get there quicker.
SPEAKER_3: So, yes, if wormholes exist and you could travel through them and they were big enough and stable enough, then you can build a time machine.
SPEAKER_3: Now, virtually every physicist who works on this, and Kit Thorne, actually, who got Nobel Prize for Gravitational Waves, did quite a lot of interesting work on this.
SPEAKER_3: It looks like when you bring...
SPEAKER_1: And he was the main advisor in the movie.
SPEAKER_1: He was, yeah.
SPEAKER_1: He was, in fact, an executive producer.
SPEAKER_1: And the robot in that movie was named Kit.
SPEAKER_3: It was, and it has a wormhole.
SPEAKER_3: And he also actually suggested to Carl Sagan in contact that wormholes were used in the film.
SPEAKER_1: In the movie contact.
SPEAKER_3: In the novel.
SPEAKER_1: In the story.
SPEAKER_3: So when you add quantum mechanics into the mix, which is the theory of everything else, because our universe hasn't just got gravity in it, it's got all sorts of other things in it as well.
SPEAKER_3: Obviously atoms and electromagnetic radiation and so on.
SPEAKER_3: Then it seems like the wormholes are inherently unstable, the big ones.
SPEAKER_3: And if you try to travel through one, it collapses.
SPEAKER_3: And they were called Einstein, Rosen, Brinches before they were wormholes.
SPEAKER_3: And they're built in to the basic description of a black hole.
SPEAKER_3: If the black hole had lived forever, it's called the maximally extended Schwarzschild metric.
SPEAKER_3: Whatever it's called.
SPEAKER_3: But that which was discovered by Schwarzschild in 1916, just after the theory was published, then there's a wormhole in there.
SPEAKER_3: So they're just fundamental to the theory.
SPEAKER_3: But most physicists believe, and Stephen Hawking wrote a paper actually called the chronology protection conjecture.
SPEAKER_3: Conjecture.
SPEAKER_3: Where are your thoughts about this?
SPEAKER_3: I didn't know he was a rapper.
SPEAKER_3: I can even say it.
SPEAKER_3: I can't say it.
SPEAKER_3: Chronology protection conjecture.
SPEAKER_3: That these things would not be stable and you can't travel through them so you can't build time machines.
SPEAKER_3: However, it's worth saying that wormholes are becoming very, very fashionable now in what's called the ER equals EPR paradigm.
SPEAKER_3: So ER is Einstein-Rosen.
SPEAKER_3: This thing from the 1930s where Einstein and Rosen noticed that these geometries exist in space-time or can exist.
SPEAKER_3: EPR is Einstein, Podolsky and Rosen spooky action at a distance.
SPEAKER_3: It's quantum entanglement.
SPEAKER_3: And so what now is very fashionable and looks, it's one of the best explanations of how information gets out of a black hole, is that this plays a role.
SPEAKER_3: So there's kind of a dual description.
SPEAKER_3: So we've got quantum entanglement, which is this spooky action at a distance thing where you separate things to large distances and they're still linked in some way.
SPEAKER_3: The linked in some way is starting to look possibly like, you can describe that in terms of wormholes, microscopic wormholes linking them together.
SPEAKER_3: But this is really, this is stuff that's being done now, 2020, 2022.
SPEAKER_3: So it's on the edge, but people have taken it very seriously.
SPEAKER_1: Okay, so wait, let's pause there and come back.
SPEAKER_1: But all right, now you've established that we agree we can think about wormholes, but you haven't told us how to go backwards in time.
SPEAKER_1: When we come back, Brian Cox is going to tell you how to go back and not kill your parents, okay?
SPEAKER_2: And I can tell you in an even simpler way, if you really want to go backwards in time, get married and do something wrong, because she will never let you forget.
SPEAKER_1: Thank you, Chuck, for splitting your marital issues into this podcast.
SPEAKER_1: StarTalk will return with Brian Cox.
SPEAKER_1: We're going to find out how to go back in time.
SPEAKER_1: We're back, StarTalk, Cosmic Queries.
SPEAKER_1: Got Chuck, of course, and Brian Cox, my friend and colleague from the UK, is taking the United States by storm and a little bit of Canada in dozens of cities.
SPEAKER_1: He's bringing his major theatrical production of...
SPEAKER_1: Do you give it a title, or is it just everything you want to know about where we are in the universe?
SPEAKER_1: How about that?
SPEAKER_1: Is that the title?
SPEAKER_3: Horizons.
SPEAKER_1: Horizons, there it is.
SPEAKER_1: And Brian Cox, you can find his schedule in briancoxlive.co.uk.
SPEAKER_1: Just do a Google on Brian Cox Live, it'll send you there.
SPEAKER_1: And you can see the whole schedule.
SPEAKER_1: And he's coming through town with a hugely visually spectacular display.
SPEAKER_1: And this is what stages are for.
SPEAKER_1: If the universe is the biggest stage of them all, he's brought the universe into theaters.
SPEAKER_1: So Brian, welcome to town for this.
SPEAKER_1: So we left off with describing wormholes.
SPEAKER_1: And I have to tell the story.
SPEAKER_1: Brian, I have to tell this, okay?
SPEAKER_1: Chuck, Brian, you just stay on the side while I tell this to Chuck.
SPEAKER_1: So Chuck, I'm in London, and I'm a guest on Brian's show.
SPEAKER_1: And we're talking about space travel and space exploration.
SPEAKER_1: And he's got a whole audience there.
SPEAKER_1: They're all UK people, okay?
SPEAKER_1: And they're new to me, and I'm a little new to them, but they know Brian, and they know I'm American.
SPEAKER_1: So I talk about the future of space travel.
SPEAKER_1: And I say, maybe, you know, no, chemical rockets are not going to work.
SPEAKER_1: In order to do this, we need, like, warp drives or ideally wormholes, and then we can do this.
SPEAKER_1: And Brian kicks in and says, wormholes are unstable, and they'll collapse, and you can't do this.
SPEAKER_1: He's correct, but that's not the point.
SPEAKER_1: The point was, the audience, do you remember what the audience said?
SPEAKER_1: The audience said, that's why the Americans discover everything.
SPEAKER_1: Because they're so optimistic about everything.
SPEAKER_1: That's why they went to the moon, and we're stuck here in London.
SPEAKER_1: And so you lost your audience on that comment, Brian.
SPEAKER_3: It's true.
SPEAKER_1: And I had them from that comment.
SPEAKER_1: Because they liked my American...
SPEAKER_1: Some of it is just me, but then I realized a lot of it is just American enthusiasm.
SPEAKER_1: So Brian, how do you use wormholes to actually travel backwards in time?
SPEAKER_1: Is that possible?
SPEAKER_3: Well, so, yeah, if they were stable, or you could stabilize them in some way, then you could use them as time machines.
SPEAKER_3: And that's considered to be unlikely.
SPEAKER_3: But it really is true to say that we...
SPEAKER_3: Well, it's very true to say we don't have what's called a quantum theory of gravity.
SPEAKER_3: So we don't really, in any sense, understand the deep merger between relativity and quantum mechanics, which you need to understand to answer that question.
SPEAKER_3: And many physicists point out that we don't...
SPEAKER_3: It feels like it's no way to build the universe.
SPEAKER_3: I mean, we're all aware of back to the future.
SPEAKER_3: We've all seen back to the future.
SPEAKER_3: We all know the paradoxes that happen if time travel is a reality.
SPEAKER_3: So I think if you pushed most physicists and said, don't be formal about it and don't say what I just said, which is we don't understand quantum gravity yet, then most physicists would say, okay, we think the laws of nature will be such that there aren't stable macroscopic big wormholes.
SPEAKER_3: That's what I think most physicists would say.
SPEAKER_3: So you could have a universe which permitted time travel and was not full of contradictions if there were no free will at all.
SPEAKER_3: So the whole universe itself is completely consistent and the time travel is built into the consistency.
SPEAKER_3: And that's actually what you see in Interstellar.
SPEAKER_3: So that happens in the plot of Interstellar.
SPEAKER_3: He can't stop it.
SPEAKER_3: Spoilers, you know.
SPEAKER_3: He can't stop himself leaving his daughter's room in the past.
SPEAKER_1: And by the way, that's also what happened in the story Slaughterhouse-Five by Kurt Vonnegut, which is a time travel story on top of being a World War II story.
SPEAKER_1: And I think Kurt Vonnegut got it right.
SPEAKER_1: Correct me if I'm wrong, Brian.
SPEAKER_1: He just described your life is always there, you're always being born, you're always dying, you're always in school, you're always in love, and you just rejoin where you were on the timeline and relive that.
SPEAKER_3: Kip Thorne's birthday party, there's a proceeding.
SPEAKER_3: So, Neil, when we go to scientific conferences, you have a proceeding, so it's a big thing.
SPEAKER_3: And Stephen Hawking gave a talk, and it's written up in the proceedings of his birthday party because he's so eminent.
SPEAKER_3: And Stephen said that Kip has become increasingly interested in time travel through wormholes as he's got older.
SPEAKER_2: That's how he started.
SPEAKER_1: That's good.
SPEAKER_2: That's good.
SPEAKER_1: Chuck, this is our third of three segments.
SPEAKER_1: Give me a few, see if you can slip in a few more questions here.
SPEAKER_2: All right, here we go.
SPEAKER_2: This is Catherine Cellarini-Moore who says, Dr.
SPEAKER_2: Tyson, Dr.
SPEAKER_2: Cox, Lord Nice, hoping that you can hear Dr.
SPEAKER_2: Cox elaborate on he alluded to in his YouTube video regarding time and space not being the stuff from which everything else is derived, rather that time and space may be derivative of something much bigger, much deeper.
SPEAKER_3: This comes from the study of black holes primarily.
SPEAKER_3: And I would say it's fair to say the cutting edge as of now is that it looks like space and time emerge from quantum entanglements.
SPEAKER_3: So we mentioned entanglement before.
SPEAKER_3: I should say what it is by the way.
SPEAKER_3: Should I say what it is?
SPEAKER_3: Imagine you have a coin and you can toss it and it can come up heads and tails.
SPEAKER_3: If it was a quantum coin and there's two of them, they can be in what we call a state such that you could separate these coins out across the Milky Way to the edges of the universe.
SPEAKER_3: And you just look at one of them and you could toss it and it would be heads and tails.
SPEAKER_3: You can look at it and its heads, you look at it again, its tails 50% of the time looks completely normal.
SPEAKER_3: But actually, if you got back together after doing lots of experiments on this thing, you would find that the coins never came up heads at the same time or tails at the same time.
SPEAKER_3: They are always heads, tails plus tails, heads.
SPEAKER_3: Heads, tails or tails, heads, right?
SPEAKER_3: They're always opposite.
SPEAKER_3: So you can build a quantum state like that.
SPEAKER_3: That's called entanglement.
SPEAKER_3: So it's an interesting thing.
SPEAKER_3: It's like the information, all the information contained in this system of two coins is somehow spread between them and they don't behave as individual entities, even if you separate them to vast distances.
SPEAKER_1: So that's entanglement.
SPEAKER_1: Isn't that because they're not just coins, they're also waves and the waves know about each other outside of the local place where the coin is getting flown?
SPEAKER_1: If that's the truth, then I've been saying it wrong all these years.
SPEAKER_3: No, really, the best way to consider it is it's a single system.
SPEAKER_3: And the information, the structure of the system, it approximates the whole thing.
SPEAKER_1: Why isn't that the wave function?
SPEAKER_1: That's got to be the wave function.
SPEAKER_3: So you can write the wave function.
SPEAKER_1: Oh, that's what I'm trying to say.
SPEAKER_3: The wave function, you can write it down.
SPEAKER_3: It would be heads' tails plus tails' heads is an example of a wave function.
SPEAKER_3: And for the geeks there, we can have a 1 over root 2 there.
SPEAKER_3: In front of each one, everyone equal probabilities.
SPEAKER_1: You've gone too far, Brian.
SPEAKER_2: You had me at wave, you lost me at 1 over root whatever.
SPEAKER_3: Anyway, so that's an entangled system.
SPEAKER_1: Deep in there is that there is a term that's squared in the wave function.
SPEAKER_1: So you've got to put the square root of 2, so that when you square that, it becomes a half.
SPEAKER_3: Yeah, if I want the 50-50 thing.
SPEAKER_1: That was a missing piece of what he was saying there.
SPEAKER_3: It's the amplitude.
SPEAKER_3: So that's entanglement.
SPEAKER_3: It's a fundamentally quantum mechanical thing, and it's very well understood, and we use it in technology and quantum cryptography and so on.
SPEAKER_3: So it's a thing.
SPEAKER_3: This is how the universe works.
SPEAKER_3: And it does seem as if, as I mentioned before, the idea that you can also interpret that as having wormholes connecting these things together.
SPEAKER_3: Essentially what you're seeing is that entanglement and space are intimately related.
SPEAKER_3: That's the modern way of looking at this, the very modern way.
SPEAKER_3: And I think it's fair to say that most physicists would say that the entanglement is the fundamental thing.
SPEAKER_3: And so we're beginning to think now that you have a theory of quantum mechanics, quantum field theories on some surface or something.
SPEAKER_3: And then the entanglement actually produces the space.
SPEAKER_3: I mean, it's true to say that entanglement, I've seen it said, which is a beautiful thing to say, that entanglement is sort of the glue that keeps space together.
SPEAKER_3: And so entanglement is fundamentally related to space and time, but it's more obscure how it relates.
SPEAKER_1: So that's the next sci-fi frontier because the latest Dr.
SPEAKER_1: Strange is Madness Through the Multiverse or something.
SPEAKER_1: So they got the multiverse in there and he's opening up portals, which are basically wormholes, as he jiggles his hand.
SPEAKER_1: So now we got to somehow get down into the very fabric of the space and time itself.
SPEAKER_1: That would be good.
SPEAKER_1: All right.
SPEAKER_1: Chuck, we got just a couple minutes.
SPEAKER_1: See if we can go into like lightning mode, lightning round.
SPEAKER_2: Okay, if we can.
SPEAKER_2: Let's lighten things up here with Lindahl Fries who says, Dr.
SPEAKER_2: Tyson, Dr.
SPEAKER_2: Cox, Chuck, here is, is there a parameter edge of the universe?
SPEAKER_2: And where in relation to that edge is the Earth or the Milky Way located?
SPEAKER_2: Are we closer or farther to the center of the universe?
SPEAKER_2: Also, how do we know the universe is expanding?
SPEAKER_2: And is it just that our instruments are getting stronger?
SPEAKER_1: Okay, so we need that at a sound bite.
SPEAKER_3: So no, we're not at the center of the universe.
SPEAKER_3: We're at the center of the observable universe, because that's just a piece that we can see.
SPEAKER_3: But the universe extends way beyond that horizon.
SPEAKER_3: And so it could be infinite in extent, but we don't know.
SPEAKER_3: But it's much bigger, I think, than the piece we can see.
SPEAKER_3: So no, we're not at the center of the universe.
SPEAKER_3: It might be an infinite universe.
SPEAKER_3: We know it's expanding just very simply because we look at light from distant objects and that light is stretched.
SPEAKER_3: And the explanation is that light is a wave and it's traveling through expanding space.
SPEAKER_3: And so it gets stretched as it journeys.
SPEAKER_3: And the basic observation, all the way back to Hubble, is that the further away you see...
SPEAKER_1: Hubble, the person, the person.
SPEAKER_3: The further away the thing is, the more the light is stretched when it reaches us.
SPEAKER_3: And that's what you would expect if space were expanding.
SPEAKER_3: Essentially a uniform race.
SPEAKER_3: It's actually changing a bit.
SPEAKER_3: It's expanding a bit faster now.
SPEAKER_1: Okay, so there is no...
SPEAKER_1: So if we went...
SPEAKER_1: If we said, I want to go to my horizon, Chuck, let's leave tomorrow.
SPEAKER_1: So what would we see?
SPEAKER_3: You'd see the same universe as far as we know.
SPEAKER_3: So you could go to the horizon and look around, and you'd see a completely uniform universe with the same kind of distribution of galaxies.
SPEAKER_1: So it's like a ship at sea is carrying its horizon with it.
SPEAKER_3: Yes, that's a good example.
SPEAKER_3: If you go to the horizon on your boat and go to the horizon 20 miles away, whatever it is, and then I probably got that number wrong, and now all the flat earth people are going, see, you didn't know.
SPEAKER_3: But there is a horizon, whatever it is.
SPEAKER_1: It's way closer than 20 miles unless you're in a crow's nest.
SPEAKER_3: So you go to the horizon and you just see the ocean, and you go to the next horizon and you just see the ocean, and that's what the universe is like as far as we can tell.
SPEAKER_1: Minus the fish.
SPEAKER_2: I mean, that's as simple as going to the top of a hill.
SPEAKER_2: You experience that anytime.
SPEAKER_2: Like you're driving up a hill or on a bike.
SPEAKER_2: You look at the top of the hill and it just looks like that's the end.
SPEAKER_2: You get at the top of the hill and it's just more of the same.
SPEAKER_2: It's just this time you're looking down.
SPEAKER_2: That's cool.
SPEAKER_2: All right.
SPEAKER_2: Let's go to Alain Bredot.
SPEAKER_1: This might be the last question we have time for.
SPEAKER_1: Okay, go.
SPEAKER_2: Alain says this.
SPEAKER_2: Hey, Neil, Chuck and Professor Cox.
SPEAKER_2: We have electron microscopes to probe smaller stuff than with regular light microscopes.
SPEAKER_2: Do you think somebody is going to come up with a quark microscope or something of that nature that will enable us to see even smaller or get closer to those strings?
SPEAKER_1: Ooh, I love it.
SPEAKER_2: That theorist fantasized.
SPEAKER_2: Wow, Alain.
SPEAKER_1: Let me just set that up just real quick.
SPEAKER_1: Regular microscopes use visible light, and visible light has certain wavelengths.
SPEAKER_1: If you really think about it, a visible light telescope can't see anything smaller than the wavelength of light you're using because the light would just wash over it and wouldn't be able to bring it into focus.
SPEAKER_1: So electron microscopes use basically, I think, Brian, is it x-rays?
SPEAKER_1: Because electrons and x-rays are the same thing at certain, you can beam electrons to have an energy level of that of an x-ray, and x-rays have really small wavelengths.
SPEAKER_1: So now you can see detail way smaller than visible light.
SPEAKER_1: So this questioner knows this about electron microscopes and wants to take it another step.
SPEAKER_3: And there's a really great fundamental point to make here which goes to black hole physics actually again.
SPEAKER_3: So as you take the wavelength down, quantum mechanics allows you to think of light as a wave or as a stream of particles called photons.
SPEAKER_3: And as you shrink the wavelength, the energy of the photon goes up.
SPEAKER_3: So that's just basic quantum mechanics.
SPEAKER_3: So the smaller the wavelength, the higher the energy.
SPEAKER_3: So you get to a point where if you want to probe smaller and smaller distances, what actually happens is you make a black hole.
SPEAKER_3: Because you put so much energy into a small piece of space that a black hole forms.
SPEAKER_3: And then as you put more energy in, the black hole grows.
SPEAKER_3: And so you end up reversing that process.
SPEAKER_3: Because as the black hole grows, then you get less and less resolution again.
SPEAKER_3: So there's a limit to how small you can see.
SPEAKER_1: So I'll step in here because Chuck didn't.
SPEAKER_1: You kept talking after you said, yeah, first you make the black hole and then you continue.
SPEAKER_3: So you put more and more energy in.
SPEAKER_1: I'm saying this sounds dangerous.
SPEAKER_3: It's an in principle argument.
SPEAKER_1: In principle?
SPEAKER_1: Oh, it's a thought experiment.
SPEAKER_3: The point is that you get to a point where if you try to cram more and more energy into a smaller and smaller amount of space, which you have to do to see the small thing, you have to get more energy in, the smaller wavelength.
SPEAKER_1: Because you're using photons that are higher and higher energy.
SPEAKER_3: Yes, or anything, electrons or whatever it is.
SPEAKER_3: Then there comes a point where you form a black hole in that region.
SPEAKER_2: And then you can't see anything because your microscope got sucked in.
SPEAKER_1: Because you dazed.
SPEAKER_3: You'll have less resolution.
SPEAKER_3: Now, Leonard Suskin writes about it.
SPEAKER_1: So ignoring the complication that you'd be dead, ignoring the complication that you'd be dead and you'd destroy the Earth, you'd have less resolution on the microscope.
SPEAKER_3: Because if you had a tiny black hole, you wouldn't notice it except you'd stop seeing.
SPEAKER_3: So you can't probe smaller and smaller distances forever.
SPEAKER_3: I think Suskin calls it the UVIR connection, ultraviolet infrared connection.
SPEAKER_3: I think that's what he calls it.
SPEAKER_3: But it's a fundamental property of the universe.
SPEAKER_3: So black holes stop you from doing that, going to smaller and smaller and smaller and smaller distances.
SPEAKER_1: Those pesky black holes.
SPEAKER_3: Again, it's fundamental.
SPEAKER_3: It's pointing to fundamental physics.
SPEAKER_3: So we go all the way back to this idea of space and time and the link to quantum.
SPEAKER_1: Dude, we've got to wrap it up there.
SPEAKER_1: Oh my gosh.
SPEAKER_1: Did we cover the universe here?
SPEAKER_1: Whoa.
SPEAKER_1: I know you're active on Twitter.
SPEAKER_1: Where else are you active?
SPEAKER_1: Because you're Prof Brian Cox on Twitter.
SPEAKER_1: Where else are you?
SPEAKER_3: I'm on Facebook as well.
SPEAKER_3: Twitter is my usual mode of communication.
SPEAKER_3: I don't know why.
SPEAKER_1: Yeah, it's a habit.
SPEAKER_1: It's quick and easy and sharp.
SPEAKER_1: And so it's been a delight to have you on this Cosmic Queries, on his British invasion of North America.
SPEAKER_1: The Brian is coming.
SPEAKER_2: The Brian is coming.
SPEAKER_1: The Brian is coming.
SPEAKER_1: Bringing his Horizons Tour through multiple cities.
SPEAKER_1: Check it out.
SPEAKER_1: briancoxlive.co.uk.
SPEAKER_1: Brian, always great to see you and hear from you.
SPEAKER_1: And we'll connect again.
SPEAKER_1: Chuck, love you, man.
SPEAKER_2: Love you, too.
SPEAKER_1: Alright, Neil deGrasse Tyson here, your personal astrophysicist.
SPEAKER_1: As always, keep working out.