StarTalk Radio - Cosmic Queries – A Ripple in Spacetime with Charles Liu

Episode Date: January 26, 2024

What if time had multiple dimensions? Neil deGrasse Tyson and co-hosts Chuck Nice and Gary O’Reilly answer grab-bag questions about Hawking Radiation, the speed of light, and how rare black holes are with astrophysicist Charles Liu. NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here: https://startalkmedia.com/show/cosmic-queries-a-ripple-in-spacetime-with-charles-liu/Thanks to our Patrons Mapplicable, Sam J, Karen Goodger, Bean Mon, Brittany Mencotti, Jeremy Davidson, and Brian Giordano for supporting us this week. Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

Coming up on StarTalk Special Edition, we're going to do a version of Cosmic Queries, but with the help of Charles Liu, everyone's geek-in-chief. And one of the questions posed is, who does he call when he doesn't have an answer? You'll learn that and more coming up on StarTalk. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk Special Edition. Neil deGrasse Tyson here, your personal astrophysicist.

And as usual for Special Editions, we've got Gary O'Reilly. Gary. Hey, Neil. If you didn't know, former soccer pro, football pro, I guess they say that over in the UK. A big turned announcer because he's retired. And we get to use a bit of him for our talk. So thank you, dude. And recently married. Yes. Congratulations. Happily married. Who knew it would last this long? What, six months? Not even that. Congratulations.

The first six months of marriage. Thank you. Nice. Chuckie baby. Hey, what's happening, Neil? I feel bad because we're checking in with you. You're doing a comedy stint in Aruba. That's right.

Right now. Right now. You're on this instead of being on the beach, so we'll try to make this quick for you. I was on the beach and left the beach. Don't rub it in. Let me step into this. Don't you have to make a thing out of it?

Literally, I was in the Caribbean, swimming around just 20 minutes ago. Okay. Came up here and said, okay, let me get back to the room and set up and do this. So what we're going to do is we're going to have kind of a Cosmic Queries, but like a special edition edition of Cosmic Queries. And whenever we're in kind of gram bag mode, I need some help. And you know who we go to for that, of course. Charles Liu.

Charles, welcome back. Hey, Gary. Hi, Liu. Charles, welcome back. Hey, Gary. Hi, Gary. Hey, Chuck. Great to see you all. I was not on the beach just now. You're not on the beach. I'm perfectly happy to be here with you all.

Hey, Chuck. We're, of course, all enviants. Gary, you brought in the questions. And you curated the questions. Yeah. You told me we had more than 100 questions on this solicitation. Yeah. And apologies up front for those questions we couldn't get to. We're only going to get about an hour's worth of this show,

so we had to flash through. They're all from our Patreon patrons, so thank you so much for your curiosity. Let's start with Gina Martin, shall we? Mm-hmm. Since time, as we know, moves in a straight line, can we consider time being one-dimensional from our perspective? That being said, what would it look like if time had three dimensions just like space?

And is that even possible? Whoa. I'm glad you're here, Charles. We'll start with an easy one, right? Yeah. The reality is that we can indeed thank you for your question uh think of time as a dimension in fact uh the rolling stones saying this all about that time is a dimension right uh but yes the general relativistic

assessment of space time is is... Einstein general relativity. Yes, Einstein general relativity describes space and time as three dimensions of space, one dimension of time. Now, there have been some work over the years, theoretically. What if there were more than one dimension of time? And what happens is complicated, as you might imagine. But the most significant... Okay, so that's the answer. It's complicated.

Next question. Yes. Well, the simplest, well, the most significant effect we would have in our lives is on cause out. Right? Neil, as you know, we think of time passing as stuff in the past affecting what happens in the present and the future, but not the other way around. If you have three dimensions of time and you can travel both forward and backward, also left and right and up and down in time, then you don't know what the past is by definition.

You have to change your concept of what causes what, because you can be dancing back and forth in a different dimension and something that you thought was in the past might actually loop around in a say, grand view and wind up in our future. When you say grand view, you mean a view from outside of those three dimensions? Yes, that's right.

That's right. You'd have to be above. You'd have to be above and beyond that whole set of coordinate system. Right. String theory, you've seen that happen all the time too. But imagine kicking a football, right, a second ago, but actually having kicked that football a second ago in one dimension of time,

but kicking the football five seconds from now in a second dimension of time and kicking it at the precise moment now in the third dimension of time. Wait, wait, wait. Is there a dimension where you don't kick the football? Not in this configuration. That's called the Charlie Brown dimension. I forgot about that dimension. Yeah, that's the Charlie Brown dimension. Is it just humans that see time as a straight line? Other beings in other galaxies are perceiving in a very different manner. Great question.

At the moment, since we haven't found other beings in other dimensions or other parts of the universe, we don't know what their brains are structured on. But the universe as a whole has a causality too. In other words, all of the universe as we conceive of it in Einstein's space only has one dimension of time. If there are other dimensions of time that we somehow can't perceive but other creatures can perceive, and as a result the universe's causality proceeds differently from what we see. Then you build up those cool science fiction ideas like Arrival, for example, which that was the A.B. Adams movie for years back, I think. Yeah, not the Charlie Sheen Arrival from decades ago, but the one where they have the linguist and the physicist instead of the astrobiologist

and the cryptographer. Yes, that one. The premise was, if you know your future, would you want to experience it anyway? Right? Oh, right. Yeah. And the answer is yes. I want to know my future. and then you want to live it i

mean even even if you know all the good and the bad but here's the thing is you wouldn't live it no one's going to live the future that they know but you may you may ultimately cause it but no one is going to live the future that they already know. So, Chuck, that's the problem. You're completely right if time is one dimension. If it is one dimension. And if time is two or three dimensional, then you don't. Maybe that's not the question. There you go.

Right. Good question. Alright. Okay. Loved it. Okay, Chuck, you got a question? Yeah, here we go. This is Morgan Fisher. Morgan Fisher says, Drs. Tyson and Liu, it's Morgan from Waterloo, Ontario,

of the Perimeter Institute. The Perimeter Institute. Perimeter. She says, I've wondered about this since first hearing of the LIGO experiments. It is said that colliding black holes create ripples in space time.

But what's the medium? There's no air. There's no water. It's a perfect vacuum. So what's actually doing the rippling? And I think she answered the question in the question. Let me lead off by saying the Perimeter Institute is a place of study where people are asking questions that kind of sit at the perimeter of established and accepted thinking in physics, math, philosophy, this sort of thing.

And so it's an audacious construct among institutions that are out there. construct among institutions that are out there. And if there's any weird, wild, wacky idea that turns out to be true, it's more likely to come from those kinds of think tanks rather than from those in the establishment. But Charles, why don't you take a gander at this answer? Well, Morgan, you have put your finger right on the concept of the general theory of relativity. Space itself is a medium. have put your finger right on the concept of the general theory of relativity. Exactly.

Space itself is a medium. What Einstein explained. Empty space. Empty space. What Einstein explained was that our conception of space being just vacuum or nothingness was incomplete. Rather, we should think of space as this sort of giant, either a rubbery sheet or a flexible sort of jello that we live in that can be bent and twisted and torn and so forth. So space is a lot like jello.

Albert Einstein showed that space is a lot like jello. You know, I mean, it's a children's song. Yeah. Well, now what part of the universe has the pineapple chunks in it? Earth! You see the pineapple chunks that sit in your jello mold, right? Some of you may have had that.

And the grapes. Yeah, that's the 1960s section of the jello mold. Yeah. The things that are floating in it are indeed mass. Massive particles and objects are agglomerations of mass, such as planets, stars, galaxies, and so forth. And those blobs cause an irritation to that otherwise beautiful, perfect jello. It's an irritant that winds up causing space-time to curl in upon itself.

And that's what gravity is. It's the curvature of space-time to curl in upon itself. And that's what gravity is. It's the curvature of space-time. What I like about the jello is you can send a ripple from one part of the jello, and that ripple will propagate out as a jello jiggle, and jiggle its way across the pineapple bits. And if you're in the pineapple, you'll feel a little jiggle as the wave moves across. Absolutely. So good job, Morgan.

You absolutely understand the point that Einstein was trying to make when he developed the general theory relativity. Yeah, but I don't know if that's a satisfying answer to Morgan because what you're saying is the vacuum is a thing, so get over it. That's really, I just gave the short version of your answer. Well, I didn't use get over it. I would say revel in it. Okay.

The nothingness is the thing, so revel in it. Enjoy. Make jiggles in it so that you can send it off to the next part of the jello bowl. All right. Okay, let's embrace the nothingness. Right. Next up, Dennis from Indiana. Black holes.

Are we sure Hawking radiation is coming from the inside of the black hole or is it just from around the event horizon? Has an observation ever been made of a black hole dying or disappearing, stellar mass or otherwise? Gentlemen. I want to reshape that question and hand it back over to Charles. So we know that Hawking radiation is birthed just outside of the event horizon. We know this, okay? That's how the calculations unfold. That's the... However, somehow that means the mass inside the event horizon drops.

And I want to ask Charles Liu, horizon drops. And I want to ask Charles Liu, how does the inside of the event horizon have any clue what just happened outside of the event horizon? And that's a reshaping, but a tuning of that question. That is a great question. And the answer still is we don't know. You see. Okay, next question. But the idea is that we know, mathematically speaking, Hawking radiation comes out of any object. It doesn't have to be just a black hole. It just comes off of any object that has mass, except that from a black hole, that's the only thing that can come out of the event horizon. And that's sort of the strange part of Hawking radiation. It's not that it is unique to black holes, but we couldn't measure it coming off of me, for example, or of Chuck or the Caribbean as much as we'd like to. It's a lovely place to be, but it's very, very slow and very, very small.

What happens to create that Hawking radiation is still a mystery. Hawking himself didn't understand. Now, you know, Neil, right, about how people often describe Hawking radiation as maybe like a particle getting close to the event horizon inside and then splitting off production into a particle and antiparticle, and then the particle escapes the event horizon, so on and so on.

That is pure speculation. That works mathematically, but physically, it has never been shown, and it's actually a little bit problematic, theoretically. I'm good with it, though. I'm good with it. If Hawking said it, I'm good with it, though. I'm good with it. If Hawking said it, I'm good. Wow. So, I mean, first of all,

you're talking about the evaporation of something like the Mojave Desert one half grain of sand at a time. That's right. Which is insane. That's right. Very, very slow. But answer my question.

If a black hole can evaporate completely, how does the inside of the event horizon know what happened on the outside? Or is the event horizon just a convenience for us to describe the edge, but really the black hole and its gravity field, the black hole maybe doesn't have an edge. It's wherever the gravity field is,

and the gravity field collectively is the black hole and the Hawking radiation comes out of the gravity field, therefore it loses mass. This is another frontier question. A paper was published about 20 years ago that suggested that mathematically Hawking radiation could be described as quantum tunnel. A thing where violating what we normally think of as the

boundaries of any given object, you can temporarily, every once in a while, get a little bit of stuff past the boundary. Right. And it's mathematically valid. So if it is a quantum tunneling process, then just as you said, Neil, that edge is a shimmering surface from which things can escape. It's a fuzzy surface. That's right.

There's a lot more that needs to be done. I would take a minute just to describe quantum mechanical tunneling, then we'll go to the next question, right? Sure. So if you try to get to some destination in front of you and there's a hill there, you got to climb up the hill and then climb down the other side.

And that's a pain in the ass. Maybe you don't have the energy to do that. So you never get there. In quantum physics, you're a particle and there's a barrier there. You're not just a particle, you're also a wave. And that wave occupies space. And part of your wave exists on the other side of that hill. And so there's a chance you could disappear from where you are and reappear still within your own

wave pattern on the other side of that hill. And when that happens, it's called tunneling, and it did not actually have to go over the hill and come down the other side to get there. And when it happens, it happens instantaneously. There's no time travel for it. The wave for the particle, as we say, collapses, and the particle exists outside of the barrier. Now, does this remain true even for Jack and Jill particles? Who went up the hill and came back? Jack and Jill didn't go up the hill to fetch the pail of water. They just tunneled right through it

and got the water. They just reappeared on the other side inside of their own wave. Hello, I'm Alexander Harvey and I support StarTalk on Patreon. This is StarTalk with Dr. Neil deGrasse Tyson. All right, who's next up? Is it Chuck? Gavin Bamber. And Gavin Bamber says,

hello from North Vancouver. Please visit. And then he says, in lieu of a nice question, I kneel down and ask the following. Oh, man. Three puns in a single sentence. Well done.

Now I really have to go to Vancouver. How many black holes are in our, are there in our galaxy compared to the number of stars? Is there a fixed ratio or is this just a random ratio? So, yeah.

Well, we know, and do you count the one at the center of our galaxy? That's just one. You know. One, yeah. So that does count. Well, this is a great question. I'd like to compare our estimates because both Charles and I have extensive research background in the answer to that question,

but we might not end up giving the same answer. So, Charles, let me hear your answer. Okay, here's my take. Black holes are formed only by the most massive stars dying. And so for every massive star that can create a black hole at the end of its main sequence lifetime star ratio is sort of millions to one. But then black holes, it has now been shown, thanks to LIGO and others, that black holes can coalesce and combine and create larger black holes. So that total amount can only shrink as you continue to go forward. that total amount can only shrink as you continue to go forward.

As big stars blow up, one in a million or less, new black holes can be formed. But then as they coalesce, they drop. I don't know what the exact mathematical ratio of all that is, but I'm guessing that it's millions to one or even more rare, black holes to regular stars. Neil, what's your take? Okay, I would say it's not as rare as you're suggesting even more rare. Black holes to regular stars. Neil, what's your take? I would say it's not as rare as you're suggesting.

Because it's just a simple integration of the initial mass function of stars. And you just find out the stars that are more massive than eight, eight or ten solar masses, whatever the threshold we agree that would be. What fraction of all stars in the galaxy are born

with a mass higher than that? I think it's not one in a million. And the reason why I say that is we have clusters of stars that don't have a million stars in them, but have a high mass star that would die that way, maybe 100,000 stars or 10,000 to 100. So I would say one out of every 100,000 stars in the galaxy, objects, stellar objects in the galaxy is a black hole as the consequence of the death of this process. Because when stars are made, they're made in, what's a group of stars, a pod? Or should we invent the name of a group of-

A cluster? An association? Yeah, that's so boring. I want a zoological. A litter. A litter of, thank you. A litter of stars born out of a gas cloud. We know that the low-mass ones, many more stars are made that are low-mass than are high-mass.

It's rarer and rarer and rarer. Interestingly, if you take a sheet of glass and drop it on the ground and it shatters, there will be more small parts than big parts. Okay? A lot of things land this way. The initial glass function.

The initial glass function. Very good. Very good. Charles, I'm saying, I bet it's more like one in 100,000, not one in millions. That's quite a discrepancy between one in a million and one in 100,000. But between astronomers, that's like the same number. Yeah, exactly. They don't care.

They don't care. What am I doing? My tax. Seriously, do you know what I'm talking about? Here's what I want to know. When a stellar nursery produces a litter of stars, does the galaxy then hound the rest of the galaxies to take one of them?

They're so cute, you're going to love it. We just need some galactic nannies to take care of them at the same time. Okay, so Charles, do you see my reasoning there? I do. I ask then, do you take into account very low mass stars

and brown dwarfs? Because if you think of a typical Salpeter initial mass function, right? 10 solar masses, every star that's 10 times the mass of the sun, there are 100 or more stars, 200 or more stars that are the mass of our sun.

And then- But those brown dwarfs, isn't another term for brown dwarf a failed star? Yeah. Yeah. Or an overachieving planet, right? Right.

There you go. Yeah, so- So what we're saying is that the initial mass function of stars would include these things that are not stars that would come in even higher numbers than the lowest mass stars. So Charles is just being sort of complete in the mathematics there. If you're going all the way down to the borderline of brown dwarfs, right,

then for every star that can produce a black hole, there are millions of objects that cannot. Other objects. There we can agree with that. And the initial mass function of brown dwarves appears to be flatter than that of regular stars that have nuclear fusions.

Okay, so Gary, we'll both do your taxes coming up, okay? And you can take the average of our answer and then you'll be bang on. I'm sure the IRS are going to love that taxes coming up, okay? And you can take the average of our answers, and then you'll be bang on. I'm sure the IRS are going to love that. I was going to say, you can take the average of the answers, and you'll still go to jail. I'll stick with someone else.

Gary, give me another one. Cameron Berg says, hello, Dr. Tyson Liu, and of course, Chuck himself, hailing from Salt Lake City. And his question is, is it possible that what we call matter and energy since the Big Bang have left a lasting or ghost effect in the fabric of space-time and dark energy continues to grow

because the effect keeps building as matter moves and expands into new space? So there we go. Cameron Berg's question. Is he saying, Charles, do you think he's saying that is the dark matter the absence of the matter that has moved from its location? Is this?

I feel like if I were to interpret this question more, it would be sort of like, is the residual effect of the Big Bang what the dark energy is as it fills space dark energy or dark matter did they say dark energy he said dark energy right and so i my response to that right anil you can correct me if you disagree uh that that won't happen energy they're very sweet a. Dark energy has been shown clearly not to be the result of matter and energy as we understand it, including dark matter. All the contents of the universe cannot explain how the universe itself is expanding in a way that is counter to that material.

itself is expanding in a way that is counter to that material. Especially given the fact that dark energy is operating in the opposite sense that energy, matter, and dark matter would have the universe behave. That's right.

So it's hard to explain one thing with the other when they are complete opposite in what their forces are. Right. The larger the universe gets, the more dark energy there has to be in the current formulation. And that just means that anything that's left over from what exists

in the current universe cannot power that additional dark energy creation. So deal with it. Wow. You are harsh today. I know. I'm with it. Wow. You are harsh today. I know. I'm getting old and tired.

And I'm on the porch on my rocking chair. You know, I'm feeling it. I'm feeling it. I'm older than all y'all. So I get to behave this way. No excuse. All right, Chuck, what you got? So this is Emil Forsblad.

Wait, what? Forsblad. Forsblad, who says... Wait, what? Hey, it's Forsblad. Forsblad. Emil. Emil. Emil Forsblad, who says, Hey, Emil from the San Francisco Bay Area, wondering about the potential measurement of consciousness.

I believe what we call consciousness is an energy or a quantum equivalent that emerges, grows, expands, converts like other forms of energy or slash matter. It seems that as the universe expands, consciousness is emergent as a natural result of the separation of all matter from its source over time. We likely need something to measure immersion consciousness if it exists as some fundamental energy. What would we use to measure other forms of energy like consciousness? Wow. Honestly, your consciousness right now is electrical. Wait, Chuck, that's the wrong reply.

It's, what are you smoking? I don't know. No, no, no. Chuck missed that one. I got low-hanging fruit right there. No, no, no. Emil, many people agree with your belief. Believe as you do that consciousness

must be something physical. It's a thing. It's a thing. Right. There is not yet any scientific evidence to confirm that if there were some way to measure it we'd be working on it right now in fact there where's it come from right there have been studies from though right there have been studies for example where they tried to measure the mass of a soul or a consciousness based on the mass of your body or your brain before an event and after

an event in terms of consciousness or unconsciousness, and there just hasn't been anything yet. So that said, we should consider the possibility, the more likely possibility, that consciousness is not an emergent form of new energy, but an emergent form of information or organization of well-known existing energy that somehow transcends just the motion of photons back and forth in our brains. Neil, you probably have much more understanding about consciousness. Well, I like what you said there, but I want to add to it. Yeah. Something that, I think it was Brian Green, we were having lunch a couple of months ago.

This came up in conversation and it's stuck with me ever since. All right. You want consciousness to have some energy field that might be shared among people. By the way, in physics, any time something happened that we couldn't explain, we investigated it, found out what caused it, exploited it, and then went to the bank with it. So go back in the middle of the 19th century, there's Faraday who puts a wire through a

magnetic field, and there's a meter over on the side connected to that wire, and it moves. And, well, how does that happen? It's like, today, which seems so trivial, back then was an amazing, you do this over here, and that happens over there. What did that? And then you find out there's current,

there's something called an electron, which hadn't been discovered yet, and all kinds of discoveries come out of this. Any time any of us in the physical sciences confronted something that was behaving in a way that we didn't know or know the cause of, we investigated it, okay? And so on a tabletop today, there's nothing left that is happening where we're saying we don't know what's happening. Not on a table, maybe in a particle accelerator, but on a tabletop, no. Your consciousness counts as a tabletop. Everybody's sitting around the table.

So now, here's the mind-blowing part. the mind-blowing part. When LIGO measures the gravitational wave washing over the detector, it is measuring the movement, it is measuring matter at the level of one-twentieth the diameter of a proton. And that is this wave that has moved through the universe of a proton. And that is this wave that has moved through the universe

for a billion years. If there was something going on in the universe affecting matter, we would see it in that experiment. If there was some mysterious other thing, oh, somebody has a sixth sense and they have an energy field and they got it.

It would show up in those data, but it doesn't. So I think we can speak with confidence that there's not some mysterious mind energy that's permeating space that science has yet to discover. Because I'll tell you what, if it was shaking up that atom,

we'd have to account for that before we measured the gravitational wave. And there was nothing there left to encounter. Charles, do you know I visited the LIGO in Louisiana? Wonderful. Oh, what a great facility that must be. And I happened to be there like three weeks before they made the announcement

and everybody was like hush lit because they thought I would just run to social media and say, no, I'm way more responsible than that. But anyhow, so when I watched the kind of stuff that they had to subtract out of their signal, with somebody walking on the ground 100 meters away, there they are right there, a car a mile away. There's an experiment where they measure the gravitational constant.

That's not LIGO, another one. Okay, so they got these torsion beams and things measuring, which is a very hard thing to measure. You realize there's a mound near that facility where if it had just rained, that mound is waterlogged and they can detect the extra gravity of the water that's in the soil. Yeah. It's pretty amazing.

So, anyway, that's my long discussion to say, I agree with you, Charles. It's not a new kind of energy or force. It's familiar energy configuring itself in such a way to give us a perception of reality that we call consciousness. So Neil, do we measure consciousness as positive and negative, bearing in mind the thought process you have? It depends on if you're into positivity or negativity. I don't know.

Haters will be haters. That's negative. That's right. Yeah. All I know is my soul did weigh 21 grams, but then I went the soul cycle and got it down to about eight. Oh, no. No. No.

Hello. Nice job. All right, let's get our next one up here. This is from Boutayeb Badawi, and he is from Nice in the south of France. Boutayeb, that brings back memories. All right. The surname Boutayeb.

Yeah, I'll tell you all about that. Boutayeb no. Butayeb is, I believe, the first name. And the family name is Badawi. If I've pronounced that incorrectly, my apologies. No, wait, wait, wait. Is this a European guest? Yes, from Nice. Nice in the South of France. Then they probably put their surname first, right?

All right. Butayeb. He's a Brit. What does he know, Charles? Exactly. No, no, no. I'm no longer European. I'm not allowed in.

That's right. In the Olympics, this is a famous Olympic story. In 1992 in Barcelona or 96 in Atlanta, I can't remember which one, there was a long-distance runner named Buteya. And he was in this 10,000-meter race. And two other people, someone named Chilemo from Kenya, another one named Ska, I think from Morocco,

were lapping. And he, you know, this Utaev was a great runner. He had won a number of international competitions, but he was in the way and you're supposed to move away. Yes, you are.

As Chilemo and Ska were coming toward him, Ska was like, move, move, move, you know, take the arm. And so he finally moved away. And what happened eventually was that Ska won and beat Chilemo. But then the event judges, the judges of the event took away his gold medal because they said that Gutayeb had helped him by blocking Chilemo. And it was quite the controversy.

What happened was it was reversed the next day upon appeal. But I remember watching that when I was a little kid, watching that actual event happening on the coverage for the Olympics. And then he was showing Ska being so upset, but then eventually coming back.

In every StarCook episode, I have to do this, right? Charles, how do you know that? How do you know that? Why do you know that? Okay. Because it does. So, Gary, I'm going with Charles' pronunciation here, okay? All right, I'm Butayeb.

Yes. Yeah, Butayeb, and it's been frenetically spelt for us here. So here we go. If we imagine a thought experiment where two photons of light travel parallel to each other, one in the vacuum of space, the other in a fluid. They both travel at the speed of light, and by definition, their respective experience of time is zero. However, their relative speed being different, life moves slower in the fluid,

they should actually have a different internal clock. How can we make that work as a question? Or is there a mistake in this experiment? Great question. It happens all the time, actually. And I want you to know that that's a great thought experiment, and it's actually a physical experiment that's been done a bunch of times. It happens when, for example, subatomic particles enter Earth's atmosphere. Say one subatomic particle misses the atmosphere and heads off into space. The other one comes into Earth's atmosphere and thus is going to the fluid known as the atmosphere, the compressible fluid of the gas over its atmosphere. And what happens is that indeed, they experience different times.

A fluid doesn't have to be liquid or wet. That's right. If a fluid takes the shape of its container, a gas would do that. So it can be compressible or incompressible. So the whole field fluid dynamics, the equations are the same that apply to the air or would apply to a liquid

because of the dynamics that goes on for objects moving through it. Continue, Charles. Yes, you're right. And so we have shown experimentally that the clocks for those subatomic particles that go through Earth's atmosphere actually run differently from the ones that are going off in space. And because of that, their decay patterns are different. Their half-lives are different, as measured by us, not in the frame of reference of the particle. So this is an experiment that has been done,

and there's some famous ones, specifically about a particle back then known as mu mesons. But we don't still call them that? We don't still call them that? We just, well, usually you just call them muons or mesons. Oh, muons. Sure, sure. Mu meson became muon.

Thank you. Yes, that's right. So you can find these experiments and show that indeed the clocks of those individual particles differed from those of their companions that did not enter the subs. Yeah. Great story. Oh,

by the way, the clock. so, so just to be clear, we're talking about particles traveling, not at the speed of light. They have clocks. Right.

But if you're actually traveling at the speed of light, you would not have a clock. And the question was about two photons, not about two particles. In that case, what you do is think about it as having no clocks, but through different media. And so the

speed of light will be different from one medium compared to the other. So you still have the same effect of causality of the surrounding environment having clocks. I hope that makes sense. I may not have explained it very well.

But the idea is that if you're thinking of time and measuring time of that photon, which itself experiences zero time, the medium still affects the measurement. So the speed of light is still the speed of light. The light is still traveling at the speed of light. It's just that stuff around it is slowing it to less than the speed of light. Less than the speed of light is still the speed of light. The light is still traveling at the speed of light. It's just that stuff around it is slowing it

to less than the speed of light. Less than the speed of light in vacuum. In the vacuum. Wait, wait. So, Charles, something I learned only recently because I never really thought about it. Yeah.

That when light slows down in a medium, it actually doesn't slow down. What's happening is it's still moving at the speed of light between the particles that it encounters. It just keeps hitting pieces. Right. Yeah.

And then it has to get through that particle somehow. It gets absorbed, re-emitted, or whatever, if it's coherent. Because if the glass is translucent, then it's not a straight line through. And if it's opaque, it's not getting through at all. So the molecules have to be just right so that it is transparent to the photon. So it moves through where there's no particle at the speed of light.

It's a particle that delays it because it's got to come out the other side to continue at the speed of light. Isn't that just what Chuck said? It is. But I wasn't going to say anything. Thank you, Gary. I like your explanation, Neil.

I like both explanations. They're great. I'm exerting positive consciousness. Yeah, so the energy of the photon just had to get in and out of the atoms or the molecules that were in its way. But between them, it's still moving at the speed of light. So it's getting refracted, it's getting diverted.

Yeah. All that can happen, and that takes time to get in and around the particles. But that's the energy moving, not a photon as a speed of light moving particle. So the point, Charles, is, and like I said, I only learned this much later in life than it should have been, that photons only ever actually move at the speed of light, even through a medium.

That's correct. I kind of see that. That's really cool. All right, let's get a little personal then. This is Mikael Bosworth, who says, hello, guardians of the Geeks. Love it.

There's a t-shirt. There's a t-shirt. Guardians of the Geeks. That's it. Mikael here from Canada. Who does Charles Liu call when he doesn't have one? Oh, no. Oh, no.

Well, Mikael, it's very kind of you to say that. But obviously, I know much less than what I don't know. So when I need information, the first people I go to are obviously… You know much less than you don't know? What does that sentence mean? people I go to are obvious. You know much less than you don't know? What does that sentence mean? It means that what I don't know far

outstrips on an infinite level what I actually do know. Gotcha. Except what you actually know far exceeds everybody else by an infinity. So they don't even know how to ask you a question in your infinity because we're still embedded

in our own infinity. Dude, that's too much. Thank you. You're very kind. But when I do have a question, my go-to people, Mikhail, are Chuck Nice and Gary O'Reilly. You guys may not know this, but

actually, Gary and Chuck, I wanted to ask you if you had a chance to take a look at my question that I sent you last week, where we would maybe use the cross terms in Einstein's field equations to figure out the topological constraints to a W, many worlds interpretation, quantum multiverse. Have you guys figured that out yet for me yet? And I wrote you back and I was like, what a dumb question. Oh, I mean, you had it, right?

I knew it. Gary, I don't know if you had a different opinion on that already. No, I'm selling that to really high-ranking think tanks at the moment, so I'm not prepared to discuss it in public. Well, when Chuck Nice and Gary O'Reilly

do not have a question answered for me right away, I usually go to my brilliant wife, Dr. Amy Radlew, and my three kids. I am blessed to be the dumbest person in my family. I'm going to address to that, actually, because I've hung out with this kid. Yeah.

And so I always... His wife has a PhD in mathematics. Yes. Charles is the dumbest one in the household. It is true. By far. Order of magnitude. So Amy and the kids are really helpful

and I always go to them if I don't know something. And then if we all have to look something up, I always try to find at least three different sources with three different answers to compare them. There's so much misinformation. If Breitbart doesn't have your answer there, and Breitbart, and Newsmax, and Fox News.

Really? I always want to be sure. There's so much information out there that I estimate that a third of it is outright wrong, and a third of it is sort of right, and then a third of it is probably right. And a third of it is sort of right. And then a third of it is probably right. So I'm always trying to find at least three sources of information,

people that I trust, sources that I know. I actually go back and read the papers if I can. The original sources, yeah. Yeah, look at the actual pieces of information. The real question there though, Charles, because that can be flawed. I can look up three different sources and they're not credible sources.

So how do you vet your source to make sure that it's credible? That's what I would want. That is a process. And sometimes it's frustrating. It takes quite a bit of time. I will look at the source and then I will look for references to that source and say, are those sources reliable or unreliable? What have other people said over long periods of time?

Very often, if you, say, type a search into any given search engine, the top 20 answers are all from the same source, but they're all just copies of each other, spread out everywhere else. You have to make sure there's independence among. That's right. So I don't hesitate to do that. It's a little bit of extra effort, sometimes a lot of extra effort to find the answers, but it's worth

it. It's the way that I protect myself from misinformation. So Charles is like the credible Hulk who backs up all of his claims with research and documented peer-reviewed journals. That's the credible Hulk. Chuck smash! Chuck dismember.

Okay, let's jump into the next question and we'll see. Because I think, you know what, it's a bit of a hot topic question, having looked at it here. This is from Jane Von Schilling from Scottsdale, Arizona. What are the possibilities of the combination of AI and quantum computers. So, does this devolve into another question where is one more powerful than the other? They're both badass,

and you put them both together? Yeah. And that's the end of us. Or is that the beginning? No. You put it together, and that is the end of humanity. Say goodbye.

Or does that solve Charles' problems? Let me tell you what. Let me tell you what the first, you know how like the first computers they had, well, they were numbers, but they were for calculations.

But the first thing that came out of the computer was hello, all right? Or the first. The first one from the Macintosh. Yeah. From the Macintosh. Hello.

That was the first thing that came out of the computer. The first thing that will come out of a quantum AI computer will be, oh, you F'd up now, dude. It could be, it could be. But I'll say this, right? Our understanding of intelligence itself may, in fact, evolve dramatically once we understand how quantum computing and artificial intelligence merge. It's really neat. computing is even in an earlier stage in its development than regular computing was in the era of those first counting machines that you were mentioning, Chuck.

We are decades away from being able to do anything like put a quantum computer on your desktop, right? Maybe essentially. Right now, the quantum computers are cryogenically cooled, they're the size of a room, and they're only able to do a few- Yes, it's a big hardware issue right now. Right, a few tiny qubits at a time to make the calculations, right?

But those tiny qubits can be extremely powerful, not necessarily because... A qubit is the quantum computing version of a bit. Yes, thank you, Neil, yes. We'd otherwise find in the computer. I should have made that clear earlier. That's why I'm here. Don't worry about it.

Keep talking. No, thank you. A quantum bit, a qubit, is a thing that depends on staying coherent with other qubits in order to make its calculations. The quantum coherence is extremely

fragile. It requires temperatures very close to absolute zero, almost no noise of any kind, electronic. If you look at it the wrong way, if you breathe on it the wrong way. Oh, yeah, yeah. It's all gone. So it's really, really in its infancy.

But it shows a great deal of promise in the sense that when you put in one and one, before it puts out two, there's a lot of stuff in between which we can't see and happens almost instantaneously. And so is that a measure of how our own brains work? That's a great question.

Artificial intelligence is attempting, is our current human attempt to use non-quantum, classical physics to mimic our brains and our intelligence and our consciousness, right? And we're seeing that that problem is almost intractable to mimic a human brain. I saw a YouTube video on this recently. It is remarkably complicated. We know the steps, but the hardware is seemingly insurmountable in its difficulty. So those two things put together might do it, but we still got a long way to go

before that actually gets to changing. The insurmountable complications of the human mind might not be what you'd want to emulate at all. You want to emulate the parts of the human mind that are capable of good things and accurate things. The actual human mind commits violence and war and crime and genocide and all of this. Not to mention that just the way that we perceive information

is a perception. We don't actually view information. We perceive information. Sure. Which is a big problem. After your senses dealt with it. Right. So it's easy

to praise the brain because we don't understand it rather than ask does the brain do things that we don't need to emulate at all because we can do it better by other means? Well, let's first understand it, figure out what's actually good and bad and what's causing them all,

all the interconnectednesses, and then we can distill the good stuff without worrying that that will accidentally cause the bad stuff to happen. And that's the frontier of neuroscience. But I agree with Chuck. Maybe AI will figure out how to perfect quantum computing. And then how to perfect human beings. Will it not then, as you say, Neil, solve its own problems?

I mean, look how long it took us from a computer the size of a room to get to a smartphone. That time is gone now. That won't take that length of time for it to solve problems that we think are impossible right now. The issue is how we solve the problems. By the way, that's 60 years. Put your finger right on the head. Well within lifetimes, right?

Well, think about this. If we put an AI on the problem of solving climate change, okay, it might be able to solve it in a day. But how would it solve it? By killing every human being so that we don't have to create any more carbon. You don't want that kind of solution, right?

That's the simplistic, simple-minded thing when you're saying, well, solve this problem quickly. No, that's evil AI. That's the evil AI. No, that's the AI that doesn't know the difference between good and evil. The immoral AI. The amoral AI.

So that's where that frontier is, I believe, Neil and Gary and Chuck. It's the issue of trying to make sure that we do it right and do it safe so that whatever AI doesn't ignore what we need of it. It's the other way around.

But if a human is in charge, if a human is in charge of AI and quantum computing... So we tell ourselves. Right. Yeah. Let's go with temporarily in charge. That's what you tell yourself about

your cat. Yeah, I'm in charge of my cat. I mean, yeah, that's never, ever, ever going to be the case. So the thing is, someone's going to have that immoral attitude and steer that intelligence

in a certain direction. There's not always going to be Captain Good Cat in charge of AI. And not everyone who's immoral believes that they are immoral. That's a whole other challenge that we have. There you go. This becomes very ethical. The winners of wars are those who write the history books. And so that's how that goes.

And just to be clear, in case people didn't know, you can be moral or immoral. Amoral means you are neither moral nor immoral. That's right. So that's just to be clear, people don't know how we use that term. And so, Chuck, if you're an a-hole, are you

neither one kind of hole or another? Right. Well, no. If you're an a-hole, we know exactly what kind of hole you are. You know, I will wrap up by saying that, Neil, you actually know this much better than I do. Astronomers have been using AI and machine learning technology for decades. We have no fear of this material. We are perfectly understanding that this can be used to do great things,

like help us understand data from millions of stars and galaxies when a single human being can do all that calculation at once. So it's not a matter of being afraid of it or saying, oh my gosh, we have to avoid it or oh my gosh, we must exploit it. It's another mystery, a puzzle, a tool that we can work with and we can learn about and we can sick on our unknowns. And if that fails, we all die. Okay, let's end on that note. We're all going to die. Well, we'll all die eventually, right? It's just a matter of when and how.

Yeah. All right, guys. Charles, it's always good to have you. It is such a pleasure to be here, everybody. Thank you so much for having me. Thanks for rejoining us. And we know that when we all visit your house, we just say, where's the dumb one?

I want to talk to him. That's going to be you. Hands down. Hands down. All right, Gary. Always good to have you, man. Pleasure, my friend. And Chuck, nice you are in Aruba right now.

Say hi to the Caribbean for us all. Yeah, man. Will do. All right, this has been StarTalk Special Edition, its own version of Cosmic Queries. A delight in its complexity and its joy, especially brought to us in the guise of

Charles Liu. I'm Neil deGrasse Tyson, your personal astrophysicist. As always, keep looking up.