StarTalk Radio - Cosmic Queries – The Experience of Time with Charles Liu

Episode Date: August 18, 2023

Is our experience of time a result of our perpetual movement? Neil deGrasse Tyson and co-hosts Chuck Nice and Gary O’Reilly explore spacetime, metaphysics, the Brachistochrone problem and more with astrophysicist Charles Liu.NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free.Thanks to our Patrons Marcus Karlstad, Vincent Zimmerman, Ryan Lambert, Carolyn K, Stefan C. Villafana, and David Churn for supporting us this week.Photo Credit: NASA, ESA, M. Robberto (Space Telescope Science Institute/ESA) and the Hubble Space Telescope Orion Treasury Project Team, Public domain, via Wikimedia Commons Subscribe to SiriusXM Podcasts+ on Apple Podcasts to listen to new episodes ad-free and a whole week early.

Today on StarTalk Special Edition, we brought in our geek-in-chief, the one and only Charles Liu. We talk about all kinds of things, like our experience with time relative to a beam of light. We also talk about what our favorite objects were in Star Trek that came true. What else? We also wonder, what direction should you launch a rocket? Is it straight up or is it sideways? That and more, coming up on StarTalk Special Edition. 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 always for these editions, we got Gary O'Reilly. Gary. Hey, Neil.

Good to be here again. Former professional footballer and professional announcer. And thank you to the soccer universe for lending you to us. That's very kind of you. Yeah. And we got Chuck. Nice, Chuck. Always good to see you, man.

Hey, that's right. And to the professional soccer universe. You're not getting that back. We got him. We got him now. You suckers. You lost. This is a grab bag cosmic queries.

Anytime the grab bag goes everywhere, guys, we got to pull out the big guns. All right. We open the shed and we pull out the ones. The only undisputed Charles. Friend and colleague. He's a professor of astronomy and physics at the City University of New York based in Staten Island. And with the Graduate Center there. And he's got a podcast called The LiUniverse, which showcases up-and-coming science talent.

We need some of that on this landscape. So good to see that happening. And so here's what happens. If you don't know Charles, he will bail us out of anything we don't otherwise know. And it works every time. That's right. Because he's the geek in chief. All hail.

That's right. All hail. The geek in chief. Charles Cocktail Party Lou. Because if there's anything you want to know, he's the guy at the cocktail party that knows everything. And I count myself high among the ranks in the Geekiverse. But in the Geekiverse,

the scale is infinite. So, however far I am, you can be geekier. And that's the man in the studio right now. Okay. So, this is a Cosmic Queries, or just Queries. It's a special edition. So, Gary, Chuck, who's first? I'll go first. All right. Okay. Gary, go for it. These are from our

Patreon audience, and we love them and bless them for their curiosity. And this is Chris Hampton's question. Could it be that our perpetual experience of time is because of our perpetual movement through the fabric of space-time. Ooh, I like that. So, Charles, let me add to that. If nothing moved in the universe, would we have any perception of time at all? We would. But it's a strange concept, right? Because as it turns out, many people will say, when one interpretation of the

special theory of relativity, which talks about space and traveling through space and traveling through time, is that everything is always moving at the speed of light. But it's speed of light, not through regular three space, but through four dimensional space. So you and I, we move through space and we have mass, we have space time, and we're moving sort of at the equivalent of a speed of light. A photon, which is a piece of light, has no mass, and it's moving always at the speed of light also. So in a sense, in this four-dimensional way of thinking

instead of a three-dimensional way of thinking, we are all always moving at the speed of light, but light itself is moving through space faster than we are moving through space only. So this perception of time is always a matter of what we perceive based on where we are and how we're moving through three-dimensional space, but also four-dimensional space. Why am I more confused than what? I was going to say, first of all, I hate to do this, but you got to tell me, why are we always moving at the speed of light?

Because I know that's what everybody is asking right now. Right this minute. What do you mean when you say, why are we always moving at the speed of light? Translated from Chuck, what were you smoking before you began this interview? Smoking a little bit of Albert Einstein, 1905. Right. Think about it this way. If you are traveling, say, in one dimension,

you measure how many, say, miles per hour you're going along the road. In a straight line. In a straight line, right. But if you're moving in two dimensions, say you're moving diagonally, like an airplane, right? Moving up diagonally during takeoff, it's moving both in the horizontal direction and the vertical direction. At the same time. Yeah.

And so when you take the combination of those, then you wind up with a new velocity vector. And the amount of speed you're going doesn't look the same as either right along the ground or vertically upward. Right. So it's adding this vector thing. Now, imagine space-time being that. Space is the horizontal axis.

Time, the fourth dimension, shall we say, is a vertical axis. So all three dimensions of space are this one axis right now. Right. It's one axis. Collapse them all together. Time, is a vertical axis. So all three dimensions of space are this one axis right now? Right. It's one axis.

Collapse them all together. Time being now the vertical axis. Exactly. Okay. Or the fourth dimension. Okay, let's keep going. So now go. It's not that hard. No, we ain't done yet.

Don't be saying it ain't hard yet. No, no. Yeah, go ahead. Then you do the same kind of thing where you use kind of like a Pythagorean theorem, right, you do the same kind of thing where you use kind of like a Pythagorean theorem, right? For what space-time does in terms of measuring distances and velocities and so forth. And so you wind up with the velocity that is what the speed of light would be just through space. So we all, everything is moving at that same velocity,

but depending on how we're moving through space, we also move through time a little bit differently. That vector, which toggles back and forth between the vertical and the horizontal, is always constant. Wait, just hold on. So if we're just sitting and having this conversation, we are moving in time.

Yeah, time. And so we're moving vertically right now in time because we're not really going anywhere. Yes. So now light is moving not only in time, but also in space. Yes. So now it's got, let's call it a 45-degree angle up there. Oh, that's the difference.

See, light has no mass. So it's always going horizontally only. So light particles don't actually age. We age as we sit here. So they're constantly in the present. Yes. In their own present. Exactly.

They're constantly in their own present. In their own present. That's right. One of the hypotheses that was trying to decipher whether or not the cosmological redshift was actually expansion of the universe or not was something proposed many decades ago by people like Fred Hoyle, who suggested that maybe the reason we see cosmological redshift, that things move,

things appearing redder than they actually are. Not expansion, but just that light as it travels, it gets tired. It loses energy as it moves, almost as if it had mass. That was called the tired light hypothesis. Right.

But does it still travel at the speed of light if it now sort of denudes its way through? Really what Gary just said is, what is red shit? That's really what he just said. That's for another time. But basically, it's the way the cosmos moves. It expands throughout. Right. What it's the way the cosmos moves. It expands throughout, right?

What used to be tiny is now huge. But as far as relativity goes and how our motion through space-time goes, right? We are this way and light is that way. Horizontal. Vertical, horizontal. And we wind up with this kind of… Who's going at an angle between us? We do when we move.

When we move. Right. Got it. If we're on a spaceship or on an airplane or something like that, we are going that. Then there's an angle because we're not only moving in space, but also in time. Because we're going up and horizontal at the same time. That's why one of my college professors who really understood this super well explained to all of us that

you can do special relativity using hyperbolic trigonometry. And he always thought, well, that was much easier. Well, who doesn't know that? Who does that, right? I mean, come on. Why wouldn't you?

Who doesn't do that? Which was cool, but I never quite understood it so well. All right. Wow. You're making me feel good, Charles, because you I never quite understood it so well. All right. Wow. You're making me feel good, Charles, because if you don't quite understand it, I feel in a better place.

This is a tough thing, guys. Yeah, man, it is. Wait, just to put the nail in his coffin. So, Charles, isn't it just being provocative to say we are moving at the speed of light? What you're saying is we're moving at our natural speed through time,

whatever we want to call that. Light is moving at the speed of light. What you're saying is we're moving at our natural speed through time, whatever we want to call that. Light is moving at its natural speed through space. But to say we're moving at the speed of light, that's a little needlessly provocative, it seems to me. It might be. That kind of phrasing probably is an intention-grabbing device more than anything else. But it also implies with it a need for you to understand what it means to move through space-time compared to what it means to move through space-time. Very good. It forced me to think about that differently. Right.

Because I'm naturally just moving forward in time at one second per second. And the light is naturally going through space, not aging at all. We're just doing our thing. That's right. However, what it did do for me was it allowed me to visualize the axes that you were talking about. That's really what it did. All right, cool. Next one.

This is Kevin the Sommelier. Kevin the Sommelier says, glad the Loonaverse is here. Nice. The Loonaverse has landed. The Loona here. Nice. The Loonaverse has landed. The Loonaverse has landed. If we are able to achieve warp capability one day, will we experience time dilation in accordance to Einstein's

general relativity? If Star Trek is correct, they age at the same rate as Starfleet in San Francisco. P.S. Neil, get your hands on some Hartford Old Vine Zinfandel from Russian River.

Oh, nice. Russian River. Excellent. Love Russian River. Napa's not cool enough anymore? No, Russian River does it right and Old Vines can't argue with that. Yep. Thank you.

Love Old Vines. All right. Yeah, well, Kevin, the bottom line is that. Yep. Thank you. Love old vines. All right. Yeah. Well, Kevin, the bottom line is that Star Trek does it wrong. Right? In order for… Yeah, I know. Excuse me. I know what I just said.

How dare you? I know what I just said. Take that back right now. Take it back. Star Trek is completely correct in the Star Trek universe. Star Trek, when it comes to warp speed and time dilation, is not correct when it comes to our understanding of the theory of relativity. So you're saying they shouldn't age while they're doing their high warp

maneuvers. Right. What should be happening, the problem is, you see, the high warp maneuvers are faster than the speed of light. Yes. And if an object moves through our current space at faster than the speed of light, then it can violate causality. And so that whole aspect of relativity and so forth is necessary to make sure that the arrow of time and the way that we know, understand history and the changing of the universe stays okay. The causes occur before events. Yes. When you have a circumstance like warps, right? That goes out the window.

This object, because it's in a subspace bubble, right? By the alchemy or drive or whatever. It goes through so fast that it can actually outrace a radio signal to a distant star. And so you can tell something that happened before the radio signal

was even arriving, which means that you violate causality. The way that they get around that problem is to say that communications also goes faster than speed of light. Also go through subspace. So you know those subspace communications and so forth, right?

And what that means is that I can still radio ahead, not with a radio though, but with something that's going faster than my spaceship is going, which is faster than the speed of light at that moment. And therefore, causality is not violated because all information that I've got before and after in that subspace is retained. So,

bottom line is, as soon as you throw in these fanciful ideas of how to go faster than light, then you have to assume that your communications also go faster than light and that light is no longer a speed limit for objects in the universe.

Therefore, causality can be preserved because you have everything able to go faster. So am I correct that that's why the wormhole works without that violation? Because you're not actually going faster than the speed of light moving through the medium of space-time. A wormhole should be just clean. A clean step through? It should just be clean. It's a clean step through. Except that wormholes at the moment

have not been determined to exist. No, no. Wait, Rick has... Well, they are in Star Trek. Rick has wormholes. Rick has wormholes. Doctor Strange has wormholes. Don't tell me we don't have wormholes.

Oh, we have wormholes. Does the universe have wormholes? I love all those wormholes. But yes, do we have one right now that's from faster than light travels Rick and Morty it's good enough

for Rick and Morty it's good enough for me that's right Morty that's right thank you Chuck do we really need the drunken burp was that really necessary

you can't do Rick without me. So who's next? Who's got the next query? All right. Next up is Manny Baez from New York City. All my life, I've always thought there is some connection from these three subjects, time, universe, and dreams. Like as in one is dependent on the other in order to unlock the center of this pyramid for answers. It may be that the answer can be a combination of science

and philosophy, but do you think this pyramid of subjects has anything to do with answering questions such as the value of life or why we exist in this universe? Danny, what a wonderful question. And linking the universe with some sort of metaphysics is something that has been done since the very beginning. of metaphysics is something that has been done since the very beginning. In fact, Neil will tell you that in the history of science, until such time as there was a true separation between empirical science and metaphysics, it was called natural philosophy. And we were always trying to philosophize until people like Galileo said, you know what? I don't think we should really mix how beautiful is a tree or how righteous is a star. Let's just talk about the tree and the star

and then worry about the philosophy separate. Yeah, in fact, Newton's most famous book, which we call Principia, the full title of that is Mathematical Principles of Natural Philosophy. And so the natural philosophy is part of that framing. Great point, right. So your ideas are great, Manny. They're right on target. And I would say is the following. As far as we know

right now, human dreams are limited in our existence, our perception. There is no evidence yet that our dreams are actually connected with the rest of the universe. That's the key here in terms of tying them together. For us and for our existence, dreams and time and the universe are linked. Charles, let me throw this at you. Premonitions. You can't get the future before you're out of the present but I've had premonitions that have come true so that's the future before and in the present

so how does that connect or is it wait a minute or is it a convergence of the past and all of your past that converges on one moment because the surroundings inform you

in such a way that you say, oh, this is going to happen. And so it appears to you that it has already happened, but really it's just your vast past experience coming together in one point, pre-another event. Well said. Can I explain one thing? I'm 19 years of age. I have not played in my football club's first 11, right? So I'm a way off of that. And about 10 days before it actually happens, I have a dream.

I'm running towards my own goal. I'm in the center of the field and I get punched in my left cheek. Wow. Random. So I'm playing in my full debut. About 10 days later, I'm running towards my own goal

in the center of the field. I get punched in my left cheek. I'm like, you are kidding me. Yellow card? No, carried on. It was allowed. Carried on? Yeah, I get punched in my left cheek. I'm like, you are kidding me. Yellow card? No, carried on. It was allowed. Carried on? Yeah, we played a different game back then. Unbelievable.

It was more rollable. Oh, man. For that, yeah. But for that to be part and parcel of that dream way ahead of time was just so random. So random. It's uncanny, right? Well, here is the point, right? We have not yet been able to scientifically confirm whether these things are random or whether they are actually connected. Think about this way. The human brain is essentially designed to make predictions of the future, right? We are spending our entire existences from the early days, right? We predict

that if that lion over there will come after me in this direction, therefore, I will run in that direction. We predict later on that the stock market will go up, therefore, we will invest. These predictions do not always come true. In fact, they rarely come true, but there are thousands of them. The brain is a prediction generator. brain is a prediction generator. So could it have been that your brain in its generation of predictions, which dreams to some extent are, right, go on and had so many predictions in your lifetime that just that one random one came true just by chance. And you remember the hits and you forget the misses. And you remember the hits and you forget the misses. I knew which stadium I was in. And it was just as dreamt. So it's really remarkable that way too.

And then there's a second factor, which I only recently learned from my psychologist friends. Apparently, we humans will adjust our memories. To match. Backwards. Yes. We humans actually have a, it's hard to know whether it's a defect or whether it's a reality.

True thing. We read, every time we remember things, our brain is recreating the memory. It's drawing it out. It's not like a typical, say, computer where it comes out and brings out a perfect copy.

It goes through a lot of, It's not a perfect copy. It goes through a lot of... It's not a movie camera. It goes through a lot of filters and it resets things. And people wind up misremembering, not on purpose, not to be lying, but their brains have actually shifted what they thought was real from the past.

So could it be that when you got hit in the face and maybe it was similar to feeling being hit in the face and maybe it was similar to feeling being hit in the face in the dream, your brain set it up so that thinking back to the dream, it wound up matching the two pieces and getting them confused. It is possible. And again, like I said, so many of you things are speculation and it's hard for us to establish what is actually scientifically causal or the case.

But that does happen. And part of the problem, Gary, is that you didn't write that down when you had the dream. That's part of the challenge here of verifying it scientifically. So that leaves whatever your dream was susceptible to exactly what Charles is saying about when you recover the dream. So, wow, this was bang on to exactly what happened. Well, the dream was about 10 days before the actual event happened. So it's... Yeah, you should just write down your dreams every single day. Okay.

And 999 times, it won't come true. And one time it comes true, you can't then claim special clairvoyance. I got to get me a dream diary. Exactly. So I guess to wrap up Manny's question, the idea is basically to say dreams definitely affect human experience and how humans interact with the universe. Does the rest of the universe, however, sense those dreams or react as a result of them?

That is something we don't know. Probably not. It's a very probably not, but people still claim it. Yeah, yeah. And listen, it informs a lot of people on what they do. So there is a significance there no matter what because there are a lot of people who are reacting to their lives based upon what they think is that information.

And by the way, it's another thing, Charles. I think a dream, as you know, is a neurosynaptic firings of your brain. And should that be fundamentally different from deep thoughts you might be having while you're not asleep? So what I find intriguing is almost every movie

that shows somebody who by some bolt of lightning or through drugs, becomes insanely brilliant. Yeah. Okay? Like the movie Lucy or the one phenomenon, I think it was. Oh, those kind of things. Okay. No, no.

In those movies, in every one of them, the person can control things with their brain. And I'm intrigued by that because if they're just really smarter, they should just simply solve problems faster or better. And somehow the urge in the storytelling is to have the power of the brain jump out of itself and become metaphysical.

Manipulate physical objects in your environment. In almost every case, that's the power they give them. But from the smartest person on Earth to the dumbest person on Earth, neither of them can move stuff in front of them without touching them. So to say, let's make the smart person even smarter, now they can spin tops and float objects, I don't get it. However, the truly smart people

know how to get other people to move stuff for them. Okay. Pick that up. Pick that up. Please pick that up. Please, please pick that up. Thank you.

Oh, yeah, that's right. Give me another question. Chuck, what do you have? All right, here we go. This is Camilla Kaftal, who says, Hello, Dr. Liu and Dr. Tyson. Camilla here from Baltimore, Maryland. How is the cosmic microwave background temperature so constant everywhere in the universe when

there are hot stars like our sun? Oh. Oh. Beautiful question. Oh. Oh. Conspiracy. Oh. Charles. Temperatureacy. Beautiful question. Oh. Conspiracy. Oh.

Charles. Temperature. Temperature. Take that one, Charles. Camilla, you've asked a great question, which sometimes astronomers don't do a good job of explaining outward. The cosmic microwave background does get contaminated by foreground objects. So if we were just measuring, like, say, for example, the WMAP satellite or the COPE satellite did, the cosmic microwave energy that's reaching us from the cosmos, what will happen is that we will pick up the stars in the front, the galaxy that we're in, and the cosmic microwave background in the back.

The trick that astronomers do, and it's not a trick, it's really hard work, is actually getting rid of that foreground signal. So your insight is exactly right, Camilla. The cosmic microwave background is contaminated. There was a result that reported

some new discovery in the cosmic background, and it was later found that they did not properly remove the effects of our galaxy. Correct. That happens a lot. Foreground… It's like the erase feature on your phone. Foreground contamination is actually one of the things in astronomy that we have to worry about much more than, say, a typical laboratory physicist.

that we have to worry about much more than, say, a typical laboratory physicist. They can try to remove as much of the foreground as possible, but we're stuck looking through the gas and the dust and the stars and the galaxies. We can't change our angle of view. Yeah, we can't change it. Very cool. Fun stuff.

Thank you. Yeah, Gary, what do you got? Okay, Kyle M. If a black hole is infinitely dense, why are some bigger than others? Hmm. Answer, please. First of all, Kyle, you know,

it's not always about size. Okay, that's number one. Oh, well, that sounds like somebody might need some size. I don't know. Chuck, I'll leave you to ponder that one. Here's the story.

A black hole is not infinitely dense. The only part of a black hole that's infinitely dense is its singularity. See, a black hole, the event horizon that surrounds it,

the edge, shall we say, of the black hole, contains a certain amount of mass. Within that container, the average mass is always less than infinity. It is just in the spot where we think exists, the singularity,

where the density is infinite. I hope that helps. Wait, wait, just to be clear, just to be clear. So when we describe the size of a black hole, it's the size of the event horizon just for practical purposes to describe how big things are. But the matter is deep within.

Normally, we think of the size of the Earth as the edge of the matter of the Earth. But the black hole, we just go to the event horizon and we're happy with that. Right. We do not know what's in size. We don't know. How it's distributed. Correct. So if that's the case,

it means that if it were a star at one point, I'm not talking about a supermassive at the center of the galaxy. I'm talking about just a star that collapses in on itself. We know that that star had a certain mass before it collapsed in upon itself. So if it had a certain mass before it collapsed in upon itself. So if it had a certain mass before it collapsed in upon itself,

how can the density of that mass become infinite at one single point if it started off with a finite mass? The mass itself doesn't become infinite, but the density becomes it, right? So for example, mass, let's say something is the weight of my head or something if i squish my head very small as a black hole would do if i fall into it right uh it would become more

dense but not more massive it would still take the same amount of energy or force to lift my head but you would need a smaller container why are you using your head as an example? Wait, wait. This is more good, Chuck. I was going to say, that was a painful... It just popped into my head. What can I say? Use a watermelon or something,

you know. I don't have a head for those kinds of jokes. So, Chuck Lowe, here's the deal. So, if that's the case, how can something become infinitely smaller and smaller and smaller and smaller?

At some point, doesn't it have to just be so tightly compact that it can't get any smaller? Great question, Chuck. And in fact, it is the people who study matter, mostly quantum physicists, who say that, yes, there must be a limit. But when Albert Einstein established the general theory of relativity, he did not see it. He was not happy with the fact that the mathematical equations of space-time allowed for the existence of these singularities. That's why they're called singularities, right? Because they don't follow the mathematical rules that you would expect for the space. It's where God is dividing by zero.

Oh my God. Who said that? You never heard that one? No. That's an interesting point. That's crazy. But it's kind of, Neil is right.

That's exactly what it is. You're dividing by zero. You're creating something that should not exist. If you've never done that before, do it on your calculator. Can you then make this thing that's reducing inside disappear

altogether? Or does it reappear somewhere else? Don't know. The current hypotheses suggest that black holes are not, say, tears in space time, in which case the matter or the mass would flow from one point to another. But rather, it's kind of like a hernia in space-time.

A water balloon where the mass goes in and kind of collects in a space or a time or something that's not part of the space-time we have access to. And then over many, many trillions and trillions of years, slowly gets expended outward again through a process called Hawking radiation. So check it out because Neil said do it. I just divided by zero on my, so the first time I did it,

I did zero divided by zero and it said, invalid format, please do not do. And then the second time I put one divided by zero and it said, can't divide by zero. And then the third time I did it and it went, no. The fourth time you did it said, I already told you no. I told you. But it's the examination of these singularities and unusual points in the equations of space-time that have led to these amazing discoveries and thought processes, like black holes, like the Big Bang, like those kinds of things that we're wondering about today that fire our imagination. Let's go to the next question.

This special edition of Cosmic Queries. Okay, all these questions. Yeah, thank you, Neil. All these questions from our Patreon audience. So thank you very much for your curiosity. Craig Cordwell from the UK. Please, can you briefly explain how it is more efficient and easier to launch a rocket going directly up rather than taking off similar to an airplane does.

So answers, please. Well. Now, Gary, could you please do that again, but do it in Craig Codwell's accent? Because you're both Brits. Okay, I don't know what part of the UK Craig Codwell is. How about if he's from Cornwall? I love the Cornwall.

Cornwall? Cornwall? Kernil? Yeah. Craig from Kernil here. Please, can you briefly explain who it is more of? Oh, it's how embarrassing. Sorry, Craig. Because he might be from Glasgow,

in which case he'd be very, very different. Or he could be a Scotsman. He could be a Scotsman. He could be all sorts of things. So I'll just have to go with… Liverpudlian. Oh, my God, no. Liverpudlian. Yeah, could be a scouse. That's true. It could be a scouse or it could be all sorts of things. So I'll just have to go with… Liverpudlian. Oh, my God, no. Liverpudlian.

Yeah, it could be a Liverpudlian. I can't dial up a scouse accent on demand. Sorry. Not too well. All right. Asking too much. Yeah. All right.

Obviously. So the answer to the question actually is that we do try to launch our rockets horizontally. When you see on the launch pad a rocket going upward vertically, the only reason it tries to go up first is because it's trying to build up speed because it will then start curling sideways. It starts moving horizontally because the best way to get into orbit or out of the gravitational well of a planet is to travel at a tangent, not straight up vertically. It's only up vertically to get off of the ground, away from the launch pad, over mountains and so forth.

And then the trajectory starts to curl, right? That's why, for example, we launched from Florida because it goes up for a short while and then goes horizontally over the Atlantic Ocean. So our sense that we launch vertically is actually just those first few seconds of our perception. Later on, if you want to go further and further upward while you're in orbit, you move tangentially. You move horizontally.

And that actually has been shown mathematically and engineering-wise to be the most efficient way to gain altitude up in space. Once you're outside of the slowing down effects of the atmosphere of the Earth. So Charles, here's something

f***ing amazing. You ready? Yes, go ahead. The exact trajectory of a rocket. You know what it is? It's an exact trajectory. I'll tell you what it is. It is the inverted,

the physically inverted solution to the Bercrystochrone problem. No kidding. Yes. Wow. Yes. I was going to guess catenary, but Bercrystochrone makes much more sense. to guess catenary, but because it makes much more sense.

It's way, think about it. Makes much more sense. Yeah, yeah, yeah. Yeah, I'm not telling you. It makes sense. Right? Yeah, of course, the ice cream cone problem. Everybody knows that.

Yeah. So there was a, was it Bernoulli? Someone posed a, some famous mathematician from the 19th century, posed the question, might have been the 18th century, posed the question, if I have a ball up here and I wanted to get down over, down, but over to the right a little, what path should I take? Should I put a plank connecting the two of them and roll it down? Will that get there faster than if it drops first and then curls around at the bottom? Okay, is there a shape?

Is there an arc that I could drop this ball? We'll get to that point at a lower elevation the fastest. This turned out to be a very hard problem. And it is not the straight line. There is a curve where it builds up speed falling. And then that speed gets forward, moves it forward very quickly. And the minimization of that is that you learn this in advanced mechanics, right? And I think that's what I did, Charles.

What class did you learn that? I think I was, I might have learned it. I think we got it as a bonus from my calculus. Yeah, yeah. My calculus teacher in high school, brilliant man, in fact, went on to write some really great books, review books about calculus. And he would throw in just these little things. Oh, by the way,

that's what kind of made math class cooler because math can be just like learning grammar or learning punctuation or learning vocabulary. And learn extra little tricks and fun things. But when you put them into like, hey, was this useful in some way? Was this a thing that you actually find out? Those are the opportunities where you make connections

and go, aha, this math stuff is cool. You bring it to life, Josh. I wish that had happened. Guys, guys, guys. We have digressed from the ice cream cone.

On purpose. No, no, no. We haven't diverged. We've embraced it, Chuck. As Gary just said, it brings it to life. Now I bet there are thousands of people

out in the podcast first that are wondering, what's the ice cream cone problem? And now they're going to look it up. And now they're going to learn math, which is based on ice cream because they like it. It livens up the subject.

It makes people say, oh, it's not just... What is the ice cream cone problem? No sprinkles. You said that the exact inverse of a trajectory of a rocket is the exact inverse of the ice cream cone principle or whatever. The brachystochrone problem.

Oh, excuse me. The brachystochrone, which is very much like cookies and cream. It's a new flavor. Bacrystocone. It's a new Ben & Jerry's. Let me tell you something, Neil. If they ever give you a Ben & Jerry's ice cream, you better name it Bacrystocreen. My only point is this math exercise is designed to find the fastest minimum energy path between these two points.

That's awesome. And so the minimum, no, just down and to the point. You take that, flip it up. It is the minimum energy expenditure into orbit. Because if you go up too high first, you wasted too much energy gaining altitude. If you go downwind first, you're wasting too much energy trying to go horizontal.

So it's the perfect inversion of that problem. Is there a way to launch by spinning? And then launching that way. This is actually a startup company. I heard about this just recently.

A startup company. Would you like to buy my series? No, no. Go. Go. Yes. It's a… They want to spin something to launch speeds.

There you go. And then they launch it. So they're not even using a rocket. It's just... Right. No, it's like... What would be the equivalent of when you put the astronaut

in the centrifuge? Centrifuge. Yeah. Like a medieval catapult. You could not throw an astronaut... Like a medieval catapult. It's a trebuchet. It's like a medieval catapult.

It spins around and then releases at a certain point. Right. You can't send an astronaut in there, though. The insides will turn to jelly. I mean, they're going to leave the catapult at like a thousand miles an hour. You know, just like sudden whoosh. You know, that kind of thing.

The G-forces will kill you. It would be too much. Yeah. So you're sending like payloads that can handle that sort of thing. But this is still in development. It would be too much. Yeah. So you're sending like payloads that can handle that sort of thing. But this is still in development.

It's about payload. Depends on what you want to say. I mean, okay, so if you've got no innards to explode or turn to jelly, then you're fine. Does this have a commercial

prospect in terms of, as you say, payload? Yeah, you don't use a rocket to put stuff into space. Well, it has been thought for a long time that the easiest way or the least energy way to get payloads up into space is just create a tether. Basically, an elevator going from ground

to thousands of miles in the air and just go up, up, up, up, up, up. And that'd be great. Stairway to heaven. Yeah. Well, there are two ways. I mean, you can go back, but in the long run, I mean up. And that'd be great. Stay away to heaven. Yeah. Well, there are two ways. I mean, you can go back, but in the long run. I mean, it's still time to change the road you're on.

Is jet fuel cheaper than rocket fuel? At the moment, yes. By a lot. Okay. So then why is it that we were transporting the shuttle when it's here on Earth by piggybacking it on the back of a big jet. But we wouldn't put it into space by piggybacking it up to the highest altitude possible, detaching it, and then letting it just fire rockets to go into space. Because the atmosphere is a lot thinner and you got a lot less space to go.

That kind of strategy is actually what was done in the early rocket planes, in the early spacecraft. In fact, some spacecraft now, for example, I think one of the commercial spacecraft done by some billionaire or another, reaches space by doing precisely that. You carry some sort

of a rocket on some sort of a plane and then you let the rocket go and then the rocket takes it the rest of the way. The rocket engine is way more expensive to build than the jet engine. So even if you save on fuel, even if it's just hydrogen and oxygen

versus some hydrocarbon or something, making the rocket work and not blow up and not move and not change, that's a lot harder than getting a jet engine on an airplane. It is not the majority cost of what's going on. So you got to watch out where you spend your money. I got you.

And the real deal is this. The moment you say, if we can get it up there without it blowing up, that's where you're lost. I'll see you when you get back. I will see you if you get back. Sadly, it's true. Let's try to get a couple more questions in here.

All right, I'll jump in with this one because this is an interesting one. Back to Star Trek, just as a spoiler. Connor Holm, in Star Trek, what is your favorite example

of a scientific prediction slash concept that actually became true but wasn't proven at the time? Ooh, I know my answer, but I want to hear everybody else's answer. I have an answer, but I don't know if it fits. Really? Okay, so here's my answer.

My favorite thing that has come true is the communicator. Indeed, all we have to do today is to pick up something a little rectangular and say, Scotty. Mm-hmm. Right? And Scotty can hear you. Yes, Captain.

Oh, sorry, that's Chekov. Same idea. Get your accent straight, dude. Okay. You're worse than me. Aye. In fact, our communicators are way more advanced than anything they used in Star Trek. Than anything Star Trek ever had.

Correct. How about that one who just touches the badge? How about he just touches his Starfleet badge and all of a sudden he opens up comms? That sort of touch, that touch activity on smartphones

that didn't exist at the time that now does? That's right. Okay. That's amazing. Yeah. Mine would be talking to your computer

and the computer talks back, which is their form of artificial intelligence. Computer, please tell me. And then the computer would give you information. Computer, please tell me. And then the computer would give you information. And we have that today. That's not science fiction anymore.

That's a great point. Right. Very good point. Right. Okay. And they don't use keyboards, right? That's not a thing. Yeah.

Is it my turn here? Yes. Yes, it is. Go ahead. Gary, did you give your answer? I did. You touched the Starfleet badge, and all of a sudden your comms are not touching. Oh, the badge touching. Just a touch. Bad did you give your answer? I did. You touched the Starfleet badge and all of a sudden you're calm.

Just a touch. Badge touching. So I have two answers. One, which I never thought would ever happen, happened. We could just walk up to a door

and it will open. But wait, even then you could go to a supermarket and do that. No, no, no. The supermarkets of the day had a touch pad. They have a pad on the floor. And you step on the pad and it would complete a circuit and No, no, no. No, no. The supermarkets of the day had a touch pad.

They have a pad on the floor. And you step on the pad, it would complete a circuit and that would open the door. Okay. But there were no pads. They would just walk up and the door just somehow knew

that they were there. And I said that. That's because there were two guys on either side of the door. Going. Post-production must have had a blast with that shit. i was i said i believe the photon torpedoes the aliens the warp drive but door opening just by walking up to it never okay another one i don't

think it was developed yet even if the science was there and maybe they wouldn't have known about it but they have this machine that instantly heats food which is basically a modern I think it also The replicator The replicator I don't know if it's

the replicator or it's just something that makes the hot food I mean the replicator doesn't necessarily heat it right so there's this this cavity

where it says I want some chicken soup they push a button and hot chicken soup comes out I count that like as a microwave oven. That's the original Star Trek, yeah. I know, but is that not a precursor to 3D printing?

Ooh. Well, the replicator is a precursor. Yeah, the replicator, I would say. The replicator would be the 3D printer. Yeah, that's another one that we've got to consider as well. Wow. And you know, there was a big prize. Was it an X Prize even that was announced?

The tricorder? The tricorder, yes. Yes, tell everybody about that that was announced? The tricorder? The tricorder, yes. Yes, tell everybody about that. Oh, well, tricorder was the thing that phones waved over somebody and figured out exactly what was wrong with them medically. Yeah. And so… I'm a doctor, not a computer technician.

Right. I'm a doctor, not a fill-in-the-blank, right? So the whole point was that if we somehow could do the same through remote sensing, just wave something over somebody and get all kinds of things, vital signs, things like that. We're getting close already, actually. For example, now we can take people's temperatures without touching them. Right.

Just in that little thing. And then you get the radio, you know, the infrared off of the surface. There was a NASA thing, by the way. That's right. Oh, absolutely. For a tricorder to work, would you need to have certain implants in the body that would allow that? It would help, but it would not be necessary.

He's lucky you're just scanning a code then, aren't you? That's right. That would be very useful, but it would not be necessary. Okay. The whole point of the tricorder is that you can just diagnose what's wrong just by remote sensing.

And some things you can do. But, you know, we're really close already because we're using light. So, you know, a lot of these instrumentations uses light to actually get the reading from the body. That's right. So, you know. So, that's photonic.

So, Charles, so there are two kinds of tools then. One of them is receiving whatever your body is giving it. So, if your body is is radiating a little warmer, you see that extra high temperature infrared. So passive receive. Passive. But another one, maybe you'd have to have the person walk in front of x-rays

and then read something that you've actually put through the body. Right. The Doppler radar for weather forecasting, for example, you do that. You send a radar pulse down to the ground, it comes back up. And depending on what to the ground, it comes back up. And depending on what it's like when it comes back up,

what the time delay is, how strong it is, and things like that, you know whether there were clouds, whether it's raining, whether it's clear. Or how much rain there was even. Right. By the same token, maybe it can send some sort of pulse, a harmless piece of information,

radiation down through the body or onto the skin. When it bounces back, it can read the results and see, ah, yes, this person has a skin infection of this kind on their, you know, that part of their skin. And therefore, we need to run. Or, Captain. We need to cut off their arm. Oh, no, no.

Which is my answer to everything medically. What? Look at that. We're living in the future, people. What? Mm-hmm. Anyhow living in the future, people. What? Mm-hmm. Anyhow, guys, we're out of time.

Oh, damn. It was a good question to end on. That was fun. We each had our own little bit of thing there. So, very good.

StarTalk Special Edition with the one and only Charles Liu. Charles, thanks for coming in for this. Always a pleasure. Thank you so much. Great having me. Undisputed Geek and Chief only Charles Liu. Charles, thanks for coming in for this. Always a pleasure. Thank you so much. Great to have me.

Undisputed Geek and Chief, Charles Liu. You guys are too kind. Thank you so much. All right, StarTalk Special Edition, signing out. Neil deGrasse Tyson. Keep looking up.