StarTalk Radio - Things You Thought You Knew – Faster Than Light

Episode Date: July 15, 2025

What’s up with the fourth dimension? Can anything travel faster than light? Neil deGrasse Tyson and Chuck Nice explore things you thought you knew about dimensions, tachyons, and isotopes.NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here: https://startalkmedia.com/show/things-you-thought-you-knew-faster-than-light/Thanks to our Patrons John Amneus, Eric, LUC THEO 280, Alex Mata, Katik, David Drain, Gwen Blake, Claira Broach, Keenan Smout, Zack Dagle, Ted, Julie Garisto, Trevor Whitfield, Lax Starkie, Bored as It, Vic Carnage, Martin Reavis, Tim Racine, Jodi Raffoul, Steve Wolf, Kimberly Dossett, Tyrell Blaylock, Samantha Lus, Daniel, odie wrex, Dakota Riffee, Joe Cutler, Odessa Rose, Nathan, Ang, A vat of K, Charles Boudreau, Zachery Hunter, Ashanti Abdullah, Madelaine Tully, Rocío, Becky Ziegler, Monty Thorstenson, Suresh, Ryan Pacharzynski, Andrew Pierce, Shervin Koramdel, Tim, Brandon Hughes, JJ M, lou, Moe Fury, Eric Max, Bren Plummer, Tyler Scott, Tom Davies, Marilyn Rivera, Jeff Nesmith, June504760, Colin Montoute, Billie Williams, and Jason Hamilton for supporting us this week. Subscribe to SiriusXM Podcasts+ to listen to new episodes of StarTalk Radio ad-free and a whole week early.Start a free trial now on Apple Podcasts or by visiting siriusxm.com/podcastsplus.

Coming up on Star Talk, we've got another Things You Thought You Knew episode. This time we talk about dimensions, isotopes, and tachyons. Check it out. Welcome to Star Talk, your place in the universe where science and pop culture collide. Star Talk begins right now. So Chuck, here's a topic I don't think we talk enough about. Dimensions. Dementia, huh? No, no. I can say to you, Chuck, I'll meet you tomorrow at Starbucks.

Right. And what's your reply to me? I'll be there all day waiting, man, because I got nothing to do. I got nothing to do. So I'll just be in Starbucks. I'll start off in the morning with some breakfast, maybe a little muffin. And then I'll just stay there until you get there. OK, sorry. I'll meet you at Starbucks at 12 noon. OK, thanks. Thanks. Thank you. Appreciate that.

I gave you a location in space and you had to wait until I gave you a location in space and you had to wait until I gave you a location in time. Time. And that intersection of space and time is called your world line. Whoa, love it. It's called a world line. World line. So for our world lines to intersect, we have to be at the same place at the same time.

See now fellas, if you're smart and you're single, you will hold this one in the back, put it away in your back pocket. Okay. You know what I mean? Girl, I just need you as a part of my world line. Ah! It's the rap lines from Relativity. Exactly.

Okay, and let's reverse that. I'll say, Chuck, I'll meet you tomorrow at noon. North America, good for you. Thank you, Earth. Yeah, Earth. Is that all right? Yeah. So we know intuitively you need both the time and the space coordinates conjoined in order to actually meet.

Absurd variance on that would be you cross the street and 10 minutes later a truck barrels through in that same location. Right. So you are in the same location as the truck, but not at the same time. You wouldn't say, oh man, I almost died today. You wouldn't, because your world lines missed each other. Right. And you can do that another way. You exist at the same time as the truck, but you know we're near each other in location.

Right. So, what made Zoom and other video conferencing so useful during COVID is that you only had to be at the same time. Right. You didn't have to be at the same place. So you take away one of the components of the world lines and then many more people can participate.

But you are converging at the same place virtually or digitally. Okay, well your image is, I mean I have my image of you on my computer but it's not you. So let's keep talking about dimensions, ready? So we have one dimension, which is just a line. The measure of the line is the length. There's no other measurement you can make of it

that has any meaning. It does not have a width. Now you can add another dimension, let's call that X. We add a Y, and now you have a surface. A plane. A plane, and then it's two dimensions, X and Y. Okay, so you can make a square out of that, couldn't you? Yeah.

Two dimensional beings who live in that surface, to everyone else in that surface, they only have an outer perimeter. Right. You can't see inside their bodies. They're all inside the flat plane. Inside the flat plane. That's all they can see. All you see is the edge of them.

Right, the edge. So, medical surgery in a two dimensional universe, they'd have to cut you open, part you, and then reach in and do what they need to, come out and then stitch you up again, okay? Right. If we live in three dimensions, you get to look down on that flat world

and see all the inner guts of every living creature in that universe. Mm-hmm. Because there is no boundary above and below, it's only within the plane itself. You can see the heart beating, you can see the spleen, the liver, the pancreas, the lungs, you can see it all. In fact, if you wanted to be a surgeon for that world, you could go in, cut out the appendix if they needed appendectomy, and never have to cut through their outer boundary. You'd be like magically going into their body.

Dimensional surgery. Dimensional surgery. They would have no access or even awareness that that was even possible, but you do. Right. And you can go in and rectify that. So now, we are in three dimensions. We reveal our skin in all directions to the other people.

Right. So our skin is the boundary between our innards and a medical doctor. If they want to get inside you, they got to cut you open. Right. A four dimensional creature can just look inside our bodies. Oh, I feel violated. I know.

Oh. I hope no one's watching right now. God. Anyone from the fourth spatial dimension has full access to your entire body's innards. Oh. They could pull stuff out, put stuff in, operate, whatever. We are the game operation to anybody in the fourth dimension. What I'm saying is, if you had what you beautifully refer to as dimensional surgery, you would

be able to operate without ever cutting someone open, provided you come from a higher dimension inward. Right. And it is completely analogous to be a four-dimensional surgeon operating on us without cutting us open to be we as three- surgeons operating on two dimensional creatures because you can just see all their organs just sitting there. Now we can move forward and back, left and right, up and down. Okay?

Those are the three spatial dimensions, but the time dimension you don't have access to the past or the future. We are prisoners of the present, forever transitioning between our inaccessible past and our unknowable future. But let's think this through. How would you imprison a two-dimensional creature? Draw a line. What kind of line?

A square. A square, just draw a square, that's its prison cell. Yeah. But we say, wait, just step up out of it And then you escape good to go. I don't know what you're talking about I'm fully locked in fully locked in. How do we put us in a cell? We have Six walls right that ceiling floor four walls around us All right

We think we are completely contained within it a higher dimensional creatures Just step out and then step back in and you're outside the cell We said I don't know what you're talking about. Right. Wait a minute. I said a four dimensional creature. If we had access to the fourth dimension, which for us is what?

Time. Time, but wait, we're prisoners of time. So suppose we weren't prisoners of time. Suppose you could move through time the way we move through space. Could you then escape the prison? Yeah, just move to a time when I'm not in prison. Exactly.

Exactly. Exactly. Just say, let me get out of these six walls here. You just go back to a time before you got put in a prison or go to the future where you were let go in the prison. Right. Each of those counts as escaping the prison without ever breaking down the wall. So time can serve that same role

if you had access to the past and to the future. That's pretty cool, man. Of course, we go higher, there's fifth dimension, sixth dimensions, this sort of thing. And mathematically, you can calculate what all the properties are, And it's fascinating to watch. Another quick one, you ready? Go ahead.

Knots in strings only exist in three dimensions. Okay. In other words, in a fourth dimension, you hand them a knot in the fourth dimension and say, wait, just pull the ends. And it unravels itself. That's the same thing as we three dimensional people looking at two dimensional people and they have a string

that just has this loop in it. One loop. And they say, how do I untie this? I can't untie. Say, dude, pick up the two ends and stretch. They can't do that. They can't do that. So knots are different things in higher dimensions.

The way to do it is you have to make a knot out of a two dimensional ribbon. And there are ways to do that, I think, rather than just out of a string. So a lot of interesting things change and are mind boggling for ascending to a higher dimension. Sweet. One last quick thing.

Why does anyone want a flying car? So you can get up and over traffic. So you only really think about flying cars in cities where you're plugged with traffic. And what a flying car gets you is another dimension of travel. True. You know when you're stuck in a one lane road,

cause that's bad, all right, but even if you go two dimensions and you have multiple lanes, cause now you're in a plane, that can get cloggy too. Right. So get a third dimension is wide open, but wait a minute,

that means we already have flying cars. It's called the subway. Ooh. Instead of being in the air, it's underground, bypassing the traffic you're in. It's still invoked the third dimension. Mm. But also, it means overpasses,

where the freeway goes right through and the overpass goes, oh, that's a flying car right there. You invoked another dimension. You have a very low bar for what's called flying. I'm Joel Cherico and I support Star Talk on Patreon. This is Star Talk with Neil deGrasse Tyson. Chuck, yeah, have you ever wanted to travel faster than light? Sure. I mean, who doesn't? I mean, I spent countless hours just sitting around saying to myself, I wish I could go

to like Proxima B and just float above it and be there. You may know that Voyager 1 is the fastest thing we've ever sent out of the solar system. If we had aimed that towards Alpha Centauri, the star system that contains Proxima, this very closest star to the sun, you would get there in plus or minus a few months, 70,000 years. But even if you went there at the speed of light, we would watch you take four years. Your time would stop. So you would get there instantly.

But you want to cross the galaxy, that's 100,000 years. Earth time for you to do that. So we need other ways to travel. Experimentally and theoretically that you cannot travel faster than light. Rue space. Right? you cannot travel faster than light, right? Rue space, right? However, some decades ago, someone hypothesized, suppose you don't increase your speed to try to get to the speed of light.

Suppose you exist on the other side of that boundary. You just start life on the other side of that boundary. What would that be? What does that even mean? Okay? So if you look at the equations of relativity, there are three things that happen as you travel faster. Your time slows down as you near the speed of light. Right. Your length shortens in the direction of your motion and your mass increases.

Okay. Okay, the direction of your motion and your your mass increases Okay, if you try to get to the speed of light as a physical object your length shortens to zero your math mass goes to infinity and Time stops Okay, this is just insane. This is insane because the equations blow up there. That's the numbers, right? Okay, there's a numbers give you. Okay, the numbers give you. All right. So, it was hypothesized, suppose you come at it from the other side. So you're not working your way towards the speed of light.

You just exist with speeds that are already faster than the speed of light. So you don't have this violation of approaching the speed of light itself. Okay. When you do that, what comes out the other side is that you live backwards in time. Oh, that's a bad, bad button. Okay. So it's not just that, you know, time slows down to time now goes backwards. A B the slowest you can travel is the speed of light. Right.

And in fact, it would take infinite energy to slow you down to that speed. Right. In the same way it would take infinite energy to speed you on this side of that universe. To speed you up to the speed of light. To speed you up to that speed. Right. So someone said, could anything exist there? And so we came up with it. We, people decades ago, came up with the name tachyons.

And that's cause they dress poorly. Tachyons. They just mix in stripes and polka dots and all kinds of madness. But electrons are protons, they're bad ass. Electrons are protons, they GQ to the max. Tachyons don't, in fact, they're the worst. Plus... Tachios don't affect them. Plus they'll come late,

they'll come early, they don't know when they'll show up. They don't even know when they'll show up. You know, what do you want? I'm on tachyon time, brother! Tachios, from the Greek, is a word for speed. Okay. So tachyons, the slowest they can go is the speed of light, and the fastest they can go is

infinite speed. Right, yeah. So in that case, you can go any distance. You can go is the speed of light and the fastest they can go is infinite speed. Right, yeah. So in that case you can go any distance. You can go any distance you want. In any amount of time. Right, because at that point you don't need a warp engine, you need a tachyon engine. You need a tachyon. A propulsion. A tachyon chariot to carry you through the galaxy.

Oh nice, well look at that, well you made it very poetic and it's the vehicle of the Greek gods. Here's an interesting fact that the early universe expanded faster than the speed of light. Right. Okay. Now, the way that happened was the space itself is expanding. Right.

Nothing is moving through space. Nothing is moving through space. Right. Space is no longer a medium. It's the actual vehicle. The medium through which you're moving, it is the thing itself. It's the thing that's moving. There's no violation of the speed of light there.

And we learn that from the general theory of relativity, which generalizes all of the parameters for which there were very specific descriptions in the special theory of relativity. Right. In other words, the special theory of relativity involves constant motion with no acceleration. So it's a simplified case, if we can call relativity simple at all. The simplified case, the general relativity involves accelerations and gravity and curved space time and all the rest of this. When you learn about space and time as a fabric of the universe, it can stretch at any speed

at all and the early universe stretches faster than light, it can stretch at any speed at all. And the early universe stretches faster than light. So that's where that's coming in. Right. In case there was a question about it. Yeah. But now it turns out you can travel faster than light in a medium where light travels with a lower speed than it would in a vacuum.

Okay. So like water going, like water. Like going through water, like going through glass, like going through diamond, all travel slower than like going through a vacuum. Gotcha. Those lower speeds, hey, we can go fast. We know how to send particles faster than those speeds.

We do that all the time. When we accelerate electrons and protons and particle accelerator. So in a diamond, light travels 40% as fast as it does in empty space. Wow. If light were 60 miles an hour, in a diamond light's going 24 miles an hour.

Right. So what happens now if we send a particle faster than light in the medium? We didn't know and it was tested. And we found out that when that happens, the whole universe explodes. Everything disintegrates like a Thanos snap. So you have water and so now you take a particle and accelerate it not only to the speed of

light in water but exceeding it and when that happens there's a flash of light. It's called in that case, Scherenkopf radiation. Scherenkopf radiation? The speed of light would be faster in air but still slower than the vacuum of space. So air is less dense than water, water is less dense than diamond. Okay so we're getting slow light when it hits our atmosphere and comes down to us. It's already slowed down. It's already slowed down. It's already slowed down. So it bends in the atmosphere then it bends again going into the water. You have a diamond ring

underwater it bends going into the diamond ring. Wow. So you got to get a four bend path on that. So my point is going faster than light triggers this reaction between the charge particle, electron and proton, and the medium and flashes of blue light come out. It's called Cherenkov radiation. We should just, Cherenkov light, just to be simple. All light is radiation. Exactly. So it scares people.

It was radiation, oh my God. Yeah, you're being bombarded with radiation every single day, all day. Correct. It's just low energy radiation. Your arms don't fall off, right? Right. High energy radiation that is ionizing, that's bad for you. Low energy radiation, it makes no difference to your body.

Body doesn't care. Exactly. So this thing about going faster than light and then emitting this energy is kind of like a sonic boom, right? I mean, it's conceptually similar. You go faster than sound in the medium, then there's this shockwave that comes out upon doing so.

So think of it as kind of a light shockwave. Oh, that's pretty cool. You know what will just bypass tachyons? What's that? Wormholes. Of course, yes. Yeah, wormholes, you don't need rockets. You don't need transporters like what they have

on Star Trek. Right. Just open a portal, step through, you're there. There you go. You don't have to be dematerialized, beamed and then rematerialized on the other side. And not only that, that material, I think, only goes at the speed of light.

You're still limited by the speed of light, even when they do beam. Right. All right, that's all I got for you. All right. This is the most time we've ever spent about talking about something that we don't know exists. That we don't know exists.

That's pretty cool. There it is. There it is. There's a word, a subject, a topic of interest that I think people don't know as much about as they should. Okay. It's all about isotopes. There's a sequence of elements beginning with hydrogen and they get sort of heavier and heavier and heavier.

Right. And they each have a number. So hydrogen is number one. Helium is number two. of elements beginning with hydrogen and they get sort of heavier and heavier and heavier and they each have a number so hydrogen is number one helium is number two so we're not just numbering them that is the count of protons in their nucleus right who's got 12 protons who's got six protons there is an element and only one element that has that many protons in the nucleus. There you go. Some famous ones, carbon has six protons. Six protons. Oxygen has eight protons. I left one out. Nitrogen has seven protons.

Okay. Uranium has 92 protons. When the periodic table of elements was being discovered, there were gaps. So you knew exactly what to look for if you were missing an element. Look for the one with 39 protons. Go back to the lab. It's like a chemical Lego set.

Hey, you just put it in a slot, click, clicks right in, and you move on. And so we have found 92 quote natural elements in the universe, one through 92. Hydrogen right on up through uranium. And we have another, how many, up to 118 now, going beyond uranium. We made those in the laboratory.

You think you can play god sir? You're just making elements now? The answer is frankly yes. So these are the protons and they're immutable. What I mean is if you take away a proton it's no longer that element. It's the other element. Right. If you add a proton it's now a different element. Wait a minute Protons all have the same charge Hmm, they all have positive charge. So what does it mean to cram them into?

The nucleus of an atom if left to their own devices they would what? Oh man They you know, it's they'd be the Real Housewives of New Jersey. That's what they'd be. Get out of here, get out of here, what you, hide the front, hide the table, hide. So what holds them together? Well there's a whole other force of nature called the strong force.

Fundamental force of nature? Fundamental force of nature, and it's propagated by a particle called the gluon. Right. Aptly named, I might add. And this happens by the presence of neutrons in the nucleus. Right. So neutrons tamp down the resistive forces and they act as a sort of a glue for the nucleus. Okay.

Unless you're Martha Stewart Adam, in which case it's a hot glue on. That was terrible. They all can't be winners like you said. Exactly, you know, I'm going to say, Martha should not have gone to prison for that. I should have. So, hydrogen in its native state only has one proton.

Right. It doesn't need a neutron. Right. To hold anything together. So native hydrogen is just one proton and then one electron on the outer side. Oh, by the way, in a red blooded atom, they have as many electrons as protons. So they're electrically neutral. Right.

Okay. So uranium would have how many electrons? As many as it has neutrons. No, no, as many as it has neutrons. No, no, it's amazing it has protons. I mean protons. Protons, how many is that? I don't know.

You don't remember? I said it. 92. 92, exactly. So matter is generally neutral for this reason. Okay, hydrogen is happy. Let's go to helium. Helium has two protons.

Its native state has two neutrons. Okay. Suppose I force hydrogen to accept a neutron and I cram it in there, okay? I can do that. Now I have what's called heavy hydrogen. Heavy hydrogen. It has a whole word that we have for it.

It's called deuterium. Oh. You might have heard's called deuterium. Oh, you might have heard the word deuterium. Do tell. What does deuterium do? You can make a water molecule out of deuterium. H2O. If one of those hydrogens is a deuterium, then it's D-H-O. Is that heavy water? That's heavy water. Heavy water. You might have heard of heavy water, yeah. You can add two neutrons to it. Okay. We have a word for that. Obese water.

No, it's something. It's called tritium. Tritium. Point is, when you do this to an atom, adding neutrons or possibly subtracting neutrons, if it has stuff it won't miss, you made an isotope. Ah ha. So deuterium and tritium are isotopes of hydrogen.

Of hydrogen. Let's go to carbon. Carbon has six protons in the nucleus. Right. So red blooded carbon would have how many neutrons? Six. Six, and it'll have six electrons. Six electrons. Carbon, bada bing. Okay. And it'll have six electrons. Electrons.

Carbon. Bada-bing. Okay? Oh, wait a minute. I can add two neutrons to it. Ooh. So now it has six protons and now eight neutrons. Add those two numbers together.

What do you got? 14. 14. Oh! Carbon 14. Carbon 14. As in carbon 14 dating. Yes, yes.

You know, someone should make a carbon 14 app, a dating app, that'd be kinda cool. That'd be kinda cool. So, that's an isotope of carbon, alright? It turns out carbon 12 is stable. 12 is six protons, six neutrons, it's stable. Right. You add two neutrons, it's not stable.

It will decay. And a half-life. And a half-life. And the half-life of carbon-14, if I remember correctly, it's around 5,000 years, which means after that amount of time, half of the carbon-14 is no longer there. It has decayed. And then you wait another 5,700 years,

half is gone again. You wait another 5,700, it's half a half of a half is an eighth. So you keep doing this, and you know what it does? It gives you access to dates across all of recent human history. From when we were in caves up through recorded history, right on up back through 1,000 years ago, 500 years ago.

So it's very useful for dating life on Earth. Some carbon that's in your body is carbon-14. So how do we end up with the carbon-14 in our bodies? So carbon in nature, add carbon-13 in there too. So carbon-12, stable. Carbon-13, stable, there's not much of that. Carbon-14, unstable. Unstable.

Okay, so in the environment, carbon-14 would normally just disappear, except there are sources of carbon-14 from cosmic rays from space. Space rays? Space rays. Space rays. We got space rays. Okay, you know what else boosted carbon-14 levels?

What? Nuclear tests that went on in the 1950s and 60s. Oh. So here's what happens. When you are alive, you uptake that native amount of carbon 12, 13, and 14 into your body. And it stays at that level until you die because then you stop ingesting more carbon. It's carbon in all food you eat basically. All food that has any nutritional value, has carbon in it.

The moment you die, you're no longer refreshing the carbon. And the carbon-14 then decays. And then that's when we can figure out the timing. Correct. The nuclear tests have interfered with some of the baseline measurements of what's going on in our environment. So you have to sort of get the nuclear tables

together with the tables of nature in order to figure out what the starting levels were for life forms that were exposed to it. We've actually put the finger on the scale. Yeah, the thumb on the scale, yeah, yeah. The thumb on the scale with the nuclear test. Yeah, with the nuclear test. Anyhow, I was just, you know,

chewing the fat here with isotopes. I love it. And they're a fun other part of what's going on on the periodic table of elements. Yes. And one other thing, hydrogen has one proton and helium, remember, has- Has two. And helium in its native state has a total of four nucleons, two protons, two neutrons, and it's stable.

Okay. nucleons, two protons, two neutrons, and it's stable. Okay, it turns out that's called helium-4, because it's got four particles in its nucleus, two protons, two neutrons, helium-4. If you take away one of the neutrons, guess what you have? Helium-3? Yes. Yeah. Helium-3.

Now here's what's cool about Helium-3. Helium-3 is one of the particles ejected by the sun and it gets embedded into the lunar surface. We might have talked about this in another show. So Helium-3 is yet another isotope, but now that's one with one fewer neutrons instead of more neutrons. That was another installment of Things You Thought You Knew. Neil deGrasse Tyson here as always, keep looking up.