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Speaker 1: Hey, welcome to Sign Stuff, a production of iHeartRadio. I'm

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Speaker 1: hoorhe cham and today we are answering the question can

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Speaker 1: we go faster than lights? Like the fastest thing in

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Speaker 1: the universe? And what would happen if you tried to

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Speaker 1: go faster. We're going to talk to a couple of

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Speaker 1: experts about this, including a famous theoretical physicist and a

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Speaker 1: historian of special relativity. So buckle up, put your helmets on,

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Speaker 1: because we are going to ludicrous speed to answer the

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Speaker 1: question can we go faster than light?

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Speaker 2: Hey?

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Speaker 1: Everyone? Okay, So today's question is a pretty deep one.

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Speaker 1: It goes to the very heart of what the laws

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Speaker 1: of physics in our universe are, and it has huge

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Speaker 1: consequences for what it means to have an orderly and

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Speaker 1: logical existence and reality. It's such a huge question that

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Speaker 1: it even stumped Einstein. So I knew I needed a

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Speaker 1: lot of help, which is why I called two very

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Speaker 1: smart friends of mine. And according to them, there are

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Speaker 1: three ways to answer this question. The first way is

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Speaker 1: to think about how fast light can go. Here's my

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Speaker 1: conversation with my first friend, famous theoretical physicist, New York

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Speaker 1: Times bestselling author and host of the Mind Skate Podcast,

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Speaker 1: Professor Sean Carroll. Cool, and I might crack some jokes.

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Speaker 1: That's the tone of the episode. That's okay, that's allowed.

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Speaker 1: We're allowed to entertain the podcast. All right, Well, thank

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Speaker 1: you doctor Carrol for joining us. Thanks very much for

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Speaker 1: having me. Please tell us who you are and what

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Speaker 1: you did. My name is Sean Carroll. I'm a physicist

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Speaker 1: and philosopher at Johns Hopkins University. I think about where

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Speaker 1: the universe came from, what it's made of, what the

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Speaker 1: laws of physics are awesome. Have you ever gone faster

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Speaker 1: than this of light? I never have. I've gone stoller

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Speaker 1: in the speed of light many many times.

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Speaker 2: I guess.

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Speaker 1: Just to start us off, what is the speed of light?

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Speaker 1: It's kind of something you can think about at different

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Speaker 1: levels of sophistication. To be honest, the speed of light

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Speaker 1: is the speed that light travels at in empty space.

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Speaker 1: So one very quick thing to get straight is that

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Speaker 1: light itself can travel at different speeds. Light travels at

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Speaker 1: a different speed through air or water than it does

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Speaker 1: through empty space. So when we're being a little bit

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Speaker 1: more careful, we say the speed of light in vacuum.

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Speaker 1: That's the special thing that's what people really care about.

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Speaker 1: That means that it's a speed of light when there's

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Speaker 1: nothing in the way, kind of nothing for the light

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Speaker 1: to bump into. Okay, so the first thing to know

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Speaker 1: about how fast light moves is that it has a speed.

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Speaker 2: It may seem.

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Speaker 1: Instantaneous when we turn on a light or a flashlight,

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Speaker 1: but it does take time for light to go places,

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Speaker 1: and this is something you can measure. For example, you

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Speaker 1: can shoot a laser at the moon and then see

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Speaker 1: how long it takes before it bounces back. If you

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Speaker 1: did that, you'd see it takes about two point six seconds.

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Speaker 2: Or you could send the.

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Speaker 1: Radio signal, which is also light, to Mars and you

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Speaker 1: see it takes about fifteen minutes on average for the

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Speaker 1: signal to go there and come back. The second thing

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Speaker 1: to know about how fast light moves is that it

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Speaker 1: depends on what it's moving through. If it's moving through

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Speaker 1: nothing or a vacuum, then it moves at its maximum speed,

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Speaker 1: which is about three hundred thousand kilometers per second. At

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Speaker 1: that speed, light can go all the way around the

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Speaker 1: Earth seven times in one second. But if it moves

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Speaker 1: through air or water or something transparent, then light slows

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Speaker 1: down and the denser that thing is the slower light

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Speaker 1: will move. So in a vacuum, light moves at about

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Speaker 1: three hundred thousand kilometers per second, but through water it

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Speaker 1: moves two hundred and twenty five thousand kilometers per second.

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Speaker 1: If it moves through glass, it's two hundred thousand kilometers

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Speaker 1: per second, And if it's a diamond, light moves at

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Speaker 1: one hundred and twenty four thousand kilometers per second, or.

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Speaker 2: Almost two and a half times slower.

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Speaker 1: And that's because even though these things are transparent, the

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Speaker 1: atoms still interact with the light. So when we think

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Speaker 1: about light traveling through water or glass or air, we

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Speaker 1: think it's transparent, it's just going right through, right, But

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Speaker 1: in fact, the light is being affected by the medium

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Speaker 1: it's moving in, by the very gentle electromagnetic interactions with

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Speaker 1: all the atoms that it might bump into. That's why

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Speaker 1: when you pass light through a prism, it will be

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Speaker 1: broken up into different wavelengths. Right, it'll become it'll be

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Speaker 1: the pink Floyd Dark side of the Moon album cover,

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Speaker 1: and white light becomes all the colors of the rainbow.

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Speaker 1: It gets psychedelic. You know, I'm not going to say

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Speaker 1: how you should best experience dark side of the moon.

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Speaker 1: That up to personal choices. Now, a lot of people

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Speaker 1: think the reason that light slows down when going through

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Speaker 1: something like air or water is that it's bumping into

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Speaker 1: all the atoms that are there. But that's not quite right.

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Speaker 1: The reason is a little technical, but basically, light is

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Speaker 1: an electromagnetic wave, and when it goes through water or

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Speaker 1: a diamond, the wave makes the electrons in the atoms

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Speaker 1: that are there wiggle, and the wiggling causes a kind

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Speaker 1: of counter electromagnetic wave that when you add it to

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Speaker 1: the original light wave, it slows it down. And it's

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Speaker 1: a good problem set for undergraduates learning this stuff for

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Speaker 1: the first time, because it's actually quite miraculous. It's the

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Speaker 1: net effect of all of the atoms has a sort

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Speaker 1: of simple calculable effect on what the light is doing.

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Speaker 1: It changes its speed. Okay, what does mean for the

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Speaker 1: first way of answering the question can we go faster

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Speaker 1: than light? Is that you can imagine setting up an

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Speaker 1: unfair race. On one side, you would shoot light through

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Speaker 1: a long piece or rod of a dense material like

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Speaker 1: glass or diamond, so that the light would be going

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Speaker 1: at half or less of its normal speed, and next

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Speaker 1: to it, you would hop into a rocket with nothing

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Speaker 1: in front of it but empty space. Now, you still

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Speaker 1: have to go pretty fast, thousands of times faster than

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Speaker 1: any human has ever gone before. But technically you could

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Speaker 1: beat the light going through that rod. If you had

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Speaker 1: enough fuel, you could get up to a speed that's

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Speaker 1: faster than that light beam, Which means that technically, one

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Speaker 1: way to answer the question can we go faster than light?

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Speaker 1: Is yes, in an unfair race. All right, you're probably thinking, sure, Jorge,

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Speaker 1: but that's cheating. And I imagine you clicked on this

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Speaker 1: episode to find out if you could go faster than

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Speaker 1: light without cheating. That is, can you go faster than

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Speaker 1: the speed of light in a vacuum? After all, that's

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Speaker 1: the question that's going to make it practical or not

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Speaker 1: if he could ever go to distant stars or even

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Speaker 1: to other galaxies. But here the answer is a lot trickier, because,

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Speaker 1: as it turns out, the speed of light isn't just

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Speaker 1: how fast light can go. It sets a universal speed limit.

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Speaker 1: Here's how Professor Carroll puts it. The slightly more sophisticated

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Speaker 1: way of saying it is the universe has a speed

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Speaker 1: limit built into the laws of physics, there is a

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Speaker 1: fastest speed at which anything can go, and unlike any

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Speaker 1: other speed, this speed is absolute. It is not relative.

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Speaker 1: It doesn't matter how you're moving through the universe, you

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Speaker 1: are going to measure the same speed limit relative to you.

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Speaker 1: It just so happens that light travels at this speed

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Speaker 1: when it's moving in vacuum. But other things do as well.

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Speaker 1: Gravitational waves, for example, also move at the speed of light.

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Speaker 1: So it's really a feature of space time itself. It's

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Speaker 1: a crucially important feature. It says that there are things

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Speaker 1: to our past, there are things to our future, and

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Speaker 1: there are things sort of sideways to us, things that

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Speaker 1: are neither in our past and our future, because we

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Speaker 1: can't get there without going faster than the speed of light,

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Speaker 1: which is not allowed. All right, when we come back,

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Speaker 1: we're gonna dig into everything Professor Carroll just said, and

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Speaker 1: we're gonna go into the mind of Albert Einstein as

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Speaker 1: he wondered the same question we are asking today, what

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Speaker 1: would happen if he could catch up to a lightbeam.

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Speaker 1: Stay with us, we'll be right back.

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Speaker 2: We come back.

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Speaker 1: Okay, we're answering the question, can we go faster than light.

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Speaker 1: And as I mentioned, there are three ways to answer

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Speaker 1: this question. The first is to cheat. You can slow

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Speaker 1: down light by making it go through something like water

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Speaker 1: or a diamond, and you could then technically beat it

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Speaker 1: in a race. The second way to answer this question

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Speaker 1: is to ask if we can go faster than the

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Speaker 1: fastest light can go, which is the speed of light

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Speaker 1: in a vacuum. And here the answer is trickier because

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Speaker 1: if you ask any physicists on Earth this question, they'll

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Speaker 1: probably tell you the answer is no. And so for

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Speaker 1: this segment, I thought i'd take you through the history

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Speaker 1: of how physicists arrived at this answer, because it definitely

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Speaker 1: wasn't by trying to go faster than light.

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Speaker 3: It sort of came in waves. It wasn't always clear

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Speaker 3: to people for all time that light even had a

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Speaker 3: finite speed. Some people wonder if light simply was instant,

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Speaker 3: as if it traveled at an infinite speed, and a

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Speaker 3: bunch of people wondered, maybe that's not right.

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Speaker 1: That's my other friend, Professor David Kaiser. He's a theoretical

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Speaker 1: physicist and a historian of science at the Massachusetts Institute

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Speaker 1: of Technology or MIT. According to doctor Kaiser, it took

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Speaker 1: a few hundred years since humans started doing serious science

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Speaker 1: in the fifteen hundreds, with people like Galileo to figure

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Speaker 1: out that light wasn't instantaneous and then it moved at

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Speaker 1: a certain speed. And that's at the stage for a

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Speaker 1: young teenager named Albert Einstein to ask a very simple question.

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Speaker 3: That's what sets up a pretty amazing intellectual journey that

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Speaker 3: leads to people like a young Albert Einstein and many others.

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Speaker 3: Right around the turn of the twentieth century. In the

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Speaker 3: early nineteen hundreds, Einstein was wondering, even as a teenager

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Speaker 3: really before he was doing very formal schooling. In this

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Speaker 3: he wondered, what would happen if I could catch up

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Speaker 3: to a light wave? What would I see?

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Speaker 1: What teenager Einstein wondered was, well, if light doesn't move

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Speaker 1: infinitely fast, if it moves at a set speed, what

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Speaker 1: would happen if you went faster and faster, could you

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Speaker 1: eventually catch up to a beam of light? And if

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Speaker 1: you did, what would it look like?

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Speaker 3: And so he had these wonderful, very visual, kind of

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Speaker 3: imaginary thought experiments in his head as a sixteen year old,

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Speaker 3: and he realized, well, if there's a surfer on an

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Speaker 3: ocean wave, and they're going at the same speed. If

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Speaker 3: they look from side to side, at least momentarily, they'll

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Speaker 3: see this wave kind of frozen, right, because they'll be

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Speaker 3: moving with the crest of the wave. There's some time

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Speaker 3: they would see basically a wave frozen in time, not

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Speaker 3: zipping past them. And Einstein wondered, well, why can't I

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Speaker 3: do that with a LightWave, or what would happen if

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Speaker 3: I if I zoomed up and traveled at the same

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Speaker 3: speed as a light wave, but I see a frozen

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Speaker 3: wave like that frozen ocean wave as a surfer.

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Speaker 1: In other words, Einstein wondered, as a sixteen year old,

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Speaker 1: if you can catch to light, would you essentially freeze

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Speaker 1: light or make it look like it's standing still? And

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Speaker 1: this question bothered Einstein. Okay, so then Einstein had this

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Speaker 1: idea that he nurtured since he was sixteen. And by

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Speaker 1: the way, when I was sixteen, I was definitely not

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Speaker 1: thinking about the nature of the universe. Not too loud,

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Speaker 1: that's right here we are.

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Speaker 3: So then what happened and then he got bothered by

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Speaker 3: that he was reading for fun as a teenager and

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Speaker 3: early college did there's still pretty new theory worked out

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Speaker 3: by people like James Clark, Maxwell and Hendrick Herritt's and others.

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Speaker 3: That was just scoring like win after win in describing

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Speaker 3: all these other things about light. It was like better

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Speaker 3: than anyone even imagined. It would match all these experiments

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Speaker 3: to high accuracy. It was a theory not only of

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Speaker 3: optics but also electric field magnetic fields. But in none

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Speaker 3: of those solutions was there a sense that you could

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Speaker 3: slow light down to zero. Wow, there was no mathematical

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Speaker 3: solution of these otherwise beautiful and very powerful equations that

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Speaker 3: showed a LightWave frozen in space.

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Speaker 1: So for young Einstein, this idea of going faster than

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Speaker 1: light and catching up to a lightbeam and seeing it

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Speaker 1: frozen wasn't allowed according to the other theories of the day.

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Speaker 1: It seemed to be true according to lots of experiments,

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Speaker 1: and so he came up with a pretty radical solution.

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Speaker 3: And so Einstein got bugged by that, and he wouldn't

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Speaker 3: let it go. Whereas other teenagers might think about other things.

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Speaker 3: For one, he got there and he realized one way

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Speaker 3: to remove this uncomfortable paradox would be to say, what

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Speaker 3: if the speed of light always has the same value,

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Speaker 3: even if I'm moving fast. What if every person who's

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Speaker 3: even in motion would measure the speed of light to

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Speaker 3: have that same speed of speed of light in vacuum.

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Speaker 3: If that's the case, that if he was careful to

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Speaker 3: say if whoa, then no one could ever catch up

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Speaker 3: with a light wave.

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Speaker 1: That's a huge leap. I mean it almost sounds like

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Speaker 1: a crazy idea.

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Speaker 3: It is not what most people were I think, that's

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Speaker 3: for sure.

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Speaker 1: Okay, here's Einstein's idea. What if you did try to

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Speaker 1: catch up to a lightbeam, you might start going faster

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Speaker 1: and faster behind it, trying to catch up to it,

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Speaker 1: and you would expect it to get closer to you.

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Speaker 1: But what if instead it never does. What if the

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Speaker 1: light beam always moves away from you at the speed

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Speaker 1: of light, no matter how fast you go.

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Speaker 2: And this is very strange.

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Speaker 1: And different than what we experience in our everyday life.

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Speaker 1: In our daily lives, we're used to speeds adding up.

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Speaker 1: For example, if you're driving down the highway at sixty

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Speaker 1: miles per hour and your kid in the back seat

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Speaker 1: throws a toy at you at ten miles per hour,

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Speaker 1: then to someone outside the car, they would see that

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Speaker 1: toy going at seventy or sixty plus ten miles per hour.

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Speaker 1: But Einstein said, what if that doesn't happen for light?

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Speaker 1: For example, what if you're going sixty miles an hour

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Speaker 1: in your car and you turn on the headlights. Expect

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Speaker 1: the light from your headlights to go the speed of

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Speaker 1: light plus to sixty miles an hour that the car

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Speaker 1: is moving. But Einstein said, nope, that light still only

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Speaker 1: goes at the speed of light. You and the car

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Speaker 1: would see the light go at the speed of light,

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Speaker 1: and someone standing on the highway would also see it

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Speaker 1: going at the speed of light. And this weird but

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Speaker 1: simple idea that light always seems to go at the

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Speaker 1: speed of light no matter who looks at it basically

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Speaker 1: revolutionized our understanding.

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Speaker 2: Of the universe.

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Speaker 1: Although it wasn't immediately a big hit, the.

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Speaker 3: First reaction Einstein's work was no reaction at all. He

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Speaker 3: was out of the way. He wasn't in an academic position.

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Speaker 3: He was, you know, frankly, kind of a nobody put

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Speaker 3: it this way. He didn't even get a promotion at

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Speaker 3: the patent office.

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Speaker 1: But eventually other people did notice Einstein's work.

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Speaker 3: Nonetheless, more time goes by, he's able to get a

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Speaker 3: fewer people to read the work and take it seriously,

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Speaker 3: and a few of them actually were beginning to do

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Speaker 3: things like write their own review articles and pay more attention.

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Speaker 3: So over a period that stretches nearly to a decade,

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Speaker 3: more and more of the professional scientists begin to pay attention.

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Speaker 1: Okay, you might be wondering, what does this have to

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Speaker 1: do with going faster than lights? Well, it turns out

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Speaker 1: that Einstein's sort of simple idea has some really weird

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Speaker 1: consequences for how the universe works. You might have heard

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Speaker 1: that time slows down when you're going really really fast.

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Speaker 1: That comes from Einstein's idea. Or that things look shorter

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Speaker 1: when they're going super fast. That's also from Einstein's crazy idea.

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Speaker 3: And he's very clear, I'm going to assume this right

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Speaker 3: and then say what will follow from that? And even

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Speaker 3: more stream sounding things followed from that, even in that

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Speaker 3: first nineteen to oh five paper. So from this postulate

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Speaker 3: he deduces other consequences. If you're zipping by on the

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Speaker 3: train at some high speed, you and I will disagree

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Speaker 3: on whether two events happened at the same time. This

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Speaker 3: becomes known as the relativity of simultaneity. Another thing he

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Speaker 3: begins to realize is that we're going to disagree on

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Speaker 3: the measurements of lengths if we're moving at a relative speed.

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Speaker 3: So it's called length contraction. And the third one is

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Speaker 3: time dilation. So if we have identical clocks that we're holding,

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Speaker 3: but you're racing past me at some outrageously high speed,

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Speaker 3: I will watch your clock tick more slowly.

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Speaker 1: The last main consequence of Einstein's idea is that nothing

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Speaker 1: can ever go faster than the speed of light. How

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Speaker 1: do we go from the speed of light, whether it's

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Speaker 1: the same in all directions, to concluding that it's a

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Speaker 1: speed limit for everything.

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Speaker 3: Partly because from Einstein's own equations, as you try to

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Speaker 3: get closer and closer to the speed of light, the

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Speaker 3: difference in measured clock rate, all these mismatches in lengths

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Speaker 3: of meter six times on clocks, even also things like

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Speaker 3: the masses, the way we measure mass, These things all

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Speaker 3: rise and in fact become infinite. And that's like saying

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Speaker 3: it would take basically an infinite amount of energy to

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Speaker 3: go as fast as that light beam does, and I can't.

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Speaker 3: I have no source of infinite energy.

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Speaker 1: Yeah, infinity can be a bummer, all right. When we

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Speaker 1: come back. We're gonna talk more about this explanation, whether

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Speaker 1: we've ever actually tried to go faster than the speed

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Speaker 1: of light, and then I'm gonna ask our experts what

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Speaker 1: they think would happen if we ever did break this

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Speaker 1: speed limit. So stay with us.

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Speaker 2: You're listening to sign stuff.

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Speaker 1: And we're back.

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Speaker 2: Okay.

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Speaker 1: We're asking the question can we go faster than light?

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Speaker 1: And so far we have two different answers. The first

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Speaker 1: is yes, you can go faster than light if you

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Speaker 1: slow down light by making it go through water or diamond.

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Speaker 1: The second answer seems to be no, if you mean

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Speaker 1: whether we can go faster than light in a vacum.

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Speaker 1: As we learn, it seems that the universe has a

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Speaker 1: speed limit, and the speed limit says nothing can ever

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Speaker 1: go faster than the speed of light in a vacuum. Now,

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Speaker 1: I know what you're thinking right now, which is have

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Speaker 1: we actually tried to go faster than the speed of light?

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Speaker 1: And the answer is yes. Since about the nineteen thirties,

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Speaker 1: scientists have been building particle accelerators. These are huge machines

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Speaker 1: that can take small particles like protons or electrons and

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Speaker 1: speed them up to go faster and faster. These accelerators

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Speaker 1: have been getting bigger and more.

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Speaker 2: Powerful over the years.

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Speaker 1: They've been pushing the limits of how fast we can

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Speaker 1: make something go. The largest accelerator right now, the Large

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Speaker 1: Hadron Collider in Geneva, Switzerland, is a seventeen mile long

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Speaker 1: circular tunnel that can speed protons up to ninety nine

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Speaker 1: point nine nine one percent of the speed of light.

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Speaker 1: What happens if you try to go faster, uh, not much.

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Speaker 1: As you get closer to the speed of light, it

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Speaker 1: gets harder and harder to make things go faster. To

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Speaker 1: actually reach the speed of light, it will take an

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Speaker 1: infinite amount of energy. Here's how doctor Carrol explains it.

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Speaker 1: All right, so we have this speed limit, and what

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Speaker 1: happens if you try to go faster than that? You

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Speaker 1: can try. The thing is that one of the equations

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Speaker 1: that Einstein bequeathed to us is a formula for how

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Speaker 1: much energy it takes to go at a certain speed.

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Speaker 1: We all have heard of equals mc squared. Right, energy

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Speaker 1: is vast times the speed of light squared. That's a

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Speaker 1: formula for what the energy is for an object with

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Speaker 1: zero velocity. If an object is moving with respect to us,

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Speaker 1: it also has what we call kinetic energy, and its

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Speaker 1: energy becomes bigger, and so there's a different formula as

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Speaker 1: that velocity goes closer and closer to the speed of light.

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Speaker 1: Einstein's formula for the energy says that the energy goes

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Speaker 1: to infinity. So the problem is that it would require

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Speaker 1: more than an infinite amount of energy to accelerate yourself

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Speaker 1: faster than the speed of light. It's one of the

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Speaker 1: ways of thinking about the fact that really you cannot

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Speaker 1: go faster than the speed of light. If you tried,

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Speaker 1: you would get closer and closer from our reference frame,

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Speaker 1: but you would never make it all the way there

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Speaker 1: is because you only have a finite amount of energy

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Speaker 1: to push you. Would you say then that the reason

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Speaker 1: we have a speed limit is because it takes an

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Speaker 1: infinite amount of energy to go faster than light. I

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Speaker 1: would say that fact, but I would say it the

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Speaker 1: other way around. I would say that it takes in

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Speaker 1: front of energy because we have a speed limit. It's

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Speaker 1: the speed limit that is really just fundamental. The existence

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Speaker 1: of a speed limit is really the defining feature of

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Speaker 1: space time, according to Einstein. Okay, and this brings us

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Speaker 1: to the big question, why does the universe seem to

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Speaker 1: have this speed limit. After all, it seems weird that

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Speaker 1: we live in a universe where you can't just go

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Speaker 1: faster and faster, that there is some sort of arbitrary

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Speaker 1: rule that curbs your speed and gives you strange phenomena

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Speaker 1: like time flowing differently for different people. I asked doctor

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Speaker 1: Carol this question. Okay, so now the question is why

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Speaker 1: do we have this speed limit in the universe. That's

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Speaker 1: an excellent question, And as we see, it is not

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Speaker 1: hard to bump up into questions where the answer is

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Speaker 1: there's no necessary reason why, Like maybe there's no such

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Speaker 1: thing as why it is a feature of the universe

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Speaker 1: that there is this speed limit. It doesn't seem necessary

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Speaker 1: if you think about all the possible laws of physics.

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Speaker 1: But since relativity came along, we know that the universe

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Speaker 1: has this feature, that there is a speed limit. But

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Speaker 1: do we have any kind of physical explanation for why

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Speaker 1: we have this speed limit? I don't know if that's

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Speaker 1: even a plausible question. You know, when you say what

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Speaker 1: is the physical explanation for something? When you really ask

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Speaker 1: is why is it? That it could not have been different?

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Speaker 1: Eventually you just say, look, that's the way it is. Okay,

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Speaker 1: that's more or less where we are with the speed

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Speaker 1: of light. It's just the way it is. It's annoying

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Speaker 1: that it's that way, because space opera becomes unrealistic when

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Speaker 1: it takes hundreds of years travel from one star to

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Speaker 1: another in your spaceship. But could it have been different?

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Speaker 1: As far as we know it could have been different.

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Speaker 1: We're just stuck with what we have. Okay. I get

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Speaker 1: this question all the time. So I wrote this book

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Speaker 1: for kids called Oliver's Great Big Universe, which you read,

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Speaker 1: Thank you for that. And I go around schools talking

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Speaker 1: about the book. And one of the biggest questions I

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Speaker 1: always get is what if I go faster than light?

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Speaker 1: And I always say you can't, you can't go. No, No,

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Speaker 1: I know, I know you can't. But what if you did?

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Speaker 1: And I say no, you can't, and they keep going no,

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Speaker 1: but what if he did? So John, why should I

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Speaker 1: tell these kids? So we think that there are laws

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Speaker 1: of physics, right, that it's not anything goes in the universe,

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Speaker 1: that apples fall down from trees. They don't just fly

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Speaker 1: up into the air when they fall off the tree. Right,

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Speaker 1: that the sun rises in the east, not in the West,

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Speaker 1: and that nothing can travel faster than the speed of light.

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Speaker 1: So it's not a choice that you have, or it's

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Speaker 1: not a matter of willpower or technological capability or anything

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Speaker 1: like that. You know, despite what you learn in Star

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Speaker 1: Trek and Star Wars, they're changing the laws of physics

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Speaker 1: because they want to have sort of a Western or

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Speaker 1: naval battle kind of feeling about what is going on

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Speaker 1: in outer space. But outer space is actually a very

437
00:24:31,920 --> 00:24:36,760
Speaker 1: different thing. So if you wet faster than the speed

438
00:24:36,760 --> 00:24:40,680
Speaker 1: of light, that would mean that everything we think we

439
00:24:40,800 --> 00:24:43,920
Speaker 1: know about the laws of physics is wrong. So if

440
00:24:43,920 --> 00:24:46,440
Speaker 1: someone asks what would happen, I got to say, Man,

441
00:24:46,520 --> 00:24:50,600
Speaker 1: I have no idea what would happen? Because you're telling

442
00:24:50,600 --> 00:24:52,199
Speaker 1: me I don't know anything other laws of physics, so

443
00:24:52,200 --> 00:24:54,639
Speaker 1: I have no way of saying what would happen. It

444
00:24:54,680 --> 00:24:58,879
Speaker 1: would go against everything we've observed as humans in the

445
00:24:58,960 --> 00:25:03,720
Speaker 1: history of humanity. Okay, what doctor Carl is saying is

446
00:25:03,720 --> 00:25:08,040
Speaker 1: that scientists don't actually know why we have the speed

447
00:25:08,080 --> 00:25:11,560
Speaker 1: limit in the universe. It's just a feature or a

448
00:25:11,680 --> 00:25:15,959
Speaker 1: rule that's built into it. There might be other universes

449
00:25:16,000 --> 00:25:19,000
Speaker 1: with a different speed limit, or even a universe out

450
00:25:19,000 --> 00:25:21,680
Speaker 1: there without the speed limit, where the speed of light

451
00:25:22,080 --> 00:25:26,440
Speaker 1: is infinite. But that's just not the universe we live in,

452
00:25:27,359 --> 00:25:29,639
Speaker 1: all right. I said at the beginning, there are three

453
00:25:29,680 --> 00:25:32,520
Speaker 1: ways to answer this question of whether we can go

454
00:25:32,680 --> 00:25:35,920
Speaker 1: faster than light, and so far we have a yes

455
00:25:36,400 --> 00:25:40,159
Speaker 1: if you cheat and slow down light. No, if you

456
00:25:40,200 --> 00:25:43,600
Speaker 1: follow the rules that we've observed about the universe. And

457
00:25:43,640 --> 00:25:46,560
Speaker 1: now the third way to answer this question is if

458
00:25:46,560 --> 00:25:50,320
Speaker 1: we put on our imagination heads and wonder about what

459
00:25:50,520 --> 00:25:55,640
Speaker 1: we don't know about the universe. To be a little

460
00:25:55,640 --> 00:25:58,359
Speaker 1: bit more fair, you know, physicists love to let their

461
00:25:58,400 --> 00:26:03,520
Speaker 1: imaginations run free. So we have imagined particles that could

462
00:26:03,560 --> 00:26:05,560
Speaker 1: go faster than the speed of light. We've even given

463
00:26:05,600 --> 00:26:10,280
Speaker 1: them a name. They're called tachions, and unlike ordinary particles

464
00:26:10,280 --> 00:26:12,840
Speaker 1: that can only go slower than the speed of light,

465
00:26:13,400 --> 00:26:16,760
Speaker 1: tachions can only go faster than the speed of light.

466
00:26:16,840 --> 00:26:21,199
Speaker 1: They can never slow down. Okay, so tachions are a

467
00:26:21,400 --> 00:26:25,600
Speaker 1: totally theoretical idea with no basis in experiments, but they

468
00:26:25,640 --> 00:26:29,879
Speaker 1: are technically sort of possible in the laws of physics,

469
00:26:30,359 --> 00:26:32,440
Speaker 1: and if they do exist, it would let.

470
00:26:32,400 --> 00:26:35,080
Speaker 2: Us do some pretty amazing things.

471
00:26:36,480 --> 00:26:39,320
Speaker 1: If you could go faster than the speed of light,

472
00:26:39,680 --> 00:26:43,160
Speaker 1: you could go to the past just as easily as

473
00:26:43,200 --> 00:26:45,760
Speaker 1: to the future, rather than me going fashion the speed

474
00:26:45,800 --> 00:26:48,040
Speaker 1: of light. Let's say I had a flashlight that could

475
00:26:48,119 --> 00:26:50,280
Speaker 1: shoot out tachions and they could go faster than the

476
00:26:50,280 --> 00:26:53,040
Speaker 1: speed of light. Right, I could send a signal to

477
00:26:53,080 --> 00:26:56,000
Speaker 1: myself yesterday, because going fashion in the speed of light

478
00:26:56,119 --> 00:26:59,159
Speaker 1: is just as bad as going to the past. Uh. Like,

479
00:26:59,200 --> 00:27:02,000
Speaker 1: if I shoot it at Alpha Centauri, will get there yesterday,

480
00:27:02,119 --> 00:27:03,840
Speaker 1: kind of, it very well could. And then if they

481
00:27:03,840 --> 00:27:06,640
Speaker 1: shoot it back, yeah, it'll get back two yesterdays ago.

482
00:27:06,720 --> 00:27:10,760
Speaker 1: There you go. So yeah, future me, if you have

483
00:27:10,800 --> 00:27:14,000
Speaker 1: a taki in flashlight, please beat me the numbers for

484
00:27:14,160 --> 00:27:18,320
Speaker 1: tomorrow's winning lottery ticket. All right, Like I said, tak

485
00:27:18,520 --> 00:27:22,159
Speaker 1: ins are purely theoretical, which puts this answer in the

486
00:27:23,280 --> 00:27:26,760
Speaker 1: maybe category. Until then, I guess we all have to

487
00:27:26,800 --> 00:27:30,320
Speaker 1: be law abiding citizens of the universe and live knowing

488
00:27:30,560 --> 00:27:33,880
Speaker 1: there is a speed limit to the universe, which our

489
00:27:33,920 --> 00:27:38,880
Speaker 1: expert argues is maybe not such a bad thing. You know,

490
00:27:39,080 --> 00:27:42,240
Speaker 1: the speed of light has a bad reputation because it

491
00:27:42,320 --> 00:27:45,239
Speaker 1: prevents us from being star wars. Right, it prevents us

492
00:27:45,280 --> 00:27:49,320
Speaker 1: from colonizing the galaxy and starting a galactic empire. But

493
00:27:49,840 --> 00:27:52,280
Speaker 1: I guess the lesson I would say is it also

494
00:27:52,960 --> 00:27:56,120
Speaker 1: brings a measure of control and predictability to the universe

495
00:27:56,200 --> 00:27:59,160
Speaker 1: that you wouldn't otherwise have. What it means is that

496
00:27:59,359 --> 00:28:04,600
Speaker 1: nothing you can do right here, right now instantaneously affects

497
00:28:04,640 --> 00:28:08,440
Speaker 1: things infinitely far away. So it's kind of a better

498
00:28:08,520 --> 00:28:12,119
Speaker 1: behaved universe. When there is a speed limit. You can't

499
00:28:12,119 --> 00:28:15,240
Speaker 1: instantly reach out and touch someone a gagillion light years away.

500
00:28:15,640 --> 00:28:18,840
Speaker 1: It seems less chaotic, I think, is what you're trying

501
00:28:18,840 --> 00:28:21,720
Speaker 1: to say, Like, not everyone's feeling everyone at the same time,

502
00:28:21,920 --> 00:28:24,320
Speaker 1: exactly right. It's a little more orderly. It takes time

503
00:28:24,359 --> 00:28:28,399
Speaker 1: for signals to travel. It calms down the universe to

504
00:28:28,440 --> 00:28:30,640
Speaker 1: have this speed limit on there. It's like if everyone

505
00:28:30,920 --> 00:28:33,919
Speaker 1: was forced to use mood and the like internet speed,

506
00:28:34,200 --> 00:28:36,679
Speaker 1: maybe our lives would be a little bit more orderly

507
00:28:36,720 --> 00:28:39,520
Speaker 1: and less chaotic. Yeah, the galaxy is not that big.

508
00:28:39,640 --> 00:28:41,680
Speaker 1: You just have to be patient. So maybe it takes

509
00:28:41,720 --> 00:28:44,680
Speaker 1: tens of thousands of years to cross it if you

510
00:28:44,720 --> 00:28:47,160
Speaker 1: go close to the speed of light, but that's nothing.

511
00:28:47,360 --> 00:28:50,080
Speaker 1: The universe is fourteen billion years old, you know, like,

512
00:28:50,200 --> 00:28:52,360
Speaker 1: be patient, we'll get there. The speed of light is

513
00:28:52,360 --> 00:28:55,360
Speaker 1: a good thing, I see, just adjust the perspective of time.

514
00:28:55,560 --> 00:28:57,920
Speaker 1: I'll tell that to the fourth graders that I talked to.

515
00:28:58,200 --> 00:29:00,600
Speaker 1: Just be patient. I'm sure that hell far good luck

516
00:29:00,640 --> 00:29:03,160
Speaker 1: with that. They'll be very understanding. I'm sure they always are,

517
00:29:05,080 --> 00:29:07,840
Speaker 1: all right. I think that answers our question for today.

518
00:29:08,240 --> 00:29:11,040
Speaker 1: Can we go faster than light? The answer seems to

519
00:29:11,040 --> 00:29:17,200
Speaker 1: be yes, sort of, No, not really maybe if there

520
00:29:17,200 --> 00:29:20,600
Speaker 1: are new things about the universe that we haven't discovered. Now,

521
00:29:20,680 --> 00:29:24,000
Speaker 1: why do we have the speed limit? We don't actually know.

522
00:29:24,520 --> 00:29:27,000
Speaker 1: That's just the way the universe we live in is.

523
00:29:27,520 --> 00:29:29,960
Speaker 1: If you live in the universe where this is not true,

524
00:29:30,200 --> 00:29:32,800
Speaker 1: send us a note. We'd love to take your experience

525
00:29:33,080 --> 00:29:36,960
Speaker 1: for a spin. Thanks for joining us. See you next time.

526
00:29:38,880 --> 00:29:40,560
Speaker 2: You've been listening to science Stuff.

527
00:29:40,680 --> 00:29:45,040
Speaker 1: The production of iHeartRadio written and produced by me or Hitchm,

528
00:29:45,200 --> 00:29:49,160
Speaker 1: edited by Rose Seguda, executive producer Jerry Rowland, and audio

529
00:29:49,160 --> 00:29:52,080
Speaker 1: engineer and mixer Kasey peckrom And you can follow me

530
00:29:52,120 --> 00:29:55,200
Speaker 1: on social media. Just search for PhD Comics and the

531
00:29:55,280 --> 00:29:57,920
Speaker 1: name of your favorite platform. Be sure to subscribe to

532
00:29:58,000 --> 00:30:01,520
Speaker 1: Sign Stuff on the iHeartRadio app, podcasts, or wherever you

533
00:30:01,520 --> 00:30:04,640
Speaker 1: get your podcasts, and please tell your friends we'll be

534
00:30:04,680 --> 00:30:12,000
Speaker 1: back next Wednesday with another episode. All right, that was fantastic.

535
00:30:12,160 --> 00:30:14,320
Speaker 1: I feel like I'd taken more than of your time

536
00:30:14,360 --> 00:30:16,040
Speaker 1: than I promise.

537
00:30:16,360 --> 00:30:20,280
Speaker 3: Well, we've just discussed time is relative. Class, running slowly fine,

538
00:30:20,800 --> 00:30:22,600
Speaker 3: We always talked for ten minutes. It's fine.

539
00:30:22,960 --> 00:30:26,000
Speaker 1: Yeah, that's right. When when a professor is putting at

540
00:30:26,000 --> 00:30:30,160
Speaker 1: sabbatical speed, time dilates and becomes meaningless

541
00:30:31,400 --> 00:30:34,000
Speaker 3: You are exactly know, exactly that's right,