Introducing: The Rest Is Science

Forget what you think you know about reality. The Rest Is Science is a mind-bending new show from Goalhanger that tears down familiar ideas… time, randomness, beauty, it will reveal just how bizarre the world truly is. Join Professor Hannah Fry and science creator Michael Stevens (aka Vsauce) twice a week to explore big, small and surprising questions as they deep dive into theories, concepts, objects and thoughts and take us on a journey into the unexpected. If you love digging into details that usually get skipped over, this is the show that proves reality is stranger than fiction. Click here to subscribe to The Rest Is Science. Learn more about your ad choices. Visit podcastchoices.com/adchoices

• 0:02Speaker 00

  Hello, The Rest Is Politics listeners. I'm Michael Stevens.

• 0:05Speaker 01

  And I'm Professor Hannah Fry. Well firstly, thanks to Rory and Alistair for letting us take over the channel to tell you about our new show for Goalhanger, The Rest Is Science. Every week, we take a fresh look at the familiar. We're going to be exploring the forces, the theories and the phenomena that shape how we live in, think about and see the world. We're going to pull apart what we take for granted to reveal the unexpected patterns and hidden logic just beneath the surface.

• 0:33Speaker 00

  Because that's what moves science forward. Not the polishing of answers, but the sharpening of questions. It's curiosity that sparks those, hey, wait, how does that actually work? Kind of a moment that changes the way we see the world.

• 0:46Speaker 01

  So, okay, here is a little glimpse of what is to come from our podcast. And if it sparks something unexplainable for you, then you can join us every Tuesday and Thursday for new episodes of The Rest Is Science, and we'll figure it out together.

• 1:01Speaker 00

  How would you describe gravity to an alien from another universe that had never experienced gravity?

• 1:07Speaker 01

  The simplest way to think of it is that in our universe, objects are attracted to each other. And if you, without any interfering from outside, if you just have two objects near each other, they will come together. That's it. I mean, that's it, really.

• 1:24Speaker 00

  And at this point, the alien goes, what? That is so odd.

• 1:27Speaker 01

  Right.

• 1:28Speaker 00

  And what do you mean by an object?

• 1:30Speaker 01

  Anything with mass. Anything with mass. Because I think that we sort of imagine gravity as though it's like the Earth is pulling us down. But the thing is, is that we're also pulling the Earth up, right? And if you get much smaller objects than planets and you put them in space, they're pulling each other and will come together.

• 1:50Speaker 00

  That's right. Yeah, I once calculated that two baseballs placed in intergalactic space, a meter apart, would very slowly collapse in towards each other until they touched. It would take three days for that to happen, but it would be because of their gravitational attraction to each other. We are gravitationally attracted to each other right now. It cannot overcome... The air it would have to push out of the way, the friction between our butts and the seats, but yet we are attracted. In fact, when you're born, right, you've got some, some zodiac constellation that's like, I don't know, it's, how does, how does astrology work?

• 2:29Speaker 01

  Something, something, something Pisces.

• 2:31Speaker 00

  Right. Okay. So, okay, you're a, you're a Pisces if you're born in a particular time of the year, but yet the gravitational influence of Pisces on you is less than the gravitational influence of the doctor who delivered you on you.

• 2:45Speaker 01

  Cause otherwise, birth ain't working.

• 2:47Speaker 00

  That's why, yeah, people are like, oh, so you're an Aquarius. And I'm like, no, I'm a schnick cookie. Because Dr. Schnick Cookie was there influencing me.

• 2:56Speaker 01

  To catchy.

• 2:56Speaker 00

  At a physical level. Yeah. Not just the catchy, not just the physical touch, but the gravitational attraction to his mass.

• 3:02Speaker 01

  Right.

• 3:03Speaker 00

  We've been talking a lot about very like fundamental things in this really abstract way to just explain that things fall down. Because here on earth, they're attracted to the earth. And you were talking about how it's not just the earth pulling things in. Things pull the earth as well, but the earth is so much bigger than everything else we work with. That equal attraction they have affects other stuff, like a pen, a lot more than it does the earth. But I once calculated that if you dropped a pen from six feet up, it actually pulls the earth up towards it nine trillionths the width of a proton.

• 3:41Speaker 01

  Oh, which is, by my calculation, small.

• 3:46Speaker 00

  It's very small. So the, the, the pen falls the remainder of that distance, which is still pretty much six feet.

• 3:52Speaker 01

  But they are coming to meet each other.

• 3:54Speaker 00

  But they're coming to meet each other somewhere in between.

• 3:58Speaker 01

  Yeah.

• 3:58Speaker 00

  It just happens to be a much longer trip for the pen. And there, you've got both of those senses of mass happening together, the gravitational attraction, but then also that force moves each object with very different accelerations.

• 4:13Speaker 01

  I mean, that pen though, is particularly light. If you take an object that is heavier, denser, I mean heavier, actually, there's sort of an implication of, of gravity in that, in that statement itself, right? Uh, but, but if you take something that has, uh, more matter, the amount that the earth would move would change too.

• 4:31Speaker 00

  That's right. That's right. And so when people say a feather and a hammer dropped in a vacuum, so there's no air to move out of the way. They will fall at the same rate. They'll hit the ground at the same time.

• 4:44Speaker 01

  I tell you what, why don't we just clear up the question of what is gravity according to what different people thought at different times?

• 4:52Speaker 00

  Yeah.

• 4:53Speaker 01

  Because everything you're describing so far is essentially like a Newtonian view of gravity. So Newton has this idea that actually gravity is all about objects accelerating towards each other, right? You know, like forces, mass times acceleration was one of his, was one of his laws. And he was saying that we are accelerating towards the earth, which is the reason why when you chuck an apple, or any object, your baseball if you like, when you chuck it, it accelerates towards the earth and follows this curved path. And everyone for, you know, many hundreds of years was like, that guy Newton, he's, he's got it made. He's done it for us. That's perfect. But there were still some lingering questions, some little things that didn't quite make sense. So for instance, where

• 5:35Speaker 01

  is this, how is this force sort of acting? Like, let's say you took the sun and you had like a magic wand that made the sun disappear instantaneously. It would take eight, nine minutes for the light to hit us. But according to Newton's version of gravity, we would immediately stop accelerating towards the sun, which means that the earth should immediately spin off into the blackness of space. But that sort of doesn't really make any sense, right? Because isn't it that nothing can travel faster than the speed of light? So how can it be that we would feel the loss of the gravitational pull of the sun before the light switched out?

• 6:12Speaker 00

  Right. Yeah. And so we, we know for a fact today that gravity travels how fast?

• 6:17Speaker 01

  Speed of light.

• 6:18Speaker 00

  Speed of light, no faster.

• 6:19Speaker 01

  Well, it's the, the universal speed limit.

• 6:23Speaker 00

  Yeah, certainly. It's not instantaneous.

• 6:26Speaker 01

  Absolutely. Which means that if the sun suddenly vanished, we wouldn't know about it at all.

• 6:31Speaker 00

  But was that a problem for Newton?

• 6:33Speaker 01

  New to know, but as the time went on, people were like, there's something a bit fishy going on. Something a bit weird. I'm not sure. I'm not sure I like this. The other one that was a bit weird that people just couldn't quite work out is Mercury's orbit. The thing about Mercury, closest planet to the sun, it has this elliptical orbit. But that elliptical orbit is itself spinning around. It's affected by the other planets. So, so the, it doesn't trace out the same ellipse every single time it orbits the sun. That ellipse is moving around. It's called the perihelion of Mercury's orbit. Which sort of makes sense, right? Helion meaning sun. And everyone was cool with that. Everyone was absolutely fine with that, that they knew that, you know, this, that the orbit was going to change because of where different planets were.

• 7:14Speaker 01

  But when they ran the calculations, according to Newton's version of gravity, that it's essentially just objects accelerating towards each other. Something was off, right? It was like the number of arc seconds of Mercury's orbit, it just didn't totally make sense. And for a long time, you know, the telescopes weren't that accurate. People were like, maybe we've just made a miscalculation. It's sort of a bit, I don't know. And this was for a long time. Long time, hundreds of years. And then when Einstein came along and he was like, I think there's something else going on here. Einstein had this great intuition that it's not just that the objects are magically accelerating towards each other, but that spacetime itself has this curvature to it.

• 7:54Speaker 01

  So the sun, for instance, this giant gravitational force is literally bending and warping spacetime between us and it. And so if you got a magical wand and you made the sun disappear immediately, there would be this ripple that was sent out from the absence of that sun. Imagine taking a bowling ball on a rubber sheet and then removing it. That rubber sheet is going to kind of bounce up and down and ripple as you remove the weight. And that that ripple would reach us at the speed of light. He had this great intuition, worked out all the calculations for it. And the, one of the very first things that he turned his equations to was the perihelion of Mercury's orbit.

• 8:35Speaker 01

  To see if his new theory came up with a more accurate prediction than Newton's.

• 8:43Speaker 01

  He absolutely nailed it.

• 8:44Speaker 00

  Nailed it.

• 8:45Speaker 01

  Level of precision. I mean, he said that he was happy for days after he looked at those calculations was like, I've absolutely got it. I found the missing piece to the puzzle.

• 8:53Speaker 00

  So two things. First, that leap from there's a force acting on things. Maybe it's mediated by some particle or whatever. From to leap from there to actually, maybe gravity is just a change in the shape of spacetime.

• 9:12Speaker 01

  Mm hmm.

• 9:12Speaker 00

  Is really gigantic.

• 9:14Speaker 01

  Gigantic.

• 9:15Speaker 00

  Because spacetime is such a bizarrely abstract thing. It's, it's, it's the canvas that we are on. If we were two dimensional, this would be easier. We could say, you know, two dimensional creature could be painted onto this curtain. And if I crumple the curtain up, they're still stuck on it and they're going over all of these crinkles, but they don't even know it. I can bring them together and push them apart. If it gets crumpled up or curved, you're just going to follow along that curve. You cannot leave it. And so, yeah, Einstein is like, but what if it's the shape of the canvas that we are on?

• 9:49Speaker 01

  Exactly.

• 9:50Speaker 00

  Even the shape of time and how quickly time runs for you. If we allow that to change, then Mercury's orbit makes sense.

• 9:58Speaker 01

  Exactly right. It's the crumpling of the curtain. That's really, that's a really nice way to do it.

• 10:02Speaker 00

  Yeah, I think you need analogies because we're just talking about things that are so outside of our normal day to day activities.

• 10:09Speaker 01

  Totally.

• 10:10Speaker 00

  We understand forces. We understand pushes and pulls. But to say that space and time themselves push and pull, it's kind of more like you're just in them.

• 10:22Speaker 01

  But here's the thing, right? The implications of this idea that spacetime is like a crumpled curtain. It means that across the surface of the earth even, the gravitational effects are slightly different. So I did some calculations. Boulder in Colorado, right? Which of course is like a very high altitude compared to Greenwich in London, where I am. The gravitational effect in Boulder is 9.796 meters per second.

• 10:51Speaker 00

  And what is it in Greenwich?

• 10:53Speaker 01

  9.812.

• 10:55Speaker 00

  Wow.

• 10:55Speaker 01

  I've got higher gravitational effect than you.

• 10:57Speaker 00

  Yeah. Or so you are more attracted to the center of earth than I am in Boulder.

• 11:02Speaker 01

  Yep.

• 11:02Speaker 00

  Because I'm further away.

• 11:03Speaker 01

  Yep.

• 11:04Speaker 00

  And the inverse square law says.

• 11:06Speaker 01

  Exactly.

• 11:07Speaker 00

  That gravitational effect is, yeah, diminishes.

• 11:09Speaker 01

  Except that what that means, given Einstein's version of of gravity, is that the way that time changes in Boulder is different to the way that time changes in Greenwich, because the gravitation, what gravity is doing is it's bending and warping spacetime. So what this means is that time travels slower in Greenwich than it does in Boulder. And the difference is about 5.6 microseconds a year. So what I will say is that you are aging faster than me.