Introducing: The Rest Is Science

Summary

Podcast Summary: The Rest Is Classified

Episode: Introducing: The Rest Is Science
Hosts: Michael Stevens & Professor Hannah Fry (guest hosts)
Release Date: December 11, 2025
Podcast Network: Goalhanger

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Overview:

This special episode introduces "The Rest Is Science," a new show by Michael Stevens and Professor Hannah Fry. Picking up the mic from "The Rest Is Classified," they promise to dissect familiar phenomena and challenge everyday assumptions, with curiosity fueling explorations into the underlying science. The preview episode delves into the concept of gravity—how it’s defined, perceived, and understood from Newton to Einstein, unpacking the evolution of our understanding through analogies, calculations, and playful banter.

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Key Discussion Points & Insights

1. Curiosity as the Engine of Science

• Michael and Hannah open by setting their show’s intent: to question even the basics we take for granted and expose the surprising science beneath everyday experiences.
  • "That's what moves science forward. Not the polishing of answers, but the sharpening of questions." – Michael [00:51]
• They invite listeners to join the journey every Tuesday and Thursday to confront and decipher scientific mysteries together.

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2. How Would You Explain Gravity to an Alien?

• Prompt: Michael poses, "How would you describe gravity to an alien from another universe that had never experienced gravity?" [01:17]

• Hannah’s answer: It’s a universal attraction between objects with mass—objects simply come together if unimpeded.

  • "Anything with mass ... we sort of imagine gravity as though it's like the Earth is pulling us down. But ... we're also pulling the Earth up." – Hannah [01:47]

• Michael's illustration: Even two baseballs in deep space would eventually move toward one another solely due to gravity, albeit over days.

  • "I once calculated that two baseballs placed in intergalactic space a meter apart would ... collapse in towards each other until they touched ... because of their gravitational attraction." – Michael [02:06]

• Playful debunking of astrology:

  • Astrology’s celestial influence is dwarfed by the basic gravitational interaction with a nearby human.
    • "The gravitational influence of Pisces on you is less than the gravitational influence of the doctor who delivered you on you." – Michael [02:49]

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3. Gravitational Attraction Works Both Ways

• Key idea: Every object exerts gravitational pull—not just the bigger ones.
  • Even a dropped pen technically pulls the Earth upward, though by an unimaginably tiny amount.
  • "If you dropped a pen from six feet up, it actually pulls the Earth up towards it. 9 trillionths the width of a proton." – Michael [03:20]

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4. Newton vs. Einstein: Evolving Views on Gravity

Newtonian Gravity:

• Newton posited gravity as a force accelerating objects toward one another. The famous “force equals mass times acceleration” rule.
  • "Everything you're describing so far is essentially like a Newtonian view of gravity ... objects accelerating towards each other." – Hannah [05:01]
• Problems with Newton’s model:
  • Immediate gravitational effects don’t consider the speed-of-light limit
  • Mercury's orbit (“precession of the perihelion”) didn’t fully fit the equations.

Einstein’s General Relativity:

• Einstein reimagined gravity as curvature in the fabric of spacetime, not a force but a consequence of objects warping this fabric.
  • "Maybe gravity is just a change in the shape of space. Time is really gigantic, gigantic." – Michael [09:10]
  • "If you got a magical wand and you made the sun disappear immediately ... there would be this ripple that was sent out ... at the speed of light." – Hannah [07:56]
• The “crumpled curtain” analogy:
  • Mass bends space and time—just as a bowling ball stretches a rubber sheet—and objects move along this curvature.

Einstein’s model explained Mercury’s orbit precisely: - "He absolutely nailed it ... he was happy for days after he looked at those calculations." – Hannah [08:34]

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5. Everyday Consequences of Curved Spacetime

• Gravity isn’t constant everywhere on Earth—it's affected by altitude.

  • "Boulder in Colorado ... 9.796 meters per second. Greenwich ... 9.812." – Hannah [11:08]
  • Meaning: In Boulder, you’re less attracted to the Earth's center than in Greenwich due to the inverse square law.

• Time runs differently:

  • Gravity’s warping of spacetime affects the passage of time.
  • "Time travels slower in Greenwich than it does in Boulder ... about 5.6 microseconds a year. So ... you are aging faster than me." – Hannah [11:26]

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Notable Quotes & Memorable Moments

• "We are gravitationally attracted to each other right now. It cannot overcome the air ... but yet we are attracted." – Michael [02:12]

• "People are like, oh, so you're an Aquarius? And I'm like, no, I'm a schnit cookie. Because Dr. Schnitcookie was there, influencing me to catch you at a physical level." – Michael [03:04]

• "If you take something that has more matter, the amount that the Earth would move would change too." – Hannah [04:30]

• "If the sun suddenly vanished, we wouldn't know about it at all [immediately]." – Michael [06:48]

• "It's the crumpling of the curtain. That's a really nice way to do it." – Hannah [10:16]

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Timestamps for Key Segments

• [00:51] – The philosophy of science and curiosity
• [01:17] – Gravity explained for an alien
• [02:06] – Gravity’s effect on everyday objects and cosmic ones
• [03:20] – A pen’s pull on the Earth: scale of gravitational forces
• [05:01] – Newton's laws and their limitations
• [07:56] – Einstein's insight and Mercury's mysterious orbit
• [09:10] – Curved spacetime and analogies ("crumpled curtain")
• [11:08] – Altitude, gravity variation, and time dilation

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Tone & Language

The dialogue is accessible, playful, and filled with relatable analogies, making profound physics approachable and engaging for general listeners.

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For Listeners Who Missed the Episode:

This energetic preview gives you a taste of what "The Rest Is Science" promises: deep explorations of everyday science, friendly banter, and a knack for unraveling the world's workings—starting with how and why gravity, from apple falls to Mercury’s orbit, shapes our universe (and even the way we age).

Transcript

[A]

For exclusive interviews, bonus episodes, ad free listening, early access to series first look at live show tickets, a weekly newsletter and discounted books. Join the Declassified [e-mail]. hello, the rest is classified listeners. I'm Michael Stevens.

[B]

And I'm Professor Hannah Fry. Well, firstly, thank you to David and Gordon for letting us take over the channel. We are here to tell you about our new show for goal hang 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.

[A]

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.

[B]

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 of Science and we'll figure it out together.

[A]

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

[B]

The simplest way to think of it is that in our universe, objects are attracted to each other. And if you. Without any. 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.

[A]

And at this point, the alien goes, what? That is so odd, Right? And what do you mean by an object?

[B]

Anything with mass. Anything with mass. Because I think that we. 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.

[A]

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 zodiac constellation that's Like, I don't know, how does astrology work?

[B]

Something, something, something. Pisces, Right?

[A]

Okay. So, okay, 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.

[B]

Because otherwise birth ain't working.

[A]

That's why. Yeah. People are like, oh, so you're an Aquarius? And I'm like, no, I'm a schnit cookie. Because Dr. Schnitcookie was there, influencing me to catch you at a physical level. Yeah. Not just the catchy. Not just the physical touch, but the gravitational attraction to his mass.

[B]

Right.

[A]

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. 9 trillionths the width of a proton. Oh.

[B]

Which is, by my calculation, small.

[A]

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

[B]

But they are coming to meet each other.

[A]

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

[B]

Yeah.

[A]

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.

[B]

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 gravity in that. In that statement itself. Right. But if you take something that has more matter, the amount that the Earth would move would change too.

[A]

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.

[B]

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? 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 force is 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 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 8, 9 minutes for the light to hit us. But according to Newton's version of gravity, we, 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?

[A]

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

[B]

Speed of light.

[A]

Speed of light? No, faster.

[B]

Well, because it's the universal speed limit.

[A]

Yeah. Certainly it's not instantaneous.

[B]

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

[A]

But was that a problem for Newton?

[B]

Newton, no. 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 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 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 the orbit was going to change because of where different planets were. But when they ran the calculations according to Newton's version of gravity, that it's essentially just accelerate objects accelerating towards each other, something was off Right. It was like the number of arc seconds of Mercury's orbit 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.

[A]

And this was for a long time.

[B]

Long.

[A]

Hundreds of years.

[B]

Hundreds of years. And then when Einstein came along and he was like, I think there's something else going on here. Einstein has this great intuition that it's not just that objects are magically accelerating towards each other, but that space time itself has this curvature to it. So the sun, for instance, this giant gravitational force, is literally bending and warping space time between us and it. And so if you got a magical wand and you made the sun disappear immediately, you, 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. Had this great intuition worked out all the calculations for it. And one of the very first things that he turned his equations to was the prohelion of Mercury's orbit to see if his new theory came up with a more accurate prediction than Newton's. And he absolutely nailed it, like 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.

[A]

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 space. Time is really gigantic, gigantic. Because space time is such a bizarrely abstract thing. It's the canvas that we are on. If we were two dimensional, this would be easier. We could say a 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 and. 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 gonna 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?

[B]

Exactly.

[A]

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

[B]

Exactly.

[A]

Right.

[B]

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

[A]

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

[B]

Totally.

[A]

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.

[B]

But here's the thing, right. The implications of this idea that space time 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.

[A]

And what is it in Greenwich?

[B]

9.812.

[A]

Wow.

[B]

I've got higher gravitational effect than you. Yeah.

[A]

So you are more attracted to the center of Earth than I am in Boulder because I'm further away. Yep. And the inverse square law says.

[B]

Exactly further away.

[A]

Gravitational effect. Yeah. Diminishes.

[B]

Except that what that means, given Einstein's version of gravity, is that the way that time changes in Boulder is different to the way that time changes in Greenwich because what gravity's 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.