# What is gravity?

An episode of [Science for Kids / Science's Not Boring: The Kids Science Podcast](https://invisiblenetwork.ai/podcast/1896928296), 31 Jul 2026, 12 min.

Audio: https://www.buzzsprout.com/2624612/episodes/19542339-what-is-gravity.mp3

Have you ever wondered why an apple falls from a tree, but the Moon never crashes into Earth? Or why astronauts seem to float in space? (Hint: They aren't actually floating at all!) Join Mira and Finn on a mind-bending adventure to uncover the universe's greatest invisible force: gravity! Travel back in time to 1666 to sit under the exact tree where Isaac Newton figured out how Earth's invisible rope pulls things down. Then, discover the wildest secret of the International Space Station! Astronauts are actually falling towards Earth at an incredible 17,500 miles per hour, but they are moving so fast sideways that they keep missing the ground entirely! But wait, it gets even crazier! Learn how Albert Einstein proved that massive objects like the Sun can bend space and time like a giant heavy bowling ball on a trampoline, even curving beams of starlight! Find out why your feet are slightly younger than your head, how satellites use Einstein's math to keep your phone's GPS from driving you into a lake, and why the giant planet Jupiter acts like a cosmic pinball machine!

## Transcript

[0:46] SPEAKER_00: Welcome to Science is Not Boring by Kidopoly.com.
[0:50] SPEAKER_00: I'm Mira.
[0:52] SPEAKER_00: And I'm Finn.
[0:54] SPEAKER_00: So, Finn, have you ever seen videos of astronauts floating around inside the International Space Station?
[1:01] SPEAKER_01: Yeah, they drink floating blobs of water and do cool flips in the air.
[1:06] SPEAKER_01: There's zero gravity up there, right?
[1:09] SPEAKER_00: Actually, no.
[1:11] SPEAKER_00: The gravity up there is almost as strong as it is down here.
[1:15] SPEAKER_00: Those astronauts aren't floating at all.
[1:18] SPEAKER_00: They are constantly falling towards Earth while moving sideways at 17,500 miles per hour.
[1:25] SPEAKER_00: Wait, what?
[1:27] SPEAKER_00: Falling?
[1:28] SPEAKER_00: Why don't they crash into the ground?
[1:30] SPEAKER_00: That is exactly what we're going to find out today.
[1:34] SPEAKER_00: We're unpicking the most mysterious, invisible force that holds our entire universe together.
[1:41] SPEAKER_00: Gravity.
[1:42] SPEAKER_01: So we're talking about apples falling on heads and astronauts doing super fast space flips?
[1:48] SPEAKER_00: Yep, from Isaac Newton's famous apple tree in 1666, to why the moon never crashes into Earth, and even how gravity can actually bend a beam of starlight.
[2:00] SPEAKER_01: Okay, so what actually is gravity?
[2:03] SPEAKER_01: Like, if I drop my sandwich, it falls to the floor.
[2:06] SPEAKER_01: But why?
[2:08] SPEAKER_00: Gravity is an invisible pulling force.
[2:11] SPEAKER_00: Everything in the universe that has mass, meaning it's made of stuff, has gravity.
[2:16] SPEAKER_00: A tiny speck of dust has gravity.
[2:19] SPEAKER_00: A car has gravity, and a whole planet has gravity.
[2:23] SPEAKER_00: The bigger something is, the stronger its pull.
[2:27] SPEAKER_01: Wait, so my sandwich has gravity?
[2:29] SPEAKER_01: Am I pulling on my sandwich right now?
[2:33] SPEAKER_00: Yes.
[2:34] SPEAKER_00: Your sandwich is technically pulling on the earth, and you're pulling on your sandwich.
[2:39] SPEAKER_00: But the earth is just so incredibly huge that it wins the tug of war easily.
[2:45] SPEAKER_00: The earth pulls your sandwich down.
[2:47] SPEAKER_01: Okay, so who figured all this out?
[2:50] SPEAKER_01: Did people always know about this invisible rope?
[2:53] SPEAKER_00: People knew things fell, but they didn't understand the rules.
[2:57] SPEAKER_00: Let's travel back to the year 1666.
[3:01] SPEAKER_00: A 23-year-old scientist named Isaac Newton was staying at his family farm, Woolsthorpe Manor, in Lincolnshire, England.
[3:10] SPEAKER_00: Was this when the apple hit him on the head?
[3:12] SPEAKER_00: Well, he didn't actually get hit on the head, but he was sitting in the garden and watched an apple fall from a special tree called a flower of Kent.
[3:22] SPEAKER_00: He started wondering, why did the apple fall straight down to the centre of the earth?
[3:28] SPEAKER_00: Why not sideways or upwards?
[3:30] SPEAKER_01: Because the giant earth was pulling on the tiny apple.
[3:34] SPEAKER_00: Exactly! But then Newton looked up at the night sky and asked an even bigger question.
[3:40] SPEAKER_00: If Earth's gravity can reach the top of an apple tree, how far does it go?
[3:46] SPEAKER_00: Does it reach all the way to the moon?
[3:48] SPEAKER_01: Wait, if Earth's gravity reaches the moon, why doesn't the moon crash into us like the apple?
[3:54] SPEAKER_00: That was Newton's genius moment.
[3:56] SPEAKER_00: He realised the moon is falling towards Earth constantly, but it's also moving sideways extremely fast.
[4:03] SPEAKER_00: Falling but missing?
[4:05] SPEAKER_00: How does that work?
[4:06] SPEAKER_00: Imagine throwing a baseball super fast.
[4:09] SPEAKER_00: It goes forward, then curves down and hits the ground.
[4:13] SPEAKER_00: Now imagine throwing it so incredibly fast that by the time it curves down, the round surface of the Earth has actually curved away beneath it.
[4:22] SPEAKER_01: So it keeps falling, but the ground keeps dodging out of the way?
[4:27] SPEAKER_00: Yes, that is exactly what an orbit is.
[4:30] SPEAKER_00: The Moon is an average of 238,855 miles away from us.
[4:36] SPEAKER_00: It is moving sideways so incredibly fast that it basically falls around the Earth in a giant, never-ending circle.
[4:44] SPEAKER_01: That is wild! Is that what the astronauts are doing on the space station?
[4:49] SPEAKER_00: Exactly! The International Space Station is orbiting about 250 miles up in the sky.
[4:56] SPEAKER_00: To keep from crashing back down to Earth, it zooms sideways at 17,500 miles per hour.
[5:03] SPEAKER_01: 17,500 miles per hour?
[5:07] SPEAKER_01: That's ridiculously fast.
[5:09] SPEAKER_00: How long does it take to go around the world?
[5:12] SPEAKER_00: It takes them just 90 minutes to orbit the entire planet.
[5:16] SPEAKER_00: Because they are constantly falling, they experience microgravity, which makes them feel totally weightless.
[5:23] SPEAKER_00: Imagine that tummy dropping feeling you get on a roller coaster when you go down a steep hill, but it lasts forever.
[5:30] SPEAKER_01: Ew, I think I'd throw up if my tummy dropped forever.
[5:34] SPEAKER_01: So they aren't floating in zero gravity, they are just in a giant, super fast freefall.
[5:40] SPEAKER_00: You got it, and the same rules keep the Earth orbiting the Sun.
[5:44] SPEAKER_00: We are moving sideways at 67,000 miles per hour, falling around the Sun year after year.
[5:50] SPEAKER_00: For over 200 years, everyone thought Newton solved gravity perfectly.
[5:56] SPEAKER_00: But then, in 1915, a scientist named Albert Einstein came along and completely changed the game.
[6:04] SPEAKER_00: What did Einstein do?
[6:06] SPEAKER_00: Einstein said gravity isn't just an invisible rope pulling things.
[6:11] SPEAKER_00: He said that massive objects actually bend space and time itself.
[6:17] SPEAKER_00: Imagine a heavy bowling ball sitting in the middle of a big trampoline.
[6:21] SPEAKER_01: Okay, the trampoline would sag down deep in the middle.
[6:25] SPEAKER_00: Right, and if you roll a marble across that trampoline, it curves down into the dip.
[6:31] SPEAKER_00: Einstein said planets and stars do that to space.
[6:35] SPEAKER_00: He even predicted gravity is so strong it could bend a beam of light.
[6:40] SPEAKER_00: Wait, light doesn't weigh anything, it doesn't have mass.
[6:43] SPEAKER_01: How can gravity pull on it?
[6:45] SPEAKER_00: That was the big question.
[6:47] SPEAKER_00: To prove it, a British astronomer named Arthur Eddington organised a famous expedition in 1919.
[6:56] SPEAKER_00: He packed up his telescopes and travelled to an island off the coast of Africa called Principe.
[7:02] SPEAKER_01: Why did he have to go all the way to an island in Africa?
[7:05] SPEAKER_00: Because he needed to watch a total solar eclipse.
[7:09] SPEAKER_00: Normally, the sun is so bright you can't see the stars behind it.
[7:14] SPEAKER_00: But during the eclipse, the moon blocked out the sun, turning day into night for just a few minutes.
[7:21] SPEAKER_00: Oh, that's so smart!
[7:23] SPEAKER_01: So he took pictures of the stars right next to the sun.
[7:26] SPEAKER_00: Yes.
[7:27] SPEAKER_00: Einstein predicted a shift of exactly 1.75 arc seconds, and Eddington's measurements were close enough to prove he was right.
[7:37] SPEAKER_00: It's a tiny shift, but it proved the sun's massive gravity bent starlight like a magnifying glass.
[7:44] SPEAKER_01: No way! So the trampoline dip around the sun forced the light rays to take a curved path.
[7:50] SPEAKER_00: Exactly! Einstein was right.
[7:53] SPEAKER_00: Space itself is curved by gravity.
[7:56] SPEAKER_00: And it made him a worldwide celebrity overnight.
[8:00] SPEAKER_01: That is seriously mind-blowing.
[8:02] SPEAKER_01: But does any of this space-spending time-travelling stuff actually affect us down here on Earth?
[8:08] SPEAKER_00: Oh, it absolutely does.
[8:10] SPEAKER_00: Think about the GPS mapping on your phone or in a car.
[8:13] SPEAKER_00: That system relies on a network of satellites orbiting the Earth, 12,000 miles up in space.
[8:20] SPEAKER_00: And because they're up in space, time is weird for them.
[8:23] SPEAKER_00: Right.
[8:24] SPEAKER_00: Because gravity is slightly weaker up there, time actually ticks faster by 45 microseconds a day.
[8:32] SPEAKER_00: But their fast speed slows it down by 7 microseconds.
[8:36] SPEAKER_00: It leaves a 38 microsecond difference.
[8:39] SPEAKER_00: And if scientists didn't use Einstein's math to fix those clocks constantly, your GPS would drift by miles every single day.
[8:48] SPEAKER_01: You'd end up driving into a lake just trying to find the grocery store.
[8:52] SPEAKER_00: Exactly.
[8:54] SPEAKER_00: And here's another weird fact.
[8:56] SPEAKER_00: Because gravity is stronger the closer you get to the centre of the Earth, your feet are aging ever so slightly slower than your head.
[9:04] SPEAKER_01: My feet are time travellers.
[9:05] SPEAKER_01: I knew it.
[9:06] SPEAKER_01: They are practically babies compared to my brain.
[9:09] SPEAKER_00: Well, we're talking about tiny fractions of a second over your whole life, but yes.
[9:15] SPEAKER_00: And gravity also throws things around.
[9:18] SPEAKER_00: Our solar system's largest planet, Jupiter, is so massive that its gravity is 2.5 times stronger than Earth's.
[9:26] SPEAKER_01: Does it act like a giant cosmic vacuum cleaner?
[9:29] SPEAKER_00: It's actually more like a pinball machine.
[9:32] SPEAKER_00: Jupiter's gravity pulls some in, but it also flings many dangerous asteroids and comets right toward the inner solar system where Earth is.
[9:41] SPEAKER_01: Wow, I guess Jupiter is a bit unpredictable.
[9:44] SPEAKER_01: I'm really glad I'm down here where my feet belong, even if they are slightly younger than my head.
[9:49] SPEAKER_00: Alright, Finn, time for the quiz.
[9:51] SPEAKER_00: Are you ready?
[9:52] SPEAKER_00: Okay, I'm ready.
[9:54] SPEAKER_00: Okay, first question.
[9:56] SPEAKER_00: What specific kind of apple tree did Isaac Newton see the apple fall from?
[10:04] SPEAKER_00: Next one.
[10:06] SPEAKER_00: On average, how many miles away is the moon from Earth?
[10:13] SPEAKER_00: Question three.
[10:14] SPEAKER_00: How fast does the International Space Station travel to stay in orbit?
[10:22] SPEAKER_00: Here's number four.
[10:24] SPEAKER_00: Who proved that gravity can bend light during a 1919 solar eclipse?
[10:33] SPEAKER_00: Last question.
[10:35] SPEAKER_00: What massive planet acts like a cosmic pinball machine with asteroids?
[10:43] SPEAKER_00: Great job! Let's see how you did.
[10:46] SPEAKER_00: The answer to question one is it was a flower of Kent, Apple Tree, at Woolsthorpe Manor.
[10:53] SPEAKER_00: For question two, the Moon is an average of 238,855 miles away.
[11:02] SPEAKER_00: The answer is the ISS travels at a super fast 17,500 miles per hour.
[11:11] SPEAKER_00: Question four.
[11:13] SPEAKER_00: The British astronomer was Arthur Eddington.
[11:16] SPEAKER_00: And the final answer is Jupiter.
[11:19] SPEAKER_00: So Finn, what's your favourite thing we learned today?
[11:22] SPEAKER_01: Definitely the fact that astronauts aren't floating.
[11:25] SPEAKER_01: They're just falling constantly and missing the ground.
[11:28] SPEAKER_01: That is the coolest thing ever.
[11:30] SPEAKER_00: It really is.
[11:32] SPEAKER_00: It totally changes how you look at the night sky.
[11:35] SPEAKER_00: And hey, to our listeners, if you loved learning about gravity and falling moons today, please leave us a five-star review.
[11:42] SPEAKER_00: Just scroll down in your podcast app and tap those stars.
[11:46] SPEAKER_01: Yeah, give us five stars.
[11:48] SPEAKER_01: Unless you're falling at 17,500 miles an hour right now, then maybe wait until you safely land.
[11:55] SPEAKER_00: Oh, and don't forget to check out our site kidopoly.com.
[11:58] SPEAKER_00: We've got tons of fun learning games and activities there.
[12:02] SPEAKER_01: And if you want a shout out on the show, or just want to say hi, email us at hello at kidopoly.com.
[12:09] SPEAKER_00: See you next time on Science is not boring.
[12:12] SPEAKER_00: Bye!

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