# Why does the Moon change shape?

An episode of [Science for Kids / Science's Not Boring: The Kids Science Podcast](https://invisiblenetwork.ai/podcast/1896928296), 20 Jul 2026, 14 min.

Audio: https://www.buzzsprout.com/2624612/episodes/19491894-why-does-the-moon-change-shape.mp3

Have you ever looked up at the night sky and wondered why the Moon changes shape? Sometimes it's a huge, glowing round ball, and other times it is just a tiny sliver that looks exactly like a banana! Join Mira and Finn on an epic space adventure to uncover the amazing secrets of our closest neighbor in space. Did you know the Moon is so incredibly far away that you could fit every single planet in our solar system right between it and Earth? Even giant Jupiter! Discover the astonishing truth about the famous "Man in the Moon" (hint: he is actually made of ancient, frozen lava from violent asteroid crashes billions of years ago!). You will also find out why the Moon gets boiling hot during the day and mind-blowingly freezing cold at night, and where top NASA scientists have found real water ice hidden deep inside dark craters! Plus, learn the shocking reason why the Moon is slowly sneaking away from Earth every year at the exact same speed your fingernails grow. Blast off into astronomy and get ready to have your mind blown!

## Transcript

[0:46] SPEAKER_00: Welcome to Science Is Not Boring by Kidopoly.com.
[0:49] SPEAKER_00: I'm Mira.
[0:50] SPEAKER_00: And I'm Finn.
[0:51] SPEAKER_00: Look up at the night sky, Finn.
[0:53] SPEAKER_01: Have you ever wondered what's really up there on the Moon?
[0:56] SPEAKER_01: I always try to spot the face in the Moon.
[0:59] SPEAKER_01: Sometimes it looks like a whole man looking down at us.
[1:03] SPEAKER_00: Well, get ready to have your mind blown, because today we are exploring our closest neighbour in space.
[1:10] SPEAKER_00: The Moon! Exactly! But before we blast off, I have a shocking fact for you.
[1:16] SPEAKER_00: Finn, how far away do you think the moon is?
[1:18] SPEAKER_01: Um really far?
[1:21] SPEAKER_01: Like a million miles?
[1:23] SPEAKER_01: I know it takes a rocket a few days to get there.
[1:25] SPEAKER_00: It's actually an average of 238,855 miles away.
[1:32] SPEAKER_00: Or 384,400 kilometres.
[1:36] SPEAKER_01: That is super far.
[1:38] SPEAKER_01: That's like driving across the whole United States almost a hundred times.
[1:43] SPEAKER_00: Exactly! It is so far, Finn, that you could take every single other planet in our solar system.
[1:50] SPEAKER_01: Wait, all of them?
[1:52] SPEAKER_01: Jupiter, Saturn?
[1:54] SPEAKER_00: Yes! Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune.
[2:00] SPEAKER_00: You could line them all up side by side, squished atmosphere to atmosphere.
[2:04] SPEAKER_01: Even Jupiter?
[2:06] SPEAKER_01: Jupiter is massive! You could fit over a thousand Earths inside Jupiter.
[2:11] SPEAKER_00: Haha, yes, even Jupiter.
[2:14] SPEAKER_00: You could fit the four gas giants and the rocky planets right between Earth and the Moon, with a little space to spare.
[2:21] SPEAKER_01: No way.
[2:22] SPEAKER_01: You could fit all the planets between us and the Moon.
[2:25] SPEAKER_01: My brain can't even picture that much empty space.
[2:28] SPEAKER_00: It's completely true.
[2:30] SPEAKER_00: The distance is huge, and today we are going to find out why the moon changes shape, what those dark spots actually are, and if anyone could ever live there.
[2:39] SPEAKER_01: Okay, so first things first, why does the moon change shape?
[2:44] SPEAKER_01: Sometimes it's a huge glowing ball, and sometimes it's just a tiny sliver that looks like a banana.
[2:51] SPEAKER_00: That's called the lunar cycle, and the secret is the moon doesn't actually change shape at all.
[2:57] SPEAKER_00: It's always a big, solid, heavy ball of rock orbiting around us.
[3:01] SPEAKER_01: Then why does it look like somebody took a huge bite out of it half the time?
[3:06] SPEAKER_00: Because the moon doesn't make its own light.
[3:09] SPEAKER_00: It doesn't have fire or giant light bulbs.
[3:12] SPEAKER_00: It's basically a giant mirror in the sky, reflecting light from the sun.
[3:16] SPEAKER_00: Oh, so the bright part is just daytime on the moon.
[3:20] SPEAKER_00: Exactly! As the moon travels around the Earth, the Sun hits it from different angles.
[3:26] SPEAKER_00: It takes about 29.5 days to complete one full cycle of phases.
[3:31] SPEAKER_01: So when we see a full moon, the sun is shining right directly on the front of it.
[3:36] SPEAKER_00: You got it! And when it's a new moon, the moon is between Earth and the Sun.
[3:41] SPEAKER_00: That means the sun is shining entirely on the back of it.
[3:45] SPEAKER_01: So the side facing us gets zero sunlight and looks completely dark.
[3:50] SPEAKER_01: That's right!
[3:51] SPEAKER_00: But wait, notice how you said the side facing us.
[3:55] SPEAKER_00: Does the moon ever show us its back?
[3:58] SPEAKER_00: Don't we see the whole thing as it spins around?
[4:00] SPEAKER_00: Never! It's locked in what scientists call synchronous rotation.
[4:05] SPEAKER_00: It spins on its axis at the exact same speed it travels around Earth.
[4:10] SPEAKER_00: So there's a whole side of the moon we never get to see from our backyard telescope.
[4:14] SPEAKER_00: Yep, the mysterious far side of the moon.
[4:18] SPEAKER_00: But let's talk about the front side.
[4:20] SPEAKER_00: What are those big dark spots we always see?
[4:22] SPEAKER_01: The man in the moon! Or sometimes I think it looks like a rabbit playing a drum.
[4:29] SPEAKER_00: That's a fun way to look at it.
[4:31] SPEAKER_00: Many early astronomers looked through their first telescopes and thought those dark patches were giant oceans.
[4:38] SPEAKER_01: Wait, they thought there was a real ocean up there, like with water and waves.
[4:44] SPEAKER_01: They did!
[4:45] SPEAKER_00: They even gave them water names.
[4:47] SPEAKER_00: They called them Maria, which is the Latin word for seas.
[4:51] SPEAKER_01: So what is the man in the moon actually made of if it's not a real sea of water?
[4:56] SPEAKER_00: Well, billions of years ago, around 3.9 billion years to be exact, our solar system was a very chaotic, violent place.
[5:06] SPEAKER_01: Uh-oh.
[5:06] SPEAKER_01: Violent how?
[5:08] SPEAKER_01: Like planets crashing into each other.
[5:10] SPEAKER_00: Exactly! Giant space rocks, comets, and massive asteroids slammed right into the moon.
[5:17] SPEAKER_00: They created massive craters called impact basins.
[5:22] SPEAKER_01: Were they huge?
[5:23] SPEAKER_01: Like the size of a city?
[5:25] SPEAKER_00: Way bigger! These basins were more than 186 miles wide.
[5:31] SPEAKER_00: Some were big enough to swallow entire countries.
[5:34] SPEAKER_01: But how did deep crater holes turn into those big, flat, dark spots we see today?
[5:39] SPEAKER_00: Because the crashes were so incredibly powerful, they cracked the moon's crust.
[5:45] SPEAKER_00: And deep down underneath, the moon still had hot, bubbling magma.
[5:50] SPEAKER_00: Oh, so the moon had active volcanoes back then?
[5:53] SPEAKER_00: Basically, yes.
[5:55] SPEAKER_00: The magma seeped up through those deep cracks and completely flooded those giant craters with dark, runny lava.
[6:04] SPEAKER_01: Whoa! So the seas are actually giant pools of cooled lava.
[6:08] SPEAKER_00: Yep.
[6:09] SPEAKER_00: The lava cooled into a dark, heavy rock called basalt.
[6:13] SPEAKER_00: When you look at the man in the moon, you're looking at ancient lava flows that froze in place billions of years ago.
[6:21] SPEAKER_01: That is so much cooler than an ocean.
[6:23] SPEAKER_01: The man in the moon is made of frozen lava.
[6:26] SPEAKER_00: One of the most famous Maria is called the Sea of Tranquility.
[6:30] SPEAKER_00: On July 20th, 1969, astronauts Neil Armstrong and Buzz Aldrin landed the Apollo 11 spacecraft right in the middle of it.
[6:41] SPEAKER_01: That's right.
[6:42] SPEAKER_01: They were the first people to walk on the moon.
[6:45] SPEAKER_01: But what was it actually like there?
[6:48] SPEAKER_01: Was it super hot because of all that old lava?
[6:52] SPEAKER_00: Well, the lava cooled down billions of years ago, so the rock itself isn't generating heat anymore.
[6:58] SPEAKER_00: But the temperature up there is totally wild.
[7:02] SPEAKER_01: Wild how?
[7:03] SPEAKER_01: Like, need a winter coat wild or need a fan wild?
[7:08] SPEAKER_00: Both! Because the moon has almost zero atmosphere, there's no blanket of air to trap heat or block the harsh rays of the sun like we have on Earth.
[7:18] SPEAKER_00: So when the sun is shining directly on it, how hot does it get?
[7:23] SPEAKER_00: During the lunar daytime at the equator, the temperature hits a boiling 250 degrees Fahrenheit.
[7:31] SPEAKER_00: That's 120 degrees Celsius.
[7:35] SPEAKER_01: 250 degrees?
[7:37] SPEAKER_01: You would literally cook.
[7:39] SPEAKER_01: Water boils at 212 degrees on Earth.
[7:43] SPEAKER_00: I know! You definitely wouldn't want to take off your spacesuit.
[7:47] SPEAKER_00: But the moment the sun sets, there's no air to hold on to that heat.
[7:51] SPEAKER_00: Does it get really cold?
[7:53] SPEAKER_01: Like an ice cube?
[7:54] SPEAKER_00: Way colder! It plunges down to minus 208 degrees Fahrenheit.
[8:01] SPEAKER_00: That's minus 133 degrees Celsius.
[8:06] SPEAKER_01: Minus 208?
[8:08] SPEAKER_01: That's way colder than Antarctica.
[8:10] SPEAKER_00: And it gets even crazier.
[8:12] SPEAKER_00: At the north and south poles of the Moon, there are deep craters where sunlight never ever reaches.
[8:19] SPEAKER_00: Never?
[8:21] SPEAKER_00: Not for millions of years.
[8:23] SPEAKER_00: Never.
[8:24] SPEAKER_00: Scientists using NASA's Lunar Reconnaissance Orbiter measured the temperature in those dark craters.
[8:30] SPEAKER_00: They drop to an unbelievable minus 424 degrees Fahrenheit, or minus 253 Celsius.
[8:41] SPEAKER_01: That's almost as cold as space can possibly get.
[8:44] SPEAKER_01: Wait, if it's that incredibly cold in those dark craters, does that mean there's ice hidden in there?
[8:51] SPEAKER_00: Thin, you are thinking exactly like a top NASA scientist right now.
[8:55] SPEAKER_00: Really?
[8:56] SPEAKER_00: Did they actually find ice?
[8:58] SPEAKER_00: They did.
[8:59] SPEAKER_00: Satellites and probes discovered patches of real water ice hidden deep in the shadows of those polar craters.
[9:07] SPEAKER_01: Water ice on the moon!
[9:09] SPEAKER_00: That means if astronauts go back, they could use it, right?
[9:13] SPEAKER_00: Exactly! NASA's incredible Artemis program is planning to send the next generation of astronauts back to the Moon.
[9:21] SPEAKER_00: And they specifically want to explore the South Pole just for that ice.
[9:26] SPEAKER_01: They could melt it to drink, or use it to water plants in a moon base, or even make rocket fuel.
[9:32] SPEAKER_00: Yes! Splitting water into hydrogen and oxygen makes amazing rocket fuel.
[9:38] SPEAKER_00: It's going to be a huge stepping stone for humanity.
[9:42] SPEAKER_00: But the moon is actually doing something else weird right now.
[9:46] SPEAKER_01: Uh-oh.
[9:47] SPEAKER_01: Is it shrinking?
[9:48] SPEAKER_00: Is it falling toward us?
[9:50] SPEAKER_00: Don't panic.
[9:52] SPEAKER_01: It's actually moving away from us.
[9:54] SPEAKER_01: The moon is running away.
[9:56] SPEAKER_01: How do we even know that?
[9:58] SPEAKER_01: We can't use a tape measure from Earth to space.
[10:01] SPEAKER_00: No tape measure needed.
[10:03] SPEAKER_00: When the Apollo astronauts visited, they left special little mirrors on the surface.
[10:09] SPEAKER_00: Scientists on Earth shoot laser beams at those mirrors.
[10:13] SPEAKER_01: Whoa, they shoot space lasers at the Moon?
[10:16] SPEAKER_00: Yep.
[10:17] SPEAKER_00: By timing exactly how many seconds the laser takes to bounce back, they can measure the exact distance down to the millimetre.
[10:26] SPEAKER_00: And what did the lasers show?
[10:28] SPEAKER_00: How fast is it running away?
[10:30] SPEAKER_00: The moon is drifting away from Earth at a speed of 3.8 cm per year.
[10:36] SPEAKER_00: 3.8 centimetres?
[10:38] SPEAKER_01: Wait, that's like an inch and a half.
[10:41] SPEAKER_01: That's about the same speed our fingernails grow.
[10:44] SPEAKER_00: That's a perfect comparison.
[10:46] SPEAKER_00: So every single year the moon gets just a tiny bit further away as its orbit slowly gets bigger.
[10:54] SPEAKER_01: I will never look at the moon the same way again.
[10:57] SPEAKER_01: It's a freezing, boiling rock made of dark lava that's slowly sneaking away from us like a growing fingernail.
[11:05] SPEAKER_00: Science is absolutely amazing, isn't it?
[11:08] SPEAKER_00: It completely changes how we see the night sky.
[11:12] SPEAKER_00: Alright, Finn, time for the quiz! Are you ready?
[11:15] SPEAKER_01: Okay, I'm ready.
[11:17] SPEAKER_01: Hit me with the moon fact.
[11:19] SPEAKER_00: First question, how many days does the full lunar cycle take?
[11:27] SPEAKER_00: Next one, what is the real name for the dark patches on the moon?
[11:35] SPEAKER_00: Question three.
[11:36] SPEAKER_00: What kind of cooled rock are those dark patches actually made of?
[11:44] SPEAKER_00: Here's number four.
[11:46] SPEAKER_00: How hot can the moon get during the daytime in Fahrenheit or Celsius?
[11:54] SPEAKER_00: Last question.
[11:56] SPEAKER_00: How fast is the moon moving away from Earth every year?
[12:03] SPEAKER_00: Great job! Let's see how you did.
[12:06] SPEAKER_00: The first answer is the lunar cycle takes about 29.5 days.
[12:12] SPEAKER_00: For question two, the dark patches are called the lunar Maria, or just Maria.
[12:18] SPEAKER_00: The answer to number three, they are made of a dark volcanic rock called basalt, which is cooled lava.
[12:26] SPEAKER_00: For question four, it hits a boiling 250 degrees Fahrenheit, or 120 degrees Celsius.
[12:35] SPEAKER_00: And the final answer: the Moon is moving away at 3.8 centimetres per year, about the speed your fingernails grow.
[12:44] SPEAKER_01: Wow, I got most of those.
[12:46] SPEAKER_01: But I'm still stuck on the fact that all the planets could fit right between us and the moon.
[12:52] SPEAKER_01: I know.
[12:53] SPEAKER_01: The scale of space is totally mind-blowing.
[12:57] SPEAKER_01: Next time I see a full moon, I'm going to tell everyone it's a giant ball of frozen lava.
[13:03] SPEAKER_01: Do it!
[13:04] SPEAKER_00: Hey listeners, if you love learning about our amazing moon today, please leave us a five-star review.
[13:10] SPEAKER_01: Yeah, just scroll down on your podcast app and tap those five stars.
[13:15] SPEAKER_01: It helps other science explorers find us.
[13:18] SPEAKER_00: Oh, and don't forget to check out our site, kidopoly.com.
[13:22] SPEAKER_00: We've got tons of fun learning games and activities there to explore.
[13:26] SPEAKER_01: And if you want a shout out on the show, or just want to say hi, send us an email at hello at kidopoly.com.
[13:33] SPEAKER_00: Thanks for exploring the solar system with us today.
[13:36] SPEAKER_00: Keep looking up at the stars.
[13:38] SPEAKER_00: See you next time on Science Is Not Boring.
[13:42] SPEAKER_00: Bye.

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