# What is the universe?

An episode of [Science for Kids / Science's Not Boring: The Kids Science Podcast](https://invisiblenetwork.ai/podcast/1896928296), 6 Aug 2026, 12 min.

Audio: https://www.buzzsprout.com/2624612/episodes/19574168-what-is-the-universe.mp3

Have you ever looked up at the night sky and wondered, just how big is space? Does it ever end? Get ready for a mind-bending cosmic adventure with Mira and Finn! We are blasting off to discover the unbelievable size of the universe. Did you know that even in our fastest spaceship, it would take 73,000 years to reach the absolute nearest star, Proxima Centauri? That is longer than all of recorded human history! Join us as we explore what a "light-year" really is and learn how looking deep into space is actually a real-life form of time travel! We will discover how a brilliant astronomer named Henrietta Swan Leavitt used pulsing "heartbeat" stars to measure the impossible, and how a trick called parallax helps scientists measure stars without a giant tape measure. Plus, find out why space is expanding like an inflating balloon and whether the universe actually has an edge! Packed with billions of galaxies and brain-melting facts, this episode of Science is Not Boring will leave you starstruck. Blast off with us today!

## Transcript

[0:00] SPEAKER_00: Welcome to Science Is Not Boring by Kidopoly.com.
[0:04] SPEAKER_00: I'm Mira.
[0:05] SPEAKER_00: And I'm Finn.
[0:06] SPEAKER_00: Finn, let's think about distance.
[0:09] SPEAKER_00: If you jumped in a car and drove at highway speeds to the very nearest star other than our Sun, do you know how long it would take?
[0:18] SPEAKER_00: Hmm.
[0:19] SPEAKER_00: Space is huge, so it's a long trip.
[0:22] SPEAKER_00: Maybe a hundred years?
[0:25] SPEAKER_00: Try 48 million years.
[0:29] SPEAKER_00: No way! 48 million?
[0:31] SPEAKER_00: What if we take a super fast spaceship?
[0:34] SPEAKER_00: Even in our farthest spaceship, like Voyager 1, it would take forever.
[0:39] SPEAKER_00: Voyager 1 launched in 1977 and travels at 38,000 miles per hour.
[0:47] SPEAKER_00: Wow, it's been flying out into the dark for nearly 50 years.
[0:51] SPEAKER_00: Exactly.
[0:52] SPEAKER_00: But even at that incredible speed, it would still take 73,000 years to reach that nearest star.
[1:01] SPEAKER_00: 73,000 years?
[1:03] SPEAKER_00: That's longer than all of recorded human history.
[1:06] SPEAKER_00: It really is, and that is just the absolute closest star to us.
[1:11] SPEAKER_00: Is that star the only other one out there?
[1:13] SPEAKER_00: Oh, not even close.
[1:15] SPEAKER_00: Our own galaxy, the Milky Way, contains between 100 billion and 400 billion stars, and that's just our home neighbourhood.
[1:25] SPEAKER_00: 400 billion stars?
[1:27] SPEAKER_00: In just one galaxy?
[1:29] SPEAKER_00: Yep.
[1:30] SPEAKER_00: And today we are answering one of the biggest questions ever.
[1:34] SPEAKER_00: How big is the universe?
[1:36] SPEAKER_00: And does it ever end?
[1:38] SPEAKER_00: Wait, if it's that big, how do we even know how far away things are?
[1:42] SPEAKER_00: We can't exactly stretch a giant tape measure across space.
[1:45] SPEAKER_00: We definitely can't.
[1:47] SPEAKER_00: Today we'll find out how astronomers measure the impossible, why looking into space is actually a form of time travel, and whether the universe has an edge.
[1:57] SPEAKER_00: Okay, start from the beginning.
[1:59] SPEAKER_00: Just how big is space?
[2:01] SPEAKER_00: Well, to measure space, normal miles are way too small.
[2:05] SPEAKER_00: We use something called a light year, which is the distance light travels in one single year.
[2:11] SPEAKER_00: Light is super fast, right?
[2:13] SPEAKER_00: How fast are we talking?
[2:15] SPEAKER_00: Light zips through space at 186,000 miles per second.
[2:22] SPEAKER_00: If you could travel at the speed of light, you could reach the moon in just 1.3 seconds.
[2:29] SPEAKER_00: To the moon in one second?
[2:31] SPEAKER_00: That's ridiculously fast.
[2:33] SPEAKER_00: It's the ultimate speed limit of the universe.
[2:36] SPEAKER_00: So in one whole year, light travels about 5.88 trillion miles.
[2:43] SPEAKER_00: Almost 6 trillion miles?
[2:45] SPEAKER_00: That's just one light year.
[2:47] SPEAKER_00: Yep, and that nearest star we talked about.
[2:50] SPEAKER_00: It's called Proxima Centauri, and it's 4.24 light years away.
[2:55] SPEAKER_00: So that's roughly 25 trillion miles away.
[2:59] SPEAKER_00: But wait, how do scientists actually measure that without a tape measure?
[3:03] SPEAKER_00: They use a really clever trick called parallax.
[3:07] SPEAKER_00: Let's travel back to the year 1838 to a mathematician and astronomer named Friedrich Bessel.
[3:14] SPEAKER_00: Where was he?
[3:15] SPEAKER_00: Did he have a giant observatory?
[3:17] SPEAKER_00: Yes, he worked at the Koenigsberg Observatory in Prussia, and he spent 28 years trying to perfect his measurements.
[3:26] SPEAKER_00: 28 years?
[3:27] SPEAKER_00: He really wanted to measure a star.
[3:30] SPEAKER_00: He specifically wanted to measure a star called 61 Signe.
[3:34] SPEAKER_00: Astronomers noticed it was moving faster across the sky than the other stars, so they nicknamed it the Flying Star.
[3:42] SPEAKER_00: So how did he measure it?
[3:43] SPEAKER_00: Did he use a giant ruler?
[3:45] SPEAKER_00: No ruler.
[3:46] SPEAKER_00: He looked at the star and then waited six whole months until Earth had moved to the exact opposite side of the Sun.
[3:54] SPEAKER_00: Oh, I get it.
[3:56] SPEAKER_00: Because Earth moved, he looked at the star from a completely different angle.
[4:00] SPEAKER_00: Exactly! Hold your finger in front of your face and close one eye, then switch eyes.
[4:06] SPEAKER_00: Your finger seems to jump back and forth compared to the background, right?
[4:11] SPEAKER_00: Yeah, it jumps.
[4:12] SPEAKER_00: So the star did that too, against the deeper background stars.
[4:16] SPEAKER_00: Yes, but the shift was incredibly tiny.
[4:20] SPEAKER_00: Bessel measured a shift of just 0.3136 arcseconds.
[4:26] SPEAKER_00: Arcseconds?
[4:27] SPEAKER_00: How tiny is that?
[4:29] SPEAKER_00: It's like standing in San Francisco and trying to measure the exact width of a house all the way over in New York City.
[4:37] SPEAKER_00: What?
[4:38] SPEAKER_00: How could anyone see something that small?
[4:41] SPEAKER_00: He used a special instrument called a heliometer.
[4:44] SPEAKER_00: It looks like a long brass telescope, but the lens at the front was literally cut in half.
[4:51] SPEAKER_00: He cut the lens in half?
[4:53] SPEAKER_00: Why?
[4:54] SPEAKER_00: By sliding the two halves, it split the image of the star in two, allowing for incredibly precise measurements.
[5:02] SPEAKER_00: He figured out 61 signi was about 10.4 light years away.
[5:07] SPEAKER_00: But wait, if a star is super far away, the angle wouldn't shift at all, right?
[5:13] SPEAKER_00: Exactly.
[5:14] SPEAKER_00: Parallax only works for nearby stars.
[5:17] SPEAKER_00: For deeper space, we were totally stuck until 1912, when a brilliant scientist named Henrietta Swan Leavitt changed everything.
[5:27] SPEAKER_00: What did she do?
[5:28] SPEAKER_00: Did she invent a new telescope?
[5:30] SPEAKER_00: Nope.
[5:31] SPEAKER_00: She was part of a group of brilliant women, known as human computers, at Harvard College Observatory.
[5:38] SPEAKER_00: They analyzed thousands of glass photographic plates of the night sky by hand.
[5:44] SPEAKER_00: Wow, they just stared at tiny dots on glass all day.
[5:48] SPEAKER_00: That sounds like really hard work.
[5:50] SPEAKER_00: It was.
[5:51] SPEAKER_00: She carefully examined plates of a distant star cluster, and she found a special type of star called a Cepheid variable.
[6:00] SPEAKER_00: These stars actually pulse.
[6:02] SPEAKER_00: They get brighter, then dimmer, then brighter again, like a slow heartbeat in space.
[6:08] SPEAKER_00: A pulsing star?
[6:09] SPEAKER_00: That sounds awesome! But how does a blinking star help measure distance?
[6:14] SPEAKER_00: Henrietta discovered something mind-blowing.
[6:17] SPEAKER_00: The slower the star pulsed, the brighter it actually was.
[6:22] SPEAKER_00: It's known as Levitt's Law.
[6:24] SPEAKER_00: Wait, so if scientists time the pulsing, they know exactly how bright the star is supposed to be.
[6:30] SPEAKER_00: Yes, and if you know its true brightness, you can compare it to how dim it looks from Earth.
[6:36] SPEAKER_00: That tells you exactly how far away it is.
[6:39] SPEAKER_00: Oh wow! Like how a flashlight looks dimmer the further away your friend walks in the dark.
[6:45] SPEAKER_00: Exactly! Her discovery was so important that astronomer Edwin Hubble used it to prove that the Andromeda galaxy was entirely separate from the Milky Way.
[6:55] SPEAKER_00: She gave us the yardstick to the universe.
[6:58] SPEAKER_00: So she proved the universe was way bigger than anyone thought.
[7:02] SPEAKER_00: How far can we see today?
[7:04] SPEAKER_00: This is where it gets crazy.
[7:05] SPEAKER_00: Because light takes time to reach us.
[7:08] SPEAKER_00: Looking into space is literally looking back in time.
[7:11] SPEAKER_00: Time travel?
[7:12] SPEAKER_00: Are you serious?
[7:14] SPEAKER_00: Totally! It takes light from our own sun eight minutes to reach Earth.
[7:18] SPEAKER_00: So we always see the Sun as it was eight minutes ago.
[7:22] SPEAKER_00: Wait, so if we look at a really distant galaxy, we're seeing it how it looked millions of years ago.
[7:28] SPEAKER_00: Billions! Recently, the James Webb Space Telescope spotted a galaxy called Jade's GSZ130.
[7:36] SPEAKER_00: That is a wild name.
[7:37] SPEAKER_00: How old is the light from that one?
[7:39] SPEAKER_00: The light travelled for 13.4 billion years to reach us.
[7:44] SPEAKER_00: We are seeing it as it existed just 320 million years after the Big Bang, at the very dawn of the universe.
[7:51] SPEAKER_00: Wait wait wait! The light is 13.4 billion years old?
[7:55] SPEAKER_00: Earth didn't even exist back then.
[7:58] SPEAKER_00: Not even close.
[7:59] SPEAKER_00: Earth is only about 4.5 billion years old.
[8:03] SPEAKER_00: We are literally watching the ancient past unfold.
[8:07] SPEAKER_00: But if the light travelled for 13.4 billion years, does that mean the galaxy is 13.4 billion light years away?
[8:16] SPEAKER_00: Actually, it's much further now.
[8:19] SPEAKER_00: Space itself is expanding, like a giant balloon inflating.
[8:23] SPEAKER_00: The fabric of the universe is stretching out in every single direction.
[8:27] SPEAKER_00: The fabric of the universe?
[8:30] SPEAKER_00: So the space between the galaxies is actually getting bigger.
[8:33] SPEAKER_00: Exactly.
[8:34] SPEAKER_00: Because of that expansion, that early galaxy is now roughly 33.6 billion light years away.
[8:42] SPEAKER_00: And the whole part we can see is a massive sphere about 93 billion light years across.
[8:48] SPEAKER_00: 93 billion?
[8:50] SPEAKER_00: I can't even picture that.
[8:52] SPEAKER_00: What happens at the edge?
[8:54] SPEAKER_00: Does it hit a giant wall?
[8:55] SPEAKER_00: Scientists don't think there is an edge.
[8:58] SPEAKER_00: It might just keep going forever.
[9:00] SPEAKER_00: It could be completely infinite.
[9:02] SPEAKER_00: Infinite space.
[9:04] SPEAKER_00: And inside that space, there are estimated to be up to two trillion galaxies, each one packed with billions of stars.
[9:12] SPEAKER_00: My brain is officially melting.
[9:15] SPEAKER_00: Here's a fun fact to help you picture the scale.
[9:18] SPEAKER_00: If our giant sun was shrunk down to the size of a single grain of sand.
[9:22] SPEAKER_00: Okay, sun is a grain of sand.
[9:25] SPEAKER_00: The nearest star, Proxima Centauri, wouldn't be the next grain over.
[9:30] SPEAKER_00: It would be another grain of sand four miles away.
[9:33] SPEAKER_00: Haha, four miles of empty space between two grains of sand?
[9:38] SPEAKER_00: Space really is mostly just empty space.
[9:41] SPEAKER_00: Alright, Finn, quiz time.
[9:43] SPEAKER_00: Are you ready?
[9:44] SPEAKER_00: Okay, I'm ready.
[9:45] SPEAKER_00: Lay it on me.
[9:46] SPEAKER_00: First question.
[9:48] SPEAKER_00: What is the name of the nearest star besides our sun?
[9:55] SPEAKER_00: Next one.
[9:56] SPEAKER_00: How many years would it take our farthest spaceship to get there?
[10:04] SPEAKER_00: Question three.
[10:05] SPEAKER_00: Who discovered how to use pulsing stars to measure deep space in 1912?
[10:11] SPEAKER_00: Here's number four.
[10:13] SPEAKER_00: What do we call it when a star seems to shift back and forth as Earth orbits?
[10:22] SPEAKER_00: Last question.
[10:23] SPEAKER_00: How wide is the observable universe?
[10:30] SPEAKER_00: Great job! Let's see how you did.
[10:33] SPEAKER_00: The first answer is Proxima Centauri.
[10:37] SPEAKER_00: For question two, it would take 73,000 years.
[10:42] SPEAKER_00: Number three, the answer is Henrietta Swan Levitt.
[10:47] SPEAKER_00: Question four, that apparent shift is called parallax.
[10:51] SPEAKER_00: And the final answer is 93 billion light years across.
[10:57] SPEAKER_00: I got most of those.
[10:59] SPEAKER_00: But honestly, thinking about infinite space makes me feel so tiny.
[11:04] SPEAKER_00: We might be tiny, but think about this.
[11:07] SPEAKER_00: Our brains are powerful enough to figure out the size of the entire universe just by watching the stars from right here on Earth.
[11:15] SPEAKER_00: That is actually really cool.
[11:17] SPEAKER_00: We're like cosmic detectives solving the biggest mystery ever.
[11:22] SPEAKER_00: Exactly.
[11:23] SPEAKER_00: Hey, if you love exploring the universe with us, please leave us a five-star review.
[11:28] SPEAKER_00: Just scroll down on your podcast app and tap the stars.
[11:32] SPEAKER_00: Yeah, tap a star for Proxima Centauri.
[11:35] SPEAKER_00: And don't forget to head over to our site, kidopoly.com.
[11:38] SPEAKER_00: We've got tons of fun learning games and activities there.
[11:41] SPEAKER_00: That's right.
[11:42] SPEAKER_00: And if you want to shout out on the show or just want to say hi, email us at hello at kidopoly.com.
[11:49] SPEAKER_00: See you next time on Science Is Not Boring.
[11:52] SPEAKER_00: Bye everyone! Keep looking up.

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