How was the galaxy made?

Have you ever wondered how our glowing, glittering galaxy was actually made? Join Mira and Finn on an epic journey through space and time to discover the secrets of the Milky Way! Imagine trying to count all 400 billion stars in our galaxy—it would take you over twelve thousand years without stopping! But long, long ago, none of these stars existed. The universe was just a dark, freezing, silent soup of gas. Learn how a superhero force of nature called gravity stepped in to squeeze the gas together until it was so hot, it burst into the very first giant stars! You will hear all about how mini-galaxies smashed into each other like a giant game of cosmic bumper cars to build the massive swirling galaxy we live in today. Plus, discover the amazing astronomer Vera Rubin, who figured out that our galaxy is mostly held together by invisible "dark matter" glue! You'll even find out what a Cosmic Year is, and why the last time Earth was in this exact spot in space, the first dinosaurs were walking the Earth! Get ready for a mind-blowing space adventure!

Transcript

SPEAKER_01 0:48

Welcome to Science Is Not Boring by Kidopoly.com. I'm Mira. And I'm Finn. Before we start, a big hello to Astrid and Fallon in Queensland, Australia.

SPEAKER_00 1:00

Yeah, hi Astrid and Fallon. They actually ask us how the galaxy was made. This one is for you.

SPEAKER_01 1:07

Okay, Finn, I want you to imagine trying to count to 400 billion. If you counted one number every single second, day and night, without stopping, it would take you over 12,000 years. Whoa! 12,000 years? I'd be out of breath. Why are we counting that high? Because that is how many stars might be in our home galaxy, the Milky Way. Up to 400 billion of them, shining in the dark.

SPEAKER_00 1:37

That is impossible to even picture in my head.

SPEAKER_01 1:40

And the craziest part? Long, long ago, none of it existed. No stars, no planets, no black holes. Just complete silent darkness.

SPEAKER_00 1:52

So how did we get from total darkness to a giant swirling city made of hundreds of billions of stars?

SPEAKER_01 1:58

That is exactly what we are going to find out today. We are going on a journey through time and space to see how the galaxy was built, piece by piece. Let's rewind the clock to about 13.6 billion years ago.

unknown 2:12

Ha!

SPEAKER_00 2:12

That is a lot of rewinding. I can't even remember what I had for breakfast.

SPEAKER_01 2:17

Well, back then, the universe was in a period scientists actually call the Dark Ages. It was mostly just a giant, invisible, freezing cold soup of hydrogen and helium gas spreading out in all directions.

SPEAKER_00 2:31

So it was just boring and empty everywhere?

SPEAKER_01 2:34

Not empty, just dark and quiet. But then a superhero stepped in to change everything. A force of nature called gravity.

SPEAKER_00 2:44

Oh, gravity! The thing that keeps me from floating off my chair right now.

SPEAKER_01 2:49

Exactly! Gravity started slowly pulling tiny bits of that gas together. Over millions of years, these gas clouds got thicker, heavier, and super crowded. And when gas gets squeezed that tightly, it gets incredibly hot.

SPEAKER_00 3:05

How hot are we talking? Like inside a volcano hot?

SPEAKER_01 3:09

Way, way hotter! Deep inside the centre of these clouds, the temperature reached over 15 million degrees Celsius. That's crazy! Everything would melt! At that extreme temperature, the gas squished together so hard that a nuclear reaction happened. Boom! The very first stars lit up the darkness.

SPEAKER_00 3:32

Ha ha, yes!

SPEAKER_01 3:33

Let there be light. But these weren't like our nice warm sun. These first stars were giant blue monsters, maybe hundreds of times bigger than the sun. They burned super bright, incredibly fast, and then exploded in giant blasts called supernovas, throwing new elements out into space.

SPEAKER_00 3:54

That sounds like an awesome fireworks show. But wait, a few huge stars exploding isn't a whole galaxy, right? Right.

SPEAKER_01 4:02

A galaxy is a massive collection of stars, dust and gas held together by gravity.

SPEAKER_00 4:09

Just how massive? Where exactly do we fit in?

SPEAKER_01 4:13

The Milky Way is so big that if our whole solar system, the Sun and all the planets, were shrunk down to the size of a coin, the Milky Way would be the size of the entire continent of North America.

SPEAKER_00 4:27

No way. That's gigantic! How does something get that big?

SPEAKER_01 4:32

To build something that enormous, gravity had to pull thousands of smaller star clusters together. They formed mini galaxies first, roaming through space. And then what happened next? Did they just stay mini? Nope, they played the most epic game of cosmic bumper cars. Over billions of years, these mini galaxies smashed into each other, melting together to form bigger and bigger galaxies.

SPEAKER_00 5:00

Wait, galaxies crash into each other? Isn't that dangerous for the planets?

SPEAKER_01 5:06

It sounds terrifying, but space is mostly just that: empty space. The distance between stars is so huge that when galaxies collide, the stars usually just pass right by each other, like ghosts. The Milky Way actually swallowed up several smaller dwarf galaxies to get to its size today.

SPEAKER_00 5:27

Haha, that's wild. It's like a giant cosmic smoothie that keeps getting bigger.

SPEAKER_01 5:33

Exactly. And as all this stuff merged together, this giant smoothie started spinning. Gravity pulled it down and it flattened out into a shape like a giant swirling pancake, spinning at over 800,000 kilometres per hour.

SPEAKER_00 5:50

Wait, if it's a pancake spinning that fast, why don't the stars just fly off into space? Like when I spin a merry-go-round way too fast and fall off.

SPEAKER_01 6:00

That is the exact question a brilliant astronomer named Vera Rubin asked in the 1960s and 1970s. Vera Rubin, what did she do to figure it out? She used incredibly powerful telescopes and brand new instruments to measure exactly how fast galaxies were spinning. According to all the laws of physics, she expected the stars near the outside edge of the galaxy to be moving slowly.

SPEAKER_00 6:27

Yeah, that makes sense. Like the outside edge of a record player.

SPEAKER_01 6:31

But when she looked at the data, she was completely shocked. She found out the outer stars were moving incredibly fast, and the visible stars couldn't supply enough gravity to hold them. Oh no! So the galaxy is breaking apart? At those speeds, the galaxy's visible gravity, the pull from all the stars and gas we can see, should not have been strong enough to hold them. They really should have been flung right out into deep space. So what is holding us in? Are we going to fly away into the dark? Don't worry, we are totally safe. Vera Rubin's discovery made scientists realise there had to be a huge amount of invisible stuff acting like cosmic glue holding the galaxy together. Invisible stuff?

SPEAKER_00 7:20

Like magic force fields?

SPEAKER_01 7:22

Nope, dark matter! It's a mysterious type of matter that doesn't shine, doesn't reflect light, and doesn't block light. But it has a ton of mass, which means it has a ton of gravity.

SPEAKER_00 7:36

Wait, so the whole galaxy is filled with invisible glue that we can't even see.

SPEAKER_01 7:41

Yes, in fact, there is about five times more dark matter in our galaxy than regular matter. Without Vera Rubin's amazing detective work, we wouldn't even know that our galaxy is mostly made of invisible secrets.

SPEAKER_00 7:56

Okay, so the galaxy is huge, it's spinning super fast, and it's mostly held together by invisible dark matter. What about our Sun? Where are we?

SPEAKER_01 8:06

Our Sun lives in one of the Milky Way's beautiful spiral arms, called the Orion arm. We are located about 26,000 light years away from the centre of the galaxy.

SPEAKER_00 8:17

Do we spin around the centre too, like a planet orbits the Sun?

SPEAKER_01 8:22

We definitely do. We are zipping around the centre of the Milky Way, but because it's so huge, it takes our solar system about 230 million years to make one full circle. Scientists call this a cosmic year.

SPEAKER_00 8:37

Wow! 230 million years just for one single lap.

SPEAKER_01 8:43

Yep, that means the last time Earth was in this exact spot in the galaxy, the very first dinosaurs were just starting to walk on the Earth during the Triassic period.

SPEAKER_00 8:54

Haha, that is mind-blowing. I wonder if a T-Rex knew he was flying through space. Have scientists found any other crazy galaxies out there?

SPEAKER_01 9:03

Yes. Recently, a super powerful space observatory called the James Webb Space Telescope looked incredibly far into deep space. What did it see out there? It actually looked back in time by capturing incredibly old light. It found one of the oldest galaxies ever discovered, named Jade's GSZ140, which formed just 290 million years after the universe began.

SPEAKER_00 9:33

That sounds like a long time, but for the universe, that's like a baby picture.

SPEAKER_01 9:38

Exactly! It's helping scientists understand how those very first stars and galaxies lit up the dark and started building the universe we see today. Alright Finn, time for the quiz. Are you ready?

SPEAKER_00 9:51

Okay, I'm ready. Let's do this.

SPEAKER_01 9:54

First question. How many stars are estimated to be in the Milky Way galaxy? Next one. What superhero Force of Nature pulled the early gas together to form the first stars? Question 3. What was the name of the brilliant astronomer who discovered evidence of dark matter? Here's number four. How many Earth years does it take the Sun to complete one cosmic year? Last question. What is the name of the spiral arm where our Sun is located in the Milky Way? Great job! Let's see how you did. The first answer is there are up to 400 billion stars in the Milky Way. For question two, the force that pulled everything together was gravity. Number three, the answer is Vera Rubin was the astronomer who found the invisible glue. Question 4. One cosmic year takes about 230 million Earth years. And the final answer is, the Sun lives in the Orion arm of the galaxy.

SPEAKER_00 11:20

I really love the idea of a cosmic year. Next time it's my birthday, I'm going to tell everyone I'm not even a tiny fraction of a cosmic year old.

SPEAKER_01 11:30

You would be a very, very tiny fraction of a cosmic year, Finn. Science is so cool, there is always more to explore and more mysteries to solve.

SPEAKER_00 11:41

And if you guys liked exploring the galaxy and learning about dark matter with us, you should leave us a five-star review. Give us a star for every bit of dark matter holding the universe together.

SPEAKER_01 11:53

Yes, please do. Just scroll down on your podcast app and tap the five stars. It really helps other kids find the show so we can all learn together.

SPEAKER_00 12:03

Oh, and don't forget to check out our site, kidopoly.com. We've got tons of fun learning games and awesome activities there.

SPEAKER_01 12:11

Exactly! Head over to our site, kidopoly.com, to keep the discovery going. And if you want your own shout out on the show, like Astrid and Fallon, or just want to say hi, email us at hello at kidopoly.com.

SPEAKER_00 12:27

Yeah, send us an email at hello at kidopoly.com and tell us your favourite space fact.

SPEAKER_01 12:33

Thanks for listening, everyone. Keep looking up. See you next time on Science Is Not Boring. Bye.