**Derek**: Do people really understand the scale of the universe?

**Participant**: Damn, really? That's... okay.

**Derek**: This task is going to seem ridiculously easy.

Rank these things from smallest at the top to biggest on the bottom.

But sometimes you have to ask the question no one would bother to in order to figure out what people are actually thinking.

**Participant**: This is really gonna put my astronomy skills to the test, so.

**Participant**: Moon. I don't know, moon.

**Participant**: Yeah, I'd say moon is probably the smallest.

**Participant**: I'd say stars are smallest.

**Participant**: But the sun is a star.

**Participant**: So this is like a science quiz.

**Participant**: I'll say planets are the smallest. I'd say planet might be the top of the line.

**Participant**: Is the sun bigger than the moon?

**Participant**: It depends on the planet, right?

**Participant**: It does, but as a general category.

**Participant**: Stars, then moons.

**Participant**: And then there's stars-

**Participant**: Yeah?

**Participant**: Around the planet.

**Participant**: The sun is a star, right? I think.

**Participant**: Yeah, it is.

**Participant**: You think this one's next? I trust you.

**Participant**: Dude, we're talking about a galaxy, bro. We're talking everything.

**Participant**: You're looking at the galaxy too? (group laughs) Okay, like, okay.

**Participant**: I think it's this one and then this one.

**Participant**: You're right.

**Participant**: You can do it.

**Participant**: Wait, no.

**Participant**: Unless you believe in the multiverse, then you know-

**Participant**: I think you're taking this, like, four-dimensional chess level.

**Participant**: I think the moon would be bigger, no?

**Participant**: I mean, you'd think right? Because like it looks bigger.

**Participant**: Yeah.

**Participant**: Yeah.

**Participant**: Is this supposed to be like a science lesson? (laughs)

**Participant**: Like there is, there's definitely some science to this.

**Participant**: Okay.

**Participant**: We are not astrology majors. (Derek laughs)

**Derek**: So what is a moon? Like, how's a moon different from a planet?

**Participant**: It's collection of dust, maybe?

**Participant**: The way that they come about in astrology and like the, I don't know, like the meteors.

**Participant**: Planets is like human life. Already exists or potentially can exist.

**Participant**: And a planet has its own like, I don't know-

**Participant**: Atmosphere.

**Participant**: I think a planet's capable-

**Participant**: Yes!

**Participant**: Of having its own atmosphere or something. (hands slap)

**Participant**: And then the atmosphere of the moon and the planet are completely different.

**Participant**: Whether or not it has like an atmosphere.

**Derek**: I get why some people would think this, because the Earth has an atmosphere, while our moon has essentially no atmosphere,

but Titan, Saturn's largest moon, actually has a thick atmosphere, while mercury has no substantial atmosphere.

So if having an atmosphere isn't what makes a planet, then what is it?

**Participant**: We don't know if the moon has people on. It could.

**Participant**: You think the moon could have people on it?

**Participant**: There could be moon people. We never know.

**Participant**: I'm thinking like orbits or something. Something around there.

**Participant**: I think natural satellite is the term used.

So, like, you'll always have moons around the planet. You can't see a planet around a moon.

**Participant**: How many planets do we know of?

**Participant**: Uh...

**Participant**: Huh. (laughs) Mm. Mm. (Derek laughs)

**Participant**: I don't know. Well-

**Participant**: Any guess?

**Participant**: Let's see.

**Participant**: Seven, eight?

**Participant**: Seven or nine?

**Participant**: Do we have 11 in our solar system?

**Participant**: I think a planet has to be certain size to be considered a planet, 'cause you look at Pluto, they say it's not a planet because it's too small.

**Participant**: Pluto doesn't count as a planet anymore.

**Participant**: Pluto's technically not a planet. That's a dwarf planet?

**Participant**: Everyone knows the poor story of Pluto, I think.

**Participant**: Because everybody loves Pluto. (bright music)

**Derek**: When Pluto was discovered in 1930, it was hailed the ninth planet, but it quickly became clear that Pluto was different.

The real nail in the coffin came (thunder cracks) on the 5th of January, 2005, when astronomers discovered Eris, (gentle music) an object in the Kuiper belt that's around 30% more massive than Pluto.

Similar large objects had already been discovered and more were likely to follow.

So scientists faced a choice: either add a whole bunch more planets or demote Pluto.

In 2006, the decision was made, and a new definition for a planet was established.

**Participant**: They should just, like, get over it.

**Participant**: A planet anymore

**Participant**: Pluto had it coming from the beginning. (audience applauds)

**Participant**: Stay in your lane?

**Participant**: Stay in your lane. (audience applauds)

**Participant**: Stay in your lane.

**Participant**: Our moon-

**Participant**: Our moon.

**Participant**: Has five times the mass of Pluto.

**Participant**: What?

**Participant**: So just get over it.

**Participant**: Is our moon a planet?

**Participant**: No, it's a moon.

**Derek**: To be a planet, an object now had to satisfy three criteria.

First, it must orbit the sun.

Second, it must have enough self-gravity so that it's round or almost round.

And third, it must be gravitationally dominant and cleared out its neighborhood.

Pluto satisfies the first two criteria, but not the third.

So now we're back to the set of planets without Pluto.

**Participant**: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune. Oh, it's eight.

**Participant**: Nice. (participant laughs) And he named them all. Bonus points.

How many planets outside the solar system?

**Participant**: Oh.

**Participant**: Maybe around a couple hundred to 1,000, maybe?

**Participant**: Probably a couple million. (laughs)

**Participant**: Probably more than that.

**Participant**: Probably more than that.

**Derek**: I mean, in terms of the number that we know is about 5,000 right now.

**Participant**: Oh.

**Derek**: That have been identified, but like, you're right, there's many more, but we just haven't seen them yet, so we don't know.

So the moons are the smallest. They go around the planets. Planets go around the stars.

What makes a star a star?

**Participant**: Kind of like a dead planet, right? Like it's just emitting heat.

**Participant**: Like little gas things. And they explode all the time. And we don't even see them. But I don't know where they come from. Can you tell me?

**Derek**: If you have a bunch of just like gas, as you say, like hydrogen, helium, and that all kind of clumps together, it forms a star.

**Participant**: Oh.

**Derek**: And then like you say, there's like fusion in the middle, explosions in the middle that are giving out light and heat and stuff like that.

**Participant**: Wow. You just taught me something new. I didn't even know that.

**Derek**: There you go.

**Participant**: Doesn't it take eight Earths to fill the sun?

**Participant**: A million Earths.

**Participant**: A million Earths. I got it wrong. Okay, I'm stupid.

**Derek**: (laughs) No, no, but like it's a lot, right?

Here's one way to put this in perspective. In our solar system, there are eight planets, hundreds of moons, millions of asteroids and more.

But in terms of mass, all that only makes up 0.14% of the mass of our solar system.

The other 99.86% of the mass is the sun.

That is just how much bigger and more massive the sun is.

**Participant**: Moon's smallest, then planets and stars. (students chattering faintly) (tone beeps)

**Derek**: Well, what is a galaxy? Like, what is that?

**Participant**: Uh...

**Participant**: A group of planets in, I'd say, a certain amount of proximity.

**Participant**: Like the solar system. Like the system of planets. So like just how we have our solar system is what makes the galaxy.

**Participant**: A ton of stars, moons, and planets in together makes the galaxy?

**Participant**: Maybe just a collection of like solar systems?

**Derek**: So how many is a collection of solar systems? How big is a galaxy? How many stars? (gentle music)

**Participant**: Uh... Help. (group laughs) I don't know.

**Participant**: Phone a friend.

**Participant**: 60,000.

**Participant**: Millions, I'd say, millions.

**Participant**: Tens of millions of stars, perhaps?

**Derek**: How many stars in a galaxy? Roughly. Ballpark.

**Participant**: Probably hundreds of millions.

**Participant**: Million? Billion?

**Derek**: 100 billion.

**Participant**: Oh, you are way off.

**Participant**: That was crazy. (laughs)

**Participant**: Oh my God. (laughs)

**Participant**: That was crazy. (laughs)

**Participant**: You said 60. 100 billion?

**Derek**: 100 billion stars.

**Participant**: Damn, really? That's... okay.

**Derek**: Number of stars in the galaxy, that can vary depending on the size of the galaxy, but like 100 billion, 200 billion, 300 billion. 50 billion, like that's like kind of the ballpark numbers from the galaxy.

**Participant**: Okay. But the average is 100 billion?

**Derek**: Yeah.

**Participant**: That's crazy,

**Derek**: Right?

**Participant**: Yeah. (laughs)

**Derek**: They're huge. There's a funny question. Are there more trees on Earth or stars in our galaxy?

**Participant**: (raspberries) Oh, actually, Mm. I'm now thinking about like a math problem where it's basically, you have to find, I guess, the whole entire surface area that, oh, huh.

**Derek**: The answer is, I'll save you the trouble, there are more trees on Earth than there are stars in the galaxy, in our Milky Way Galaxy.

**Participant**: You know it figures, you know? (laughs)

**Derek**: So a galaxy is a huge collection of stars, planets, gas, dust, dark matter, and other objects, all bound together by gravity.

And then what is around the Milky Way galaxy?

**Participant**: More galaxies.

**Derek**: There are more galaxies, but they're kind of far away. So what's between us and those other galaxies?

**Participant**: The...

**Participant**: Uh...

**Participant**: Uh...

**Participant**: Like all types of vastness, you know? Super novas.

**Participant**: Dark matter?

**Participant**: Stars? (laughs)

**Derek**: You know, this is the thing that I find nuts, and one of the things I wanted to see if people know, but like the Milky Way is like one galaxy, but it's huge.

**Participant**: Right.

**Derek**: It's like 100,000 light-years across. That's pretty big.

**Participant**: Mm.

**Derek**: You know what I mean? But then around us, there's nothing.

**Participant**: Hmm.

**Participant**: Oh wow, I didn't know that.

**Derek**: Basically nothing.

**Participant**: Yeah. It's kind of like the continents, right? That you have a continent, but then around it, like there's all this ocean, and then there's like more galaxies, and then there's nothing, and then more galaxies, nothing more galaxies, nothing.

But this animation is not to scale. Really, it should look more like this.

The distances between galaxies are enormous, typically millions of light-years.

If you zoom out further, you find that galaxies are grouped together in clusters, and those clusters make up even larger superclusters, all separated by enormous voids.

And you know how many galaxies there are in the universe?

**Participant**: I'll take a guess and say like 20-something.

**Derek**: How many galaxies in the universe?

**Participant**: (beep) If I know. (laughs)

**Participant**: 12? I don't know. Is it? Is that like close?

**Derek**: It's more, much more.

**Participant**: 20? Oh, much more.

**Participant**: I'm gonna say 100.

**Derek**: More than hundreds.

**Participant**: Thousands?

**Derek**: More than thousands.

**Participant**: (laughs) Oh my gosh.

**Participant**: 10,000.

**Participant**: (participants laughs) 10,000?

**Participant**: 10,000?

**Participant**: That's small.

**Participant**: I mean 10,000 galaxies, but each galaxy's got 100 billion stars.

**Participant**: 16,482.

**Participant**: Hundreds of thousands? Millions? Billions?

**Participant**: 1 billion?

**Participant**: 1 billion?

**Participant**: Or, is that too small?

**Participant**: 1 billion galaxies, each one with 100 billion stars?

**Participant**: I'll say 10 billion that we know of.

**Derek**: What are you gonna say?

**Participant**: The answer is...

**Derek**: The answer is... How many galaxies in the universe? About? Oh jeez. (laughs) (wind rustling) 100 billion.

**Participant**: What, really?

**Derek**: About 100 billion galaxies.

**Participant**: Holy. Seriously?

**Derek**: Yeah. About 100 billion.

**Participant**: Dang, weird.

**Participant**: Oh man. (participants laugh)

**Derek**: It's huge. 100 billion are observable.

**Participant**: And these are just galaxies?

**Derek**: These are galaxies. Each galaxy then has about 100 billion stars.

**Participant**: Okay.

**Derek**: Right? That's mind blowing a little bit.

**Participant**: Right?

**Participant**: Yeah.

**Derek**: This is what I'm saying. I feel like most people don't know the scale of the universe, and that's what I'm out here to talk about.

**Participant**: Mm-hmm.

**Derek**: That's why I wanted to be, like, it's so much bigger than almost anyone thinks.

**Participant**: Right.

**Derek**: In fact, there could be even more, because 100 billion galaxies is a conservative estimate.

Some believe there are up to 2 trillion galaxies in the observable universe.

So it's huge, and between all these galaxies, nothing.

**Participant**: Just nothing.

**Derek**: What a wacky universe, right?

**Participant**: Yeah.

**Derek**: And around each star, there might be, on average, about six planets.

**Participant**: Wow.

**Derek**: So you can think about 100 billion times 100 billion times six, roughly, and that's conservative.

**Participant**: Okay.

**Derek**: Kind of like number of planets may be in the universe.

**Participant**: Mm-hmm.

**Derek**: So it's insanely huge.

**Participant**: Yes. That sounds... That is actually, wow.

**Participant**: I feel like it makes me less stressed, because it's just a blip in the system, man. Nothing's ever that deep. (gentle music)

**Participant**: Whoa. (laughs)

**Derek**: So the universe is insanely huge.

**Participant**: And we're incredibly small. I got you.

**Derek**: (Derek laughs) How does that make you feel?

**Participant**: Very small.

**Derek**: To think about the size of it.

**Participant**: Very small.

**Derek**: I don't know. It doesn't make you feel that small.

**Participant**: Nope?

**Derek**: Because there's not-

**Participant**: You still feel pretty big? (participant laughs)

**Participant**: I don't feel big, but you know, I still feel like this Earth in particular has a pretty decent amount of significant whatever, you know, significance.

**Derek**: This is a special place, for sure.

**Participant**: Yeah.

**Derek**: Yeah. On the 14th of February, 1990, the Voyager 1 spacecraft was about 6 billion kilometers from the sun when it took this picture.

All you see are a few rays of light and a little dot.

Carl Sagan described this picture best. (gentle music)

"Look again at that dot. That's here, that's home, that's us.

On it, everyone you love, everyone you know.

Everyone you ever heard of, every human being who ever was lived out their lives,

every hero and coward, every creator and destroyer of civilization,

every young couple in love, every mother and father, inventor and explorer,

every superstar, every supreme leader,

every saint and sinner in the history of our species lived there,

on a mote of dust suspended in a sunbeam."

The earth is a very small stage in a vast cosmic arena.

To me, it underscores our responsibility to deal more kindly with one another,

and to preserve and cherish the pale blue dot, the only home we've ever known.

**Participant**: I'm glad you taught me something today. I appreciate it. I like learning.

**Derek**: That's awesome. Well, thank you for being open to learning, 'cause that's so important.

**Participant**: The thing that people are worried about is making mistakes, but you can't learn without making mistakes a lot of times. (bright music)

**Derek**: So many people don't know the basics about the universe we live in, but it can even be hard to understand the world we live in, and this has a lot to do with our media ecosystem, which often prioritizes speed over accuracy and sensationalism over facts,

the problem that's so big in science communication, I made a whole video about it.

But Ground News, the sponsor of this video, changes the game by giving you the tools to consume news in a more nuanced and transparent way.

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