Original subtitles

(ethereal music)

HAWKING: We all have questions,

big questions.

JOY (off screen): How big is the universe?

HAWKING: It's part of what it means to be a human.

JIM (off screen): How far away are the stars?

JOY: Joy to boat.

♪ ♪

HAWKING: My name is Stephen Hawking,

and I believe that anyone can answer big questions for themselves.

CAT: This is exciting.

HAWKING (off screen): So with the help of a few ordinary people...

And a team of experts...

CHRIS (off screen): Where you are changes how we see the universe.

HAWKING (off screen): We are going on the ultimate voyage.

JUNA (off screen): These distances are just getting bigger and bigger.

HAWKING (off screen): A quest to answer

the greatest mysteries of the universe...

JIM: Right, let's blow this bad boy up.

HAWKING (off screen): Using the power of the human mind...

JOY: We made it!

♪ ♪

HAWKING: Because anyone can think like a genius.

PEOPLE (off screen): Where are we?

(spacey music)

♪ ♪

HAWKING (off screen): Where are we?

That's a pretty profound question.

If we didn't know where we are, we'd be like monkeys in a forest,

totally unaware of our position in the cosmos.

Fortunately, we humans know everything from the shape of the Earth

to its place in the universe.

But how did we find out?

I believe anyone can work it out.

Let's see if I'm right.

I have asked three ordinary people to come on a journey of discovery.

They will have tools and equipment,

and I want to see if they can grasp the full scale of the universe...

With some fun experiments to find out where we are.

JOY: Where are we?

JIM: That's a really good question.

JOY: We're on Earth.

CAT: Yet there's more planets out there.

JIM: In my solar system.

CAT: In the Milky Way.

JIM: That's where I'm at.

HAWKING (off screen): But how do we know for sure?

The first step is to measure our planet.

How big is it, and is it really round?

The volunteers don't know it, but they are going to find out

the size and shape of the world right here in Nevada.

They'll do it by tackling their first challenge:

how flat is this lake?

CAT (off screen): How do you measure the flatness of a lake?

JOY: With a huge ruler.

(laughter)

JIM: Yeah, she has a point, though.

You need something that you know is flat

to measure the surface of the water against.

JOY: Yeah.

(percussive music)

HAWKING (off screen): This lake holds the secret to the size and shape

of the Earth, but can the team work it out?

To help them, they need a few tools.

JOY: 2 feet, 7 inches.

HAWKING (off screen): First is a powerful laser which projects

a straight beam of light across the surface of the lake.

Next, they'll need a boat.

JIM: Bye.

-Whoo, we just passed through it! -CAT: Yep.

JOY (off screen): Joy to boat.

CAT (over radio): This is Cat, over.

JOY: I want you to go at the front of the laser.

CAT (off screen): Roger.

Now we gotta turn a little to the right.

HAWKING (off screen): If the lake is flat...

The laser beam and the water will always be parallel to each other.

Seen from a boat,

the beam would always stay at the same height above the water

no matter how far you travel into the lake.

But does that happen, and can the team work out why?

Time to find out.

The boat has a whiteboard attached to it which will be a target.

CAT (off screen): We're looking for the laser beam

so that we can mark it on the whiteboard.

JIM: Oh, it's hitting off that.

And we made the first measurement,

and I was pretty confident that we weren't gonna find anything.

CAT (off screen): A little more to the right.

JIM (off screen): Almost there. There we go.

HAWKING (off screen): They take their first reading 500 feet from the shore.

JIM (off screen): Okay, what was the height of it?

Got it.

(tense music)

HAWKING (off screen): For the next measurement,

they'll need to go much further out.

JOY (off screen): Okay, so now I need you go out three miles

away from the laser.

CAT (over radio): All right.

JIM: Awesome.

♪ ♪

HAWKING (off screen): So 3 miles away, where is the laser beam?

Remember, if the lake is flat, it would be the same height as before.

JOY (off screen): Cat, you have to go slightly to the left.

CAT (over radio): You said go slightly to the left?

JOY (over radio): Yeah.

CAT: A little bit more to the right.

JIM: Here we go.

CAT: I don't even think this beam is gonna hit our boat...

(dramatic music)

So we're gonna have to measure it on something else.

CAT: All right.

-JIM: I've no idea. -CAT: Here we go.

JIM: Oh, is that your... your measuring tool?

-CAT: Do you see it? -JIM: Yep.

CAT: Can you mark it?

CAT: Oh, that's good.

JIM: We made the second measurement, and my whole world fell apart.

It's like 6 feet.

-CAT: Yeah. -JIM: Yeah.

CAT: It seems a lot higher. -JIM: Okay.

-CAT: You got it? -JIM: Uh huh.

CAT: All right.

HAWKING (off screen): Just 3 miles away,

the laser seems to have risen by 6 feet.

But we know the beam is level,

so that suggests that the lake is now 6 feet lower.

JIM (off screen): To see a 6-foot drop,

when everything looked flat to me, was kind of mind-boggling.

Definitely kind of shattered my perspective in about one second.

It made me rethink what was going on.

(soft dramatic music)

JIM: Perception is still it's a flat lake, but...

-CAT: It's not a flat lake. -JIM: It's not a flat lake.

CAT (off screen): That was crazy.

I was definitely blown away by the fact

that the laser was that high off the water.

-JIM: Hey. -CAT: Hey, Joy.

-JIM: What's up? -CAT: We're back.

JOY: So how was it?

JIM: The laser was 6 feet up in the air,

and we had to use... -JOY: What?

JIM (off screen): This board to mark it. It was cool...

HAWKING (off screen): The lake is clearly not flat.

It's almost as if it's sloping downhill.

With this realization, my volunteers have made

their first step towards measuring the entire world.

JOY: I think we should make some more measurements, for sure.

-JIM: Yeah, agreed. -CAT: Yeah, totally.

HAWKING (off screen): But they are not the first people

to do it, of course.

In fact, the first person to measure the Earth accurately

was an ancient Greek genius named Eratosthenes.

FRANCISCO: More than 2,000 years ago, Eratosthenes, a very clever philosopher,

mathematician, geometer, from Greece,

he embarked on an experiment to measure the diameter of the Earth.

If the Earth was flat,

anywhere on the flat Earth at a given time during the day,

we would see the sun shining with the same angle.

While, if it is round, that won't be the case.

HAWKING (off screen): Eratosthenes had heard that at noon

on the longest day of the year, the sun shines

directly down the water well in what is now the city of Aswan in Egypt.

Here, the sun must be directly overhead.

So in another location 500 miles to the north,

he made a second observation,

again at noon on the longest day of the year.

FRANCISCO: Here, 500 miles north, he performed this experiment

and he planted a pole vertical

and realized that the pole was casting a shadow.

HAWKING (off screen): The shadow was evidence

that the sun is not overhead, but at an angle.

(light music)

By measuring this angle

and knowing the distance between the two locations...

He was able to calculate that the Earth is a ball,

about 8,000 miles in diameter.

But the question is,

with the right tools, can the volunteers match this genius?

HAWKING (off screen): Our search to find our place in the universe is underway.

My volunteers have discovered the lake is not flat,

but in order to measure the whole world,

they need to make a new measurement,

much further away.

They will need some new tools.

-JOY: Okay, let's get this box open. -JIM: All right.

CAT: Yeah.

-CAT: Hey, what do we have here? -JIM: Tripod.

JOY: That looks like a tripod.

HAWKING (off screen): Now, instead of the laser,

a telescope will enable our volunteers

to look in a straight line to the lake's opposite shore.

But that's not the only instrument they'll need.

-CAT (off screen): We're wondering, okay,

how are we gonna get this next point if it's so high,

it's past our board?

(dynamic music)

♪ ♪

-CAT: Whoa! -JIM: Very cool.

CAT: Are we getting in a helicopter?

CAT: This chopper appears out of nowhere.

CAT: All right, that is awesome.

HAWKING (off screen): Just as the telescope replaces the laser,

the helicopter takes the place of the boat.

JIM (off screen): I'll stay with the telescope.

-JOY: Okay, great. -CAT (off screen): We'll go in

the helicopter.

-JOY: That's a plan. -JIM (off screen): Sounds like a plan.

-JOY: Yeah. -CAT (off screen): All right, let's do it.

BRIAN (off screen): All right, we'll go ahead and lift off.

CAT: This is exciting!

JOY: I love that there are no doors. (laughs)

JOY: We're flying to Pyramid Rock, do you copy that?

JIM: I copy that. You are flying to the Pyramid.

JOY (off screen): The lake looks completely flat from up here.

HAWKING (off screen): If they are twice as far away as before,

how much lower will the far shore of the lake appear to be?

JOY (over radio): Jim, we're going to be at the top

of the pyramid rock.

Jim: Oh, got 'em.

Yeah, I have you on the telescope. Go ahead and land.

(dynamic music)

♪ ♪

JIM: As it lands, it completely disappears from my line of sight.

Joy, are you still airborne?

JOY: Yeah, can you see us landing?

JIM (off screen): The reports from the helicopter, they're still flying,

but I can't see it.

To wrap your head around it in that short of time

was a little difficult for me.

I was like, this is crazy.

JOY: We have landed in our position.

JIM: Okay, Joy, go ahead and lift off.

HAWKING (off screen): They plan to ascend until Jim can see them on the horizon.

Then they'll tell him their altitude.

JOY: Let me know when you can see us on spots of the horizon.

(dramatic music)

♪ ♪

JIM: Oh, I got 'em, I got 'em.

JIM (off screen): Okay, what's your elevation right now?

CAT: All right, Brian, how many feet are we above the lake?

BRIAN: 24 feet.

JOY: Whoo, we made it, 24 feet.

JIM: 24 feet, awesome.

CAT (off screen): 24 feet is a lot higher

than our other two points that we got.

That was awesome, it was great.

HAWKING (off screen): At 6 miles,

the lake has fallen four times lower than before.

So what is going on?

JIM: Okay, you guys, check this out.

So if this line is our laser beam...

CAT: Right.

JIM: That we shot across the lake, right?

And that's the shore, this is the laser, right there.

And we join our data points...

At 6 feet and then all the way out to 24,

this is our source, that's our flat line, right?

And this is the surface of the lake.

HAWKING (off screen): The green line shows the path of the laser

and the view from the telescope.

And the gold line shows how the data points

form the beginning of a curve.

CAT: So that means this lake isn't flat.

JIM: It's not even close.

CAT: No.

JIM: That's crazy.

JIM (off screen): If we can just continue that curvature all the way around

and complete a circle, and we can measure it,

then that gives us the circumference of the Earth.

HAWKING (off screen): With these measurements on the lake,

we can calculate that the Earth's circumference

is around 25,000 miles, which matches Eratosthenes's calculation.

JIM: I still have a hard time wrapping my head around the fact

that we measured the Earth at that lake.

CAT: I'll never look at a lake the same way,

I'll never look at a big body of water the same way,

now that I know it's following the curvature of the Earth.

HAWKING (off screen): Knowing the shape and size of the Earth

is just the beginning of finding out where we are.

To learn more,

we need to journey into space,

to the moon and beyond.

HAWKING (off screen): The moon is our nearest neighbor,

but few people realize its distance from Earth.

So the next challenge in finding out where we are

is to find out how far away the moon is.

To discover this, we need to head into the vast Nevada desert.

CAT: So, what's in the box?

-JOY: Oh! -CAT: Okay.

So it's a tiny Earth and a tiny moon.

HAWKING (off screen): These are scale models of the Earth and the moon.

Their relative size was first discovered by the ancient Greeks,

thousands of years ago.

Back then, the genius who worked it out

was a man called Aristarchus.

CHRIS (off screen): If you look at the moon, there's a bright crater,

and it's called Aristarchus,

named that way to help us remember the man

who told us the size of the moon.

CHRIS (off screen): So how did Aristarchus do it?

The answer is that he simply observed its passage through the sky.

And he calculated that it took one hour

to cover the distance of its own diameter.

Once he'd worked that out, he had to find a way

to make that figure relevant to the size of the Earth.

Aristarchus realized that he could use a phenomenon

called a total eclipse.

And a total eclipse of the moon is a common thing.

It happens once or twice a year,

when the moon passes through the Earth's shadow.

CHRIS (off screen): He discovered that the moon took about

2.7 hours to cross through the Earth's shadow.

And so he then knew that the Earth's shadow

was 2.7 times larger than the moon itself.

CHRIS (off screen): Aristarchus's calculation showed

that the moon was 3,000 miles across in diameter,

and we now know that the true figure is just over 2,000 miles.

What this does is it extends the reach of measurement

out above the Earth's atmosphere and into space.

He says that the universe is a place that scientists can explore as well.

HAWKING (off screen): Once we know the size of the Earth and the moon,

it's possible for my volunteers to take the next step

and find out how far apart they are.

But first, a guess.

JIM: I think it's closer. I think it's about...there.

CAT: That is what I was gonna do.

I was gonna put them...

-CAT: Close, I think. -JIM: Closer than further.

JOY: I think that it's a bit further away.

-CAT: Wow, that far? -JIM: Going big.

-JOY (off screen) I put this as my guess. -JIM: Okay.

HAWKING (off screen): So how can we find out for sure?

This evening, there is a full moon.

That is the final clue they need to think like Aristarchus.

CAT: Maybe, we take the Earth and put the moon in front of it,

until we cover up the moon?

-JIM: Same size? -CAT: Same size.

-JIM (off screen) Okay. -CAT (off screen): Take it till we

lose sight of the moon.

HAWKING (off screen): Cat has the answer.

CAT: I'm looking at the real moon in the sky

and the little moon that we have

and I'm thinking, "Well, they're the same."

So maybe we need to black out the real moon in the sky.

Closer, closer...

CAT: A little closer.

CAT (off screen): All right. I say that's it.

-JIM: Is that it? -CAT: Yeah, so you were right.

The moon is pretty far from the Earth,

yeah, a lot farther than we thought.

HAWKING (off screen): When the scale moon is just the right distance away,

it will cover the real moon perfectly.

That's how you find the distance.

In the desert, the scale models of the moon and Earth are 6 feet apart.

Up in the sky, the real moon is about 240,000 miles away.

CAT (off screen): It worked. I'm not a scientist,

and be able to just do that off a whim

and it just came to me, that was...that was incredible.

(dramatic music)

♪ ♪

HAWKING: By measuring the Earth and our distance to the moon,

we've taken our first step out into space.

CAT (off screen): Good.

HAWKING (off screen): But to find out where we truly are in the universe...

JIM: Got it?

HAWKING (off screen): The next step is to figure out our place

in relation to the brightest object in our sky, the sun.

Today, we know it is nearly 900,000 miles in diameter.

But again, people don't realize how big that really is.

-JIM: Whoa. -CAT: Wow!

JIM: That's the sun, that's massive.

JOY: It looks so big.

HAWKING (off screen): This is the sun at the same scale

as our tiny Earth and moon models.

-CAT: Go this way, -JOY: Okay.

-JIM: Uh, this thing... -JOY: Oh, no, it's...(laughs)

JIM: At first, when we tried to lift it, we could barely pull the model out.

-JOY: All right. -JIM: It's giant.

-CAT: Careful. -JIM: This is really to scale?

JIM (off screen): And then we started unrolling it and it just keeps going

and going and going.

'Cause I just wanted to fill it up with air and see really how big it was.

CAT: It just seemed like it was more and more fabric,

more and more, just keep coming, it kept coming.

JIM (off screen): Oh, wow.

All right, let's blow this bad boy up.

(dramatic music)

♪ ♪

JOY: I was just thinking, wow, how big is this sun

compared to this tiny Earth that I had in my hand.

So if this is the Earth, then this is the sun.

(dramatic music)

♪ ♪

HAWKING (off screen): The sun is almost 110 times the diameter of the Earth.

Now, the next big question: on this scale,

what is the distance between Earth and the sun?

JIM: So how far do we have to move that model to get

the distance, and how are we gonna get the distance exact?

CAT (off screen): I don't know.

HAWKING (off screen): Much like it was with the moon,

the key to answering this question is an eclipse.

But this time, it's a solar eclipse.

When the moon passes in front of the sun,

seen from the Earth,

the sun and moon are exactly the same size.

So they should be able to find the distance

by creating an eclipse on their model.

CAT (off screen): In the solar eclipse, we can't see the sun at all.

So when this sun disappears, you'd have a solar eclipse.

JIM: Boom, there we go.

So all we need is a solar eclipse.

CAT (off screen): Yeah, exactly,

CAT (off screen): We jump in the truck and we just go.

We go in the desert and we just drive, drive, drive.

HAWKING (off screen): How far do they need to drive?

JIM: I think that's about it.

HAWKING (off screen): They decide to stop 400 meters from the sun.

CAT: All right, let's see.

JIM: The moon...right there.

HAWKING (off screen): To make the tiny moon eclipse the sun,

it always has to be 6 feet from the Earth.

-JOY: Okay, so I've got the Earth here. -JIM: All right.

JOY: So we know this distance and now I'm going to see

whether the moon is the same size as the sun.

It's actually a bit smaller, so we have to go a bit closer to the sun.

-CAT: All right, let's move it. -JOY: Let's do it.

HAWKING (off screen): Do they need to be closer or further away?

-CAT: Let's try here, about there? -JIM: Yeah, I think so.

JOY (off screen) The sun is still bigger.

-JIM (off screen) Really? -JOY (off screen) Yeah.

CAT: The sun's still bigger than the moon?

-JOY: Yeah. -CAT: That means we would go that way.

JIM: I'm having a dumb stroke, I'm having a dumb moment.

-JOY: Let's go back. -CAT: All right.

JIM: I think we all felt a bit silly.

CAT: We're walking across the desert.

JIM: What were we thinking?

CAT: How much further do you guys think?

-JIM: I'm saying check it. -CAT: Check it?

JIM: Bam, right there.

JIM: Okay, ready, we look...

JIM (off screen): Oh, we got it.

-CAT: Yeah! -JOY: We got it.

CAT: Yeah.

HAWKING (off screen): They've done it.

On the scale, the sun is just under half a mile from Earth.

Up in space, the distance is 93 million miles.

CAT (off screen): To see it in perspective, I mean,

our Earth was only so big,

and we had to take it across the desert

in order to show distance and, I mean,

that just shows how...

how small we are.

HAWKING: Our volunteers have figured out

the distance between the sun, moon, and Earth...

using nothing more than three round balls and a little bit of logic.

But now we need to find out where we are on a much larger scale.

If we know the sun is 93 million miles away...

How big is the entire solar system?

The ancient astronomers knew from observing the heavens

that there was more to the universe

than the Earth, moon, sun and stars.

They identified five points of light

that moved in a different way from the stars.

These are the planets.

Here on our scale model, Mercury is closest to the sun.

As we head further into the solar system,

we can see Jupiter on the horizon.

Viewed from above, we can see all eight planets aligned.

Neptune is 9 miles away from the sun,

or nearly 3 billion miles in space.

And the entire solar system is 180 billion miles side to side.

CAT: We know we have all the planets, the stars, the sun,

but when you see it for yourself in a perspective,

our solar system is much bigger than we think it is.

(ethereal music)

♪ ♪

HAWKING: We have now found out the true scale of our solar system

and our place within it.

But now I want to take us further into the cosmos

and explore where we are in relation to the stars.

On a clear night, there are 3,000 visible stars,

but how far away are they?

By the 19th century,

telescopes had become powerful enough to hone in on individual stars.

And in 1838, German astronomer Friedrich Bessel

was able to calculate that a nearby star called 61 Cygni

was around 67 trillion miles away from Earth.

This was far greater than any distance

we had encountered in our solar system.

So a new unit of measurement was needed

to take us to interstellar space.

It's called the light year.

It's the distance that light travels in one year...

Whizzing along at 186,000 miles a second.

That's around 5.8 trillion miles a year.

61 Cygni is found to be about 11 light years away.

To try and understand such huge distances,

I want to explore what the speed of light looks like on our scale model.

-JIM: How fast is the speed of light? -CAT: Well, it's fast, right?

HAWKING (off screen): It takes sunlight 8 minutes and 20 seconds

to travel from the sun to Earth.

So in our model, the speed of light

is the speed needed to get from the sun to our model Earth

in 8 minutes and 20 seconds.

How fast is that?

CAT: We know it takes 8 1/2 minutes,

so how fast do we need to move

to get from our model sun to our model Earth?

JOY: Let's be the light.

Let's walk 750 meters and time it and see how long it takes.

-JIM: All right. -CAT: All right.

-JIM: I'll get the watch. -CAT: Let's go.

HAWKING (off screen): On the scale, every foot

that my volunteers travel represents over 40,000 miles.

CAT: How much time have we been walking?

-JIM: 40 seconds. -CAT: Only 40 seconds?

JIM: Yeah.

CAT: And we've gone pretty far.

I mean, I can see the Earth from here.

(laidback rock music)

♪ ♪

HAWKING (off screen): How fast is the speed of light on this scale?

JIM: Almost there, almost there.

-JIM: Passing the moon. -CAT: Hello, moon.

-JIM: And bam. -CAT: What did you get?

JIM: 8 minutes, 35 seconds.

CAT (off screen): Wow. So we pretty much walked

from the sun to Earth in the speed of light.

HAWKING (off screen): Even though it's the fastest speed in the universe,

the speed of light on this scale is just over 3 miles per hour.

That's walking pace.

CAT: So light isn't as fast as we perceive it to be.

JOY: In the entire universe, light appears to travel really slow.

CAT: Wow.

HAWKING (off screen): It's a strange paradox.

Although the speed of light is fast,

distances in space are so huge

that even one light year is not very far at all.

JIM: It's such a revelation, but then it alters...

it just alters your thoughts, and I have to sit in a quiet place

and wrap my head around it for a while.

HAWKING (off screen): If it takes eight minutes for my volunteers to reach

their model Earth, imagine how long it would take to get to our nearest star.

It's called Proxima Centauri.

On our scale model, it would be 126,000 miles away from the sun.

So our volunteers would have to walk

halfway to the real moon to reach it.

In space, the total distance is 4.2 light years.

JIM (off screen): I'd have to walk for 4.2 years continuously

to get to my nearest star.

If I was gonna shrink that down for the purpose of demonstrations,

well, our scale model's gonna be like a speck of sand.

HAWKING (off screen): Even on this scale,

distances have now become too large to comprehend.

We need to shrink our model sun from this...

To this.

CAT: Wow, this is our sun?

From that big giant sun we had earlier is now this?

JIM: Yeah. That little dot.

(dramatic music)

HAWKING (off screen): Even on this tiny scale,

the distance between the tiny sun and our nearest star

would be 17 miles.

We can try and get a grip on this if we light a flare...

17 miles away across the desert.

-CAT: There it is. -JOY: Whoa.

CAT: That is incredible.

(ethereal choir)

JOY (off screen): To see the nearest star so far away, when our sun is that small,

was just amazing; it made me think about all the stars in the sky.

These are the things that feel so familiar to us,

but yet, we don't know anything about them.

(dramatic music)

♪ ♪

HAWKING (off screen): After centuries of observations,

we now know that our sun and its nearest neighbor

Proxima Centauri are part of a small community of 33 stars,

all within 15 light years of Earth.

And this system sits in a network of an estimated 300 billion stars

called the Milky Way.

(dynamic music)

♪ ♪

And until recently, astronomers believed

that this galaxy was the entire universe.

That was the whole answer to the question "where are we?"

Then in the 20th century, a new generation of telescopes

allowed us to explore new formations.

And they seemed to be much further away.

JUNA (off screen): People had been seeing

different smudgy patches of light on the sky,

and they struggled with what these faint smudges on the sky actually are.

HAWKING (off screen): Enter Edwin Hubble, 20th century American astronomer.

Using this telescope at the Mount Wilson Observatory in California,

he made a sensational discovery.

He realized that these smudges were millions of light years from us.

JUNA (off screen): It was Edwin Hubble's discovery

of the distance to these smudgy patches

that indicated that indeed, these were other galaxies

just like the Milky Way at great distances from us.

HAWKING (off screen): Hubble found that the sky was studded with distant galaxies,

giant collections of stars, far beyond our own galaxy.

JUNA (off screen): So this just shatters everything.

It shatters the small Milky Way, and it shatters the notion

that the universe can be contained in the Milky Way.

Now these distances are just getting bigger and bigger.

HAWKING (off screen): Distances are indeed becoming astronomical.

Our next one is 2.5 million light years away.

That's the distance between the Milky Way

and our nearest galaxy, Andromeda.

Now that we are talking galaxies,

it's time to introduce a new scale model.

Our next challenge is pretty simple.

If we could fit our galaxy on a smartphone

and Andromeda on a tablet, how far apart would they be?

CAT: So these are our galaxies.

JOY: This is the Milky Way,

and this is our closest galaxy, Andromeda.

(mysterious music)

HAWKING (off screen): The Milky Way is 100,000 light years side to side.

With that information,

I want my volunteers to work out the distance between the two galaxies.

CAT: So our Milky Way is 100,000 light years wide,

and Andromeda is 2.5 million light years away.

So on this scale, comparing this to this,

how far away is this galaxy?

JOY: So this is 100,000 light years across,

and there's ten times that is a million,

and so that's 2.5 million light years away.

So that would make...

-CAT (off screen): 25 of those. -JOY: 25 of these.

Shall we measure it?

One, two, three...

25.

JIM: That's it?

CAT: That's it and that's our nearest galaxy.

HAWKING (off screen): The Milky Way and Andromeda are just the start.

They are surrounded by dozens of galaxies

in the local galactic neighborhood,

and it doesn't stop there.

(exciting music)

♪ ♪

In 1990, the Hubble Space Telescope is launched.

After a decade of observations, this picture is released,

showing thousands of galaxies which stretch away into the far distance

for up to 13 billion light years.

And this is just a tiny part of the sky,

like looking at a postage stamp from 100 feet away.

JIM: My brain will never get around this.

This is gonna take me weeks, the rest of my life maybe.

HAWKING (off screen): In the desert, our volunteers have figured out

distances around the Earth to our sun.

JIM: It's like perfect right now.

HAWKING (off screen): And across our solar system.

JOY: The thing that will stick with me the most

is just how tiny we are.

HAWKING (off screen): Then out into our galaxy and beyond.

-CAT: There it is. -JOY: Oh my gosh!

CAT: In the grand scheme of things, we are infinitely small.

HAWKING: And now, back on Earth, we return to our first question.

Where are we?

We have learned that our planet is a little sphere orbiting a star...

In a modest neighborhood called the solar system.

(mysterious music)

♪ ♪

We are surrounded by a local group of a few dozen stars,

up to 50 light years distant.

♪ ♪

And we all occupy one little part of a spinning arm

in a medium-sized galaxy known as the Milky Way.

♪ ♪

Along with more than 50 others, we form a local group of galaxies,

10 million light years across.

♪ ♪

And together, we inhabit one corner of a vast collection of galaxies

known as the Laniakea Supercluster.

It's like a huge galactic city filled with hundreds of thousands of galaxies

similar to our own.

Grouped with many more millions of clusters,

they form gigantic arms which stretch through the cosmos,

the largest structures known to humanity.

(epic music)

♪ ♪

And this is just one small corner of the observable universe...

♪ ♪

Which is billions of light years, side to side.

♪ ♪

♪ ♪

Even though the distances are unimaginable,

the fact that most people can understand such a universe

does exist is a remarkable feat of the human mind.

♪ ♪

So now I hope you are beginning to realize that with a little bit of thinking,

you have the genius to figure out where we are.

Captioned by Captionmax