Five, four, three, two, one.

Hi, I'm Commander Chris Hadfield, astronaut,

spaceship commander, spacewalker, part-time musician.

I'm here today to, hopefully,

debunk some common space myths.

Here's this common perception,

that you will immediately fry to a crisp

by the unfiltered, unadulterated solar radiation

if you get sucked out of the airlock.

In truth, it's way worse than that.

In the shade in space, it's like minus 250 degrees,

but the part of you that's in the sun,

it's plus 250 degrees, at least,

so it's gonna start boiling and burning.

It's like lying on a red-hot stove

with a piece of dry ice on your back.

End, your lungs are gonna be sucked flat instantaneously.

But even worse than that, is your blood is gonna boil.

Like opening a can of pop

where suddenly all the little bubbles come out

because there's no air pressure around you.

So simultaneously, you are going to freeze, boil, burn,

get the bends and no longer be able to breathe.

Not a good way to go.

I've done two space walks and I was very thankful

to have a spacesuit around my body

so that none of those things happened to me.

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Sometimes you hear that you have to work out constantly

or you will pass out and possibly die in space.

Not true.

Livin' on a spaceship is the most lazy existence

you can imagine, you're weightless,

you do not have to lift a finger.

You don't have to hold your head up.

Your heart doesn't have to lift your blood against gravity.

You can be the laziest person in the universe in space.

But eventually, you need to come back to Earth

and if you don't exercise for your whole six months

in space, you'll sort of turn into a jellyfish.

So we do exercise two hours a day on a spaceship.

We have a resistant machine, we have a unicycle

and we have a treadmill where elastics hold us down.

Just to keep our bodies strong enough

and our bones dense enough so when we get home

we don't just fall over like a puddle.

But, you don't need to work out all the time.

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You've probably heard that space has a smell,

maybe like burnt steak or some type of barbeque.

That's true.

When you come in from a space walk,

you're surrounded by the emptiness of space.

It's sort of like the opposite of air,

there's nothing there at all.

When you quickly repressurize the hatch

and you open up the hatch and you smell

what is that lingering smell from a place

that used to be exposed to space,

the smell in there is a little bit like

that trace of a smell of gunpowder or burnt steak.

Or, to me it's sort of like brimstone,

like a witch has just been there.

It's a cool, lingering trace of a smell.

I think what it really is, is the emptiness of space,

the vacuum of space is actually pulling trace chemicals

out of the metal of the walls of the ship.

Little bits of stuff you never smell

because normally there's air pressure holding them

into the metal.

They're slowly off-gassing those tiny little trace gases

and trace particles that otherwise,

they'd never get into your nose and those are released.

Sort of that metallic, gunpowder-iron smell,

that's where the smell is comin' from.

Maybe it's not even comin' from space,

it's just sort of coming from space's affect on our ship.

Yeah, in truth, it smells a little bit like a burnt steak.

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So there's a lot of word that if you go incredibly fast,

like the speed of light,

if you could travel at the speed of light

that you won't age and despite thousands of years going by,

you'll stay the same but everybody that you know will die.

That's not really true.

Einstein called it relativity, 'cause what he meant was,

your aging will be different relative

to people's aging on Earth.

You'll still age, time will still pass for you,

but people on Earth will age at a different rate.

So that if you came back after going incredibly fast,

you would have gotten older by the amount of time

that it took for you to travel,

but people on Earth would have aged much, much faster,

they would have had a longer period of time.

Because if you get going fast enough,

your speed is sort of proportional to the time passing,

so you'll still age, you'll just age at a different rate

than people back on Earth.

Einstein did this cool thought experiment.

Imagine if you were looking at a clock,

the light from the clock is coming and hitting your eyeballs

and telling you it's 12 o'clock.

Well, imagine if you could move away from that clock

at the speed of light.

It would only say 12 o'clock

because that light and you would be moving away

from the clock at the same speed.

So for you, it would look like it always 12 o'clock forever,

you'd still be getting older

but that clock would always look like it was the same time.

The people on Earth were continuing to live,

they're not aware of you goin' the speed of light.

So, you can see that the time for you,

because of your speed, is relatively different

than the time for the people on Earth.

It's a really unusual thing to try and grasp in your head.

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What happens when something blows up in space?

If something explodes in space will it make a sound

and could a human hear it?

It's a pretty easy question to answer.

The sun is just an explosion.

The sun is the biggest explosion any of us can imagine.

It's a huge, continuous, thermonuclear explosion.

It's every atom bomb we've ever built,

way more than that, continuously exploding.

It would be the loudest thing imaginable.

It's constantly happening but we don't hear a whisper of it

and that's because there's nothing to carry the sound

from the sun to us.

Even though it's incredibly violent,

there's nowhere for the pressure of all of that sound,

all of that noise, to be carried across the emptiness

of space to shake my ear drum in here

and let me hear the sound of the sun.

It's a good thing, it'd be deafening.

So, if something explodes in space it makes a sound

but there's no way for that sound

to be carried across space so that I can hear it.

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There is this idea out there that maybe the only way

that we can really create gravity is to spin the spaceship

so that everybody is stuck to the sides

like one of those rides at the fair

where you're pinned against the wall.

And for now, that's actually true.

We don't know how to control gravity.

We have no way to control gravity.

We can sort of pretend there's gravity by spinning a ship

and everybody stick to the sides,

like a ball at the end of a string.

Maybe someday we'll figure out how to control gravity,

but for now, we have to spin the whole ship,

only in the middle will they be weightless.

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I've seen that people think

that NASA is working on warp speed

so that we can travel at the speed of light

to interstellar planets.

Warp speed is an invention of science fiction.

If we knew how to work on warp speed we would.

We don't know how to go anywhere near the speed of light,

it takes an unlimited amount of energy.

The faster you go the more energy it takes, E = MC squared.

It goes up with the square of the speed in fact.

So, how can you generate that much electricity

and what does it do to your mass?

We don't know?

We think, maybe, it's possible that you could go faster

than the speed of light,

but we sure don't understand how right now.

So, we're not really working on it

so it's not really true, we're hoping for it.

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In so many movies you see that the only way

that they survive interstellar travel,

from one star to another,

is to freeze yourself into cryo-sleep.

We don't know how to do that.

Right now when you freeze water,

which is what we're mostly made of,

our blood and everything, it goes into crystals,

it turns into ice crystals.

And if you allow the beautiful, delicate nature

of your human body to expand into ice crystals

it'll destroy the structure of you, it'll kill you.

You know, frostbite destroys it

so that you get gangrene in your hand.

You'd end up with an entirely destroyed body.

So right now, we do not know how

to successfully freeze a human body

so that it is not gonna be permanently destroyed.

Maybe we'll figure it out someday,

but all of those movies that rely on freezing the crew,

we don't know how to do that, it's not real.

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You see on the internet all the time

someone has built a balloon

and they've launch some little figurine

with a camera attached to it

where they take a picture way up high in the atmosphere,

you can see the curvature of the Earth.

It's pretty cool.

But there's some people thinking you could fly yourself

all the way up to the stratosphere

with some sort of high-altitude balloon.

You can, actually, but it's really complicated.

Felix Baumgartner, when he did his leap out of a balloon

and actually go through the speed of sound falling

down towards the Earth and landing with a parachute,

he was way up into the stratosphere.

The stratosphere starts at about six or seven miles up,

it's not all that high but then it goes on for a long way.

There's not enough air to breathe,

you kind of need to have air liner with the pressure inside

to keep your body healthy if you're that high.

But if you take the right equipment with you,

yes, we can use a balloon to lift us high enough

to get all the way up into the stratosphere.

So, if you have the right equipment, it's true.

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You've probably read somewhere on the internet

that if you go to the space station

your body will get taller, sort of expand

and it'll be painful and you're gonna be taller forever,

an irreversible experience.

It's not really true.

As I'm standing here talking right now,

gravity is pushing me down towards the floor.

Every single bone in my body

and the little bit of gristle that's inbetween the bones,

like each of the vertebra of my back,

every one has a little disc inbetween each of the bones.

And even my hip bones and my knee bones,

there's a little bit of a gap.

Well, if there's no gravity pushing me down

then those gaps can all get a tiny bit bigger.

If you stay in weightlessness for a few weeks,

in fact your body just sort of stretches

because the gap between each

of the bones gets a little bigger.

And in my case, I got about that much taller.

But you aren't really taller, you're just sort of,

temporarily, longer, but it's not permanent.

As soon as you get home and gravity starts doin'

it's work on you and grinding you down,

everything squishes back down to its launch.

So you may be, for a little while,

a little bit taller in space

and it may hurt your back a little

'cause everything's sort of gettin' pulled tight.

Some people have back pain in space as a result,

but it's not really growing, it's just sort of stretching

to your natural maximum.

Then you're gonna get squished back again

as soon as you get home.

If you do get maybe that much longer

after you've been in space for a few weeks,

think what your pants would be like?

They're gonna be high above your ankle.

And if you put on a spacesuit,

who custom fit the spacesuit to the size of your body,

well, we know it's gonna happen

so we actually plan in advance.

We fit our spacesuits knowing that the astronauts are gonna

be a little bit taller when they're in space,

or at least their bodies are gonna

be a little bit stretched.

And even the seat that protects us

when we come back to Earth, the crash seat,

so that when we hit the ground it protects us properly,

we allow for the fact that our backbones are gonna

be slightly longer when we're up there.

But your clothes, you don't really know how they fit

because you're floating around weightless,

your shirt is always floating around your body.

So you never really have a sense up there

how well your clothes fit just because there's no gravity

to pull them down and look

and see how well they're fitting on your body.

It's more like they're just floating next to you.

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I read somewhere that

on board the International Space Station bacteria multiplies

10 times faster in space.

So, if you get sick your body's gonna be like torn apart

by this ravenous strain of mutant salmonella.

Nah.

It is a different place than Earth, the space station.

We run around with little swabs all the time

to measure what microbes and what viruses,

and what little tiny bits of life might

be growing on the spaceship.

We also go around with little cleaners and wet wipes

and wipe down the whole space station all the time,

like in a hospital,

to try and keep the whole thing clean and hygienic.

And we are finding that some of those primitive forms

of life do mutate slightly differently

in the high-radiation, weightless environment

of the spaceship but no one has died yet

because of the mutant salmonella.

I'm Chris Hadfield, hopefully this has helped

to answer some of those common space myths.

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