Welcome to the bedtime sciences. Tonight we're going all the way
up into space to learn about the International Space Station.
Now here's my dad. Thanks, Blake, and welcome to
the Bedtime Scientist, everyone. Tonight we're going to visit a
house above the earth. Not a pretend house, a real 1.
And right now, while you're getting ready for sleep, there
are people inside it, floating, brushing their teeth while
upside down, pulling themselves through narrow hallways with
just two fingers against the wall.
And outside the window, the entire planet is turning beneath
them. Blue oceans, white clouds, dark
land freckled with light. Tonight, somewhere above you,
morning is arriving again. The house is called the
International Space Station, and it's very, very high above the
Earth. If you stacked 20 Mount Everest
on top of each other, the station would still be higher,
about 250 miles above the ground, where the sky fades from
blue into black. The station circles our planet
again and again, not once a day, but every 90 minutes.
That means by the time you fall asleep tonight, the station will
already be on the other side of the world.
It travels over oceans. It travels over deserts.
It travels over long stretches of dark water where moonlight
touches the waves, silver, white.
And inside the International Space Station, people drift
through the air as if they're underwater.
Except there's no water and no up and no down.
A sleeping bag might be attached to the wall or the floor, or
beside a window in space. Those are all the same thing.
A pen can float beside someone's shoulder for hours.
A small ball of water can drift across the room like a tiny
planet on Earth. Gravity pulls every drop of
liquid down into the shape of whatever holds it.
But up there, nothing pulls. So the water does what every
liquid wants to do. When nothing is pushing it
around, it rounds itself. Every drop of water, every tear
in space, becomes a tiny sphere, a little ball held together by
something called surface tension, the same invisible pole
that lets a droplet beat up on a leaf.
Everything aboard the station has to be clipped down, zipped
shut or attached with Velcro, otherwise it floats away.
A sock drifts into the corner. A packet of food wanders through
the air. Once, astronauts lost a spoon
for months before finally spotting it floating behind a
machine. Even though the space station is
moving faster than almost anything humans have ever built
inside it, it can feel completely calm.
That's because the station is falling around the Earth.
Imagine throwing a ball as hard as you can.
It falls back down. Now imagine throwing it so much
faster that the earth begins to curve away beneath it.
The ball still falls, but the ground keeps bending out from
under it. So instead of landing, the ball
keeps going around the earth. That's what the station is
doing. It's falling all the time, but
the Earth keeps curving out of the way at exactly the same
speed. The station moves 5 miles every
second, fast enough to cross the United States in about 10
minutes. The people inside the station
aren't just floating around for fun, They're working every day.
They study things that can only be studied in space.
They study how fire behaves when there's no up on Earth.
A flame stretches upward like a teardrop.
Because hot air rises in space with no up to rise toward, a
flame becomes a tiny blue sphere.
It burns more slowly, more evenly, and it teaches
scientists how fuel really works.
They also study the human body. Bones grow lighter when nothing
pulls down on them. Muscles relax when they no
longer have to hold a body up. Our hearts pump differently
because it no longer fights gravity.
Every astronaut who lives up there teaches Dr. something new
about what a body needs to stay strong.
They also study botany to learn how plants grow when their roots
can't tell which way is down. They study weather from above
the weather, and they study the stars without an atmosphere
blurring the view. All of this work is happening
tonight, right now, above all of us.
The space station wasn't built by 1 country.
Pieces of it were made all around the world.
Hallways from America, rooms from Russia, laboratories from
Japan, Germany and Italy, a long robotic arm from Canada,
research partners from Australia and from many other places
beyond. The people who built those
pieces spoke different languages, wrote in different
alphabets, and grew up hearing different songs.
When they were small and one by one, over many years, humans
carried those pieces into space on rockets and connected them
together above the earth. A hallway that was built in one
country had to fit perfectly into a room built somewhere
else. A wire made by one team had to
connect to a machine designed by another team across the world.
And somehow, they did it. Human beings who don't always
agree about things down here on Earth built a floating home
together in the dark. For more than 25 years now,
someone has always been living aboard the station.
Every single night since the year 2000, at least one human
being has been awake above the Earth.
No matter what was happening down below, no matter how loud
or quiet the day had been somewhere overhead, people
floated through the night together.
And because the station circles Earth every 90 minutes, the
astronauts see something that is almost impossible.
They see 16 sunrises every day. That's 16 mornings.
The darkness outside the window begins to glow blue, then gold.
Then suddenly sunlight pours across oceans and clouds beneath
them, the whole earth shining at once.
Then 45 minutes later, night comes back again.
And then another sunrise. And another 16 times.
If they treated every sunrise as a new morning, the day would
never end. So the astronauts made a
decision. Together.
They chose a bedtime. They picked 1 shared clock for
everyone aboard, no matter where they came from, no matter which
language they dreamed in. At a certain hour, the lights
dim to amber, tablets go dark, voices become low.
Someone zips into a sleeping bag attached to the wall.
Someone else takes one last look through a round window at the
earth below. The oceans beneath them look
like a swirling blue puddle. Lightning flickers inside
faraway clouds. City lights spread across
continents. Then the window shade closes,
even while another sunrise is already beginning outside.
We built a tiny village in space, a place with no up or
down, and even surrounded by endless mornings, the people
there still understood something important.
Living things need rest. Even explorers need sleep.
Even in space, night matters. And just before you drift off to
dream of sleeping bags on walls, lit windows above the earth, and
the slow blue turning of the world, I want you to know
something about you. Your mind is a wonderful thing,
so full of curiosity, and I like your mind just the way it
wonders. I'll be back again soon to
wonder more with you.