Have you ever wished upon a shooting star
streaking across the night sky?
Hi, I'm Jasmin Moghbeli
and I'm an astronaut living and working
aboard the space station.
I'm glad you've joined me today
to talk about friction
and how we use it in microgravity.
Are you ready to learn about
what's falling from the sky?
Let's go check it out.
Before we get to shooting stars,
let's talk about friction.
Friction is a force
that tries
to stop the movement of two things
that are touching.
It is the resistance
objects experience
while moving over a surface
or through a fluid.
It results from tiny imperfections
to the surfaces when contact happens.
There are three main types
of friction Static, kinetic, and fluid.
Static friction
and kinetic
friction occur between solid surfaces,
while fluid friction is a resistance
against a solid object
moving through liquids or gases.
When objects like
rockets, for example,
experience fluid friction in the air,
we call it air resistance.
Kinetic friction, also called
sliding friction
or dynamic friction occurs
when you have movement
between two surfaces in contact
with each other.
If you've ever moved your chair
in a classroom
by sliding it
across the floor,
you've also experienced kinetic friction.
Up here on station,
we experience friction differently
than we would back on Earth.
If I were to move a piece of equipment
or heavy cargo transfer bag,
all I do is push
and it floats wherever I need it to go.
A moving cargo transfer bag
would still experience air resistance
since we have air
aboard the space station.
We experience kinetic friction on station
when we write with a pencil
as the pencil is pushed
across the surface of the paper.
The pencil tip slides on the top
of the paper, leaving a mark.
Static friction acts on an object
when it is in contact
with another surface,
but remains at rest.
Your feet, for example,
use static friction to help you walk.
Your foot
grips the surface
so you can push yourself forward.
If you tried to do the same thing on ice,
your feet couldn't
grip the ground and you'd slip.
Most surfaces,
like the bottoms of our feet, experience
very little friction on ice.
Here on station.
We also use static friction,
but in a different way.
While we're in microgravity,
we don't use our feet to walk
like we do back on Earth.
Instead,
our legs and feet
can be used to carry things,
and our hands are used to navigate
the space station's many modules.
We also use our hands and feet
to hook onto foot restraints
and grab bars
to keep us in place
when we're conducting
scientific investigations
or recording video.
Now, about those shooting stars,
they aren't
actually stars shooting
across the night sky.
Some are meteors entrapped by Earth's
gravitational pull,
causing them to fall toward Earth
and burn up in the atmosphere,
giving off that bright streak of light.
Other shooting stars you've seen
could be our reentry spacecraft
returning to earth
or waste
we expel out of the space station.
A glowing spectacle is produced
when the gas particles in the atmosphere
and the fast reentry speed
causes the surrounding air
to rapidly compress,
which in turn causes
the surfaces of the objects
to heat up and glow.
Reentry spacecraft
are designed to withstand
that extreme heat and speed.
Once the reentry spacecraft
is at a safe altitude to do so,
parachutes are deployed
to maximize its air resistance
and slow it to a safe
landing or splashdown speed.
The space station waste and meteors
burn up in Earth's atmosphere
well before they pose a threat
to life on the surface.
Whether we're pushing chairs across
a classroom floor,
swimming in a pool on earth
or moving something on station,
friction is part of our everyday lives.
Next time you see a shooting star,
remember it could be a meteor
or something
falling from the
International Space Station.
Either way,
enjoy the marvels in our night sky.
I'm going to send it back to Earth
so you can experiment with friction
using the corresponding
classroom connections.
Thanks for exploring physics
with me today. See you soon.