Why Do Astronauts Float?
It’s not because there’s no gravity in space. The real reason is much stranger, and much cooler: they are falling!
There is gravity in space!
Many people think astronauts float because there is no gravity in space. But up where the space station flies, about 400 kilometres high, Earth’s gravity is still almost as strong as it is on the ground: about nine-tenths as strong!
Astronauts float because they are falling. The space station and everyone inside it are falling toward Earth all the time. But they are also moving sideways so fast that the ground curves away beneath them, and they keep missing it. That never-ending fall around a planet is called an orbit.
Newton’s cannonball idea
More than 300 years ago, Isaac Newton imagined a cannon on top of a very tall mountain.
- 1
Fire gently
The cannonball curves down and lands a little way off.
- 2
Fire harder
It flies farther before gravity pulls it to the ground.
- 3
Fire super fast
The ball falls, but Earth’s round surface curves away just as fast. It falls all the way around!
- 4
That’s an orbit
Satellites, the space station and even the Moon are all falling around Earth like that cannonball.
Why falling feels like floating
Have you ever felt your tummy float at the top of a roller coaster or a swing? For a moment, you and your seat are falling together, so the seat isn’t pushing up on you.
Astronauts feel that all the time. They, their food, their pens and the whole station are falling together at the same speed, so nothing presses on anything else. Scientists call it microgravity, and it makes everything drift.
Try it yourself
Ask a grown-up to poke two small holes near the bottom of a paper cup. Fill it with water over a sink or outside, and the water squirts out of the holes. Now drop the cup!
While the cup is falling, the water stops squirting. The water and the cup are falling together, so the water no longer pushes out through the holes. That’s the same reason astronauts float: everything is falling together.
Floating Facts
Water forms floating balls in orbit.
Without anything pressing it down, a blob of water pulls itself into a wobbly ball.
Candle flames are round in space.
On Earth, hot air rises and stretches a flame upward. In orbit, nothing rises, so the flame is a little blue ball.
Astronauts practise floating in airplanes.
Special planes fly up and over in a big arc. For about 20 seconds at a time, everyone inside falls together and floats.
Nothing slows you down in space.
With no air to push against, once you start moving you keep going. To stop, you have to push the other way.
The planets are orbiting too.
Every planet is falling around the Sun, moving sideways fast enough to keep missing it. Meet them in the solar system for kids.
Science words to know
- Gravity
- The pull that every object has on every other object. Earth’s gravity pulls us down.
- Orbit
- A never-ending fall around a planet or star.
- Microgravity
- When everything is falling together, so things seem weightless and float.
- Satellite
- Anything that orbits a planet, like the Moon or the space station.
Quick quiz!
0 / 31. Is there gravity on the space station?
2. Why do astronauts float?
3. In the cup experiment, why does the water stop squirting?
Questions kids ask
Why do astronauts float if there is gravity?
Because they are in free fall around Earth. They are falling, but moving sideways so fast they keep missing the ground.
Is there gravity in space?
Yes. Gravity reaches far into space. It holds the Moon in orbit around Earth and the planets in orbit around the Sun.
What is an orbit?
An orbit is the curved path of something falling around a planet or star while moving sideways fast enough to keep missing it.
Do astronauts float on the Moon?
No. Standing on the Moon, they feel its gravity, about one-sixth of Earth’s, so they bounce and hop. See the Moon landing for kids.
Spacewalk Drift
Float outside the space station and collect six lost tools. Once you start moving you keep going, so plan every push!
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