Floating in Space

Floating in Space

Jump up. jump as high as you can. You can't go very high, because Earth's gravity pulls you down. On Earth gravity is strong because Earth contains a lot of material-rocks and soil, water, and metals.

If you were on the moon, you could jump much higher. The moon's gravity is much weaker than Earth's gravity. That's because the moon contains much less material. If you were on a shuttle or a space station, you could jump so high, you would float to the ceiling. Then you would float to the floor. Up you would float again; up and down, up and down. You would be floating in space. That's because gravity in a shuttle is very weak.

In the shuttle there is so little gravity, it is often called zero gravity, There is no " down" or " up. " Astronauts do not jump inside a shuttle or a space station. They move very carefully. They hold on to straps with their hands or their feet. If they keep very still, astronauts can stay wherever they are, even without a strap. But if they lift an arm or a leg, they start moving. They might hit a ceiling or a wall, or they might spin around. Wherever they land, they can stand. That means they could stand on a wall or on the ceiling. Imagine how that would make you feel.

Here on Earth astronauts are used to standing on the floor, just as you and I are. When they first find themselves standing on a wall many astronauts feel a bit dizzy. But after three or four days most astronauts get used to space, and they enjoy standing on a wall, or even a ceiling. In the shuttle or in a space station you don't feel any weight. You are weightless. Your weight on Earth is the amount of gravity pulling you down. If you weigh fifty pounds, the force of gravity on you is fifty pounds. The heavier you are, the greater the force of gravity on you. In the shuttle there is very little gravity, almost zero. So there is very little weight, close to zero. That's why it is easy to move. Also, it is easy to lift things, even if they would weigh a ton or more on Earth.

It's really too easy to move around in the shuttle. You hardly need your muscles at all, and you hardly need your bones, But to stay healthy, each of us must use our muscles every day. Astronauts do this by using exercise machines. Even so, when astronauts stay in space very long, their muscles and bones get weaker. And astronauts grow one or two inches taller because gravity isn't pulling on them. When the astronauts return to Earth, they slowly become shorter again. These changes cause backaches for many astronauts. Since there is no " down" in space, water cannot flow. That means drinking is through a straw, And using the toilet is somewhat different. The astronaut is strapped to the toilet to keep from floating free. Urine is collected and vented into space. Solid waste is dried and stored until the shuttle lands. The toilet looks and works much like one on an airplane.