Is there zero gravity in space? It seems obvious. Astronauts float around in their space ships up there so there must not be any gravity, right?
Not so fast. Gravity is the force between any two objects that have mass. There is mass in space (you, the planets, the stars) so there must be gravity also. The moon feels the effect of the earth’s gravity. The earth feels the effect of the sun’s gravity. There is gravity in space. The effects of gravity do lessen with distance, but astronauts are only a few hundred miles above the surface of the earth. A person who weighs 160 pounds on earth would still weigh about 140 pounds at that distance. Still plenty to hit the floor, so why do they float?
They float because they are in free fall. The shuttle is falling toward the earth in a circle. As long as it doesn’t slow down it will never hit the earth though. That’s what an orbit is, it’s falling in a circle.
Zero Gravity Experiment
- Get a paper cup and poke a hole in the bottom with a pencil.
- Fill the cup with water. Water should drip out of the hole, because gravity is pulling it toward Earth.
- Now drop the cup from a high place. Watch the dripping water carefully.
- What happens while the cup is falling?
When things are free falling they are weightless. Perhaps you’ve experienced a bit of this in an elevator, or on a roller coaster or a free fall ride at the amusement park.