Is There Zero Gravity in Space?

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?

This is astronaut Bruce McCandless. He is wearing an MMU backpack which allows him to maneuver in space and get back to his craft without a tether. On Earth the MMU unit is very heavy but in the weightlessness of orbit it is nothing at all. Photo by NASA, public domain.

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

  1. Get a paper cup and poke a hole in the bottom with a pencil.
  2. Fill the cup with water. Water should drip out of the hole, because gravity is pulling it toward Earth.
  3. Now drop the cup from a high place. Watch the dripping water carefully.
  4. What happens while the cup is falling?

Zero Gravity Experiment

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.

More From Layers of Learning

Here is a simple experiment that proves that objects do fall at the same rate if air resistance is taken out of the equation. Galileo was right.

Here is a simple experiment that proves that objects do fall at the same rate if air resistance is taken out of the equation. Galileo was right.

Potential and kinetic energy explained with the aid of a sled and a hill.

Potential and kinetic energy explained with the aid of a sled and a hill.

Try this balloon rocket.  It demonstrated Newton's third law.  To every action therie is an equal and opposite reaction, which also explains how an MMU can help an astronaut propel himself in space.

Try this balloon rocket. It demonstrates Newton’s third law. To every action there is an equal and opposite reaction, which also explains how an MMU can help an astronaut propel himself in space.

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