MICROGRAVITY

All objects exert the force of gravity upon other objects.  As you sit there before your computer, reading this, you are pulling the computer towards you with gravitational force.  At the same time, the computer is pulling you towards it, with gravitational force.  Unfortunately, because of your small mass, the gravitational pull that you and the computer have towards each other is so small, that it cannot be measured or felt.

For objects to have a gravitational pull that we can measure, or feel, they must be really massive, like planets, or moons.  The law of Universal Gravitation says:

Law of Universal Gravitation The gravitational force between 2 masses M + m is proportional to the product of the masses and inversely proportional to the square of the distance r between them.

What?  You can't understand that.  Well, let's put it a little simpler.  All the Law of Universal Gravitation really says is:

Because of this law, when you move farther from the earth, or any other planet, star, or moon, the gravitational pull from that planet has less effect on you.  So, an astrounaut circling the earth will feel as if there is no gravity, even though he might have felt gravity that morning while he was sitting in his kitchen eating breakfast.

Just because that astronaut doesn't feel gravity doesn't mean that there isn't any gravity.  The reason he doesn't feel it is that he is falling around the earth at the same rate that everything close to him is.  So, if he drops something, it won't move away from him, because he and it are falling together at the same rate.

We call this condition that exists in space, where everything is falling together "microgravity."  This is made up of two words, "gravity" which we know refers to the force that pulls objects together, and "micro" which means something very small.  Together they tell us that "microgravity" is a condition where there is a very little amount of gravity.  There is still some there, but it is such a small amount that we cannot feel or measure it. 

SIMULATING MICROGRAVITY

For this month's experiment, we are going to build a microgravity simulator.  Normally, experiments this complicated are left to NASA, and large engineering companies that build things for NASA.  However, I am quite sure that you will be successful in building your own microgravity simulator in your own kitchen. 

You Will Need:

• A plastic soda bottle (empty)

• An electric drill and bit (1/8")

• A chair

• Some tape

• Some water

• A large plastic bin (storage type)

BUILDING YOUR MICROGRAVITY SIMULATOR

Follow these steps carefully.  Remember, this is a complicated piece of scientific equipment, and must be treated delicately.

1. Clean out the soda bottle from any soda residue.  Remove the label.
   

2. Using the electric drill, make a small hole (aprox. 1/8 inch diameter) in the side of the soda bottle, between 1/2 inch and 1 inch from the bottom.
   

3. Cover the hole you just made with tape.  Be sure the tape is pressed down against the bottle well, so that water cannot escape out of it.
   

SIMULATING MICROGRAVITY

To use your microgravity simulator, do the following steps.  It might be a good idea to have an assistant to observe your experiment, and report the results to you.

1. Place the plastic bin on the ground.  Place the chair next to it.
   

2. Fill the microgravity simulator 3/4 of the way full with clean water.  Tighten the cap onto the bottle so that no water may escape.
   

3. Stand upon the chair, holding the microgravity simulator in your hand.  Lay it upon its side, with the hole you drilled in it facing up.  Remove the tape, and place your finger over the hole, so that the water cannot escape.
   

4. Hold the microgravity simulator upright, at approximately head height over the plastic bin.  Remove your finger from over the hole.  Observe what happens with the water inside the simulator.
   

5. Before all the water runs out, drop the simulator, so that it lands in the bin.  Observe what happens with the water inside the simulator.
   

EXPLAINING HOW IT WORKS

When you held the simulator up, and removed your finger from the hole in the side, a stream of water should have started coming out of the hole.  This happened because gravity pulled on the water, and it sought a route to go down to the earth.  The hole provided a convenient avenue for the water to use in order to drop to the earth.

However, once you dropped the simulator, both it, and the water were falling towards the earth.  Since falling objects all fall at the same rate (see last month's science experiment) the bottle and water were falling to the earth at the same rate.

Since both the bottle and water were falling, the water should have stopped coming out of the bottle.  This is the same affect as microgravity.  Although objects in orbit around the earth are falling, they are all falling at the same rate.  Therefore, they seem as if they aren't falling at all.  Since they are orbiting around the earth at the same time they are falling, the are actually falling past the earth, and don't impact upon it.  The force of the gravity from the earth pulls on them, curving their fall into an orbit.

All satalites, rockets, and even the international space station are constantly falling.  The engineers and scientists carefully calculate their fall to insure that they have a constant orbit.  As astronauts work in space, whether in the space station, in the space shuttle, or any other place in space, they fall with the objects that they are working with.  This gives them the sense of weightlessness, even though they still have gravity pulling upon them. 

Congratulations!  You have made microgravity in your own home!