Changes

Everything in the universe that has mass attracts every other thing that has mass. How much depends on the size of the masses and the distance between them. For normal objects, this pull is minute, but you can measure the pull between a very large object like the [[Earth]] and another object like you by standing on the scales. Your weight is the measure of the pull of gravity between you and the planet you are standing on. This force depends on your mass and the mass of that planet, but it also depends on your distance from the center of the planet. The further you are from the planet's center, the weaker the pull between it and your body. If you double your distance, the force is one quarter. At ten times the distance, the force is one hundredth. It drops off with the square of the distance. This is called the [[Inverse Square Law.]] <ref>http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html</ref>The force never becomes zero, no matter how far you travel.

Everything in the universe that has mass (and some things that don't like photons) attracts every other thing that has mass (and some that don't). How much depends on the size of the masses and the distance between them. For normal objects, this pull is minute, but you can measure the pull between a very large object like the [[Earth]] and another object like you by standing on the scales. Your weight is the measure of the pull of gravity between you and the planet you are standing on. This force depends on your mass and the mass of that planet, but it also depends on your distance from the center of the planet. The further you are from the planet's center, the weaker the pull between it and your body. If you double your distance, the force is one quarter. At ten times the distance, the force is one hundredth. It drops off with the square of the distance. This is called the [[Inverse Square Law.]] <ref>http://hyperphysics.phy-astr.gsu.edu/hbase/forces/isq.html</ref>The force never becomes zero, no matter how far you travel.

Astronauts in the [[space shuttle]] appear to be weightless because they are in a container which is falling. The reason the space shuttle doesn't fall to earth is that it is moving very fast sideways at the same time as it is falling, so it falls in a curve. Its speed makes its curved path the same as the Earth’s curve, so it never comes down but stays in orbit, in free fall.

Astronauts in the [[space shuttle]] appear to be weightless because they are in a container which is falling. The reason the space shuttle doesn't fall to earth is that it is moving very fast sideways at the same time as it is falling, so it falls in a curve. Its speed makes its curved path the same as the Earth’s curve, so it never comes down but stays in orbit, in free fall.