Johannes Kepler studied the motion of planets. With these experiments, Galileo showed that gravitation accelerates all objects at the same rate regardless of weight. Gravitational theory Galileo Īccording to one of his students, Galileo did a famous experiment about gravity where he dropped balls from the Tower of Pisa. Sometimes scientists use 'gravity' for the force that pulls objects towards each other, and 'gravitation' for the theory about the attraction. These words mean almost the same thing in everyday use. This pulling force is called 'gravity' and it gives weight. So the Earth pulls on every object and person, and they pull on the Earth. A person also exerts a gravitational pull, but it is so tiny it can be ignored for all practical purposes. The Earth pulls more strongly than the Moon. The pull of gravity varies according to the mass of an object.The weight of an object is variable its mass is constant.The difference can be very different on other extraterrestial objects such as the moon, and other planets. On Earth, mass and weight are the same for most purposes, though a sensitive gravimeter can detect the difference. What does not change is the amount of matter in an object. So any object on the Moon weighs 1/6th of its weight on Earth.

The Moon is much smaller and the pull of gravity on the Moon is about 1/6th that of Earth. Actually, weight changes when the pull of gravity changes. In everyday talk, we say things fall because the Earth's gravity pulls on them.

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