What Is Gravitation ?
Investigations in the field of physical science started with questions that people asked about the night sky.
- Why doesn’t the moon fall to earth?
- Why do the planets move across the sky?
- Why doesn’t the earth fly off into space rather than remaining in orbit around the sun?
The study of gravitation provides the answers to these and many related questions.
Gravitation is one of the four classes of interactions found in nature, and it was the earliest of the four to be studied extensively. Newton discovered in the 17th century that the same interaction that makes an apple fall out of a tree also keeps the planets in their orbits around the sun. This was the beginning of celestial mechanics, the study of the dynamics of objects in space. Today, our knowledge of celestial mechanics allows us to determine how to put a satellite into any desired orbit around the earth or to choose just the right trajectory to send a spacecraft to another planet.
The basic law that governs gravitational interactions : Gravity acts in the same fundamental way between the earth and your body, between the sun and a planet, and between a planet and one of its moons.