# What experiements were done to figure out law of gravitation

1. Apr 26, 2012

### jd12345

Okay, i know people saw that earth is pulling everything towards each other and infact every other object is attracting each other. So there must be a force. But how did they discover the law i.e. F = GMm / r^2.
They must have done some experiements to figure out this law and determine the gravitational constant. What were those experiments?

2. Apr 26, 2012

### K^2

You just need to have Newton's Second and Third Laws, Kepler's Laws, and cnetripetal acceleration. You can derive gravity from these. So the experiments would be these on accelerated masses and observations of motion of the celestial bodies.

3. Apr 26, 2012

### rbj

here's a url http://www.physicsclassroom.com/class/circles/u6l3b.cfm .

the inverse-square nature is what was needed to be compatible with astronomical observation, particularly the The Law of Equal Areas . the value of G is determined by a Cavendish-like apparatus, e.g. a modern version: http://arxiv.org/abs/gr-qc/0006043v1 . the problem with determining G from acceleration of gravity on Earth is that it requires knowing Earth's mass independently.