Gravitation

Kepler's laws

Towards the end of the sixteenth century, Tycho Brahe, has collected an enormous amount of information given accurate measurements of the position of the planets. Johannes Kepler, after a detailed analysis of the measures announced three laws in 1619.

1. Track every planet is an ellipse, which is the Sun in a colony.

Every second planet moves so that the line (imaginary) connecting to the Sun sweeps equal areas in equal times.

3. The squares of the periods of revolution of the planets around the sun are proportional to the cubes of their mean distances from it.

Newton's universal gravitation

Some fifty years after the laws of Kepler announced his name, Isaac Newton showed that each particle in the universe attracts every other with a force proportional to the product of their masses and inversely proportional to the square of their separation.

Therefore:

If F is the force of gravity-induced, g the acceleration of gravity, G the universal gravitational constant (6.67x10-11 N.m2/kg2), m the mass and r the distance between two objects. Then

F = G m1 m2 / R2