This document discusses Newton's law of gravitation and the history of theories of gravitation, including Kepler's laws of planetary motion. It describes how Newton modified previous theories to propose that a force of gravitation exists between all masses and is proportional to the product of their masses and inversely proportional to the square of the distance between them. The document also notes how Einstein later modified Newton's law of gravitation based on his theory of relativity.

1. The Theory of Gravitation

2. Newton’s law of gravitation
F = G * MM/d2 …………..(1)
Eqn.(1) is called the law of gravitation

3. HISTORY
Geocentric Theory
Heliocentric Theory

4. HISTORY
Tycho Brahe
Tycho’s observatory

5. KEPLER’S 1st LAW
Each planet revolves around the SUN in an elliptical path with the SUN at one of the focus.
Johannes Kepler

6. KEPLER’S 2nd LAW
The radius vector from the sun to the planet sweeps out equal area in equal intervals of
time.

7. KEPLER’S 3rd LAW
The square of the periods of any two planets are proportional to the cubes of the
semi-major axis of their respective orbits.

8. DYNAMICS
Galileo Galilie
ANGEL THEORY

9. NEWTON’S MODIFICATION
1. The only way to change the motion of a body is by applying force.
2. Force is needed to change the speed or direction of motion of a body.
NEWTON’S LAW: The force acting on a body is equal to the product of the mass
of the body and acceleration produced by the force.
F = ma
Thus, the force needed to control the motion of a planet around the sun is not a force
around the sun but towards the sun.

10. NEWTON’S LAW OF
GRAVITATION
From Kepler’s 2nd law he concluded that all the forces are directed towards the sun.
Also, from Kepler’s 3rd law he analyzed that the farther the planet the weaker the
force which shows that forces are inversely proportional to the square of the distance.
Thus, he concluded that there is a force which is inversely proportional of the
distance, directed in a line between the two objects.

11. PHENOMENA EXPLAINED
The earth-moon system, with tides

12. Why the earth is round?

13. Orbit of Sirius B with respect to
Sirius A

14. Globular Star Cluster
Omega Centauri

15. ABSTRACT NATURE OF LAWS
The law of conservation of energy is a law by which many quantities can be
calculated but there is no mention why this happens.
Another example are the laws of motion.
We use mathematics to describe nature without bothering about the mechanism.

16. MECHANISM FOR
GRAVITATION
It was discovered in 1750.
1. Particles moving with very high speed in all directions and slightly absorbed.
2. When they absorbed, they give an impulse to the earth.
3. The impulse is balanced.
4. When sun is near, particles are partially absorbed by sun.
5. The earth feels a net impulse.
Limitation of the mechanism:
Earth moving around the sun would acts on particle more when they come
from front side then from back.

17. GRAVITY AND RELATIVITY
Albert Einstein modified the Newton’s law of gravitation by taking into account
the theory of relativity.
According to Newton the gravitational effect is instantaneous.
Einstein argued that nothing can be send faster than the speed of light.