The Theory of Gravitation

Newton’s law of gravitation

F = G * MM/d2 …………..(1)

Eqn.(1) is called the law of gravitation

HISTORY

Geocentric Theory

Heliocentric Theory

HISTORY

Tycho Brahe

Tycho’s observatory

KEPLER’S 1st LAW

Each planet revolves around the SUN in an elliptical path with the SUN at one of the focus.

Johannes Kepler

KEPLER’S 2nd LAW

The radius vector from the sun to the planet sweeps out equal area in equal intervals of time.

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.

DYNAMICS

Galileo Galilie

ANGEL THEORY

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.

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.

PHENOMENA EXPLAINED

The earth-moon system, with tides

Why the earth is round?

Orbit of Sirius B with respect to Sirius A

Globular Star Cluster

Omega Centauri

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.

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.

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.