History of Gravitational Theory - Modern Era (Origin of Gravitation)

Modern Era (Origin of Gravitation)

Gravity was described by the 11th century Indian Mathematician Bhaskaracharya in his book called Siddhantha Siromani. "Aakrishti sakthischa mahee thayaa yathkhastham guru swa abhimukham swa sakthyaa . aakrushyathe thath pathathi iti bhaathi same samanthaath kwa pathathi ayam khe" is the verse which describes that the earth attracts the solid objects in the sky by its own force towards itself. Bhaskaracharya further discusses the forces between the celestial bodies using a question: Where can the celestial bodies fall since they attract each other?

Before 1543 in De revolutionibus orbium coelestium Copernicus wrote :"...inter centrum gravitatis terrae, & centrum magnitudis..."

During the 17th century, Galileo found that, counter to Aristotle's teachings, all objects accelerated equally when falling.

In the late 17th century, as a result of Robert Hooke's suggestion that there is a gravitational force which depends on the inverse square of the distance, Isaac Newton was able to mathematically derive Kepler's three kinematic laws of planetary motion, including the elliptical orbits for the seven known planets:

"I deduced that the forces which keep the planets in their orbs must be reciprocally as the squares of their distances from the centres about which they revolve, and thereby compared the force requisite to keep the moon in her orb with the force of gravity at the surface of the earth and found them to answer pretty nearly." —Isaac Newton, 1666

So Newton's original formula was:

where the symbol means "is proportional to".

To make this into an equal-sided formula or equation, there needed to be a multiplying factor or constant that would give the correct force of gravity no matter the value of the masses or distance between them. This gravitational constant was first measured in 1797 by Henry Cavendish.

In 1907 Albert Einstein, in what was described by him as "the happiest thought of my life", realized that an observer who is falling from the roof of a house experiences no gravitational field. In other words, gravitation was exactly equivalent to acceleration. Between 1911 and 1915 this idea, initially stated as the Equivalence principle, was formally developed into Einstein's theory of general relativity.