The story of Newton's discovery of gravity (mainly written later)

According to a famous story of Newton, Newton explained his law of gravity after being inspired by an apple that fell from a tree. Comics even think that the falling apple just hit Newton's forehead, and its collision made him somehow understand gravity. Newton's assistant in the Royal Mint and the husband of Newton's niece, John Condut, mentioned this in his book about Newton's life:

1666, he left Cambridge University again and went back to his mother in Lincolnshire. When he was walking in the garden, it suddenly occurred to him that gravity (making apples fall from trees to the ground) would not be confined to a limited distance around the earth, but would extend farther than usual.

He said to himself, why not be as high as the moon-if so, it will definitely affect her movement-and maybe keep her in her own orbit, so he began to calculate what effect that hypothesis would have.

The question is not whether gravity exists, but whether it can extend so far away from the earth and become a force to keep the moon in orbit. Newton found that if the force decreases inversely with the square of the distance, then the calculated lunar orbital period can be in good agreement with the real situation.

He guessed that the same force would lead to other orbital motions, so he named it "gravity". An apple tree was found in the Botanical Garden of Cambridge University, which is called the descendant of Newton's apple tree.

Reverend William Stukeley, a contemporary writer, recorded a conversation between/kloc-0 and Newton in Kensington on April 5, 726 in his Memoirs of Sir isaac newton's Life, in which Newton recalled that "the concept of gravity entered his mind a long time ago.

While he was meditating, the fall of the apple caused him to think. Why do apples always fall vertically on the ground, he thought. Why can't we walk sideways or upward, but always face the center of the earth? "

A similar statement also appeared in Voltaire's Epic Essay (1727): "Sir isaac newton was walking in his garden. He first thought of his gravitational system, and then he saw an apple fall from the tree."

These descriptions may have exaggerated Newton's own story of seeing an apple fall from the tree while sitting at home by the window.

law of universal gravitation

The law of universal gravitation is a universal law of physics which isaac newton called inductive reasoning. As a part of classical mechanics, Mathematical Principles of Natural Philosophy was first published in 1687, and was first published in175/687. When Newton's book was submitted to the Royal Society in 1686, robert hooke claimed that Newton got the inverse square law of Distance from him.

In modern language, this law makes it clear that the mass of each point attracts the mass of every other point by pointing to the force along the intersection of two points.

Force is proportional to the product of two masses and inversely proportional to the square of the distance between them. The first experiment about Newton's theory of gravitation between masses was the Cavendish experiment conducted by British scientist henry cavendish in 1798. This experiment took place11year after Newton's principle was published, about 7 1 year after his death.

Newton's law of gravity is similar to Coulomb's law, which is used to calculate the amount of electricity generated between two charged bodies. Both are inverse square law, and the acting force is inversely proportional to the square of the distance between objects. Coulomb's law is to replace the product of mass with two charges and the gravitational constant with electrostatic constant.