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

A famous story of Newton said that Newton explained his law of gravity after being inspired by an apple falling from a tree. The comic works even think that the falling apple just hit Newton's forehead, and its collision made him somehow understand gravity. John Conduit, Newton's assistant at the Royal Mint and the husband of Newton's niece, mentioned this in his writings about Newton's life:

In p>1666, he left Cambridge University again and returned to his mother who lived in Lincolnshire. When he was walking in a garden, it suddenly occurred to him that gravity (which makes an apple fall from a tree to the ground) would not be confined to a limited distance around the earth, but would extend to a farther place 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 orbit, so he began to calculate what effect that assumption would have.

the question is not whether gravity exists, but whether it can extend so far 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, the calculated lunar orbital period can be in good agreement with the real situation.

He guessed that the same force also led to other orbital motions, so he named it "gravity". An apple tree, known as the descendant of Newton's apple tree, was found in the Botanical Garden of Cambridge University

In his Memoirs of Sir isaac newton, the contemporary writer William stukeley recorded a conversation with Newton in Kensington on April 15th, 1726. In this conversation, Newton recalled that "once upon a time, the concept of gravity entered his mind.

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

a similar statement also appeared in Voltaire's Essay on Epic Poetry》(1727): "Sir isaac newton was walking in his garden, and 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 a tree while sitting by the window at home (Woolsop Manor).

law of universal gravitation

the law of universal gravitation is a general physical law that isaac newton called inductive reasoning. As a part of classical mechanics, it was first published in Mathematical Principles of Natural Philosophy in 1687, and was first published on July 5, 1687. 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.

according to modern Chinese, 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 line of two points.

the force is directly 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 universal gravitation between masses was the Cavendish experiment conducted by British scientist Henry cavendish in 1798. This experiment took place 111 years after the publication of Newton's Principles and about 71 years 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, in which 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.