"This view of why objects fall reigned until the
scientific revolution that began in the
Renaissance. “Standing on the shoulders of giants” like
Kepler and
Galileo,
Isaac Newton realized that the
apple falling to the ground and the
Moon
orbiting Earth were subject to the same gravitational force. The force
was proportional to the mass of the two bodies attracting each other and
inversely proportional to the square of the distance between them.
(That is, when two bodies are twice as far apart as they were before,
the gravitational attraction is 1/[2×2], or ¼ as strong.) The force
operated between everything in the universe and explained the motions of
the Moon and the
planets very well.
Well, almost. Newtonian gravity had its triumphs. It was used to predict the location of the then unknown planet
Neptune. However, for
Mercury, the closest planet to the
Sun,
Newton’s law
was not quite as accurate in predicting the location of the planet’s
perihelion (the point in its orbit where it is the closest to the Sun)
as it was for the others. This point seemed to move about the Sun, and
the motion vexed astronomers until
Einstein introduced his theory of general
relativity in 1915, in which gravity is not a force reaching out across the universe but is a bending of
space-time around a massive object. The orbits of the planets and the apples falling to the ground follow the shape of space-time."
https://www.britannica.com/story/gravity-from-apples-to-the-universe
