Newton discovered the story of an apple falling to the ground.

From 65438 to 0666, 23-year-old Newton was a junior at Trinity College, Cambridge University. Sitting in his sister's orchard, Newton heard a familiar voice, and an apple fell on the grass with a bang. He turned quickly to watch the second apple fall to the ground. The second apple fell from the outstretched branch, bounced on the ground and lay quietly on the grass. This apple is definitely not the first apple Newton saw fall to the ground. Of course, the second apple is no different from the first one. Apples will fall to the ground, but the moon will not fall to the earth. What's the difference between an apple and the moon? The next morning, it was sunny, and Newton saw his little nephew playing with a ball. He has a rubber band tied to his hand, and a ball tied to the other end of the rubber band. He swung the ball slowly first, then faster and faster, and finally the ball was thrown straight out. Newton suddenly realized that the movements of the moon and the ball were very similar. There are two forces acting on the ball, one is the outward driving force, and the other is the tension of the rubber band. Similarly, there are two forces acting on the moon, namely, the driving force of the moon's movement and the pulling force of gravity. It is under the action of gravity that the apple will fall to the ground. Newton believed for the first time that the falling of apples, raindrops and planets orbiting the sun were all the results of gravity. It is generally believed that the laws of nature applicable to the earth are completely different from those applicable to space. Newton's law of universal gravitation gave this view a heavy blow, telling people that the laws governing nature and the universe are very simple. Newton promoted the development of the law of universal gravitation, pointing out that universal gravitation is not only the characteristic of stars, but also the characteristic of all objects. As one of the most important scientific laws, the law of gravity and its mathematical formula have become the cornerstone of the whole physics.