Why don't stars fall from the sky?

Everything in life will fall to the ground Whether it's apples and pears, or skydivers and bungee enthusiasts. Only the moon and stars are high in the sky and will not fall. What's going on here?

When the night is clear, we can see 3000 stars through the telescope, but none of them fall. 1608, the Dutch invented the telescope, which can pull the stars back and watch them at close range. Later, the Italian Galileo soon discovered that there were four stars revolving around Jupiter.

Later Galileo discovered that some stars in the universe can emit light and heat. For example, the sun is called a star, and other celestial bodies that do not emit light themselves are called planets. The sun is like a big fireball, and some stars such as the earth revolve around it. This system is also called the solar system. That is, standing in the universe, you can see a blue earth revolving around the sun.

All the stars are in their own orbits, and none of them are tied with ropes and hung in the universe. In order to explain why planets don't fall, Niu Dun discovered the law of universal gravitation. In other words, there is a force between the planets that makes him run at a certain radius and speed. Objects on the earth will return to the ground because they are attracted by the gravity of the earth.

Gravity keeps the stars in the starry sky in balance and order, but sometimes they get out of control. When they get out of control, planets will fall and become meteorites when they reach the ground. There have been several disasters in history when planets fell and hit the ground. Like the extinction of dinosaurs.

Man has made a spacewalk in a spaceship, but this is only the first small step.