First, the reason: related to the gravity of the earth, the escape speed of the earth (the first cosmic speed) is 7.9 km/s. When the satellite rocket we launched reaches this speed, it can leave the ground and make a circular motion around the earth. When the speed is more than 7.9KM/S and less than V2 (the second cosmic speed) 1 1.2KM/S, the orbit of the satellite around the earth will become flatter and flatter, approaching a very flat ellipse.

Second, the detailed reasons:

1. Kepler's first law (orbital law): all planets orbit the sun in elliptical orbits of different sizes, and the sun is at a focus of these ellipses;

2. Kepler's second law (also known as the law of area): the connecting line between the sun and the planet sweeps the same area in the same time;

3. Kepler's third law (also known as the periodic law): the ratio of the third power of the semi-long axis of the elliptical orbit of all planets to the second power of period of revolution is equal;

Kepler's Law 123 also applies to artificial satellites.

Under the action of gravity, there are only two situations in which a planet moves around a star or a satellite moves around a planet: an ellipse or a hyperbola, of which only an ellipse is stable. A circle is just a special case where the major axis of an ellipse is equal to the minor axis.