Why doesn the earth fall out of orbit into the sun, just as earth satellites eventually do?
Satellites in low earth orbit are not quite above all of the Earth’s atmosphere, so there is some small amount of drag from the extremely thin air. That drag force is constantly taking kinetic energy away from the satellite, so its orbit is constantly getting lower. It is different for Earth. Earth is not experiencing a continuous drag force. It does sometimes get hit by meteoroids or asteroids, but not always from the same direction, so each impact is not necessarily reducing the Earth’s kinetic energy. An orbit is not a delicate balance between gravity and centrifugal force. It is a sum total of the kinetic and potential energy of the orbiting body. Kinetic energy is energy of motion and potential energy is, in the case of an orbit, energy of height. In a perfectly circular orbit both types of energy would be constant all the time. In an elliptical orbit, the potential energy is larger, at the expense of kinetic energy, at the high point of the ellipse (aphelion for Earth) and at the
