Question

The planetary motion is a result of inertia. But what actually made the planets move?

Answer 1

Our solar system is formed from clouds of gases revolving about a common center. Due to gravity more mass accumulated at the center and smaller and bigger chunks of condensed gases revolving around the concentrated mass at the center. These chunks of condensed gases grew bigger and formed planets and satellites. Thus, the motion of the gases during the formation of the solar system is still in continuation in form of motion of planets and satellites around the sun.

The basic reason behind this motion is gravitational pull of the sun on the planets and the satellites.