CBSE Class 9 Answered

Two bodies orbits one another about the point known as center of mass.The position of center of mass depends on the mass of the bodies involved. If two bodies are of equal size the centre of mass would be at the middle of the distance between the bodies. If one body is heavier than other the center of mass would be more closer to the heavier body.In case of earth- moon system this center of mass is located at a point inside the earth because earth is much more heavier than moon. As a result both earth and moon revolve around that center of mass but because this point is located inside the earth we are unable too see the earth moving around this point but moon is at a considerable distance from this point and hence its orbital/circular motion about this point is visible to us.