gravity
Gravity and Inertia keeps the earth in orbit
the suns gravity keeps the planets in orbit
The sun's gravitational pull keeps the earth in orbit around it.
The Sun has a powerful gravitational pull. This, combined with the velocities of the planets, keeps the planets in orbit.
Gravity keeps everything in orbit around the Sun.
The force of gravity keeps the space station in orbit as well as inertia that keeps the space station moving in a straight line.
gravity keeps things in orbit
It keeps them in orbit.
the sun
gravity
gravity
The balance between the inertia of the Moon and the gravitational pull keeps the moon in orbit with Earth.