A couple is needed to produce the rotation of any body..

If so then what are the forces acting on earth in space if its not the suns gravitational force which leads us to centripetal force.?

• A combination of equal (in magnitude) and opposite (in direction) forces producing rotation without any transition is called a couple.
• The application of these two equal and opposite force occurs simultaneously, and only then a system of such force can be called a 'couple'.
• The resultant of couple system is only limited to the induction of rotation in the applied system and no other force dependant result is gained due to the action of couple force.

• Example: Force applied on the steering wheels and force applied on simple water taps. These forces of couple lead only to the rotation of the parts on which couple is applied.
• In our solar system, the force which keeps the planets in their orbits around the Sun is basically due to the strong gravitational force of the Sun.
• Due to the enormous mass of the Sun, it possesses enough gravitational pull to hold the entire system in a systematic orbit.
• The circular motion of planets around the Sun must not be mistaken with the concept and consequence of couple force.
• The movement of planets around the Sun does not have any 'equal in magnitude and opposite in direction' forces acting on the planets and therefore couple has no role in keeping the orbits of the solar system in regularity.