Question

how does gravity cause the planets to move in a circle around the sun?

Explanation:

Gravity is a force of attraction between two objects with mass. The Sun has a large mass, so it exerts a strong gravitational pull on the planets. This gravitational force acts as a centripetal force. A centripetal force is a force that causes an object to move in a circular path. In the case of the planets, the gravitational force from the Sun provides the necessary centripetal force for their orbital motion. Without this gravitational force (the centripetal force), the planets would move in a straight - line path (as per Newton's first law of motion, which states that an object in motion will stay in motion with a constant velocity in a straight line unless acted upon by an external force).

Answer:

Gravity from the Sun acts as the centripetal force. This centripetal force changes the direction of the planet's velocity continuously (while keeping the speed approximately constant for a circular orbit in a simple model). According to Newton's laws of motion, without this centripetal (gravitational) force, the planet would move in a straight line. So, the gravitational pull of the Sun on the planets causes them to move in a circular (or near - circular) path around the Sun.