Gravity is one example of a certain force, being the centripetal force. This force can be analogized to the force that is keeping a rock in the whirling sling of a warrior or hunter—it is a force, not merely the leather or fabric that connects the rock and hand.

Gravity, then, is the name of this centripetal force when describing why we walk on the Earth instead of drift away, and gravity is how the moon maintains its orbit. And gravity is how the Earth (and moon) maintains its orbit around the sun.

Or at least that is how Newton conceived it.

Thank you, Great Ideas Program and Great Books of the Western World. Thank you very much.