That warp in Space and Time that all known matter creates; this warp causes any other piece of matter that enters it to curve towards the generating (usually larger or greater-mass) piece of matter although it is still for all intents and purposes moving in a straight line. Earth is moving AWAY from the sun, but the curvature in space-time that the sun creates causes the earth to move AROUND the sun. The farther you get away from the gravitational event, the slower time moves. Gravity does not only effect matter but time as well.