Relative Motion Because motion is determined by a reference frame that can change, motion is relative. Suppose you are relaxing on a beach. If you use your beach towel as your reference frame, you are not moving. You and the beach towel are not changing positions relative to each other. Suppose you use the sun as a reference frame instead of your beach towel. If you compare your position to the sun, you are moving quite rapidly, because you are on Earth and Earth revolves around the sun. Relative to the sun, you are moving, but relative to Earth, you are sitting still, so you don't feel as if you are in motion. See Figure 2 for another example of relative motion. CHECK POINT Draw Evidence What sources of information might you use to determine the relative motion of Earth compared to other planets in the solar system?