Here's why:
* Motion is defined as a change in position over time. If an object stays in the same location relative to a reference point, it has not changed its position and therefore is not in motion.
Example:
Imagine you're sitting in a car that is parked. You are stationary relative to the car (your reference point). Even though the Earth is rotating and moving through space, you are not moving with respect to the car.
Important Note: Motion is relative. An object can be in motion with respect to one reference point but stationary with respect to another. For example, the car mentioned above is stationary relative to you, but it is moving relative to the ground.
