Answer:
Inertia
Explanation:
Inertia is the resistance of any physical object to any change in its velocity. This includes changes to the object's speed, or direction of motion.
Assuming its "resting" is the place in the middle of the wave crest and trough, the distance between the crest and the middle line would be considered its amplitude. The height of a wave is the distance between the crest and the trough, and wavelength is the distance between two crests.
I'm almost sure your answer is going to be "Because the sun's mass creates a gravitational force that pulls earth towards it."
correct me if I am wrong.
