If we observe one edge of a planet to be redshifted and the opposite edge to be blue shifted, what can we conclude about the planet?
A) The planet is actually two bodies, one moving toward us, the other away from us.
B) The planet is in the process of falling apart.
C) The planet is in the process of formation.
D) The planet is rotating.
E) The planet's surface is very different from one side to the other.
Answer: D