AST 101 Lecture Notes - Lecture 26: Spiral Galaxy, White Dwarf, Event Horizon
Document Summary
Near a large mass light needs to escape the gravity well. A ball rolling up a hill loses kinetic energy converting it to potential energy- the ball slows. Since light can"t slow it loses only energy. Energy is shift in frequencies toward the red. Light leaving a mass will be gravitationally red shifted. This is the speed a mass must have in order to avoid being drawn back by another masses of gravity. As the probe gets closer to the event horizon, its clock begins to tick slower compared to your clock. As you watch the clock on the probe, the blue light that it was emitting begins to turn red. As it gets closer to the event horizon, all of the light from the probe gets gravitationally red shifted until it becomes undetectable. Now you jump into your spacesuit, and jump out of your spaceshift. You have a third clock that is exactly like the other two.
