December 21, 2006 11:15pm CST
Einstein's principle of equivalence says that you can't tell the difference between being in a stationary elevator in a gravitational field and an accelerating elevator in free space. However, if the stationary elevator is in a field that has the magnitude of that of a black hole, your temperature will increase due to Hawking radiation. If you are accelerating in free space (at a value equal to g of the black hole) your temperature will increase according to the Davies-Unruh effect. However, the Hawking formula predicts a different temperature to the Davies-Unruh formula. So, we can imagine a thought experiment where we can measure this difference, and hence tell if the elevator is accelerating or not. Does this violate Einstein's principle of equivalence? Explain.
12 Feb 07
Einstein's principal is saying that you can not tell the difference between an a force resisting an accelleration (stationary elevator in a gravitational field) and an accellerating elevator in free space. The requirement that you are in free space means that you must be at a great distance from any significant mass (strictly intergalactic distances are not enough). This is of course not a realistic situation. The area of space surrounding a black hole is about as far from free space as anywhere else.