Since he is offline I will post it. Anyone can comment on it.
The space elevator thought experiment. Imagine a elevator accelerating at 9.8m/s/s in space. You could do any experiment in that elevator and get the same results as you would get here on Earth, thus equivalence. Now shine a laser from one wall to the other. You would see nothing. Now make the elevator one light year wide. Shine the same laser from wall to wall. The laser would never make it to the other wall. It would bend and hit the floor. The laser light is not curving, rather it appears to curve. There is no force on the laser beam. There is your equivalence between gravity and acceleration. But they are not truly the same.