It just occurred to me that, perhaps, this is what the Emperor did when he blew up at the end of ROTJ. A last-ditch attempt to take vengeance on the father-son tag-team that had done him in. Maybe as he was falling he formed, created, and set off a thought bomb, which would explain the explosion, and possibly also why Vader was a hell of a lot weaker after he threw the Emperor over the side of the shaft. (Though admittedly, it's more likely that the Emperor's lightning zapped out his life support relays. But, IIRC, we don't see Vader collapse against the railing until after the Emperor blows up real good....)
Ah, well. It's just a thought. I know Lucas didn't have 'thought bombs' in mind when he directed that scene.
