According to quantum physics, before the wave function is collapsed it is theoretically possible for something to be everywhere at once, even transcending time. Based on this theory, is it possible, then, that all a ghost turns out to be is a person for whom the wave function hasn't collapsed? Say if back in 1910 the wave function hadn't collapsed on your great-auntie Griselda, it would be possible to see her standing in your living room. Well, you wouldn't be seeing her, but your observation would cause the wave function to collapse and put her right back in the spot where and when she would most likely be. Of course, this doesn't explain why we don't see people from the future, and I'm sure there are plenty of holes in this idea, but I thought I'd nail this one up and let the wind whistle through it.
[This message has been edited by Oxygen (edited March 06, 2000).]
[This message has been edited by Oxygen (edited March 06, 2000).]