Re: Seeing into the past

There are two reasons why using a computer to predict what had happened in
the past with a high degree of certainty is incredibly difficult. For a
start, such a computer would not only be as intelligent as humans (a goal
still well away in AI research), but it would have to be many times more
intelligent. Think of movies or television shows where a detective is
trying to reconstruct a crime from evidence left at the scene. It's clearly
a very difficult task, which requires a special form of intelligence. And,
that's only for the events that occurred in one room, perhaps a day or so
earlier.

Secondly, not only would such a computer require an incredible super-human
intelligence, but it would also require huge amounts of knowledge about the
world. Consider yourself going into a kitchen and guessing what was eaten
at the last meal by observing the dirty plates, used cooking pots, the
contents of the rubbish bin, and everything. You'd probably be able to make
a fairly good guess. Any computer attempting to work out what was eaten
would need access to the same set of knowledge that you gained by observing
the kitchen.  To make predictions about anything in the last few years,
would require unbelievable amounts of knowledge. And, even if all evidence
could be gathered and entered into the computer, it still may not be
enough. E.g. if you return to our example kitchen, and I asked you to work
out what had been eaten 58 days ago, most of the evidence/knowledge would
no longer be there. The plates would have been washed, the pots cleaned,
and the rubbish bin emptied. Even if you did find a mouldy scrap of food
behind a fridge, working out if it was 58 days old (relevant) or 57 days
old (irrelevant) would probably be impossible. 

To answer your question, I think that building a computer that would be
able to tell what happened several years ago is a near certain
impossibility. However, the spread of cameras and the computers that could
record, store, and retrieve images, to the point where nearly everything is
recorded is "more possible". See the book "1984" by George Orwell for a
view on how this might affect society.