so maybe time doesn't fly like an arrow...

[jrtom]

...but like a magic missile (i.e., anywhere you want it to, once you've figured out how to aim it):

NYT: Remembrance of Things Future: The Mystery of Time

So many people are going to be so disappointed if it turns out that the universe does not, in fact, care (on some levels, anyway) whether we think that its processes should be logical. :)

Comments

paradox found, cont'd.

[amnesiadust.livejournal.com]

I guess the question is whether it is theoretically possible to create a sensible universe with mixed boundary conditions, in which objects can freely move in and out of a region containing closed timelike curves, and interact with objects which have world lines that only move forward in coordinate time. This is a very difficult question to answer, but my gut instincts say "bat, meet supernova." It would seem to me impossible to predict anything that would happen in such a universe, since (as has been pointed out) one would observe from that point anything that had ever, or could ever, go around the loop at once. It would simply be history (though a very confusing one), rather than an effect "percolat[ing] outwards". One's instinct is to abandon coordinate time flowing forward and to use proper time only as the measure of local physics, but since each observer in the region may have his/her own different proper time, there is no way to unify the descriptions of interactions between different observers. Maybe string theory has a different way of handling this, but it clearly will require reformatting our brains in order to get a clean install of the new physics.

Put another way: Whenever we use phrases like "before X went back in time and changed history", what we have implicitly done is to put another notion of time-moving-forward over top of the "coordinate time" which is now being bent and superseded. This sense of time is assumed to correspond to the proper time of the observer travelling backward in coordinate time, but no unique and natural such choice can be made, and any such choice would have to coincide for all conceivable time-travelling observers.

Does this make any sense at all? It makes sense to me in my head, but maybe I haven't explained my thought process very well. And no doubt there lurk in my reasoning assumptions which are being challenged by today's Deep Thinkers. Back to the work I'm getting paid to do in the meantime...