Check in everyday this week for new posts on time travel and its perils...
Time Travel 101
Physicists take for granted that if one were to move away from the Earth at relativistic velocities and return, more time would have passed on Earth than for the traveler, so in this sense it is accepted that relativity allows "travel into the future." Any theory which would allow time travel into the past would require that issues of causality be resolved. The classic example of a problem involving causality is the "grandfather paradox."
The grandfather paradox is this: suppose a man traveled back in time and killed his biological grandfather before the latter met the traveler's grandmother. As a result, one of the traveler's parents (and by extension the traveler himself) would never have been conceived. This would imply that he could not have traveled back in time after all, which in turn implies the grandfather would still be alive, and the traveler would have been conceived allowing him to travel back in time and kill his grandfather Thus each possibility seems to imply its own negation a type of logical paradox.
Check back tomorrow for more time travel.
1) The implications of relativity on time travel is not yet worked out (duh). Given the function of speed of the observer and time, backwards time travel would be possible only if we exceed the speed of light. The fastest thing in the world can't do this, except for the theoretical particle (I think it's theoretical) tachyon which is supposed to "travel backwards in time."
ReplyDelete2) I know I'm skipping way ahead here while opening a whole new can of worms, but there's a lot of things about time travel that could completely avoid the grandfather paradox: multiverses in which the time traveler travels between universes as opposed to another point in time in the same universe. So, one who travels back in time to kill his grandfather would not be in the same universe from which he hails.
3) Some random shit I had written down... don't remember when or why, but here it is (disregard unless you're really really bored and/or you have a great interest in berating me):
in the many-world's interpretations, is there an finite number of possible universes?
say, at t0, there are X amount of possible universes that differ in the slightest unit possible (i.e., 1 quantum unit). there would be as many of these slightest difference universes as there are amount of quantum units. quantum units to the # of quantum units power then gives us all possible universes at t0.
but what about universes that move longitudinally to time? e.g., possible universe Y at t0 = possible universe XYZ at t1293. or, possible universe Y at t0 = possible universe Z at t1. there must be, then, at least one possible universe at one time that is identical to another possible universe at another time.
if we agree that time is finite, then the number of possible universes are also finite.
to-do: define time (not as our everyday understanding of time as spacetime observers but as the movement of an observer through a single possible linear universe at a reference point as it moves through all its phases).