Originally posted by melon:
Science fiction. Assuming that the universe eventually does contract and start coming back together, why would that mean that time would reverse as well? I think time travel is complete science fiction for the only reason that I don't think time, in itself, is "recorded" whatsoever. Time is just a series of "present" moments that cease to be "present" instantaneously. Past/future...all human concepts. All we have is the present, folks, regardless of our location or the size of the universe.
Melon
First, the current scientific consensus to my knowledge is that the universe is not only expanding, but accelerating, thus making the problem of collapse and reverse time travel not something to worry about.
Also, theoretically, time travel is not science fiction. From Discover Magazine, March 2002, page 75...
"Einstein established that a limited form of travel into the future is possible. According to the special theory of relativity, rapid motion or a strong gravitational field can noticeably slow the passage of time. If you set out in a very fast spaceship at 87 percent the speed of light--161,000 miles per second--you'll see time pass twice as quickly for the rest of the world as it does for you. Press on closer to the speed of light, and you can race ahead even more rapidly into the future.
Going into the past requires a great deal more work..." It goes on to describe how that would be accomplished, theoretically.
So, just because we don't know how to do something or don't completely understand it doesn't mean it doesn't exist.
Also, I don't remember who brought it up entirely, but there is a very interesting article about the existence or non-existence of time in Discover Magazine, December 2000, entitled "From Here to Eternity." In it, physicist Julian Barbour argues several interesting points:
1. Time is an illusion, a creation of human perception.
2. If time is removed from the foundation of physics, new theories are needed to explain why humans experience the sensation of passing time.
3. "Each stage of a person's life--from fetus to young adult to senior citizen--eternally coexists with all others." "Each instant has a content, and that content is eternal." Thus, we're all immortal.
Some pretty heavy stuff to wrap your mind around, admittedly, but that's just some tidbits from the article, which does a great job explaining theories of time. It is interesting, to say the least, to try to justify Einstein's theories with Barbour's. I also recommend reading St. Augustine's Confessions, which has some pretty interesting philosophical arguments on the nature of time which are still relevant today 1700 years later. Or has it really been 1700 years?
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U2 @ The Blooming Heart