OK, stop me if you heard this one, but I am without a doubt one of the top 1 million thinkers of our time, which is pretty good considering that that puts me over 5,999,000,000 mediocretins. The originality, depth of analysis, and bredth of topics I'm willing to tackle make me virtually unparalleled. Now, if only I could get a chick...
I was thinking about time travel. Surely you've seen those Back to the Future movies where Michael J. Fox remakes his present about a dozen times, as well as all of the dozens of Star Trek episodes that deal with such temporal daliances. In each of these, people travel through time and change their own present through their past actions. The problem with this is that if those changes were made, they would have been born and would have grown up in the new present and then not have known the difference. It's no wonder why people are so confused about temporal dynamics. In the following paragraphs I will explain the prinicipals behind time travel and why, as I recently discovered, time travel is impossible for very practical reasons.
First, the future is just as set as the past, we just don't know it yet. Everything in the universe from the roll of the dice to the thoughts in your head right now operate on a simple cause and effect schematic. A bumps into B so the B affects C in a specific way. If one had perfect knowledge of how everything interacted on a subatomic level they would be able to predict with 100% certainty how everything would turn out from day 1 of the universe.
That said, if one goes back in time to make changes, those changes would already have been made and the time traveler will end up creating the future they're trying to change. The Terminator and HG Well's Time Machine are pretty good examples of realistic temporal dynamics. The BEST example, ironically, is Bill and Ted's Excellent Adventure. Go rent it.
Time travel is, however, impossible for a very simple reason that everyone seems to have forgotten. In every film I've seen or book I've read, the time traveler appears in exactly the same place as before, just at a different in time. This is no doubt correct, since travelling through time instantaneously would leave your position in the other three dimensions completely unchanged.
Why, you ask? If you don't know anything about graphing of geometry, skip to the next paragraph and take my word for it. Otherwise...take a run-of-the-mill XY graph. Say you're moving 4 squares per second. You can move 4 squares along the X axis, but your Y will remain unchanged and vice versa. If you travel equally between them, you will travel four squares, but only 2 along each axis because, well, you're going diagonally. Einstein's theory of relativity implies that the same relationship exists between time and the other three dimensions with the idea that time slows and eventually stops as you approach light speed. This implies that we're moving at "light speed" down a four dimensional graph and that if we travel at light speed down one axis, movement on the other three is reduced to zero. Likewise, if we move at "light speed" down the timeline, the other dimensions cannot change and hence we will occupy the exact same spatial coordinates. That's about as specific I can get without breaking into higher math.
So you travel, say, a year into the future? Where will you end up? IN DEEP SPACE, that's where! The thing these dumbasses who write this space traveling crap always forget is that while YOU stay in exactly the same place, the rest of the universe continues to move! The Earth will whiz away at 16 miles per second! The sun will revolve around the galaxy and the galaxy will spin away and unknown speeds! Even assuming that you managed not to reappear in any space dust (and since you would be refilling a space at infinte speed and if you hit a piece of sand you'd die), you would have absolutely no clue where you were.
Therefore, any successful temporal ship would have to have extremely sophisticated navigational systems and the ability to catch up to its desired destination. Of course, that doesn't even begin to address the actual machinery required to time travel in the first place. SO, there aren't going to be any Delorians or slingshots around the sun or any crap like that. If even possible at all, it can only be achievable with short jumps. Travel too far in time and you'll never even be able to find the galaxy.
Bill and Ted's Excellent Adventure was Keanu Reeve's finest hour.
