Time travel is obviously possible. Everyone does it all the time. Just sitting around doing nothing we travel through time at a rate of 1 second per 1000 milliseconds. What’s more interesting is how we can travel through time at a different rate and how this prohibits any time paradoxes from occurring such traveling into the future to meet an older version of yourself.
As I have posted before we are always traveling at a constant speed. This is the speed of light and we cannot change that. What we can change is the direction in which we travel. Nearly all of our velocity is on the time axis but as soon as we move in the conventional sense our velocity in time slows down such that the magnitude of our velocity vector remains constant.
What this means is that every time you travel away from someone and come back you are out of synch with them in regards to time. In nearly all cases the difference is in femtoseconds and is totally irrelevant. What is be more interesting and is conceptually possible is to spend a year (in your perception) and travel two (or ten) years in time as perceived by the people you left behind.
If such a machine were built it would more properly be called a “time vehicle” than a “time machine”. To travel any interesting distance in time would require enormous amounts of energy and you cannot retrace your path or go backward in time.
Using such a machine it would be impossible to meet yourself in the future. Use of the vehicle would be exactly analogous to taking a shortcut to some geographical location your friends were traveling to. You will have traveled a shorter distance than your friends but arrive at the same location. It is not possible for you to travel both paths simultaneously.
I woke up at about 4:00 AM this morning and it took an hour or so of thinking about this before I could go back to sleep.
That’s Planet of the Apes and the Ender’s Game series right there.
We’d need much better spaceships, and they’d need hard core radiation shielding. What has been little talked about is the fact that long-term space travel, as we know it, outside the Earth’s protective magnetic field, will just plain kill ya. You can get to Mars ok, but getting back will pretty well do you in unless you can do it very fast, and any moon colony would need to be under ground.
Yeah, so, about that Goldilocks Zone thing. It would also have to include a planet with an active core, if we’re talking surface life. Then I suppose there should be a definition of a galactic Goldilocks Zone– one that avoids the really crowded areas where radiation levels are horrific.
Have I strayed far enough from the OP yet?
For such long-term space travel, we’d definately need a long-lived capitalist society, because the innovation, wealth and productivity would never be enough to support such ventures otherwise. There– right back on track.
IIRC, there are parts of quantum theory that do allow more then one path to be taken simultaneously – see “Schrodinger’s Cat.” Where that seems to fail is in the translation from theory to physical reality, but I suspect we just don’t know enough. Yet.
Damian Conway create some time travel and parallel universe jumping Perl code:
Temporally Quaquaversal Virtual Nanomachine Programming In Multiple Topologically Connected Quantum-Relativistic Parallel Spacetimes
http://blip.tv/oreilly-open-source-convention/oscon-2008-damian-conway-thoughtstream-temporally-quaquaversal-virtual-nanomachine-programming-in-multiple-t-1151669
Have fun wrapping your brain around this one!
The difference between time and space is: You can reuse space.
Nyquil would have been a short-cut to the same location.
You woke at 4:00am and did not get back to sleep for an hour. Did you fall asleep at 5:00am or 3:00am? The latter would be very, very interesting.