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Time travel talk

mushy

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Does the argument "If time travel were ever possible, it would have happened in the future, so we would have come back to visit ourselves already" imply that the future has already happened, therefore our lives are pre planned?
 
Well the question of "pre-planned" is hotly debated with or without time travel. Do a search here on "free will" and you'll see what I mean. One part of the argument says that if you have enough information about the current state or matter, forces, etc... then you know what will happen next. So, the next thought you have or action you take is entirely pre-determined by the current state of the universe - you have no control over any of it. No free will.

As for time travel, I do it all the time. Its just always forward, and at more or less the same rate as everyone else. ;)

And I wonder, if one could time travel, how would they know they were actually moving forward or backward in time, as opposed to traveling into another universe that just happened to be very similar?
 
That assumes that we know enough about time to have an informed theory. I doubt that we do. There are dozens of interesting theories about time by various and very qualified scientists.... and millions more by people who have no actual knowledge to base a theory on. A lot of the paradox theories assume that causality is always a factor, which it may not be.
 
I'm pretty sure if time travel will be possible someone would have come back to stop me by now.
 
time_machine.png

[We never see any time travelers because they all discover it's a huge mistake. This is also why your friend at the lab suddenly looked about a year older recently.]
http://xkcd.com/716/
 
If time travel to the past is possible, which I highly doubt, it could be that one can only travel back to a point after the machine was built. And since nobody has built a time machine yet, nobody from the past has visited. Or it could be that time travelers are very careful not to reveal themselves.
 
dtugg said:
If time travel to the past is possible, which I highly doubt, it could be that one can only travel back to a point after the machine was built.
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The TV series "7 days" had it that there was never enough power available to take journeys further into the past than 7 days.
 
If the "multiverse" notions are plausible, then perhaps time travel implies going to parallel universes as well.... This would keep the "free will" thing going.... (If I decide to go mow the lawn in this universe, then there's another where I didn't....)
But it would be rather confusing for the poor time traveler.
 
Rasmus said:
The TV series "7 days" had it that there was never enough power available to take journeys further into the past than 7 days.
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Of course, in that series, the time machine was also alien technology from the Roswell crash.
 
If you travel back in time using modern technology, to a time when that technology does not yet exist, wouldn't your time machine become useless?

Also, if you built your time machine out of a metal which was found under a mountain in 2011, and went back in time to 1970, would the metal still be under the mountain? Thus, you would be creating new matter in 1970, which is impossible.

METAL IN GROUND + METAL IN TIME MACHINE = 2X METAL
 
Yeah, there are countless variations of the violation.

Say you have worn a particular wristwatch for 10 years. Go back in time 10 years wearing the watch. Visit yourself wearing that same watch.

Your watch + your watch = 2X metal.

When these threads come up over and over again... "If time travel were ever possible..." It should just be followed with "It isn't possible."
 
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Drewbot said:
If you travel back in time using modern technology, to a time when that technology does not yet exist, wouldn't your time machine become useless?
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I've never understood this line of thinking. You're bringing your technology with you. What has it got to do with the technology available at your destination?

madurobob said:
Anything, including yourself and your clothes would represent matter/energy being created from nothing in the time in which you arrived.
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I'm sure it's some kind of violation, but it's not a violation of creation of matter and energy - you're bringing it with you. You already existed. Yes, it's a case of some matter and energy showing up where it's not supposed to be. But that matter and energy is not being created. It's being moved. If you put a soda can down on a table, there's a can there where there wasn't before, but you didn't create it there.
 
If you travel back with a time machine built out of metal, and the metal used to make the time machine is in the ground, because it hasn't been mined yet, then the matter would have to be created.

If it was not still in the ground, then it wouldn't be there in the future when you create the time machine.
 
Lithrael said:
Yes, it's a case of some matter and energy showing up where it's not supposed to be.
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Stark violation.


It's being moved.
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The wristwatch wasn't simply moved. It's exact duplication is a violation. It isn't even a duplication per se. The same metal is now in two different places in the same place.
 
Some elemental particles can "travel backwards" in time on a quantum level. Things like people and soda cans and wristwatches cannot.
 
...

You're talking about it like it was an actual thing. Whatever kind of violation backward time travel is, it's not a run of the mill 'this particle cannot exist in two places at the same time' violation. For starters it's not the exact same particle, it's an older version of the same particle. If you had an atom of plutonium, waited for it to decay, then sent it back in time, and set it next to its younger self, they wouldn't be the exact same atom existing in two places at once.

If you have it working the way you say, it doesn't work at all - you broke the game before you started playing. You don't need to say 'your time travel machine won't work anymore when you arrive,' because if the rules work like that you won't arrive, the machine won't arrive, nothing will arrive.
 
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Lithrael said:
If you had an atom of plutonium, waited for it to decay, then sent it back in time, and set it next to its younger self, they wouldn't be the exact same atom existing in two places at once.
Click to expand...


But it's the same wristwatch sitting next to itself.
 
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