Is Time Travel (going backwards) Possible?

Quickleaf · Oct 17, 2012

What, you mean like John Titor?

John Titor - Wikipedia, the free encyclopedia

I'd like to believe in time travel, but it seems pretty dang unlikely.

Dire Bare · Oct 17, 2012

RSKennan said:
I agree that same-timeline backwards time travel is almost certainly impossible, but forward time travel isn't.

Isn't traveling forward through time just traveling in someone elses' past?

sabrinathecat · Oct 17, 2012

Well, one problem would be similar to the Trek Transporter: you are creating or altering a few billion molecules in order to make yourself that new body. Or you are altering their position and form.

As for killing Hitler, there was a great story about that. Short version: hit-squad goes back in time and gets caught. During the interrogation Hitler walks in, expressing his concern. One of the hit-squad breaks free, and the squad and Hitler all get killed. The top generals look at each other. "Now What?"
"Well, there is always the clone..."
"I never liked that thing--it always struck me as unstable."

And another story where the entire crowd at the crucifixion is made up of time travelers and 4 or 5 actual locals.

Yeah, the Earth spins. The Earth orbits around the sun. The Sun orbits within the Milky Way. The Milky way moves within the Galaxy. The Galaxy drifts out as the universe expands. Thus, it is impossible to come to a full and complete stop. Try that one next time you are pulled over for not stopping at a stop sign. Include the math for the officer.

Stormonu · Oct 17, 2012

Yes, but the energy involved would be ridiculous.

What is going back in time? Putting every relevant molecule except your own back where they were X seconds, minutes, hours, days or whatever.

If you could find "the center of the universe" and the equivalent of some sort of super magnet that put everything back in its place (and we're talking food that was eaten, pulling corpses out of the ground and hauling back dessicated atoms of flesh and the like...), you'd have gone back in time.

But we're talking here enough energy to reverse "the Big Bang". Unless the universe is going to collapse back in upon itself at some point*, I don't see it happening any time soon.

Perhaps someone could find a way to do a localized version - say, with a few properly placed black holes? In that case though, the fun would be in stopping the reversal of time...

* In which case, the Battlestar Galactica mantra "this has all happened before and will happen again" takes on new meaning...

Fast Learner · Oct 17, 2012

Morrus said:
No, because Hitler existed. If time travel were ever to become possible, his bedroom would have been be filled every night with thousands of would-be asssssins from the future.

Unless, say, Hitler's and the Nazis' actions serve as an essential historical lesson, preventing countless future genocides, maybe even the destruction of entire species.

Time and history are incredibly complex.

Morrus · Oct 17, 2012

Fast Learner said:
Unless, say, Hitler's and the Nazis' actions serve as an essential historical lesson, preventing countless future genocides, maybe even the destruction of entire species.

What, and every person from the invention of time travel until the end of time abides by that?

Someone · Oct 17, 2012

Morrus said:
No, because Hitler existed. If time travel were ever to become possible, his bedroom would have been be filled every night with thousands of would-be asssssins from the future.

I think you got your sci-fi wrong. Any alteration to the past, even stepping on a butterfly, results on nazins winning WWII. The nazis didn't win WWII, therefore nobody has travelled to the past.

Also, the current set of events aren't one where anyone will ever travel to the past, or else the nazis would have won WWII. So, if time travel is possible, no time machine will ever be built.

Hand of Evil · Oct 17, 2012

RSKennan said:
How do you figure? Travel near c time slows down for your frame of reference. Stop travelling near c, and bam, you're in the future. Sure, you pass through the intervening time at an accellerated rate, but you still get to the future in a shorter period of time than it would take if you had stayed "still" and waited it out.

FTL does not take you out of "now". No matter where you go...there you are.

RSKennan · Oct 17, 2012

Hand of Evil said:
FTL does not take you out of "now". No matter where you go...there you are.

Irrelevant to the topic at hand. The point is, it's time travel to the future, because all such future time travel would take some interval of subjective time that is less than the interval of subjective time that would have passed without the time travel.

Hand of Evil · Oct 17, 2012

Time is a concept created in hell, you always want more, you never have enough, you try and save it, it flys and it crawls. It is always out, is money and there is a limit to how much you get.