Time Travel

[Arthur Dent]

This is the only one that's ever made sense to me.

I suppose fate does too, but I reason that if you can go back once and see one thing happen and let it happen, you could go back again and intentionally cause something different. Maybe that's flawed somehow.

If there is fate, you do not have the free will to create this contradiction. You cannot react to a situation to change the predestined outcome because your reaction is simply part of an inexorable sequence of events that cannot be contradictory because there is no uncertainty in principle.

There is no reason why it couldn't appear to all observers that free will exists even in this type of universe because an incalculable future is indistinguishable from an undetermined one.

[M1IRONMIKE]

All the techno theories and opinions aside.....I sure would like to go back in time

[Cronos]

I remember reading somewhere that one theory posits that as soon as time travel gets invented the universe will be destroyed. (haven't read the rest of the thread, sorry if it was mentioned).

So for all our sakes, I hope it's not possible.

[ghostrunner]

This is the only one that's ever made sense to me.

I suppose fate does too, but I reason that if you can go back once and see one thing happen and let it happen, you could go back again and intentionally cause something different. Maybe that's flawed somehow.

If there is fate, you do not have the free will to create this contradiction. You cannot react to a situation to change the predestined outcome because your reaction is simply part of an inexorable sequence of events that cannot be contradictory because there is no uncertainty in principle.

There is no reason why it couldn't appear to all observers that free will exists even in this type of universe because an incalculable future is indistinguishable from an undetermined one.

Well, if you can go back intentionally then it has to be true that there is no fate. Because there's no reason you couldn't go back once and witness a certain event. Then go back again and intentionally change that event. What would stop you from doing that?

[Arthur Dent]

What would stop you from doing that?

Fate. When you went back to observe the "first" time, you'd see yourself changing the event.

[ghostrunner]

What would stop you from doing that?

Fate. When you went back to observe the "first" time, you'd see yourself changing the event.

Damn.

[AdmiralKird]

I remember reading somewhere that one theory posits that as soon as time travel gets invented the universe will be destroyed. (haven't read the rest of the thread, sorry if it was mentioned).

So for all our sakes, I hope it's not possible.

Rest at ease, if it is possible its already been invented and used somewhere else in the universe. There are probably races within our own galaxy that consider our intelligence vastly inferior. It would be akin to how we feel about the animals' intelligence relative to our own. I don't believe the human race is that smart.

[Arthur Dent]

In a physical model in which time travel is possible, someone has long since screwed up the universe.

i've made this point before. and particulaly about time machine. If one was built, we'd have seen them by now.

So I actually read the posted article, and the author makes a good point about this:

According to Einstein's picture of the universe, space and time are curved and very closely related to each other. This means that traveling through time would be much like traveling through a tunnel in space—in which case you'd need both an entrance and an exit. As a time traveler, you can't visit an era unless there's already a time machine when you get there—an off-ramp. This helps explain why we're not visited by time-traveling tourists from our own future. Futuristic humans don't drop in for dinner because we haven't yet invented time travel.

There's a similar point about theoretical faster than light travel. You could do it if you send the construction crew to the destination slower than light.

[jim]

Not only is time travel into the future possible, we are all doing it right now!!

Stasis is my only hope.

Help me, Obi Wan.

Well, when did you type this message? What time is it now? Voila, you just traveled through time. No big deal.

What can change is the rate at which you travel through time relative to an independent observer. So if you and me set our clocks at noon, and I jumped into a car and traveled at 1/2 the speed of light for a half hour according to me, my clock would say 12:30 but yours would say 1:00. Your watch is just fine, it's just that I altered the rate at which I traveled through time. Hollywood would say that I time traveled into the future, which is true but unremarkable. The unintuitive point of this is that I traveled through time "slower" than you did.

I'll have to check when I get back to work, but I'm certain I read something in our daily rag at work about how time travel in black holes is like traveling through space, and traveling through space is like time. Space and time are just different dimensions on of one thing called spacetime, and apparently the gravitational force of a black hole is so strong that it warps spacetime so much that you actually "flip" dimensions. So if you could survive a fall into one, you would find it impossible to move backward in space but you could freely move either forward or backwards in time. That makes some sense actually, because if you get caught in a black hole you are only going to be able to go one direction in space, right?

Maybe this flipping happens in worm holes and not black holes? Dunno, I'll ask someone smarter than me.

Some interesting time issues on the event horizon of a blackhole as well. If I observed you falling into a blackhole from some safe distance, what would seem like a second to you would be minutes, hours, days, or years to me. As you fell in, you would essentially be reaching a point where your travel through the time dimension virtually stopped, but of course as I'm sitting here typing this I'm flying through time at my old rate.

By the way, as bizarre as this idea sounds it was actually experimentally proven. This was done back in the 70's I think, putting synchronized atomic clocks on airplanes etc.. and flying them. Just like Einstein predicted, they "slowed" down as they were flying. I put the slowed in quotes because of course to the clocks and the people on those airplanes, relative to them there was nothing "slow" about their clock. It was just different than an observer not on the plane. Since the ratio of an airplane speed compared to the speed of light is so small, you don't really notice when you get off that flight in Tokyo that you the people on the ground actually are a little ahead of you timewise. But just because it's too small to be noticed by humans doesn't mean it doesn't exist.

So there you go, time travel happens all time and it's no big deal. Can't go backward, but theoretically you could "stop" time by traveling at the speed of light. If you could go faster than the speed of light, you would be going backward in time. But you can't.

It's all relative.


Although I wonder about some of the balls Albert hits.

[Arthur Dent]

So if you could survive a fall into one, you would find it impossible to move backward in space but you could freely move either forward or backwards in time.

Which direction is backwards in space?