What's the status of time travel?

Factual Questions
1

I’m wondering if anyone is seriously investigating travelling in time these days. I’m also wondering how difficult this challenge is compared to, say, “transporting” someone a la Star Trek.

Seems to me time travel would be easier. I remember reading somewhere that someone thought of “reading the grooves” of ancient pottery like an old-style LP to “hear” the sounds of what was happening when the pottery was made.

Are there any serious studies being done about the possibility of time travel that anyone knows of?

I heard recently that scientists were able to “transport” an ion or something equally ridiculous, but I’ve never heard the they were able to go back or forward one second in time.

2

Lots of theories, but all the sensible ones say that it can’t be done. There might be tiny picosecond reversals in time possible at the quantum level, which some parapsychologists think could be somehow amplified into a sort of perceptible precognition of a second or less…
but for real time travel you would need a Tipler Cylinder or a pair of Relativistically Displaced Wormholes- both of which are very difficult, if not impossible, to acheive. LINK

3

I can’t answer this again. I just answered it tomorrow. I’ll tell you what. I’ll explain it yesterday. OK?

4

Last time I checked, no one had a working flux capacitor capable of generating 1.21 gigawatts of power.

Besides that, Hawking and others have wagers on the issue, and neither him nor his peers with whom he wagered have ponied up any money yet, so it’s still undetermined.

I believe Hawking is on the ‘can’t be done’ side of the fence.

5

Theoretically it would be possible to travel back and forth to the future through some sort of quantum mechanism (forgive me if I can’t give you more details) but travelling back in time past the creation of the quantum mechanism is impossible. However, no one is even close to creating this mechanism.

My guess is that time travel will come around before Star Trek transportation, just because I have never even heard credible theories on how it would be possible to break matter up, send them at light speed through other matter and then reassemble them perfectly. And that’s just non-living matter.

Hopefully a physicist will be around to fill in the details.

6

It’s been delayed due to foreseen circumstances.

7

As far as physicists can tell with today’s knowledge time travel is possible. There is nothing in the theories we have today that prohibits it. Of course, time travel brings up so many problems that most seem to think there must be something that prohibits it…we just don’t know exactly what that something is yet.

Fortunately for our timeline time travel, even if it is truly possible, seems to be insanely difficult to pull off. Most ideas for workable time machines require negative energy (no one has a clue how that would be managed) and stupendous amounts of energy. Even if you did get your hands on the energy necessary to do this that amount of energy would likely kill anyone attempting to time travel anyway.

For all of that, as already mentioned, time travel seems to be a simpler problem than transporting people/things ala Star Trek. Star Trek transporters are likely truly impossible due to such things as the Heisenberg Uncertainty Principle which is a well established and proven concept in physics that would mess up any transporter system (there are a few other problems with transporting people as well…the Uncertainty Principle just being the main stumbling block).

8

TBA

9

Moving along nicely here at 1 second/second.

10

[nitpick]
The flux capacitor does not generate 1.21 gigawatts, it requires this much power to operate. As this is GD, you’d think we could stick to the facts.

:smiley:

11

As for why it’s generally believed to be impossible, the classic example is the “grandfather paradox”. Suppose that I invent a time machine, and go back in time to before my parents were born. I then kill one or more of my grandparents. Now, this means that my parents were never born, and therefore neither was I. But if I was never born, then who was the guy who went back and killed those folks? And if nobody did, then I do exist after all, so why can’t I do it?

Related to this is the problem of djinns, or effects without external causes. Suppose, for instance, that I’m a little more peaceful in my intentions, and go back to visit Bethoven to discuss his music with him. Of course, I bring along a copy of his famous fifth symphony. But I go back to when he was only still working on the fourth. Well, he takes a look at the sheet music I show him, and he thinks that it’s great. I give him permission to publish it as his own, and a few years later, he does. So where did that music come from?

In physics, the only known problem with time travel appears to be the amount of energy required. It’s not that it would require too much, but that it would require too little: Specifically, less than zero. I’ve seen schemes which would only require negative a few grams or so, so we’re not talking astronomical amounts, here. Nor is the time of creation of the device necessarily a factor: A Thorne wormhole time machine could only take you back to when it was first constructed, but an Alcubierre warp field, which is theoretically no more impossible than a Thorne wormhole, would not suffer from this restriction.

Finally, I should add that there are a few possibilities which could theoretically permit time travel, but which couldn’t ever be built, even theoretically. A Gödel universe, for instance (one whose spacetime has a net angular momentum) would contain closed timelike curves, as would a universe containing a maximally-extended extreme Riser-Nordstrom black hole. But in order for either of these things to exist, they need to exist from the very beginning of the universe: Neither can have a beginning point (or an ending point) in time. So it’s conceivable that we might get lucky and someday find such an object, but if we don’t, there’s nothing we can do about it.

12

Didn’t we do this just recently? Try the search function.

It’s easy to travel into the future. Hop aboard a spaceship going 99.9% the speed of light for 10 years and when you come home everyone you know will be dead. Add more 9’s and you can return to earth 1000, 10000, or as many years as you like in the future.

13

We have to agree what we mean by time travel to the future and to the past. If by time travel to the future, you mean finding a way to leave a place, do something, come back and age less than the people who stayed in the place (e.g. you have a twin brother, and when you come back, he is ten years older than you), that is perfectly possible in principle, and in a sense it is done all the time, according to General Relativity. The catch, of course, is that with current technologies, the differences among the watches are truly small.

A more challenging question is whether it is possible to travel to the past (say, meet your parents before you were born). We don’t have a proof that it is not possible, although I expect that to be the answer. The problem is that General Relativity does not seem enough to settle the question, since it is expected that quantum effects will play an importan role, and General Relativity is a purely classical (i.e. non quantum) theory.

On the other hand, we don’t have a fully developed and accepted theory of quantum gravity, so it is not clear which tools we should use to attack the problem.

In the last post of thisthread, I tried to address the question in more detail.

14

>>I can’t answer this again. I just answered it tomorrow. I’ll tell you what. I’ll explain it yesterday. OK?
There should be a law as to people making other people laugh till they’re in stitches.

15

Umm, sorry if this was part of another thread. I apologise for recreating it without searching. I’ll remember not to do it again yesterday.

But I was thinking: why isn’t time just like other physical phenomena like light, or gravity? It seems to me that if only someone could “crack” the equation, it would indeed be possible to fool with time. It is my suspicion—pathetic though it may be—that all these “phenomena” such as ghosts or UFOs can actually be attributed to someone in the future who has cracked time travel.

And I’ll bet you his name is not McFly.

16

eburacum45, brilliant link, thanks muchly.

17

Chronos:

God-dayam! This is why I post on this board.

18

I thought you’d still need a great deal of energy to make a Thorne wormhole time machine. You use your negative energy to hold open the mouth of the wormhole but now you need to drag one end of it around at relativistic speeds…probably by towing a large gravitational object nearby to attract one end of the wormhole.

So, don’t you need both a ‘little’ (less than zero) and a lot of energy to make this happen?

19

I believe Hawking cites as “proof” the fact that as far as he knows, we’ve never had any visitors from the future.

20

The Time Lords from Galleyfrea have prevented all time travel technologies to be fully achieved within this Time continuum. Time travel is limited to a few species in this continuum’s universe.