[quote name='Eelco' timestamp='1317063684' post='4866176']
[quote name='Discount_Flunky' timestamp='1317054850' post='4866119']
[quote name='Eelco' timestamp='1317046265' post='4866066']
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What are you talking about the theory of relatively does talk about time and therefore time travel. According to the theory of relatively the faster something travels the slower time passes for that object. Also the higher the gravity around an object the slower time passes for it. Therefore if you travel faster than the speed of light, according to the equation, you would go backwards in time. The notion of time travel was originally proposed by scientist studying relatively, not science fiction writers.
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O RLLY?

Indeed, more velocity means slower passing of time; but clearly the geometry of the equation doesnt allow for the extrapolation you posit here, since time dilation as a function of v isnt even differentiable at v==c; it has an infinite slope. The correct extrapolation of ever more velocity isnt into negative time; the correct extrapolation is that the function doesnt extend into the v>c domain at all cause it completely curves away from that domain and doesnt point toward it at all.

Try and plug v > c into the formula for time dilation; you dont get a negative number as your naive extrapolation would have, but an imaginary one. An imaginary flow of time... indeed a concept more apt for science fiction writers than scientists. (or perhaps scientists looking to pry funding loose from people who never looked at the math themselves)
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When you put v = c you get 0 which means times stops for the object. The thing is though that getting anything to go the speed of light that has mass takes infinite energy, because things also get more massive the faster they go. According to the equation mass is infinite at the speed of light therefore the energy needed to go faster then the speed of light is impossible to reach. That is way the possibility of Neutrioes going faster then light is so freaky, because that implies that there is a loop hole in relativity.
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Light doesnt have a special role in relativity per se. If the neutrinos would go faster than the 'maximum' speed posited by relativity, yes, that would be freaky. Going faster than light should more likely be taken as light not reaching that maximum.

When most scientist speak of time travel mostly they speak of using something like a black hole's gravity field to make yourself live way longer then you normally would so that you can see the future.[/quote]
Sure, thats perfectly valid, but im not sure id call it time travel.

The only way to got to the past would be a worm hole, and those haven't been proven yet. Also you could only go back to the time that the worm hole was created.[/quote]Not only have they 'not been proven yet', 'they' are complete theoretical speculation; and not even theoretically sound. Nontrivial space topologies are entirely logically sound notions, but have never been observed; and to extrapolate from that to nontrivial spacetime topologies is just to assume time travel could exist using fancy words; without doing anything to solve the logical contradictions inherent in the notion, by the way.

Edit: Also just because something sounds far fetched it doesn't mean it's form or should only be mentioned in science fiction. There's a lot crazy science out there. For instance many scientists are starting to find proof that humans have a sixth sense.
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Yes, absence of proof is not proof of absence; but thats truely the only thing time travel has going for it. There are no hints or clues it could be possible in our current understanding at all; all people have done is tried to explore what would happen if you forced it into existing theoretical frameworks; and invariably ran into complete nonsense rather than an interesting new experiment to perform.

I don't think this has been pointed out before: the observation of the 1987a supernova suggests very strongly that neutrinos travel at exactly the speed of light to very large precision. So this new observation should be taken with a lot of salt.
http://scienceblogs....claim_requi.php

Well; the neutrinos did in fact come three hours earlier; a fact that we managed to rationalize by our model of how light escapes from the core; but then again, how much do we really know about that? Three hours is still very small relative to the OPERA findings, but to use the word 'exactly' seems unwarranted; I think there is a large margin of error here.

Besides, the neutrinos from OPERA are far higher energy, and the particles from the supernova have been moving through a medium which is rather different from our terrestial one, which might matter in some yet to be determined way.

That said, this is the main reason that makes me suspect that what we are to get from all this is a more accurate GPS system, not new physics.

@Eelco

You talk to me like I'm a third grade boy vainly hoping that time travels exists so I can go back and see Charlemagne or something. Many high profile scientist have put there entire careers into the theory of time travel. It IS A POSSIBILITY using today concepts of science. It's it partially feasible? I really doubt it, but it is theoretically possible. If you aren't read up on the latest theories of time travel then you can't really call yourself a science fan. The truth is stranger then fiction, that's a fact that has been proven time and time again. There are scientist who state that you can create a new universe using giant lasers for crying out loud. Science fiction has nothing on real science.

[quote name='Eelco' timestamp='1317063684' post='4866176']
[quote name='Discount_Flunky' timestamp='1317054850' post='4866119']
[quote name='Eelco' timestamp='1317046265' post='4866066']
snip

What are you talking about the theory of relatively does talk about time and therefore time travel. According to the theory of relatively the faster something travels the slower time passes for that object. Also the higher the gravity around an object the slower time passes for it. Therefore if you travel faster than the speed of light, according to the equation, you would go backwards in time. The notion of time travel was originally proposed by scientist studying relatively, not science fiction writers.
[/quote]
O RLLY?

Indeed, more velocity means slower passing of time; but clearly the geometry of the equation doesnt allow for the extrapolation you posit here, since time dilation as a function of v isnt even differentiable at v==c; it has an infinite slope. The correct extrapolation of ever more velocity isnt into negative time; the correct extrapolation is that the function doesnt extend into the v>c domain at all cause it completely curves away from that domain and doesnt point toward it at all.
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FTL travel indeed would make traveling backwards in time possible, but not because of some naive interpolation of equations.


According to the theory of relativity, if two space-time points A & B are separated by space-like distance (i.e. light cannot travel from A to B before B takes place and vice versa), the time-order of those events is not definable. I.e. there are always some reference frames, where A happens before B and some where B happens before A.

Now, if somehow something travels from A to B FTL and reaches the spatial location of B "at or before" B takes place, then in those reference frames where B takes place BEFORE A, it has traveled backwards in time.
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What do you mean, 'has travelled backwards in time'? Indeed, faster than light travel would play funny tricks with our perceptions of causality, but not with causality itself. Yes, if you go faster than light, people get to see your present state before ever getting to see your past states. You can do essentially the same thing with a good old mirror.


Of course these mere perceptions tell us nothing about the interesting question, as to how such a superluminal actor would experience time; how fast or in what manner his elementary particles would jiggle relative to eachother. He isnt going to kill his great gandfather, thats for sure, and as for what would happen to himself, our theory is entirely silent on the matter, unless you can give an interpretation to the passing of imaginary time.

For instance many scientists are starting to find proof that humans have a sixth sense.

Humans are painfully predictable and creatures of habit. Google and Facebook are mining all this data to run their own "sixth sense". Gather enough data and you can tell, with 95% confidence what the person will do. "Enough" in this case means web activity. Visa has been able to predict many decisions people make solely from purchasing history for many years now.

Human brain works through pattern matching, much of it is subconscious. While called sixth sense, it's nothing more than learned experience.

In the end, there is nothing mystical about it. Like weather. Gather enough inputs, fit them through some statistical model and you end up with a good enough prediction for next few days. Biggest change in recent years is the availability of computing power and number of sensors. Both have advanced sufficiently to the point where individuals' actions can be predicted in same way as weather.

And over long term, it does mean pre-crime becomes viable. Not through paranormal activity, but through simple math operating on vast amounts of data. Retail will also change. So will jobs. Linkedin has been promising this for a while, but we aren't there yet. Generations born today however will be providing sufficient records through entire life through which the models will be built, and eventually used for their successors. All big companies are using such models already and have been for a while. Not with breakthrough success, but sofficient to notice various trends.

According to the theory of relativity there is NO preferred reference frame

You mean that theory you intend to throw out of the window by positing a faster-than-fastest object?

...And all these descriptions are equally true descriptions of the Universe.[/quote]Assuming the axioms of relativity hold, yes. Little surprise one can derive a contradiction from inconsistenly applying ones axioms.