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Janus
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It's a commonly made misinterpretation of the equations of relativity that one would go backward in time when travelling faster than light. In fact, the equations say nothing of the sort. If we input a velocity faster than light, the time elapsed is given by an imaginary number (not a negative one). That is, a solution that has no real physical interpretation. This is why FTL travel is (usually) forbidden. The current FTL studies mentioned on other threads involve quantum probabilities, and thus avoid having weird time effects, What physicists are worried about is having to mess around with the 'light cone' theories of causality, not backward time travel.

 

 

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Wrong Again !.....

 

What part of this article did you not understand Janus?, I think perhaps you need to read it again, what makes you the authority to make such an assanine conclusion within the given "Facts"?

 

READ AGAIN:] Eureka! Scientists break speed of light.

 

Jonathan Leake, Science Editor

 

SCIENTISTS claim they have broken the ultimate speed barrier: the speed of light.

 

In research carried out in the United States, particle physicists have shown that light pulses can be accelerated to up to 300 times their normal velocity of 186,000 miles per second.

 

The implications, like the speed, are mind-boggling. On one interpretation it means that light will arrive at its destination almost before it has started its journey. In effect, it is leaping forward in time.

 

Exact details of the findings remain confidential because they have been submitted to Nature, the international scientific journal, for review prior to possible publication.

 

The work was carried out by Dr Lijun Wang, of the NEC research institute in Princeton, who transmitted a pulse of light towards a

 

chamber filled with specially treated caesium gas.

 

Before the pulse had fully entered the chamber it had gone right through it and travelled a further 60ft across the laboratory. In effect it existed in two places at once, a phenomenon that Wang explains by saying it travelled 300 times faster than light.

 

The research is already causing controversy among physicists. What bothers them is that if light could travel forward in time it could carry information. This would breach one of the basic principles in physics - causality, which says that a cause must come

 

before an effect. It would also shatter Einstein's theory of relativity since it depends in part on the speed of light being unbreachable.

 

This weekend Wang said he could not give details but confirmed:

 

"Our light pulses did indeed travel faster than the accepted speed of light. I hope it will give us a much better understanding of the nature of light and how it behaves."

 

Dr Raymond Chiao, professor of physics at the University of California at Berkeley, who is familiar with Wang's work, said he was impressedby the findings. "This is a fascinating experiment," he said.

 

In Italy, another group of physicists has also succeeded in breaking the light speed barrier. In a newly published paper, physicists at the Italian National Research Council described how theypropagated microwaves at 25% above normal light speed. The group speculates that it could be possible to transmit information faster than light.

 

Dr Guenter Nimtz, of Cologne University, an expert in the field, agrees. He believes that information can be sent faster than light and last week gave a paper describing how it could be done to a conference in Edinburgh.

 

He believes, however, that this will not breach the principle of causality because the time taken to interpret the signal would fritter away all the savings.

 

"The most likely application for this is not in time travel but in speeding up the way signals move through computer circuits," he

 

said.

 

Wang's experiment is the latest and possibly the most important evidence that the physical world may not operate according to any of the accepted conventions.

 

In the new world that modern science is beginning to perceive, sub-atomic particles can apparently exist in two places at the same time - making no distinction between space and time.

 

Separate experiments carried out by Chiao illustrate this. He showed that in certain circumstances photons - the particles of which light is made - could apparently jump between two points separated by a barrier in what appears to be zero time.

 

The process, known as tunnelling, has been used to make some of the most sensitive

 

electron microscopes.

 

The implications of Wang's experiments will arouse fierce debate. Many will question whether his work can be interpreted as proving that light can exceed its normal speed - suggesting that another mechanism may be at work.

 

Neil Turok, professor of mathematical physics at Cambridge University, said he awaited the details with interest, but added:

 

"I doubt this will change our view of the fundamental laws of physics."

 

Wang emphasises that his experiments are relevant only to light and may not apply to other physical entities. But scientists are beginning to accept that man may eventually exploit some of these characteristics for inter-stellar space travel.

 

----------------End of Article--------------

 

 

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The article you posted says nothing to counter my last post. My post was about the misconception that FTL travel would lead to backward time travel. Not about the actual feasability of FTL travel.

 

The idea of 'causality' as generally accepted in physics today says that effects cannot occur outside the light cone of their causes. FTL travel breaks this assumption because the effect of an action can be outside its light cone. But backward time travel is still not occuring; read your own post:

 

"On one interpretation it means that light will arrive at its destination almost before it has started its journey."

 

Almost. Almost. Not before, *almost* before. Backward time travel is not occuring.

 

My post did not say that FTL travel is impossible, either. I focused on Relativity, not quantum mechanics, and the efforts mentioned in your and other posts involved quantum probabilities, etc., and are not relativistic in nature.

 

 

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*Point well noted.....

 

However, understand this,Time travel or event hopping does not have the effect of erasing events, all that happens is that history no longer follows a sequential path in the forward direction. Although the events that lead you to YOUR present are sequential the sequence is no longer synchronised with a forward time reference.

 

"The following are examples of other posts from other authors"..........

 

Events are merely results of interactions between matter-energy, spacetime, and whatnot. The original substrate has nothing to do with rate -- or, if you like, we can postulate that for the substrate everything always happens at a fixed rate. What we observe as events are superficial phenomena on top of the fundamental substrate. What we observe as differential event rates in different reference frames are merely a manifestation of the difference between the reference frames -- namely, that they are traveling at a certain rate with respect to us, or that they are in a strong gravitational field, etc. Basically, think about it this way: if the speed of light is the limit, then if something is moving away from you at 0.9c, then they can only move laterally at a maximum speed of (1-0.81c^2)^0.5. This would slow down the rate of any events in a travelling frame relative to the frame of the observer.

 

actualy,(1-0.81)^0.5 c as maximum lateral speed with c outside but I get the point, you basically have a triagle of the speed vectors with c being the hypothenusa, 0.9 c the realtive speed and 0.43 c the lateral speed. If you want all the speeds then (suppose the triagle was drawn from the origin) simply let the hypothenusa vector rotate around the origin then make an other circle around the 0.9 point with radius c, then all the points from the first circle who lie within the second one are allowed speeds, each speed vector is drawn from the 0.9 point to the first circle.

 

However I don't think with this only you will find the Lorentz equations because you are only talking about speeds, you will need one more thing since Lorentz gives the equations for time and space separatly.

 

the space component was missing from the picture i.e. (Frame Dragging) (but you do have to wonder how velocities get affected strictly along the line of travel, and whether the "space contraction" cannot be derived from the extreme difficulty of forward-directed interactions. But even if this is not correct (probably not, as it is too simple and someone would have figured it out by now) -- it conveys my idea. The idea is that time is not a coordinate and not a dimension -- but rather a local property of rate.Remember Newton's first law -- objects at rest remain at rest (which is just another description of inertia.) Once you get an object going, it acquires "kinetic energy" -- but what is that energy other than resistance against being stopped? In fact, the direct proportionality of kinetic energy to inertial mass paints it squarely as a manifestation of inertia.

 

Though you'd have to concede that perspective can be measured with just one eye, and besides, we can do things like radar or sonar ranging. No, the third dimension is just as fundamental as the other two; I don't think there is a way to make it any less fundamental. In fact, if you persist with examining the precise point at which measurement takes place, then you will have to conclude that there are no dimensions at all! After all, even a single eye is an array of photoreceptors arranged in roughly 2D. If you then consider just one photoreceptor, you can only measure points -- zero-dimensional objects. The very fact that you can arrange your sensors in 2 (or even 3) dimensions is a direct indication that those 3 dimensions are fundamental dimensions that matter can traverse or occupy. Time, however, does not fit under such classification.

 

To make any kind of a time measurement, you necessarily have to rely on memory of some sort. And memory is merely a stored state contained in the present configuration of the universe. You cannot define (nor indeed conceive of) time without usage of memory. Hence, my conclusion follows that time is but a cognitive illusion generated through memory.

 

You're right that my stance clashes with many folk notions. However, and at a risk of self-aggrandisement, I would remind you that the Copernican solar system, the Newtonian revolving spherical Earth, the Einsteinian relativity of space and time, and many other things used to equally clash with folk notions. So I'd argue that what used to make sense in the past provides a poor measuring stick against what actually might be real. But history is not useless or non-existent even in my framework; it is encoded in the current state of the universe, since the "present" is a direct sequitur of the "past". Indeed, history is part of our knowledge, and knowledge is primarily useful as a starting point of induction. Hence, it still makes sense to try and learn from "past mistakes", so that "history repeating itself" can be avoided.

 

As to the gravitational/inertial mass thing -- it's darn amazing that the two are related linearly, is it not? One just has to wonder what the constant of proportionality is, and more importantly where it comes from?

 

"In his memoirs, Einstein wrote that he was disturbed that his equations contained solutions that allowed for time travel. But he finally concluded: the universe does not rotate, it expands (i.e., as in the Big Bang theory) and hence Goedel's solution could be thrown out for "physical reasons." (Apparently, if the Big bang was rotating, then time travel would be possible throughout the universe!)

 

Then in 1963, Roy Kerr, a New Zealand mathematician, found a solution of Einstein's equations for a rotating black hole, which had bizarre properties. The black hole would not collapse to a point (as previously thought) but into a spinning ring (of neutrons.) The ring would be circulating so rapidly that centrifugal force would keep the ring from collapsing under gravity. The ring, in turn, would act like the Looking Glass of Alice. Anyone walking through the ring would not die, but could pass through the ring into an alternate universe.

 

Since then, hundreds of other "wormhole" solutions have been found to Einstein's equations. These wormholes connect not only two regions of space (hence the name) but also two regions of time as well. In principle, they can be used as time machines.

 

Recently, attempts to add the quantum theory to gravity (and hence create a "theory of everything") have given us some insight into the paradox problem. In the quantum theory, we can have multiple states of any object. For example, an electron can exist simultaneously in different orbits (a fact which is responsible for giving us the laws of chemistry.) Similarly, Schrodinger's famous cat can exist simultaneously in two possible states: dead and alive. So by going back in time and altering the past, we merely create a parallel universe. We are changing someone ELSE's past by saving, say, Abraham Lincoln from being assassinated at the Ford Theater, but our Lincoln is still dead. But does this mean that we are able to jump into H.G. Wells' machine, spin the dial, and soar several hundred thousand years into England's future?

 

No. There are a number of difficult hurdles to overcome. First, the main problem is one of energy. In the same way that a car needs gasoline, a time machine needs to have fabulous amounts of energy. One either has to harness the power of a star, or to find something called "exotic" matter (which falls up, rather than down) or find a source of negative energy. (Physicists once thought that negative energy was impossible. But tiny amounts of negative energy have been experimentally verified for something called the Casimir effect, i.e., the energy created by two parallel plates.) All of these are exceedingly difficult to obtain in large quantities, at least for several more centuries!

 

Then there is the problem of stability. The Kerr black hole, for example, may be unstable if one falls through it. Similarly, quantum effects may build up and destroy the wormhole before you enter it. Unfortunately, our mathematics is not powerful enough to answer the question of stability because you need a "theory of everything" which combines both quantum forces and gravity. At present, superstring theory is the leading candidate for such a theory (in fact, it is the ONLY candidate; it really has no rivals at all.) But superstring theory, which happens to be my specialty, is still too difficult to solve completely. The theory is well-defined, but no one on earth is smart enough to solve it.

 

Interestingly enough, Stephen Hawking once opposed the idea of time travel. He even claimed he had "empirical" evidence against it. If time travel existed, he said, then we would have been visited by tourists from the future, ergo: time travel is not possible. Because of the enormous amount of work done by theoretical physicists within the last 5 years or so, Hawking has since changed his mind, and now believes that time travel is possible (although not necessarily practical.) Furthermore, perhaps, we are simply not very interesting to these tourists from the future. Anyone who can harness the power of a star would consider us to be very primitive. Imagine your friends coming across an ant hill. Would they bend down to the ants and give them trinkets, books, medicine, and power? Or would some of your friends have the strange urge to step on a few of them?

 

In conclusion, don't turn someone away who knocks at your door one day and claims to be your future great-great-great-grandchild. They may be right."

 

------------------

 

"Everything you know,...is Wrong!

 

soon we shall all discover the truth."

 

p)'i4q4

 

 

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Boy, you sure do like to cut and paste, don't you? :-)

 

Once again, your post says nothing to counter my original post. Still I see no argument to the concept that time does not reverse at superluminal velocities. The time-travel ideas in your post are all related to the tilting of light cones near anomalous objects (like ring-shaped black holes), not exceeding c.

 

I would appreciate it if you would stay on topic and not talk about the nature of time in a thread about the effects of FTL travel.

 

 

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Man Janus, what crawled up your butt and died? Lighten up, I'll bet you do this to everyone and your single? One lonely, isolated man. Tisk-tisk...

 

Here's some advice, if you choose to take it or not, is up to you. First off stop being so up tight for a minute maybe you can examine your current mental condition and see that this is your life. Are you really happy? Second, realize that there's many of us out there that believe in Time Travel and that it's real. So shut your mouth for once, because you are going to be proven wrong.

 

-Javier C.

 

 

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Let's see here,

 

Your post was in argument "about the misconception that FTL travel would lead to backward time travel. Not about the actual feasability of FTL travel".

 

I posted a reply with given examples to demonstrate a fair argument in favor of the potential for "backward time travel", as you so eloquently put it, and then in your next reply, you accuse me of going off topic and not talking about the nature of time in a thread about the effects of FTL travel.

 

Hmmmm? Now what is wrong with this picture?

 

Point well noted * There are no presentable arguments that exist within this universe, in favor of anything that goes against the comprehensive abilities, and backwards thinking, within the neural network of the mind of Janus; subsequently, any attempt to do so will result in swift argument bent on the destruction of such ideas that may be associated with the potential to prove otherwise.

 

In short, we cannot win an argument with you!.......or can we?

 

------------------

 

"Everything you know,...is Wrong!

 

soon we shall all discover the truth."

 

p)'i4q4

 

 

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TTA: Yeah, And I'm sure all the ladies are just chasing after you when they find out you think you're being manipulated by malicious folks from the future. Come on, you said it yourself - this forum is not a place for personal comments - insults or otherwise.

 

And remember, belief does not equal reality. There was a time when a large percentage of humanity believed the Earth went around the Sun...

 

Time02112: Why do you make such a big deal out of this? I made a simple post that said FTL travel does not equal backward time travel. You then posted two large quotes which did not in any way counter that idea, presented in a way that suggested they did. And then you say that I'm not making sense? Let me state it in unequivocable terms: Do you think that FTL travel would result in backward time travel? Not any other methods, I said nothing about black holes or negative energy, just FTL travel. Is that so tough to understand?

 

In fact, these are the first of your posts in which I agree with a large amount of what they say; but they're off topic. Start a new thread, this stuff could spur some interesting discussion.

 

And for God's sake, who's destroying ideas? All I said was that your posts were off topic.

 

And I don't think you've argued with me yet - you've just denied what I said. That's not an argument, it's just contradiction. Bring up a valid point and I'll concede it. The problem is, arguments take time - which is one thing you don't seem to spend much of on your replies.

 

 

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Why FTL implies time travel (tachyon pistols)

 

The entire "FTL implies time travel" bit has to do with what's sometimes called "failure of simultaneity at a distance". In addition to the effects that pop treatments of relativity mention (that is, time dilation and length contraction), relativity proposes

 

that the definition of "right now" is also different, depending on which observer's coordinate system you use.

 

This is an effect much like the revolution of deciding that the direction "up" wasn't the same everywhere, but varied from place to place on earth. With relativity, the revolutionary notion is that the direction "futureward" (or "now-ward") isn't the same everywhere, and varies with velocity.

 

We can describe this effect by idealizing FTL to be "instantaneous", and describing how the more familar time dilation implies this effect. But remember, the same points apply to any FTL speed, you just have more messy arithmetic to grind through.

 

Consider a duel (that you're observing) with tachyon pistols. Two duelists, A and B, are to stand back to back, then start out at 0.866 lightspeed for 8 seconds, turn, and fire. Tachyon pistol rounds move so fast, they are instantaneous for all practical purposes.

 

So, the duelists both set out --- at 0.866 lightspeed each relative to the other, so that the time dilation factor is 2 between them. Duelist A counts off 8 lightseconds, turns, and fires. Now, according to A (since in relativity all inertial frames are equally valid) B's the one who's moving, so B's clock is ticking at half-speed. Thus, the tachyon round hits B in the back as B's clock ticks 4

 

seconds.

 

Now B (according to relativity) has every right to consider A as moving, and thus, A is the one with the slowed clock. So, as B is hit in the back at tick 4, in outrage at A's firing before 8 seconds are up, B manages to turn and fire before being overcome by his fatal wound.

 

And since in B's frame of reference it's A's clock that ticks slow, B's round hits A, striking A dead instantly, at A's second tick; a full six seconds before A fired the original round. A classic grandfather paradox.

 

Note, this is NOT a matter of when light gets to an observer, it is NOT an optical illusion. It is due to the fact that, in SR, the question of what occurs at the "same time as" something else is observer dependent.

 

As A fired that first show at tick 8, the bullet effectively teleported from A's gun to B's back instantly --- instantly according to

 

A. But for B, who was moving at 0.866 lightspeed WRT A, B was hit in the back by the bullet 4 seconds BEFORE the bullet

 

was fired. And again note, this is NOT due to the optical illusion of lightspeed delay in viewing A's turn-and-shoot; the light from that event wouldn't reach B until MUCH later, not tick 4.

 

So we see that, each of the three observers thinks the other two have slow clocks, and that if we are allowed to move faster than a lightcone, we'll end up going "pastward" in somebody's reckoning.

 

Finally, FTL still can can bite you in non-instantaneous cases; where we're only going a "little bit" faster than light.

 

If you warp out, go to Tau Ceti, then with normal reaction engines accelerate away from earth, warp out again to go back to

 

earth, you will indeed get back before you left. (Presuming that the real-space delta-v before the warp/hyperdrive/tachyon-watziz trips was "large enough"...

 

 

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Well it is good to know that someone here has done their homework.

 

Bravo Jack D !

 

Keep Janus thinking, you are perhaps the best one here to have demonstrated an ability to match wits with Janus's objections, to accept that which most of us have "already"... with an effective means to demonstrate the "How" can it be? by injecting a form of supierior communication that even Janus cannot escape from.

 

Thank You!

 

------------------

 

"Everything you know,...is Wrong!

 

soon we shall all discover the truth."

 

p)'i4q4

 

 

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Look, I don't want to sound like I'm attacking you personally with this response, but I know it'll seem that way, because I have to present facts exactly contrary to your claims. Sorry in advance for any misinterpretation of my tone.

 

You don't apply relativistic time dilation in a reliable manner. Let me explain: A fires when he has experienced 8 seconds. From his point of view, this occurs when B has only experienced 4. But this is not the same from B's point of view.

 

B only sees A firing when, from B's point of view, A has experienced 8 seconds. Which, in B's frame, occurs 16 seconds after the start. What you did was apply A's data, which depends on his reference frame, to B's frame - a step which is invalid.

 

A thinks he's shot B when he only experienced 4 seconds, but he can't prove it without moving into B's reference frame, and thus changing his perception of time to that of B, rendering his argument invalid.

 

Now, there's still the problem of how they shoot each other. B would be shot once he had experienced 8 seconds, by a bullet which had seemingly travelled back in time from A, firing it after 16 seconds. But in fact, this is just a remnant of A and B being in different frames. If they accelerated to meet each other, the appearance of reverse time travel would cease to exist.

 

And, with a third observer, let's call her C, the backward time travel is eliminated anyway. C will see the two duelists departing at .866c in opposite directions, firing 16 seconds later (deducing this, taking into account the speed of the light she's seeing), and both dying. If you brought both A and B back to C after the duel, she would see that they had both fired at the same time and killed each other simultaneously.

 

C's reference frame is the ultimate paradox solver, as the two duelists had to begin in it and accelerate outward to reach their final velocities, and no reverse time travel occurs in it.

 

PS the lightsecond is a unit of distance, like the lightyear, equal to about 299 Mm. Not a measure of time.

 

 

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Ofcourse I don't take it as a personal attack. Let me address a few of your issues:

 

A fires when he has experienced 8 seconds. From his point of view, this occurs when B has only experienced 4. But this is not the same from B's point of view.

 

Right...as Einstein said, "Dot's Relativity"

 

B only sees A firing when, from B's point of view, A has experienced 8 seconds.

 

B didn't see A firing at all, his back was turned. :)

 

But, No. Assuming that he could see A, B would see A fire at the 2nd tick. (Since A's clock would be half of B's)

 

Which, in B's frame, occurs 16 seconds after the start.

 

B's clock is slowed, so it will be 4 seconds, not 16.

 

A thinks he's shot B when B only experienced 4 seconds

 

Right, A Knows he shot B when B was at tick 4.

 

but he can't prove it without moving into B's reference frame

 

Yes he can. Since A counted to 8 and fired, and B's clock is half as slow as A, B will get hit at tick 4.

 

Now, there's still the problem of how they shoot each other. B would be shot once B had experienced 8 seconds

 

No, 4 seconds

 

by a bullet which had seemingly travelled back in time from A, firing it after 16 seconds.

 

8 seconds...to A

 

If they accelerated to meet each other, the appearance of reverse time travel would cease to exist.

 

Because they'd bump into each other, get a nasty concussion, and half to call the duel off.

 

But really, the reverse time travel wouldn't cease to exist. Let's say Alan and Bill start a distance apart, and rush toward each other at 0.866 of c so the TD factor between them is 2.

 

Alan counts to 8 and fires. Bill gets hit on his 4th tick, gets mad, and returns fire.

 

Now to Bill, Alan has the slow clock, so Alan will get hit when his clock is half of Bill's. Since Bill's clock says 4, Alan will get hit at 2. Since Alan fired at 8, his bullet hit Bill before he fired the gun. It still works out, wether they're traveling towards, or away from each other.

 

If you brought both A and B back to C after the duel, she would see that they had both fired at the same time and killed each other simultaneously. C's reference frame is the ultimate paradox solver, as the two duelists had to begin in it and accelerate outward to reach their final velocities, and no reverse time travel occurs in it.

 

But what C says is invalid, because to A and B, C has a slowed clock (Since they both think that C is moving away from them) They will all disagree if you brought them all back, but...Dot's Relativity!

 

PS the lightsecond is a unit of distance, like the lightyear, equal to about 299 Mm. Not a measure of time.

 

Lightseconds sounds cooler, but ok, just a plain old boring second than :)

 

This can be proven in the real world too. Just replace the Tachyon pistols with that thing we were talking about that accelerates light 300 times faster than normal.

 

Than get two spaceships, and put one on each ship. We can than repeat the 'duel' experiment, in a 'lasertag' fashion.

 

The effect will be less dramatic, due to the relativly slow speed of the spacecrafts. It will probably be measured in nano or attoseconds.

 

 

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My last post was overly verbose - I think I even contradicted myself in it. Well, this'll contradict some of what I said in the other post, too. Just disregard the old post, I'll restate my (more clarified) version here. Sorry, but it took me a while to work this all out, and I posted the first one rather quickly after reading your idea.

 

First of all, this is a lot like the twins 'paradox'. The elimination of the paradox uses shifting reference frames, to determine which of the twins is time-dilated and which is not. Because the spaceship twin accelerates at the beginning of the journey, his reference frame is not as valid as the Earth twin's. The spaceship twin can't say "The Earth is moving and I'm standing still" because he is time-slowed and sees Earth et al. moving faster than him, not slower, as he would if Earth were moving. That way, when he stops again, he's experienced less time than Earth. This just goes to show that when acceleration is involved, all reference frames were not created equal.

 

So now, apply the same logic to the tachyon duel scenario. A & B depart from point C, accelerating to .866c . What does A see? Just like the spaceship twin, A is time dilated relative to point C and sees time at C proceeding at twice the speed his own time is going. When he looks at B, he sees B's time moving at the same rate as his own, because B is also slowed to .5 of C's time rate. So looking at it this way, there is no backward time travel. And this logic is already proven to have worked in the twin scenario, so it works.

 

(Glad I didn't have to resort to the full math, with finite superluminal velocities. yet.?)

 

Now, if you could formulate another expression of this problem without using acceleration (tricky to do), I might have some other comments.

 

PS I remember something about people picking on the Star Wars movies because they used 'lightyears' as a measurement of time, not distance...

 

 

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Janus,

 

Just look at your self struggling to weasel your way out of this? You come on these posts claiming to know more then the people whom your replying to, and you get proven wrong and humiliated, big time =D. A duhh duh duhhh, I swear I could almost hear your mind stuttering =).

 

Why not just take it like a man, (if you even are a man) and own up to it. Don't try and make excuses. Geesh Man, see where your crappy generalizations and arrogance got you? Take it easy next time, and don't forget to breath =).

 

Have a nice day,

 

Javier C.

 

 

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I think that Janus may occationally resort to actual Reinman math. Some other folks here are parroting misconceptions. This is my excuse to throw in an off hand speculation. If I were a betting man (and I am) I'd say that the tachyon "bullets" would arrive at both locations right on time, at 8 clicks. The rest is a bunch of foo-faa.

 

Your two spaceship example requires a third outside observer to watch both ships at the same time. All three would be in their own independent reference frame. Each would get their own independent answer, that would look just fine by their own clocks. If you wanted to watch all three, well you would need a fourth refference frame and so on. Thats why they CALL it RELATIVEty.

 

Relativety is a space travel theory and has zero to do with time travel. In my opinion.

 

 

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I don't know what the big deal is. Yes, FTL travel WILL lead to time travel. The problem is, since it depends on time dilation (Which is not time travel, as said by many here) It will cause unsolvable paradoxes. There is no Multiverse to help us out in this instance.

 

FTL is Impossible for any object consisting of mass. Yes, there is the whole bending and tunneling through space bit, but I'm talking about actual acceleration to FTL speeds.

 

Even in my own instance with the spacecrafts, a very obvious paradox arises. If you can't see it, email or post, and I'll reply as promtly as possible.

 

I would, however still like to see it carried out, just for the heck of it. We might learn something.

 

If you still don't believe why FTL leads to a form of time travel, go here:

 

http://www.physics.purdue.edu/~hinson/ftl/html/FTL_part4.html

 

They have some nice space-time diagrams and equations. Also, look for this qoute:

 

In short, for any signal sent FTL in one frame of reference, another frame of reference can be found in which that signal actually traveled backwards in time, thus violating causality in that frame.

 

I hope we can end this debate soon.

 

 

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Well, I still don't think your particular example leads to a paradox, but I think this discussion has come to its end, resolved or not. Jack D, it seems you are an intelligent man who knows his physics, and I welcome further contributions you may make to the group.

 

As for Time02112, I will no longer be reading or responding to any posts by him on any topic. I don't need to be patronized and mocked on my own free time.

 

 

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