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Possible Duplicate:
Accelerating particles to the speed of light

I have heard about atomic rockets in novels which have the capability to travel faster than light. I have also heard about fictional stories where objects capable to travel faster than light.

My question is:

Is it scientifically possible to build an instrument which can travel faster than light?

And atlast i like to clarify that whether this question suitable to your site or maybe asked in anyother stackexchange site's,usually downvote will be awarded when there is lack of research ,i am seeking answer where the research be-ginned for it,am i wrong ?

if my question is off the topic here please let me to know where can i ask this question?

Community
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BlueBerry - Vignesh4303
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  • +1 although faster-than-light questions are asked annoyingly often to physicists, curiosity like your own should be awarded, not downvoted – Rody Oldenhuis Aug 14 '12 at 08:00
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    Your article about faster-than-light neutrinos is out of date - that result turned out to be experimental error due to a faulty fibre-optic cable. – N. Virgo Aug 14 '12 at 11:20
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    @RodyOldenhuis , The issue is not necessarily the level of the question, but the fact that it is a duplicate of so many other questions about faster-than-light on this site. – Benjamin Horowitz Aug 14 '12 at 13:31
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    @BenjaminHorowitz Granted, but then the correct course of action is to link to the most representative of those duplicates, and close this question rather than downvote it (or upvote it) – Rody Oldenhuis Aug 14 '12 at 13:45
  • Also, note that neutrinos do not travel faster than light. There was a measurement error at CERN, a loose cable. – Mark M Aug 14 '12 at 16:07
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    @RodyOldenhuis There is a point of view that failure to even try to find the many existing questions on the site (not by searching, mind you, but just by looking at the similar titles that come up when you type "faster than light" into the title of the ask a question page) makes this a bad question, and indicative of a user who may continue to expect us to do his or her work. Indeed, the feeling of the Stack Exchange management has moved steadily from an initial position very much like your to a rather tough position that failure to do some basic homework is unacceptable. – dmckee --- ex-moderator kitten Aug 14 '12 at 16:43
  • @dmckee Good comment -- now the OP also knows :) – Rody Oldenhuis Aug 14 '12 at 17:12
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    @dmckee: This question is not interested in accelerating anything. I believe it is not a duplicate. – Argus Aug 14 '12 at 23:13
  • @dmckee as it maybe the duplicate of the questions but my my question was it possible or not i need to know the possibilities does it not welcomed to this commnity? – BlueBerry - Vignesh4303 Aug 20 '12 at 11:55

5 Answers5

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No, unless we find the laws of relativity to be seriously incomplete or incorrect (not very likely to happen as both SR and GR are well-tested theories.) "Building an instrument" would presumably mean that it has some finite mass and unless that rest mass is 0, you will be limited by c.

Xavier
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  • i am a computer student and i am unaware of physics laws,so please can you say it in simple terms – BlueBerry - Vignesh4303 Aug 14 '12 at 07:10
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    @vignesh In simple terms - no, you cannot. If you could, some very unexpected and very strange things would be possible (like time travel, existing in multiple places at once, effect preceeding cause, etc.) that we just don't see happening anywhere. Plus, it would mean our current understanding of the universe is completely and totally incorrect -- which is extremely unlikely, given the hundreds of millions of experiments carried out in the past 400 (or so) years, all indicating our understanding is actually pretty reliable. – Rody Oldenhuis Aug 14 '12 at 07:56
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What you should understand is that because of the way special relativity works, going faster than the speed of light would mean travelling backwards in time, so you're really asking if we can build time machines.

Another way to think about is is that while the speed of light is finite, it's indeed an infinite velocity in a very real sense: Because of time dilation, a moving clock ticks slower, and it would stop if speed of light were reached. This means that photons travel along their path instantaneously. In fact, from the point of view of the photon, there's no need to travel at all, because length contraction will have reduced the distance between start and end to zero.

Christoph
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Is it scientifically possible to build an instrument which can travel faster than light?

No, it is not.

Do remember that the stories you've been reading are fiction. I'm not sure what you've seen to suggest that such a thing might be possible in reality, but no massive object can accelerate up to the speed of light.

David Z
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It's a basic principle of relativity (both special and general) that if you measure speed locally the fastest speed you can travel is the speed of light. My favourite way to explain this is that it's a consequence of the geometry of spacetime. In fact I've just answered a question on this: Special Relativity Second Postulate

In special relativity the local invariance of the speed of light means there is absolutely no way to travel faster than light, however in general relativity this limitation no longer exists globally. It still isn't possible to travel faster than light relative to spacetime, but in GR spacetime itself can stretch and carry matter along with it, and the net effect is that FTL travel is possible - though physically unlikely.

The most commonly quoted example of this is the Alcubierre drive, varients of which crop up regularly in Science Fiction. Another is the wormhole, though the physics of wormholes are far subtler than (most) SciFi books think.

As a simple example of FTL motion, you probably know the universe is expanding and the recession speed of distant galaxies is (roughly) proportional to their distance. This means that if a galaxy is distant enough it must be moving faster than the speed of light relative to us. Note however that he distant galaxy isn't moving away from us in the sense that a bullet moves away from you when you fire a gun. Instead the spacetime in between us and the distant galaxy is expanding.

You'll probably find the Wikipedia article on faster than light travel an interesting read.

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John Rennie
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  • please review my post am i asked anything wrong here.usually downvote would be awarded if the question has lack of research i am wondering why my question was down voted? – BlueBerry - Vignesh4303 Aug 14 '12 at 10:17
  • @vignesh: I didn't downvote you (actually I've just upvoted you!) and I can't see why your question was downvoted. Possibly it's because you probably should have searched the forum before posting as there have been lots of questions in this area. Incidentally I would delete the bits about neutrinos as this turned out to be experimental error and neutrinos don't travel faster than light. – John Rennie Aug 14 '12 at 10:36
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    BTW lots of us are in the SciFi Exchange as well, and we saw your question there. That's probably why David emphasised you shouldn't take SciFi stories too literally. If you're really interested in this area read the Wikipedia article I linked, then use Google to find more info. You may end up learning general relativity - that's sort of how I got started. – John Rennie Aug 14 '12 at 10:40
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    @JohnRennie: Given 2 objects moving at some velocity v relative to one another, is it possible to determine whether they are moving or whether the space between them is expanding? – mcFreid Aug 14 '12 at 13:00
  • @mcFreid, you know, that should be a question on its own; it doesn't deserve to die as a comment – user56771 Aug 14 '12 at 13:27
  • If you are only allowed to sit on one of the two objects it's (probably) impossible. An easy way to tell if space is curved is to shine light rays through it and see what happens to the light. This is exactly what the red shift is: it's the Hubble expansion stretching the light wavelength. For weirder things like Alcubierre drives or wormholes you'd get all sorts of unusual optical effects like Einstein rings. However you probably need to shine the light sideways to detect these i.e. not directly along the line between the two objects. – John Rennie Aug 14 '12 at 13:29
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Many particles have been observed to travel faster than light. But only when the light is moving through some material that isn't a vacuum.

In order to go faster than light you can make a tradeoff between how fast you want to go and how slow you want the light to go!

FTLFTW
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    For the purposes of these types of questions "the speed of light" universally means "the speed of light in vacuum". When we wish to discuss, for instance, Cerenkov radiation, we say "the speed of light in the medium" for clarity. – dmckee --- ex-moderator kitten Aug 14 '12 at 17:16