Spacetime Diagram why Superluminal signalling implies time travel
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From: Tailor on 31 May 2010 21:16 Hi, I know that in Special Relativity, Superluminal signalling implies time travel. I've been looking in the net the past hour for a good spacetime diagram of how superluminal signalling can become in another frame backward travelling time. Can someone share a very good url about it (not the normal SR stuff but specifically about this superluminal thing)? Thanks.
From: Androcles on 1 Jun 2010 03:34 "Tailor" <tailoreys(a)gmail.com> wrote in message news:cc18c758-7c51-4767-b91d-219080151173(a)40g2000pry.googlegroups.com... | Hi, | | I know that in Special Relativity, Superluminal signalling implies | time travel. I've been looking in the net the past hour for a good | spacetime diagram of how superluminal signalling can become in another | frame backward travelling time. Can someone share a very good url | about it (not the normal SR stuff but specifically about this | superluminal thing)? Thanks. | Sure: http://www.androcles01.pwp.blueyonder.co.uk/Algol/Algol.htm Superluminal light, not the normal SR thing. Oh wait, you wanted a spacetime diagram: http://www.androcles01.pwp.blueyonder.co.uk/Doolin'sStar.GIF
From: Sam Wormley on 1 Jun 2010 14:25 On 5/31/10 8:16 PM, Tailor wrote: > Hi, > > I know that in Special Relativity, Superluminal signalling implies > time travel. Whatever gave you such an idea--The fabric of spacetime puts a speed limit on communications. Quantum entanglement cannot be used for *arbitrary communications* over arbitrary distances which remains constrained by the speed of light. Neither phase velocity nor group velocity can be used for *arbitrary communications* over arbitrary distances which remains constrained by the speed of light. A Mathematical Theory of Communication by Claude E. Shannon http://cm.bell-labs.com/cm/ms/what/shannonday/paper.html http://cm.bell-labs.com/cm/ms/what/shannonday/shannon1948.pdf Claude E. Shannon http://scienceworld.wolfram.com/biography/Shannon.html
From: G. L. Bradford on 2 Jun 2010 00:28 "Tailor" <tailoreys(a)gmail.com> wrote in message news:cc18c758-7c51-4767-b91d-219080151173(a)40g2000pry.googlegroups.com... > Hi, > > I know that in Special Relativity, Superluminal signalling implies > time travel. I've been looking in the net the past hour for a good > spacetime diagram of how superluminal signalling can become in another > frame backward travelling time. Can someone share a very good url > about it (not the normal SR stuff but specifically about this > superluminal thing)? Thanks. ==================== Why travel backward in time when you start out back in time, to way back in time, relative to your OBSERVATION of your destination? It isn't a matter of traveling back in time as you travel forward in the observable universe, it's a matter of climbing out of the hole of all those non-local histories globally showing (anything at one light second's distance being minus one second in time to the observer's or traveler's zero locally. Thus to get to the place there-now the traveler has to travel one light second, or time travel minus one second to zero, even if it takes only a tenth of second to do the job, which is not superluminal -- not faster than light -- travel: It is a travel minus one second to zero observed -- thus plus one second -- plus the one tenth of a second travel time clocked by the traveler, for a grand total of one and one tenth of a second observed to travel one light second's distance (a travel less than the speed of light)). Of course if the traveler could observe his departure point one light second away quick enough, he would observe it for a time before he left it (he would observe it as just another of the [observable] universe's innumerable many histories). Of course the [observed] departure point would not be the real-time departure point [unobservably] one second forward in time of the [observed] departure point ONE LIGHT SECOND AWAY and minus one second from his own time observed. Meaning that in fact what he observes is history and does not actually exist as part of the up-to-date UNOBSERVABLE universe (he does not in fact exist in the two places at once -- at his arrival point and departure point at the same time, regardless of what he observes momentarily from ONE LIGHT SECOND AWAY). Superluminal travel is not only a physical impossibility, but as I point out above it's utterly unnecessary....utterly meaningless. GLB ===================
From: spudnik on 2 Jun 2010 15:39
it's just a misnomer; "travel 'in' time" is "travel" in one dimension; travel requires time! Minkowski's God-am pants didn't help, at all. thusNso: yes, but your "dynamical 3-space" is just a euphemism; others, however, choose to believe in an absolute vacuum -- and that really sucks! > my papers mainly deal with simpler cases of non-turbulent flow. thusNso: the introduction sounded good; I'll read it, later. http://research.physics.illinois.edu/qi/photonics/papers/QuantumCakes... thusNso: ladies & germs, nature abhors a refractive index equal to 1.0000..., and I thank Pascal for his dyscovery of it, and damn Einstein for his damn "photon" reification of Newton's God-am corpuscle -- so, let's get on with it! thusNso: Michelson and Morely did not get no results, as has been amply demonstrated by follow-on researchers, and documented by "surfer" herein. Minkowsi's silly statement about time & space --then, he died-- has been hobbling minds, ever since; it is just a phase-space, clearly elaborated with quaternions (and the language of "vectors" that Hamilton created thereby .-) thusNso: clearly, NeinStein#9 doesn't know what *mathematica* is; it's not just a "visualization programme" from the Wolframites! http://math.ucr.edu/home/baez/physics/General/LightMill/light-mill.html Dear Editor; The staff report on plastic bags, given when SM considered a ban, before, refused to list the actual fraction of a penny, paid for them by bulk users like grocers & farmers at markets. Any rational EIR would show that, at a fraction of a gram of "fossilized fuel (TM)" per bag, a) they require far less energy & materiel than a paper bag, and b) that recycling them is impractical, beyond reusing the clean ones for carrying & garbage, as many responsible folks do. As I stated at that meeting, perhaps coastal communities *should* ban them -- except at farmers' markets -- because they are such efficient examples of "tensional integrity," that they can clog stormdrains by catching all sorts of leaves, twigs & paper. But, a statewide ban is just too much of an environmental & economic burden. --Stop British Petroleum's capNtrade rip-off; tell your legislators, a tiny tax on carbon could achieve the result, instead of "let the arbitrageurs/hedgies/daytrippers make as much money as they can on CO2 credits!" http://wlym.com |