colonel@gloria.UUCP (George Sicherman) (11/15/84)
[You' in a heap o' trouble, bwah] Here's another version, for people who do not want to fool around with relativity: You are made up of charged particles, whose courses are determined by their charges and masses. When you move, the particles generate magnetic forces - this is the Oersted effect. The fields slow down the particles, and interfere with the effect of any outside force. At the speed of light, the magnetic forces exactly counteract the electric forces, time stops, and outside forces have no effect. Not that any of this is what Oersted has in mind ... -- Col. G. L. Sicherman ...seismo!rochester!rocksanne!rocksvax!sunybcs!gloria!colonel
norm@ariel.UUCP (N.ANDREWS) (11/18/84)
> Here's another version, for people who do not want to fool around > with relativity: > You are made up of charged particles, whose courses are determined > by their charges and masses. When you move, the particles generate > magnetic forces - this is the Oersted effect. The fields slow down > the particles, and interfere with the effect of any outside force. > At the speed of light, the magnetic forces exactly counteract the > electric forces, time stops, and outside forces have no effect. > Not that any of this is what Oersted has in mind ...-- Col. G. L. Sicherman 1.) Time stops? What is time and under what conditions does time stop? What does it mean to say that time stops? 2.) "whose courses are determined by their charges and masses." Did you forget free will? You mean someone trying to understand the illegality of FTL travel should trade an explanation based on relativity for one that requires answers about time and free will? I sure would like to learn from someone who understands all about relativity, time and free will. I'm not really being all that facetious... Norm Andrews, vax135!ariel!norm
gjk@talcott.UUCP (Greg J Kuperberg) (11/20/84)
>> Here's another version, for people who do not want to fool around >> with relativity: >> You are made up of charged particles, whose courses are determined >> by their charges and masses. When you move, the particles generate >> magnetic forces - this is the Oersted effect. The fields slow down >> the particles, and interfere with the effect of any outside force. >> At the speed of light, the magnetic forces exactly counteract the >> electric forces, time stops, and outside forces have no effect. >> Not that any of this is what Oersted has in mind ...-- Col. G. L. Sicherman >1.) Time stops? What is time and under what conditions does time stop? >What does it mean to say that time stops? >2.) "whose courses are determined by their charges and masses." Did you forget >free will? >You mean someone trying to understand the illegality of FTL travel should trade >an explanation based on relativity for one that requires answers about time and >free will? >I sure would like to learn from someone who understands all about relativity, >time and free will. I'm not really being all that facetious... >Norm Andrews, vax135!ariel!norm First, the answers to your questions: Time means evidence of change in the system. If a physical system is doing absolutely *nothing*, that is, the air in it isn't moving, no light is being radiated through it, radioactive decay is not taking place, etc., we say that time has stopped. Basically, the Colonel is arguing that electromagnetic weaken in a system moving at high velocity, and therefore all events in the system slow down. This includes clocks, heart rates, and everything else (actually, the electromagnetic force does not include radioactive decay, but a phenomenon similar to Oersted's effect takes place in the other forces of nature as well). However, the occupant of a space ship moving at high velocity would not notice, since his metabolism would be slowed down just as much as everything else. At the limit of the speed of light, everything stops. A person in a spaceship travelling at the speed of light appears frozen in mid air, the ship clocks having stopped, the ship computer having stopped, and the air itself not moving at all either. Yes, the electromagnetic force is responsible (usually in quantum mechanical form) for almost *every* effect we see, from the why "water is wet" to why we have gases, liquids, and solids, to semiconductor technology. Whether or not free will is a consequence of the electromagnetic force is a question of theology, but the Colonel was going under the assumption that it is. Mind you that special relativity is a simple, but tricky, derivation from Maxwell's equations. The Colonel's argument works for plain-Joe travel, but one could still ask, "couldn't there be something like hyper-space leaps, where you don't really move faster than light, but you can arrive at your destination quickly nevertheless?" Here is a stronger argument against FTL travel: One of the first consequences of special relativity is that simultaneity is not conserved. If you have two events that happens at the same time at different places, then a moving observer would not only *see* them happening at different times, but even taking into account the finite speed of light, he would *deduce* that they must have happened at different times. In fact, under certain circumstances, the order of occurence of two events can be switched. Suppose you have two people, at positions A and B. Suppose that at time t0, the person at A turns on a flashlight pointed at B. Suppose that at time t1, the person at B sneezes, and at time t2>t1, the light arrives at B. Then for some moving observer, B sneezed *before* A turned on the flashlight. Now supposing I take off for Alpha Centauri and arrive there in less than the amount of time that it takes light to get from here to Alpha Centauri. Then for some moving observer, I arrived before I left! Thus I have the power to travel backwards in time. This causes a whole slew of problems. If I can travel backwards in time, I could, for example, go back and kill my grandfather before my father was conceived. I would have to then cease to exist (as would my father). But if I never existed, who killed my grandfather? It's because of nonsense stories like this that people say that FTL travel is impossible.
kay@flame.UUCP (Kay Dekker) (11/23/84)
<BUGBAITER> How about Bell's Theorem? Now, my maths isn't hyper-hot, and my knowledge of reality theory isn't super-current, but it seems that Bell's theorem, because it disposes of the principle of local causes, implies that FTL transmission of information can occur. I believe this all came out of the good old Einstein-Rosen-Podolsky experiment .... Kay. -- "Serendipity: finding something useful on the net" ... mcvax!ukc!qtlon!flame!ubu!kay
js2j@mhuxt.UUCP (sonntag) (11/26/84)
On why FTL implies time travel: > Now supposing I take off for Alpha Centauri and arrive there in less than > the amount of time that it takes light to get from here to Alpha Centauri. > Then for some moving observer, I arrived before I left! Thus I have the > power to travel backwards in time. > > This causes a whole slew of problems. If I can travel backwards in time, I > could, for example, go back and kill my grandfather before my father was > conceived. I would have to then cease to exist (as would my father). > But if I never existed, who killed my grandfather? I still don't understand! Some moving observer, who obviously doesn't understand relativity thinks that you arrived there before you left, and you believe him? Assuming for the sake of arguement that you had some method of traveling (let's simplify things) any distance in zero time. Please explain how this could be used to go back in time. I don't want to hear about any observer who thinks that you did. Many thanks for all who helped to explain why c is a speed limit, but I still don't understand why violation of this speed limit implied time travel. Jeff Sonntag ihnp4!mhuxt!js2j p.s. What do you mean? You're my grandson from the future come here to test a theory? Wait a minute.... what if I just promise not to have children? Oh, you have to be sure. Wait! Put down that gun! I'm too young to ^#~................. USERID JS2J TIMED OUT AT 09:48:37 MESSAGE TERMINATED -- MAILER
stern@bnl.UUCP (Eric Stern) (12/10/84)
> > On why FTL implies time travel: > > Now supposing I take off for Alpha Centauri and arrive there in less than > > the amount of time that it takes light to get from here to Alpha Centauri. > > Then for some moving observer, I arrived before I left! Thus I have the > > power to travel backwards in time. > > I still don't understand! Some moving observer, who obviously doesn't > understand relativity thinks that you arrived there before you left, and > you believe him? One of the postulates of physics is that any observer in an inertial frame must observe a universe that obeys the same laws of physics as an observer in any other inertial frame. Otherwise there is no point to physics since the universe depends on how you observe it, and not on any intrisic existence of its own. If one observer in an inertial frame sees me getting to Alpha Centauri before I leave Earth, that is the same thing as observing effects before their causes (causality violation) which means that his physics is different from my physics. As I have pointed out above, this is a big no-no. Now, if the theory leads to contradictions, it must be modified. In this case the only allowed modification is to disallow travel faster than light, since the theory makes sense for any speed slower than lightspeed. This is the only allowable theory, because all other pieces follow directly from the observation that the speed of light is constant in all reference frames. Of course it must be noted that there is no experimental evidence for faster than light travel, so the theory holds up. To answer another question about quantized spacetime, the experimental evidence suggests that there is no quantization of these quantities. Since quantum electrodynamics has been experimentally verified to be correct at extremly large energies (10 Gev) and q.e.d. is a continuous theory this must put a limit of space quantization of the order of an electron wavelength at 10Gev or about 1.0e-17 m. Eric G. Stern Dept. of Physics, SUNY StonyBrook NY 11727 stern@bnl.arpa philabs!sbcs!bnl!stern
roy@gitpyr.UUCP (Roy J. Mongiovi) (12/15/84)
> One of the postulates of physics is that any observer in an > inertial frame must observe a universe that obeys the same laws of > physics as an observer in any other inertial frame. Otherwise > there is no point to physics since the universe depends on how > you observe it, and not on any intrisic existence of its own. But I thought that QM says that events absolutely DO depend on being observed? -- Roy J. Mongiovi. Office of Computing Services. User Services. Georgia Institute of Technology. Atlanta GA 30332. (404) 894-6163 ...!{akgua, allegra, amd, hplabs, ihnp4, masscomp, ut-ngp}!gatech!gitpyr!roy Who me? I'm not even a REAL modo, I'm only a quasi-modo.
gwyn@brl-tgr.ARPA (12/19/84)
> > One of the postulates of physics is that any observer in an > > inertial frame must observe a universe that obeys the same laws of > > physics as an observer in any other inertial frame. Otherwise > > there is no point to physics since the universe depends on how > > you observe it, and not on any intrisic existence of its own. > > But I thought that QM says that events absolutely DO depend on being observed? A very common mistake. What quantum physics tells us is that observation affects the system being observed (specifically, the measured value of a physical quantity is an eigenvalue of the corresponding operator, with probability distribution of eigenvalues corresponding to squared amplitudes of elements of the operator applied to the system state, according to the usual QM computation rules). This is not the same as "depending on being observed". The physical occurrences propagate in the total absence of any observer. This is really not much worse than in relativity theory, where the actual results of observations are observer (state of motion) dependent projections of absolute physical objects. Relativistic descriptions can be done either using coordinates or coordinate-free; similarly for quantum physics.