Hawkin'sDawkins Posted February 8, 2010 Posted February 8, 2010 Hi all, I've been thinking about this for a while and can't get it to add up in my head. I know that according to Mr Einstein, a jolly clever chap by all accounts, nothing can move faster than light. This includes information, as described by light cone diagrams. However, thinking way way back to school, I remember my physics teacher telling me that electricity actually travels instantaneously. The analogy he used was that an electric current in a wire is like a smarties tube full of marbles: If you push another marble in one end, a marble comes out at the other end. i.e. if you push electrons at a power station, the electrons in my kettle move instantly because every electron in the system sort of budges one atom along. So my question is this. If a superconducting electric cable could be made in the order of light-years long,that stretched to to another star system, could signals be sent along it faster than light? Obviously this is a BIG hypothetical as there would be countless engineering problems to overcome, not to mention an existing human presence in another star system, but is the idea plausible?
swansont Posted February 8, 2010 Posted February 8, 2010 However, thinking way way back to school, I remember my physics teacher telling me that electricity actually travels instantaneously. Your physics teacher was wrong. The interactions between the electrons is limited to the speed of light, and it's the speed of light in the material, which means the interaction slowed by the index of refraction. The actual speed of electricity is actually a bit slower, depending on the type of conductor. In a coaxial cable, it's about 2/3 c. The added drift speed of the individual electrons is much, much smaller — of order mm/sec.
Hawkin'sDawkins Posted February 8, 2010 Author Posted February 8, 2010 Well that one got shot down pretty quick. Ah well, thanks anyway. and Mr Boyd lied to me
Sisyphus Posted February 8, 2010 Posted February 8, 2010 Just to be clear, a tube of marbles won't work either, because marbles (or anything) are not perfectly rigid. A compressive wave has to be transmitted down the line, and that wave can't move faster than light.
Sayonara Posted February 8, 2010 Posted February 8, 2010 This reminds me of that "orbital circuit" thought puzzle we did a while ago: http://www.scienceforums.net/forum/showthread.php?t=25762
Bob_for_short Posted February 8, 2010 Posted February 8, 2010 In a fermi-liquid the situation might be different due to quantum (Fermi-Dirac) statistics. There might be instant coupling at long distances. Some fermions in such a system "feel" others not due to electromagnetic interaction propagation but due to filled states forbidding certain transitions. I do not remember any specific example from my quantum liquid classes though.
rogerxd45 Posted February 8, 2010 Posted February 8, 2010 ok so i have a question.... so lets say you have a tube of marbles that is 1 light year long filled to capacity with marbles... you push one more in and that cases the one at the end to fall out. couldnt you thoreticly pass info like this in a binary code type of thing where a 1 in a mrble falling out and a 0 is no marbles fallng out. So since it would take light 1 year to get there it seems at least thoreticly possible to transmit info faster then light since the marble at the end would fall out long before the light actually got there. of course this isnt even close to possible but it does make me wonder.
insane_alien Posted February 8, 2010 Posted February 8, 2010 ok so i have a question.... so lets say you have a tube of marbles that is 1 light year long filled to capacity with marbles... you push one more in and that cases the one at the end to fall out. couldnt you thoreticly pass info like this in a binary code type of thing where a 1 in a mrble falling out and a 0 is no marbles fallng out. So since it would take light 1 year to get there it seems at least thoreticly possible to transmit info faster then light since the marble at the end would fall out long before the light actually got there. of course this isnt even close to possible but it does make me wonder. sisyphus already answered this one.
emcelhannon Posted March 23, 2010 Posted March 23, 2010 Yes, but it doesn't matter if the marbles are perfectly rigid, because space/time is not. I'm fairly certain Einstein presented a hypothetical example involving a pully on the moon. Imagine a pully on the moon with a ideal static line, (impossible, but imagine completely unelastic) threaded through it. If you had one end in each hand, and pulled with the left, the right wouldn't respond for 2.7sec, (800,000 mile round trip at light speed). It's not that the marbles are only slightly more rigid sponges that absorb the shock, it's that the speed of light IS the speed of time.
Farsight Posted March 29, 2010 Posted March 29, 2010 ...lets say you have a tube of marbles that is 1 light year long filled to capacity with marbles... you push one more in and that cases the one at the end to fall out. couldnt you thoreticly pass info like this in a binary code type of thing where a 1 in a mrble falling out and a 0 is no marbles fallng out. So since it would take light 1 year to get there it seems at least thoreticly possible to transmit info faster then light since the marble at the end would fall out long before the light actually got there. Replace your tube of marbles with a steel rod 13000 miles long, and whack one end of it with a hammer. The speed of sound in steel is about 13000 mph, so it's an hour before the other end moves.
emcelhannon Posted April 2, 2010 Posted April 2, 2010 ???? Time is the 4th dimension. Think of 187K miles per hr is the angle in which it extends. Is that a decent analogy? I think I like it.
insane_alien Posted April 2, 2010 Posted April 2, 2010 time is a dimension, it doesn't have a speed if it does, then other dimensions must also have a speed. what do you think the speed of forward is? or the speed of left? or the speed of down?
emcelhannon Posted April 2, 2010 Posted April 2, 2010 I believe that is a quote from Einstein. The speed of light is the speed of time.
insane_alien Posted April 2, 2010 Posted April 2, 2010 just because einstein said it doesn't make it right.
emcelhannon Posted April 2, 2010 Posted April 2, 2010 Dimensions in this case are mathamatical abstractions. You need four numbers or pieces of information to attend a meeting or exist at all. Say you have a meeting on the third floor on the corner of 5th street and 47th avenue. An element of special relativity is that you also need a 4th number, which is time. He says that space and time are connected in the way that the 1st,2nd and 3rd are to each other and coined the word "spacetime." The relationship between time and the others is a special number, which is "c."
SpaceShark Posted April 4, 2010 Posted April 4, 2010 If something is traveling faster than the speed of light - how would you detect it? Can sound waves detect light waves? If you subscribe to the power of infinity - Then it will have to lie in the realm of the space dimension - all of space is but a point of absolute nothingness - which everything single particle of matter is contained - thus you will have your instantaneous travel
Mr Skeptic Posted April 5, 2010 Posted April 5, 2010 I believe that is a quote from Einstein. The speed of light is the speed of time. Sort of. It's more a unit conversion. Kind of like if we measured "up" in inches but "forward" and "sideways" in meters, then you'd have a unit conversion between "up" measurements and "sideways" measurements. I suppose you could call that the "length of up".
Sisyphus Posted April 5, 2010 Posted April 5, 2010 "Speed" is distance per time, by definition. Hence "speed of time" taken literally is meaningless. As a figurative expression, it's more defensible. It's not really as simple as a unit conversion, either. Distance and duration are inextricably linked, but they're not synonyms.
emcelhannon Posted April 8, 2010 Posted April 8, 2010 "Speed" is distance per time, by definition. Hence "speed of time" taken literally is meaningless. As a figurative expression, it's more defensible. It's not really as simple as a unit conversion, either. Distance and duration are inextricably linked, but they're not synonyms. When viewing something in motion, we observe its speed through space in relation to our own position, (distance x time). We will observe the speeds within that something as slower than our own. This difference adds a new quantity to be measured, (the difference in the rate of change between things in relative motion). So we end up with speeds of speed, and the faster one is, the slower goes the other. The speed of light is not a unit. It is an absolute quantity that is divided into units. Each unit, however, can be regarded as a fraction of space or time. When it is regarded as a fraction of time, what better word should be used to define it than "speed?"
Dak Posted April 10, 2010 Posted April 10, 2010 time is a dimension, it doesn't have a speed if it does, then other dimensions must also have a speed. what do you think the speed of forward is? or the speed of left? or the speed of down? can't you have statements like 'time is going at x seconds in area 1 per second in area 2'? and doesn't gravity 'slow time down'? so... umm... if you could construct a magical anti-gravity tube that completely blocked out the effects of gravity so that gravity within the tube was absolute zero, and you fired off one beam of light down the tube and one parrallel to (and outside) the tube at the same time, then the beam of light within the tube should reach the end before the beam of light outside, effectively sort of making the tube a 'bit faster than the speed of light would have been otherwize' communication link? because time inside the tube goes at a rate of '1 second per slightly less than one second outside the tube'?
1bobwhite Posted May 13, 2010 Posted May 13, 2010 Consider this real world dilemma: Can you explain the light speed change that occurs when a laser beam exits a fiberoptic into a vacuum. Light speed has been shown to be slower when traversing through a material such as a fiber optic fiber, but at the exact boundary surface of the fiber optic as the light exits, the speed instantly is at the light speed in the vacuum. Is this instantaneous infinite acceleration of photons? Seems to be. See my crude illustration. Bob.
swansont Posted May 13, 2010 Posted May 13, 2010 Photons always travel at c. The speed of propagation will also be c when there is nothing around to absorb them and delay their trip, as is the case as they exit the fiber.
Moontanman Posted May 13, 2010 Posted May 13, 2010 Isn't it true that the speed of light inside the fiber optics is still c when it's not interacting with the atoms of the optic fiber? if so there would be no acceleration out side the cable, just a lack of interactions the photons have to deal with.
michel123456 Posted May 14, 2010 Posted May 14, 2010 The speed of light is not a unit. It is an absolute quantity that is divided into units. Each unit, however, can be regarded as a fraction of space or time. When it is regarded as a fraction of time, what better word should be used to define it than "speed?" Hi Ernie Speed is distance divided by time. (note that it is NOT Space divided by time, but distance divided by time). It is not "a fraction of time", it is a fraction of space. If you are searching for dividing time by anything, you can only but divide time by distance. Then you get sec/meters, or 1/v. That could be the "speed of time": exactly the opposite of what we call "speed". In this case, it would be better to put another name on it, because "speed" means something, and "inverse speed" means something else.
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