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| Thread ID: 74295 | 2006-11-17 17:14:00 | Speed Of Light Exceeded? | SurferJoe46 (51) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 499988 | 2006-11-17 17:14:00 | I know this is a long article, but I have permission to blog or post it via my subscription . Here's the URL for reference ( . msnbc . msn . com/id/3077368/" target="_blank">www . msnbc . msn . com) . This is VERY interesting reading to those who are so inclined toward physics and relativity . Clarifying Einstein’s rules of the road Physicists clear up misconceptions about ‘faster than light’ transmission By Alan Boyle, Science editor July 19, 2000 - Can anything break the cosmic speed limit of 186,000 miles per second? For weeks, scientific circles have been buzzing about an experiment that pulsed light through a special chamber so fast that it left the apparatus before it fully entered it . Now the research has been released at last, and the experimenters say their findings contradict no laws of physics — just the misconceptions people have about them . Einsteins’s theory of special relativity set the tone in 1905 with the claim that an object cannot be accelerated to beyond the speed of light in a vacuum: 186,000 miles per second, or 300,000 kilometers per second . Since then, the light-speed threshold has served as the inspiration for such science-fiction standbys as warp drives and backward time travel — reinforcing the idea that going faster than 186,000 miles a second was pure fantasy . However, in recent years there has been increasing evidence that 186,000 miles a second is not necessarily the limit for light transmission, depending on your definitions . The clearest evidence so far comes from an experiment conducted at the NEC Research Institute in New Jersey and described in Thursday’s issue of the journal Nature . The experiment highlights the loopholes in relativity theory — caveats that usually don’t figure in popular discussions of what Einstein proposed . First of all, it’s important to remember that this business about 186,000 miles per second applies only to light in a vacuum, and that the speed limit applies only to objects that have mass . Since light waves are massless, physicists say that light can travel as fast as … well, as fast as light . It’s well known that light can travel slower than 186,000 miles a second, depending on the medium it’s passing through . That medium can be as common as air, water or glass . Or it can be more exotic . For example, researchers at the Rowland Institute for Science and Harvard University say they’ve been able to slow light down to 1 mph, by passing it through a chamber containing supercooled atoms . Speeding up a light wave Lijun Wang, Alexander Kuzmich and Arthur Dogariu used a different kind of exotic medium in their experiment: The researchers used lasers to “pump” cesium atoms, contained in a 6-centimeter (2 . 4-inch) chamber, to an excited state that doesn’t occur naturally . Then they passed a smooth light pulse, lasting about three-millionths of a second, through the chamber . The atoms in the cesium gas were in just the right state to shift the pattern of peaks and troughs in the many wavelengths that made up the light pulse . Because of this shift, the pulse popped up on the other side of the chamber far sooner than it should have, based on the speed of light in a vacuum . In fact, the time difference — 62-billionths of a second — meant that the peak of the pulse appeared on the far side of the chamber before it entered the near side of the chamber . That’s an instance of what’s known as “negative delay” or “negative velocity,” a phenomenon that seems paradoxical . It was almost as if the light wave could figure out, on the basis of the very beginning of the pulse, how to reconstruct the full peak on the other side . This isn’t the first time researchers have made light waves travel “faster than light,” but it’s the most clear-cut case . Other experiments, including research from Italy that was published in May, involved more manipulation of the light wave in transit . Word of the NEC experiment leaked out weeks ago, but the researchers couldn’t discuss their findings publicly because of Nature’s embargo . Now they are free to declare that the results mesh quite well with what’s known about electromagnetism and quantum mechanics . “Our experiment is not at odds with Einstein’s special relativity,” they said in a statement . “The experiment can be well explained using existing physics theories that are consistent with relativity . In fact, the experiment was designed based on calculations using existing physics theories . ” What it means All this might make it sound as if the NEC researchers found a way to send a message at speeds faster than 186,000 miles a second — which could theoretically open the way for a sort of time travel . But the researchers contend that is not the case . Their experiment dealt with smooth changes in a pulse, and “a smooth function cannot carry information,” Dogariu said . Sending information — for example, the flashes of a laser semaphore — would require sharper variations in frequency that could not be processed in the type of finely tuned atom chamber used by the NEC researchers . This would fit the view that a cosmic speed limit may apply to the transmission of information rather than light per se — a concept that has been the subject of debate with regard to another spooky and widely misunderstood phenomenon known as quantum teleportation . Such fine points were lost in most advance reports about the experiment . In fact, the NEC scientists have been spending much of their time trying to correct erroneous claims about their research . “We are in the middle of a battle to save Einstein’s relativity theory from bad press interpretations of our experiment,” Dogariu said in an e-mail message . Another physicist familiar with the experiment, Aephraim Steinberg of the University of Toronto, agreed that it was easy to misinterpret what the NEC researchers had done . “The researchers have been very careful in the point of view that they’ve taken,” he told MSNBC . com . “Certainly in these experiments, there is something that’s faster than light or even a negative speed, which is very dramatic . But then we have to back up and interpret what’s going on . “It’s very different from what we might want in our science-fiction dreams,” he said . So if the NEC experiment doesn’t violate the laws of physics or show us the path to warp speed, does that mean it’s just a glorified parlor trick? Not at all, the researchers say . On one level, the experiment and others like it are shedding new light — so to speak — on some dark corners of relativity theory . Moreover, the techniques are likely to find practical application, perhaps as a way of speeding up information transfer within circuitry to 186,000 miles per second, known to physicists as “c . ” “Using this effect, one might be able to increase information transfer speed up to ‘c,’” the researchers said . “In present-day technology, information is transmitted at speeds far slower than ‘c’ in most cases, such as through the Internet and inside a computer . ” © 2006 MSNBC Interactive URL: . msnbc . msn . com/id/3077368/" target="_blank">www . msnbc . msn . com |
SurferJoe46 (51) | ||
| 499989 | 2006-11-17 17:23:00 | ...missed the edit time-warp..so here's another interesting thing to Google if one is so inclined: Lense-Thirring effect | SurferJoe46 (51) | ||
| 499990 | 2006-11-17 18:42:00 | "There was a young lady called Bright Whose speed was in excess of light She took off one day in a relative way and returned the previous night":lol: |
jcr1 (893) | ||
| 499991 | 2006-11-17 20:02:00 | Light travels faster than sound . This is why some people appear bright until you hear them speak . Just thought it was worth mentioning as the subject is related :thumbs: |
Shortcircuit (1666) | ||
| 499992 | 2006-11-17 21:29:00 | Light travels faster than sound . This is why some people appear bright until you hear them speak . Just thought it was worth mentioning as the subject is related :thumbs: No it's not!!!!:angry |
SurferJoe46 (51) | ||
| 499993 | 2006-11-17 21:41:00 | Thanks Joe, very interesting and I'll keep an eye open for further articles on the implications of this experiment. The fact that information cannot exceed c is the crux of relativity although I hadn't known that until now. :waughh: | Winston001 (3612) | ||
| 499994 | 2006-11-17 22:01:00 | Ok, light is relatively quick, but dark is much faster as demonstrated daily. Each day starts slightly after midnight (even in the northern hemisphere), and the dark gets here an average 6 hours before the light. QED :groan: | R2x1 (4628) | ||
| 499995 | 2006-11-18 01:34:00 | Ok, light is relatively quick, but dark is much faster as demonstrated daily. Each day starts slightly after midnight (even in the northern hemisphere), and the dark gets here an average 6 hours before the light. QED :groan: lol, also, dark must be faster than light, otherwise, how would it get out of the way? :p |
motorbyclist (188) | ||
| 499996 | 2006-11-18 01:57:00 | . . . We are in the middle of a battle to save Einstein’s relativity theory from bad press interpretations of our experiment,” Dogariu said in an e-mail message . It will be misinterpreted :( Particles can travel faster than the "speed of light" in a medium . That's been known for a very long time . Look up "Cerenkov radiation" . They appear to have "changed the wavelength" of light by a pumping mechanism, so they are simulating a negative refractive index . But they are doing that to a continuous "wave" ; there's no modulation, therefore no information is being transmitted . Einstein rules . :thumbs: |
Graham L (2) | ||
| 499997 | 2006-11-18 02:11:00 | You have to admit it's still pretty damn cool. Didn't even know you could have a -ve refractive index. |
roddy_boy (4115) | ||
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