Speed of Light Exceeded? 393
PreacherTom writes "Scientists at the NEC Research Institute in Princeton, NJ are reporting that they have broken the speed of light. For the experiment, the researchers manipulated a vapor of laser-irradiated atoms, causing a pulse that propagates about 300 times faster than light would travel in a vacuum. The pulse seemed to exit the chamber even before entering it." This research was published in Nature, so presumably it was peer-reviewed. It's impossible from the CBC story to determine what is being claimed. First of all they get the physics wrong by asserting that Einstein's special relativity only decrees that matter cannot exceed the speed of light. Wrong. Matter cannot touch the speed of light in vacuum; energy (e.g. light) cannot exceed it; and information cannot be transferred faster than this limit. What exactly the researchers achieved, and what they claim, can only be determined at this point by subscribers to Nature.
It works... (Score:5, Funny)
Re:It works... (Score:5, Funny)
Re:It works... (Score:5, Funny)
No, this is the dupe. The original will be posted tomorrow.
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Re:It works... (Score:5, Informative)
http://science.slashdot.org/article.pl?sid=05/08/
Now pardon me as I karma whore:
By Trip11
By: Justanyone
By: Alwin
here is my example (Score:5, Interesting)
You put a lightbulb inside a spinning coffee can with slits at 4 equally spaced spots around the circumference.
The photons are projecting out of the slits. As the can spins, the pattern of light and shadow turns and projects on the surroundings.
The outside surface of the can is moving at 1 full turn per second.
10 feet away from the can, the pattern of light and shadow is moving at 31.4 feet per second.
100 feet away from the can, the pattern of light and shadow is moving at 314 feet per second.
At just 2 miles from the can (we are using a BRIGHT bulb), the light and shadow is moving 22,619 miles per hour!
Re:here is my example (Score:5, Informative)
There's no tangential movement of photons here breaking any 'laws'. Let me give another similar example just to point out how stupid it is:
Say you have a light bulb with two slots on each side you can open an close. Both sides are being observed from a distance of 1km, side A is open and side B is closed. Slit B is opened then 5 seconds later A is closed. Am I now going to claim observer B saw the light from A move to B so fast it came FROM THE FUTURE?
Bonus points if you can calculate how fast it went.
Re:here is my example (Score:4, Insightful)
Re:here is my example (Score:5, Informative)
The same goes for group velocity.
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Re:here is my example (Score:5, Funny)
Sufficient amounts of ingested caffeine can make everything seem faster! I like experiements which require one to consume an entire can of coffee in order to cut slots it in to do psudo-physics research.
Re:here is my example (Score:5, Funny)
"I put instant coffee in a microwave oven and almost went back in time."
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Re:here is my example (Score:5, Funny)
Re:here is my example (Score:4, Funny)
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What makes you think a can of coffee isnt hot?
The Japanese have been doing this shit forever.
Re:here is my example (Score:4, Funny)
Re:here is my example (Score:5, Funny)
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Indeed, that was the point you missed.
Re:It works... (Score:4, Interesting)
Drive a bus at
I can see how this would be useful for faster-than-light communication, but since nothing (well, no "matter")actually exceeds the speed of light, none of the fundamental laws are broken.
I could be totally and absolutely wrong about all of this.
BBH
Re:It works... (Score:5, Informative)
You are
The only way you set up these faster than light experiments is by manipulating the entire situation to set things up so it looks like the wave is being propagated faster than light. No information is being transmitted, because the "wave" isn't really a a propagation of information, but a result of you very specifically setting up initial conditions for all the photons, or in your example, people. If you tell everyone to stand and sit as soon as they see the person behind them stand and sit, you won't violate causality because there will be a delay inherent in them recieving the information about the previous seat's state. If instead, you tell them all to look at their watches and move at a pre-determined time, you can create something that LOOKS like a wave propagating faster than light, but in reality no information is being transmitted, because you cleverly manipulated the initial conditions.
Faster-than-light communication is still, unfortunately, completely impossible, and it will take one big-ass change in our understanding of physics to have any hope of ever acheiving it.
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I could be totally and absolutely wrong about all of this.
I don't know, and I really don't care - I just liked the mental image of this bus speeding along at 0.99c, all full of people doing Mexican waves really quickly, and everyone's happy, and everyone's laughing about getting in the Guinness Book of Records, and the cute foreign couple down the back are taking pictures ...
...
And then all of a sudden some wildlife jumps out onto the road and the driver slams on the brakes
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From your perspective, however, this isn't true. With enough energy (a hopelessly
Not all forces travel at 'c'... (Score:5, Informative)
Not at all correct. First the weak force is transmitted by W and Z bosons which have mass and therefore CANNOT propagate at the speed of light. Secondly in their own reference frame, by definition the weak force bosons will not propagate at all since your own reference frame is defined as the frame you are at rest in. Thirdly massless particles have no reference frame of their own.
I know you were quoting someone else but please pick someone who at least has a clue what they are talking about!
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The best way to define momentum is through the concept of "generalized momentum". Every physical system is ultimately described by a quantity called a Lagrangian or Lagrangian density that's given to you axiomatically with respect to certain generalized coordinates. The generalized momentum is defined as the rate of change of the lagrangian with respect to the gen
Phase velocity versus group velocity... (Score:3, Informative)
If you define the group velocity as the speed of the peak of a gaussian pulse modulated by some frequency, this can travel faster than c. However, there are "tails" that extend far from the hump, and these contain the information about the hump.
A discontinuity (I wake up and decide to press a button) cannot be propagated faster than c.
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Re:It works... (Score:4, Funny)
Re:It works... (Score:5, Funny)
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Results of experiment published in the past (Score:5, Insightful)
Re:Results of experiment published in the past (Score:5, Funny)
This story is from November 2000.
So the dupe will be posted 6 years ago? Awesome! I'm looking forward to it.
Re:Results of experiment published in the past (Score:5, Funny)
Shouldn't you be looking backward to it?
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Re:Results of experiment published in the past (Score:5, Informative)
Found it! [slashdot.org]
"According to this NY Times piece, Lijun Wang of the NEC Research Institute in Princeton has reported an experiment where "a pulse of light that enters a transparent chamber filled with specially prepared cesium gas is pushed to speeds of 300 times the normal speed of light". A second experiment by three scientists for the Italian National Research Council is reporting also superluminal speeds. And yet, this seems to be consistent with Einstein's theories. "
Wow
So which one is the dupe? (Score:2)
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Well, subscribers who keep their back-issues anyway.
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Sounds Familiar - (Score:2)
Anyone got a name for that? I'm lost on it.
Group Velocity Again (Score:5, Informative)
You're stuck in traffic, behind an accident. They clear the accident. Slowly, every car speeds up now that the blockage is gone. If you're looking from above, you'll see a "wave" move through the line of cars, as each takes a few seconds to realize he can accelerate.
This wave is the group velocity, and very much has nothing to do with the speed of each individual car.
Suppose all the cars were wired electronically to know that they could all accelerate at once. That knowledge would move at nearly the speed of light.
No car would be moving at the speed of light. Everyone would just hit their gas pedal at almost the same time.
Almost every time we see these stories, this is the type of speed they're talking about.
Re:Group Velocity Again (Score:4, Informative)
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no information? (Score:2)
Re:no information? (Score:4, Informative)
Because of the way the experiment is set up, the pulse has to arrive; you can predict that it will arrive because of previous things that have happened. Basically, as I understand the experiment, a sequence of short pulses of light are sent down the chamber, with known gaps between them. The 'faster than light' wave results from the phase motion of these normal speed light waves. By the time it starts propogating, you can already tell that it will do so from observations you can make at the end of its run.
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It's exactly the same experiment we've seen time & time again, and it's meaningless because no information is transmitted.
Well, I guess that explains why we keep seeing dupes about it.
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Re:Group Velocity Again (Score:4, Informative)
There are plenty of examples of arbitrary "things" that move faster than the speed of light. For example, take a laser pointer and point it at the moon. As you move your hand, you can get that dot moving across the surface of the moon way faster than the speed of light. However, this can't be used to transmit information faster than c; it still takes a few seconds for the light to get from your moving hand to the surface of the moon.
The group velocity of photons is just another one of those things. The summary refers to a "pulse" that "propagates"; they almost certainly mean the group velocity, which is useless to transmit information.
Re:Group Velocity Again (Score:5, Funny)
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It seems to me that the "dot" wouldn't move faster than light in any ref frame. When you rotate the laser pointer by an infinitesimal angle (neglecting noninertial effects) then the "dot" on the moon doesn't move by the corresponding distance until the information "I have moved the pointer by d(theta) now move accordingly Mr. dot" reaches the dot on the moon, after which it moves by the corresponding distance. However, by that time, I have rotated my pointer to another position. Effecti
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Also I believe a group of scientists sucessfully proved that you can go faster than light using super cooled Cesium or something like that.
I don't understand why people are so hung up on this absolute speed of light thing, Einstein was a smart guy but so were Galileo, Newton and more recently Hawkings, and Hawkings says something > SOL.
String theory is all based around the concept that nothing can go faster than l
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Actually, your analogy is bad because in the case of cars in a traffic jam, if wave of cars did indeed move faster than light (even if the individual ones didn't), that would still violate special relativity because there would be information (there's no more blockage) transmitted faster than the speed of light.
The correct analogy is not that the wave moves faster than the speed of light, it's that the wave moves faster than the top speed of a car. In this case the analogy is slightly flawed because you could use it to transmit information faster than the top speed of a car; the only reason this is possible is because the drivers are using light to see when to accelerate :D
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The correct analogy is not that the wave moves faster than the speed of light, it's that the wave moves faster than the top speed of a car. In this case the analogy is slightly flawed because you could use it to transmit information faster than the top speed of a car; the only reason this is possible is because the drivers are using light to see when to accelerate :D
The speed of the wave has pretty much nothing to do with the speed of the car. It doesn't even go into the same direction (the cars go forward, the wave travels backward). And actually, many wave phenomena (except light in vacuum) involve the same basic phenomenon: they involve movement of some medium (water molecules for surface waves, O2 and N2 molecules for sound, pieces of rope, electrons in a wire, ...) which may move slower or faster than the wave.
Relativity says that neither the particles of the m
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Information? (Score:5, Informative)
Re:Information? (Score:5, Insightful)
That, and earth is a sphere in the center of the universe, as Plato proved.
Fair enough... (Score:2)
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Besides, kdawson's wrong. The article does not say that SR says that matter can't travel faster than light, it says that "The result appears to be at odds with one of the basic principles of Albert Einstein's theory of relativity, that nothing can go faster than the speed of light in a vacuum". Further down the article it then says "The scientific statement "nothing with mass can travel faster than
Time . . . (Score:5, Funny)
"Lemons?"
"If I have three lemons and three oranges and I lose two oranges and a lemon, what do I have left?"
"Huh?"
"Okay, so you think that time flows that way, do you?"
-Mostly Harmless
Slashdot is not the proper forum for speculation. (Score:3, Informative)
The linked article says, and I quote: "Last Updated: Friday, November 10, 2000 | 11:57 PM ET" (My emphasis.)
Please consider that Slashdot is not the proper forum for speculation about Physics, especially when it is not clear what happened, and the article is over 6 YEARS old.
Please consider that perhaps you should not be a Slashdot editor. It amazes me that Slashdot editors are still, after all these years, not very good at what they do. What social processes prevented even the most simple learning?
--
Is U.S. government violence a good in the world, or does violence just cause more violence?
Re:Slashdot is not the proper forum for speculatio (Score:3, Funny)
So: kdawson's integrity remains intact.
Re:Slashdot is not the proper forum for speculatio (Score:2)
Then what is it? (Score:2)
Obligitory Futurama (Score:5, Funny)
Cubert: That's impossible. You can't go faster than the speed of light.
Farnsworth: Of course not. That's why scientists increased the speed of light in 2208.
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Ok, lemme take a poke at what is might be (Score:2, Interesting)
Old news (Score:2, Informative)
If you shined a flashlight or a laser beam at a wall very far away and quickly turned the angle of the beam, the lit spot on the wall might move faster than the speed of light. It doesn't mean you can transmit information faster than the speed of light in a vacuum.
Old, Old News (Score:2)
Last Updated: Friday, November 10, 2000 | 11:57 PM ET
Funny (Score:5, Funny)
How do I mod down kdawson and the /. editors? (Score:5, Insightful)
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Ever wonder how a person can be moded troll, explain himself a few posts later and be moded insightfull or interesting? It is freaks going after freaks.
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One way (Score:2)
A few misconceptions (Score:4, Insightful)
It will be interesting to see in what sense they have exceeded the speed of light; so far all examples of this have proven to be tricks of the circumstances rather than actual physics - eg. it is easy, at least in theory, to make a shadow move faster than the speed of light, but it doesn't represent actual, physical motion; I'm sure most have heard about this one.
Question (Score:2, Interesting)
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Wrong, sorry (Score:2)
Just because there are some falling blocks, doesn't mean the ball will jump on the head of the next block just because it's there. You'd still need to accelerate the ball from zero velocity (in your frame of reference) to reaching the head of the next block just in time. It would take infinite energy to even reach the speed of light, and may the elder gods help you in gettin
Not in Nature... (Score:4, Interesting)
For another, more understandable report, here is a BBC website: http://www.whyevolution.com/einstein.html [whyevolution.com] (search for Wang).
Just Horrible (Score:3, Insightful)
http://gregegan.customer.netspace.net.au/APPLETS/
This is probably the worst article I've ever read. The journalist's dubious explanation of the findings and complete lack of understanding of how these findings fit into known science is a perfect example of how modern journalism is often at odds with the spread of knowledge.
The findings are IN NO WAY "at odds" with relativity.
The team did not "change the state of a vapour in a way that light travelling(sic) through it would travel faster than normal." They created a pattern of interfering waves that made a pulse that traveled faster than normal. This is like saying that swinging the end of a jump-rope changes the state of the surrounding air to make the rope move faster, when in reality the ends of the rope are stationary and only a pulse is moving down the rope.
This was on Fark yesterday and it was even lower than THEIR scientific standards. I'm waiting for it to hit Digg so 500 people can comment that there is a massive conspiracy to suppress FTL technologies.
MOD PARENT UP (Score:2)
This research was done in 2000 (Score:5, Informative)
Here's what he said:
The page also contains an "intuitive" explanation of the phenonmenon. A careful reading and some high school level physics make it simple to understand in a logical sense, but it remains completely incomprehensible intuitively (at least to me).
Tree in the forrest (Score:2)
Only if it leaves behind somthing similar to a log.
"cannot - impossible " etc etc (Score:2)
The fastest thing in the universe is... (Score:2)
- Hey guys... ever wondered what's the fastest thing in the universe?
- Dunno... it's a thought, maybe?
- No, man, it's light.
- You're all wrong. It's diarrhea.
- What the hell? Diarrhea?
- Yeah. I once had a diarrhea so bad that I ran to the toilet and didn't have enough time to think about turning on the lights.
Dupe -- The Space Shuttle Beat Them (Score:5, Funny)
CNN doesn't lie!
http://fire-eyes.org/gal/v/hmr/cln/shuttleisfast.
thiotimoline (Score:3, Interesting)
Back in time vs forward in time (Score:2)
If x travels forward in time isn't that equivalent to (universe - x) travelling back in time?
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Re:You can beat it! (Score:5, Insightful)
Well, to be honest the today conception of vacuum is not that of a space completely devoid of everything. Vacuum has an energy, and literally boils of instantly-annihilating particle-antiparticle couples. This has observable effects that have been measured, like the Casimir effect. See http://en.wikipedia.org/wiki/Vacuum_energy [wikipedia.org] for an explanation.
Uhm, yeah. I believe you, but... (Score:2)
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Has your enormous, rigid rod gone floppy? (Score:2)
Let 2 enormously rigid "rods" of astronomical length be parallel. Let the one set of endpoints be fixed, and accelerate the other ends towards each other until crossing, and let them continue moving, now apart, with the rods intersecting. Even if the individual endpoints are moving at sub-c, one could easily imagine having the intersection point moving faster than c, however the intersection point is a logical construct, carrying neither
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