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Speed of Light Exceeded?
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.
I wrote this yesterday.
This story is from November 2000. If Princeton scientists *did* exceed the light-speed barrier, then it the evidence would only naturally show up in the past. Interesting!
99% chance it's this again:
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.
So, was any information transmitted? Then it's big news I suppose, otherwise not? From the sound of it, a "pulse" make me suspicious, but I lack the full physics geekdom to completely dismiss the story. Anyway, speed of light only applies to transmission of information, not group velocity.
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kdawson: You said, and I quote: "What exactly the researchers achieved, and what they claim, can only be determined at this point by subscribers to Nature."
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?
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Farnsworth: These are the dark matter engines I invented. They allow my starship to travel between galaxies in mere hours.
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.
Summation 2
I've been hearing group velocity. I understand nothing, but I remember from a class, no idea which one now, that you can seem to exceed the speed of light, but you're not really doing it. For example take a tube of balls, packed end to end. There is no more room for any of the balls, so the moment you put one in on one end, the other one immediatly pops out. Now, if that tube of balls was empty, then it would take n amount of time for that ball to roll the length of the tube. Is this the same conceptionally or is it different?
This is old news.
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.
On my google startpage I have the 'quotes of the day'. Just now I noticed there was a quote from Woody Allen : "It is impossible to travel faster than the speed of light, and certainly not desirable, as one's hat keeps blowing off."
I have mod points, but I can't figure out how to dole out some negative karma to either the person sending in a link for an over six year old story, or the editor who approved it. >:(
"Convictions are more dangerous enemies of truth than lies."
I just don't understand the following: the pulse/no pulse thing is itself a bit of information.
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.
You moron! Can't you see that the information contained in the article appeared back in November 2000 yet the test was conducted on March 2007? This is further PROOF that they have exceeded the speed of light as the information contained in the article appeared six years prior to the tests being reported at Slashdot.
:)
So: kdawson's integrity remains intact.
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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 for an explanation.
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First of all - it is a fundamental assumption in Einstein's theory that the speed of light is the same in EVERY frame of reference; ie. two observers moving at some speed relative to each other will see the same lightwave moving at the same speed. One consequence of this is that all (rest-) massless particles move at the speed of light - in a way they only exist as movement or a disturbance of some field or other. Photons are disturbances in the electro-magnetic field, gravitons are disturbances in the gravity field (or the 'structure of space', if you like). Another consequence of the constance of the speed of light is that particles with real restmass > 0 get heavier when they move faster and the perceived mass goes to infinity as the relative speed approaches the speed of light.
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.
(Oh. No friction, by the way. Let's assume everything's soaked in WD40 or whatever.)
The heavens do not fall for such a trifle.
For another, more understandable report, here is a BBC website: http://www.whyevolution.com/einstein.html (search for Wang).
For those who want to see how this REALLY works...2 0/20.html
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.
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!
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).
All 4 basic forces: electromagnatism, gravity, strong nuclear, and weak nuclear (not Nukular; bite me, George) forces propogate at the speed of light in their reference frame.
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!
Maybe it's due to the time bending effects of this, but the space shuttle already beat them.
j pg.html
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OK, I see something like eight articles that have been put up by kdawson, whoever he (or she) is. This one is pretty typical: While spouting off about how the article got the physics wrong (arguable at best), the "editor" failed to notice that the article in question is over six years old!!!
Pathetic, really. It's like a return to the days of Jon Katz.
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Was I the only one who skimmed the story header and thought of Thiotimoline?
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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.
It's not wasting time, I'm educating myself.