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.

It works...

[fortunato]

I wrote this yesterday.

Re:It works...

[Anonymous Coward]

expect a dupe tomorrow

Re:It works...

[frdmfghtr]

expect a dupe tomorrow

No, this is the dupe. The original will be posted tomorrow.

Re:

[jigyasubalak]

That's nothing. I will write this tomorrow.

Re:It works...

[AchiIIe]

It must be true, I read this article months ago....

http://science.slashdot.org/article.pl?sid=05/08/2 0/1440228 [slashdot.org] ..

Now pardon me as I karma whore:

By Trip11

Everyone say it together with me: "Phase velocity vs Group velocity" There are no photons in this experiment that are traveling faster than the speed of light. Only collections of them that 'appear' to be doing so. Think of this as an example: I space people out in a line, each of them two light minutes apart from the people next in line (all at rest with respect to each other). Now I go about talking to them and informing them of my plan. At 12:00 the first person waves, at 12:01 the second person waves, at 12:02 the third person waves, and so forth. My "wave" is propogating, therefore, at twice the speed of light. This is the same thing that this experiment is doing more or less. By spending extra time setting up the experiment, you can make it appear that a light pulse travels faster than c, but like my "wave" it is only an appearance.

By: Justanyone

Information flow (see: Steven Hawking's theories) cannot propogate at faster than the speed of light, or causality is violated and we have (dead virgins/future grandfathers) all over the place.

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. If we switch frames we're not fooling anyone; if we preposition information we're not watching causality violations.

This kind of story is quite irritating, not due to the actual achievement involved (playing with light propogation is actually very cool geek-cred stuff), but the overhype and miscommunication to all the laypersons out there who just go, "Yup, that's an 'oops', they said it was a law and now it ain't. I guess evolution might not really be true, dad-gummit, I don't trust me none o' dem smarty pants anyway."

By: Alwin

Set up say, 1000 domino blocks in a row. Then tip the first one over. Given constant size, weight, spacing of individual blocks, and a horizontal surface, you will observe blocks falling down at a constant rate/speed ('c'). Given that constant rate/speed, tipping over the first block will cause all blocks to fall down, tipping over the last block some time later. Time delay calculates as distance divided by 'c'.

Now, create 'extreme conditions', where the first domino block is down, the last one is still standing, and halfway down the row, blocks are falling, but not quite down on the floor. Then, observe the 'wave front' of falling domino blocks. It will appear to move faster than the previously determined 'c'. How come?

Look more closely: as each block falls down, there's a fixed delay before it hits the next block. But what happens under our 'extreme conditions'? At the exact time a previous block would have hit the next one (under normal circumstances), that next block is already falling down! The time it takes for the 1000 blocks to fall down, is less than what normally would be expected.

Did this 'c' constant get violated? Nope, it still took the same amount of time for each block to fall down. Was the maximum 'c' speed exceeded? Nope. After tipping the first block, it still took the same amount of time before this 'information' was passed on to the next block. With a set of 1000 blocks all standing, the time needed for an initial 'disturbance' to be passed on to the last block, is still limited by 'c'.

So these 'extreme conditions' are like pre-tipping each block, and let you observe something that appeared to move faster than 'c'.
Nice for the lab folks, but other than that, sensationalist journalism. Wake me up when trans-atlantic ping times (sending actual packets with random data) dive below the time dictated by the speed of light.

here is my example

[deathcow]

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

[Rakshasa Taisab]

A nice example, but what is it supposed to show?

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

[digitig]

A nice example, but what is it supposed to show?

The difference between phase and group velocity, presumably.

Re:here is my example

[ComaVN]

Actually, it shows that some things we, humans, perceive as an entity (the pattern of light and shadow), are not actually physical objects, and thus are not governed by the same laws as physical objects (such as v<c)

The same goes for group velocity.

Re:

[knewter]

Then you should make a killing making 'optical occlusion' interconnects for processors. Think how you could dominate those silly optical interconnects :) Freaking lowly 'c' speed...

Re:here is my example

[FractalZone]

A nice example, but what is it supposed to show?

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

[hotdiggitydawg]

Obligatory Steven Wright:

"I put instant coffee in a microwave oven and almost went back in time."

Re:

[anagama]

From the "100 reasons why coffee is better than women": instant coffee.

Re:here is my example

[kickedfortrolling]

you're just lucky you're not in soviet russia- where i understand the subject and objects of a statement are reversed for the sake of comedy

Re:here is my example

[Anonymous Coward]

In soviet russia, the subject and objects reverse YOU!

Re:

[Altus]

What makes you think a can of coffee isnt hot?

The Japanese have been doing this shit forever.

Re:here is my example

[Gerzel]

We do! We just send some stuff to other places in the past to make you feel better about yourselves.

Re:here is my example

[The Warlock]

Exactly. And it's gotten a lot easier now that we've figured out how to break the speed of light.

Re:

[Flodis]

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 ju

Re:

[Mr2cents]

here --> . --

Indeed, that was the point you missed.

Re:It works...

[BigBuckHunter]

I was under the impression that they simply used waves within a medium already moving close to the speed of light to overcome the Fitzgerald contraction (avoid addition of velocities). In my mind, it would work like the following....

Drive a bus at .99C. Have the back row stand and sit. Then the next row stand and sit, then the next, so you get a wave going from the back of the bus. If you get people doing the wave fast enough, the wave may exceed the speed of light while the transport mechanism does not.

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...

[MustardMan]

I could be totally and absolutely wrong about all of this.

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.

Re:

[shellbeach]

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 ...

Re:

[TriezGamer]

The only mental image that gives me is of a man hitting the piece of rebar, adding some rotational velocity, and getting slapped by the tail end of it as it passes...

Re:

[Fastolfe]

Time dilation would prevent us from agreeing on your speed or changes in your speed. Since you're traveling at c-1mph, time is passing MUCH more slowly for you than it is for me. When you add 5mph to your speed, since we disagree about what an "h" in that "mph" is, I see a far more modest increase in your speed. From my perspective, no matter how fast you try to go, you'll always be slightly slower than the speed of light.

From your perspective, however, this isn't true. With enough energy (a hopelessly

Not all forces travel at 'c'...

[Roger W Moore]

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!

Re:

[XchristX]

The formula momentum=mass*velocity is a formula for the MECHANICAL momentum, which is just ONE kind of momentum. There are many kinds of momenta.

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...

[FuzzyDaddy]

Actually, group velocity can exceed c - even though no information is transferred faster than c.

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.

Re:

[Old Wolf]

Actually it's nothing like that, but don't let facts get in the way of a good post.

Re:It works...

[jimmydevice]

Researchers note that the equipment was set to 11 to produce the results.

Re:It works...

[EinZweiDrei]

'Nothing travels faster than the speed of light with the possible exception of bad news, which obeys its own special laws. The Hingefreel people of Arkintoofle Minor did try to build spaceships that were powered by bad news but they didn't work particularly well and were so extremely unwelcome whenever they arrived anywhere that there wasn't really any point in being there.'

Re:

[808140]

Parent's quote is from Mostly Harmless, by Douglas Adams... it's good to cite your sources, EinZweiDrei.

Results of experiment published in the past

[Epsas]

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!

Re:Results of experiment published in the past

[darkitecture]

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

[unitron]

So the dupe will be posted 6 years ago? Awesome! I'm looking forward to it.

Shouldn't you be looking backward to it?

Re:

[Anonymous Coward]

Dang, no wonder I missed it next time around.

Re:

[Tjp($)pjT]

Some guy named ocaT rednammoC failed to publish it then. Said something about his cat being dead. Last seen walking backwards through red curtains on a checkerboard floor. Well at least that's what they will say on the street in 2000.

Re:

[@madeus]

Some guy named ocaT rednammoC failed to publish it then. Said something about his cat being dead. Last seen walking backwards through red curtains on a checkerboard floor.

My chances of understanding the science involved in this experiment are still greater than my chances of understanding what the hell was going in that show [wikipedia.org] (funny, I thought it was checkerboard too...).

Re:Results of experiment published in the past

[Siener]

So the dupe will be posted 6 years ago? Awesome! I'm looking forward to it.

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 ... we finally have proof that dupes travel faster than the speed of light!

So which one is the dupe?

[EmbeddedJanitor]

This is going to make /. dupe identification pretty hard!

Re:

[Who235]

What exactly the researchers achieved, and what they claim, can only be determined at this point by subscribers to Nature.

Well, subscribers who keep their back-issues anyway.

Re:

[acidrain]

Wow. I'm seriously thinking of filtering kdawson. I mean at least Jon Katz... err nevermind...

Sounds Familiar -

[RoffleTheWaffle]

I think we've heard about this before. Something about atoms reacting in this big wave faster than light would travel, without anything actually moving faster than light.

Anyone got a name for that? I'm lost on it.

Group Velocity Again

[Effugas]

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.

Re:Group Velocity Again

[julesh]

Exactly. It's exactly the same experiment we've seen time & time again, and it's meaningless because no information is transmitted.

Re:

[TapeCutter]

I agree, debunking the same psudeo-scientific crap over and over again is boring.

no information?

[someone1234]

I just don't understand the following: the pulse/no pulse thing is itself a bit of information.

Re:no information?

[julesh]

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.

Re:

[achurch]

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.

Re:

[Anonymous Cowled]

Ah... the good old /. car analogy ;-)

Re:Group Velocity Again

[physicsnick]

Exactly.

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

[jez9999]

So YOU were the one causing that damn red blob when I was trying to watch the eclipse? Go test out your new laser toy elsewhere!

Re:

[XchristX]

You sure about this?

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

Re:

[Deliveranc3]

Um then some force or energy is passing through the mass, moving faster than light...

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

Re:

[jmv]

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.

Re:

[physicsnick]

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

Re:

[ArsenneLupin]

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

Re:

[fabs64]

... I think you have missed the whole point in ANY analogy

Information?

[Jugalator]

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 [wikipedia.org].

Re:Information?

[ZeroExistenZ]

Nothing can ever exceed speed of light, not even information,as proved by Hawking.

That, and earth is a sphere in the center of the universe, as Plato proved.

Fair enough...

[im_thatoneguy]

The poster can't figure out exactly what their news item is about. What the author of TFA claiming, or what conclusions we should reach. Sounds like just another day on Slashdot.

Re:

[Tim C]

That's not the poster saying that, that's kdawson - all of PreacherTom's words are in the blockquoted section.

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 . . .

[OverlordQ]

"Good. No, the answer is an orange and two lemons."

"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.

[Futurepower(R)]

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?

--
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

[JRHelgeson]

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. :)

Re:Slashdot is not the proper forum for speculatio

[Danny Rathjens]

You can't even figure out where your .sig is supposed to go and you are whining about editors? Just filter his stories in your preferences if you can't stand his article selections or frequent mistakes.

Then what is it?

[Flying pig]

Slashdot is, I believe, Rob Malda's blog and as such whatever he sees fit to include is proper content. In fact, the parent post is so completely up itself that it is looking at its kidneys from the inside. +5 informative? -5 troll more like. And I've just fallen for it - so it works!

Obligitory Futurama

[Rik Sweeney]

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.

Re:

[sumdumass]

I get it know. The ship's engines don't move the ship at all, It moves the universe around the ship.

Ok, lemme take a poke at what is might be

[realcoolguy425]

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 conceptio

Old news

[sdxxx]

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.

Old, Old News

[Frodrick]

From the article:

Last Updated: Friday, November 10, 2000 | 11:57 PM ET

Funny

[__aahlyu4518]

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."

How do I mod down kdawson and the /. editors?

[osu-neko]

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. >:(

Re:

[SharpFang]

http://slashdot.org/firehose.pl [slashdot.org]

Re:

[sumdumass]

Simple. Troll like the others. Goto their user page, find articles they have posted in that you havn't and start modding comments troll and flaim bate.

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.

Re:

[jez9999]

You might have been able to contribute to its not being considered by modding it down in the Firehose beforehand...

One way

[edwardpickman]

Physics wouldn't allow it unless the light travelled 1/300 the distance. Gas wouldn't do it but within known physics it could happen with severely warped space. No laws are broken if the distance is shortened. Obviously that isn't what happened in this case.

A few misconceptions

[jandersen]

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.

Question

[Lord Aurora]

Ok, so all this nonsense about group velocity and whatnot tickles inside of me like so much uncooked rice, and I have a little question. Say you set up a couple million little blocks across the Atlantic Ocean. Block 1 is set to pop up at 12:00, Block 2 at a time just the tiniest bit afterwards, and so on, so eventually what you have is a wave of blocks popping up, and let's say this 'wave' 'moves' faster than the speed of light. Follow? Now, put the blocks inside a perfect vacuum, slope their tops toward th

Re:

[Skrynkelberg]

Briefly explained: As the ball's velocity increases, so does it's mass, thanks to special relativity. That means it will take more time to accelerate and you will never actually reach the speed of light, no matter how long the slope.

Wrong, sorry

[Moraelin]

Well, no. The short answer is that there still is no way to make the bouncy ball move faster than light, or even at the speed of light.

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...

[tgv]

Well, it's from Nature 406 (6793): 277-279 Jul 20 2000. The article is cited 315 times and seems dispted. Here is the abstract for those poor souls without access to Nature, Web of Science, Scopus, etc.:

Einstein's theory of special relativity and the principle of causality(1-4) imply that the speed of any moving object cannot exceed that of light in a vacuum (c). Nevertheless, there exist various proposals(5-18) for observing faster-than-c propagation of light pulses, using anomalous dispersion near an absorption line(4,6-8), nonlinear(9) and linear gain lines(10-18), or tunnelling barriers(19). However, in all previous experimental demonstrations, the light pulses experienced either very large absorption(7) or severe reshaping(9,19), resulting in controversies over the interpretation. Here we use gain-assisted linear anomalous dispersion to demonstrate superluminal light propagation in atomic caesium gas. The group velocity of a laser pulse in this region exceeds c and can even become negative(16,17), while the shape of the pulse is preserved. We measure a group-velocity index of n(g) = -310(+/-5); in practice, this means that a light pulse propagating through the atomic vapour cell appears at the exit side so much earlier than if it had propagated the same distance in a vacuum that the peak of the pulse appears to leave the cell before entering it. The observed superluminal light pulse propagation is not at odds with causality, being a direct consequence of classical interference between its different frequency components in an anomalous dispersion region.

For another, more understandable report, here is a BBC website: http://www.whyevolution.com/einstein.html [whyevolution.com] (search for Wang).

Just Horrible

[fonik]

For those who want to see how this REALLY works...
http://gregegan.customer.netspace.net.au/APPLETS/2 0/20.html [netspace.net.au]

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

[TheThiefMaster]

That link made me understand it. I especially like how if you put a break in the beam then the superluminal pulse disappears when it gets to the break and then re-appears on the other side, proving without a doubt that it can't be used for data transfer.

This research was done in 2000

[Anonymous Coward]

In fact, this research is so old that Dr. Lijun Wang's FAQ page describing the experiment is no longer on the Internet. It has to be located through the Internet Archive: http://web.archive.org/web/20041012175312/www.neci .nj.nec.com/homepages/lwan/faq.htm [archive.org]

Here's what he said:

Q. How to interpret those earlier press coverage?

A. It has been mistakenly reported that we have observed a light pulse's group velocity exceeding c by a factor of 300. This is erroneous. In the experiment, the light pulse emerges on the far side of the atomic cell sooner than if it had traveled through the same thickness in vacuum by a time difference that is 310 folds of the vacuum transit time.

In our experiment, a smooth light pulse of about 3-microsecond duration propagates through a specially prepared cesium atomic chamber of 6-cm length. It takes 0.2 nanosecond for a light pulse to traverse a 6-cm length in vacuum. In our experiment, we measured that the light pulse traversing through the specially-prepared atomic cell emerges 62 nanosecond sooner than if it propagate through the same thickness in vacuum. In other words, the net effect can be viewed as that the time it takes a light pulse to traverse through the specially prepared atomic medium is a negative one. This negative delay, or a pulse advance, is 310 times the "vacuum transit time" (time it takes light to traverse the 6-cm length in vacuum).

Q. Is Einstein's Relativity violated?

A. Our experiment is not at odds with Einstein's special relativity. 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.

However, our experiment does show that the generally held misconception "nothing can move faster than the speed of light" is wrong. The statement only applies to objects with a rest mass. Light can be viewed as waves and has no mass. Therefore, it is not limited by its speed inside a vacuum.

Information coded using a light pulse cannot be transmitted faster than c using this effect. Hence, it is still true to say that "Information carried by a light pulse cannot be transmitted faster than c." The detailed reasons are very complex and are still under debate. However, using this effect, one might be able to increase information transfer speed up to c. In present day technology, information is transmitted at speed far slower than c in most cases such as through the Internet and inside a computer.

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

[Joebert]

If a warzoot went faster than light in outterspace, & nobody was there to see it, did it really go faster than light ?

Only if it leaves behind somthing similar to a log.

"cannot - impossible " etc etc

[unity100]

such words should never be used for things related to technology/science. likewise words were spent in abundance in 19th century for a limitless number of proposed stuff, and naysayers have always been proved wrong. Science always moves forward, and nothing is impossible in the universe.

The fastest thing in the universe is...

[Stormwatch]

Three friends were at a bar, drinking and chatting.

- 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

[fire-eyes]

Maybe it's due to the time bending effects of this, but the space shuttle already beat them.

CNN doesn't lie!
http://fire-eyes.org/gal/v/hmr/cln/shuttleisfast.j pg.html [fire-eyes.org]

thiotimoline

[bobv-pillars-net]

Was I the only one who skimmed the story header and thought of Thiotimoline? [wikipedia.org]

Back in time vs forward in time

[EmbeddedJanitor]

"at least back in time."

If x travels forward in time isn't that equivalent to (universe - x) travelling back in time?

Re:

[sumdumass]

Only to the perspective of the one moving forward wich means :depends on who you ask.".

Re:

[someone1234]

I thought vacuum means there is no material. Surely physics evolved beyond me :)

Re:

[feyhunde]

Vacuum has an N of 1. It's possible to be faster than vacuum, but in terms of Group Velocity, which is useless to send encoded information on.

Re:You can beat it!

[cyclop]

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...

[someone1234]

...like in the star gate episode, i would rather not want to see all those extradimensional critters!

Re:

[feyhunde]

Thats what happens when particles that are traveling faster than the speed of light in one material enter another. It's faster in Uranium than water, resulting in the particles having to give up the extra energy.

Has your enormous, rigid rod gone floppy?

[Pfhorrest]

I seem to remember reading about the following hypothetical experiment:

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

Re:

[Ingolfke]

Um... Minitrue states very clearly that its experts cannot be wrong. How dare you question them.