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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.
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!
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."
Ah... the good old /. car analogy ;-)
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.
-- Patent no.123456: A way to personalize
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.
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.
Quidnam Latine loqui modo coepi?
That, and earth is a sphere in the center of the universe, as Plato proved.
I think we can keep recursing like this until someone returns 1
And then all of a sudden some wildlife jumps out onto the road and the driver slams on the brakes
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Indeed, that was the point you missed.
"It's too bad that stupidity isn't painful." - Anton LaVey
What makes you think a can of coffee isnt hot?
The Japanese have been doing this shit forever.
"In America, first you get the sugar, then you get the power, then you get the women..." -H. Simpson
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.
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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 generalized velocity for a particular generalized coordinate. Notice that I have not put mass anywhere into the definition.
This means that anything that has a generalized coordinate, a corresponding generalized velocity and a lagrangian has a momentum, even massless objects. The relation p = m*v (non-relativistic) can be derived as a special case from the lagrangian of massive objects. In the case of light, which is massless, the generalized coordinate is the electromagnetic vector potential, and calculations on the postulated lagrangian show that the momentum is a product of the electric and Magnetic field called the Poynting Vector. You do second quantization on this and you get massless photons of the same momenta. Notice that mo mass was needed.
Sorry if the above sounds too pedantic. Somebody else may be able to offer a less technical explanation...
Refs:
http://en.wikipedia.org/wiki/Lagrangian
http://scienceworld.wolfram.com/physics/Generaliz
http://scienceworld.wolfram.com/physics/PoyntingV
l'Homme n'est Rien l'Oeuvre Tout: Gustave Flaubert to George Sand
Actually it's nothing like that, but don't let facts get in the way of a good post.