Posted on 08/24/2005 6:02:52 PM PDT by Arkie2
Researchers in Switzerland have succeeded in breaking the cosmic speed limit by getting light to go faster than, well, light.
Or is it all an illusion?
Scientists have recently succeeded in doing all sorts of fancy things with light, including slowing it down and even stopping it all together. Now a team at the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland is controlling the speed of light using simple off-the-shelf optical fibers, without the aid of special media such as cold gases or crystalline solids like in other experiments.
“This has the enormous advantage of being a simple, inexpensive procedure that works at any wavelength,” said Luc Thévenaz, lead author of the study detailing the research.
Using a technique called Stimulated Brillouin Scattering, the researchers were able to slow down or ratchet up the speed of light like the gas pedal on a car. They succeeded in reducing the speed of light by almost a factor of 4 (although that’s still plenty fast at 46,500 miles per second), but even more dramatically, the team was also able to speed up the speed of light.
Light in a vacuum travels at approximately 186,000 miles per second, but a popular misconception is that, according to Einstein’s special theory of relativity, nothing in the universe can travel faster than this speed.
This seeming paradox can be resolved because a pulse of light is actually made up of many separate frequency components, each of which moves at their own velocities. This is known as the pulse’s phase velocity. If all the frequency components have the same phase velocity, then the overall pulse will also appear to move at that velocity.
However, if the components have different phase velocities, then the pulse’s overall velocity will depend on the relationships between the velocities of the separate components. If the velocities differ, the pulse is said to be moving at the group velocity.
By tweaking the relationship between phase velocities, it’s possible to adjust the group velocity and create the illusion that parts of the pulse are traveling faster than the speed of light.
One area where such an advance could be enormously beneficial is in the telecommunications industry.
Although information can be channeled through fiber optics at the speed of light, it can’t be processed at this speed because with current technologies, light signals must be transformed into much slower electrical signals before they are useful.
hevenaz’s technique would essentially allow light to be processed with light without a costly electrical conversion.
The group’s research will be published in an August 22nd issue of the journal Applied Physics Letters.
The phase velocity is not the velocity of light. It's sort of like when you see those old movies of an automobile rolling down the street and it looks like the wheels are moving backwards. They aren't really of course.
Much slower electrical signals? Hardly. The problem with electrical signals is not their speed, but the capacitance slowing down clear transitions, and the resistance at high frequency.
Somebody 'splain to me where this 'misconception' is, because I was pretty sure that one of Einstein's laws is exactly that.
Actually, you can go up to 186,282 MPH without getting a ticket.
Only because the radar guns max out at 185,500. Nyack!
That's alright; some of us won't read it until yesterday.
I probably take my ping list "responsibilities" too seriously. But I'd rather not have people dropping out because they get bothered by too many pings to trivial stuff. No one ever drops out because of too few pings.
I'm not sure what Arkie2 had in mind, but the inflationary big bang model has the universe briefly expanding FTL. I've seen various explanations as to why this doesn't create a problem, but it's probably because it doesn't involve any possible causality contradictions. Undoubtedly, an expert will pop in to show where I've botched this up. If so, I welcome the information.
Exactly. I've dropped ping lists before because the flood of pings is just too overwhelming.
That would be MPS. (And you wanted to be MY latex physicist...)
You have a ping list?
Uhh, well my statement is still true ;->
Of course you could also go faster, as in 186282 MPS.
If you'll look at the title of the article the note in parenthesis is mine. I'm aware nothing mentioned here violates Einstein's theories but it's intweresting from a technical viewpoint.
Actually, the most amusing aspect of this article is the note that scientists have slowed light to zero. If only it were true we would never have to worry about Hillary being elected prez!
That's what the said about the sound barrier.
The velocity they are talking about isn't anything real. It's the speed at which the interference patterns between the different light frequencies pass.
Think of it this way: Say you have two fans spinning at different speeds and you put one in front of the other in front of a light source. As the fans spin, you'll see a shifting pattern of light and dark as the fan blades interfere with each other in transmitting the background light. The speed at which these patterns change can be much faster than the spinning speed of the fans, but it's not a real velocity.
Likewise, when you put multiple frequencies of light together, you get a similar effect. Bands of interference will move in the same direction as the light, but can move much faster than the light itself.
Unfortunately, the moment you try to analyze the information carried by the interference patterns, you are once again restricted to the speed of light because you have to wait for a certain number of patterns to pass by, and amazingly, that number is just enough to slow the whole thing back down to the speed of light again.
The misconception is not being able to travel faster than light.
Actually, the relativity equations say no such thing. What they say is that you can't travel AT the speed of light, unless you are massless.
Once you get past the speed of light, the equations work again, except that a number of them have an imaginary component (sqrt-1).
A superluminary universe has some interesting properties according to relativity theory. Rest mass is at 2sqrt(2)c, doppler shifts are reversed, it takes infinite energy to slow DOWN to the speed of light, etc.
The sound barrier didn't require near-zero mass to break.
"Actually, you can go up to 186,282 MPH without getting a ticket."
But it is one massive ticket.
Yeah, that makes sense. It's like approaching a limit from the "other side."
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