Kunnen we sneller dan het licht?

[legatus]

MONCTON, New Brunswick, Jan. 21 (UPI) -- Canadian scientists have sent electric pulses over long ranges at speeds faster than light for the first time.

The researchers believe their findings may one day help greatly increase computer and telecommunications speeds.

"The most important part of the finding is that it is the first time something -- anything -- was seen traveling over such distances at superluminal speeds," said lead researcher Alain Hache, a physicist at the University of Moncton in Canada.

The investigators stress it is not theoretically possible to send useful data at superluminal or faster than light velocities. However, they believe their results may help speed up electronics by more than half.

"Right now, the signal velocity in any wire -- a wire inside a computer chip, a phone wire -- is only a fraction of the speed of light," Hache said in an interview with United Press International. "One might one day accelerate those pulses up to the speed of light."

The speed of light is theoretically the fastest possible. First measured in 1675 by analyzing sunlight reflected off the moons of Jupiter, light speed is roughly 670 million miles per hour in vacuum -- fast enough to go around the Earth in about a tenth of a second.

The theory of relativity proposed by Einstein suggests exceeding the light barrier would lead to impossible results, such as cause after effect -- time travel. Scientists, however, have experimentally broken this speed limit for the past two decades, transmitting light pulses that move at superluminal speeds.

The key to understanding this apparently impossible phenomenon is to visualize a pulse of light as a group of waves all intermingled with each other. This group pulse rises and falls in energy over space, with a peak of strength in the middle.

Materials that absorb or disperse light can force the different waves in a group pulse to shift. The waves making up the rear of this pulse can be made to interfere with each other to drive the pulse's peak forward in space, resulting in the pulse traveling at superluminal speed.

Scientists were previously able to generate superluminal pulses of light over very short distances of only a few feet at most using very complex equipment. The research team managed to generate electric pulses that moved faster than light over a simple wire for the first time -- signals that moved at three times the speed of light over more than 500 feet.

The researchers connected a series of off-the-shelf store-bought wires together, each with different electrical resistance levels. This created reflections in the signals for the superluminal effect.

"The same laws that apply for light waves also apply for electrical waves," Hache explained.

Do not expect superluminal starships or time machines anytime soon, however. Since the energy that makes up the group pulse does not actually travel faster than light, the theory of relativity remains unbroken. A signal also gets weaker and more distorted the faster it goes, so it is theoretically impossible to send useful information at superluminal speeds.

However, the researchers do hope to use their reflection technique to help increase the speed of electrical signals traveling down existing telecommunication cables.

"At the moment, plain coaxial cables allow a velocity of about two-thirds the speed of light," Hache said. "By texturing the cable... we might bring that limit closer to light speed. There would be a lot of applications for that, like in computers when you send a bit from A to B."

Superluminal physics expert Mohammad Mojahedi, an electrical engineer at the University of Toronto, said this work may help move faster-than-light phenomena "from the physics aspect to the engineering aspects, to make faster devices."

(Reported by Charles Choi in New York.)

[timonx]

JA, maar volgens mij was het een paar andere gasten al eerder gelukt

[Hannibal]

timonx schreef:
JA, maar volgens mij was het een paar andere gasten al eerder gelukt

Scientists, however, have experimentally broken this speed limit for the past two decades, transmitting light pulses that move at superluminal speeds.

Lezen

[Demon of Fire]

Since the energy that makes up the group pulse does not actually travel faster than light, the theory of relativity remains unbroken.

Dus sneller dan het licht zoals jij het stelt is niet aan de orde.

Overgens hier een artikel over een ander experiment waarin ook geclaimd werd dat het sneller dat het licht gaat.

Faster Than Light?
By David Harris

Dateline: 08/05/00

You may have seen stories in the media recently about the speed of light being broken in an experiment at the NEC Research Institute, Princeton. The stories probably mentioned that light was passed through a caesium vapor and was observed to come out of the cell before it entered! The research paper appeared in a journal no less prestigious than Nature so is this the end of Einstein's rule of modern physics?

Despite the claims, there is no reason to believe that either Einstein's theory of special relativity or causality has been violated, a point that is discussed in the original paper. In fact, the whole speed of light issue is a bit of a red herring. It is true that "something" appears to move faster than the speed of light but that "something" does not carry information and it has been observed before and the fact that it happens is a direct result of Einstein's theory!

So what is going on?

About the experiment

The experiment involves sending a pulse of light through a chamber filled with a caesium vapor. We already need to clarify something in that first sentence. A pulse of light is not a simple object. It is not infinitely short in time, nor in space. The shape of the pulse is the critical part of the experiment. Any light pulse can be thought of as starting with an intensity smoothly rising from zero up to a maximum value and then dropping away again.

There are a number of ways that you can measure the position of a pulse of light. One way is to measure the location of the peak. Another is to measure the first detectable rise about zero, the front of the pulse. You could also define a point at which the pulse has risen to half the peak height. In fact, all of these definitions are used for different purposes. There are a few more measures you could also use.

Back to the experiment. A pulse of light was passed through a caesium vapor but the light did not just pass through unaffected. The light pulse was transformed in a very particular way. There are a few different ways to think about what happened.

One is to think of light as being like a wave. However, the only way to make a finite pulse out of waves is to combine a lot of different waves of different frequencies and wavelengths. Working out how to make up the combination is the subject of Fourier analysis. We won't go into the details here but just note that the pulse of light can be thought of as being made of many components, each of which has a different frequency.

This is important because different frequencies interact with the caesium vapor in different ways. You have seen this effect before when you look at a rainbow-each color of the rainbow is a different frequency behaving slightly differently. The effect in a caesium gas can be far more pronounced with some very strange results.

The caesium gas will preferentially absorb some frequencies and then re-emit them at later times and all sorts of other complicated interactions take place. The trouble with all of this is that the different components of the pulse are transmitted at different speeds so the pulse you have coming out is quite different to the pulse coming in. The process going on in the experiment is called anomalous dispersion.

Imagine a pulse of light...

The front, peak and half-heights can all be at different places relative to each other. Imagine a situation where a pulse begins to enter the caesium vapor chamber. Now imagine that the leading part of the pulse is transmitted much faster than the rest of the pulse because of the frequencies that make it up. This part of the pulse could start to exit the chamber before the peak of the entering pulse reaches the chamber. If the lagging part of the pulse was so spread out that the first part of the pulse exiting was the new peak, it would appear that the peak of the exiting pulse comes out before the peak of the entering pulse actually goes in.

If you were measuring the speed of the pulse as the speed of the peak, then it would appear that the pulse exits the chamber before it enters!

This is not exactly what happens in the experiment but just meant to give you an idea of how you have be extremely careful when you talk about the speed of pulses of light.

However, this is not enough to violate special relativity. If you wish to actually transmit information, you need to measure more of the pulse. When you work out the details, it turns out that you need to measure enough of the pulse to bring the total transmission speed back down below the speed of light in a vacuum.

So what's the verdict? Relativity is fine, causality is fine and the whole fuss is really a bit silly. The experiment is still an important one because it is the first time that anomalous dispersion has been demonstrated in a non-opaque medium. This is important for people who deal with light transmission, such as telecommunications companies but not much use to the person in the street.

Why all the fuss?

One of the reasons that there was a fuss is due to the way media sell stories to the public, the regular use of unrepresentative headlines and journalists' lack of understanding of the details of the experiment. A very interesting article about how the media dealt with this story and what was going on in the background can be read in Salon.com.


Artikel van Nature hier...
http://physics.about.com/gi/dynamic/...FUserReference =D82349EE46B4B617CE3BA729F59B39870D49


Overgens is er een mogelijkheid sneller dan het licht te gaan, maar dat is dan door middel van ruimtekromming.
Dus je zorgt er voor dat de afstand voor je kleiner wordt ten opzichte van je bestemming en achter je groter. Zoals Star trek. (zit meer wetenschap in Star trek dan je misschien zou denken )

Maar dan moet je weer voor zorgen dat je over anti-zwaartekracht beschikt, want een versnelling naar lichtsnelheid toe overleef je niet, het enige wat er van je over blijft is een hoopje pudding.

Groetjes
Ben(die zo van dienst is geweest