If you thought the trillion-year crunch was mind-boggling, how about light that moves backwards, and does so at speeds faster than c? From the University of Rochester comes word that Robert Boyd, a professor of optics there, has slowed light to negative speeds. To do this, the experimenter sent a pulse of laser light through an optical fiber laced with the element erbium. Leaving the laser, the light pulse was split, with one pulse going into the fiber and the other left undisturbed for reference.
The remarkable result: The peak of the pulse emerged from the other end of the fiber before it entered the front of the fiber, and ahead of the reference pulse. “Through experiments we were able to see that the pulse inside the fiber was actually moving backward, linking the input and output pulses,” says Boyd, who acknowledges “I’ve had some of the world’s experts scratching their heads over this one.”
Centauri Dreams hardly qualifies as an expert, but head-scratching does seem in order here. Boyd is quick to note that there is no violation of Einsteinian principles involved. What Einstein said was that information cannot travel faster than light, and no information is required to do that in these experiments. Boyd again:
“The pulse of light is shaped like a hump with a peak and long leading and trailing edges. The leading edge carries with it all the information about the pulse and enters the fiber first. By the time the peak enters the fiber, the leading edge is already well ahead, exiting. From the information in that leading edge, the fiber essentially ‘reconstructs’ the pulse at the far end, sending one version out the fiber, and another backward toward the beginning of the fiber.”
Can a pulse be designed without a leading edge? Einstein’s work would imply that if it can, the reverse light phenomenon will disappear. Reverse light thus becomes an interesting test of Einstein, though one that still confounds this writer. Animations of fast light, slow light and backward light may help. The paper is Gehring, Schweinsberg, Boyd et al., “Observation of Backward Pulse Propagation Through a Medium with a Negative Group Velocity,” in Science 12 (May 2006), pp. 895-897.
I agree, some definite head-scratching is in order here! I don’t quite understand why the leading edge of the pulse doesn’t carry with it any information.
Uh, isn’t the mere fact that a pulse is detected, information? Maybe it’s just a reflection?
I’m with Eric on this one; I would assume a pulse detection is itself information, but maybe Boyd’s subsequent work will clarify this.
the light can travel backward in time,because when a left-handed object travel with speed faster than light,it if transform into right-handed object,with our violate causality,by the object is torsed and deformed to half of a curvature of space-time,that is backward in time and the half is forward in time.then the linearity of space-time is broken,and does appear others continuties of space-time,that measure other time and space.then in 4-D world the left-right handness worlds are differents,permiting that the does transposition of energy( backward in space-time as holes of energy or negative space-time).
some extende theories to the RT permit speed greater than speed light of continuity of space-time.then the speed light cannot be isotropic in the space.then as the space is left-right handed, then the space is deformed by the time through of non-linearity that is generated by spontaneous breaks of pt ,where the space is curved by time through two opposed torsion that generate curvatures produced by two antipodes torsion made in the four dimension that would be coupled to 5-d,because the time woud be given by two opposed rotations,asymmetric that are semi-curves in space,generating then continuos space-time as only one entity.therefore there are particles that travel with speeds greater than of the light,known.then the negative refrangibily index is similar at changes of topology,our topologic deffects that produces the neighboorings through of the non-homogeinities and differents of the fibres or of the space-time.
Putting the Brakes on Light Speed
Washington Post, Jan. 18, 2007
Researchers at the University of Rochester have achieved a long-sought goal of slowing waves of light to one-three-hundredth of its normal velocity and using those harnessed pulses to store an image.
Physicists said the new approach to taming light could hasten the arrival of a futuristic era in which computers and other devices will process information on optical beams instead of with electricity.
The researchers created a four-inch-long chamber filled with cesium gas heated to about 212 degrees Fahrenheit. When they sent pulses of laser light through that gas, the cesium atoms put the brakes on the leading edge of that wave, creating a photonic traffic jam.
In one experiment, the image was clear even when a single photon was beamed through a stencil.
http://www.kurzweilai.net/news/frame.html?main=/news/news_single.html?id%3D6308
Two relativity tests are better than one (Jun 28)
http://physicsweb.org/article/news/11/6/17
Simultaneous tests of EinsteinâEUR(TM)s special theory of relativity
performed in Europe and Australia have allowed physicists to conclude
that the speed of light is constant in all directions, without having to
make an important assumption that had limited the validity of previous
tests. The researchers performed two different types of Michelson-Morley
experiment — one on each continent — which allowed them to rule out,
for the first time, violations of EinsteinâEUR(TM)s theory that could
affect the physical properties of the experimental equipment and change
the outcome of the measurement (arXiv:0706.2031v1).