“This is a very clean experiment,” said Chiao. Others who are critical said they did not know the experiment in enough detail to comment publicly.īut many who have read the actual report are impressed. ![]() Several physicists who are critical of the work declined to be interviewed about their reservations. Some of the early experiments were not as acceptable to physicists because the light waves that were accelerated were absorbed or distorted by the equipment used in the experiments.Īt least some physicists, however, remain skeptical of the experiment, which has been the topic of private mutterings among some academics who disagree with the conclusions. Earlier descriptions of superluminal pulses of light date back to 1970 and include work by Stephen Chu, a Nobel-winning physicist at Stanford.īut those early experiments did not attract much attention or many converts and lay dormant for several years, Steinberg said. The effect is very dramatic,” said Steinberg, who had conducted similar research in 1993. The latest experiment is one in a series of tests in optics research showing that light pulses can be superluminal, or move faster than the speed of light, if they are sent through special materials.ĭata from the current experiment is “very nice and very clear. The experiment was conducted by Wang, Alexander Kuzmich and Arthur Dogariu, all physicists at the NEC Institute, a basic research arm of computing giant NEC. That transit time was incredibly short: two-tenths of a billionth of a second. ![]() That allows the cesium atoms in the chamber to spit out a light beam before the entering pulse has fully reached them.Īs a result, the time needed for the pulse to move through the cell is about one three-hundredth the time it would normally take light to travel the length of the cell in a vacuum. A precisely tuned third laser soaked up the excess energy and shot out of the cell at a speed faster than light.Īccording to Wang and several other physicists, the reason the light behaves the way it does is that when the leading edge of that third laser pulse begins to enter the chamber, it carries with it all the information needed to reconstruct the entire light wave. They shot the cell with two laser pulses that raised each of the cesium atoms in the vapor to a specific altered energy level. In this case, the experimenters used a clever and highly artificial creation-a 2.4-inch glass cell filled with cesium vapor. While that is a feat, experiments to accelerate light beyond light speed are considered much more difficult. Physicists at Harvard and Berkeley have shown in the last year that they can slow light-in one case down to the speed of an Olympic runner. Passed through very particular materials that physicists can create in their labs, light can begin to act very strangely. The pulse, like a wave in the ocean, has a peak, but also a leading edge that precedes it. Here are the details: A pulse of light is actually an ensemble of waves of different frequencies. “Unfortunately, energy and information still can’t break any speed limits,” said Steinberg. That’s because meaningful information consists of complex signals that could not take the same “shortcut” across space as a simple light pulse. It’s agreed by most physicists that information carried by a light pulse still has a speed limit. Currently, because of electrical effects, information travels across computer circuits at a relative crawl, moving across a tiny chip in the same time that light jumps a foot or more. ![]() The experiments do offer hope, however, that information may one day travel across computer systems and the Internet much faster than is now possible. While some more fanciful minds see a future of warp speed and time travel arising from such experiments, scientists say those ideas remain fantasies. “No, you can’t kill your ancestors,” he said. The new experiment does not mean that ordinary objects somehow can go backward or forward through time, said Chiao, an expert in the field of quantum optics, the study of the quantum nature of light. “Einstein’s theory of relativity still holds,” Wang said. Ultra-fast light pulses are possible-and explainable in the world as we know it-because light, unlike matter, has no mass and can be viewed as a series of particles and as waves. The physicists are clear on one point-nothing in the new experiment actually contradicts Einstein’s theory.
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