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An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Messages Fly No Faster Than Light
15 October 2003 (All day)
Faster-than-light tricks are old hat; in the past few years, scientists have performed "superluminal" experiments using weird quantum effects, special mirrors, and cells full of vapor. What would be really exciting--and a violation of Einstein's theory of relativity--is if someone could use these techniques to send a message faster than the speed of light. Now three American scientists have made the most well-controlled trial of sending faster-than-light messages and failed, implying that there are no loopholes in Einstein's speed limit.
The most impressive type of superluminal experiment uses a chamber of gas with a property known as "anomalous dispersion." When a pulse of light--which is made up of a bunch of superimposed waves--shines through such a chamber, the gas shifts some of the waves in such a way that the pulse appears to travel faster than the speed of light (ScienceNOW, 21 July 2000).
In the 16 October issue of Nature, Daniel Gauthier of Duke University in Durham, North Carolina, and colleagues describe experiments in which they transmitted light pulses through just such a chamber of potassium vapor. At first glance, it looks as if a light pulse travels through about 27 nanoseconds faster than the speed of light would allow. But when the scientists tried to transmit information with that speeded-up light--by tweaking the amplitude of the pulse to represent a 1 or a 0--the modification came through the chamber slower than the speed of light even as the pulse itself came through faster. "Even though you're receiving photons faster, you're not gaining information from those photons," says Gauthier. "It's consistent with special relativity."
Aephraim Steinberg, a physicist at the University of Toronto, calls the experiment "beautiful." But although mainstream scientists agree that it's not possible to use superluminal signals to transmit information, there are subtle loopholes in any experimental setup that would allow the possibility of superluminal information transfer. "I don't think you can ever completely convince the hardliners," says Steinberg. However, he adds, "they've done about as good a job as you could imagine doing."