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Thursday, August 14, 2008

Spooky Physics: Signals Seem to Travel Faster Than Light

By Charles Q. Choi, Special to LiveScience

Strange events that Einstein himself called "spooky" might happen at least 10,000 times the speed of light, according to the latest attempt to understand them.

Atoms, electrons, and the rest of the infinitesimally tiny building blocks of the universe can behave rather bizarrely, going completely against the way life as we normally experience it. For example, objects can sometimes be said to exist in two or more places at the same time, or spin in opposite directions simultaneously.

One consequence of this murky realm of quantum physics is that objects can get linked together, such that what happens to one instantaneously has an effect on the other, a phenomenon dubbed "quantum entanglement." This holds true no matter how far apart these objects are from each other.

Einstein rebelled against the notion of quantum entanglement, derisively calling it "spooky action at a distance." One could instead argue that an entangled object releases an unknown particle or some other signal at high speeds to influence its partner, giving the illusion of a simultaneous reaction.

In the past, experiments have ruled out any suspects for such hidden signals from the realm of classical physics. Still, one exotic possibility remains — that such x-factors instead travel faster than the speed of light.

To investigate this possibility, scientists at Geneva in Switzerland began with entangled pairs of photons, or packets of light. These pairs were then split up and sent over fiber optic cables provided by Swisscom to stations at two Swiss villages some 11 miles (18 kilometers) apart from each other. The stations confirmed that each pair of photons had remained entangled — by analyzing one, scientists could predict aspects of its partner.

For any hidden signal to travel from one station to the other in just 300 trillionths of a second — the rapidity at which the stations could accurately detect the photons — any such x-factor had to go at least 10,000 times the speed of light.

As much as Einstein might have disliked the notion of quantum entanglement, he also revealed that signals could not get transmitted faster than light. Any faster-than-light "spooky action at a distance" is therefore implausible, said researcher Nicolas Gisin, a physicist at the University of Geneva. Instead, "what's fascinating here is that we see that nature is able to produce events that can manifest themselves at several locations," he said.

In a sense, these instantaneous events "seem to happen from outside space-time, in that it's not a story you can tell within space-time," Gisin told LiveScience. "This is something that an entire community of scientists is already studying very intensively."

Gisin and his colleagues detailed their findings in the August 14 issue of the journal Nature.

Original here

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