Evidence for the Slowing Down of Light

Australian scientists have discovered that light isn't quite as fast as it used to be.

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Dr Charley Lineweaver, one of Davies' co-authors, along with graduate student Tamara Davis, explains that their paper works the other way around. They have taken observations and plugged the data into known mathematical formulas to determine that the speed of light has slowed.

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"Theorists always play with all kinds of crazy things," Lineweaver says. "The important thing here is we have experimental evidence . . . that's what's new here."

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The theory is based on observations made at the University of New South Wales by Dr John Webb in 1999 and further observations by one of his PhD students, Michael Murphy.

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It is hair-curling science. They looked at light from the most distant objects in the universe, quasars up to a billion times the size of our sun, which are 10 billion or 12 billion light years away.

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"The light that comes to you from a quasar has been travelling for most of the age of the universe - several billion years - and it carries with it information about what happened to it along the way," Murphy says.

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On its long journey, the light from those quasars has passed through gas clouds full of metals. The photons in the light - little packets of energy that make up the light itself - interact with the electrons in the gas clouds, charged particles that orbit the nuclei of the metal atoms. This leaves a fingerprint on the light as it arrives on Earth, called the fine structure constant, Murphy explains.

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When they measured the fine structure constant of this 12 billion-year-old light, Webb and Murphy found it was slightly higher than it would be today. Mathematically, there were two possible reasons for this - either the electric charge of the electrons had increased, or the speed of light had fallen.

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Using Stephen Hawking's formula for black hole thermodynamics, Davies, Davis and Lineweaver ruled out the electric charge possibility. By adapting Hawking's formula, they determined that an increase in electric charge would break the second law of thermodynamics, which says energy can only flow from hot spots to cold spots.

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"That's illegal. It would be like a cup of coffee sitting on your desk getting hotter," Lineweaver says.

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But while he is still cautious about the quasar observations, he says the implications are revolutionary if they hold true. "Supposing we do take it seriously, then we have some very profound things to worry about. One is, why is it doing this?"

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[This message has been edited by blitz77, 08-07-2002]

Current light years you mean... and if light was faster in the past it would have a smaller distance to travel since there would be less time for the universe to expand. If you want the actual Nature article, here it is.This paper argues that it must be c slowing down, as a change in e would violate 2LoT.