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 Light Travels Backward Faster than Lightspeed?
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15831 Posts

Posted - 05/19/2006 :  11:54:28  Show Profile Send HalfMooner a Private Message
This item from LiveScience has me completely confused:

Light Travels Backward and Faster than Light
By Robert Roy Britt
LiveScience Managing Editor
posted: 18 May 2006
12:51 pm ET

It sounds nuts, but a scientist says his team has made light go backward. And this is not a simple trick of mirrors.

Previous work has slowed light to a crawl. But in the new research, a pulse of light is given a negative speed and—as if just to make your head spin—the researcher says the experiment made light appear to exceed its theoretical speed limit.

If you totally confused, don't worry. This reporter doesn't get it either. Nor do a lot of really smart scientists.

"I've had some of the world's experts scratching their heads over this one," says Robert Boyd, a professor of optics at the University of Rochester. "It's weird stuff."

The research was reported in the May 12 issue of the journal Science. Though not normally stated in news reports, Science is a peer-reviewed journal. That means some experts read Boyd's paper and said it was good to publish.

That said, nobody would blame you if you stop here. Otherwise, grab a couple aspirin, have a look at depictions of the experiment in this graphic or this animation, and read on.

We're going to let Boyd do the explaining. And this next sentence is the crux of it all:

"We sent a pulse through an optical fiber, and before its peak even entered the fiber, it was exiting the other end. Through experiments we were able to see that the pulse inside the fiber was actually moving backward, linking the input and output pulses."

"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."

. . .
Anoyone here in the physical sciences able to explain this to a layman?

Biology is just physics that has begun to smell bad.” —HalfMooner
Here's a link to Moonscape News, and one to its Archive.

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2998 Posts

Posted - 05/19/2006 :  12:24:36   [Permalink]  Show Profile  Visit pleco's Homepage Send pleco a Private Message
No, but I bet the YECers will site this as "proof" the earth is only 6K years old and the starlight we see from millions of years ago is not from millions of years ago.

by Filthy
The neo-con methane machine will soon be running at full fart.
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1536 Posts

Posted - 05/19/2006 :  12:38:34   [Permalink]  Show Profile Send furshur a Private Message
"As the pulse enters the material, a second pulse appears on the far end of the fiber and flows backward. The reversed pulse not only propagates backward, but it releases a forward pulse out the far end of the fiber. In this way, the pulse that enters the front of the fiber appears out the end almost instantly, apparently traveling faster than the regular speed of light."

This quote is clearly saying that the pulse of light essentially instantly causes a pulse of light at the far end of the fiber. That sure sounds like it violates Einsteins theory.

I can't find the source article but I sure would like to...

If I knew then what I know now then I would know more now than I know.
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760 Posts

Posted - 05/19/2006 :  13:40:29   [Permalink]  Show Profile Send dv82matt a Private Message
Very weird. I'm guessing this would be similar to Einstien's famous "spooky action at a distance".

The thing is that no actual information is being transmitted faster than light. All the information about the pulse is contained in the leading edge.
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4 Posts

Posted - 05/31/2006 :  20:58:50   [Permalink]  Show Profile Send Reztasohk a Private Message
The graphic, and even more-so the animation, helps a lot to illustrate what is going on here. Be sure to check out the OP's link.

Considering that the initial pulse cancels out with the backward pulse, I think the more amazing thing here is that the "new pulse" appears to be leaving from the other end before the initial pulse has even entered the medium. Whether this series of events is an illusion or a technological breakthrough, I think its downright phenomenal that light can essentially move faster than...the speed of light.

This link attempts to explain how this is able to occur.
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Skeptic Friend

313 Posts

Posted - 05/31/2006 :  23:07:20   [Permalink]  Show Profile Send woolytoad a Private Message
If you follow Rez's link, you see that nothing is actually moving faster than light.
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