Wednesday, September 5, 2007

Light in Reverse Gear - The backward moving pulse

Ever thought of reversing the light?? Yeah thats not a trick , not at all
In the recent years scientists have started to "PUSH LIGHT INTO REVERSE". Hey that in no way turning off the lights (haha!!)
From everybody's knowing and common sense light is known to travel fastest. And according to Einstein if something could move faster than that , then it can be seen reaching its destination before it left its starting position. Laugh !!! LOL .. think how can that be possible. So according to him nothing can do that

But researchers found that "back-ward moving pulse of light is faster" than that. Pretty Confused !!
Yeah!! Now that is putting light into the reverse gear. So everything now seems to have reverse gear. Read more at : Light’s most exotic trick yet: so fast it goes backwards?

The article is as below:
In the past few years, physicists have found ways to make light go both faster and slower than its usual speed limit. Now researchers say they’ve gone a step further: pushing light into reverse.
As if to defy common sense, they say, the backward-moving pulse of light travels faster than light.
Confused? You’re not alone.
“I’ve had some of the world’s experts scratching their heads over this one,” said Robert Boyd of the University of Rochester in Rochester, N.Y., one of the researchers. “It’s weird stuff.”
“Theory predicted that we could send light backwards, but nobody knew if the theory would hold up or even if it could be observed in laboratory conditions.”

Einstein determined that nothing can be accelerated to a speed greater than that of light in a vacuum. That’s about 300,000 kilometers (190,000 miles) per second. If something broke that limit, then some observers could see it reach its destination before it left, violating a universal law of causality. But physicists in recent years have reported finding tricks to slow light to a near-standstill, or even speed it up in apparent violation of Einstein’s rule. Now, Boyd said, he’s taken what was once just a mathematical oddity—negative speed—and shown it working in the real world. The findings are published in the May 12 issue of the research journal Science. Boyd and colleagues sent bursts of laser light through an optical fiber laced with the element erbium. An optical fiber is a thin, transparent tube that transmits light by letting it bounce along its interior. “The pulse of light is shaped like a hump with a peak,” Boyd explained. “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.”
To understand how light’s speed can be manipulated, think of a funhouse mirror that makes you look fatter. As you first walk by the mirror, you look normal. But as you pass the curved portion in the center, your reflection stretches. The far edge seems to leap ahead of you momentarily.

In the same way, a pulse of light fired through a special material may move at normal speed until it hits the substance, where it is stretched out to reach and exit the material’s other side .
Conversely, if the funhouse mirror were the type that made you look skinny, your reflection would appear to suddenly squish together, with the leading edge of your reflection slowing as you passed the curved section. Similarly, a light pulse can be made to contract and slow inside a material, exiting the other side later than it naturally would.

To visualize the backward-moving light pulse reported by Boyd, replace the mirror with a TV and video camera. As you may have noticed when passing such a display in an electronics store window, as you walk past the camera, your on-screen image appears on the opposite side of the TV. The image walks in the direction opposite to yours, and thus toward you. It passes you in the middle, and continues until it exits the other side of the screen.

A negative-speed pulse of light would ................ read full article

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