Speed of Light - NOT CONSTANT!!...
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Chicago Astronomer Joe
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Speed of Light - NOT CONSTANT!!... Aug 22, 2005 20:56:30 GMT -6
Post by Chicago Astronomer Joe on Aug 22, 2005 20:56:30 GMT -6
Speed of light made faster
Swiss researchers have successfully demonstrated for the first time that it is possible to control the speed of light in an optical fiber.
On the screen, a small pulse shifts back and forth – just a little bit. But this seemingly unremarkable phenomenon could have profound technological consequences. It represents the success of Luc Thévenaz and his fellow researchers in the Nanophotonics and Metrology laboratory at EPFL in controlling the speed of light in a simple optical fiber. They were able not only to slow light down by a factor of three from its well – established speed c of 300 million meters per second in a vacuum, but they've also accomplished the considerable feat of speeding it up – making light go faster than the speed of light.
This is not the first time that scientists have tweaked the speed of a light signal. Even light passing through a window or water is slowed down a fraction as it travels through the medium. In fact, in the right conditions, scientists have been able to slow light down to the speed of a bicycle, or even stop it altogether. In 2003, a group from the University of Rochester made an important advance by slowing down a light signal in a room-temperature solid. But all these methods depend on special media such as cold gases or crystalline solids, and they only work at certain well-defined wavelengths. With the publication of their new method, the EPFL team, made up of Luc Thévenaz, Miguel Gonzaléz Herraez and Kwang-Yong Song, has raised the bar higher still. Their all-optical technique to slow light works in off-the-shelf optical fibers, without requiring costly experimental set-ups or special media. They can easily tune the speed of the light signal, thus achieving a wide range of delays.
More here: www.physorg.com/news5929.html
Now I'm more confused than ever. Doesn't this screw up all theories now? Light year calculations are no longer prime, and wide fluctuations possible. They claim to have stopped light all together, and this is in a lab. What about the influences out there...in the universe(s) that exert influences on the photons?
Why isn't this bigger news?
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Post by Maddad on Aug 23, 2005 17:21:46 GMT -6
It may not be represented by the reporter as it was conceived by the scientist. If light really does change speed, then you start getting crazy answers. For instance, if you change a gram of matter into energy at the standard speed of light, and then change it back into matter when light's speed has been doubled, you get four grams of matter for your original one.
I suspect that what has been change is outward appearances, not the speed of light itself. For instance, when they were reporting that light slowed in a medium, what was happening was that light was bouncing from particle to particle, being absorbed and then re-emitted. This takes longer of course than just simple transmission.
If the universe is a ball the size of America, then the solar system is almost as large as the smallest cell in the human body.
Speed of Light - NOT CONSTANT!!... Nov 5, 2005 4:56:11 GMT -6
Post by Chicago Astronomer Joe on Nov 5, 2005 4:56:11 GMT -6
IBM Slows Down the Speed of Light...
Now...here's a story...
IBM slows light, readies it for networking
IBM has created a chip that can slow down light, the latest advance in an industrywide effort to develop computers that will use only a fraction of the energy of today's machines.
The chip, called a photonic silicon waveguide, is a piece of silicon dotted with arrays of tiny holes. Scattered systematically by the holes, light shown on the chip slows down to 1/300th of its ordinary speed of 186,000 miles per second. In a computer system, slower light pulses could carry data rapidly, but in an orderly fashion. The light can be further slowed by applying an electric field to the waveguide.
Full story here: tinyurl.com/d45gb
Perhaps IBM can create a computer/time machine now that will catch a crash before it happens...
Last Edit: Nov 5, 2005 4:57:13 GMT -6 by Chicago Astronomer Joe
Speed of Light - NOT CONSTANT!!... Nov 7, 2005 12:34:11 GMT -6
Post by Maddad on Nov 7, 2005 12:34:11 GMT -6
"Perhaps IBM can create a computer/time machine now that will catch a crash before it happens..."
Now you're expecting the impossible from science.
Speed of Light - NOT CONSTANT!!... Dec 14, 2005 2:32:48 GMT -6
Post by Chicago Astronomer Joe on Dec 14, 2005 2:32:48 GMT -6
Freezing Light
Scientists have slowed down and even stopped the fastest substance in the universe: light. As this ScienCentral News video reports, the research may lead to faster, more powerful computers.
Light sets the universe's speed limit. Nothing else moves faster. In just one second, an ordinary ray of light travels a distance equal to seven trips around the earth.
But now, physicist Matt Sellars has found a way to hit the brakes on light, slowing a speeding laser pulse and capturing it inside a crystal.
Sellars and his research team at the Laser Physics Center at the Australian National University in Canberra, Australia, managed to slow the laser light down from 670 million miles an hour to a mere 670 miles an hour — about the speed of a bullet being fired from a gun — before stopping it altogether.
"It's quite a bit faster than you can drive a car, but… we now have the ability to hold it for seconds at this stage and possibly longer," Sellars explains. That's longer than ever before, and long enough to be able to use light for quantum computing.
More here: www.sciencentral.com/articles/view.php3?article_id=218392702
Slowing light down, speeding it up...we will find out one day that it's just another form of energy that can be manipulated.
Speed of Light - NOT CONSTANT!!... Dec 14, 2005 12:31:43 GMT -6
Post by Maddad on Dec 14, 2005 12:31:43 GMT -6
What they might be missing in these reporters talking about science is that the restriction on the speed of light is its spped in a vacuum. Light's speed in a different medium, like glass, may be much slower. When you get a charged particle, like a proton, traveling through a medium faster than light can travel through that medium, you get a flash of light called cerenkov radiation. Monitoring those photons is how we count solar neutrinos.
I would be interested though in the logic explaining how photons travel faster than light in a vacuum. It needs to be more than a quantum fluctuation to be useful.
Speed of Light - NOT CONSTANT!!... May 13, 2006 0:21:22 GMT -6
Post by Chicago Astronomer Joe on May 13, 2006 0:21:22 GMT -6
Slowing down light to go in reverse
In the past few years, scientists have found ways to make light go both faster and slower than its usual speed limit, but now researchers at the University of Rochester have published a paper today in Science on how they've gone one step further: pushing light into reverse. As if to defy common sense, 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," says Robert Boyd, the M. Parker Givens Professor of Optics at the University of Rochester. "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."
Boyd recently showed how he can slow down a pulse of light to slower than an airplane, or speed it up faster than its breakneck pace, using exotic techniques and materials. But he's now taken what was once just a mathematical oddity—negative speed—and shown it working in the real world.
"It's weird stuff," says Boyd. "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."
So, wouldn't Einstein shake a finger at all these strange goings-on? After all, this seems to violate Einstein's sacred tenet that nothing can travel faster than the speed of light.
"Einstein said information can't travel faster than light, and in this case, as with all fast-light experiments, no information is truly moving faster than light," says Boyd. "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."
Boyd is already working on ways to see what will happen if he can design a pulse without a leading edge. Einstein says the entire faster-than-light and reverse-light phenomena will disappear. Boyd is eager to put Einstein to the test.
So How Does Light Go Backwards?
Boyd, along with Rochester graduate students George M. Gehring and Aaron Schweinsberg, and undergraduates Christopher Barsi of Manhattan College and Natalie Kostinski of the University of Michigan, sent a burst of laser light through an optical fiber that had been laced with the element erbium. As the pulse exited the laser, it was split into two. One pulse went into the erbium fiber and the second traveled along undisturbed as a reference. The peak of the pulse emerged from the other end of the fiber before the peak entered the front of the fiber, and well ahead of the peak of the reference pulse.
But to find out if the pulse was truly traveling backward within the fiber, Boyd and his students had to cut back the fiber every few inches and re-measure the pulse peaks when they exited each pared-back section of the fiber. By arranging that data and playing it back in a time sequence, Boyd was able to depict, for the first time, that the pulse of light was moving backward within the fiber.
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, with the far edge seeming to leap ahead of you (the reference walker) for a moment. In the same way, a pulse of light fired through special materials moves at normal speed until it hits the substance, where it is stretched out to reach and exit the material's other side [See "fast light" animation].
Conversely, if the funhouse mirror were the kind 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 much later than it naturally would [See "slow light" animation].
To visualize Boyd's reverse-traveling light pulse, replace the mirror with a big-screen 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 far side of the TV. It walks toward you, passes you in the middle, and continues moving in the opposite direction until it exits the other side of the screen.
A negative-speed pulse of light acts much the same way. 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. To use the TV analogy again—it's as if you walked by the shop window, saw your image stepping toward you from the opposite edge of the TV screen, and that TV image of you created a clone at that far edge, walking in the same direction as you, several paces ahead.
Full story here: www.scienceblog.com/cms/lights-most-exotic-trick-yet-so-fast-it-goes-backwards-10590.html
I'm sure something faster than light will soon be discovered.