The reason I pose this question with the answer below is: Science has used the constant speed of light to determine, distance, time, speed, and the age of the universe. Being able to alter, what was once considered a constant, makes new problems with no answers. Only new doors open for new possibilities. Even one that science would not like to admit. That some things may not be as old as first thought. So read below, all of what you see is from science itself. I have included the references that go exactly to where this info was reprinted from.
Light feels the heat and slows down
1 July 1999
Earlier this year a group of physicists reduced the velocity of a laser pulse to 17 metres per second. However, the group had to use a Bose condensate - a gas of atoms cooled to a temperature of less than one micro-kelvin - to achieve this incredible reduction in velocity. Now another group of researchers has slowed light down to 90 metres per second in a gas of hot rubidium atoms. The new technique will be much easier to use for applications. The team, which was led by Edward Fry and Marlan Scully of Texas A&M University and the Max Planck Institute for Quantum Optics in Germany, exploited a phenomenon known as electromagnetically induced transparency (Phys. Rev. Lett. 82 5229).
The researchers also showed that the rubidium gas, which they say is a "relatively easily created medium", exhibits extremely efficient nonlinear interactions. Materials with such properties could be used for fundamental research, such as high-precision spectroscopy, or for applications such as the compression of optical information.
In electromagnetically induced transparency a "pump" laser is used to drive transitions between various electron energy levels in the atom. If the conditions are correct, quantum interference effects can cause the probability of transitions between two of the levels to fall to zero. This means that a second "probe" laser with a frequency that is resonant with this transition can travel through the media without absorption. The quantum interference can also increase the refractive index of the material at this frequency by many orders of magnitude, thereby greatly reducing the speed of light in the material.
Reference: Physics Web
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Desktop kit slows light to a crawl |
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| 11:09 02 April 03 |
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| NewScientist.com news service |
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Light can been slowed down to just over 200 kilometres per hour using only simple desktop equipment at room temperature, US researchers have shown.
In a vacuum, light travels at 300,000 kilometres per second. It is slowed, for example, by a third when it passes through glass. But slowing light to 200 kph - a factor of 5.4 million - normally requires large and complex laboratory equipment and cryogenic cooling.
Light can even be stopped by causing it to interact with atoms of gas tuned with laser beams. These laboratory techniques use an effect called electromagnetically induced transparency (EIT) to alter the speed at which light travels through a material.
"We used a different physical process," says Robert Boyd, at the University of Rochester in New York. This allowed the team to slow light dramatically with apparatus up no bigger than a desktop PC.
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Rhythmic vibration
The researchers fired two laser beams tuned to slightly different frequencies at a ruby crystal. The frequency difference produced a rhythmic vibration in atoms in the crystal, which in turn altered the refractive index of the material.
The effect, called coherent population oscillation, is well known but has never been put to this use before. The refractive index determines the speed of light and can be tuned by changing the frequency of the lasers. Boyd says the work could have important implications for telecommunications research. It could make it easier to control information transmitted via light at a network switching station, for example.
"We can control the delay that light experiences when it passes through the material," Boyd told New Scientist. "It's a mundane application, but it is very important." Journal reference: Physical Review Letters (DOI: 10.1103-1/PhysRevLett.90.113903) |
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Will Knight
Reference: New Science
An opinion: If gravity can affect something, that has no mass, by attracting it, or pulling on it. Then how do we know that the light that leaves an object (like our sun) is at full velocity? Does light have to travel a certain distance from this gravity before it can obtain the speed of light?
Why would not the same gravity that bends light not also try to pull it backwards as it leaves the sun? Which would slow it down. Can gravity only pull light in one direction? That's what I was made to believe when I ask this question on a science forum. They would not admit it, but it was implied.
The reasoning: If science has to recant the theory that: "light speed in a vacuum is constant". Think of all the formulations that would have to be redone. Everything that distance has been measured by light speed, being a constant, would have to be redone. The age of the universe would no longer be right. Even the distance of the sun from earth would be wrong. Etc.. etc... The things that science will not approach just keeps stacking up. One day, it will become as big as a mountain, and when it falls, all involved will be crushed. And there will be to many peaces to pick up and try to start over. | |
Can light be stopped?
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Light 'frozen' in its tracks |
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| 18:00 10 December 03 |
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| NewScientist.com news service |
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A pulse of light has been stopped in its tracks with all its photons intact, reveal US physicists.
In a vacuum, light travels at the phenomenal speed of approximately 300,000,000 metres per second. Scientists can exploit the way that the electric and magnetic fields in light interact with matter to slow it down.
Over the last few years, scientists have become masters of the light beam. Speeds of a few metres per second are now reached routinely in laboratories around the world. It is rather harder, however, to stop light completely and previous attempts have halted light but lost its photons in the process.
Mikhail Lukin and colleagues at Harvard University in Cambridge, Massachusetts managed to stop light without this loss by firing a short burst of red laser light into a gas of hot rubidium atoms.
This is then "frozen" with the help of two control beams. The light in the control beams interacts with the rubidium atoms to create layers that alternately transmit and reflect the pulse.
As the signal tries to propagate through these layers, the photons bounce backwards and forwards between them. As a result, the pulse makes no forward progress - the light is "frozen" in place. The pulse is set free when the control beams are turned off.
Ulf Leonhardt at the University of St Andrews in Fife, Scotland, says the technique is novel in that the effect the control beams have is "like storing light behind bars".
Reference: New Science
There are also some more interesting articles about light at this website. Liquid Light Stop light technology for quantum computing. The ultimate control over light.
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