Faster than light?
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It was supposed to be the one speed limit you cannot break.
But scientists claim to have demonstrated there is the possibility of travel faster than the speed of light.
The feat contradicts one of the key tenets of Einstein's special theory of relativity - that nothing, under any circumstances, can move faster than 186,000 miles per second, or the speed of light.
Travelling faster than light also, in theory, turns back time. According to conventional physics, an astronaut moving beyond light speed would arrive at his destination before leaving.
But two German physicists claim to have forced light to overcome its own speed limit using the strange phenomenon of quantum tunnelling, in which particles summon up the energy to cross an apparently uncrossable barrier.
Their experiments focused on the travel of microwave photons - energetic packets of light - through two prisms.
When the prisms were moved apart, most photons reflected off the first prism they encountered and were picked up by a detector.
But a few appeared to "tunnel" through a gap separating them as if the prisms were still held together.
Although these photons had travelled a longer distance, they arrived at their detector at the same time as the reflected photons. This suggests that the transit between the two prisms was faster than the speed of light.
Dr Gunter Nimtz, of the University of Koblenz, told the magazine New Scientist: "For the time being, this is the only violation of special relativity that I know of."
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I saw this today, very cool!
We will see if they can back up their claim with real evidence, I hope it is not another 'cold fusion' incedent.
Latest "faster than the speed of light" claims wrong (again)
By Chris Lee | Published: August 16, 2007 - 07:38PM CT
A paper submitted to the physics arXiv has been picked up by a number of major news outlets (e.g., the Daily Mail) because the paper suggests that its authors have measured something traveling faster than the speed of light. Unfortunately, the claim is worse than weak; it is silly. I'll talk about why that is after briefly discussing their research.
The paper in question has no data at all so; although it asserts that it has measured superluminal velocities, it offers nothing to back that up. It also has very little in the way of experimental detail, so we can't determine with certainty what they are measuring, making it very difficult to evaluate their claims. We'll take as close a look as we can, given these limitations.
The researchers make use of the property called total internal reflection (brief discussion). When light is above a certain angle of incidence on an interface between two materials—say, at the face of a prism—it can be totally reflected, provided it is arriving at this interface from the higher refractive index material. However, near the boundary, something called an evanescent wave forms that does not propagate like normal light (technically it does not propagate at all) and quickly decays away to nothing. If you take a second prism and place it very close to the interface where total internal reflection occurred, then some light from this evanescent wave will leak across the interface and exit the second prism. The prisms have to be no further than the wavelength of light involved for this to work.
Now the interesting questions are: where did the energy in this light come from? How fast did it travel across the boundary? The first question is interesting because the evanescent field has no energy in it. This is because the electric and magnetic fields that make up the field are phased in such a way that the product is always zero. The second question is interesting because the speed of light is not defined in a way that is intuitive to non-physicists. Suffice it to say that, for the evanescent wave, the speed of light is zero, and therefore any measurable speed is faster than the speed of light.
So, how are these authors measuring an excessive speed of light? In practical terms, most experiments measure light in terms of what is called the group velocity, which is how fast a pulse propagates along an underlying carrier frequency. This can, in some circumstances, lead to the pulses traveling faster than the speed of light in the medium they're in, but not faster than light in vacuum. Although the setup in the new paper is not entirely clear, they were measuring the arrival time of pulses, which means we're talking about group velocity rather than the actual speed of light.
Another problem that occurs in these experiments comes from determining when the pulse actually arrived. If you analyze a pulse of light, you find that it is made up of a huge number of frequencies that, as you move away from the fundamental frequency, get lower and lower in amplitude. Once you look at the experimental set up in detail, you find that it is triggering on the pre-pulse noise generated by these high frequency components.
Separate from the whole speed of light issue, the answer to the energy question in this experimental setup is interesting. Once the two prisms are close to each other, the evanescent wave is partially reflected from the second prism back to the first prism. When this happens, the total electric field and total magnetic field are no longer such that their product is always zero—there is energy in the field. Furthermore, if you analyze the components of the fields that contain the energy, you find that they do have a non-zero speed of light and it is—you guessed it—the same c that applies everywhere else in the universe.
So although this makes for an interesting physics lecture—or at least I thought it was interesting—it is not new physics and not a breakdown of special relativity.
I hope that when the world comes to an end I can breathe a sigh of relief, because there will be so much to look forward to.
Well this will be an example of science's strength over religion.
Someone has come up with 'evidence' that breaks all known laws of science. Is it true?, did it happen I for one have no idea? but what I do know is it will be peer reviewed and judged. Current theory may collapse or it may not but it will be done on the basis of evidence and scientific method
thanks xamination for saving me the time..... Speed of light, it's not just a good idea, it's the law.
"Hitler burned people like Anne Frank, for that we call him evil.
"God" burns Anne Frank eternally. For that, theists call him 'good.'