Light Coaxed Out of Nowhere in Vacuum -- Maybe!
Physicists have coaxed energy from a vacuum. Though not yet verified, this finding would provide an unusual proof for quantum mechanics. John Pendry, a theoretical physicist at Imperial College in London who was not involved in the study, calls it "a significant milestone."
The work was done at Chalmers University of Technology in Gothenburg, Sweden. The researchers will present their findings in Padua, Italy, next week. They have post4ed a paper on a server, but they have not talked to reporters since the work has not yet been peer-reviewed. In spite of this, other scientists are impressed by the study. At the heart of the experiment is the quantum principle that empty space contains many particles that twinkle in and out of existence. An example consists of photons between mirrors. More of these short term photons exist in space than between two facing mirrors, which pushes the mirrors together. This "Casimir" force is strong enough when the mirrors are close for it to be measured.
Theorists have predicted for decades that such an effect can be produced by a single mirror if it is moving very quickly. Theoretically a mirror can absorb energy from a virtual photon and re-emit it as a real photon. A mirror has to be moving through a vacuum at nearly the speed of light for this effect, a situation nearly impossible for ordinary devices.
The researchers at Chalmers avoided this limit by using a superconducting quantum interference device (SQUID), itself very sensitive to magnetic fields.
By constructing a superconducting circuit for which the SQUID served as a mirror and passing a magnetic field through the SQUID with reversal of current several billion times a second, the "wiggle" of the mirror was enough to create a noticeable effect.
The group claims the result was a shower of microwave photons shaken loose from the vacuum. The frequency of these photons was roughly half the frequency for which the mirror was wiggling, which fits quantum theory.
Frederico Capasso, himself an experimental physicist at Harvard University, has worked on quantum effects. He calls the experiment "very clever" but not practical, since large numbers of photons are not generated. He would like to see a moving piece of metal generating detectable light from the vacuum, but currently available speeds aren’t fast enough.
-- summarized by the blog author from a June 3, 2001, article by Geoff Brumfiel of Nature magazine that was repeated by Scientific American online at:
http://www.scientificamerican.com/article.cfm?id=moving-mirrors-make-light-from-nothing
Here is a comment posted by a reader of that Scientific American online site:
In contrast to the weird 'something from nothing' effect implied in this article, the manifestation of 'virtual' (short lived, self-annihilating particle-antiparticle pairs) particles must be the product of energy interactions within spacetime.
-- Jtdwyer 4:19pm June 3, 2011
= = = = = = = = = = = = = = = = = = = = = = = = = = =
The blog author agrees with Jtdwyer’s speculation. The short-lived particles are likely to have been created by the rapidly oscillating mirror or by the electrons in the circuit exposed to high magnetism. The blog author also doubts that the vacuum of space is teeming with short-lived particles. The light from a galaxy over 13 billion light years away is fuzzy but still forms a recognizable blob of a galaxy. Not much at all has interfered with those photons moving so fast for so long…. a vacuum really is a vacuum… so the experiment could easily be "noise" created by the circuit used to create the "mirror."
Oh. One more little thing. Quantum mechanics is a model.
Physicists have coaxed energy from a vacuum. Though not yet verified, this finding would provide an unusual proof for quantum mechanics. John Pendry, a theoretical physicist at Imperial College in London who was not involved in the study, calls it "a significant milestone."
The work was done at Chalmers University of Technology in Gothenburg, Sweden. The researchers will present their findings in Padua, Italy, next week. They have post4ed a paper on a server, but they have not talked to reporters since the work has not yet been peer-reviewed. In spite of this, other scientists are impressed by the study. At the heart of the experiment is the quantum principle that empty space contains many particles that twinkle in and out of existence. An example consists of photons between mirrors. More of these short term photons exist in space than between two facing mirrors, which pushes the mirrors together. This "Casimir" force is strong enough when the mirrors are close for it to be measured.
Theorists have predicted for decades that such an effect can be produced by a single mirror if it is moving very quickly. Theoretically a mirror can absorb energy from a virtual photon and re-emit it as a real photon. A mirror has to be moving through a vacuum at nearly the speed of light for this effect, a situation nearly impossible for ordinary devices.
The researchers at Chalmers avoided this limit by using a superconducting quantum interference device (SQUID), itself very sensitive to magnetic fields.
By constructing a superconducting circuit for which the SQUID served as a mirror and passing a magnetic field through the SQUID with reversal of current several billion times a second, the "wiggle" of the mirror was enough to create a noticeable effect.
The group claims the result was a shower of microwave photons shaken loose from the vacuum. The frequency of these photons was roughly half the frequency for which the mirror was wiggling, which fits quantum theory.
Frederico Capasso, himself an experimental physicist at Harvard University, has worked on quantum effects. He calls the experiment "very clever" but not practical, since large numbers of photons are not generated. He would like to see a moving piece of metal generating detectable light from the vacuum, but currently available speeds aren’t fast enough.
-- summarized by the blog author from a June 3, 2001, article by Geoff Brumfiel of Nature magazine that was repeated by Scientific American online at:
http://www.scientificamerican.com/article.cfm?id=moving-mirrors-make-light-from-nothing
Here is a comment posted by a reader of that Scientific American online site:
In contrast to the weird 'something from nothing' effect implied in this article, the manifestation of 'virtual' (short lived, self-annihilating particle-antiparticle pairs) particles must be the product of energy interactions within spacetime.
-- Jtdwyer 4:19pm June 3, 2011
= = = = = = = = = = = = = = = = = = = = = = = = = = =
The blog author agrees with Jtdwyer’s speculation. The short-lived particles are likely to have been created by the rapidly oscillating mirror or by the electrons in the circuit exposed to high magnetism. The blog author also doubts that the vacuum of space is teeming with short-lived particles. The light from a galaxy over 13 billion light years away is fuzzy but still forms a recognizable blob of a galaxy. Not much at all has interfered with those photons moving so fast for so long…. a vacuum really is a vacuum… so the experiment could easily be "noise" created by the circuit used to create the "mirror."
Oh. One more little thing. Quantum mechanics is a model.
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