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Perpetual Motion Test Could Amend Theory of Time

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Sketch of ion ring. An illustration of the time crystal experiment planned at UC-Berkeley. Electric fields will be used to corral calcium ions into a 100-micron-wide “trap,” where they will form a crystalline ring. The scientists believe a static magnetic field will cause the ring to rotate. (Illustration: Courtesy of Hartmut Häffner)

Sketch of ion ring.
An illustration of the time crystal experiment planned at UC-Berkeley. Electric fields will be used to corral calcium ions into a 100-micron-wide “trap,” where they will form a crystalline ring. The scientists believe a static magnetic field will cause the ring to rotate. (Illustration: Courtesy of Hartmut Häffner)

by: Natalie Wolchover
In February 2012, the Nobel Prize-winning physicist Frank Wilczek decided to go public with a strange and, he worried, somewhat embarrassing idea. Impossible as it seemed, Wilczek had developed an apparent proof of “time crystals” — physical structures that move in a repeating pattern, like minute hands rounding clocks, without expending energy or ever winding down. Unlike clocks or any other known objects, time crystals derive their movement not from stored energy but from a break in the symmetry of time, enabling a special form of perpetual motion.

“Most research in physics is continuations of things that have gone before,” said Wilczek, a professor at the Massachusetts Institute of Technology. This, he said, was “kind of outside the box.”

Wilczek’s idea met with a muted response from physicists. Here was a brilliant professor known for developing exotic theories that later entered the mainstream, including the existence of particles called axions and anyons, and discovering a property of nuclear forces known as asymptotic freedom (for which he shared the Nobel Prize in physics in 2004). But perpetual motion, deemed impossible by the fundamental laws of physics, was hard to swallow. Did the work constitute a major breakthrough or faulty logic? Jakub Zakrzewski, a professor of physics and head of atomic optics at Jagiellonian University in Poland who wrote a perspective on the research that accompanied Wilczek’s publication, says: “I simply don’t know.”

Now, a technological advance has made it possible for physicists to test the idea. They plan to build a time crystal, not in the hope that this perpetuum mobile will generate an endless supply of energy (as inventors have striven in vain to do for more than a thousand years) but that it will yield a better theory of time itself….
Read more at https://simonsfoundation.org/features/science-news/perpetual-motion-test-could-amend-theory-of-time/

Written by physicsgg

April 27, 2013 at 6:33 am

Posted in PHYSICS

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Self-oscillation

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Alejandro Jenkins

Illustration of the turbulent vortices generated by a flow of velocity v as it hits a circular obstacle of diameter d, on the left

Physicists are very familiar with forced and parametric resonance, but usually not with self-oscillation, a property of certain linear systems that gives rise to a great variety of vibrations, both useful and destructive. In a self-oscillator, the driving force is controlled by the oscillation itself so that it acts in phase with the velocity, causing a negative damping that feeds energy from the environment into the vibration: no external rate needs to be tuned to the resonant frequency. A paper from 1830 by G. B. Airy gives us the opening to introduce self-oscillation as a sort of “perpetual motion” responsible for the human voice. The famous collapse of the Tacoma Narrows bridge in 1940, often attributed by introductory physics texts to forced resonance, was actually a self-oscillation, as was the more recent swaying of the London Millenium Footbridge. Clocks are self-oscillators, as are bowed and wind musical instruments, and the heartbeat. We review the criterion that determines whether an arbitrary linear system can self-oscillate and describe the operation of two thermodynamic self-oscillators, the putt-putt toy boat and the Rijke tube, before concluding with a brief discussion of the relevance of the concept of self-oscillation to the semi-classical theory of lasers….
Read more: http://arxiv.org/PS_cache/arxiv/pdf/1109/1109.6640v1.pdf

Written by physicsgg

October 13, 2011 at 5:45 pm