Time crystals could behave almost like perpetual motion machines
February 20, 2012 by Lisa Zyga 
Image by Sam Rohn, flickr.com/photos/nylocations/
(PhysOrg.com) -- As every young science student knows, moving objects have kinetic energy. But just how much energy does something need to move? In a new study, a pair of physicists has shown that it’s theoretically possible for a system in its lowest energy state, or ground state, to exhibit periodic motion. This periodically moving system can be thought of as the temporal equivalent of a crystal, which is defined by its spatial periodicity. What’s even more intriguing about these "time crystals" is that, by exhibiting motion at their state of lowest energy, they break a fundamental symmetry called time translation symmetry and become "perilously close" to looking like perpetual motion machines.
The physicists, Frank Wilczek of MIT (a 2004 Nobel Laureate) and Alfred Shapere of the University of Kentucky, have posted two papers on their novel idea of time crystals at arXiv.org. One paper focuses on classical time crystals, while the other looks at quantum time crystals.
Modern physics deals with many types of symmetry, but one of the most fundamental is time translation symmetry, which basically says that the laws of physics we have today should still be here tomorrow. Likewise, if a system’s features remain constant over time, that system obeys time translation symmetry. On the other hand, a clock, which has hands that are constantly moving, breaks time translation symmetry.
But while a clock requires a power source to break this symmetry, a system in its lowest energy state has no power source by definition. To show that such a system can indeed exhibit motion, Wilczek and Shapere performed some complex mathematical calculations, which revealed that a system in its lowest energy state could move in a periodic motion, such as a loop or orbit. As far as the scientists know, this is the first time that a system in its lowest energy state without any external source of power has been shown to exhibit motion and break time translation symmetry.
As the physicists explained, this discovery doesn’t mean that such systems actually exist in nature, but that they can exist. At first, the physicists were somewhat doubtful that they could exist at all, since such a system would behave very similar to a perpetual motion machine, the fantasy device that could run forever with no energy input. However, building such a system may actually be less improbable than showing that it can simply exist. As the scientists noted, under the right circumstances, a superconductor almost acts in this manner because ground-state electrons can continuously loop through it.
“It’s so tricky to implement mathematically,” Wilczek told PhysOrg.com. “It’s surprising that they can exist at all. But, whether or not they exist naturally, I’m very optimistic that it’s something one could engineer.”
He added that, even though time crystals might move continuously, they couldn’t be used to generate useful energy since they can’t be disturbed, and they wouldn’t violate the second law of thermodynamics. Nevertheless, the possibilities for time crystals are exciting, and the scientists plan to investigate them further in the future.
“There are many directions to go here,” Wilczek said. “The question is what to do first. ... One question is how this kind of idea might be realized in actual materials. What are the materials, how can we tell that it’s happening, what dimensions do the materials have? If this is a state of matter that’s different from other states, there could be phase transitions.”
“In the past, I’ve had some exciting episodes,” he said, referring to his earlier work on anyons, particles with such unusual properties that some people doubted they could exist. Evidence for anyons was finally detected in 2005. “It’s a strange, curious idea, and it will be interesting to see where it goes.”
More information: Alfred Shapere and Frank Wilczek. “Classical Time Crystals.” arXiv:1202.2537v1 [cond-mat.other]
Frank Wilczek. “Quantum Time Crystals.” arXiv:1202.2539v1 [quant-ph]
via: Science News
© 2011 PhysOrg.com
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Feb 20, 2012
Rank: 1.7 / 5 (13)
How about the electron in a hydrogen atom?
Planets orbiting a star?
Feb 20, 2012
Rank: 2.5 / 5 (11)
Exactly what I thought of.
However, on closer inspection, those systems are imperfect and deteriorate over time due to various forces such as friction, frame dragging, etc.
but from my point of view, for all practical purposes, you are correct, those systems are and have always been perpetual motion machines.
Feb 20, 2012
Rank: 2.2 / 5 (9)
"Persistent current is a perpetual electrical current, not requiring an external power source, that flows naturally through resistive metal."
http://en.wikiped..._current
Which is as usual egocentrically myopic in the extreme. Planetary orbits decay from tidal forces. Electron orbits do not decay. Unless you have a source which says they do?
Feb 20, 2012
Rank: 4.5 / 5 (10)
Feb 20, 2012
Rank: 3 / 5 (9)
Allegedly, over obscenely long time periods they certainly decay, according to the mainstream model, because that ties into part of the "big freeze" theory of cosmology. All matter and energy eventually decay.
this is what all the big names in modern physics say anyway.
youtube.com/watch?v=zf2csQnE0jA
I tire of these games, Ghost.
I wonder whether you even bother to check this stuff for yourself, or if you've come to hypocritically rely on my integrity.
Feb 20, 2012
Rank: 2.4 / 5 (5)
Feb 20, 2012
Rank: 1.6 / 5 (9)
The requirement of these "time crystals" is that they be isolated from their surroundings, such that their quantum state is not altered.
Applying the same limitations on atoms or planets produces the same perpetual motion results.
Feb 20, 2012
Rank: 1 / 5 (8)
Given that individual particles are themselves characterized by temporal oscillations, I see nothing special here.
Feb 20, 2012
Rank: 5 / 5 (10)
They decay - but there's no friction, frame dragging or whatnot involved (and the orbitals don't shrink, either). Proton decay - if it exists - is a probabilistic process (i.e. it happens suddenly, but with a very low probability)
And no - this has nothing to do with the 'big freeze'. The big freeze can very well happen with atoms still in it. Atoms can be at 0 Kelvin and still remain atoms.
Feb 20, 2012
Rank: 5 / 5 (2)
Feb 20, 2012
Rank: 1.7 / 5 (7)
Please fire whoever writes your BS headlines. Immediately.
Sensationalistic headline deceit is for politics, not physics.
Feb 20, 2012
Rank: 1 / 5 (7)
Feb 20, 2012
Rank: not rated yet
Feb 20, 2012
Rank: 3 / 5 (4)
Watch it again, you missed it.
Clearly, if the theory claims the entire universe will be made of nothing but photons, then all physical matter, including electrons, must decay.
Feb 20, 2012
Rank: 4.6 / 5 (10)
I didn't mean that the orbitals get smaller or somesuch (they are quantized). I meant that protons possibly decay. If they do then the atoms they were a part of will eventually decay (i.e. fall apart). This is a sudden event...not some slow 'spiralling in' of electrons (which is a wrong picture, anyways, because electrons do not orbit nuclei the way moons orbit planets)
Feb 20, 2012
Rank: 5 / 5 (1)
Feb 20, 2012
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Could we eventually harness the power of their kinetic energy?
Feb 20, 2012
Rank: 5 / 5 (11)
So the answer would be: No.
Feb 20, 2012
Rank: 2 / 5 (4)
Maybe so, but we'll never know as absolute zero temperature is unachievable.
Feb 20, 2012
Rank: 5 / 5 (2)
I'm sorry, what ?
http://en.wikiped...-PAR.svg
You are looking for a slow spiral or something Newtonian ?
Feb 20, 2012
Rank: 1 / 5 (2)
Quick question: The 2nd law depends on closed systems. Do closed systems really translate from math to modern physics where a particle is always unavoidably exposed to vacuum energy and quantum foam?
Feb 21, 2012
Rank: 1 / 5 (2)
Forgivable, perhaps. We don't know how much sleep the writer was missing. But don't do it again.
Feb 21, 2012
Rank: 5 / 5 (1)
Regarding the electron around a atom core. Bohr suggested a planetary system to describe this. Due to the speed electrons would immediatly throw themselves into the atom core because of the centrigual force (I might state it politically incorect, therefore my apologies).
Clearly, this doesn't happen. Why? Because newtonian physics do not apply anymore and we need to use quantum physics. The electron is equally distributed at a certain distant (1s orbital) and if it a probability distribution, meaning it is likely to find the electron somewhere over there, but it can't be exactly pinpointed.
That is why the atom-system is not a perpetuum mobile system =perpetual motion machine in newtion physics
Feb 21, 2012
Rank: 2 / 5 (4)
It was a minor point of contention. But even the intended meaning of the article is not news.
Feb 21, 2012
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Feb 21, 2012
Rank: 3 / 5 (2)
How about this-
http://en.wikiped...ysics%29
"dark current is the relatively small electric current that flows through photosensitive devices such as a photomultiplier tube, photodiode, or charge-coupled device even when no photons are entering the device ... dark current flows due to the random generation of electrons and holes within the depletion region of the device that are then swept by the high electric field"
Feb 21, 2012
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Feb 21, 2012
Rank: 3.8 / 5 (4)
Feb 21, 2012
Rank: 1 / 5 (2)
Please provide evidence for the decay of electron orbits or STFU.
Feb 21, 2012
Rank: 5 / 5 (1)
Actually it can. It's a mathematical concept, and thus not dependent in any way on human thinking.
Feb 22, 2012
Rank: 1 / 5 (1)
Tricky, because from the point of view of a photon no time passes. To it the event of emission and of being captured are simultaneous (this even goes if the photon isn't captured, ever, again (!))
What about it? You have an external voltage (power source) along which the charged particles (electrons, holes) flow.
The dark current gets less the cooler you make your photomultiplier. This is why many infrared/photomultiplier detector systems are cooled (e.g. military targetting systems or infrared telescopes)
Dark current is a probabilistic occurence. A system that has a temperature above absolute zero contains some (thermal) energy. But that energy isn't (at all times) spread perfectly evenly throughout the system. If enough of it (by chance) happens to be at one point an electron can be liberated from its atom.
Feb 23, 2012
Rank: 5 / 5 (1)
http://en.wikiped..._theorem
Feb 23, 2012
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Feb 24, 2012
Rank: 1 / 5 (2)
Feb 24, 2012
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Feb 25, 2012
Rank: not rated yet
Questo materiale, sebbene perfettamente isolato dall'ambiente circostante, potrebbe essere sede di vibrazioni meccaniche perpetue.
Sarebbe questo un time cristal?
Forse cercavi: posso immaginare un materiale con una perfetta elasticitą, similmente ad un materiale con perfetta conducibilitą elettrica.
Digita il testo o l'indirizzo di un sito web oppure traduci un documento.
Annulla
ingleseitalianospagnoloAlpha
I can imagine a material with a perfect elasticity, similar to a material with perfect electrical conductivity.
This material, though perfectly isolated from the environment, could be the site of perpetual mechanical vibrations.
This would be a time crystal?
Feb 25, 2012
Rank: not rated yet
Feb 26, 2012
Rank: 1 / 5 (1)
http://arxiv.org/.../0312325
and
http://en.wikiped...operties
Feb 26, 2012
Rank: not rated yet
In basic physics, a voltage does not necessarily require a power source, however that may not be the case with how a photodiode works.
Right, the point is that this thermal energy can theoretically do some tiny amount of work through this dark current, even though it actually impedes usefulness in real thermal imaging devices.