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Are time crystals just a mathematical curiosity, or could they actually physically exist? Physicists have been debating this question since 2012, when Nobel laureate Frank Wilczek first proposed the idea of time crystals. He argued that these hypothetical objects can exhibit periodic motion, such as moving in a circular orbit, in their state of lowest energy, or their "ground state." Theoretically, objects in their ground states don't have enough energy to move at all.
In the years since, other physicists have proposed various arguments for why the physical existence of time crystals is impossible—and most physicists do seem to think that time crystals are physically impossible because of their odd properties. Even though time crystals couldn't be used to generate useful energy (since disturbing them makes them stop moving), and don't violate the second law of thermodynamics, they do violate a fundamental symmetry of the laws of physics.
However, now in a new paper published in Physical Review Letters, physicists from the University of California, Santa Barbara (UCSB) and Microsoft Station Q (a Microsoft research lab located on the UCSB campus) have demonstrated that it may be possible for time crystals to physically exist.
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According to the physicists, it should be possible to perform an experiment to observe time-translation symmetry breaking by using a large system of trapped atoms, trapped ions, or superconducting qubits to fabricate a time crystal, and then measure how these systems evolve over time. The scientists predict that the systems will exhibit the periodic, oscillating motion that is characteristic of time crystals and indicative of spontaneously broken time-translation symmetry.
(Score: 1, Interesting) by Anonymous Coward on Tuesday September 13 2016, @10:02PM
I am not a physicist, so I'm speaking purely as a layman. However, this doesn't pass the "sniff" test to me, much like perpetual motion machines.
I'm prepared to believe that such objects in perpetual motion exist. However, assuming they do and their lowest energy state is one of motion, how would a person be able to observe it? For this object to be observed, it would need to interact with the general universe in some way (emitting photons, gravity waves, transferring momentum, etc)... and that would expend energy. Assuming Newton's 3 laws of motion are true (this is a big assumption, especially at the quantum level), than that would necessarily impart energy on the thing being acted upon, which would lower the energy state of the crystal and contradict the initial assumption.
Can a physicist or mathematician cut past the jargon and say whether this has any more plausibility than the countless patents for perpetual motion machines the patent office rejects without even bothering to read them?
(Score: 2) by turgid on Tuesday September 13 2016, @10:08PM
Could you extract energy from it? If it's in "the ground state" I doubt it (it can't physically move to a lower-energy state), therefore, you can't really claim it to be perpetual motion. However, back when I made a ham-fisted attempt at trying to learn some physics, I think stuff in the ground state was always in motion. Absolute Zero is physically impossible to achieve. It's just a theoretical concept. So yes, it sounds like codswallop.
I refuse to engage in a battle of wits with an unarmed opponent [wikipedia.org].
(Score: 1, Insightful) by Anonymous Coward on Wednesday September 14 2016, @02:22AM
Perpetual motion is kinda a misnomer. A body in motion stays in motion while one at rest stays at rest (unless acted upon by an external force).
So, in a sense, the earth goes around the sun perpetually (kinda). And the moon goes around the earth perpetually. The rovers we launched in space are perpetually moving. Comets move perpetually.
When most people refer to perpetual motion what they mean is perpetual energy production. Something that can spontaneously produce (infinite sums of) energy perpetually.
(Score: 0) by Anonymous Coward on Wednesday September 14 2016, @01:23PM
By observing an observable that changes during that motion.
The interaction energy can be provided by the measurement device. Obviously the ground state won't emit energy on its own, otherwise it wouldn't be the ground state.
And yes, the measurement would take it out of the ground state. Without having read the article, I'd expect them to prepare those states many times, and then measure after a different duration for different equally-prepared systems. If they see a periodicity in their measurement data, they know they have a periodic moving state.