Slashdot Mirror
Physicists Attempting To Test 'Time Crystals'
ceview writes "This story at Wired seems to have lots of people a bit confused: '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. ... [A] Berkeley-led team will attempt to build a time crystal by injecting 100 calcium ions into a small chamber surrounded by electrodes. The electric field generated by the electrodes will corral the ions in a "trap" 100 microns wide, or roughly the width of a human hair. The scientists must precisely calibrate the electrodes to smooth out the field. Because like charges repel, the ions will space themselves evenly around the outer edge of the trap, forming a crystalline ring.' The experimental set up is incredibly delicate (Bose Einstein Condensate), so it implies this perpetual motion effect can't really be used to extract energy. What is your take on it? It's unlike to upend anything, as the article suggests, because at a quantum level things behave weirdly at the best of times. The heavy details are available at the arXiv."
How the heck is it that Satyendar Nath Bose didn't get a Nobel prize?
I guess back then they didn't know how awesome his ideas were?
From the article: "How can something move, and keep moving forever, without expending energy? It seemed an absurd idea — a major break from the accepted laws of physics. "
Isn't that what Newton's first law of motion says? Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. Clearly the article isn't explaining this properly.
It always saddens me when scientists are afraid of looking like fools. Fortunately this one over came his fear.
Well, after we produce 6 time crystals we can assemble the key to time. Frank Wilczek is really the Black Guardian in disguise, but the Berkeley physicist heading up the project won't figure this out until the last Slashdot article in the series.
Required reading for internet skeptics
IINAScientist but here's how I understand it. Three-dimensional crystals form a regular, repeating lattice in the three spacial dimensions. These lattices are stable and need no energy input to retain their structure. Hypothetically, time crystals extend that lattice into a fourth dimension (time), treating time more-or-less as a spacial dimension. Given that the structure is crystalline, no energy is needed to maintain it even though its 3-dimensional structure, dimensions, etc. may appear to vary over time. Such structures are so far only hypothetical; the goal of this experiment is to attempt to create one.
Accept Eris as your Fnord and personally sate her
Here's my understanding (I'm a physicist though not in a field at all related to the described work):
As usual, the summary and the article somewhat mis-state the interesting part. They talk about 'perpetual motion' but there are lots of examples of things that move seemingly without end: e.g. a planet orbiting a star. However if you think about it a bit more, you'll realize that those kinds of motion can't be used to get "free energy" and actually are not even perpetual. If you try to extract energy from some kind of bound system that exhibits motion, you decrease the energy of the system and alter the motion. So you can extract energy from a planetary orbit (in principle), but then the planet will have less energy, and orbit more slowly (its orbit will decay). As other posters mention, all kinds of natural processes inherently perform this kind of "energy extraction": e.g. random collisision with space-dust, or tidal interactions between planetary bodies, will slowly alter these 'perpetual' orbits. Even if you imagine a highly idealized system (perfectly rigid objects orbiting one another in perfect vacuum), we have reason to believe that such a system will radiate away energy (slowly) by emitting gravitational waves.
What this all amounts to is saying that the system has some 'extra energy' that could be extracted. In physics we would say that the system is not in its ground state, or "minimum energy state". This is the key phrase that the quoted physicists use which the article doesn't properly explain.
The idea is that a system in its ground state will have lost all the energy it can possibly lose. There is no extra energy left. And, conventionally one would assume that a system in the ground state would no longer exhibit any kind of motion: because any motion is extra energy that could be extracted, obviously. So an idealized orbital system has motion, but is not in the minimum energy state. What Wilczek is proposing is that he's discovered kinds of systems which exhibit motion in their ground state. In other words, the system oscillates as a function of time, and yet one cannot extract energy from this oscillation. Cool!
The analogy to crystals is this: as you cool atoms, they vibrate less and less, and eventually they settle into their minimum energy state. This state is usually a crystal, where all the atoms are frozen into perfect rows. This is the minimum energy state. Interestingly, at high-temperature the system was spatially homogeneous (a gas has atoms all over the place), whereas the ground state has spontaneously broken space-translational symmetry: the atoms exist in well-defined positions and don't occupy intervening points. Thus the ground state spontaneously breaks a symmetry (space-translation). Wilczek's proposed states, if they really exist, would upon cooling to their ground state (no excess energy left) settle into an arrangement where they are in motion. Thus along the time axis the system is not constant/homogeneous. The system has spontaneously broken time-translational symmetry. Hence this is like a crystal along the time axis: a 'time crystal'.
I'm not qualified to say whether this is right or wrong. It would be exciting if true. But it doesn't seem to violate any known laws (e.g. you can't use it to violate conservation of energy, so no 'perpetual motion' in the 'free energy' sense), so it seems possible that these states could exist.