Last year, MIT physicist Frank Wilczek had a crazy idea. The Nobel Prize-winning (2004) professor has had crazy—almost impossible—ideas before, but this one fundamentally challenged one of the hard and fast rules of physics: perpetual motion is not allowed.
What he developed was a proof for “time crystals.” Now my notion of the structures is hazy, but here’s how they work in concept: they are objects that move in a repeating pattern, around and around, without expending energy or stopping. And, the kicker, “time crystals” manage to do this by breaking the symmetry of time, and in essence, allowing for a type of perpetual motion.
You see, crystals are a bit funny. When they form, their atoms organize into rows, columns, and stacks. Crystals, then, form an exception to the typical spatial symmetry of nature in that they ignore a plethora of choices for a discrete configuration. Wilczek is hoping that, when tested, crystals might also prove to break the temporal symmetry of nature, challenging the idea that objects not in motion would stay the same as time passes.
Natalie Wolchover at Wired has more:
Wilczek mulled over the possibility for months. Eventually, his equations indicated that atoms could indeed form a regularly repeating lattice in time, returning to their initial arrangement only after discrete (rather than continuous) intervals, thereby breaking time symmetry. Without consuming or producing energy, time crystals would be stable, in what physicists call their “ground state,” despite cyclical variations in structure that scientists say can be interpreted as perpetual motion.
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. But Wilczek’s papers on quantum and classical time crystals (the latter co-authored by Alfred Shapere of the University of Kentucky) survived a panel of expert reviewers and were published in Physical Review Letters in October 2012. Wilczek didn’t claim to know whether objects that break the symmetry of time exist in nature, but he wanted experimentalists to try to make one.
The theory is not without its critics—some point out the Wilczek may have been confusing the behavior of crystals in excited states with their ground states. But that hasn’t stopped a group of scientists (an international team led by Berkeley nanoengineers) from prepping a test, though this test has no planned completion date.
So here, in laymen’s terms, is how the experiment will proceed. First, the Berkeley team will build a time crystal by concentrating calcium ions into a chamber surrounded by electrodes. Diode lasers (thanks to a new scientific breakthrough) will be used to scatter excess kinetic energy, leading the calcium ions to crystallize into their ground state. From there, a magnetic field will be turned on, causing the crystallize structure to rotate.
Back to Wolchover for a wrap-up:
If all goes as planned, the ions will cycle around to their starting point at fixed intervals, forming a regularly repeating lattice in time that breaks temporal symmetry.
To see the ring’s rotation, the scientists will zap one of the ions with a laser, effectively tagging it by putting it into a different electronic state than the other 99 ions. It will stay bright (and reveal its new location) when the others are darkened by a second laser.
If the bright ion is circling the ring at a steady rate, then the scientists will have demonstrated, for the first time, that the translational symmetry of time can be broken.
Whether successful or not (or even attempted), the theorization of “time crystals” should keep physicists pondering the fabric of time and space.