They sound like some fanciful fiction, the stuff of fairy tales, or some Jim Henson-inspired concoction: time crystals. But it turns out that these intuition-defying entities could actually exist, according to a new study released in the journal Physical Review Letters.
Time crystals were an idea first proposed by Nobel laureate Frank Wilczek in 2012. They began as mere mathematical curiosities, hypothetical objects that extend the idea of a crystal beyond the three dimensions of space and into the fourth dimension of time. Now new research by Wilczek answers some of the criticisms that have been leveled at his idea. More intriguingly, though, the research leaves open the possibility that time crystals could actually exist, reports Phys.org.
The main argument against the existence of time crystals relates to one of their more bizarre characteristics, which is that they seem capable of achieving everlasting movement by periodically moving and then returning to an original state over and over again. This would seem to indicate that they violate a fundamental symmetry in physics, known as "time-translation symmetry."
Time-translation symmetry is a version of one of the fundamental symmetries of space-time, which essentially states that the laws of physics are the same everywhere and at all times. Wilczek and colleagues think they can get around an underlying violation of this principle by making a crucial distinction between "explicit symmetry breaking" and "spontaneous symmetry breaking."
"If a symmetry is broken explicitly, then the laws of nature do not have the symmetry anymore; spontaneous symmetry breaking means that the laws of nature have a symmetry, but nature chooses a state that doesn't," explained co-author Dominic Else.
If time crystals merely break spontaneous symmetry, they wouldn't be the first entities known to do so in nature. For instance, symmetry is mysteriously broken in magnets, which spontaneously "choose" which pole is north and which pole is south. This doesn't break any symmetries that exist in the laws of physics themselves, it merely represents an example of the laws of physics not specifying what ought to happen.
Regular crystals actually spontaneously break symmetry too, though the symmetries they violate are all spatial in nature, not extending to the dimension of time. The spontaneous breaking of time-translation symmetry has never been observed before, but if it's ever observed, it seems like time crystals should be the place to look.
To prove that this was possible, the researchers ran simulations that allowed for the spontaneous breaking of time-translation symmetry without violating any other fundamental laws of physics, such as the laws of thermodynamics.
So time crystals ought to be able to exist in nature. They're not mathematically impossible, at least. The next step will be to try and actually create one, which Wilczek's team is already beginning to imagine. They have envisioned an experiment involving a large system of trapped atoms, trapped ions, or superconducting qubits — the equivalent of computer bits, but for a quantum computer — to fabricate a time crystal.
If they're successful, it will be a mind-blowing breakthrough, to say the least. We can only hope they don't accidentally open a door to another time dimension in the meantime, spilling out Demogorgons or some other once-fictional entities from our nightmares. That's just the risk of working on the cutting edge of theoretical physics.