A group of American physicists were able to construct the so-called "crystal of time" - a structure, the possibility of which was predicted long ago. A feature of the crystal is the ability to periodically become asymmetric not only in space, but also in time. Therefore, it can be used to make an ultra-precise chronometer.
Crystals are generally very paradoxical formations. Take, for example, their relationship with symmetry: as we know, a crystal itself, judging by its appearance, can be considered simply a model of spatial symmetry. However, the crystallization process is nothing more than its malicious violation.
This is very well illustrated by the example of the formation of crystals in solution, for example, some salts. If we analyze this process from the very beginning, it will be seen that in the solution itself the particles are arranged chaotically, and the entire system is at a minimum energy level. However, interactions between particles are symmetric with respect to rotations and shears. However, after the liquid has crystallized, a state arises in which both of these symmetries are broken.
Thus, we can conclude that the interaction between particles in the resulting crystal is not at all symmetric. This implies a number of the most important properties of crystals - for example, these structures, unlike liquid or gas, conduct electric current or heat in different ways in different directions (they can conduct it to the north, but not to the south). In physics, this property is called anisotropy. This crystalline anisotropy has long been used by humans in various industries, such as electronics.
Another interesting property of crystals is that, as a system, it is always at the minimum energy level. What is most curious is that it is much lower than, for example, in the solution that "gave birth" to the crystal. It can be said that in order to obtain these structures, it is necessary to "take away" energy from the initial substrate.
So, during the formation of a crystal, the energy level of the system decreases and the initial spatial symmetry is broken. And not so long ago, two physicists from the United States, Al Shapir and Frank Wilczek (by the way, a Nobel laureate), wondered whether the existence of a so-called "four-dimensional" crystal, where symmetry breaking would occur not only in space, but also in time, was possible.
With the help of complex mathematical calculations, scientists were able to prove that this is quite possible. The result is a system that exists, like a real crystal, at a minimum energy level. But the most interesting thing is that due to the formation of certain periodic structures, not in space, but in time, it would come to an asymmetric final state. The authors of the work called such a system very solemnly - "the crystal of time".
After a while, a group of experimental physicists led by Professor Zhang Xiang from the University of California (USA) decided to create such a system no longer on paper, but in reality. Scientists have created a cloud of beryllium ions, and then "locked" it in a circular electromagnetic field. Since the electrostatic repulsion of equally charged ions from each other causes them to be distributed evenly around the circle, the researchers essentially got a gaseous crystal. And while the characteristics of the field were unchanged, the state of the system, in theory, should not have changed either.
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At the same time, calculations, and then observations, showed that this very ionic ring will not be motionless. The gaseous crystal was constantly rotating, and the interactions of the ions were sometimes symmetric, then not. All this was observed even when the crystal was cooled to almost absolute zero. Thus, this structure is indeed a "crystal of time": it exhibits the properties of periodicity and asymmetry both in space and in time.
It is curious that the leisurely rotating ring of ions, designed by Professor Zhang's group, caused many non-specialists to associate it with a perpetual motion machine. Of course, a gas crystal looks like a perpetum mobile, but in fact it is not. After all, this system cannot do any work, since all its components are at the same energy level (moreover, the minimum). And according to the second law of thermodynamics, work is possible only in that system, the components of which are at least at two energy levels.
At the same time, this does not mean at all that the "time crystal" cannot be used in any way for practical needs. Professor Zhang is convinced that, for example, an ultra-precise chronometer can be constructed on its basis. After all, the transition from symmetry to asymmetry has a pronounced periodicity. In the meantime, the professor and his colleagues want to do a more detailed study of the properties of the wonderful structure they created …
Anton Evseev
