Physicists have filmed the oscillation of a time crystal
Since the article doesn&#x27;t do a good job of explaining what a time crystal <i>is</i>, here&#x27;s my attempt at summarizing the Wikipedia article [0].<p>Normally, a system which is driven by an external frequency oscillates at the same, or a multiple of the driving frequency. This is because the external conditions are symmetric under a time translation (i.e. a delay) by the period duration. This symmetry is normally preserved by the system.<p>A time crystal, however, will oscillate with a fraction (or rational multiple) of the driving frequency. This breaks the original time translation symmetry.<p>The analogy with normal &#x27;spatial&#x27; crystals is through this symmetry breaking: Empty space is symmetric under all translations, but a crystal spontaneously breaks the symmetry group down to the smaller set of &#x27;translations by a multiple of the lattice constant&#x27;.<p>The continuous symmetry of time translations cannot be spontaneously broken, due to thermodynamic arguments. Instead, we explicitly break down the time translation symmetry to &#x27;delays by a multiple of the period duration&#x27;. A time crystal then spontaneously breaks the symmetry down even further, by multiplying the period duration &#x2F; dividing the frequency.<p>[0]: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Time_crystal" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Time_crystal</a>