Interesting new research on the concept of ["time crystals"](https://www.sott.net/article/341047-Time-crystals-Scientists-have-confirmed-a-brand-new-form-of-matter). This appears to be an oscillation in a lattice structure, perhaps akin to phonons, but I can't tell from this paper. What is interesting is this statement:
>The two lasers that were periodically nudging the ytterbium atoms were producing a repetition in the system at twice the period of the nudges, something that couldn't occur in a normal system.
> "Wouldn't it be super weird if you jiggled the Jell-O and found that somehow it responded at a different period?" said Yao.
> "But that is the essence of the time crystal. You have some periodic driver that has a period 'T', but the system somehow synchronises so that you observe the system oscillating with a period that is larger than 'T'."
They find it unusual that a period doubling in jiggled Jell-O occurs? I suppose that would happen if one doesn't know the scientific literature. This is from [Ibrahim's book on sloshing](https://books.google.com/books/about/Liquid_Sloshing_Dynamics.html?id=ctvhvH74ZzEC)
Note that both Faraday and Rayleigh observed period doubling. Rayleigh's original paper [On Maintained Vibrations](http://www.tandfonline.com/doi/abs/10.1080/14786448308627342?journalCode=tphm16) is an interesting read.
A liquid is not a crystal, yet phonons jiggling a crystal is the acoustic wave equivalent of a liquid sloshing.
And the reason I commented in this thread is because I believe the same period doubling behavior features in the sloshing dynamics of ENSO. This is the same Mathieu equation formulation that I apply to refine models of the behavior.