The theory of elasticity is essential in engineering. The most basic law is that any piece becomes smaller if one compresses it. My question is:
How can a piece of material expand (some minutes, hours, or days) after being compressed?
It is against our intuition. A related topic is the development of (meta)material with negative Poisson's ratio, which is also counterintuitive.
I suppose such material is possible, for example, a linear spring (as harmonic oscillator) with a very long period (you press it today, it expands tomorrow). I am wondering whether there is subfield developing such unusual material.