Mirrors confine light, and light exerts pressure on mirrors. The combination of these effects can be exploited to cool tiny, flexible mirrors to low temperatures purely through the influence of incident light. Looking at how a poppy oscillates back and forth in a gentle breeze tells us something about the rigidity of the flowers stem and the strength of the prevailing wind. Observing the movement of a tiny mirror attached to a stem-like post in a 'photon breeze' might be similarly illuminating. Suchdisplacements could reveal the spooky quantum-mechanical behaviour of the mirror itself and maybe even gravity's role in quantum mechanics1 — no mean feat. The problem is that under normal, room-temperature conditions such effects are masked: the mirrorcontains an exceedingly large number of thermally excited atoms, so it is in a state of permanent random agitation around its average position on its stalk. And cooling by traditional cryogenic means does not go far enough to remove these 'non-coherent' thermal effects.
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