A system made of just a handful of particles acts just like larger systems, allowing scientists to study quantum behaviour more easily.

Most substances physicists study are made up of huge numbers of particles—so large that there is essentially no difference between the behavioural properties of a drop or a swimming pool’s worth of pure water. Even a single drop can contain more than a quadrillion particles.

This makes understanding their collective behaviour relatively easy. For example, both the water in the drop and in the pool will freeze at 0C and boil at 100C.

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