Are there any quantum effects that we can see day to day?

LIAM FARMER, BIRMINGHAM

As they govern the behaviour of atoms, quantum effects underpin everything from the ability of plants to turn sunlight into chemical energy to the behaviour of semiconductors in microchips. Their influence is, however, usually subtle and hard to see directly. Perhaps the most spectacular demonstration of quantum effects, pure and simple, is a magnet. Despite its familiarity, magnetism is actually impossible without quantum effects, which are needed to explain the necessary behaviour of atoms. For example, the ability of a simple bar magnet to pick up a needle is the result of the so-called Pauli Exclusion Principle, a key component of quantum theory that dictates how electrons are arranged.