Max Planck did not mean to overthrow all human notions of order in the universe; he simply wanted to understand how light bulbs work. At the dawn of the 20th century, there was no formula that fully explained how the colour of the light emitted by an object changes as its temperature rises. Planck found one, but only by committing an ‘act of desperation’: he abandoned the common-sense position that they could absorb or emit any amount of energy they liked and instead assumed that they were restricted to discrete packets – or quanta – of energy instead.
So began a century of tumult. Planck’s reluctant breakthrough was developed further by Albert Einstein, Niels Bohr, Werner Heisenberg, Erwin Schrödinger and other luminaries to explain the deeply peculiar behaviour of subatomic particles: photons, electrons and their ilk. The descriptions they devised are among the most successful in any branch