Making sense of the maths

When, 99 years ago, Werner Heisenberg invented the first real theory of quantum mechanics, he didn’t worry much about what it meant. That’s to say, he didn’t try to articulate it as a picture of what the world was like. It was purely a mathematical formalism, an austere calculus of matrices that enabled him to make predictions about, say, the spectra of atoms, based on quantities that had already been measured.

Defending this absence of a physical picture in 1930, Heisenberg wrote that: ‘It is not surprising that our language should be incapable of describing the processes occurring within the atoms, for it was invented to describe the experiences of daily life, and these consist only of processes involving exceedingly large numbers of atoms.’