A robin: inside her small dark eye, a quantum entanglement | Helen Sullivan

A symbol of spring and rebirth, the robin is a favourite of gardeners and inspiration for poets and dreamers

What is it about the poem Who killed Cock Robin?" It is so sad, and so coolly dark: a miniature drama played out in the shade of a single tree. The sparrow confesses right away, and nobody minds. The fly - I, said the fly, with my little eye, I saw him die" - is a witness of whom no questions are asked. Everyone seems eager for the burial, eager to help, insincere in their mourning, a-sighing and sobbing".

Everything is small. The fish catching blood in his little dish", the rook playing parson with his little book". The death of a little bird, and a funeral for a bird the size, and almost the shape, of an orange, and weighing no more than an orange segment.

One of the electrons migrates a few nanometers away, where it feels a slightly different magnetic field than its partner. Depending on how the magnetic field alters the electron's spin, different chemical reactions are produced. In theory, the products of many such reactions across a bird's eye could create a picture of Earth's magnetic field as a varying pattern of light and dark.