bio

Cryptochrome

A light-sensitive protein in the retina of migratory birds, thought to be the heart of the quantum magnetic compass. When a photon of blue light strikes it, an electron is kicked across the molecule, leaving a radical pair whose quantum spins are linked. The rate at which that spin pair flickers is sensitive to the angle of the surrounding magnetic field, so the signal the molecule sends to the brain changes with which way the bird's head points - turning molecular chemistry into a direction sense. It is an inclination compass, reading the dip angle of the field lines rather than north and south.