Birds migrate thousands of miles without a map, a compass, or a GPS signal. How? Quantum physics. And it has direct implications for what we do on the mat. Birds have a protein in their eyes called cryptochrome. When light hits it, it creates what physicists call a radical pair — two molecules with entangled electrons that are sensitive to Earth's magnetic field. The bird literally sees magnetic field lines superimposed on its normal vision. North and south appear as patterns