When a baby sea turtle scrambles down a beach into the ocean, you might not think it’ll ever see that beach again. But females will. Decades later, after 10 to 30 years of wandering open ocean, the same turtle returns to the exact beach where she hatched, crawls ashore, and lays her own eggs.
Sea turtles do it by reading the Earth’s magnetic field. Every spot on Earth has a slightly different “magnetic signature” - a unique combination of field strength and angle. The hatchling memorizes the signature of her birth beach. Years later, she uses it as a homing beacon.
Even baby turtles freshly out of the egg use the field to swim in the right direction toward open ocean. Scientists have proven this by tilting the magnetic field around hatchlings in a lab tank - and watching them swim the “wrong” direction with full confidence.
