Zooplankton in the Arctic dive down to about 50 meters deep every month when the full moon happens, and they all do it at the same time—like clockwork—suggesting the moon controls their movement in the winter.

Arctic ocean plankton move up and down in the water every 24.8 hours during the dark winter, matching the moon's cycle — and scientists think moonlight is what tells them when to move, even in pitch-black seas.