As the sun sinks low in the west, other lights come awake.

And the nightly pyrotechnics of San Diego's theme parks add an extra splash of color.

These bright nights distract us from a ritual older than our entire species Just offshore single-celled algae called dinoflagellates are starting to reproduce.

If disturbed, a chemical reaction inside each cell creates a tiny spark of light.

When the conditions are just right, the algae multiply to uncountable numbers.

And the coast becomes electric.

But most San Diegans never notice it, and in a few hours the show is over.