Today is the winter solstice, with the shortest period of daylight and the longest night of the year. To mark the event, learn about the ticking clock inside us all during APM's "Brains On" one-hour science special, called "Tick, Tock, Circadian Clock."
Host Molly Bloom explores circadian rhythms, animal hibernation and how light and dark affect all life on Earth.
Our circadian rhythm is set by the cycles of the sun. They let us know when it's time to get up, when it's time to eat and when it's time to go to sleep at night.
Our circadian rhythms are close, but not quite on a 24 hour schedule, and not everybody operates with the same rhythm.
Our body clocks usually run between 22 hours and 26 hours.
Looking at our own rhythms can help us understand when the best time is to complete certain tasks.
To listen to the program, click the audio player above.