Starved of environmental cues telling us when it's time to go to sleep, our sleep cycles are actually a little longer than twenty-four hours.
How does the body know when to wake up? How does the body know when to fall asleep?
Surprisingly, even though there is no light to catch, the sunflower will continue to bend every day just as it did when it was outside. This is a classic example of what scientists call a circadian rhythm — it’s a daily cycle of behavior that is internal to the organism, rather than being solely triggered by the environment.