Virtual Skylights

from Artificial Sky

The brain’s hypothalamus controls our circadian rhythms, but they are also directly affected by light. When it’s dark, your eyes send a signal to the hypothalamus that it’s time to feel tired. Your brain, in turn, sends a signal to your body to release the hormone melatonin, which makes you feel sleepy. That’s why your circadian rhythm tends to coincide with the cycle of daytime and nighttime (and why it’s so hard for shift workers to sleep during the day and stay awake at night).
Virtual Skylights by Artificial Sky