The biological clock
What a conductor is to an orchestra, the biological clock is to the body. It is a part of the brain that synchronizes our circadian system to a 24-hour day/night cycle. Without this synchronization, our sleep patterns would shift every day to the point where people would not be awake at the same time. Several synchronizers act simultaneously to maintain the rhythm: the most powerful of these is light.
Natural light synchronizes biological rhythms. When the brain is exposed to natural morning light, it blocks the production of melatonin (the hormone responsible for sleep) via the information it receives from the retina and produces the waking hormone.
Exposure to natural light is essential for our general well-being; it activates the production of serotonin, the hormone involved in mood management and associated with happiness.
Formerly called light therapy, phototherapy can counteract the adverse consequences of a lack of natural light, especially in winter. This therapy involves exposure to high intensity light (5000 – 10,000 lux) for a set amount of time (30 minutes). You simply place the light therapy lamp in the part of the house where you start your day (dining room, dinette, living room) and soak in the light for a moment to re-energize yourself and also to ensure you sleep soundly come bed time.
The secretion of melatonin increases at the end of the day shortly before bedtime, helping us to fall asleep. It reaches its peak between 2 and 4 a.m. and then gradually falls to negligible levels early in the morning, shortly after waking up. Exposure to light in the evening delays the biological clock, and thus the production of melatonin and drowsiness.
In sum, light is nothing to trifle with! You need to take it seriously and be in synch with it. Soaking up the light at the right time is one of the keys to sound and restful sleep.