All living things require light for life. Light is a trigger for a wide array of essential life functions from digestion to the sleep/wake cycle. The key is to get the right light quality at the right time to trigger healthy living, productive living and satisfying living.
Darkness is essential to sleep. If you’re exposed to natural or artificial light at the wrong time, this disrupts our body’s internal “biological clock” to the point that it will impact your sleep-quantity and quality.