It wasn’t long ago, relatively speaking, that humans woke and slept along with the rise and setting of the sun.
While the invention of modern artificial lighting has allowed us to be productive 24 hours a day, even in what would otherwise be the black of night, our bodies have not adapted to this onslaught of light when it should be dark.
Humans have long existed with the glow of firelight, and its corresponding yellow, orange and red wavelengths do not appear to have the detrimental effects (such as suppression of melatonin production) of other wavelengths of light, like white and blue.
Blue light, which is prevalent when the sun is bright and overhead, is particularly problematic. Photoreceptors, or light-sensitive cells, in your eyes track blue light, which in turn triggers different processes in your suprachiasmatic nucleus, a small region in your brain’s hypothalamus.