Today, 60% of the world and 99% of the United States experiences a devoid of total darkness due to light pollution. How does the ubiquitous presence of artificial light impact human beings and other creatures? In this essay for Aeon, journalist Rebecca Boyle investigates the wealth of scientific research behind this question. For example, a team at the Max Planck Institute found that even small amounts of streetlights suppressed melatonin release in blackbirds. Another study, headed by circadian biologist Randy Nelson, found that exposing Nile grass rats to light at night seemed to increase their rates of depression and obesity. Other researchers have been focused on solutions: NASA, for example, has found that red hued lights seem to disrupt sleep less that blue hued light. To learn more, check out the full essay.