Theophrastus described a tamarind tree that closes its leaves at night and opens them at sunrise. This observation was reported by Androsthenes, a ship's captain serving under Alexander the Great.
Jean-Jacques d'Ortous de Mairan conducted his first experiment in 1729. He observed 24-hour patterns in the movement of Mimosa pudica leaves kept in constant darkness.
Jeffrey Hall, Michael Roshbash, and Young received the Nobel Prize in Physiology or Medicine 2017 for their work on the period gene. Their research identified the gene covers a 7.1-kilobase interval on the X chromosome.
Shift workers show increased rates of operational error and impaired visual-motor performance. They also face higher levels of resistin indicating plaque build-up and an increased risk of dementia compared to day shift workers.
Blue LED lighting suppresses melatonin production five times more than orange-yellow high-pressure sodium light. This suppression occurs because specialized ganglion cells contain the photopigment melanopsin and project directly to the suprachiasmatic nucleus.