Part 2/12:
At the core of time perception is a process called entrainment—the way our internal biological and psychological systems synchronize with external events. The most pervasive and constant form of entrainment stems from our circadian rhythms, which are approximately 24-hour cycles primarily regulated by light exposure.
Light, detected by specialized cells in our eyes, influences the secretion of melatonin—a hormone responsible for sleepiness and hormone regulation. Longer days mean less melatonin production, boosting our energy levels, while shorter days increase melatonin, often leading to lower energy and mood during winter months. This cyclic pattern aligns our internal systems with the external environment, providing a reliable measure of yearly and daily time.