the.com/circadian
Your body's internal clock, ticking whether or not you respect it.
means Describing biological rhythms that cycle roughly every 24 hours, like sleep, hunger, and alertness.
from Coined in 1959 from Latin circa (around) and dies (day) — literally about a day, because the rhythm runs close to 24 hours but not exactly.
Runs longHuman clock free-runs near 24.2 hours.
Light sets itMorning sunlight resets the master clock daily.
Even plantsLeaves open and close on schedule, unprompted.