“Chrono” means time and “Biology” means the study of life. Chronobiology creates a lifestyle according to specific changes which are innate in your body. This means we have an internal clock and this internal clock determines the production of hormones and, when coupled with exposure to light, it creates photoperiodism. The earth rotates so there is sun at midday and when the sun goes down at 6 o’clock for example, there is no more thermal emission, no more ultra violet and, so on.
The rhythms are all driven by the fact that we are living on a sphere that rotates, and we have an internal adaptation system – our circadian clock – to try to adapt to these rhythms.