Dawn triggers basic biological changes in the waking human body. As the sun rises, so does heart rate, blood pressure and body temperature. The liver, the kidneys and many natural processes also begin shifting from idle into high gear. Then as daylight wanes and darkness descends, these processes likewise begin to subside, returning to their lowest levels again as we sleep.
These internal biological patterns are tightly linked to an external cosmic pattern: the earth’s rotation around the sun once every 24 hours. This endless loop of light and darkness and the corresponding synchrony of internal and external clocks, are called circadian rhythms, from “circa diem,” Latin for “approximately a day.” Circadian rhythms influence almost all living organisms, from bacteria to algae, insects, birds and, as is increasingly understood by science, humans beings. (more…)