The Nobel Prize in Physiology or Medicine 2017 was jointly awarded to three American scientists who uncovered the secrets of biological clocks.
The biological clock is literally a built-in clock in the body maintaining circadian rhythm, which acts to keep the body alert and active during the day and falling asleep at night.
Interestingly, one day is 24 hours based on the Earth's rotation cycle, but the intrinsic period of the human circadian pacemaker has been measured 24.2 hours which is longer than the rotation cycle.
Nevertheless, we are able to live a life of 24-hour periodicity because the light received through the eyes is transmitted to the biological clock, so that it can be synchronized to the external world of 24 hours.
In fact, patients with anophthalmia have no eyeballs that can accept light, so they are suffered from a broken rhythm pattern presenting frequent sleeping and awakening cycle.
In addition to the sleep-wake rhythm, the biological clock fine-tuned through interactions with the external environment such as light carries out various activities that are fundamental to life maintenance including body temperature, pulse, and hormone secretion.
The expression "Light is a Source of Life" is probably based on these scientific reasons.
A-Young Lee Ph.D Biologist Head of Our Healthcare Committee