Sunlight is essential for all living organisms.
Photosynthesis in plants is light energy converted to carbohydrates, food for insects, animals, and eventually the soil. Light direction and duration promotes the plant growth cycle. Plants turn toward the light. Sunflowers are harbingers of autumn. The diminishing light sends plants into dormancy. Daylight and night rhythm expressed.
For mammals, light and dark rhythm creates the circadian flow in an almost 24 hour period. Sleep, dream, wake, hunger, content/wellbeing, activity, hormone regulation, slowing down, moving into sleep.
Light receptors in our eyes and skin produces the neurotransmitter serotonin and sends information to the pineal gland to produce melatonin. Endocrine system in flow with the earth cycle. The pineal gland initiates the circadian rhythm.
The pineal gland has been called the third eye, producing insight and inner wisdom. In many lizards and frogs there is a parietal eye, the third eye is visible, it winks at the daylight and offers a direct route inward. Daylight produces wakeful consciousness; nighttime produces dream state consciousness. Luminance.