These cycles and the principles of Ayurveda are not random. They correspond to a keen awareness of astrophysics and the ways in which the forces in the larger universe affect our bodies. To understand Ayurveda, we must remind ourselves continually of the adage, ‘as in the macrocosm, so in the microcosm’. In Sanskrit, we call this - ‘Yat Pinde, tat Brahmande’. It cycles from the macrocosm to the microcosm, stating,’ as in the world out there, so is the body in here’.
There are three recurring cycles in nature, driven by forces that correspond to physiology in our body.
The first cycle is the solar cycle- the rotation of the earth on its own axis, causing the day-night cycle. This is understood by the body through the pineal gland in the brain, which produces a series of chemicals, such as melatonin, and a cascade of signals along the hypothalamic-pituitary axis. These are thoughts, emotions, and activities via hormones, neurotransmitters and chemicals throughout the body that react in a fine-tuned web of intercommunication. This is where Ayurveda brings the concepts of Dinacharya and ratricharya ( Daily and nightly regimen). These principles are very precisely laid out to align with the solar cycle of the day including the time to wake up, eat, meditate, right time for intercourse, and sleep etc. Just recently, modern medicine discovered the importance to align ourselves with the circadian rhythms
The second cycle corresponds to the revolution of the moon around the earth. This gravitational lunar pull produces cyclic tides of the oceans, due to the frictional coupling of water with the earth’s rotation through the ocean floors, and the inertia of water’s movement. Lunar cycle heavily influences our state of mind. We can evidently notice these imbalances on a full moon day or a new moon day. It also corresponds to the menstrual cycle and corresponding hormonal flows in both women and men.
The third cycle corresponds to the revolution of the earth around the sun. It produces seasons and changes in nature that flow into cycles of perennial death and rebirth of flowering plants and herbs. The trees change their rhythms, as do animals, fields, and water. We perceive these changes in the environment through our five senses and fires in our bodies, increasing fires when it is cold and decreasing them when it's hot. So, Ayurvedic scriptures laid out Rutucharya - the seasonal regimen and influence of seasons on doshas and elements.