The two Ayanams are ushered in by the sun and the moon changing their respective courses in the heavens (passing over the tropics of Cancer and Capricorn) as the measurers of time. The rains, autumn and Hemanta follow one another in succession when the sun is over the Tropic of Capricorn or is in the Winter Solstice (Dakshinayanam) and the moon gains in strength in this part of the year. Rasas (Serum or sap) possessed of acid, saline and sweet tastes, grow
strong and become dominant when the sun is over the Tropic of Capricorn (Dakshinayanam) and all beings gain in strength and energy more and more. Winter, spring and summer mark the passing of the sun over the Summer Solstice (Uttarayanam). The sun grows stronger in heat and light, and saps rasas of bitter, pungent and sour tastes increase in intensity, and all animals gradually begin to lose strength and energy.
Authoritative verses on the subject:—The moon imparts the moisture and humidity to the earth which is soaked up by the sun in his daily course, while the wind in conjunction with the sun and the moon, contributes towards the preservation of animal life. The successive change of the two solstices marks a year.
Five such complete years count as a Yuga. The sub-divisions of eternal time from the minutest Nimesha to a complete Yuga, are constantly revolving like a wheel,
