
𝙋𝙖𝙧𝙖𝙢𝙖𝙩𝙢𝙖 is like an eternal ocean and 𝙖𝙩𝙢𝙖 is an imperishable drop that is surrounded by the perishable human body. Krishna describes that ocean and says, "Know that brilliance to be mine which residing in the sun illuminates the world, which is in the moon as well as in fire (15.12). Permeating the earth, I nourish all living beings with energy. Becoming the moon, I nourish all plants with the juice of life (15.13).
Having become 𝙑𝙖𝙞𝙨𝙝𝙫𝙖𝙣𝙖𝙧𝙖 (fiery power), I exist in the body of living beings, united with 𝙥𝙧𝙖𝙣𝙖 (inhalation of breath) and 𝙖𝙥𝙖𝙣𝙖 (exhalation), I digest the fourfold food (15.14). I am seated in the hearts of all beings; and from Me come 𝙎𝙢𝙧𝙞𝙩𝙞 (self awareness), 𝙂𝙮𝙖𝙣 (wisdom) and 𝘼𝙥𝙤𝙝𝙖𝙣 (clarifying doubts). I alone am to be known by all the 𝙑𝙚𝙙𝙖𝙨, am the author of the 𝙑𝙚𝙙𝙖𝙣𝙩 , and the knower of the meaning of the 𝙑𝙚𝙙𝙖𝙨" (15.15).
Firstly, Krishna says He is the brilliance of the sun (sunlight) and nourishes all living beings with energy. Plants convert it into the food we consume. Yesterday's sunlight is what we are using as fossil fuels. Sunlight keeps water in the liquid state. Hence, it enables us to exist and survive.
Secondly, Krishna chose the process of digestion and breathing as a metaphor to explain the numerous processes that happen in the human body. It's like the healing of a surgeon's incision; it's the harmony between various organs and chemicals in the body making it functional.
Science is good at answering the 'hows' but not the 'whys'. 'How light works' is explained but the answer to 'why is light dual' is left open. In these verses Krishna explains that he is behind these 'whys'. While we struggle to get a certain answer to 'how and why', these are nothing but HIS 𝙡𝙚𝙚𝙡𝙖 or divine drama.