7. The Movement of Light in Photosynthesis
The involvement of sunlight in the process of photosynthesis can be broadly divided into three stages. The first stage consists of those steps that result in sunlight reaching the cells of the leaf. This stage includes the process of nuclear fusion in the sun that emits photons, as well as that light's penetration into the earth's atmosphere. Once sunlight is absorbed into the leaf's cells, photosynthesis can be divided into two stages: the light cycle and the Calvin (dark) cycle. The light cycle of photosynthesis involves the conversion of the energy stored in the photons into chemical energy that the cells can later use in the manufacturing of the carbohydrates, while the Calvin cycle involves the actual carbohydrate synthesis.
One of the principal teachings of the Ba'al Shem Tov is that every genuine and complete 'movement' (i.e., activity in time or space) of the soul (or psyche), the chief metaphor for which is light, entails three stages referred to as Submission (, hachna'ah), Separation (, havdalah), and Sweetening (, hamtakah). In essence, photosynthesis is a process that uses sunlight to produce carbohydrates on the face of the planet. Hence it is natural that we find the essence of the Ba'al Shem Tov's three stages in the movement of light itself.
Following this 3 step process and looking for its application in the 3 steps of photosynthesis, we note that the most obvious correspondence is that between the final stage of photosynthesis, the production of carbohydrates in the Calvin cycle, and the (last) stage of sweetening-carbohydrates themselves being the source of sweetness.
The (first) stage of submission can be thought of as corresponding to the sun's 'surrendering' its light so that it can be 'captured' (and utilized) in photosynthesis.
Finally, the (middle) stage of separation finds expression in the light cycle when the energy of the photons is used to separate protons and electrons across the thylakoid membrane. That separation creates a potential difference (i.e. a chemical 'battery') that is used as an energy source for driving the synthesis of carbohydrates. Additionally, we find that the second step also involves the separation of water into oxygen and protons.
The Ba'al Shem Tov also explained that the three stages of submission, separation, and sweetening correspond to the words Silence (, hash), Circumcision (, mal) and Speech (, mal) . In terms of our comparison, this means that the submission of the soul, which we found to correspond to the sun 'submitting' its light, would correspond to the power of silence in the soul. This is hinted at by the additional meaning of the Hebrew word hash (silence) as 'speed' or 'haste' alluding to the fact that light travels at the fastest speed possible according to modern physics.
We summarize the parallels between these models and photosynthesis in the following table: