Swara yoga is the old Indian science of watching the breath itself — specifically, which nostril is carrying more air at any given time. The central observation, recorded in texts such as the Shiva Swarodaya, is that healthy breathing is not evenly split between the two nostrils. One side dominates for a while, then the flow shifts to the other, in a rhythm that changes through the day.
The left nostril is associated with the Ida nadi — cooling, lunar, associated with rest and reflection. The right nostril is the Pingala nadi — heating, solar, associated with action and exertion. Swara yoga further maps the breath onto the same five elements this whole site is organised around: as the nostril dominance shifts, the tradition holds that a different element — earth, water, fire, air or space — briefly dominates the breath itself, each with its own characteristic length and direction of exhale.
Practically, the tradition was used as a timing guide: calm, reflective work when the left nostril flowed; demanding or difficult work when the right nostril flowed. Alternate nostril breathing — Nadi Shodhana — is the practice most people encounter today, usually taught simply as a calming technique, stripped of the older predictive framework.
The nasal cycle itself — alternating congestion and decongestion between the two nostrils over a period of roughly two to four hours — is a real, measurable physiological phenomenon, studied in conventional medicine since the late 19th century. What is not established is the wider predictive and diagnostic framework built on top of it — that a given nostril dictates which kind of work will succeed, or that mismatches signal approaching illness. Alternate nostril breathing itself is gentle and, for most people, safe to practise.