Ramanujan’s letter to G. H. Hardy

1. He said that before the industrial era, nobody slept 8 hours in one block. People slept in two parts: they went to bed after sunset, woke up around midnight, stayed awake for 1–2 hours, then went back to sleep. This “split sleep” was normal for thousands of years. But when factories appeared in the 19th century, society forced everyone into one long sleep window — and the body never fully adapted. He said the modern schedule confuses the brain: it doesn’t understand when it should rest and wh