tag #solar-system 1 reading card on “solar-system”, in chronological order. Part of the full archive. 2026-05-14 Neptune The planet that was found with the point of a pen. In the summer of 1846, a French mathematician who had never looked through a telescope wrote a letter to Berlin, telling a German astronomer exactly where to point one. That night, a new planet appeared — within one degree of the predicted position. It was the first world in history discovered not by sight, but by pure mathematics.
