Though comets appeared to the general population as spontaneous events, ancient Greco-Roman astronomers were familiar with the theory that these smaller bodies, such as the planets, moved along orbital paths. Some of the more notable works of ancient astronomy from the Greco-Roman world include Aristotle’s Meteorologica and De Caelo, Seneca’s Naturales Quaestiones, Pliny’s Naturalis Historia and Claudius Ptolemy’s Almagest and Tetrabiblos.