Since primeval times, the appearance of bright comets has impressed humanity. But more detailed conclusions about individual comets or even their paths can only be obtained from written records, which are available from about 500 BC. The most complete reports of comets come from China, whereas reports from Europe are incomplete, and only single out certain individual comets. Chinese astronomers also gave details of the oldest cometary apparition that can be identified nowadays, from the year 613 BC. Readily understood indicators are provided by Halley's Comet, which was observed in the years 240, 164, 87 and 12 BC. After the birth of Christ, it appeared in AD 66, 141, 218, 295, 374 and 451.

One of the oldest comets documented from Europe is the Great Comet observed by Aristotle in the winter of 373–372 BC. The Greek thinker saw it in his childhood. He later wrote in his work Meteorologica: “its light stretched as a great ribbon across one third of the sky”. Aristotle linked the comet with an earthquake and with a ‘tidal wave’ that the latter produced – an early example of the interpretation of comets as harbingers of disaster that persisted into modern times. According to Diodorus, witnesses claimed that the comet had cast shadows like the Moon. A few chroniclers report that the comet eventually ‘broke into two planets’. According to modern analysis, it was probably a sungrazer, which broke up after a close approach to the Sun. If this is so, the Comet of 372 BC may be the parent comet of the Great Comets of 1680 and 1843.

Dating from the year 240 BC, the first full sightings of Comet Halley come from China and Mesopotamia. At its return in 164 BC the apparition of the comet was documented on Babylonian cuneiform tablets. The comet of 135 BC is famous for appearing at the birth of King Mithridates VI of Pontus. It was visible for 70 days; Seneca described it, according to eye-witnesses, as “stretching out like the Milky Way”.