Comets have been known since ancient times

• known to ancient Greeks and Romans as "bearded stars"

• recorded on many ancient Chinese star charts, known as "broom stars"

• at one decade per major comet, generally portended as some kind of omen

Aristotle (350 B.C.) determined comets were in our atmosphere.

• not based on observational evidence.

• Aristotle felt that the heavens should be unchanging