In addition to celebrating Christmas today, science history buffs might note that today is also the 250th anniversary of a notable return of Halley's Comet in the skies over Germany.

Edmond Halley was a contemporary of Isaac Newton. In addition to his own manifold contributions to science, he convinced Newton to write his seminal book, "Mathematical Principles of Science," and even paid for its publishing.

In Halley's time comets were thought to be one-time phenomena. In 1705, after searching historical records and calculating orbits, Halley published his hypothesis that four comets seen in the previous 250 years were actually the same comet, on an orbit that brought it back to the inner solar system every 76 years. He predicted the comet's return in 1758, but died 16 years too early to see if he had been right.

Given Halley's reputation, astronomers worldwide began to scan the skies in 1758. But as the year wore on and the comet failed to appear, most lost interest and wrote off Halley's prediction as a failure. What they didn't know was that - unlike planets - comets' orbital periods can vary considerably. When a comet crosses a planets' orbit, the planet's gravity can perturb the comet's motion. Also, as comets approach the sun, frozen gases are boiled away, producing a jet effect. Consequently, Halley's Comet was running nearly two years behind schedule.

Finally, on the night of Christmas, 1758, German amateur astronomer Johann Palitzsch spotted the tardy comet. The comet was immediately named in Halley's honor, securing his place in history. (Astronomical historians have since found nearly a dozen other historical records of previous apparitions of Halley's Comet, the oldest being Chinese chronicles written in 240 B.C.)

Palitzsch's name barely rises to the level of historical trivia nowadays. But perhaps we should at least acknowledge his posthumous Christmas gift to Edmond Halley.