On Christmas Day, 1758, a German amateur astronomer and farmer named Johann Georg Palitzsch did something that would have made a great Christmas gift for English astronomer Edmond Halley. Johann “recovered” Halley’s Comet, meaning he was the first to observe this previously observed “dirty snowball” as it returned to the inner solar system. Edmond Halley (1656-1742) calculated the orbit of the comet that now bears his name based on previous sightings...