One of the fascinating things about the cyclical movements of the earth, moon, and other celestial bodies is that when you know enough about them, you can pinpoint their positions for any date in history. We can use this knowledge to add in details for all kinds of historical events, and even figure out why things happened the way they did. One case of historical mystery solved by astronomy is the disagreements set forth in the famous "Almanac Trial,” in which a lawyer named Abraham Lincoln brilliantly cast doubt on witnesses against his client.
In 1858, Lincoln defended one William "Duff" Armstrong, who was accused of killing James Preston Metzler on due to injuries from a brawl. The key witness in the case claimed that he had seen the brawl in full moonlight, but Lincoln produced an almanac that showed that, at the time of the brawl, the moon would have been near the horizon, nearly out of sight. Armstrong was acquitted, but after the trial, people began to wonder if the almanac was a fake. After all, numerous people remembered seeing a bright moon that night. Should we start calling him "Dishonest Abe"?
Probably not, although there is a reason the townsfolk remember seeing such a bright moon. It turns our that the night of the brawl, the moon was at a very special point in a 18.6-year cycle. The tilt of the Earth's axis and the tilt of the lunar orbit resulted in a very unusual, extreme passage through the sky. So early in the evening, the moon did indeed cross the meridian of the sky, but just a few hours later — at the time of the brawl — it was nearly out of view. Both the almanac and the townsfolk were correct.
That’s only one story. You’ll find eight more cases of astronomy solving historical mysteries at io9. -via the Presurfer