As of the writing of this post, the first lunar eclipse of 2011 is underway, visible on at least part of every continent except North America. (Homo sapiens stuck in North America can view pictures and feeds of the eclipse on a number of websites, including Google's homepage.) It's the longest lunar eclipse since 2000. Like many other natural wonders, for centuries most people believed lunar eclipses to be heaven-sent omens, sometimes even changing the course of wars. Although these spectacles are no longer the scientific mysteries to the wider public that they once were (in spite of sports fans' determination to read the astronomical tea leaves), unlike other natural phenomena (floods or forest fires, for example), the patterns behind solar and lunar eclipses are so precise that astronomers can predict both future and past eclipses to the day, allowing astronomers to calculate the dates of ancient events.

Four years ago, astronomers from Rockefeller University in New York sought to confirm a date for one of the earliest solar eclipses mentioned in human history. In the 20th book of Homer's Odyssey, the seer Theoklymenos warns Penelope's suitors of their impending deaths, and ends his prophecy thus:  "the sun is blotted out of heaven, and a blighting gloom is over all the land." Ancient scholars, including Heraclitus and Plutarch, have long noted that the line suggested a total solar eclipse. In 1926, astronomer Carl Schoch went so far as to suggest a specific date, April 16, 1178 BCE, but Homeric scholars have rarely given credence to the theory, believing it unlikely that Homer would know of a specific eclipse that occurred some five centuries before the story was composed as we know it today. To further test Schoch's proposed date, the authors analyzed the rest of the text for astronomical references, finding three: Odysseus navigating using the constellations Pleiades and Bootes (which only share the sky in March and September), Venus rising in the sky before dawn when Odysseus arrives at Ithaca, and a reference to the god Hermes traveling "far west to Ogygia" to deliver news, then "immediately travel[ing] back east." The authors argue that the third passage describes the planetary motion of Mercury (the Roman name for Hermes), which reverses course in the sky every 116 days. Because a new moon is necessary for a solar eclipse, the authors compared new moon dates between 1250 and 1150 (around when the real Trojan War is believed to have occurred) to the three conditions mentioned elsewhere in the epic. They found only one date that matched: April 16, 1178 BCE. Seems Homer knew his astronomy pretty well.