Factgirl's fact of the day:

In Jonathan Swift's 1726 classic, Gulliver's Travels, there is a statement that Mars had two moons, at a distance of three and a half diameters from Mars respectively, the nearest one revolving in ten hours and the outermost in twenty-one and a half hours.

This statement is a remarkable one, because the existence of those moons was not established until August 1877 by Asaph Hall. Their distance from Mars, and the length of their orbits also corresponded to Swift's suggestion. The inner moon is the only known body in the universe that revolves around a central body faster than the central body rotates - this fact is also included in Swift's writing.

A few crackpots over the years have attributed this phenomena to Jonathan Swift being from Mars; More likely he read Galileo's discovery of the four moons of Jupiter and (wrongly) assumed that each planet had moons in geometric progression: no moons for Venus, one for Earth, two for Mars, and Jupiter four.

-it's a fact!