These days, if someone's heard of Jonathan Swift's 1726 satire of utopian literature "Gulliver's Travels," they probably know the most famous image of a regular-sized dude being tied down to the ground by the tiny-sized people of Lilliput. Movie and TV adaptations for kids sometimes give the impression that the book is a whimsical adventure, but Swift was actually writing a biting satire of contemporary society. He also sent his protagonist to a lot more places than Lilliput.
One of the other lands visited by Lemuel Gulliver was Laputa, a floating island full of mad scientists. Swift lampooned the burgeoning field of scientific inquiry within his society by portraying a bunch of dudes trying to figure out how to, for example, extract solar energy from food by running it backwards through the digestive tract. The Laputan astronomers, likewise, had discovered two small moons orbiting Mars, and the text gives the orbital distance and periods of the two satellites.
As the Neurologica blog points out, it wasn't for another 151 years that Phobos and Deimos, the two moons of Mars, were actually discovered by Asaph Hall in 1877. All things considered, the orbital distance and periods of the actual moons turned out to be, uh, not that far off from Swift's made-up statistics. It's possible Swift just got lucky, but he may also have used logical deduction based on existing information about moons within our solar system.
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