The Two Moons of Mars (1726)
More than a hundred years before we learned that Mars has two moons, Phobos and Deimos, Jonathan Swift made an educated guess about the Red Planet. In his 1726 novel, he wrote about “two lesser stars, or satellites, which revolve about Mars.”
Even more remarkably, he predicted their sizes and speeds of rotation: “…The innermost is distant from the primary planet exactly three of his diameters, and the overmost five; the former revolved in a space of 10 hours, the latter in 21.5” Given that no technology existed yet that would’ve made Mars visible, Swift’s prediction has confounded everyone, from NASA scientists and Harvard professors.
