Ludovico Ariosto, in his epic Orlando Furioso (1513),[4] jestingly sent his hero to a Moon where everything lost on Earth eventually turns up; but it was not until Galileo discovered (1609–1610) that the Moon had surface features, and that the other planets could, at least, be resolved into disks,[5] that the concept that the planets were real physical bodies came to be taken seriously. In 1543, Nicolaus Copernicus had already posited that the planets orbited the Sun as the Earth does; combined, these two concepts led to the thought that the planets might be "worlds" similar to the Earth.[6] Public expression of such concepts could be dangerous, however; Giordano Bruno was martyred in 1600 for, among other things, imagining an infinite number of other worlds, and claiming that "Innumerable suns exist; innumerable Earths revolve about these suns ... Living beings inhabit these worlds" in De l'infinito universo e mondi ("Concerning the Infinite Universe and Worlds", 1584).[7]