It is always worth remembering that today's unorthodox cosmology sometimes becomes tomorrow's accepted fact. For centuries the Ptolemaic view of the universe held sway. This had the Earth at the centre of all creation, with the moon, sun, planets and stars travelling around it in their different spheres. Generally it was believed that the Earth was flat, despite the fact that ancient Greek philosophers such as Aristotle and Eratosthenes had proved it to be a ball and even calculated its diameter. Mariners must have known, through observation, that the Ptolemaic Theory was nonsensical, yet they continued to use it because it gave suitably accurate results for navigation use. By the 16th Century, however, dissent concerning the theory was growing among the intellectual community. In 1593 Copernicus, on his deathbed, published his theory that the Earth and the other planets orbited the sun. His ideas were attacked by both religious and scientific authorities, but within decades had become generally accepted. It is hard to believe that some of the wilder theories in circulation today bear any truth.