The most prudent thing any intelligent animal can do, if it would prefer its descendents not to spend a lot of time on a slab with electrodes clamped to their brains or sticking mines on the bottom of ships, or being patronised by zoologists, is to make bloody certain humans don't find out about it.
Terry PratchettThe disc, being flat, has no real horizon. Any adventurous sailor who got funny ideas from staring at eggs and oranges for too long and set out for the antipodes soon learned that the reason why distant ships sometimes looked as though they were disappearing over the edge of the world was that they were disappearing over the edge of the world.
Terry Pratchett