KentuckyFC (1144503) writes "The history of astronomy is littered with ideas that once seemed incontrovertibly right and yet later proved to be bizarrely wrong. Not least among these are the ancient ideas that the Earth is flat and at the center of the universe. But there is no shortage of others from the modern era. Now one astronomer has compiled a list of examples of wrong-thinking that have significantly held back progress in astronomy. These include the idea put forward in 1909 that telescopes had reached optimal size and that little would be gained by making them any bigger. Then there was the NASA committee that concluded that an orbiting x-ray telescope would be of little value. This delayed the eventual launch of the first x-ray telescope by half a decade, which went on to discover the first black hole candidate among other things. And perhaps most spectacularly wrong was the idea that other solar systems must be like our own, with Jupiter-like planets orbiting at vast distances from their parent stars. This view probably delayed the discovery of the first exoplanet by 30 years. Indeed, when astronomers did find the first exo-Jupiter, the community failed to recognize it as a planet for six years. As Mark Twain once put it: 'It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so.'"