Nature World News: The process by which a planet overheats and enters the uninhabitable phase known as the "runaway greenhouse" stage might occur much more easily than previously thought, according to new research by astronomers at the University of Washington and the University of Victoria. In the runaway greenhouse stage, a planet absorbs more solar energy than it can give off to retain equilibrium and, as a result, the world overheats and its oceans boil, filling the atmosphere with steam. When this happens, the...