In 1492, Christopher Columbus ignored advice that that the Earth was flat and tried to reach India by sailing west rather than east. He may have muddled his continents, but he didn't fall off the 'edge' - the Earth's surface is of course curved. Researchers now announce that the answer is yes. Common sense tells us that flying through space in a straight line gets you further and further away from your starting point.
Researchers have no difficulty accepting a universe in which space itself is curved.
Fly for long enough in curved space and you could find yourself back where you started. But the curvature of a universe doesn't just bend the brain, it also has a far more worrying conclusion. A universe that contains enough mass to give it a positive curvature is doomed to a fiery end. It will gradually stop expanding and begin to shrink, ultimately imploding in a cataclysmic 'big crunch'. A universe with zero curvature, a 'flat universe', escapes this demise.