In the 19th century, people living near the Barisal region of Bangladesh kept hearing what sounded like distant cannon fire booming out of a clear sky. The Barisal guns became one of the best-known examples of a "skyquake," a sudden loud sound with no corresponding earthquake activity.
The same unexplained noises turn up all over the world, and locals have given them their own names: mistpoeffers, or "fog dissipators," in Belgium and the Netherlands; Seeschießen, "sea gunshots," in Germany; brontidi, "thunder-alike," in Italy. They have been reported along the U.S. East Coast and the Finger Lakes, across the North Sea, in Japan, and even far from any water in the American Midwest, where they have been blamed on cold weather.
Proposed causes range from ocean waves broken up by coastal topography to shifts deep underground. The source has never been pinned down.
