Korean scientists think they have determined what caused a 39-story Seoul skyscraper to shake violently for 10 minutes, causing the building to be evacuated for two days. Earthquake? Nope. Gale-force winds? Sorry. Volcanic activity? Unh-uh. No, the culprit, they say, was 17-middle-aged gym rats working off the midriff bulge in a Tae Bo class. Apparently, [...]