Members of the court thought the device had failed when the alarm sounded one day and they felt nothing. Doubt turned to astonishment a few days later. A messenger arrived from a town 400 miles away to report that it'd been savaged by an earthquake.

Chinese writings talked about Chang Heng's seismograph and ones like it until the Mongols overran China. After that, it vanished as though it had never been...And why is such brilliance so badly remembered? It's probably because people like Chang Heng were tied so tightly to their patrons. They didn't belong to the same loose, open communities of freely moving scholars that have diffused knowledge so effectively in the West.

They tried to recreate these on a mythbusters episode. Very interesting!

I'd never heard of it,very interesting,thanks