The first earthquake detector was built by the Chinese scholar Zhang Heng in 132 CE: a bronze urn ringed with eight dragon heads, each holding a ball above a toad — a tremor dropped the ball, pointing at the quake. The modern seismograph came from John Milne in Japan, whose pendulums of about 1880 first recorded ground motion faithfully.
Zhang Heng's device could reportedly detect distant quakes the capital could not feel — court records describe officials dispatching inspectors toward the indicated direction. Milne's instruments, recording shaking on smoked paper, founded seismology as a science: for the first time, earthquakes left a written trace.
