Word: seismographic
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Dates: during 1990-1999
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...Shang Dynasty over 3,000 years ago. In the 2,100 years from the Qin Dynasty to the late Qing Dynasty (that is, from 221 B.C. to 1911), the 27 appearances of Halley's Comet were all recorded in China. Zhang Heng, of the Han Dynasty, invented a seismograph to determine the location of earthquakes, and the celestial globe that showed the movement of the sun, moon and other stars. Mathematicians in the pre-Qin days put forward the proposition known as the Pythagorean theorem in the West today. In the Northern and Southern Dynasties in the 4th century...
When Steim's seismograph was installed at Caltech in 1988, it replaced "something like over 40 specialized seismographs," according to Adam Dziewonski, professor of geophysics at Harvard...
...contrast to a tuning fork which can produce only one pitch at one volume, Steim's seismograph works like a grand piano by harmonizing various signals from one source to create a more polished and rich composition...
...Digital Seismograph is so precise that the unit at Harvard's Oak Ridge Observatory in Harvard, Mass., can detect "marine microseisms"--the "motion of the ground generated by wave action against the entire coastline," Steim says. Units in other locations have also detected volcanic explosions, the sonic wave generated by landing space shuttles and even trucks...
Although there were several attempts to create a global seismograph network in the 1960s and 1970s, Steim says the efforts focused less on science and more on the pressing Cold War need to detect nuclear explosions by measuring their shock waves...