Editing Seismometer (section)

=== Ancient era ===
[[File:EastHanSeismograph.JPG|thumb|Replica of [[Zhang Heng]]'s seismoscope ''Houfeng Didong Yi'']]
{{See also|List of Chinese inventions}}

In [[Ancient Egypt]], [[Amenhotep, son of Hapu]] invented a precursor of seismometer, a vertical wooden poles connected with wooden gutters on the central axis functioned to fill water into a vessel until full to detect earthquakes.

In [[AD 132]], [[Zhang Heng]] of China's [[Han dynasty]] is said to have invented the first seismoscope (by the definition above), which was called ''Houfeng Didong Yi'' (translated as, "instrument for measuring the seasonal winds and the movements of the Earth"). The description we have, from the [[Book of Later Han|History of the Later Han Dynasty]], says that it was a large bronze vessel, about 2 meters in diameter; at eight points around the top were dragon's heads holding bronze balls. When there was an earthquake, one of the dragons' mouths would open and drop its ball into a bronze toad at the base, making a sound and supposedly showing the direction of the earthquake. On at least one occasion, probably at the time of a large earthquake in [[Gansu]] in AD 143, the seismoscope indicated an earthquake even though one was not felt. The available text says that inside the vessel was a central column that could move along eight tracks; this is thought to refer to a pendulum, though it is not known exactly how this was linked to a mechanism that would open only one dragon's mouth. The first earthquake recorded by this seismoscope was supposedly "somewhere in the east". Days later, a rider from the east reported this earthquake.<ref name=sivin>{{cite journal |author=Sleeswyk AW, Sivin N |title=Dragons and toads: the Chinese seismoscope of BC. 132 |year=1983 |journal=[[Chinese Science]] |volume=6 |pages=1–19}}</ref><ref name=needham>{{cite book |last=Needham |first=Joseph |title=Science and Civilization in China, Volume 3: Mathematics and the Sciences of the Heavens and the Earth |place=Cambridge |publisher=Cambridge University Press |year=1959 |pages=626–635 |bibcode=1959scc3.book.....N}}</ref>