Zhang Heng
78–139 CE · Chinese (Han Dynasty) · Han Dynasty China
Known for: Invented the first seismoscope, improved the armillary sphere, and calculated pi accurately
Zhang Heng was a polymath who invented the world's first earthquake detector—a bronze vessel with dragon heads that dropped balls into frog mouths when seismic waves were detected. He also improved the armillary sphere, calculated pi to remarkable accuracy, and was a talented poet and painter.
He argued against superstition and advocated for empirical observation in an era when most explanations were supernatural.
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