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Zhang Heng

Eastern Han Dynasty Polymath

Zhang Heng (AD 78–139) was a Chinese polymath whose scientific and literary achievements spanned astronomy, mechanics, seismology, and poetry. A brilliant inventor and observer, he introduced empirical methods that set the foundation for later scientific inquiry.

He refined π values (near 3.1416), supported the spherical nature of the Moon, and explained lunar eclipses via Earth’s shadow—recognizing that lunar light stems from reflected sunlight.

Zhang invented the world’s first seismoscope in AD 132—a bronze instrument whose pendulum mechanism could detect and indicate the direction of distant earthquakes. He also crafted a water-driven armillary sphere to model heavenly motions, anticipating later mechanical astronomical devices.

In addition, Zhang compiled a stellar catalog of approximately 2,500 stars and improved measurements of equinoxes and solstices. As a poet, he elegantly fused scientific insight with lyrical expression, illustrating how art and observation can coalesce.

Legacy

Zhang Heng’s inventions and observations were pioneering—seismology’s roots trace back to his device, and his mechanical models advanced astronomical technology. A true Renaissance figure, he exemplified the integration of scientific precision and poetic vision in ancient China.