230 BC – 220 BCs

Events in 230 BC – 220 BC 3

• 225 BC Quadrature of the Parabola The area under a parabola — anticipating integral calculus In Quadrature of the Parabola, Archimedes proved that the area enclosed by a parabola and a straight line is exactly 4/3 the area of the inscribed triangle. He proved this using both a mechanical method (balancing on a lever) and a rigorous method of exhaustion. The result anticipates the fundamental theorem of integral calculus by nearly 2,000 years. Newton and Leibniz both acknowledged the influence of Archimedes's method of exhaustion on their invention of calculus.
• 221 BC – 206 BC Qin Dynasty — First unified China Qin Shi Huang unifies the warring states In 221 BC, Ying Zheng of the state of Qin conquered the last of the warring states and proclaimed himself Qin Shi Huang — First Emperor of China. He standardised weights, measures, currency, axle widths and writing across the empire, creating the template for Chinese civilisation. His dynasty lasted only 15 years but its legacy shaped China for two millennia. The name "China" derives from "Qin".
• 221 BC – 210 BC Qin Shi Huang — First Emperor of China 221–210 BC — unifier, tyrant, visionary Ying Zheng became king of Qin at age 13 and conquered all rival states by 221 BC, aged 38. As First Emperor he standardised writing, currency, weights and measures across China, built the first Great Wall, and connected the empire with roads and canals. He also burned books and buried scholars alive to suppress dissent. He spent his final years obsessively seeking immortality. His terracotta army of 8,000 warriors was discovered in 1974.