Science & Discovery in the 3rd century BC

8 sourced entries, 285 BCE to 200 BCE, oldest first. Also see Science & Discovery across every century or everything else in the 3rd century BC.

• 285 BCEA 110 metre tall lighthouse on the island of Pharos in Alexandria's harbour is completed and serves as a landmark for ships in the eastern Mediterranean. Built by Sostratus of Cnidus for Ptolemy II of Egypt, it is one of the seven wonders of the ancient world. It is a technological triumph and is the archetype of all lighthouses since. A broad spiral ramp leads to the top, where a fire burns at night.source
• 280 BCEAristarchus of Samos uses the size of the Earth's shadow on the Moon to estimate that the Moon's radius is one-third that of the Earth. He proposes, for the first time, a heliocentric view of the Solar System, but is ignored due to the lack of evidence of the Earth's motion.source
• 265 BCEThe Archimedes screw for raising water is devised by the Greek mathematician Archimedes, who is studying at Alexandria.source
• 245 BCEApproximate date – Callimachus produces the Pinakes, a subject index to the Library of Alexandria.source
• 240 BCEMay 25 – Chinese astronomers make the first recorded observation of Halley's Comet.source
• 240 BCEThe Hellenistic period Mathematician Eratosthenes estimates the Earth's circumference to be 252,000 stadia, a figure between 2%-20% off modern measurements.source
• 239 BCEQin Prime Minister Lü Buwei publishes the "Spring and Autumn Annals of Lü Buwei" (Lüshi Chunqiu).source
• 200 BCEThe first good measurement of the distance between Earth and the Sun is made by Eratosthenes (approximate date). By studying lunar eclipses, his result is roughly 150 000 000 km. The currently accepted value is 149 597 870 691 ± 30 metres.source