Greek cities were set up throughout the Hellenistic world under Graeco-Macedonian dynasties which encouraged technological innovations and the development of science. The cities of Alexandria in Egypt and Pergamum became the centres for these activities.
New advances were made in mathematics, astronomy, biology, medicine and engineering. Royal patrons provided excellent research facilities like libraries and museums for their scientists. Although most scientists were Greek, they benefited from the cross-fertilization of cultures that was an important feature of the Hellenistic Age.
The most famous of these scientists included Eratosthenes of Cyrene, who calculated the earth's circumference by means of geometry and drew a map of the world, and Aristarchus of Samos, who wrote a treatise on the relation of the sun and the moon to the earth and theorized that the sun was at the centre of the universe.
Archimedes of Syracuse calculated the value of pi, invented the Archimedean screw which is still used to raise water for irrigation and discovered the principle of water displacement used to calculate volume (the 'eureka' story).
Herophilis of Calchedon headed a medical school in Alexandria and researched the eye, brain, liver and reproductive organs. Erasistratus of Ceos, another medic, investigated the digestive and vascular systems. It is thought that both Herophilis and Erasistratus practised surgery and other experiments on living humans who were selected from the prisons of Alexandria.
