The World Is a Pear - Don't Know Much About Geography - page 20

c. 530 Pythagoras, a mathematician and mystic, is active in Samos. The Pythagoreans teach that
the earth is a sphere and not in the shape of a disk. The first recorded description of the earth as a
sphere, by Plato, quoting Socrates, comes in 380 BC. One of the later members of the Pythagorean
school suggests there is a central fire around which the earth, sun, moon, and planets revolve; he
also believes the earth rotates.
c. 500 Greek historian Hecataeus develops a map of the world showing Europe and Asia as semi-
circles surrounded by ocean.
c. 480 Greek philosopher Oenopides is supposedly the first to calculate the angle at which the earth
is tipped. His value of 24 degrees is only half a degree from the presently accepted value of about
23.5 degrees.
5th century BC Chinese astronomers begin continuous star observations.
c. 390 Plato conceives the idea that there must be a continent directly opposite Europe, on the other
side of the globe, which he calls the Antipodes.
334 Alexander of Macedon invades Asia Minor; conquers Egypt (332) and Persia (330); reaches
India (329); dies in Babylon (323).
c. 310-230 Aristarchus postulates that the earth revolves around the sun, according to Archimedes.
c. 300 Chinese writings contain the first reference to a lodestone's magnetic alignment; it is called a
“south pointer.”
c. 240 Eratosthenes calculates the circumference of the earth with near accuracy.
221 Shi Huang Ti, of the Ch'in dynasty, unites China, and the construction of the Great Wall begins
in 214.
c. 190-120 Hipparchus, a Greek astronomer, is the first to use latitude and longitude.
c. 138 During the Han dynasty, Chang Ch'ien is sent as an ambassador to explore Central Asia in
search of allies to help fight the Huns. In his years of travel, he reaches Afghanistan and later as far
as Syria and possibly Egypt.
c. 112 Opening of the Silk Road across Central Asia; it becomes the route on which Chinese and
European goods are exchanged, although no Europeans would see China for centuries to come.
c. 64- 21 Strabo, influential Greek traveler and geographer.
Anno Domini
23-79 Pliny the Elder, a Roman scholar, whose Natural History was a widely accepted source.
Careless in his research, Pliny passes along fabulous tales and legends for popular consumption. He
died observing an eruption of Mount Vesuvius.