Picture of Ptolemy
The Bettmann Archive
Ptolemy was a Greek astronomer who lived between 85-165 A.D. He put together his own ideas, those of Aristotle, and Hipparchus' system of epicycles and eccentric circles, to formulate the geocentric theory. Ptolemy believed that the Earth was at the center of the universe and all other heavenly bodies circled it. This Ptolemaic System was accepted for the next 1,500 years until Copernicus' heliocentric theory.
Ptolemy is also famous for his work in geography. He was the first person to use longitude and latitude lines to identify places on the face of the Earth, and developed three methods for projections in mapmaking.
Shop Windows to the Universe Science Store!
Our online store
on science education, classroom activities in The Earth Scientist
specimens, and educational games
You might also be interested in:
How did life evolve on Earth? The answer to this question can help us understand our past and prepare for our future. Although evolution provides credible and reliable answers, polls show that many people turn away from science, seeking other explanations with which they are more comfortable....more
Aristotle was a Greek philosopher who lived between 384-322 B.C. He was one of the greatest thinkers of the world and his written works encompassed all major areas of thought: logic, science, metaphysics,...more
Nicholas Copernicus was a Polish astronomer who lived between 1473-1543. He was born in Torun, Poland to a middle class family. He attended school at Cracow and eventually moved on to Italy where he received...more
Tycho Brahe was a Danish astronomer who lived between 1546-1601. Although Tycho had his own model of the solar system, which differed from both the heliocentric and geocentric theories, his contributions...more
Galileo Galilei was an Italian astronomer and physicist who lived between 1564-1642. He challenged Aristotle's ancient proposition that heavenly bodies were divine and therefore perfect and blemish-free....more
Archimedes was a Greek mathematician and engineer who lived between 287-212 B.C. His greatest contributions are in the field of geometry, where he identified the relationship of a sphere and cylinder's...more
Democritus was a Greek philosopher who lived between 470-380 B.C. He developed the concept of the 'atom', Greek for 'indivisible'. Democritus believed that everything in the universe was composed of atoms,...more
Eratosthenes was an ancient Greek astronomer, geographer, and mathematician. He lived from 276 to 194 B.C. Eratosthenes is most famous for making the first accurate measurement of the circumference of...more