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PTOLEMY

b. about 100 A. D. and d. about 161

Greek astronomer, geographer and mathematician. He maintained that the earth was a sphere and that the sun and stars revolve daily around the earth, which is fixed in the centre of the universe. His astronomical theory is called the Ptolemaic system. He wrote a work on general geography, which for ages was the chief authority on that subject and did not become obsolete until the fifteenth century. He gave special attention to the determination of the latitudes and longitudes of places by mathematical process, but neglected the descriptive part of geography.

Reas’ning at every step he treads,
Man yet mistakes his way,
While meaner things, whom instinct leads,
Are rarely known to stray.

—Cowper

1008—Junis Ebn made astronomical tables.

1473, January 19-1543, May 24—Nicholas Copernicus lived. 1517, he discovered the true system of the universe. He completely overthrew the Ptolemaic theory of the universe. His great work is entitled “De Revolutionbus Orbium Cælestium.

1790—An immense stone was found in Mexico engraved with the astronomical cycle of the Aztecs.

1801, January 1—Karl F. Gauss invented his method of calculating the position of heavenly bodies, enabling astronomers to relocate lost planets.

1838—Herschel’s Outline of Astronomy was published.