What was Ptolemy's theroy about the structure of the earth?

Answer 1

I note several posters addressing Ptolemy's earth-centric view of the cosmos rather than addressing the original poster's question about Ptolemy's thoughts on the structure of the earth (*structure*, not orbit, folks), about which next to nothing is known.

Of the things we know, Ptolemy was definitely NOT a member of the Flat Earth Society. Find in the next link one of his maps of the "known world". Observe the recognition of the spheriod shape.

http://geology.cwru.edu/~huwig/catalog/slides/769.G.2.jpg

He wrote three main works -- one on astronomy and geometry, one on astrology, and finally, his 8 volume work on geography.

From the latter, we know that like the other Greeks and Romans of his time, he understood that the Earth was round, and discussed at some length the problem of portraying it on a flat piece of paper (see his map, above). In addition, Ptolemy took a crack at it, but made a fairly serious underestimation of the Earth's circumference.

Apart from those basic things having to do with its surface, I am not aware of ANY information that would shed light on how Ptolemy viewed the *structure* of the Earth (what it looks like *below* the surface). If anyone is able to shed light on the original topic, I'll be as interested as the O.P. to hear more about it.

Answer 2

Hi. Your question was about the Earth's structure at the time of Ptolemy. I would think that he viewed it as flat, or at least bounded.

Edit. Some of your answers suggest to me that I could be wrong. Hey, it happens!

Answer 3

Ptolemy formulated a geocentric model that was widely accepted until it was superseded by the heliocentric solar system of Copernicus. Likewise his computational methods (supplemented in the 12th century with the Arabic computational Tables of Toledo) were of sufficient accuracy to satisfy the needs of astronomers, astrologers and navigators, until the time of the great explorationS.

Answer 4

Ptolemy (aka Claudius Ptolemaeus, Ptolomaeus, Klaudios Ptolemaios, Ptolemeus) lived in Alexandria (in Egypt) from approx. 87 -150 AD. Very little is known about his personal life (the image above is probably purely the artist's imagination)

He was an astronomer, mathematician and geographer. He codified the Greek geocentric view of the universe, and rationalized the apparent motions of the planets as they were known in his time.

Ptolemy synthesized and extended Hipparchus's system of epicycles and eccentric circles to explain his geocentric theory of the solar system. Ptolemy's system involved at least 80 epicycles to explain the motions of the Sun, the Moon, and the five planets known in his time. He believed the planets and sun to orbit the Earth in the order Mercury, Venus, Sun, Mars, Jupiter, Saturn . This system became known as the Ptolemaic system. It predicts the positions of the planets accurately enough for naked-eye observations This is described in the book Mathematical Syntaxis (widely called the Almagest), a thirteen book mathematical treatment of the phenomena of astronomy. It contains a myriad of information ranging from earth conceptions to sun, moon, and star movement as well as eclipses and a breakdown on the length of months. The Almagest also included a star catalog containing 48 constellations, using the names we still use today.


In addition to his well known works in astronomy, Ptolemy was very important in the history of geography and cartography. Ptolemy of course knew that the Earth is a sphere. Ptolemy's is the first known projection of the sphere onto a plane. His Geography remained the principal work on the subject until the time of Columbus. But he had Asia extending much too far east, which may have been a factor in Columbus's decision to sail west for the Indies.


The Ptolemaic explanation of the motions of the planets remained the accepted wisdom until the Polish scholar Copernicus proposed a heliocentric view in 1543. It should be noted, too, that Ptolemy's system is actually more accurate than Copernicus's. The heliocentric formulation does not improve on Ptolemy's until Kepler's Laws are also added.


It is doubtful that Ptolemy actually believed in the reality of his system. He may have thought of it only as a method of calculating positions.

Ptolemy also wrote Tetrabiblos, a work on astrology. (In those days, astrology was a reputable field of study.)

[Note: There were also a number of Egyptian rulers known as Ptolemy who ruled Egypt from 323BC to 30BC. Though he lived in Egypt, our Ptolemy was a Greek.]



Links

a quick bio from IMSS, Firenze
nice page from University of St. Andrews, Scotland
Greek Astronomy, from the Vatican Exhibit; including images of Ptolemy's Almagest and Geography
Ptolemy's Geography, from the Vatican Exhibit; including Handy Tables
another map from a 15th century translation of Ptolemy's Geography; (another version)
Ptolemy's Geography as a GIS
History and Philosophy of Western Astronomy has a short section on Ptolemy and his predecessors.
bibliography
Ptolemy and Geography
Documents of Astronomical History, including an excerpt from Almagest
machine readable version of the star catalogue in the Almagest

Answer 5

have you ever made ice cubes in an ice cube tray? if so, you will word that they freeze on the exterior first with a liquid interior before freezing fullyyt. Likewise, the Earth began as liquid rock and has purely "frozen" on the exterior. in case you think of a extensive ball (like a sea coast ball) the exterior layer is the solid "crust" yet each and every of the interior is liquid rock "magma." the solid crust is made up of things referred to as tectonic plates. those plates drift around on suited of the magma. while they crash it is referred to as an earthquake. while a hollow interior the crust breaks open and magma comes out it is referred to as a volcano and the magma is termed lava. we've in no way sent a probe into the interior the Earth.