The Copernican response to the Ptolemaic model of the universe

Of all the scientific disciplines Astronomy stands out as the all-encompassing one in that all the other sciences grew out of astronomy and are still influenced by it . From its early history the astronomic novelties had always been based on the predecessors discoveries which first found support among successors but then usually induced revolutionary new discoveries . This research presents a of two models of universe proposed by great astronomers who made considerable contributions into the development of the science and astronomy in particular

Claudius Ptolemaus (Ptolemy (AD 100-170 ) was probably born

in Greece but his Latin name indicated that he possessed Roman citizenship . His earliest celestial observations are dated AD 127 and his stellar catalogue is dated AD 137 . Hipparchus ' stellar astronomy was highly accurate and it greatly influenced the astronomers who followed him particularly Ptolemy , who , in his The Almagest (also known as The Great Syntax ) gave a detailed record of Hipparchus and his achievements Ptolemy records that Hipparchus accurately determined the positions relative to the vernal equinox and the ecliptic (celestial latitudes and longitudes ) of 1080 stars and classified their brightness . This is the first example in astronomical history of a star catalogue

In his The Almagest , Ptolemy examined and commented on every problem in astronomy that had challenged his predecessors . But the principal problem that concerned him was the explanation of the motions of the planets . In this area of his work he accepted the concept of epicycles as proposed by Hipparchus (Sambursky , 139 , but improved on Hipparchus work by developing a very elegant epicycle model of the motions of Venus and Mercury . Ptolemy had to explain why the apparent motions of Mercury and Venus differ drastically from the apparent motions of Mars , Jupiter and Saturn

It is sufficient to consider the apparent motion of Venus alone to understand the problem that confronted both Hipparchus and Ptolemy and how Ptolemy solved it using special epicycles . Venus always appears to be near the sun , either to its left or right , but never straying more than 48 degrees on one side or the other , shifting its position from one side to the other periodically as though it were to the sun When Venus is to the right (to the west ) of the sun , it rises early in the morning , before the sun rises . Venus is then called the Morning Star . The early Greeks called it Phosphorus . It then sets before the sun sets . When Venus is to the left of the sun (east of the sun , it is visible in the early evening and sets after the sun does . Called Hesperus by the early Greeks , we now call it the Evening Star Pythagoras was probably the first to discover that Hesperus and Phosphorus are the same planet , which was named Venus by the Romans (Hawkins , 44

Unlike the planets Mars , Jupiter , and Saturn which rise and set at all times of day without regard to the sun , the rising and setting of Venus and Mercury closely...