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Of Samos preferred the "Heliocentric" model with the Sun at the The Geocentric model of Aristotle could not To the Terrestrial Realm in the upper Earth's atmosphere. Objects like meteors or comets must belong Also celestial objects were incorruptible. It was called Aether and had the property of glowing without Likewise in the Terrestrial Realm everything was corruptible (changing).Īre different in the Celestial Realm. Opposing the natural tendency (violent motion) required force. Objects that followed their natural tendencies Earth and water tended to sink, while air and fire tended to rise. Elements had natural tendencies of motion. In the Terrestrial Realm motion could be predicted only when theĬomposition of the object was known. Shifting of a star position that must occur if the Earth orbits the Sun)ĭivided the universe into two realms. The Earth was the stationary, center of the Universe. Other measurements of the Moon at critical times in its orbit, the Greeks wereĪble to obtain the relative distance and sizes of the Earth, Moon, andĬompared to the Earth and the Moon, but that the Earth was larger than theįact that the angular sizes of the Moon and the Sun are almost exactly theĪdvances lead to the first comprehensive models of the universe. Erastosthenes measured that the Sun was 7.5 degrees South of theĭifference of the Sun in the two cities is about 1/50 th theĭistance between the two cities must be 1/50 th the circumference of The Sun in the sky at Alexandria at the same moment. That said, "At noon on the summer solstice, we can see the bottom of a Library in Alexandria, came across a note from the far southern city of Syene We now know the shape of the Earth, can we measure the size of the Earth. The only shape that can only cast a circular shadow is the sphere. The Babylonians recorded many lunarĮclipses, but all were sections of a circle. Produces the lunar eclipse, we can judge the shape of the Earth. Phases and eclipse are understood, the Greeks can take the next logical How much of the sunlit portion do we see from the Earth. Of the Moon are seen to be simply geometry - as the Moon goes around the Earth, Simple model relies on two changes in the basic assumptions:Īt least the Sun has to be farther away than the Moon Is between the Sun and the Moon and the shadow of the Earth can fall onto the Possible for the shadow of the Moon to be cast onto the Earth, producing a At New Moon the moon is between the Earth and the Sun and it is This model had to change the basic assumptions about theĪre just shadows cast from one body onto another. Were very good sky observers but their ability to build models of the universeĪsking why things happened the way they did, a question that would never haveĮarly model predicted lunar phases and eclipses.