_ THE _2 _ 2007 V10 B

_ THE _2 _ 2007 V10 B - TAKE-HOME EXP 2 A Calculation of...

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TAKE-HOME EXP. # 2 A Calculation of the Circumference and Radius of the Earth On two dates during the year, the geometric relationship of Earth to the Sun produces "equinox", a word literally meaning, "equal night" or equal durations for night and day. The Fall equinox occurs approximately Sept. 21, and the Spring equinox, approximately March 21. On these two days, every year: a) The time between sunrise and sunset is approximately 12 hours everywhere on Earth. b) The Sun is directly overhead at noon at the equator. As a consequence, the shadow- terminator line is parallel to a line of longitude, and, therefore, the shadow of Earth bisects each polar region. March 21 and September 21 This experiment will use the second fact to directly measure your latitude angle. And, as a consequence, you can directly produce the actual circumference and radius of the Earth! The circumference and radius of Earth helps to locate human beings within the context of a universe of galaxies. A. A Procedure To Find The Circumference Of The Earth This procedure was first used by Eratosthenes, who headed the great Museum at Alexandria (or Cairo) in Egypt, around 200 BC Most of the ancient observers were completely convinced of the roundness of Earth. The evidence was clear. Lunar eclipses were correctly interpreted as showing the circular shadow of the Earth. Also, if one traveled north, the northern constellations got higher in the sky, and the southern ones dropped toward the horizon. A similar effect occurred for southward travel, with the south constellations getting higher in the sky, and even some new constellations, not seen from the northern hemisphere would be visible.
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TAKE-HOME EXPERIMENT #2 T.H.E. #2-2 _________________________________________ With that background, Eratosthenes also had some additional local information. On the summer solstice date, Eratosthenes knew that the Sun illuminated the bottom of a very deep well at Syene, about 500 miles directly south of the Museum at Alexandria. In order to reach the bottom of such a narrow, deep shaft, the Sun at Aswan must have been nearly directly overhead at noon. If a stick had been oriented vertically at Aswan on that date, it would have cast no shadow at noon on that day. Note on the map that Syene (Aswan) is just a short distance north of the 23.5˚ N latitude line, the Tropic of Cancer, which is the farthest north latitude at which the Sun can be directly overhead. That occurs there about June 21, the solstice date. The Use of a Vertical Stick Called a “Gnomon”. The use of a vertical stick perpendicular to a flat surface can tell one a great deal about the time of day and the time of year. The ancient Greek word for this device was "gnomon", and it has been directly taken over into English. It should be found in any "collegiate" dictionary.
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This note was uploaded on 04/24/2010 for the course ANTH 7173 taught by Professor George during the Spring '10 term at CSU Long Beach.

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_ THE _2 _ 2007 V10 B - TAKE-HOME EXP 2 A Calculation of...

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