Eratosthenes of Cyrene
Eratosthenes of Cyrene was an astronomer and for a time was the director of the Bibliotheca Alexandrina . One of his greatest achievements, in fact, the achievement by which he attributes his current celebrity was to measure the circumference of the globe around the year 250 A. c.
Eratosthenes One day a papyrus found in the Library of Alexandria where he could read in a place called Siena (now Aswan ) the sun's rays fell to lead the summer solstice day, which had been found because the person who wrote on papyrus pointed to a deep well in which water could see the sun fully reflected and that the objects cast no shadow. This will astound Eratosthenes, and that he remembered in Alexandria the summer solstice day objects, columns and so on if they planned to shadow. For most of us the mere finding of a papyrus which document the perplexity of a man with a fact that we give and by daily and not pay attention to what would have gone unnoticed, but thank God or Allah or whoever, in history have been men and women who have left to question why things happen and have not tired despite not find the answers, because they trusted their instincts and they were sure that would seat the foundation for future knowledge.
Well, but what I was saying, Eratosthenes surprised by this fact hired a man to take a walk the distance between Alexandria and Siena. Distance in current units proved to be of 840 kilometers, though it really was measured at Stadiums (1 stage = 152.7 meters).
At that time already knew or suspected that the earth was round so without thinking twice thinking geometrically Eratosthenes concluded: if the sun's rays directly affect Siena, but in Alexandria makes an angle with the vertical, this angle is equal to the vertical form of the two cities whether to lengthen the center of the Earth, ie it is equal to the difference geographic latitude between Siena and Alexandria. Call this angle A.
angle A, as found Eratosthenes, was about 7.5 °. With this interesting information in hand, Eratosthenes is said angle A (7.5 °) is the forty-eighth (48 part) of a complete circle (360 °), therefore, the distance between Alexandria and Syene must be in proportion to the circumference of the Earth, that is:
Where:
(360 ° / A) x distance = circumference Alexandria Earth Siena
words:
(360 / 7.5) x 840 km = Earth's circumference
Eratosthenes One day a papyrus found in the Library of Alexandria where he could read in a place called Siena (now Aswan ) the sun's rays fell to lead the summer solstice day, which had been found because the person who wrote on papyrus pointed to a deep well in which water could see the sun fully reflected and that the objects cast no shadow. This will astound Eratosthenes, and that he remembered in Alexandria the summer solstice day objects, columns and so on if they planned to shadow. For most of us the mere finding of a papyrus which document the perplexity of a man with a fact that we give and by daily and not pay attention to what would have gone unnoticed, but thank God or Allah or whoever, in history have been men and women who have left to question why things happen and have not tired despite not find the answers, because they trusted their instincts and they were sure that would seat the foundation for future knowledge.
Well, but what I was saying, Eratosthenes surprised by this fact hired a man to take a walk the distance between Alexandria and Siena. Distance in current units proved to be of 840 kilometers, though it really was measured at Stadiums (1 stage = 152.7 meters).
At that time already knew or suspected that the earth was round so without thinking twice thinking geometrically Eratosthenes concluded: if the sun's rays directly affect Siena, but in Alexandria makes an angle with the vertical, this angle is equal to the vertical form of the two cities whether to lengthen the center of the Earth, ie it is equal to the difference geographic latitude between Siena and Alexandria. Call this angle A.
angle A, as found Eratosthenes, was about 7.5 °. With this interesting information in hand, Eratosthenes is said angle A (7.5 °) is the forty-eighth (48 part) of a complete circle (360 °), therefore, the distance between Alexandria and Syene must be in proportion to the circumference of the Earth, that is:
360 ° (full circle) = Circumference Earth
________________ _________________
Alexandria-Siena Distance
________________ _________________
Alexandria-Siena Distance
Where:
(360 ° / A) x distance = circumference Alexandria Earth Siena
words:
(360 / 7.5) x 840 km = Earth's circumference
Therefore, the Earth's circumference = 40,320 miles or so.
And lo, my dear children how a man's insatiable curiosity for quite some jug of years calculated with a precision almost inconceivable, with simple logic and overwhelming the circumference of the earth with a minimum error rate, as demonstrated with our ultra modern instruments today.
And even though I often complain of this world, our leaders, of all that I think is unfair to suddenly see a ' Eratosthenes "and I do still believe in amazing and surprising that the human race. Him if he did something incredible, not how Obama.
Sources:
The method of Eratosthenes to measure the circumference of the Earth Eratosthenes
And lo, my dear children how a man's insatiable curiosity for quite some jug of years calculated with a precision almost inconceivable, with simple logic and overwhelming the circumference of the earth with a minimum error rate, as demonstrated with our ultra modern instruments today.
And even though I often complain of this world, our leaders, of all that I think is unfair to suddenly see a ' Eratosthenes "and I do still believe in amazing and surprising that the human race. Him if he did something incredible, not how Obama.
Sources:
The method of Eratosthenes to measure the circumference of the Earth Eratosthenes
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