EratosthenesEratosthenes

His LifeHis Life

Eratosthenes was born in Cyrene. (in Eratosthenes was born in Cyrene. (in modern-day Libya). He was the third chief modern-day Libya). He was the third chief librarian of the Great Library of Alexandria, librarian of the Great Library of Alexandria, the center of science and learning in the the center of science and learning in the ancient world, and died in the capital of ancient world, and died in the capital of Ptolemaic Egypt.Ptolemaic Egypt.

Eratosthenes studied in Alexandria, and claimed Eratosthenes studied in Alexandria, and claimed to have also studied for some years in Athens. In to have also studied for some years in Athens. In 236 BC he was appointed by Ptolemy III 236 BC he was appointed by Ptolemy III Euergetes I as librarian of the Alexandrian library, Euergetes I as librarian of the Alexandrian library, succeeding the second librarian, Apollonius of succeeding the second librarian, Apollonius of Rhodes, in that post.[7] He made several Rhodes, in that post.[7] He made several important contributions to mathematics and important contributions to mathematics and science, and was a good friend to Archimedes. science, and was a good friend to Archimedes. Around 255 BC he invented the armillary sphere. Around 255 BC he invented the armillary sphere. In In On the Circular Motions of the Celestial On the Circular Motions of the Celestial BodiesBodies, Cleomedes credited him with having , Cleomedes credited him with having calculated the Earth's circumference around calculated the Earth's circumference around 240 BC, using knowledge of the angle of 240 BC, using knowledge of the angle of elevation of the sun at noon on the summer elevation of the sun at noon on the summer solstice in Alexandria and on Elephantine Island solstice in Alexandria and on Elephantine Island near Syene (now Aswan, Egypt).near Syene (now Aswan, Egypt).

Eratosthenes criticized Eratosthenes criticized Aristotle for arguing Aristotle for arguing that humanity was that humanity was divided into Greeks divided into Greeks and barbarians, and and barbarians, and that the Greeks should that the Greeks should keep themselves keep themselves racially pure, believing racially pure, believing there was good and there was good and bad in every nation.[8] bad in every nation.[8] By 195 B.C., By 195 B.C., Eratosthenes became Eratosthenes became blind. He died in 194 blind. He died in 194 B.C., at the age of 82.B.C., at the age of 82.

His AchiementsHis Achiements

Measurement of Measurement of the Earth's the Earth's circumference.circumference.

Eratosthenes Eratosthenes calculated the calculated the circumference of circumference of the Earth without the Earth without leaving Egypt. leaving Egypt.

Prime numbersPrime numbers

Main article: Sieve of EratosthenesMain article: Sieve of Eratosthenes Eratosthenes also proposed a simple Eratosthenes also proposed a simple

algorithm for finding prime numbers. This algorithm for finding prime numbers. This algorithm is known in mathematics as the algorithm is known in mathematics as the Sieve of Eratosthenes.Sieve of Eratosthenes.

Achievement in astronomyAchievement in astronomy

o Eratosthenes measured the angle of the Eratosthenes measured the angle of the shadow to the Earth.shadow to the Earth.

o Eratosthenes believed that the sun was Eratosthenes believed that the sun was so far away that its rays were parallel. so far away that its rays were parallel.

o It is also believed that Eratosthenes made It is also believed that Eratosthenes made a star catalog with approximately 675 stars a star catalog with approximately 675 stars and created a calendar that included leap and created a calendar that included leap years. years.

Achievements in HistoryAchievements in History

He decided to work on giving a systematic He decided to work on giving a systematic chronography of the known world by chronography of the known world by figuring out the dates of literary and figuring out the dates of literary and political events from the siege of Troy up political events from the siege of Troy up until his time. However, this was only a until his time. However, this was only a beginning. Others built on his foundation. beginning. Others built on his foundation.

Achievements in GeographyAchievements in Geography

Eratosthenes also Eratosthenes also contributed to contributed to geographic source geographic source of the river. of the river.

Many scholars that preceded Eratosthenes Many scholars that preceded Eratosthenes in the study of the Nile river, tried to figure in the study of the Nile river, tried to figure out the reason why parts of the river flooded out the reason why parts of the river flooded while other parts did not. It was not until while other parts did not. It was not until Eratosthenes that a correct answer was Eratosthenes that a correct answer was proposed.proposed.

He believed that heavy rains near the He believed that heavy rains near the source of the Nile was the cause of Many of source of the Nile was the cause of Many of Eratosthenes' peers nicknamed him "Beta" Eratosthenes' peers nicknamed him "Beta" which is the second letter of the Greek which is the second letter of the Greek alphabet, indicating that he just fell short of alphabet, indicating that he just fell short of first place.first place.

Eratosthenes contributed greatly to many Eratosthenes contributed greatly to many different areas of knowledge, more than I could different areas of knowledge, more than I could cover in this short paper. Maybe in his time cover in this short paper. Maybe in his time period, his peers did not feel that he contributed period, his peers did not feel that he contributed enough in one area or maybe they were jealous enough in one area or maybe they were jealous that he had contributed so much to so many that he had contributed so much to so many areas. areas.

For a man who was nicknamed Beta, it is pretty For a man who was nicknamed Beta, it is pretty impressive that so much of his work in these impressive that so much of his work in these areas is still discussed today, so many years areas is still discussed today, so many years later.later.

His death & ReasonsHis death & Reasons

""On the Murder of EratosthenesOn the Murder of Eratosthenes" is a " is a speech by Lysias, one of the "Canon of speech by Lysias, one of the "Canon of Ten" Attic orators (Speech 1 in Lamb's Ten" Attic orators (Speech 1 in Lamb's translation, ISBN 978-0-674-99269-6). The translation, ISBN 978-0-674-99269-6). The speech is a defense written for Euphiletos speech is a defense written for Euphiletos who is charged with the death of who is charged with the death of Eratosthenes. The case is heard before Eratosthenes. The case is heard before the Delphinion, a court which hears the Delphinion, a court which hears proceedings for justifiable homicideproceedings for justifiable homicide

Euphiletos is accused Euphiletos is accused of killing Eratosthenes, of killing Eratosthenes, who was caught in the who was caught in the act of adultery with act of adultery with Euphiletos's wife. Euphiletos's wife. Euphiletos's defense is Euphiletos's defense is that his killing of that his killing of Eratosthenes was an Eratosthenes was an act of justifiable act of justifiable homicide and therefore homicide and therefore not punishable.not punishable.

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