Eratosthenes

1. Eratosthenes ALEXANDRIAN MATHEMATICIAN AND GEOGRAPHER (276-194 B.C.)

2. ABOUT ERATOSTHENES Eratosthenes was born in Cyrene (NOW LIBYA) in the year 276 B.C. Eratosthenes was a GREEK mathematician, GEOGRAPHER AND ASTRONOMER. He was the third chief librarian of the Great Library of Alexandria, the centre of science and learning in the ancient world. ERATOSTHENES IS KNOWN AS THE ‘FATHER OF GEOGRAPHY’. HE DIED IN THE CAPITAL OF PTOLEMAIC EGYPT IN 194 B.C. AT THE AGE OF 82.

3. He is best known for being the first person to calculate the  circumference of the earth He was nicknamed “Beta” by his contemporaries due to the fact that he proved to be second best at almost anything- beta is the second letter in the Greek alphabet.  Eratosthenes was the founder of scientific  chronology ABOUT ERATOSTHENES

4. HIS STUDIES Eratosthenes went to Athens to further his studies. There he was taught  Stoicism   by its founder,  Zeno of Citium , in philosophical lectures on living a virtuous life . He then studied under  Ariston of Chios , who led a more cynical school of philosophy .  He also studied under the head of the Platonic Academy, who was  Arcesilaus of Pitane . His interest in Plato led him to write his very first work at a scholarly level,  Platonikos , inquiring into the mathematical foundation of Plato's philosophies.

5. In 236 BC he was appointed by Ptolemy III Euergetes I as librarian of the Alexandrian library, succeeding the second librarian, Apollonius of Rhodes, in that post . He made several important contributions to mathematics and science, and was a good friend to Archimedes. Around 255 BC he invented the armillary sphere . Eratosthenes criticized Aristotle for arguing that humanity was divided into Greeks and barbarians, and that the Greeks should keep themselves racially pure, believing there was good and bad in every nation . By 195 B.C., Eratosthenes became blind.  He died in 194 B.C., at the age of 82.

6. HIS ACHIVEMENTS HE SUCCESFULLY CALCULATED THE CIRCUMFERENCE OF THE EARTH without leaving Egypt . He also was able to calculate the tilt of Earth’s axis with remarkable accuracy. Another accomplishment of Eratosthenes was his calculation of Earth’s distance from the sun AND MOON. Eratosthenes also invented the leap day, which adds an extra day onto a year, in order to make sure the calendar keep stay on track with the sun.

7. PRIME NUMBERS Main article: Sieve of Eratosthenes Eratosthenes also proposed a simple algorithm for finding prime numbers. This algorithm is known in mathematics as the Sieve of Eratosthenes.

8. Achievement in astronomy Eratosthenes measured the angle of the shadow to the Earth . Eratosthenes believed that the sun was so far away that its rays were parallel . It is also believed that Eratosthenes made a star catalogue with approximately 675 stars and created a calendar that included leap years.

9. ACHIVEMENT IN HISTORY He decided to work on giving a systematic chronography of the known world by figuring out the dates of literary and political events from the siege of Troy up until his time. 

10. Achievements in Geography Eratosthenes also contributed to geographic source of the river . Many scholars that preceded Eratosthenes in the study of the Nile river, tried to figure out the reason why parts of the river flooded while other parts did not. It was not until Eratosthenes that a correct answer was proposed . He believed that heavy rains near the source of the Nile was the cause of Many of Eratosthenes peers nicknamed him "Beta" which is the second letter of the Greek alphabet, indicating that he just fell short of first place.

11. ERATOSTHENES IS IDENTIFIED AS THE “ FATHER OF GEOGRAPHY ” BECAUSE AMONG OTHER CONTRIBUTIONS, HE WAS THE FIRST TO COIN THE TERM “ GEOGRAPHY ”. HE ALSO TRIED TO DIVIDE THE EARTH INTO VARIOUS HEAT BELTS, AND INTRODUCED THE TERMS LIKE “TORRID”, “FRIGID” AND “TEMPERATE” TO GEOGRAPHY. HE PRODUCED A BOOK ON THE HABITABLE PART OR THE EKUMENE OF THE EARTH. HE USED TWO TERMS i.e., LATITUDES AND LONGITUDES TO LOCATE PLACES AND TO MEASURE DISTANCES.

12. HIS DEATH As he aged he contracted ophthalmia, becoming blind around 195 BC. Losing the ability to read and to observe nature plagued and depressed him, leading him to voluntarily starve himself to death. He died in 194 BC at the age of 82 in his beloved Alexandria.

13. references http://en.wikipedia.org/wiki/Eratosthenes http://astroverada.com/earth/stadia.html

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