Eratosthenes

 

by

Sara Rullán

Gulf Coast Community College
April 2000

 

Throughout the history of mankind there have only been a handful of people whose extraordinary contributions have been crucial to the development of our society.  One such pillar of history is Eratosthenes, whose name is revered by even the most renowned scholarly minds of our time.  Although Eratosthenes is most commonly known for his mathematical accomplishments, he is also celebrated for his achievements in geography, astronomy, history, philosophy, and even poetry. Eratosthenes was born around 276 B.C. in the Greek colony of Cyrene.

Eratosthenes was given two nicknames that are significant in light of the prodigious range of his interests.  In honor of his varied accomplishments, his friend called him Pentathis, a name applied to the champion in five athletic events-hence, to men who tried their hands at everything.  His detractors felt that in attempting too many specialties, Eratosthenes failed to surpass his contemporaries in any one of them.  They dubbed him Beta (the second letter in the Greek alphabet), insinuating that while Erastothenes stood at least second in all fields he was first in none (Burton 176).

One of Eratosthenes chief accomplishments was the sieve of Eratosthenes, a method of finding prime numbers.  The sieve works by listing a sequence of natural numbers.  Then 1 is crossed off since 1 is not a prime.  Then 2 is circled since it is the first prime, and every multiple of 2 is crossed off.  Next 3 is circled since it is a prime, and then every multiple of 3 is crossed off.  This process continues until the only numbers left are prime numbers (Gulberg 77).  Illustrated is how the sieve works for the first 40 natural numbers.

The first 40 natural numbers.



Eratosthene’s sieve showing the primes in the first 40 numbers.

 

Another of Eratosthenes’ outstanding accomplishments lies in the field of geography.  He had created the most accurate map of his time by using mathematical principles.  He was also the first person to use meridians of longitude and parallels of latitude.  His geographical data was regarded as the fundamental authority for centuries (Burton177).  He measured the circumference of the Earth with incredible accuracy by comparing the noon shadows of Syene and Alexandria (Eratosthenes 3). He also accurately measured the tilt of the Earths axis.  It is believed that Eratosthenes “created the improved calendar adopted by Julius Caesar.  Similar to the modern-day calendar, Eratosthenes’ calendar incorporated the addition of one day every four years, which is now Leap Year” (Young 161).

He was also a historian who recorded the history of Greece based on factual documentation instead of legendary stories.  Chronographiai and ailympionikai are two historical books he wrote by using Olympiad records (Young 161).  Eratosthenes held the title of chief librarian at the distinguished library of Alexandria for forty years of his life.   After losing his eyesight, he committed suicide by starving himself to death.  It is believed that he did not wish to live without being able to read. Eratosthenes died in 194 B.C., yet he will be forever immortalized through his paramount works, discoveries, and achievements.  

 

References

 

Biographical Dictionary of Mathematicians. New York: Charles Scribner’s Sons,

            1991.

Burton, D.M. The History of Mathematics An Introduction. Boston: WCB/McGraw-Hill,

            1999.

“Eratosthones” http://www-history.mcs.st-and.ac.uk/history/Mathematicians/

            Eratosthenes.html. Feb.9, 2000.

“Eratosthenes” http://www.math.bme.hu/mathhist/Mathematicians/Eretosthenes.html

            February 9, 2000.

Gulberg, J. Mathematics from the Birth of Numbers. New York: W.W. Norton and

            Company, 1997.

Young, R. V. Notable Mathematicians from Ancient Times to the Present. Detroit:

            Gale, 1998.