ERATOSTHENES

ALEXANDRIAN MATHEMATICIAN AND

GEOGRAPHER

(276-194 B.C.)

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.

• 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

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.

• 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.

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.

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.

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.

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. 

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.

• 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.

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.

REFERENCES

• http://en.wikipedia.org/wiki/Eratosthenes

• http://astroverada.com/earth/stadia.html

THANKING YOU!