Eratosthenes of Cyrene (; grc-gre,
Ἐρατοσθένης
Eratosthenes of Cyrene (; grc-gre, Ἐρατοσθένης ; – ) was a Greek polymath: a mathematician, geographer, poet, astronomer, and music theorist. He was a man of learning, becoming the chief librarian at the Library of Alexandr ...
; – ) was a Greek
polymath
A polymath ( el, πολυμαθής, , "having learned much"; la, homo universalis, "universal human") is an individual whose knowledge spans a substantial number of subjects, known to draw on complex bodies of knowledge to solve specific pro ...
: a
mathematician
A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems.
Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change.
History
On ...
,
geographer
A geographer is a physical scientist, social scientist or humanist whose area of study is geography, the study of Earth's natural environment and human society, including how society and nature interacts. The Greek prefix "geo" means "earth" a ...
,
poet
A poet is a person who studies and creates poetry. Poets may describe themselves as such or be described as such by others. A poet may simply be the creator ( thinker, songwriter, writer, or author) who creates (composes) poems ( oral or wri ...
,
astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
, and
music theorist
Music theory is the study of the practices and possibilities of music. ''The Oxford Companion to Music'' describes three interrelated uses of the term "music theory". The first is the " rudiments", that are needed to understand music notation (k ...
. He was a man of learning, becoming the chief librarian at the
Library of Alexandria. His work is comparable to what is now known as the study of
geography
Geography (from Greek: , ''geographia''. Combination of Greek words ‘Geo’ (The Earth) and ‘Graphien’ (to describe), literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, an ...
, and he introduced some of the
terminology
Terminology is a group of specialized words and respective meanings in a particular field, and also the study of such terms and their use; the latter meaning is also known as terminology science. A ''term'' is a word, compound word, or multi-wo ...
still used today.
He is best known for being the first person known to calculate the
circumference of the Earth, which he did by using the extensive survey results he could access in his role at the Library; his calculation was remarkably accurate.
He was also the first to calculate
Earth's axial tilt, which has also proved to have remarkable accuracy.
He created the
first global projection of the world, incorporating
parallels and
meridians based on the available geographic knowledge of his era.
Eratosthenes was the founder of scientific
chronology
Chronology (from Latin ''chronologia'', from Ancient Greek , ''chrónos'', "time"; and , ''-logia'') is the science of arranging events in their order of occurrence in time. Consider, for example, the use of a timeline or sequence of events. I ...
; he used Egyptian and Persian records to estimate the dates of the main events of the mythical
Trojan War
In Greek mythology, the Trojan War was waged against the city of Troy by the Achaeans (Greeks) after Paris of Troy took Helen from her husband Menelaus, king of Sparta. The war is one of the most important events in Greek mythology and ...
, dating the Sack of
Troy
Troy ( el, Τροία and Latin: Troia, Hittite: 𒋫𒊒𒄿𒊭 ''Truwiša'') or Ilion ( el, Ίλιον and Latin: Ilium, Hittite: 𒃾𒇻𒊭 ''Wiluša'') was an ancient city located at Hisarlik in present-day Turkey, south-west of Ç ...
to 1183 BC. In
number theory
Number theory (or arithmetic or higher arithmetic in older usage) is a branch of pure mathematics devoted primarily to the study of the integers and integer-valued functions. German mathematician Carl Friedrich Gauss (1777–1855) said, "Mat ...
, he introduced the
sieve of Eratosthenes, an efficient method of identifying
prime number
A prime number (or a prime) is a natural number greater than 1 that is not a product of two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways ...
s.
He was a figure of influence in many fields who yearned to understand the complexities of the entire world.
His devotees nicknamed him ''Pentathlos'' after
the Olympians
''The Olympians'' is an opera in three acts by Arthur Bliss to a libretto by J. B. Priestley, first performed at the Royal Opera House, Covent Garden on 29 September 1949, conducted by Karl Rankl in a production by Peter Brook.
After the initi ...
who were well rounded competitors, for he had proven himself to be knowledgeable in every area of learning. Yet, according to an entry
in the
Suda (a 10th-century encyclopedia), some critics scorned him, calling him ''Beta'' (the second letter of the Greek alphabet) because he always came in second in all his endeavours.
Life
The son of Aglaos, Eratosthenes was born in 276 BC in
Cyrene. Now part of modern-day
Libya
Libya (; ar, ليبيا, Lībiyā), officially the State of Libya ( ar, دولة ليبيا, Dawlat Lībiyā), is a country in the Maghreb region in North Africa. It is bordered by the Mediterranean Sea to the north, Egypt to the east, Suda ...
, Cyrene had been founded by Greeks centuries earlier and became the capital of
Pentapolis (North Africa)
A pentapolis (from Ancient Greek, Greek ''penta-'', 'five' and ''polis'', 'city') is a geographic and/or institutional grouping of five cities. Cities in the ancient world probably formed such groups for political, commercial and military reaso ...
, a country of five cities: Cyrene,
Arsinoe,
Berenice
Berenice ( grc, Βερενίκη, ''Bereníkē'') is the Ancient Macedonian form of the Attic Greek name ''Pherenikē'', which means "bearer of victory" . Berenika, priestess of Demeter in Lete ca. 350 BC, is the oldest epigraphical evidence. ...
,
Ptolemias, and
Apollonia.
Alexander the Great
Alexander III of Macedon ( grc, Ἀλέξανδρος, Alexandros; 20/21 July 356 BC – 10/11 June 323 BC), commonly known as Alexander the Great, was a king of the ancient Greek kingdom of Macedon. He succeeded his father Philip II to ...
conquered Cyrene in 332 BC, and following his death in 323 BC, its rule was given to one of his generals,
Ptolemy I Soter
Ptolemy I Soter (; gr, Πτολεμαῖος Σωτήρ, ''Ptolemaîos Sōtḗr'' "Ptolemy the Savior"; c. 367 BC – January 282 BC) was a Macedonian Greek general, historian and companion of Alexander the Great from the Kingdom of Macedo ...
, the founder of the
Ptolemaic Kingdom. Under Ptolemaic rule the economy prospered, based largely on the export of horses and
silphium
Silphium (also known as ''silphion'', ''laserwort'', or ''laser'') is an unidentified plant that was used in classical antiquity as a seasoning, perfume, aphrodisiac, and medicine. It also was used as a contraceptive by ancient Greeks and Romans ...
, a plant used for rich seasoning and medicine.
Cyrene became a place of cultivation, where knowledge blossomed. Like any young Greek at the time, Eratosthenes would have studied in the local
gymnasium, where he would have learned physical skills and social discourse as well as reading, writing, arithmetic, poetry, and music.
Eratosthenes went to Athens to further his studies. There he was taught
Stoicism by its founder,
Zeno of Citium
Zeno of Citium (; grc-x-koine, Ζήνων ὁ Κιτιεύς, ; c. 334 – c. 262 BC) was a Hellenistic philosopher from Citium (, ), Cyprus. Zeno was the founder of the Stoic school of philosophy, which he taught in Athens from about 300 B ...
, in philosophical lectures on living a virtuous life.
He then studied under
Aristo of Chios
Aristo of Chios ( el, Ἀρίστων ὁ Χῖος ''Ariston ho Chios''; fl. c. 260 BC), also spelled Ariston, was a Greek Stoic philosopher and colleague of Zeno of Citium. He outlined a system of Stoic philosophy that was, in many ways, close ...
, who led a more
cynical
Cynicism is an attitude characterized by a general distrust of the motives of "others". A cynic may have a general lack of faith or hope in people motivated by ambition, desire, greed, gratification, materialism, goals, and opinions that a cynic ...
school of philosophy. He also studied under the head of the
Platonic Academy
The Academy (Ancient Greek: Ἀκαδημία) was founded by Plato in c. 387 BC in Athens. Aristotle studied there for twenty years (367–347 BC) before founding his own school, the Lyceum. The Academy persisted throughout the Hellenistic p ...
, who was
Arcesilaus of Pitane. His interest in
Plato
Plato ( ; grc-gre, Πλάτων ; 428/427 or 424/423 – 348/347 BC) was a Greek philosopher born in Athens during the Classical period in Ancient Greece. He founded the Platonist school of thought and the Academy, the first institution ...
led him to write his very first work at a scholarly level, ''Platonikos'', inquiring into the mathematical foundation of Plato's philosophies.
Eratosthenes was a man of many perspectives and investigated the
art of poetry under
Callimachus
Callimachus (; ) was an ancient Greek poet, scholar and librarian who was active in Alexandria during the 3rd century BC. A representative of Ancient Greek literature of the Hellenistic period, he wrote over 800 literary works in a wide varie ...
.
He wrote poems: one in
hexameter
Hexameter is a metrical line of verses consisting of six feet (a "foot" here is the pulse, or major accent, of words in an English line of poetry; in Greek and Latin a "foot" is not an accent, but describes various combinations of syllables). It w ...
s called ''Hermes'', illustrating the god's life history; and another in
elegiac The adjective ''elegiac'' has two possible meanings. First, it can refer to something of, relating to, or involving, an elegy or something that expresses similar mournfulness or sorrow. Second, it can refer more specifically to poetry composed in ...
s, called ''Erigone'', describing the suicide of the Athenian maiden
Erigone (daughter of Icarius)
In Greek mythology, Erigone ( grc, Ἠριγόνη) was the daughter of Icarius of Athens.
Mythology
Icarius was cordial towards Dionysus, who gave his shepherds wine. They became intoxicated and killed Icarius, thinking he had poisoned them. ...
.
He wrote ''Chronographies'', a text that scientifically depicted dates of importance, beginning with the
Trojan War
In Greek mythology, the Trojan War was waged against the city of Troy by the Achaeans (Greeks) after Paris of Troy took Helen from her husband Menelaus, king of Sparta. The war is one of the most important events in Greek mythology and ...
. This work was highly esteemed for its accuracy.
George Syncellus
George Syncellus ( el, Γεώργιος Σύγκελλος, ''Georgios Synkellos''; died after 810) was a Byzantine chronicler and ecclesiastic. He had lived many years in Palestine (probably in the Old Lavra of Saint Chariton or Souka, near Tekoa ...
was later able to preserve from ''Chronographies'' a list of 38 kings of the
Egyptian Thebes. Eratosthenes also wrote ''Olympic Victors'', a chronology of the winners of the
Olympic Games
The modern Olympic Games or Olympics (french: link=no, Jeux olympiques) are the leading international sporting events featuring summer and winter sports competitions in which thousands of athletes from around the world participate in a vari ...
. It is not known when he wrote his works, but they highlighted his abilities.
These works and his great poetic abilities led the pharaoh
Ptolemy III Euergetes
, predecessor = Ptolemy II
, successor = Ptolemy IV
, nebty = ''ḳn nḏtj-nṯrw jnb-mnḫ-n-tꜢmrj'Qen nedjtinetjeru inebmenekhentamery''The brave one who has protected the gods, a potent wall for The Beloved Land
, nebty_hiero ...
to seek to place him as a librarian at the
Library of Alexandria in the year 245 BC. Eratosthenes, then thirty years old, accepted Ptolemy's invitation and traveled to Alexandria, where he lived for the rest of his life. Within about five years he became Chief Librarian, a position that the poet
Apollonius Rhodius
Apollonius of Rhodes ( grc, Ἀπολλώνιος Ῥόδιος ''Apollṓnios Rhódios''; la, Apollonius Rhodius; fl. first half of 3rd century BC) was an ancient Greek author, best known for the ''Argonautica'', an epic poem about Jason and t ...
had previously held. As head of the library Eratosthenes tutored the children of Ptolemy, including
Ptolemy IV Philopator
egy, Iwaennetjerwymenkhwy Setepptah Userkare Sekhemankhamun Clayton (2006) p. 208.
, predecessor = Ptolemy III
, successor = Ptolemy V
, horus = ''ḥnw-ḳni sḫꜤi.n-sw-it.f'Khunuqeni sekhaensuitef'' The strong youth whose f ...
who became the fourth Ptolemaic pharaoh. He expanded the library's holdings: in Alexandria all books had to be surrendered for duplication. It was said that these were copied so accurately that it was impossible to tell if the library had returned the original or the copy.
He sought to maintain the reputation of the Library of Alexandria against competition from the
Library of Pergamum
The Library of Pergamum in Pergamum, Asia Minor or Anatolia (present day Turkey). It was one of the most important libraries in the ancient world.
The city of Pergamum
Founded sometime during 3rd century BC, during the Hellenistic Age, Perga ...
. Eratosthenes created a whole section devoted to the examination of Homer, and acquired original works of great tragic dramas of
Aeschylus
Aeschylus (, ; grc-gre, Αἰσχύλος ; c. 525/524 – c. 456/455 BC) was an ancient Greek tragedian, and is often described as the father of tragedy. Academic knowledge of the genre begins with his work, and understanding of earlier Greek ...
,
Sophocles
Sophocles (; grc, Σοφοκλῆς, , Sophoklễs; 497/6 – winter 406/5 BC)Sommerstein (2002), p. 41. is one of three ancient Greek tragedians, at least one of whose plays has survived in full. His first plays were written later than, or c ...
and
Euripides
Euripides (; grc, Εὐριπίδης, Eurīpídēs, ; ) was a tragedian of classical Athens. Along with Aeschylus and Sophocles, he is one of the three ancient Greek tragedians for whom any plays have survived in full. Some ancient scholars a ...
.
Eratosthenes made several important contributions to
mathematics and
science
Science is a systematic endeavor that Scientific method, builds and organizes knowledge in the form of Testability, testable explanations and predictions about the universe.
Science may be as old as the human species, and some of the earli ...
, and was a friend of
Archimedes. Around 255 BC, he invented the
armillary sphere. In ''On the Circular Motions of the Celestial Bodies'',
Cleomedes credited him with having calculated the
Earth's circumference
Earth's circumference is the distance around Earth. Measured around the Equator, it is . Measured around the poles, the circumference is .
Measurement of Earth's circumference has been important to navigation since ancient times. The first kno ...
around 240 BC, with a high precision.
Eratosthenes believed there was both good and bad in every nation and criticized
Aristotle
Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatetic school of ph ...
for arguing that humanity was divided into Greeks and
barbarians, as well as for arguing that the Greeks should keep themselves racially pure.
As he aged, he contracted
ophthalmia
Ophthalmia (also called ophthalmitis) is inflammation of the eye. It results in congestion of the eyeball, often eye-watering, redness and swelling, itching and burning, and a general feeling of irritation under the eyelids. Ophthalmia can have d ...
, 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 82 in Alexandria.
Scholarly career
Measurement of Earth's circumference
The measurement of
Earth's circumference
Earth's circumference is the distance around Earth. Measured around the Equator, it is . Measured around the poles, the circumference is .
Measurement of Earth's circumference has been important to navigation since ancient times. The first kno ...
is the most famous among the results obtained by Eratosthenes, who estimated that the meridian has a length of 252,000
stadia
Stadia may refer to:
* One of the plurals of stadium, along with "stadiums"
* The plural of stadion, an ancient Greek unit of distance, which equals to 600 Greek feet (''podes'').
* Stadia (Caria), a town of ancient Caria, now in Turkey
* Stadi ...
(39,060–40,320 km), with an error on the real value between −2.4% and +0.8% (assuming a value for the stadion between 155 and 160 metres).
Eratosthenes described his
arc measurement
Arc measurement, sometimes degree measurement (german: Gradmessung), is the astrogeodetic technique of determining of the radius of Earth – more specifically, the local Earth radius of curvature of the figure of the Earth – by relating the la ...
technique,
in a book entitled ', which has not been preserved. However, a simplified version of the method has been preserved, as described by
Cleomedes.
The simplified method works by considering two cities along the same
meridian
Meridian or a meridian line (from Latin ''meridies'' via Old French ''meridiane'', meaning “midday”) may refer to
Science
* Meridian (astronomy), imaginary circle in a plane perpendicular to the planes of the celestial equator and horizon
* ...
and measuring both the distance between them and the difference in angles of the shadows cast by the sun on a vertical rod (a
gnomon) in each city at noon on the summer
solstice
A solstice is an event that occurs when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. In many countr ...
. The two cities used were
Alexandria
Alexandria ( or ; ar, ٱلْإِسْكَنْدَرِيَّةُ ; grc-gre, Αλεξάνδρεια, Alexándria) is the second largest city in Egypt, and the largest city on the Mediterranean coast. Founded in by Alexander the Great, Alexandri ...
and
Syene
Aswan (, also ; ar, أسوان, ʾAswān ; cop, Ⲥⲟⲩⲁⲛ ) is a city in Southern Egypt, and is the capital of the Aswan Governorate.
Aswan is a busy market and tourist centre located just north of the Aswan Dam on the east bank of t ...
(modern
Aswan
Aswan (, also ; ar, أسوان, ʾAswān ; cop, Ⲥⲟⲩⲁⲛ ) is a city in Southern Egypt, and is the capital of the Aswan Governorate.
Aswan is a busy market and tourist centre located just north of the Aswan Dam on the east bank of the ...
), and the distance between the cities was measured by professional
bematist
Bematists or bematistae (Ancient Greek βηματισταί (''bēmatistaí'', 'step measurer'), from
βῆμα (''bema'', 'pace')), were specialists in ancient Greece and ancient Egypt who measured distances by pacing.
Measurements of Alexa ...
s. A geometric calculation reveals that the circumference of the Earth is the distance between the two cities divided by the difference in shadow angles expressed as a fraction of
one turn.
Geography
Eratosthenes now continued from his knowledge about the Earth. Using his discoveries and knowledge of its size and shape, he began to sketch it. In the Library of Alexandria he had access to various travel books, which contained various items of information and representations of the world that needed to be pieced together in some organized format.
In his three-volume work ''Geography'' ( grc-gre, Geographika, script=Latn), he described and mapped his entire known world, even dividing the Earth into five climate zones:
two freezing zones around the poles, two temperate zones, and a zone encompassing the equator and the tropics.
This book is the first recorded instance of many terms still in use today, including the name of the discipline
geography
Geography (from Greek: , ''geographia''. Combination of Greek words ‘Geo’ (The Earth) and ‘Graphien’ (to describe), literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, an ...
.
He placed grids of overlapping lines over the surface of the Earth. He used parallels and meridians to link together every place in the world. It was now possible to estimate one's distance from remote locations with this network over the surface of the Earth. In the ''Geography'' the names of over 400 cities and their locations were shown, which had never been achieved before.
However, his ''Geography'' has been lost to history, although fragments of the work can be pieced together from other great historians like
Pliny
Pliny may refer to:
People
* Pliny the Elder (23–79 CE), ancient Roman nobleman, scientist, historian, and author of ''Naturalis Historia'' (''Pliny's Natural History'')
* Pliny the Younger (died 113), ancient Roman statesman, orator, w ...
,
Polybius,
Strabo, and
Marcianus
Marcian (; la, Marcianus, link=no; grc-gre, Μαρκιανός, link=no ; 392 – 27 January 457) was Roman emperor of the Byzantine Empire, East from 450 to 457. Very little of his life before becoming emperor is known, other than that he wa ...
. While this work is the earliest we can trace certain ideas, words, and concepts in the historical record, earlier contributions may have been lost to history.
* The first book was something of an introduction and gave a review of his predecessors, recognizing their contributions that he compiled in the library. In this book Eratosthenes denounced
Homer
Homer (; grc, Ὅμηρος , ''Hómēros'') (born ) was a Greek poet who is credited as the author of the ''Iliad'' and the ''Odyssey'', two epic poems that are foundational works of ancient Greek literature. Homer is considered one of the ...
as not providing any insight into what he now described as geography. His disapproval of Homer's topography angered many who believed the world depicted in the ''Odyssey'' to be legitimate.
He also commented on the ideas of the nature and origin of the Earth: he thought of Earth as an immovable globe while its surface was changing. He hypothesized that at one time the
Mediterranean
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...
had been a vast lake that covered the countries that surrounded it and that it only became connected to the ocean to the west when a passage opened up sometime in its history.
* The second book contains his calculation of the circumference of the Earth. This is where, according to Pliny, "The world was grasped." Here Eratosthenes described his famous story of the well in Syene, wherein at noon each summer solstice, the Sun's rays shone straight down into the city-center well. This book would now be considered a text on
mathematical geography.
* His third book of the ''Geography'' contained
political geography. He cited countries and used parallel lines to divide the map into sections, to give accurate descriptions of the realms. This was a breakthrough and can be considered the beginning of geography. For this, Eratosthenes was named the "Father of Modern Geography."
According to Strabo, Eratosthenes argued against the Greek-
Barbarian dichotomy. He says Alexander ignored his advisers by his regard for all people with law and government. Strabo says that Eratosthenes was wrong to claim that Alexander had disregarded the counsel of his advisers. Strabo argues it was Alexander's interpretation of their "real intent" in recognizing that "in some people there prevail the law-abiding and the political instinct, and the qualities associated with education and powers of speech".
[Isaac, Benjamin. Invention of Racism in Classical Antiquity. Princeton University Press, 2013.]
Achievements
Eratosthenes was described by the
Suda Lexicon as a Πένταθλος (Pentathlos) which can be translated as "All-Rounder", for he was skilled in a variety of things: He was a true polymath. He was nicknamed Beta because he was great at many things and tried to get his hands on every bit of information but never achieved the highest rank in anything;
Strabo accounts Eratosthenes as a mathematician among geographers and a geographer among mathematicians.
*
Eusebius of Caesarea in his ''
Preparatio Evangelica'' includes a brief chapter of three sentences on celestial distances
Book XV Chapter 53). He states simply that Eratosthenes found the distance to the Sun to be "" (literally "of
stadia
Stadia may refer to:
* One of the plurals of stadium, along with "stadiums"
* The plural of stadion, an ancient Greek unit of distance, which equals to 600 Greek feet (''podes'').
* Stadia (Caria), a town of ancient Caria, now in Turkey
* Stadi ...
myriads 400 and 80,000") and the distance to the Moon to be 780,000 stadia. The expression for the distance to the Sun has been translated either as 4,080,000 stadia (1903 translation by E. H. Gifford), or as 804,000,000 stadia (edition of Edouard des Places, dated 1974–1991). The meaning depends on whether Eusebius meant 400 myriad plus 80,000 or "400 and 80,000" myriad. With a stade of , 804,000,000 stadia is , approximately the distance from the Earth to the Sun.
* Eratosthenes also calculated the Sun's diameter. According to Macrobious, Eratosthenes made the diameter of the Sun to be about 27 times that of the Earth.
The actual figure is approximately 109 times.
* During his time at the Library of Alexandria, Eratosthenes devised a calendar using his predictions about the
ecliptic
The ecliptic or ecliptic plane is the orbital plane of the Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic agains ...
of the Earth. He calculated that there are 365 days in a year and that every fourth year there would be 366 days.
* He was also very proud of his solution for
Doubling the Cube
Doubling the cube, also known as the Delian problem, is an ancient geometric problem. Given the edge of a cube, the problem requires the construction of the edge of a second cube whose volume is double that of the first. As with the related probl ...
. His motivation was that he wanted to produce catapults. Eratosthenes constructed a mechanical line drawing device to calculate the cube, called the mesolabio. He dedicated his solution to King Ptolemy, presenting a model in bronze with it a letter and an epigram.
Archimedes was Eratosthenes' friend and he, too, worked on the war instrument with mathematics. Archimedes dedicated his book ''The Method'' to Eratosthenes, knowing his love for learning and mathematics.
Number theory
Eratosthenes proposed a simple
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...
for finding
prime numbers. This algorithm is known in mathematics as the
Sieve of Eratosthenes.
In mathematics, the sieve of Eratosthenes (Greek: κόσκινον Ἐρατοσθένους), one of a number of
prime number sieves, is a simple, ancient algorithm for finding all prime numbers up to any given limit. It does so by iteratively marking as composite, ''i.e.'', not prime, the multiples of each prime, starting with the multiples of 2. The multiples of a given prime are generated starting from that prime, as a sequence of numbers with the same difference, equal to that prime, between consecutive numbers. This is the sieve's key distinction from using trial division to sequentially test each candidate number for divisibility by each prime.
Works
Eratosthenes was one of the most pre-eminent scholarly figures of his time, and produced works covering a vast area of knowledge before and during his time at the Library. He wrote on many topicsgeography, mathematics, philosophy, chronology, literary criticism, grammar, poetry, and even old comedies. Unfortunately, there are no documents left of his work after the
destruction of the Library of Alexandria
The Great Library of Alexandria in Alexandria, Egypt, was one of the largest and most significant libraries of the ancient world. The Library was part of a larger research institution called the Mouseion, which was dedicated to the Muses, th ...
.
Titles
* ''Platonikos''
* ''Hermes''
* ''Erigone''
* ''Chronographies''
* ''Olympic Victors''
* ''Περὶ τῆς ἀναμετρήσεως τῆς γῆς'' (''On the Measurement of the Earth'')
(lost, summarized by
Cleomedes)
* ''Гεωγραϕικά'' (''Geographika'')
(lost, criticized by
Strabo)
* ''Arsinoe'' (a memoir of queen
Arsinoe; lost; quoted by
Athenaeus
Athenaeus of Naucratis (; grc, Ἀθήναιος ὁ Nαυκρατίτης or Nαυκράτιος, ''Athēnaios Naukratitēs'' or ''Naukratios''; la, Athenaeus Naucratita) was a Greek rhetorician and grammarian, flourishing about the end of th ...
in the ''
Deipnosophistae'')
* ''Ariston'' (concerning
Aristo of Chios
Aristo of Chios ( el, Ἀρίστων ὁ Χῖος ''Ariston ho Chios''; fl. c. 260 BC), also spelled Ariston, was a Greek Stoic philosopher and colleague of Zeno of Citium. He outlined a system of Stoic philosophy that was, in many ways, close ...
' addiction to luxury); lost; quoted by
Athenaeus
Athenaeus of Naucratis (; grc, Ἀθήναιος ὁ Nαυκρατίτης or Nαυκράτιος, ''Athēnaios Naukratitēs'' or ''Naukratios''; la, Athenaeus Naucratita) was a Greek rhetorician and grammarian, flourishing about the end of th ...
in the ''
Deipnosophistae'')
* The ''
Catasterismi'' (''Katasterismoi''), a lost collection of
Hellenistic
In Classical antiquity, the Hellenistic period covers the time in Mediterranean history after Classical Greece, between the death of Alexander the Great in 323 BC and the emergence of the Roman Empire, as signified by the Battle of Actium in ...
myths about the
constellations, was attributed to Eratosthenes.
See also
*
Aristarchus of Samos (), a Greek mathematician who
calculated
''Calculated'' is the only studio album by the American punk rock band Heavens to Betsy, released on March 21, 1994, by Kill Rock Stars. The album received positive reviews from critics.
Recording and release
''Calculated'' was recorded in Se ...
the distance from the Earth to the Sun.
*
Eratosthenes (crater)
Eratosthenes crater is a relatively deep lunar impact crater that lies on the boundary between the Mare Imbrium and Sinus Aestuum mare regions. It forms the western terminus of the Montes Apenninus mountain range. It is named after ancient Greek ...
on the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
.
*
Eratosthenian period in the
lunar geologic timescale.
*
Eratosthenes Seamount
The Eratosthenes Seamount or Eratosthenes Tablemount is a seamount in the Eastern Mediterranean, in the Levantine basin about south of western Cyprus. Unlike most seamounts, it is a carbonate platform not a volcano. It is a large, submerged mass ...
in the eastern Mediterranean Sea.
*
Eratosthenes Point in
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
.
*
Hipparchus
Hipparchus (; el, Ἵππαρχος, ''Hipparkhos''; BC) was a Greek astronomer, geographer, and mathematician. He is considered the founder of trigonometry, but is most famous for his incidental discovery of the precession of the equi ...
(), a Greek mathematician who
measured the radii of the Sun and the Moon as well as their distances from the Earth.
*
Posidonius
Posidonius (; grc-gre, Ποσειδώνιος , "of Poseidon") "of Apameia" (ὁ Ἀπαμεύς) or "of Rhodes" (ὁ Ῥόδιος) (), was a Greek politician, astronomer, astrologer, geographer, historian, mathematician, and teacher nativ ...
(), a Greek astronomer and mathematician who
calculated
''Calculated'' is the only studio album by the American punk rock band Heavens to Betsy, released on March 21, 1994, by Kill Rock Stars. The album received positive reviews from critics.
Recording and release
''Calculated'' was recorded in Se ...
the circumference of the Earth.
Notes
References
Further reading
* Aujac, G. (2001). ''Eratosthène de Cyrène, le pionnier de la géographie''. Paris: Édition du CTHS. 224 p.
*
*
*
*
*
*
*
*
*
* Fuentes González, P. P.,
Ératosthène de Cyrène, in R. Goulet (ed.), ''Dictionnaire des Philosophes Antiques'', vol. III, Paris, Centre National de la Recherche Scientifique, 2000, pp. 188–236.
* Geus K. (2002)
''Eratosthenes von Kyrene. Studien zur hellenistischen Kultur- und Wissenschaftgeschichte'' München: Verlag C.H. Beck. (Münchener Beiträge zur Papyrusforschung und antiken Rechtsgeschichte. Bd. 92) X, 412 S.
*
*
* Honigmann, E. (1929). ''Die sieben Klimata und die πολεις επισημοι''. Eine Untersuchung zur Geschichte der Geographie und Astrologie in Altertum und Mittelalter. Heidelberg: Carl Winter's Universitätsbuchhandlung. 247 S.
*
*
*
*
*
* Marcotte, D. (1998). "La climatologie d'Ératosthène à Poséidonios: genèse d'une science humaine". G. Argoud, J.Y. Guillaumin (eds.). ''Sciences exactes et sciences appliquées à Alexandrie (IIIe siècle av J.C. – Ier ap J.C.)''. Saint Etienne: Publications de l'Université de Saint Etienne: 263–277.
* McPhail, Cameron (2011)
''Reconstructing Eratosthenes' Map of the World: a Study in Source Analysis''. A Thesis Submitted for the Degree of Master of Arts at the University of Otago Dunedin, New Zealand.
*
*
*
*
*
* Rosokoki, A. (1995), ''Die Erigone des Eratosthenes. Eine kommentierte Ausgabe der Fragmente'', Heidelberg: C. Winter-Verlag
* Shcheglov, D.A. (2004/2006). "Ptolemy's System of Seven Climata and Eratosthenes' Geography". ''Geographia Antiqua'' 13: 21–37.
*
*
*
* Thalamas, A. (1921). ''La géographe d'Ératosthène''. Versailles.
*
External links
English translation of the primary source for Eratosthenes and the size of the Earthat Roger Pearse.
Berlin, 1822 (PDF) (Latin/Greek), Reprinted Osnabruck 1968 (German)
*
ttp://www.newadvent.org/cathen/01303a.htm New Advent Encyclopedia article on the Library of AlexandriaEratosthenes' sieve in classic BASIC all-web based interactive programming environmentInternational pedagogical project: project
:fr:La main à la pâte.
Open source Physics Computer Model about Eratosthenes estimation of radius and circumference of EarthEratosthenes, video
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