Eratosthenes knew that in Syene, in Egypt, the Sun was directly overhead at the summer solstice, while he estimated that the angle formed by a shadow cast by the Sun at Alexandria was 1 / 50th of a circle.

He succeeded Eratosthenes as head librarian of the Library of Alexandria at the age of sixty.

Eratosthenes of Alexandria, who died about 194 BC, wrote on astronomy and geography, but his work is known mainly from later summaries.

The first known grade measurement was performed by Eratosthenes ( 240 BC ) between Alexandria and Syene in what is now Egypt, determining the radius of the Earth with remarkable correctness.

* c. 240 BCE Eratosthenes of Alexandria, Egypt determines fairly accurately the circumference of the Earth using angles of shadows in Syene and Alexandria.

* Eratosthenes ( 276194 BC ), who made the first known reliable estimation of the Earth's size.

Those who believe that the stories of the Trojan War are derived from a specific historical conflict usually date it to the 12th or 11th centuries BC, often preferring the dates given by Eratosthenes, 1194 – 1184 BC, which roughly corresponds with archaeological evidence of a catastrophic burning of Troy VIIa.

Although Strabo cited the antique Greek astronomers Eratosthenes and Hipparchus, acknowledging their astronomical and mathematical efforts towards geography, he claimed that a descriptive approach was more practical, such that his works were designed for statesmen who were more anthropologically than numerically concerned with the character of countries and regions.

Those who believe that the stories of the Trojan War derive from a specific historical conflict usually date it to the twelfth or eleventh centuries BC, often preferring the dates given by Eratosthenes, 1194 – 1184 BC, which roughly correspond with archaeological evidence of a catastrophic burning of Troy VIIa.

Posidonius was informed in his approach to finding the Earth's circumference by Eratosthenes, who a century earlier used the elevation of the sun at different latitudes to arrive at a figure of 250, 000 stadia ( which he rounded to 252, 000 so that it would be divisible by 60 ).

1241 indicates that Apollonius was succeeded in the position by Eratosthenes ; this must have been after 247 / 246 BCE, the date of the accession of Ptolemy III Euergetes, who was probably tutored by Apollonius and who appointed Eratosthenes.

Lysias and Polemarchus were rich men, having inherited property from their father, Cephalus ; and Lysias claims that, though merely resident aliens, they discharged public services with a liberality which shamed many of those who enjoyed the franchise ( Against Eratosthenes xii. 20 ).

Richard Pankhurst and others have argued that the name should be understood as " River of the Boras people ", where asta can be related to Proto-Nubian asti " water "., while-boras can be linked to a number of Roman allusions to a tribe named the Bora, who lived near Meroe, and another tribe named the Megabares ( in Eratosthenes and Strabo, in Pliny the Elder ).

About 150 years after the disaster, the philosopher Eratosthenes visited the site and reported that a standing bronze statue of Poseidon was submerged in a " poros ", " holding in one hand a hippocamp ", where it posed a hazard to those who fished with nets.

Strabo mentions him as a contemporary of Eratosthenes, who was born 275 BC.

Eratosthenes, who lived in Athens as a young man, claimed that Aristo and Arcesilaus were the two most important philosophers of his age.

Herodotus, Strabo, and other classical authors repeatedly mention the Caspians but do not seem to know much about them ; they are grouped with other inhabitants of the southern shore of the Caspian Sea, like the Amardi, Anariacae, Cadusii, Albani ( see below ), and Vitii ( Eratosthenes apud Strabo, 11. 8. 8 ), and their land ( Caspiane ) is said to be part of Albania ( Theophanes Mytilenaeus apud Strabo, 11. 4. 5 ).

* A twelve-book essay about Homer's Catalogue of Ships, also based on Eratosthenes of Cyrene and Demetrius of Scepsis, dealing with Homeric geography and how it has changed along the centuries.

In addition to these dozen sentences, the geographer Strabo mentions India a few times in the course of his long dispute with Eratosthenes about the shape of Eurasia.

Most of these are purely geographical claims, but he does mention that Eratosthenes ' sources say that some of the Greek kings conquered further than Alexander ; Strabo does not believe them on this, but modern historians do ; nor does he believe that Menander and Demetrius son of Euthydemus conquered more tribes than Alexander There is half a story about Menander in one of the books of Polybius which has not come down to us intact.

Pliny claims that this gave Eratosthenes the idea about how to calculate the circumference of the Earth ( N. H. 2. 183, 6. 168 ).

* Eratosthenes 276 – 194 BC, ancient Greece

Early in Classical Greece, that the earth is a sphere (" round "), was generally known by all, and around 240 BCE, Eratosthenes ( 276 BCE – 194 BCE ) accurately estimated its circumference.

* Eratosthenes ( c. 276 – 194 BC ), Greek mathematician, geographer and astronomer

* Eratosthenes, Greek mathematician, geographer and astronomer ( d. 194 BC )

The Hellenistic world view after Seleucus: ancient world map of Eratosthenes ( 276 – 194 BC ), incorporating information from the campaigns of Alexander and his successors.

The Greek astronomer Hipparchus ( c. 190 – c. 120 BCE ) credited Eratosthenes ( 276 – 194 BCE ) as the inventor of the armillary sphere.

As noted in the book Huai Nan Zu, in the 2nd Century BC Chinese astronomers effectively inverted Eratosthenes ' calculation of the curvature of the Earth to calculate the height of the sun above the earth.

The Earth's circumference was first determined around 240 BC by Eratosthenes.

* 1184 BC – Trojan War: Troy is sacked and burned, according to calculations by Eratosthenes.

* Eratosthenes ( late 3rd century BC )

Maps based on scientific principles had been made since the time of Eratosthenes ( 3rd century BC ), but Ptolemy improved projections.

Ephorus gives 1135 BC, Sosibius 1172 BC, Eratosthenes 1184 BC / 1183 BC, Timaeus 1193 BC, the Parian marble 1209 BC / 1208 BC, Dicaearchus 1212 BC, Herodotus around 1250 BC, Eretes 1291 BC, while Douris 1334 BC.

Ancient Greek historians variously placed the Trojan War in the 12th, 13th, or 14th centuries BC: Eratosthenes to 1184 BC, Herodotus to 1250 BC, Duris of Samos to 1334 BC.

Eratosthenes used this spelling, however Hipparchos wrote it as Κάνωπος.

The Samian Sibyl, by name Phemonoe, or Phyto of whom Eratosthenes wrote.

A Sieve of Eratosthenes benchmark, computing all prime numbers less than 65536, was tested on a Sun SPARCstation 1.

One reason is that Ptolemy estimated the size of the Earth as too small: while Eratosthenes found 700 stadia for a great circle degree on the globe, in the Geographia Ptolemy uses 500 stadia.

Book 34 was entirely devoted to questions of geography and included some trenchant criticisms of Eratosthenes, whom he accused of passing on popular preconceptions or laodogmatika.

In 1915, he introduced a new method, based on Legendre's version of the sieve of Eratosthenes, now known as the Brun sieve, which addresses additive problems such as Goldbach's conjecture and the twin prime conjecture.

< p > Strabo ... enters largely, in the Second Book of his Geography, into the opinions of Eratosthenes and other Greeks on one of the most difficult problems in geology, viz., by what causes marine shells came to be plentifully buried in the earth at such great elevations and distances from the sea .</ p >

That alternative route, different from the theoretical eastward route, was based on calculations of the Earth's circumference made by Columbus which showed the measurement to be substantially less than the classic 10, 000 mile figure given by Eratosthenes in the 3rd century BC.

The Return of the Heracleidae, which is the closest event to a Dorian Invasion available in legend, must coincide with the entry of Aristodemus and his brethren into Arcadia, which, based on the chronology of Eratosthenes, happened 328 years before the generally accepted date of the first year of the first Olympiad, 776 BC.

The Return of the Heracleidae, which is the closest event to a Dorian Invasion available in legend, must coincide with the entry of Aristodemus and his brethren into Arcadia, which, based on the chronology of Eratosthenes, happened 328 years before the generally accepted date of the first year of the first Olympiad, 776 BC.

Ptolemy discussed and favored this revised figure of Posidonius over Eratosthenes in his Geographia, and during the Middle Ages scholars divided into two camps regarding the circumference of the earth, identified with Eratosthenes ' calculation on the one hand and Posidonius ' 180, 000-stadium measure on the other.

De Astronomia was first published, with accompanying figures, by Erhard Ratdolt in Venice, 1482, under the title Clarissimi uiri Hyginii Poeticon astronomicon opus utilissimum This " Poetic astronomy by the most renowned Hyginus, a most useful work ," chiefly tells us the myths connected with the constellations, in versions that are chiefly based on Catasterismi, a work that was traditionally attributed to Eratosthenes.

Many parts of modern geometry are based on the work of Euclid, while Eratosthenes was one of the first scientific geographers, calculating the circumference of the earth and conceiving the first maps based on scientific principles.

He is also the author of the mathematical libraries DJBFFT, a fast portable FFT library, and of primegen, an asymptotically fast small prime sieve with low memory footprint based on the sieve of Atkin rather than the more usual sieve of Eratosthenes.

The two towns were separated by one degree on the meridian, so from his measurement he was able to calculate a value for the circumference of the earth – a feat celebrated in the title of his book Eratosthenes Batavus ( The Dutch Eratosthenes ), published in 1617.

On the divisions and boundaries of Europe, Asia and Africa, he repeats Eratosthenes ; like all classical geographers from Alexander the Great ( except Ptolemy ) he regards the Caspian Sea as an inlet of the Northern Ocean, corresponding to the Persian and Arabian ( Red Sea ) gulfs on the south.

He had a high reputation as a Grecian, a Latinist and a philologist, and he brought out with the collaboration of others his an edition of St Cyprian in 1682, an English translation of The Unity of the Church in 1681, editions of Nemesius of Emesa ( 1671 ), of Aratus and of Eratosthenes ( 1672 ), Theocritus ( 1676 ), Alcinous on Plato ( 1677 ), St Clement's Epistles to the Corinthians ( 1677 ), Athenagoras ( 1682 ), Clemens Alexandrinus ( 1683 ), Theophilus of Antioch ( 1684 ), Grammatica rationis sive institutiones logicae ( 1673 and 1685 ), and a critical edition of the New Testament in 1675.

Many sources claim that the fabled Well of Erastothenes, famous for the calculation of the circumference of Earth by Eratosthenes, was located on the island.

* Chronicle ( Χρονικά ), a Greek history in verse from the fall of Troy in the 12th century BC to roughly 143 BC ( although later it was extended as far as 109 BC ), and based on previous works by Eratosthenes of Cyrene.