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.

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

Several works among the best known during this long period could be cited as an example, from Strabo ( Geography ), Eratosthenes ( Geography ) or Dionisio Periegetes ( Periegesis Oiceumene ) in the Ancient Age to the Alexander von Humboldt ( Cosmos ) in the century XIX, in which geography is regarded as a physical and natural science, of course, through the work Summa de Geografía of Martín Fernández de Enciso from the early sixteenth century, which is indicated for the first time the New World.

The early part of Pytheas ' voyage is outlined by statements of Eratosthenes that Strabo says are false because taken from Pytheas.

A statement of Eratosthenes attributed by Strabo to Pytheas, that the north of the Iberian Peninsula was an easier passage to Celtica than across the Ocean, is somewhat ambiguous: apparently he knew or knew of both routes, but he does not say which he took.

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.

Random access is critical, or at least valuable, to many algorithms such as binary search, integer sorting or certain versions of sieve of Eratosthenes.

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

* 200 BC – Eratosthenes uses shadows to determine that the radius of the Earth is roughly 6, 400 km

* The first good measurement of the distance between Earth and the Sun is made by Eratosthenes ( approximate date ).

In mathematics, the sieve of Eratosthenes (), one of a number of prime number sieves, is a simple, ancient algorithm for finding all prime numbers up to any given limit.

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.

Eratosthenes ' date is therefore 1104 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.

Eratosthenes ' date is therefore 1104 BC.

As with Posidonius, Eratosthenes ' stadium is thought to have equated to 1 / 10 of a mile, so that his measure translates to 25, 000 ( or 25, 200 ) miles.

An example of the sort of attack this portrayal was intended to defend against can be found in two orations of Lysias, Against Eratosthenes and Against Agoratus ; there, Theramenes is portrayed as treasonous and self-interested, doing tremendous harm to the Athenian cause through his machinations.

A formula used in Eratosthenes ' method is

For this method, it is also necessary to check for divisibility by all primes that are less than c. Observations analogous to the preceding can be applied recursively, giving the Sieve of Eratosthenes.

This possibility is likely, given that many ancient Greek philosophers are thought to have lived over the age of 90 ( e. g., Xenophanes of Colophon, c. 570 / 565 – c. 475 / 470 BC, Pyrrho of Ellis, c. 360 – c. 270 BC, Eratosthenes of Cirene, c. 285 – c. 190 BC, etc .).

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.

In number theory, a lucky number is a natural number in a set which is generated by a " sieve " similar to the Sieve of Eratosthenes that generates the primes.

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.

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

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.

In 1773, Lessing published an epigram he had found in a manuscript during his work as a librarian ; it claimed to be a letter sent by Archimedes to Eratosthenes.

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.

< 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 Portuguese Court, which agreed with the figure provided by Eratosthenes, rejected Columbus ' proposal because they believed that the distance to Asia over the open Western Ocean was too great for the ship's crews to survive the journey without being able to make port and resupply.

Conversely, the remarkably accurate calculation of the earth's circumference by Eratosthenes, and the invention of a steam engine by Heron, both ascribed in chapter 60 to the priest Menes, historically occurred in Alexandrian Egypt, centuries after the period of the novel.

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 ).

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.

The first scientific estimation of the radius of the earth was given by Eratosthenes.

Since the estimate by Eratosthenes, many models have been created.

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

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.

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.

The founder of the mathematical school was the celebrated Euclid ; among its scholars were Archimedes ; Apollonius of Perga, author of a treatise on Conic Sections ; Eratosthenes, to whom we owe the first measurement of the earth ; and Hipparchus, the founder of the epicyclical theory of the heavens, afterwards called the Ptolemaic system, from its most famous expositor, Claudius Ptolemy.

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