synonymEratoceni(Ancient Greek historian, linguist, philosopher) generally refers to Eratosthenes
Eratosthenes (275-194 BC) was an outstanding mathematician, astronomer and geographer in ancient Greece, who made outstanding contributions to cartography.
He pioneered the method of measuring the length of the earth's circumference, and obtained the first scientific data. According to the coordinate principle, he drew the world map using longitude and latitude lines, especially his first“geography”This word, written in three volumes of monographs, has been honored as "the father of geography".[1]
Eratosthenes was born in Cyrene, a Greek colony in Libya.When he was young, he studied in the Lucerne School of Aristotle, and perhaps also in Plato College.In about 244 BC, the Egyptian monarch Euergetes hired him as the court teacher of Prince Philopator.In 234 BC, he was appointed to take over from Calichus as the director of the Library of Alexandria.Because of the collection of scientific works of various schools in the ancient world, the Alexander Library at that time became the world's largest scientific center, and the directors were undoubtedly the most prestigious people in the academic world.Eratosthenes was also a genius who was good at using books and materials. He read sample books, drew nutrition from them, and obtained necessary materials for scientific research.
Main contributions
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Figure 1
His famous book, "The Revision of the Size of the Earth", proposed an idea that the length of an arc on the meridian of the Earth can be measured by using a sundial and a gnomon for a single observation.The so-called Guibiao is actually a time measuring device, which is composed of a hollowed hemisphere and a pair of mutually perpendicular wooden markers fixed at the center of the inner solitary surface.The time of a solar day can be measured by the length of the sun on the inner side of the Gui Biao.In theory, he assumed that Saini (Svene - today's Aswan, Egypt) and Alexandria were on the same meridian, and Dan Saini was just on the Tropic of Cancer.On the summer solstice, the sun directly shines on the Tropic of Cancer, and the Saini noon sun can reach the deepest well bottom without shadow, while at the same time on the sundial, the main watch of Alexandria Port can show shadow, as shown in Figure 1.He believed that if we can determine the proportion of the shadow length to the big circle on the Gui Biao, then this proportion should be equal to the proportion of the arc on the meridian between the two places to the circle of the earth.He finally worked out that the ratio was 1/50.Since the distance between the two places is known to be 5000 stadia (Greek length unit, equivalent to 157.5 meters), the earth circumference is calculated to be 5000 × 50=250000 stadia.In practice, in order to make it easy to divide the value by 360, Eratosthenes added 2000, which is 252000 Stadia.When converted into metric system, it is equal to 39690km, which is very close to the current value of 40000 km.
The measurement of Eratosthenes is very rough, which contains many errors. For example, Saini and Alexandria are not on the same meridian. Saini is 3 ° 03 'east of Alexandria, and Saini's latitude is 24 ° 5'30' ', which is not exactly on the regression line. The distance between the two places is not more than 4530 Stadia.This caused the large arc value to change from 7 ° 05 'to 7 ° 12', and also caused errors in the final results.But for a pioneer who had neither telescope nor other precision measuring instruments available, the result was remarkable.
Earth research
Another important achievement of Eratosthenes is that it was the first time to draw a world map based on the longitude and latitude line network, and correctly marked the geographical regions and cities that had been inhabited at that time.On this figure, he imitated his predecessor Siax and selected a datum latitude line and a datum longitude line, which are orthogonal to each other in the center of the figure and become the coordinate control axis.The latitude line starts from the pillar of Linnaeus, crosses the Mediterranean Sea to the Gulf of Issus, extends eastward along the southern foot of the Taurus Mountains in Asia, and the longitude line goes from Alexandria Port to the estuary of the Borisfen River through Rhode Island and Byzantium.He took the datum meridian as the primary meridian, which was the main basis for calculation and drawing.
On his map, it has been correctly speculated that the Atlantic Ocean is connected to the Indian Ocean, and people can bypass Africa from the sea.But he mistakenlyCaspian SeaAs a bay of the Arctic Ocean, it is envisaged that Asia can be surrounded by sea.Of course, due to the limitations of the times, he could not know the true shape of East Asia, North Asia, West Africa and South Africa.
According to Eratosthenes, the width of the continent seems to be more than twice its length, and the area around the known world is a vast ocean.On his map, we can see that the world has been divided into Europe, Asia and Libya.The map he drew created a correct way to use the longitude and latitude network to draw maps, making people take a big step in establishing a system concept for the whole earth.
In addition, Eratosthenes first estimated that the intersection angles of the ecliptic and the equator are 23 ° 51 ', 19' '. 5, and conducted research on mathematical geography;He also suggested that the world should be divided into five zones, one tropical zone, two temperate zones and two frigid zones, with 24 ° latitude to the south and north as the dividing line of the hot temperate zone.He has written many books on science and philosophy, but unfortunately they have all been lost, and can only infer something from other works indirectly.
In addition, the book "Earth Size Correction" also includes research on the following aspects: the length of the equatorRegression lineAndpolar circleDistancePolar zoneThe size of the sun and the moon, the distance between the sun, the earth and the moon, the total and partial eclipses of the sun and the moon, and the change of the length of the day with latitude and season.These studies represented the high level of geographical development at that time.[1]
