2 Life Editor of Characters
Eratosthenes was hired as a royal teacher by the Egyptian King and was appointed as a first-class researcher in the Alexandria Library. He has been a librarian since 234 BC. At that time, the library of Alexandria was the highest center of science and knowledge in the ancient western world, where various ancient scientific and literary works were collected. Curator was the most authoritative position in Greek academic circles at that time, and was usually awarded to highly respected and popular scholars. Eratosthenes served as the curator until his death, which also illustrates this point.
Eratosthenes made full use of his position as the director of Alexandria Library, and made excellent use of his rich geographical data and maps. His genius enabled him to make scientific innovations on the basis of literature. Eratosthenes's outstanding contribution to geography is embodied in his two representative works, Revision of the Earth's Size and Introduction to Geography. The former discusses the shape of the earth and takes the circumference of the earth as an example. The latter is a map of the inhabited part of the world and its description. In this book, he systematically put forward the method of drawing the world and country with latitude and longitude net, and completely redrawn the map of Ionia. Based on accurate measurement, he combined all the achievements of astronomy and geodesy as much as possible, so the world map he compiled was not only authoritative at that time, but also became the basis of all ancient maps later. Although Eratosthenes's two geographical works are unfortunately lost, through the preserved fragments, especially Strappo's quotations, later generations have a certain understanding of their contents and the author's incisive opinions.
3 measure the circumference of the earth editor
The calculation of the circumference of the earth is the essence of the book Revision of the Earth's Size. Before Eratosthenes, many people tried to make measurements and estimates, such as Yudhoyono. However, most of them lack theoretical basis and the calculation results are very inaccurate. Eratosthenes was the first to combine astronomy with geodesy, and put forward the idea of observing the position of the sun in two places at the same time from summer to the sun. Through research and analysis, the scientific method of calculating the circumference of the earth is summarized. This method is much more perfect and accurate than Yudoko's method of relying solely on astronomical observation, because the simple astronomical method is influenced by instrument precision and astronomical refractive index, which often leads to large errors. Eratosthenes chose Sene and Alexander on the same meridian. The observation of the position of the sun from summer to sun is compared. Near Siena, there is a deep well on an island in the middle of the Nile. On the day of summer solstice, the sun can shine directly at the bottom of the well. This phenomenon has a long history and attracts many travelers to watch the wonders. This shows that the sun is at the zenith on the solstice in summer. At the same time, he chose a very high obelisk in Alexandria as a reference, and measured the shadow length of the tower on the day of summer solstice. In this way, he can measure the angle between the vertical obelisk and the sunlight. After obtaining these data, he applied Thales' mathematical law, that is, when a light passes through two parallel lines, their diagonal angles are equal. Eratosthenes observed that this angle is 712', which is equivalent to 1/50 with a circumferential angle of 360. This means that this angle is equal to 1/50. That is to say, the distance from Siena to Alexandria should be equal to 1/50 of the circumference of the earth. Next, with the help of the geodetic data of the Royal Surveyor, Eratosthenes measured the distance between the two cities as 5,000 Greek miles. Once this result is obtained, the circumference of the earth can be multiplied by 50 and the result is 250,000 Greek miles. In order to conform to the traditional system of dividing the circumference into 60 equal parts, Eratosthenes raised this figure to 252,000 Greek, so it can be divided by 60. The Greek Rio in Egypt is 157.5 meters, which can be converted into modern metric system. The circumference of the earth is about 39,375 kilometers, which is surprisingly close to the actual circumference of the earth after being corrected by Eratosthenes. Therefore, Eratosthenes skillfully combined astronomy with geodesy.
In addition, the revision of the size of the earth also includes the following studies: equatorial length, the distance from the Tropic of Cancer to the polar circle, the range of the polar belt, the size of the sun and the moon, the distance between the sun and the moon, total solar eclipse and partial solar eclipse, and the change of the length of a day with latitude and season. These studies represented the height of geographical development at that time.
4 depicting the new earth editor
Introduction to Geography is devoted to the study of the world where human beings live. This book is divided into three volumes. The first volume is an introduction, which gives a historical review of the emergence and development of geography, and then focuses on the structure and evolution of the earth and the movement of water (tides, currents in the straits, etc.). The second volume is mathematical geography, which mainly discusses the shape and structure of the sky, the earth and the ocean, the division of the regions and zones of the earth and the scope of the known world. The third volume discusses the redrawing of the world map, including the newly compiled world map and regional description. Eratosthenes's works summarized the achievements of Greek geography, marked the highest level of geography in this period, and were important documents in the treasure house of ancient geography.
Eratosthenes inherited and developed Aristotle's livable zone theory, and divided the world into three continents: Europe, Asia and Africa, and five temperature zones, including one tropical zone, two temperate zones and two cold zones. He improved Aristotle's zoning method and strictly divided the latitude of the north-south boundary of the five zones. Compared with previous scholars, it is much more scientific and systematic. His division of the earth is quite close to the concept of "zone" in modern geography. The position of the Tropic of Cancer determined by him is only half a degree away from its actual position (23 30'), and the accuracy is amazing. However, Eratosthenes's division of the world's three continents was far from the actual situation, which was obviously limited by the level of epistemology and science at that time.
Eratosthenes realized that the old Ionian map must be completely redrawn. His goal is to draw a more reasonable image of the world by using geometric methods based on accurate new data of astronomy and geodesy. He unequivocally rejected Alexander's previous data, and adopted a lot of achievements of Pythias' voyage, Alexander's expedition and other recent geographical surveys. When using data, he did not blindly follow, but paid great attention to analysis and judgment. For example, when he processed the route survey data, he considered the factors such as terrain fluctuation and road curvature, and reduced the mileage data provided by the data by115 on average, thus greatly improving the accuracy of the map and the accuracy of the data.