The Ptolemaic system is a geocentric system of the world, according to which the central place in the Universe is occupied by the planet Earth, which remains motionless. The Moon, the Sun, all the stars and planets are already gathering around it. It was first formulated in Ancient Greece. It became the basis for ancient and medieval cosmology and astronomy. An alternative later became the heliocentric system of the world, which became the basis for the current cosmological models of the Universe.
The emergence of geocentrism
The Ptolemaic system has been considered fundamental for all scientists for many centuries. Since ancient times, the Earth has been considered the center of the universe. It was assumed that there is a central axis of the Universe, and some kind of support keeps the Earth from falling.
Ancient people believed that it was some mythical giant creature, such as an elephant, a turtle, or several whales. Thales of Miletus, who was considered the father of philosophy, suggested that the world ocean itself could be such a natural support. Some have suggested that the Earth, being at the center of space, does not need to move inin any direction, it simply rests in the very center of the universe without any support.
World system
Claudius Ptolemy sought to give his own explanation for all the visible movements of the planets and other celestial bodies. The main problem was that all observations at that time were carried out exclusively from the surface of the Earth, because of this it was impossible to reliably determine whether our planet was in motion or not.
In this regard, ancient astronomers had two theories. According to one of them, the Earth is at the center of the universe and remains motionless. Mostly the theory was based on personal impressions and observations. And according to the second version, which was based solely on speculative conclusions, the Earth rotates around its own axis and moves around the Sun, which is the center of the whole world. However, this fact clearly contradicted the existing opinions and religious views. That is why the second point of view did not receive a mathematical justification, for many centuries the opinion about the immobility of the Earth was approved in astronomy.
Proceedings of an astronomer
In the book of Ptolemy called "The Great Construction" the main ideas of ancient astronomers about the structure of the Universe were summarized and outlined. The Arabic translation of this work was widely used. It is known under the name "Almagest". Ptolemy based his theory on four main assumptions.
Earth is located directly inthe center of the Universe and is motionless, all celestial bodies move around it in circles at a constant speed, that is, evenly.
Ptolemy's system is called geocentric. In a simplified form, it is described as follows: the planets move in circles at a uniform speed. In the common center of everything is the motionless Earth. The Moon and the Sun revolve around the Earth without epicycles, but along deferents that lie inside the sphere, and "fixed" stars remain on the surface.
The daily movement of any of the stars was explained by Claudius Ptolemy as the rotation of the entire Universe around the motionless Earth.
Movement of planets
It is interesting that for each of the planets the scientist selected the sizes of the radii of the deferent and the epicycle, as well as the speed of their movement. This could only be done under certain conditions. For example, Ptolemy took it for granted that the centers of all the epicycles of the lower planets are located in a certain direction from the Sun, and the radii of the epicycles of the upper planets in the same direction are parallel.
As a result, the direction to the Sun in the Ptolemaic system became predominant. It was also concluded that the periods of revolution of the corresponding planets are equal to the same sidereal periods. All this in Ptolemy's theory meant that the system of the world includes the most important features of the actual and real movements of the planets. Much later, another brilliant astronomer, Copernicus, managed to fully reveal them.
One of the important issues in this theory was the need to calculatedistance, how many kilometers from the Earth to the Moon. It has now been reliably established that it is 384,400 kilometers.
Merit of Ptolemy
The main merit of Ptolemy was that he managed to give a full and exhaustive explanation of the apparent movements of the planets, and also allowed them to calculate their position in the future with an accuracy that would correspond to observations made by the naked eye. As a result, although the theory itself was fundamentally wrong, it did not cause serious objections, and any attempts to contradict it were immediately severely suppressed by the Christian church.
Over time, serious discrepancies between theory and observations were discovered, which arose as accuracy improved. They were finally eliminated only by significantly complicating the optical system. For example, certain irregularities in the apparent motion of the planets, which were discovered as a result of later observations, were explained by the fact that it is no longer the planet itself that revolves around the center of the first epicycle, but the so-called center of the second epicycle. And now a celestial body is moving along its circumference.
If such a construction turned out to be insufficient, additional epicycles were introduced until the position of the planet on the circle correlated with the observational data. As a result, at the beginning of the 16th century, the system developed by Ptolemy turned out to be so complex that it did not meet the requirements that were imposed on astronomical observations in practice. First of all, it concerned navigation. New methods were needed to calculate the motion of the planets, which were supposed to be easier. They were developed by Nicolaus Copernicus, who laid the foundation for the new astronomy on which modern science is based.
Aristotle's views
The geocentric system of the world of Aristotle was also popular. It consisted in the postulate that the Earth is a heavy body for the Universe.
As practice has shown, all heavy bodies fall vertically, as they are in motion towards the center of the world. The earth itself was located in the center. On this basis, Aristotle refuted the orbital motion of the planet, coming to the conclusion that it leads to a parallactic displacement of the stars. He also sought to calculate how much from the Earth to the Moon, having managed to achieve only approximate calculations.
Biography of Ptolemy
Ptolemy was born around 100 AD. The main sources of information about the biography of the scientist are his own writings, which modern researchers have managed to arrange in chronological order through cross-references.
Fragmentary information about his fate can also be gleaned from the works of Byzantine authors. But it should be noted that this is unreliable information that is not trustworthy. It is believed that he owed his wide and versatile erudition to the active use of volumes stored in the Library of Alexandria.
Proceedings of a scientist
The main works of Ptolemy are related to astronomy, but he also left a mark in other scientific fields. ATin particular, in mathematics he derived Ptolemy's theorem and inequality, based on the theory of the product of the diagonals of a quadrilateral inscribed in a circle.
Five books make up his treatise on optics. In it, he describes the nature of vision, considers various aspects of perception, describes the properties of mirrors and the laws of reflections, and discusses the laws of light refraction. For the first time in world science, a detailed and fairly accurate description of atmospheric refraction is given.
Many people know Ptolemy as a talented geographer. In eight books, he details the knowledge inherent in the man of the ancient world. It was he who laid the foundations of cartography and mathematical geography. He published the coordinates of eight thousand points located from Egypt to Scandinavia and from Indochina to the Atlantic Ocean.
