The Ptolemy system is a geocentric system of the world, according to which the planet Earth, which remains motionless, occupies a central place in the Universe. 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. The heliocentric system of the world later became an alternative, which became the basis for the current cosmological models of the Universe.
The emergence of geocentrism
The Ptolemy system for many centuries was considered fundamental to all scientists. Earth has been considered the center of the universe since ancient times. It was assumed that there is a central axis of the Universe, and some support restrains the Earth from falling.
Ancient people believed that it was a mythical giant creature, such as an elephant, a turtle or several whales. Thales of Miletus, considered the father of philosophy, suggested that the oceans themselves could be such a natural support. Some suggested that the Earth, located in the center of the cosmos, does not need to move in any of the directions, it simply rests in the very center of the Universe without any support.
Peace 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 the observations at that time were made exclusively from the surface of the Earth, because of this it was impossible to reliably establish whether our planet is in motion or not.
In this regard, the ancient astronomers had two theories. According to one of them, the Earth is in 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 relied 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 was clearly contrary to existing opinions and religious views. That is why the second point of view did not receive a mathematical justification; over the course of many centuries, the opinion of the immobility of the Earth has been approved in astronomy.
Proceedings of the astronomer
In the book of Ptolemy, entitled "The Great Building", the basic ideas of ancient astronomers about the structure of the Universe were generalized and presented. The Arabic translation of this work became widespread. It is known as the Almagest. Ptolemy based his theory on four main assumptions.
The Earth is located directly in the center of the Universe and motionless, all celestial bodies move around it in circles at a constant speed, that is, uniformly.
The Ptolemy system is usually called geocentric. In a simplified form, it is described as follows: planets move in circles with uniform speed. In the general center of everything is the motionless Earth. The Moon and the Sun revolve around the Earth without epicycles, but according to the defenders that lie inside the sphere, and “motionless” stars remain on the surface.
The daily movement of any of the luminaries was explained by Claudius Ptolemy the rotation of the entire Universe around a motionless Earth.
Planetary motion
Interestingly, for each of the planets, the scientist picked up the sizes of the radii of the deferent and the epicycle, as well as the speed of their movement. This was only possible under certain conditions. For example, Ptolemy took for granted that the centers of all the epicycles of the lower planets are located in a certain direction from the Sun, and for the upper planets in the same direction the radii of the epicycles are parallel.
As a result, the direction to the Sun in the Ptolemy system became predominant. It was also concluded that the periods of revolution of the corresponding planets are equal to the same stellar periods. All this in the theory of Ptolemy meant that the system of the world includes the most important features of the real and real movements of the planets. To reveal them to the full extent was possible much later to another ingenious astronomer - Copernicus.
One of the important issues in the framework of this theory was the need to calculate the distance, 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 was able to give a complete and comprehensive explanation of the visible motions of the planets, and also made it possible to calculate their position in the future with accuracy that would correspond to observations made with 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 harshly suppressed by the Christian church.
Over time, serious discrepancies were found between theory and observations, which arose as accuracy increased. They managed to finally eliminate them, only significantly complicating the optical system. For example, certain irregularities in the apparent motion of the planets that were discovered as a result of later observations were explained by the fact that the center of the first epicycle is no longer the planet itself, but the so-called center of the second epicycle. And now, on its circumference, the celestial body moves.
In the event that such a construction turned out to be insufficient, additional epicycles were introduced until the position of the planet on the circle corresponded to 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 for astronomical observations in practice. This primarily concerned navigation. New methods for calculating the motion of the planets were needed, which should have become easier. They were developed by Nikolai 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 toward the center of the world. The earth itself was located in the center. On this basis, Aristotle refuted the orbital motion of the planet, concluding that it leads to a parallactic displacement of stars. He sought to calculate how much from Earth to the Moon, having managed to achieve only approximate calculations.
Ptolemy's biography
Ptolemy was born around 100 AD. The main sources of information about the biography of the scientist are his own works, which modern researchers have managed to build in chronological order due to cross-references.
Sketchy 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 owes his extensive and versatile erudition to the active use of volumes stored in the Alexandria Library.
Proceedings of the scientist
The main works of Ptolemy related to astronomy, but he also left a mark in other scientific fields. In particular, in mathematics he derived the Ptolemy inequality and theorem, based on the theory of the product of the diagonals of a quadrilateral inscribed in a circle.
Five books compose 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 refraction of light. 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 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.