The Almagest is an ancient work that supports the idea of geocentrism.
In the 2nd century , Claudius Ptolemy published a treatise on astronomy entitled Hè magalè syntaxis , which in Arabic became known as Almagest . The work includes an extensive list of stars , explains the apparent movement of the stars and offers a description of a geocentric system (which places the Earth at the center of the universe).
Detailed work
To develop his treatise, Ptolemy started from a catalog of stars that Hipparchus of Nicaea had created. The Almagest presents thirteen volumes, beginning with the exposition of the geocentric system and ending with a detail of the method followed by the author to calculate the trajectories and positions of the planets.
Ptolemy offers information on forty-eight constellations in the Almagest . The astronomer also exposes the foundations of the geocentric system, with the planets, the Moon and the Sun revolving around the Earth .
It is important to mention that Ptolemy wrote his book in Greek. In the 9th century , the Caliph Al-Mamun promoted the translation of the text into Arabic, which came to be mentioned as Al-Majisti (translatable as “The Greatest” ). Finally the work remained in history as Almagest .
The popularity of the Almagest in the Western world came through its Arabic version. Only in the 12th century was the Almagest translated into our language .
The thirteen volumes
As we mentioned above, this work is a true example of hard and meticulous work, regardless of the fact that the information it presents is no longer considered current from a scientific point of view. Regarding Hipparchus of Nicaea , we can say that he was another scientist dedicated to astronomy, in addition to geography and mathematics, who lived between 190 and 120 BC. C. His catalog is not preserved, so we cannot know with certainty how much it has in common with Ptolemy's.
The common edition of Almagest belongs to the historian and philologist Johan Ludvig Heiberg , born in Denmark in the mid-19th century, which he published in 1899. The translations into German and English, from 1912 and 1984, respectively, are based on it. Note that some changes were included in the English version thanks to having reviewed the original manuscripts.
Below we will see the topics that each of the thirteen volumes deals with:
1 : presentation of the geocentric system. Although it is Ptolemy's version, other scientists had already supported the same general idea of the Earth as the center of the known universe;
2 : the length of the year and the time at which the equinoxes take place;
3 : more about the equinoxes, as well as dealing with the solstices;
4 : the synodic month (the period between two equivalent phases of the moon, which usually lasts approximately 29.53 days) and other information about the Moon;
5 : the correction of the deviation of the angles at which the Moon and the Sun move;
6 : a method of predicting the occurrence of eclipses and a measurement of the diameter of the Moon and the Sun;
7 and 8 : it is stated that the relative position of the stars is fixed, in addition to including a catalog of southern stars, that is, those closest to the south pole;
9 to 13 : the method of determining the paths and positions of the planets, with a detailed explanation of the aforementioned epicyclic circles.
Ptolemy's geocentric system was based on the concept of epicyclic motion.
Geocentric system
It should be noted that the geocentric system postulated by Ptolemy was the predominant theory to explain the orbits of the planets until Copernicus proposed the heliocentric model . Later, Galileo Galilei and Johannes Kepler provided more data that consolidated heliocentrism.
The movement of the planets, the Moon and the Sun is explained in the Almagest using a very detailed system that Ptolemy himself designed, which consisted of a series of epicyclic circles. This last term refers to the fact that each circle has its center on the edge of another; In other words, all bodies that rotate around another follow a circular orbit, placing on it the center of another rotary movement with which, along the entire path, they draw an ellipse.