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Posted on August 29th, 2012, by

People on the earth have been always very interested in the things and processes, happening around them in the nature. The moment came, when they also paid attention to the sky and the components of it. Comets belonged to the unusual objects, which, as soon as they appeared, attracted attention of usual people and scientists of course. In this paper we are going to discuss the historical development of the scientific thought about comets during ancient times and Middle Ages.

For many centuries already scientists studied the mysterious phenomenon, which we call comets today. This is evident, that due to the fact, that they appeared so seldom, they presented such a great interest for everybody. At the very beginning comets were considered to be signals, which god gave to the Earth and its inhabitants. This was the easiest explanation of the phenomenon, needing no scientific research and background. However, in the sixteenth century appeared opponents of this view, for example the Hungarian scholar Andreas Dudith stated, that if these were god’s remindings about our sins, then they should be present in the sky constantly.

Modern scientists have already proved, that comets are some remnants from the solar system. The detailed research of the comets is able to provide information about the compositions of the planets, which were formed around 4.5 billion years ago (Bowdoin, 13).

As it was already mentioned, the history of comets study is rather long and rich. This is actually considered to be one of the brightest examples of how progressive scientific ideas developed from religious and scientific thoughts of the past. Further we are going to stop at the most important scientists, who devoted their time to studies of comets and their theories.

The ideas of Aristotle were without any doubts the dominating in the history of western scientific thought for almost 2000 years. He wrote the book ”“ Meteorologica, where he expressed his ideas about comets. “Besides stating his own views Aristotle presented the views of his Greek predecessors from the sixth to the fourth century BC including those of Pythagoras (c.560-480B-C), Hippocrates of Chios (fl.440B.C.) and Anaxagoras of Clazomenae (c.500-428B.C.)”¯ (Sagan, 111). Aristotle underlined, that Pythagoras developed the idea of existence of only one comet. This approach was supported by Hippocrates, who also presented the explanation of the tail of the comet, as a formation appearing thanks to the moisture taken from the earth. According to him, comet was at a bigger distance from other stars and was the slowest one among them. Anaxagoras believed, that comets were formed due to planetary conjunction, this idea, although described in Meteorologica, was still not supported by Aristotle, because he proved, that comets existed in the spaces, where there were no stars, this explanation was accepted also in the seventeenth century.

The Aristotelian studies of the comets were certainly related to his general theory about cosmology. “Aristotle viewed the universe as finite spherical and geocentric where the first four elements viz. earth, water, air and fire moved naturally along straight, finite lines but they remained confined to the imperfect sublunar world”¯ (Sagan, 118). The fifth element here was presented by the supralunar space ”“ the space where the Moon and other planets were moving all the time in their ideal circles. The scientists worked out the following sequence of the concentric spheres: first the earth, then the water, then the air and finally the fiery sphere. Aristotle stated, that comets formed from parts of the earth as a result of the Sun heating the Earth. The moisture remained in the lower layers, whereas the warm exhalation was able to rise to the fiery sphere. These parts were becoming so hot, that they were able to unite and form comets. The movement of the formed comet was supported by the movements of the heavens in the last sphere. The type of the exhalation influenced the form and sustainability of the comet. As it was already said, these views, developed by Aristotle were accepted by other scholars within around two thousand years afterwards. Certainly nowadays we are aware of the fact, that he was mistaken. However very important is that although his theories were wrong, they still presented a serious step forward in studying comets and a huge step aside from simple superstitions of the ancient people.

Aristotle was not the only scientist, who devoted his time to researching comets, Seneca put down his ideas in the Natural Questions. In this work Seneca also described the views of other scholars, “this is from Seneca’s Natural Questions we know the views of comets of the Chaldeans or Babylonians. From Seneca we also learn the cometary ideas of some Greek scholars like Ephorus of Cyme (fl. 340 BC), Epigenes, Apollonius of Myndus and Posidonius (135-51 BC)”¯ (Bowdoin, 47). Seneca didn’t support that idea of Ephorus, that comets split into two separate parts. Epigenes in reality changed a little the ideas, described by Aristotle already. Apollonius stated, that comets couldn’t be considered either planetary conjunctions or optical illusions.

The natural history of Pliny the Elder or Gaius Plinius SecundusĀ  – the head of the Roman fleet played a great role for scientific views of the Middle Ages. Surprising is that he was not a scholar himself, but an outstanding writer and traveler. The major aim of his 37 volumes of the Natural History he put as following: “to give a general description of everything that is known to exist throughout the Earth”¯ (Bowdoin, 58).

There were numerous myths and facts without proofs in his writing, but it was the most complete Natural History source of the Middle Ages. He didn’t develop any theories concerning comets on his own, but rather wrote about the perceptions of them by his contemporaries.

The comets were considered to be omens of some terrible events, and Pliny described a lot of events, which followed the appearance of comets and which he thought could be related to them. He worked out some rules, which could be supposedly used for identifying the nature of the disaster that will take place after certain comet was seen. According to Pliny’s writings, some comets were moving and some were not; they moved in various directions, but only those, which moved in the south were without tails. Although with little scientific background, the ideas of Pliny were seriously considered in other scientific works during the seventeenth century as well.

The greatest scientist of the Alexandria of the seventeenth century was considered to be Ptolemy. In his work ”“ Almagest ”“ he studied the movements of the bodies in the heaven. However comets, the scientists didn’t attribute to heaven bodies, rather to evils. Actually there is a reflection of the Pliny’s ideas to be found. Ptolemy also stated, that it was possible to note what part of the world will suffer from some evil, depending on the part of the sky, where a comet was seen and on the direction of its tail. The shapes of the comet were “responsible”¯ for the concrete persons and the kinds of evils definition. The period of the disaster could be identified by the position of the comet in relation to the sun. During the Middle Ages as well as Renaissance, most of the scholars based their views on the studies of Aristotle and Ptolemy.

The Austrian astronomer and mathematician ”“ George von Purbach worked on a cometary parallax determination in 1456 already, unfortunately the instruments, he was able to apply, were not accurate enough for confirmation, that comets belong to celestial or terrestrial bodies (Schechner, 24). His student- Johanes Muller ”“ was said to formulate the methods for determination of the cometary parallax. The views of the parallax measurements of the comets were later supported by such scientists as Tycho Brahe, Michael Mastlin, Cornelius Gemma.

Overall, in this paper we have studied the most outstanding views and theories concerning comets, their formation, forms, tails, movements and other characteristics, developed by the most well known scientists of the ancient times and Middle Ages. The initial understandings of this natural phenomenon were certainly based on pure superstitions, because people knew so little about the world around them, but still had to find some explanations for the natural processes. However, as time passed, the theories concerning comets distanced from religious or superstitious grounds and received more scientific attention. Even if nowadays most of these researchers and theories might seem ridiculous even to school pupils, we should not forget, that exactly these theories laid the groundwork for further and modern scientific researchers about comets and planetary systems.

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