Comets are the most unusual in appearance celestial objects available for observation with the naked eye. They attract the attention of people from ancient times. Together with asteroids and meteoric bodies, comets are considered to be small bodies of the solar system. The peculiarity of comets is that when approaching the Sun they have a tail, almost always directed from the line of the Sun.
The story of comet astronomy
Prehistory of the study of comets. Thousands of years past, individuals realized that the celestial luminaries much don't modification their mutual position (stars), and if they are doing, they move on the strictly established methods and with a well-defined speed ("wandering stars", or planets, as well as the Moon and therefore the Sun). Therefore, the surprising look of "tailed luminaries" within the night sky caused individuals to feel worry and was thought-about a harbinger of dangerous events.
"Comet" in Greek means "hairy star". In ancient Greece, and later in the Middle Ages, the comet was often depicted as a severed head with waving hair. Since the history of mankind has always been full of tragic events - wars, epidemics, palace coups d'état, murders of noblemen - then each appearance of a bright comet necessarily accompanied any of these events. Court astrologers could only deeply "tie" the affairs of earth and heaven.
Roman historians reported that the death of Julius Caesar in 44 AD coincided with the appearance of a bright comet in the sky. Therefore, in the Middle Ages and even later at the royal courts of Europe was widely believed that the comet heralds the death of the king or his heir (a very convenient way to "write off" the palace intrigue on the phenomenon of nature).
Here is an example of the emotional description of the comet in 1528, compiled by the famous French surgeon Ambroise Pare: "This comet was so terrible and terrible and gave rise to such great confusion among the people that some died of fear alone, while others fell ill. It was a luminous luminaire of enormous length and bloody color; at the top of it was visible a compressed hand holding a long sword, as if ready to open. At the end of his blade were three stars. On both sides of the rays coming out of the tail of this comet were many axes, knives, swords, and blood-stained, and among them were horrible human faces with their beards bent and their hair standing on their backs.
The first appearance
The first appearance of the comet in history dates back to 2296 BC. At that time, it was observed by Chinese astronomers who carefully watched the movement of the comet along the constellations. In the ancient Chinese view, the sky was a vast empire ruled by the sun and consisting of numerous regions and provinces in which the brightest planets were rulers. Couriers were needed to deliver imperial decrees to remote provinces. Their role was assigned to the "tailed luminaries", as they quickly moved through many constellations and could transmit the imperial will. The Chinese astronomers considered the movement of the ruling planets from one constellation to another after the passage of the comet to be a confirmation of this. Interestingly, such a positive role was attributed to comets only in China.
Certainly, some ancient Greek and Roman thinkers, who considered comets as natural phenomena unrelated to human destiny, resisted the ordinary views of the people. Aristotle considered comets to be atmospheric phenomena belonging to the changing "lunar world", a kind of earthly fumes, heating or even igniting from the proximity to the heavenly "sphere of fire". However, he did not insist on his hypothesis; he wrote: "Since we do not have an opinion about comets based on feelings, I should be satisfied with such an explanation, which does not contain contradictions with known truths.
The Roman philosopher Seneca, who wrote in his correspondence with Aristotle in his dispute with Aristotle, was the closest to the modern scientific truth: "I cannot agree that the comet is only a lit fire; it is rather one of the eternal creations of nature... The comet has its own place between the celestial bodies... It describes its path and does not go out, but only leaves. Let us not be surprised that the laws of the comet movement have not yet been solved; there will come a time when hard work will reveal to us the hidden truth now...". This time has come only after a millennium and a half.
The birth of scientific cometography
Tycho Brahe, who observed a bright comet in 1577, compared his data with the observations of other European astronomers and came to the conclusion that the comet did not have a noticeable parallax, and therefore it was far beyond the limit of the Earth's atmosphere and even beyond the Moon's orbit, i.e. was an independent celestial body.
Theoretical work of Nicolas Copernicus and practical discoveries made with the telescope of Galileo finally undermined the trust in the geocentric system of Aristotle and Ptolemy, which served as the basis of scientific outlook for almost two millennia. Perhaps this fact would be more surprised by Aristotle himself. Unlike his many followers, he was not a dogmatist; he wrote: "I am talking about celestial bodies, but I see them only from afar; I can not see them where they are, and most of what is happening in the sky, avoiding our eyes ... If someone can give another explanation for these phenomena, based on a better and more natural basis, he acquires the legitimate right to our gratitude.
Distance gratitude to Aristotle was deserved by those who prepared the ground for the search for the general laws of the movement of celestial bodies - astronomers of the era of Tycho and Galilee. These very laws were established in 1609-18 by the talented mathematician Johann Kepler, who used the most accurate data on the movements of the planets, received by Tycho Brahe. Kepler established three laws of movement of planets on elliptical trajectories around the Sun, but the reason for such movement was unclear. And only the law of gravitation and laws of mechanics, finally formulated by Issac Newton in 1687, gave it a scientific explanation.
The calculations made by Newton at the request of the English astronomer Edmond Halley proved that the bright comet of 1682 moves in an elliptical orbit. On the basis of own observations of this comet and analysis of reliable historical records of observations of comets for the previous 300 years, Halley made the first catalogs of 24 comets, which included the elements of their orbits calculated by him. Analyzing these data, Halley noticed a close match of the orbital elements in the three comets that appeared in 1531, 1607 and 1682. He suggested that it could be the same comet. Its period of reference around the Sun appeared 75,5 years so that the following occurrence should occur in 1758. Halley's prediction was confirmed: in the beginning of 1759, there was a bright comet, having confirmed the trust in the laws of mechanics, on the basis of which the calculations of comet trajectories were made. Unfortunately, Halley did not live to this day. The periodic comet opened by him was called the comet of Halley. So began scientific research comets.