An article from 1975, from the book "Opus 200 by Isaac Asimov, Fantasia Library, Hyperion Publishing. This expense no longer exists
An ellipse looks like a flat circle. It can be flattened to such an extent that it will be impossible to distinguish it from a circle. Even the orbit of Mercury, which is flatter than any other orbit known in Kepler's time, is not very flat. The Sun is not at the center of the elliptical orbits of the planets around it. The flatter the ellipse, the closer one of its ends is to the sun. As the Earth moves around the Sun, it is only 146.4 million kilometers from it at one end of its orbit, but 151.2 million kilometers at the other end. The farthest distance is 4 percent greater than the nearest distance.
Mercury's orbit around the sun is more elliptical, so there is an even greater difference. When Mercury is at the edge of the ellipse closest to the Sun, it is only 54.8 million kilometers from the Sun, but at the other end it is 70.4 million kilometers away from it. The distance at the far point is approximately 50 percent greater than the distance at the near point.
Kepler was able to find the elliptical orbits of all the planets, but what about the comets? If these were celestial bodies, did they also have orbits? Kepler carefully studied the reports he had of the changing positions of the comets in the sky. Finally he decided that the comets must move in straight lines. He believed that they came from a distant place in space, passed by the sun, and then traveled on to a distant place in space that was in the other direction.
They could only be seen when they were close to the sun, and when they reflected its light. Before they got close enough to the sun they couldn't be seen. After they moved far enough from the sun, they could not be seen again. According to Kepler, the comets were not part of the solar system. Each comet passed through the solar system only once, and no more were seen.
The Italian astronomer Giovanni Alfonso Borelli meticulously studied the conditions of the comet that appeared in the sky in 1664. He found that he had to disagree with Kepler.
The only way to understand the comet's path across the sky, Borelli argued, was to assume that it changed direction as it passed the Sun. It came closer and closer to the sun, along a path that was almost straight. So, it went around the sun and left a line that looked good again, but one that changed direction.
The way Borelli explained it was to point out that the ellipses could indeed be very flat. They could be so flat that they resembled a long, thin cigar. In fact, if you imagined an ellipse that was more and more flat, more and more elongated, you could eventually imagine one that was so flat that it went on and on, ad infinitum. Such an ellipse will be closed at only one end. It will never be closed in the other direction, but will simply go on and on. An ellipse with one edge that goes on forever is called a parabola.
Borelli decided that the orbit of a comet is a parabola, with the sun very close to the closed end. The comet entered at one end of the parabola, flew around the sun, and moved out along the other side of the parabola.
Borelli's view was similar to Kepler's, except that the trajectory he envisioned was not a straight line. Like Kepler, Borelli believed that the comet was originally so far away that it could not be seen. As it got closer to the sun it became bright enough to be seen, then as it got further and further away from the sun, it became too dim to be seen again. According to Borelli's view, like Kepler's, the comets were not part of the solar system, each comet passed through the solar system only once, and never returned.
Kepler's concept of elliptical orbits made the planets much more complicated, but many questions remained unanswered. Why do the planets revolve around the sun in ellipses and not in circles (or in another curved line?) Why do the planets move faster when they are close to the sun than when they are far away from it?
These and many other questions were answered by the English scientist, Isaac Newton, in 1687 Newton published a book in which he described his theory about the gravitational force of the universe, according to this theory, every body in the universe attracts every other body, the force of attraction between two bodies Some depended on the 'mass' of each body (the amount of matter it contains) and the distance between them. The strength of attraction can be calculated using a simple mathematical equation.
Newton showed how to use the equation to find the exact orbit of the moon around the earth, and the orbits of the planets around the sun.
The same equation that explained why a star moves sometimes fast and sometimes slowly, and why some of the planets move faster than others, it can account for slight changes in the motion of the planets that are caused by the effects of one planet on something, even when all the planets are caught in the enormous pull of the much larger sun , the equation that explains the tides of sea waves on the surface of the earth, and many other things.
However, the comets still remain a group of celestial bodies, whose nature has not yet been determined. If comets were moving in orbits that were parabolas, Newton's theory would not be able to explain this fact. However, they assumed that the orbits were not really parabolas, they assumed that the orbits were Simply very long ellipses, and in a certain place the other end exists, we can observe the comet only at the end of the orbit closest to the sun. The shape of the small part of the giant orbit would be a narrow curve if the ellipse was very long. The shape would be wider if the ellipse was even longer, and even wider if the ellipse never closed and was a parabola.
The differences between the shapes of the small part of the orbit we can see, as predicted by Vyton's theory, were so minute that astronomers of Vyton's time could not distinguish them. They were unable to determine with certainty whether the orbit of a comet was a very long ellipse or whether it was a parabola.
This was decisive. If the orbit of a comet was a parabola, then after one 'visit' to the solar system, it would never return. If the orbit was a very, very long ellipse, then eventually the comet would reach the other end of the ellipse, turn around, and start approaching the sun again. The comet was Shab.
In fact, if astronomers could calculate the exact length of the orbit, they would be able to predict when the comet would return. It could have been a brilliant victory for Newton's theory.
Newton had a young friend, Edmund Halley, who encouraged Newton to publish his book, and he was interested in the problems of comets.
About 1682 a comet appeared, and Hallie studied with great care its positions and the path it took in the sky. From the part of the orbit that he could see, he could not say whether the star would ever return, but it seemed to him that if a comet did return, it would do so at regular intervals - every few years - and draw the same path in the sky.
Therefore, Halley began to collect all the early reports of cometary condensers from the past, and began to compare them. He observed that the comet of 1682, which he himself observed, followed the same path in the sky as the comet of 1607. The same path also moved the comet of 1532 (which was traced by Pracastoro and Appian) and the comet of 1456.
These comets appeared at a frequency of seventy-five or seventy-six shenis. Is it possible that it was the same comet, which returned approximately every seventy-five years? Could it have been a 'periodic comet'?
Halley calculated the orbit of the comet that returned every seventy-five years by drawing the orbit drawn by the comet of 1682, the results were amazing, Saturn, the farthest planet from the sun (as it was known in Halley's time), was never farther from the sun than 1.5 billion km, however, the comet of 1682 moved 5.12 billion km away from the Sun before reaching the other end of its elliptical orbit and beginning to move inward again, the comet moving three times the distance of the planet
Saturn.
On the other hand, the comet passed along the edge of the ellipse closest to the Sun, it came as close as 86.4 million km from it, which was about half the distance between the Earth and the Sun.
After calculating the trajectory, Halley declared that the comet of 1682 would return around 1758, and follow a certain path in the sky. Halley did not live long enough to witness the return of the comet. He was 86 years old when he died, in 1742, but it was too early to predict a return,
However, there were others who expected it, a French astronomer, Alexis Claude Claro, calculated the orbit as described by Halley, he realized that the gravitational attraction of large stars such as Jupiter and Saturn, would cause the comet to follow. It will not orbit the Sun until about 1759.
In 1758, many astronomers observed this part of the sky, where, according to Halley, the Shabish star was supposed to appear. They did not have to depend on their eyes as Tycho and earlier astronomers had. The telescope was invented in 1609.
On December 25, 1758, on Christmas Day. German farmer. Johann Georg Palutzesch, himself an amateur astronomer, located the comet, the comet of 1682 appeared in the sky where Halley determined it would appear, and continued to move along the path Halley had predicted. It was moving around the sun quite close to the time Claro had predicted.
There was no doubt that it was the comet of 1682, and that it returned. Dabach meant that part of the mystery of the comets had become clear. They followed the same rules as other solar system bodies, except that its orbit was more elliptical. Naturally, the comet of 1682, which returned and passed around the sun in 1758 was called 'Halley's Comet'.
Halley's Comet is the most famous comet, it turns out that it was the one that appeared in the sky in 1066 when William of Normandy was preparing to invade England. It was also in the sky in 11 BC, when Jesus was born, and some believe that it is possible and it is the 'Star of Bethlehem'.
Halley's Comet has returned twice since Palitzsch saw it. He returned in 1835, and shone in the sky as Mark Twain was born. He returned in 1910, and shone in the sky when Mark Twain died.
Editor's note
The book was written in the 1986s and predicted that Halley's Comet would return again in 1910. He did, but apparently in the seventy-six years that have passed since his appearance in 1997, his dust emissions have weakened, or alternatively he was also at the opposite end of the solar system from Earth. I waited for it with many astronomy enthusiasts and had to content myself with watching it through a telescope. Anyway, in 39 I enjoyed the great sight of Comet Hale-Bop. Unfortunately, this comet claimed XNUMX victims - members of a mysterious sect who believed that a spaceship was waiting for them in the tail of the comet and killed themselves so that their souls would reach it.
