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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Hubble law. History and essence of scientific discovery
Directory / The most important scientific discoveries “In 1744, the Swiss astronomer de Shezo and independently in 1826 Olbers formulated the following paradox,” writes T. Regge in his book, “which led to the crisis of the then naive cosmological models. Imagine that the space around the Earth is infinite, eternal and invariably and that it is uniformly filled with stars, and their density is on average constant.With the help of simple calculations, Szezo and Olbers showed that the total amount of light sent to Earth by stars should be infinite, due to which the night sky will not be black, but, to put it mildly, flooded with light. To get rid of their paradox, they assumed the existence of vast wandering opaque nebulae in space, obscuring the most distant stars. In fact, this is impossible to get out of the situation: by absorbing light from the stars, the nebulae would involuntarily heat up and themselves emit light so the same as the stars. So, if the cosmological principle is true, then we cannot accept Aristotle's idea of an eternal and unchanging universe. Here, as in the case of relativity, nature seems to prefer symmetry in its development, rather than the imaginary Aristotelian perfection. However, the most serious blow to the inviolability of the Universe was dealt not by the theory of stellar evolution, but by the results of measurements of the receding velocities of galaxies obtained by the great American astronomer Edwin Hubble. Edwin Hubble (1889–1953) was born in the small town of Marshfield, Missouri, to John Powell Hubble, an insurance agent, and his wife, Virginia Lee James. Edwin became interested in astronomy early, probably under the influence of his maternal grandfather, who built himself a small telescope. Edwin graduated from high school in 1906. At the age of sixteen, Hubble entered the University of Chicago, which was then one of the top ten best educational institutions in the United States. The astronomer F.R. Multon, author of the well-known theory of the origin of the solar system. He had a great influence on the further choice of Hubble. After graduating from university, Hubble managed to get a Rhodes scholarship and go to England for three years to continue his education. However, instead of the natural sciences, he had to study law at Cambridge. In the summer of 1913, Edwin returned to his homeland, but he never became a lawyer. Hubble strove for science and returned to the University of Chicago, where at the Yerk Observatory, under the guidance of Professor Frost, he prepared a dissertation for a Ph.D. His work was a statistical study of faint spiral nebulae in several parts of the sky and was not particularly original. But even then Hubble shared the opinion that "spirals are star systems at distances often measured in millions of light years." At that time, a great event was approaching in astronomy - the Mount Wilson Observatory, which was headed by the remarkable organizer of science D.E. Hale, was preparing to commission the largest telescope - a hundred-inch reflector (250 cm - Approx. Aut.). Among others, Hubble received an invitation to work at the observatory. However, in the spring of 1917, when he was completing his dissertation, the United States entered the First World War. The young scientist declined the invitation and volunteered for the army. As part of the American Expeditionary Force, Major Hubble ended up in Europe in the fall of 1918, shortly before the end of the war, and did not have time to take part in the hostilities. In the summer of 1919, Hubble demobilized and hurried to Pasadena to accept Hale's invitation. At the observatory, Hubble began to study nebulae, focusing first on objects visible in the Milky Way band. In the anthology "Book of Primary Sources on Astronomy and Astrophysics, 1900-1975" by K. Lang and O. Gingerich (USA), which reproduced the most outstanding research for three quarters of the twentieth century, three Hubble works are placed, and the first of them is a work on the classification of extragalactic nebulae. The other two relate to the establishment of the nature of these nebulae and the discovery of the law of redshift. In 1923, Hubble began observing the nebula in the constellation Andromeda with 6822 and XNUMX inch reflectors. The scientist concluded that the large Andromeda Nebula is indeed another star system. Hubble obtained the same results for the MOS XNUMX nebula and the Triangulum nebula. Although a number of astronomers soon became aware of Hubble's discovery, the official announcement was made only on January 1, 1925, when G. Ressel read Hubble's report at the congress of the American Astronomical Society. The famous astronomer D. Stebbins wrote that the Hubble report "expanded the volume of the material world a hundredfold and definitely resolved the long dispute about the nature of spirals, proving that these are gigantic sets of stars, almost comparable in size to our own Galaxy." Now the Universe appeared before astronomers as a space filled with star islands - galaxies. Already one establishment of the true nature of the nebulae determined the place of Hubble in the history of astronomy. But an even more outstanding achievement fell to his lot - the discovery of the law of redshift. Spectral studies of spiral and elliptical "nebulae" were started in 1912 on the basis of such considerations1 if they are really located outside our Galaxy, then they do not participate in its rotation and therefore their radial velocities will indicate the motion of the Sun. It was expected that these speeds would be on the order of 200–300 kilometers per second, i.e., they would correspond to the speed of the Sun around the center of the Galaxy. Meanwhile, with a few exceptions, the radial velocities of galaxies turned out to be much higher: they were measured in thousands and tens of thousands of kilometers per second. In mid-January 1929, in Proceedings of the US National Academy of Sciences, Hubble presented a short note entitled "On the relationship between the distance and the radial velocity of extragalactic nebulae." At that time, Hubble already had the ability to match the speed of a galaxy with its distance for 36 objects. It turned out that these two quantities are related by the condition of direct proportionality: the speed is equal to the distance multiplied by the Hubble constant. This expression is called the Hubble law. The scientist in 1929 determined the numerical value of the Hubble constant at 500 km / (s x Mpc). However, he made a mistake in establishing the distances to galaxies. After repeated corrections and refinements of these distances, the numerical value of the Hubble constant is now taken to be 50 km/(s x Mpc). Mount Wilson Observatory began to determine the radial velocities of ever more distant galaxies. By 1936, M. Humason published data for one hundred nebulae. A record speed of 42 kilometers per second was recorded from a member of a distant cluster of galaxies in Ursa Major. But this was already the limit of the 000-inch telescope. More powerful tools were needed. “You can approach the issue of the Hubble expansion of space using more familiar, intuitive images,” says T. Regge. “For example, imagine soldiers lined up on some square with an interval of 1 meter. so that this interval increases to 2 meters.Whichever way the command is executed, the relative speed of two soldiers standing next to each other will be 1 m/min, and the relative speed of two soldiers standing at a distance of 100 meters from each other will be 100 m/min , if we take into account that the distance between them will increase from 100 to 200 meters.Thus, the speed of mutual removal is proportional to the distance.Note that after the expansion of the rows, the cosmological principle remains valid: the "galaxies-soldiers" are still distributed evenly, and the same proportions between different mutual distances. The only drawback of our comparison is that in practice one of the soldiers always stands motionless in the center of the square, while the rest scatter at speeds that are greater, the greater the distance from them to the center. In space, however, there are no milestones against which absolute measurements of velocity could be made; We are deprived of such an opportunity by the theory of relativity: everyone can compare his movement only with the movement of those walking next to him, and at the same time it will seem to him that they are running away from him. We see, therefore, that Hubble's law ensures that the cosmological principle remains unchanged at all times, and this confirms us in the opinion that both the law and the principle itself are indeed valid. Another example of an intuitive image is the explosion of a bomb; in this case, the faster the fragment flies, the farther it will fly. A moment after the explosion itself, we see that the fragments are distributed in accordance with Hubble's law, that is, their speeds are proportional to their distances. Here, however, the cosmological principle is violated, because if we move far enough from the explosion site, we will not see any fragments. In this way, the most famous term in modern cosmology "big bang" is suggested. According to these ideas, about 20 billion years ago, all the matter of the Universe was collected at one point, from which the rapid expansion of the Universe to modern sizes began. Hubble's law was almost immediately recognized in science. The significance of Hubble's discovery was highly appreciated Einstein. In January 1931, he wrote: "The new observations of Hubble and Humason about the redshift ... make it plausible that the general structure of the universe is not stationary." Hubble's discovery finally destroyed the idea that had existed since the time of Aristotle about a static, unshakable Universe. Currently, Hubble's law is used to determine the distances to distant galaxies and quasars. Author: Samin D.K.
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