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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Special theory of relativity. History and essence of scientific discovery
Directory / The most important scientific discoveries In 1905, in the German scientific journal Annalen der Physicist, a short article of 30 printed pages appeared in a twenty-six-year-old Albert Einstein "On the Electrodynamics of Moving Bodies", in which the special theory of relativity was almost completely expounded, which soon made the young expert of the patent office famous. In the same year, the article "Does the inertia of a body depend on the energy contained in it?" appeared in the same journal, supplementing the first one. The special theory of relativity did not appear out of nowhere, it grew out of the solution of the electrodynamic problem of moving bodies, on which many physicists have been working since the middle of the XNUMXth century. They sought to discover the existence of an ether-medium in which electromagnetic waves propagated. It was assumed that the ether penetrates through all bodies, but does not take part in their movement. Various models of the luminiferous ether were built, hypotheses were put forward regarding its properties. It seemed that the motionless ether could serve as that absolutely resting frame of reference, relative to which Newton considered the "true" motions of bodies. According to Newton's view, there are "normal clocks" in the Universe that count the course of "absolute time" from any point. In addition, there is "absolute motion", i.e., "the movement of a body from one absolute place to another absolute place." For two hundred years, Newton's principles were considered correct and unshakable. No physicist has questioned them. Ernst Mach was the first to openly criticize Newton's principles. He began his scientific career at the Department of Experimental Physics and had his own laboratory in Austria. Mach conducted experiments with sound waves and studied the phenomenon of inertia. Mach tried to refute the concepts of "absolute space", "absolute motion", "absolute time". Einstein was familiar with the work of Mach, and this acquaintance played an important role in his work on the theory of relativity. In experimental physics, Newtonian dogmas were also called into question. The earth moves in its orbit around the sun. In turn, the solar system flies in world space. Consequently, if the light ether is at rest in "absolute space" and celestial bodies pass through it, then their movement with respect to the ether should cause a noticeable "ethereal wind" that could be detected using sensitive optical instruments. An experiment to detect the "ethereal wind" was set up in 1881 by the American Albert Michelson on the idea expressed 12 years before. Maxwell. Michelson reasoned as follows: if the globe moves through an absolutely immobile ether, then a beam of light launched from the surface of the Earth, under certain conditions, will be carried back by the "ethereal wind", which blows towards the movement of the Earth. The "ethereal wind" should arise only due to the displacement of the Earth relative to the ether. The first experimental setup was built and tested by Michelson in Berlin, all instruments were mounted on a stone slab and could be rotated as one. Then the experiments were transferred to America and carried out with the participation of Michelson's close friend and collaborator Edward Morley. Scientists have created a mirror interferometer, which could register even the weakest "aether wind". The results of all the experiments carried out both in 1881 and in 1887 denied the existence of any "ethereal wind". Michelson's experiment can still be considered one of the most famous and outstanding in the history of physics. According to Einstein himself, he was of great importance for the birth of the theory of relativity. But not all physicists agreed that the aether did not exist and that Newton's principles should not only be called into question, but also discarded forever. Dutch physicist Hendrik Lorenz in 1895 he tried to "save" the ether. He suggested that fast moving bodies experience contraction. Even before Lorentz, in 1891, the Irish physicist George Fitzgerald made a similar suggestion, which Lorentz was unaware of. Lorentz and Fitzgerald wrote that all objects "under the pressure" of the ether are flattened, shortened. The plate, on which all the devices are located, and the devices themselves are shortened. Both the globe and the people on its surface are shortened, and the magnitude of all these shortenings and flattenings is equal to such a magnitude as to balance the effect of the "ethereal wind". Scientists also introduced a correction for the propagation time of the "ethereal wind". These ideas were just speculations with little to no support. In the autumn of 1904, Henri Poincaré also tried to "save" the absolutely motionless ether. He tried to formulate Lorentz's calculations in the form of a more or less coherent theory, but this "theory" was only a formality. The greatest minds were sad, it seemed that there was no way out of this situation. But the way out was found by Albert Einstein, he brought physics out of the impasse and directed it into a new direction. Einstein, while still at school in Aarau, often conducted a thought experiment: what a person could see moving behind a light wave at the speed of light. It was this question that served as the beginning of reflections on what was later called the theory of relativity. About the beginning of his reasoning, Einstein wrote: "It was necessary to get a clear idea of what the spatial coordinates and time of some event mean in physics." Einstein began by exploring the concept of simultaneity. Thus, Newtonian mechanics asserts that, in principle, the propagation of interactions (that is, the transmission of signals, information) with infinite speed is possible. And according to Einstein's theory, the speed of light, which is the maximum speed of signal transmission, is still finite and, moreover, has the same value for all observers of three hundred thousand kilometers per second. Therefore, the concept of "absolute simultaneity" is devoid of any physical meaning and cannot be applied. Einstein comes to the conclusion that the simultaneity of spatially separated events is relative. The reason for the relativity of simultaneity is the finiteness of the speed of propagation of signals. True, we cannot imagine this clearly, since the speed of light is much greater than the speeds with which we move. If "absolute simultaneity" is impossible, then "absolute time" cannot exist, which is the same in all frames of reference. The notion of "absolute time", which flows once and for all at a given pace, completely independent of matter and its movement, turns out to be wrong. Each frame of reference has its own "local time". Einstein's doctrine of time was a completely new step in science. "Absolute time" was discarded, and since time and motion are closely related, it became necessary to eliminate the Newtonian concept of "absolute motion". This is what Einstein did. The first and main postulate of Einstein's theory - the principle of relativity - states that in all frames of reference moving uniformly and rectilinearly with respect to each other, the same laws of nature operate. Thus, the principle of relativity of classical mechanics is extrapolated to all processes in nature, including electromagnetic ones. If a transition from one frame of reference to another is necessary, then Lorentz transformations must be used. Einstein named these equations as a sign of deep respect for the work of his predecessor. Einstein in his theory of relativity replaced the light ether with an electromagnetic field. Many scientists reacted very painfully to such a turn, they could not come to terms with the fact that the ether does not exist. Even the great Dutchman Lorentz believed in the existence of the ether until his death. Einstein's second postulate states that the speed of light in vacuum is the same for all inertial frames of reference. It does not depend on either the speed of the source or the speed of the receiver of the light signal. The speed of light is the upper limit for all processes occurring in nature. The speed of light is the limiting speed, none of the processes in nature can have a speed greater than the speed of light. Two famous paradoxes or consequences follow from the constancy of the speed of light: the relativity of distances and the relativity of time intervals. The relativity of distances lies in the fact that the distance is not an absolute value, but depends on the speed of the body relative to a given frame of reference. The dimensions of fast-moving bodies are reduced in comparison with the length of bodies at rest. When approaching the speed of the body to the speed of light, its dimensions will approach zero! Lorentz also expressed something similar when he tried to "save" the ether in Michelson's experiment. The relativity of time intervals consists in slowing down the rate of clocks in a fast-moving frame compared to clocks in a resting reference frame relative to the first one. The effects described above are called relativistic by physicists, i.e. they are observed at speeds close to the speed of light. What will happen if we actually try to accelerate a material body to speeds close to the speed of light? The theory of relativity asserts the equivalence of mass and energy in accordance with the now famous formula, which can be expressed in words as follows: "Energy is equal to mass times the square of the speed of light." Initially, an increase in the energy of the body is accompanied by a subtle increase in the mass and, consequently, inertia of the body. Therefore, it becomes a little bit more difficult to accelerate it further. As the speed approaches the speed of light, this effect, becoming more and more impressive, makes it impossible to overcome the speed of light. Einstein's formula received brilliant confirmation in the late thirties in the reactions of uranium fission. At the same time, one thousandth of the total mass disappeared in order to be fully revealed again in the form of atomic energy. Even in ordinary chemical reactions, the Einstein ratio is observed, but the quantities of matter that appear or disappear during the reaction are less than one ten-billionth of the total mass, so it is impossible to detect them even with very accurate balances. It is important to emphasize that in the special theory of relativity, uniform motion is considered, i.e., motion at a constant speed, at which the direction of motion does not change. If the movement occurs with an acceleration due to external forces, such as gravitational attraction, then the special theory of relativity can no longer be applied. What Einstein discovered and introduced into physics was truly revolutionary, so few physicists immediately realized that the special theory of relativity is a brilliant discovery. Among those who understood was Max Planck, who wrote: "Einstein's concept of time surpasses in boldness everything that up to this time has been created in speculative natural science and even in the philosophical theory of knowledge." In 1908, the German mathematician Hermann Minkowski, who taught Einstein at the Zurich Polytechnic, created a mathematical apparatus for the special theory of relativity. In his famous speech at the Congress of German Naturalists and Physicians on September 21, 1908, Minkowski said: “The concepts of space and time that I am about to develop before you have grown on the soil of experimental physics. This is their strength. They will lead to radical consequences. From now on space itself and time itself completely disappear into the realm of shadows, and only a kind of union of both of these concepts retains an independent existence. Since then, the "Minkowski world" has become an integral part of the special theory of relativity. Einstein once said to James Frank: "Why exactly did I create the theory of relativity? When I ask myself this question, it seems to me that the reason is as follows. A normal adult does not think about the problem of space and time at all. According to him, he has already thought about this problem in childhood. I developed intellectually so slowly that space and time occupied my thoughts when I became an adult. Naturally, I could penetrate deeper into the problem than a child with normal inclinations." Einstein did not have the "adult" confidence that the global problems of the world had already been solved. This feeling was not repressed by the accumulation of special knowledge and interests. He thought about the concept of motion and returned to the idea inherent in the childhood of mankind - to the ancient idea of relativity, which was later obscured by the concept of ether as an absolute reference body. When the concept of ether was discarded, Einstein concluded that motion cannot be absolute. Author: Samin D.K.
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