Late 19th - early 20th century were marked by the birth of new scientific concepts that radically changed the usual picture of the world. In 1887, American physicists Edward Morley and Albert Michelson wanted to experimentally confirm the traditional idea that light (that is, electromagnetic oscillations) propagates in a special substance - ether, just as sound waves travel through space through air.
Without even assuming that their experience would show the completely opposite result, the scientists directed a light beam onto a translucent plate located at an angle of 45 ° to the light source. The beam bifurcated, partly passing through the plate, and partly being reflected from it at right angles to the source. Propagating with the same frequency, both beams were reflected from the perpendicular mirrors and returned to the plate. One reflected from it, the other passed through, and when one beam was superimposed on another, interference fringes appeared on the screen. If the light moved in some substance, the so-called ethereal wind would have to shift the interference pattern, but nothing has changed over six months of observations. So Michelson and Morley realized that ether does not exist, and light can spread even in a vacuum - absolute emptiness. This discredited the basic position of classical Newtonian mechanics about the existence of absolute space - the fundamental frame of reference, relative to which the ether is at rest.
Another "stone" in the direction of classical physics was the equations of the Scottish scientist James Maxwell, which showed that light moves with a limited speed, which does not depend on the "source-observer" system. These discoveries served as the impetus for the formation of two completely innovative theories: quantum and the theory of relativity.
In 1896 the German physicist Max Planck (1858-1947) began to study heat rays - in particular, their dependence on the texture and color of the emitting object. Planck's interest in this topic arose in connection with the thought experiment of his compatriot Gustav Kirchhoff, carried out in 1859. Kirchhoff created a model of an absolutely black body, which is an ideal opaque container that absorbs all rays falling on it and does not let them out, “forcing »Repeatedly bounce off the walls and lose energy. But if this body is heated, it will begin to emit radiation, and the higher the heating temperature, the shorter the ray wavelengths, which means that the rays will pass from the invisible spectrum to the visible one. The body will first turn red and then turn white, because its radiation will combine the entire spectrum. The emitted and absorbed radiation will come into equilibrium, that is, their parameters will become the same and independent of the substance from which the body is made - energy will be absorbed and released in equal amounts. The only factor that can affect the radiation spectrum is body temperature.
After learning about Kirchhoff's findings, many scientists set out to measure the temperature of a black body and the corresponding wavelengths of the emitted rays. Of course, they did it using the methods of classical physics - and … they came to a dead end, getting completely meaningless results. With an increase in body temperature and, accordingly, a decrease in the wavelength of radiation to the ultraviolet spectrum, the intensity of wave oscillations (energy density) increased to infinity. Meanwhile, experiments showed the opposite. Indeed, does an incandescent lamp shine brighter than an X-ray tube? And is it possible to heat a black cube so that it becomes radioactive?
To eliminate this paradox, called the ultraviolet catastrophe, Planck in 1900 found an original explanation for how the radiation energy of a black body behaves. The scientist suggested that the atoms, vibrating, release energy in strictly dosed portions - quanta, and the shorter the wave and the higher the vibration frequency, the larger the quantum, and vice versa. To describe the quantum, Planck derived a formula according to which the amount of energy can be determined by the product of the frequency of the wave and the quantum of action (constant equal to 6.62 × 10-34 J / s).
In December, the scientist presented his theory to members of the German Physical Society, and this event marked the beginning of quantum physics and mechanics. However, due to the lack of confirmation by real experiments, Planck's discovery aroused interest far from immediately. And the scientist himself at first presented quanta not as material particles, but as a mathematical abstraction. Only five years later, when Einstein found a justification for the photoelectric effect (knocking out electrons from a substance under the influence of light), explaining this phenomenon by "dosing" of the radiated energy, Planck's formula found its application. Then it became clear to everyone that these were not empty speculations, but a description of a real phenomenon at the micro level.
By the way, the author of the theory of relativity himself highly appreciated the work of his colleague. According to Einstein, Planck's merit lies in proving that not only matter is made up of particles, but also energy. Moreover, Planck found a quantum of action - a constant linking the frequency of radiation with the magnitude of its energy, and this discovery turned physics upside down, starting its development in a different direction. Einstein predicted that it would be thanks to Planck's theory that it would be possible to create a model of the atom and understand how energy behaves when atoms and molecules decay. According to the great physicist, Planck destroyed the foundations of Newtonian mechanics and showed a new way in understanding the world order.
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Now Planck's constant is used in all equations and formulas of quantum mechanics, dividing the macrocosm, living according to Newton's laws, and the microcosm, where quantum laws work. For example, this coefficient determines the scale at which the Heisenberg uncertainty principle operates - that is, the inability to predict the properties and behavior of elementary particles. Indeed, in the quantum world, all objects have a dual nature, arising in two places at the same time, manifesting themselves as a particle at one point and as a wave at another, etc.
Thus, having discovered quanta, Max Planck founded quantum physics, capable of explaining phenomena at the atomic and molecular levels, which is beyond the power of classical physics. His theory became the basis for the further development of this scientific field.