Today we will talk about the essence of such a concept as "ultraviolet catastrophe": why this paradox appeared and whether there are ways to resolve it.
Classical physics
Before the advent of the quantum, the world of natural science was dominated by classical physics. Of course, mathematics has always been considered the main one. However, algebra and geometry are most often used as applied sciences. Classical physics explores how bodies behave when heated, expanded, and hit. It describes the transformation of energy from kinetic to internal, talks about such concepts as work and power. It is in this area that the answer to the question of how the ultraviolet catastrophe in physics arose.
At some point, all these phenomena were so well studied that it seemed that there was nothing more to discover! It got to the point that talented young people were advised to go to mathematicians or biologists, since breakthroughs are possible only in these areas of science. But the ultraviolet catastrophe and the harmonization of practice with theory proved the fallacy of such ideas.
Heat radiation
Classical physics and paradoxes were not deprived. For example, thermal radiation is the quanta of the electromagnetic field that arise in heated bodies. Internal energy turns into light. According to classical physics, the radiation of a heated body is a continuous spectrum, and its maximum depends on temperature: the lower the thermometer reading, the “redder” the most intense light. Now we will directly approach what is called the ultraviolet catastrophe.
Terminator and thermal radiation
An example of thermal radiation is heated and molten metals. Terminator films often feature industrial facilities. In the most touching second part of the epic, the iron machine plunges into a bath of gurgling cast iron. And this lake is red. So, this shade corresponds to the maximum radiation of cast iron with a certain temperature. This means that such a value is not the highest of all possible, because the red photon has the smallest wavelength. It is worth remembering: liquid metal radiates energy in the infrared, and in the visible, and in the ultraviolet region. Only there are very few photons other than red.
Perfect black body
To obtain the spectral power density of the radiation of a heated substance, the black body approximation is used. The term sounds scary, but in fact it is very useful in physics and is not so rare in reality. So, a completely black body is an object that does not “release” the objects that have fallen to it.photons. Moreover, its color (spectrum) depends on temperature. A rough approximation of a completely black body would be a cube, in one side of which there is a hole less than ten percent of the area of the entire figure. Example: windows in apartments of ordinary high-rise buildings. That's why they appear black.
Rayleigh-Jeans
This formula describes the radiation of a black body, based only on data available to classical physics:
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u(ω, T)=kTω2/π2c3, where
u is just the spectral density of energy luminosity, ω is the radiation frequency, kT is the vibration energy.
If the wavelengths are large, then the values are plausible and agree well with experiment. But as soon as we cross the line of visible radiation and enter the ultraviolet zone of the electromagnetic spectrum, the energies reach incredible values. In addition, when integrating the formula over frequency from zero to infinity, an infinite value is obtained! This fact reveals the essence of the ultraviolet catastrophe: if some body is heated well enough, its energy will be enough to destroy the universe.
Planck and his quantum
Many scientists have tried to work around this paradox. A breakthrough led science out of the impasse, an almost intuitive step into the unknown. Planck's hypothesis helped to overcome the paradox of the ultraviolet catastrophe. Planck's formula for the frequency distribution of black body radiation contained the concept"quantum". The scientist himself defined it as a very small single action of the system on the surrounding world. Now a quantum is the smallest indivisible portion of some physical quantities.
Quantas come in many forms:
- electromagnetic field (photon, including in a rainbow);
- vector field (gluon determines the existence of strong interaction);
- gravitational field (graviton is still a purely hypothetical particle, which is in the calculations, but it has not yet been found experimentally);
- Higgs fields (the Higgs boson was experimentally discovered not so long ago in the Large Hadron Collider, and even people very far from science rejoiced at its discovery);
- synchronous motion of atoms of the lattice of a solid body (phonon).
Schrödinger's cat and Maxwell's demon
The discovery of the quantum led to very significant consequences: a fundamentally new branch of physics was created. Quantum mechanics, optics, field theory caused an explosion of scientific discoveries. Eminent scientists discovered or rewrote laws. The fact of quantization of systems of elementary particles helped explain why the Maxwell demon cannot exist (in fact, three explanations have been proposed). However, Max Planck himself did not accept the fundamental nature of his discovery for a very long time. He believed that a quantum is a convenient mathematical way to express a certain thought, but no more. Moreover, the scientist laughed at the school of new physicists. Therefore, M. Planck came up with an unsolvable, as it seemed to him, paradoxabout Schrödinger's cat. The poor beast was both alive and dead at the same time, which is impossible to imagine. But even such a task has a quite clear explanation within the framework of quantum physics, and the relatively young science itself is already striding across the planet with might and main.
