The fathers of quantum mechanics: 1900, Max Planck discovered the notion of quanta

Max Planck: Discover the notion of quanta (1900)

Whether to designate the father of the fathers of quantum mechanics, Max Planck did the trick. Recall that this mechanism appeared around 1900, when it was realized the limitations of Newtonian mechanics; mechanical walking well on our scale (or more precisely to scale apples), but was out of breath at the microscopic level (those atoms), eventually say anything!



Planck was born in Kiel, near Strasbourg, in the middle of the nineteenth century, in a family filled with priests and law professors. He hesitated a long time, but it was much physics that drew in Munich and Berlin. He began to become known by rejecting the principles emerging from its precursors, in particular refuting the idea that the material could be discontinuous. Recall that the concept of atom was so recent. It was enunciated in 1800 by Joe Dalton (the teacher, not the robber). The idea of the electron, meanwhile, was contemporary Planck. It was thought in the beginning of the twentieth century, physics was soon completed. There remained (in the famous phrase of Lord Kelvin) two small clouds. The second cumulonimbus concerned the surprising results of experiments that had demonstrated the invariance of the speed of light. We will talk about it again. The first, who was tortured Planck was bound to the insoluble problem of black body radiation: radiation that stubbornly refused to set equations!

The black body

It has long been noticed that the temperature of an object was linked to its color. Thus, the master glassmakers, observing the color of molten glass, could they give her temperature! This relationship was independent of the nature of the object. It worked as well for glass or wood. Or, the color is a wavelength. Red corresponds to important wavelengths and blue, on the contrary, the short wavelengths. Also, it was attached to construct an equation that would provide a relationship between the wavelength and temperature. Lord Rayleigh had found a solution for the red and Wien for blue. But when we used the law Rayleigh for blue or purple, were obtained temperatures endless! But it was clear that before an oven, even with blue, we were not instantly charred by infinite temperatures. So there was a problem. They gave a name to this problem: the ultraviolet catastrophe.

Birth of the concept of quanta

Planck began fumbling and found an empirical law, a formula (based on experience) who walked to red and purple. But he did not explain. He tried again. He decided to reflect on the functioning of the material. He represented under the force of springs which were stretched and relaxed. The wavelength would be the extension of the spring and the temperature of the energy that would release. But he soon realized that to stick to its formula, the springs could not expand as they wished. The springs could only have certain lengths. It was as if they went directly from 20 centimeters to 10 centimeters, by skipping intermediate values. What seemed impossible for our springs every day seemed a common practice in the world of atoms. Micro-springs Planck energy liberated per package, by quantities per quanta. Quantum mechanics was born.

Planck did not believe in his discovery

Planck did not like the idea of discontinuous energy release. It was as if his radiator could release 10 ° C or 20 ° C but not 15 ° C! EINSTEIN do not believe not more. Yet he will himself as the same observation (discontinuity) explaining the photoelectric effect.

The war Bohr Einstein

Planck’s work would lead to the development of new physics: quantum mechanics. Mechanical in what chance had its place! A revolution ! Both sides would then compete:

  • a side Planck, Einstein and Schrödinger;
  • the other Bohr, Heisenberg and Born.

The first believed in determinism (defined by Laplace ), including at the level of atoms. It was to say that there was no effect without cause. And a cause must always produce the same effects. It was still in the sequence of ideas put by Aristotle and taken up by Descartes and Newton : There was no chance. For the latter, on the contrary, chance came in large pumps in the building physics. An effect was not necessarily preceded by a cause. And the same question could have different effects. A quantum object can pass through several paths to reach a target. Better, this object could be in different places at once! Although being the founding fathers of quantum mechanics, Einstein and Planck will never be convinced by the theories they nevertheless contribute to establish. It took until 1982 and the experiments of Alain Aspect to decide between the two sides in favor of the latter. Einstein was wrong; God played dice well!


It was from his work that the true physics of revolution will take off. Planck will give its name to a constant (h), a wall (10E-43 seconds), a physics institute, an international project (radiation measurement of the universe), a satellite observatory. It will be Nobel Prize in physics.

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