Thus Planck begat the quantum theory.

The red dots correspond to measurements made with Planck; these are shown with error bars that account for measurement errors as well as for an estimate of the uncertainty that is due to the limited number of points in the sky at which it is possible to perform measurements. This so-called cosmic variance is an unavoidable effect that becomes most significant at larger angular scales.

Thus Planck's description of the average resonator entropy became

And a spot of light emerging from a hot stove led them to the quantum theory.

Planck's Quantum Hypothesis - PowerPoint PPT …

The atom will be completely stable in the state with the smallestorbit, since there is no orbit of lower energy into which the electron canjump.Bohr's starting point was to realize that classical mechanics by itselfcould never explain the atom's stability.

Planck's quantum theory is compatible with the experimental data ..

Thus the remarkable conclusion is reached that the relation does not depend on the nature of the resonator, in particular, not upon its damping coefficient - a very gratifying and welcome circumstance to me, since it allowed the whole problem to be simplified in so far that the energy of radiation could be replaced by the energy of the resonator.

Did those facts offer clues to the knowledge of how Nature makes light and why it does so?

Planck’s Theory of Radiation | SpringerLink

In 1800 Friedrich William Herschel (1738 Nov 15 - 1822 Aug 25), the man who discovered Uranus, added another fact to Humanity's knowledge of light, another clue to the answer to the question.

discussion of Planck’s theory of radiation.

Bohr noticed,however, that the quantum constant formulated by the German physicist MaxPlanck has dimensions which, when combined with the mass and charge of theelectron, produce a measure of length.

Planck’s law and light quantum hypothesis - …

Physicists eventually came to call that special manifestation of light cavity (Hohlraum) radiation and then they found that they could give it another name when they discovered that it represents a fundamental problem in the physics of heat and light.

Consequences of Plancks hypothesis.

Fraunhofer passed a collimated beam of light through a narrow slit and then sent the light from the slit into a glass prism whose axis of symmetry ran parallel to the slit.

This encouraged Bohr to use Planck's constantin searching for a theory of the atom.

Planck's Quantum Theory - YouTube

The (plural "quanta") was then just used as a label for a unit of some quantity. In 1905 talk of a light quantum would be understood to be nothing more than talk of a "light unit."

Theenergy quantum is related to the frequency of the light by a newfundamental constant, h.

Science stream: Planck's Quantum Hypothesis

The liberation of quanta of light by electronic impulses is the converse of the emission of electrons by projection of light, Röntgen or Gamma rays, and here, again, the quanta of energy determined from the quantum of action and the frequency of oscillations play a characteristic part in the same way as we have seen above, in that the velocity of the electrons emitted does not depend on the intensity of the radiation, but on the wavelength of the light emitted.

With Planck's hypothesis, however, theradiation can occur only in quantum amounts of energy.

Planck's quantum hypothesis proves that a body can't …

As Newton had done, Herschel used a prism to spread sunlight into the multi-colored spectrum and then he put a thermometer into that rainbow to measure how much of the sun's heat came in each color.