The Origin of Quantum Concepts
At the end of the nineteenth century, just when the classical theories had blossomed into beautiful and elegant formulations, new challenges troubled the scientific community. The spectroscopic methods applied to analyze the atomic and the blackbody radiations, accumulated evidences that could not be explained with the existing theories. The electromagnetic theory, that reached its summit with the Maxwell equations, at the time recognized the ether as the medium of wave propagation, even though the Michelson-Morley experiment denied it. With the discovery of electrons, in 1897, the interest in understanding the atomic structure grew up steadily to become soon a true challenge for experimental and theoretical physicists. These and other problems, underpinned a period of crisis and prolific creativity. Max Planck and Albert Einstein, are emblematic symbols of two new theories of the modern physics that grew out of the crisis: the quantum physics and the relativity theory. Both theories undermined the classical physics and introduced new concepts that not only changed physics but also pervaded and gave shape to the modern culture, dominated by the communications industry and the optoelectronic devices.