At the beginning of the twentieth century, the scientists thought that they had included/understood the great fundamental principles of the universe.
The atoms were the solids blocks of construction of nature; people believed in the Newtonian laws of the movement, the majority of the problems of the
physicists seemed to be solved.
Nevertheless, the theory of relativity of Einstein replacing Newtonian mechanics, the scientists realized gradually that their knowledge was far from
The field incipient from quantum mechanics was of particular interest, by completely deteriorating the fundamental precepts of physics.
Chronology of Quantum Physic :
1900 max Planck suggests that the radiations are quantifiable (they can take only values which are multiples of an elementary value called
1905 Albert Einstein, one of the rare scientists who considered the ideas of Planck seriously, proposes a quantum of light (the photon) which behaves
like a particle. The other theories of Einstein explain the equivalence of the mass and energy, the duality wave-particle of the photons, the
principle of equivalence and restricted relativity.
1909 Hans Geiger and Ernest Marsden, under the responsibility of Ernest Rutherford, send particles alpha on a gold sheet and observe great scattering
angles, which suggests the existence of a core positively charged, small and dense inside the atom. 1911 Ernest Rutherford shows the existence from
the core like result from the experiment from diffusion alpha realized by Hans Geiger and Ernest Marsden.
1912 Albert Einstein explains the curve of the space time.
1913 Niels Bohr builds the theory of the atomic structure based on quantum assumptions.
1919 Ernest Rutherford proves the existence of the proton.
1921 James Chadwick and E.S. Bieler conclude that a force of great intensity (known as strong) maintains the core plain.
1923 Arthur Compton discovers quantum nature (particulate) x-rays, confirming that the photons are particles.
1924 Louis de Broglie proposes undulatory properties for the matter.
1925 (Jan) Wolfgang Pauli formulates the principle of exclusion for the electrons inside an atom.
1925 (April) Walther Bothe and Hans Geiger show that energy and the mass are preserved in the atomic processes.
1926 Erwin Schroedinger develops the wave mechanics, which describes the behavior of the quantum systems for bosons. Max Born gives a probabilistic
interpretation of quantum mechanics. G.N. Lewis proposes the name of photon for the quantum of light.
1927 It was observed that certain materials emitted electrons (beta decay). The atom and the core having discrete energy levels, it was difficult to
include/understand how the electrons produced in this transition could have a continuous spectrum (see 1930 for the answer).
1927 Werner Heisenberg formulates the principle of uncertainty: the more you have information on the energy of a particle, the less know you over the
time during which it has this energy (and vice versa). The same principle applies with the impulse and the position.
1928 Paul Dirac combines quantum mechanics and relativity restricted to describe the electron.
1930 quantum mechanics and restricted relativity are well established. There are only three elementary particles: protons, electrons and photons. Max
Born, fascinating knowledge of the equation of Dirac, known as: "physics such as we know it will have died in six months".