I have put together a brief chronological history of quantum physics. This happened in the early 1900's in Europe. The most significant discoveries which culminated in the new quantum theory happened in the 1920's. All of the scientists involved were young men in their 20's and 30's. Planck was the oldest at 42.
By the 1930's the Nazi's had come into power and this affected the personal lives of these scientists and sometimes their personal relationships as well. By the end of the 1930's the focus in science was on the development of the atomic bomb
In 1801 the first double slit experiment was done. (Not the quantum version.) Light was directed through two slits simultaneously and an interference pattern developed. This effect would be similar to dropping two pebbles in a pond of water in close proximity and watching the ripple patterns interfere with each other. From this it was determined that light acted as a wave.
In 1899 Planck's constant was discovered. Planck's constant is E=hf. E=energy, h=Planck's constant and f is frequency. E=hf became the basis of nearly all 20th century research in physics. Planck's constant sets the quantitative scale at which quantum effects become appreciably large (Goswami, pg 36)
In 1900 Planck (age 42), discovered the law of heat radiation, named Planck's law of black body radiation. The clue that triggered the quantum revolution came not from studies of matter but from a problem in radiation. Why did hot objects emit different colors of light depending on how hot they were? ( red, white and blue) Planck postulated that the energies of the vibrating electrons that radiate the light are quantized.
In 1905 Einstein (age 26) discovered the photon which is a discrete light amount (thought to be a particle at the time it was discovered). Light is emitted and received in discrete amounts. - The photoelectric effect - This discovery validated Planck's law of black body radiation. In 1921 Einstein won a Nobel Prize for this discovery. Although Einstein contributed a great deal to quantum physics he did not like it. He was firmly on the side of material realism.
1911- Ernest Rutherford discovered the nucleus of the atom. Neils Bohr joined Rutherford in 1912 and adapted Rutherford's nuclear structure to Max Planck's quantum theory. Later with improvements as a result of Heisenberg's concepts, this atomic structure remains valid today.
1913- Neils Bohr (age 28) published his model of atomic structure. This introduced the theory of electrons traveling in orbit around the nucleus of the atom. The chemical properties of the element were largely determined by the number of electrons traveling in the outer orbit. (became the basis for the chart of the elements) He introduced the idea that an electron could drop from a higher energy orbit to a lower one, emitting a photon (light quantum) of discrete energy. The electrons "jump" between stationary states instantaneously.
In 1919 Max Planck won the Nobel Prize with his paper "The Origin and Development of Quantum Theory", In Einstein's words "This shattered the whole framework of classical mechanics."
WWI -The first world war slowed scientific discovery but after the war things gained momentum rapidly.
1922 Niels Bohr won the Nobel Prize for his work on the structure of atoms.
1923 Louis DeBroglie : Wave - Particle Duality - This was DeBroglie's doctoral thesis. It was finally approved by Einstein. The particle behavior of light should have its counterpart in the wave behavior of particles. He proposed that electrons which circled an atom were actually waves in confinement. This would be like guitar strings. They produce discrete stationary wave patterns. There is waviness but the strings do not propogate in space. This was groundbreaking as it proposed that matter (as well as light) is comprised of waves. In 1926 Erwin Schrodinger took De Broglie's idea and created a wave equation for matter.
1924 - Satyendra Bose tried to explain the Planck radiation law. He treated light as if it were a gas of mass-less particles (now called photons).
Bose-Einstein distribution - How energy is shared by the particles in a gas. Einstein immediately applied Bose's reasoning to a real gas of massive particles and obtained a new law known as the Bose-Einstein distribution.
"In the 3 year period from 1925 to 1928 a series of events occurred which resulted in a scientific revolution." (www.4physics.com)
1925 - Max Born and Werner Heisenberg -The theory of quantum mechanics was formulated, this completed the development of quantum theory.
1925 -Max Born and Pasqual Jordan paper on the matrix mechanics representation of Quantum Mechanics.
1925 - All three authors submit a final paper on matrix mechanics - Heisenberg, Born and Jordan. Einstein recommends the three of them for the Nobel Prize in 1928. This did not happen as it should have.
1926 - Schrodinger's wave equation for which he shared the 1933 Nobel Prize. This equation is the cornerstone of the mathematics that replaced Newton's laws in the new physics. (Goswami, pg. 35) I have not included the math here as it is too complex for the content of this site
Copenhagen Interpretation - Named for the location of Bohrs Institute for Theoretical Physics in Copenhagen. Max Born, Werner Heisenberg, and Niels Bohr's interpretation of quantum theory. Quantum objects are waves. These waves are interpreted probabilistically. We determine their attributes somewhat uncertainly and understand them complementarily. Discontinuity and quantum jumps, the collapse of the wave upon observation are fundamental aspects of the behavior of a quantum object. Quantum objects are inseparable. Large objects (classical physics) act as classical physics would predict.
1927 -Bohr introduced his complementarity principle which constitutes the basis for the Copenhagen interpretation of quantum mechanics (Bohr’s scientific institute was in Copenhagen) this principle shows that items can be separately analyzed as having contradictory properties. Light behaves either as a wave or a particle depending on the experimental framework. These are two mutually exclusive properties. This was a way to resolve quantum paradoxes.
1927 - Werner Heisenberg developed his uncertainty principle - We cannot simultaneously determine with certainty both the position and the velocity (momentum) of an electron. Any effort to measure one accurately blurs our knowledge of the other. (Goswami pg 37)
1929 - Heisenberg and Wolfgang Pauli submit 2 papers laying the foundation for quantum field theory.
1932 - James Chadwick discovers the Neutron.
1932 Heisenberg won the Nobel prize for his neutron-proton model of the nucleus. This should have been shared by Born and Jordan. Einstein had nominated the three of them together. However there were some political issues due to the rise of the Nazi Party which probably affected the final outcome.
1933 Nobel prize was shared by Schrodinger and Dirac for "the discovery of new productive forms of atomic theory." (www.NobelPrize.org)
1933 - Paul A. M. Dirac shares the Nobel prize for his relativistic wave equation of quantum mechanics (paper 1928) This explained electron spins and implied the existence of positive electrons (aka anti-matter, later named positrons). Dirac laid the foundations of quantum field theory by providing a quantum description of the electromagnetic field.
The importance of Dirac's work lies essentially in his famous wave equation, which introduced special relativity into Schrodinger's equation. Taking into account the fact that, mathematically speaking, relativity theory and quantum theory are not only distinct from each other, but also oppose each other, Dirac's work could be considered a fruitful reconciliation between the two theories.
1933 - Heisenberg presents his theory of the positron building on Dirac's work.
1938 - Fermi received the Nobel Prize at the age of 37 for his "demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons". Fermi is often referred to as the father of the atomic bomb.
I am ending my history of quantum physics here. Developments that followed were primarily related to the development of the atomic bomb. WWII had an effect on the lives of most of the prominent scientists because of what was happening in Europe. Several of them had to relocate.
www.4physics.com - Historical overview from which some of this history is taken.
Amit Goswami, The Self Aware Universe, N.Y. Tarcher/Putnam, 1993.
©Robyn S. Levy