Key Events in the History of Quantum Mechanics

1. James Clerk Maxwell argues that the positions and velocities of molecules are initially at random. Later he will introduce the Maxwell distribution curve plotting the number of molecules vs their respective velocities for given temperatures.
2. Ludwig Boltzmann introduces the field of Statistical Mechanics. Introduces theorem of the equipartition of energy.
3. Blackbody Radiation arises. Experimental work carried out by Wilhelm Wien.
4. Lord Rayleigh and James Jeans introduce the concept of the ultra-violet catastrophe.
5. Max Planck saves the day (and opens up a can of worms) by introducing concept of discrete units of energy quanta where each quanta has an energy = hf. h = Planck’s constant and f = frequency of the quanta (or photon in the case of light).
6. Phillip Lennard works on problem of photo-electric effect.
7. Albert Einstein explains how photons of light above a threshold frequency can liberate electrons and provide them with kinetic energy. He will win a Nobel Prize for his work.
8. Joseph von Fraunhofer discovers dark lines in solar spectrum (later Fraunhofer lines). These will become the basis for Astrophysical spectroscopy.
9. Gustav Kirchoff discovers Helium on the sun using Fraunhofer solar spectrum.
10. J.J. Thompsopn discovers the electron.
11. Ernest Rutherford discovers positive nucleus of atom. Experiments carried out by Geiger and Marsden.
12. Arthur Compton works out the momentum of a photon. Shows the effect of photon scattering and wavelength shift.
13. Niels Bohr explains Bright Line Light Spectra. Introduces concept of probability waves. Explains working of Hydrogen atom. Bohr uses relies heavily on analysis of hydrogen spectrum by Swiss math teacher Johann Balmer.
14. Most scientists will grow to accept probability description. A noteable exception is Albert Einstein.
15. Pieter Zeeman demonstrates the Zeeman Effect ie. The extraneous spectral lines which appear when excited atoms are placed in a magnetic field.
16. Bohr introduces the n, k and m quantum numbers. N = orbit size, k = orbit shape and m = orbit direction.
17. Wolfgang Pauli speaks about the Pauli Exclusion Principle. Adds fourth quantum # for spin. No two electrons can have the same set of four quantum numbers.
18. Bohr uses quantum Mechanics to explain the nature of Mendeleev’s Periodic Table. Concept of Closed and Open Electron shells introduced.
19. Wave Particle/Duality appears to be winning out in the battle to describe the nature of light.
20. Louis De Broglie introduces the concept of Matter Waves.
21. G. P. Thomson proves that Matter Waves do exist.
22. Werner Heisenberg introduces Matrix Mechanics. Introduces Uncertainty Principle. Probable death of the Philosophy of Determinism.
23. Max Born and Erwin Schrodinger further develop Matrix Mechanic.
24. Schrodinger introduces his famous equation – contains wave function, position and energy of photon.
25. Fourier analysis builds on Scrodinger’s work – looks at the number of nodes in a vibrating system.
26. Schrodinger argues that particles may not even exist. Wants to describe all particles as superposition of waves.
27. Henrik Lorentz argues otherwise. Wave function that Schrodinger felt did not spread out. Appears to spread out.
28. Schrodinger introduces famous cat problem.
29. Born introduces concept of quantum mechanical probability. Speaks about Probability Amplitude of an Electron.
30. Consciousness and the Collapsing Wave Function problems are addressed by Eugene Wigner.
31. Paul Dirac brings together a new solution that looks at the problems of Bohr, Einstein and Planck’s Quantum Theories.
32. Dirac Introduces Transformation Theory.
33. Birth of Quantum Electrodynamics. Richard Feynman’s field
34. Dirac uses equation to solve problem of Electron Spin.
35. Dirac predicts existence of Anti-matter.
36. Bohr speaks about complementarity.
37. Formalization of Copenhagen Interpretation.
38. Einstein speaks of his box of light.
39. EPR Challenge to Bohr.
40. The Non-Locality Issue rises to the fore.
41. Bell’s non-inequality principle argues that nature is non-local.
42. Period of New Advances: Action at a Distance, Entanglement, Qbits, String Theory, Quantum Loop Gravity.
43. The Future: We will await and see.