One hudred years ago, Einstein was interested in how things look to moving observers, while Bohr was worrying about why the hydogen energy levels are discrete. They are discrete because the electron orits are standing waves. Thus, there is a welldefined problem.
How would the standing waves look to moving observers?Click here for the definition of the problem. 
Many distinguished physicists worried about this problem. Among them were Dirac, Wigner,
and Feynman.

Three Wise Men from the 20th Century ? Click here for a story 
Three papersClick herefor detailed references. 
Dirac

Wigner

Feynman

Major Contributions  cnumber timeenergy uncertainty, harmonic oscillators, lightcone coordinate system.  Little groups defining internal spacetime symmetries.  Parton model, oscillator model for Regge trajectories, in addition to Feynman diagrams. 
Favorite language  Poems. Dirac's writings are like poems.  Twobytwo matrices.  Diagrams and pictures. 
Soft spots  Lack of figures and illustrations. Lack of physical examples.  Lack of concrete physical examples. His 1939 paper could not explain Maxwell's equations.  Sloppy mathematics. 
One Mathematics 
The mathematics of two coupled oscillators is well known. All of the above
papers can be understood in terms of this mathematical instrument.

If we assemble these nine paper, we then end up with
Further Contents of Einstein's E = mc^{2 }


copyright@2012 by Y. S. Kim, unless otherwise specified. The Photo of Dirac by Bulent Atalay, and photo of Wigner by Y. S. Kim (1988). Feynman's photo is from the main lobby of the Feynman Computing Center at the Fermi National Accelerator Laboratory, Batavia, Illinois, USA.