Pople On Dirac's Famous Remark

The Schrodinger equation is easily solved for the hydrogen atom and found to give results identical to the earlier treatment of Bohr. With inclusion of the relativistic corrections via the Dirac equation, almost perfect agreement was found with experimental spectroscopic data. However, exact solutions for any other system was not found possible, leading to a famous remark by Dirac in 1929:

"The fundamental laws necessary for the mathematical treatment of a large part of physics and the whole of chemistry are thus completely known, and the difficulty lies only in the fact that application of these laws leads to equations that are too complex to be solved."

This was a cry both of triumph and of despair. It marked the end of the process of fundamental discovery in chemistry but left a colossal mathematical task of implementation. In retrospect, the implied finality of the claim seems excessively bold.

In 1929, there had only been one preliminary approximate quantum-mechanical calculation on the hydrogen molecule by Heitler and London, leading to a value of the bond energy of only about 70% of the experimental value. Nevertheless, the physicists were highly confident and most moved on to study the internal structure of the nucleus during the 1930s. In fact, their boldness was apparently justified, for no significant failure of the full Schrodinger-Dirac treatment has ever been demonstrated.


Nobel Lecture: Quantum chemical models
John A. Pople
Reviews of Modern Physics, Vol. 71, No. 5, October 1999, page 1287.