In 1938, the British astronomer Arthur Eddington hit on the idea that the fine structure constant α, which had been measured at approximately 1/136, should be exactly 1/136. He based this on aesthetic and numerological arguments. In his talk "The Philosophy of Physical Science", given as the 1938 Tarner Lecture at Trinity College, Cambridge, he stated:

'I believe there are 15 747 724 136 275 002 577 605 653 961 181 555 468 044 717 914 527 116 709 366 231 425 076 185 631 031 296 296 protons in the universe and the same number of electrons.'

This number, , or about , came to be known as the Eddington number.

Improved measurements of α later yielded values closer to 1/137, whereupon Eddington changed his 'proof' to show that α had to be exactly 1/137. The modern value for the fine structure constant stands at α = 1/137.03599976(50), definitely not a reciprocal integer.

See also

• Eddington-Dirac number