Yesterday marked the 114th anniversary of the birth of Paul Adrien Maurice Dirac, one of the world’s greatest ever theoretical physicists. Born on the 8th of August 1902 in Bristol (UK), Dirac studied for his PhD at St. John’s college Cambridge University, where he would subsequently discover the equation that now bears his name,
iγ·∂ψ = mψ .
The Dirac equation is a solution to the problem of describing an electron in a way that is consistent with both quantum mechanics and Einstein’s theory of relativity. His solution was unique in its natural inclusion of the electron “spin”, which had to otherwise be invoked to account for fine structure in atomic spectra. His brilliant contemporary, Wolfgang Pauli, described Dirac’s thinking as acrobatic. And several of Dirac’s theories are regarded as among the most beautiful and elegant of modern physics.
An important prediction of the Dirac equation is the existence of the anti-electron (also known as the positron). This particle is equal in mass to the more familiar electron, but has the opposite electric charge. Dirac published his theory of the anti-electron in 1931 – two years before “the positive electron” was discovered by Carl Anderson. Dirac accurately mused that the anti-proton might also exist, and most physicists now believe that all particles posses an antimatter counterpart. But antimatter is apparently – and as yet inexplicably – much scarcer than matter.
In 1933 Dirac shared the Nobel prize in physics with Erwin Schrödinger “for the discovery of new productive forms of atomic theory”. Dirac died aged 82 in 1984. He’s commemorated in Westminster Abbey by an inscription in the Nave, not far from Newton’s monument. Separated in life by more than two centuries, Paul Dirac and Sir Isaac Newton are arguably the fathers of antimatter and gravity.
The Strangest Man by Graham Farmelo is a fascinating account of Dirac’s life and work.