Предполагам, че когато е писано това, хората са били по-оптимистично настроени относно квантуването на гравитацията.
Ето цитат от една биография на Дирак.
Dirac began his talk by making it clear that he was not going to comment on the particle physics in fashion but about the electromagnetic and gravitational interactions, both known for centuries but still not fully understood. Everyone in the audience knew that Maxwell’s field theory of electromagnetism predicted the existence of electromagnetic waves, including visible light, and that the energy of the field comes in quanta, known as photons. By a similar token, Einstein had shown that the general theory of relativity predicts the existence of gravitational waves. Dirac announced that his study of the gravitational field’s energy indicated that it is delivered in separate quanta, which he called ‘gravitons’, a long-neglected term first introduced a quarter of a century before in the journal Under the Banner of Marxism. After Dirac reintroduced the name, it stuck. These particles will be much harder to detect than photons, he pointed out, but experimenters should lose no time in beginning the hunt for them. He gave the impression to the New York Times journalist Robert Plumb that this was an important prediction; the next day, Plumb’s report appeared on the front page: ‘[Dirac] believed that his postulation at this time was in the same category as his postulation of positive electrons a quarter of a century ago.’
Dirac did not succeed in quantising the general theory of relativity, but his Hamiltonian method turned out to be his most influential contribution to the theory. His approach, and similar techniques developed independently by other physicists, enabled Einstein’s equations to be conveniently set out in a comparatively simple form, especially in situations when gravitational fields change rapidly. This excursion by Dirac into relativity theory looked odd to most physicists. In the late 1950s, the development of the general theory of relativity was a cottage industry by comparison with the industrial scale of particle physics. Relativity was an unfashionable subject for theorists, and Dirac was one of the few who thought it important to develop it and to find a single theoretical framework to understand...
gravity and electromagnetism.