Quantum_ Einstein, Bohr and the Great Debate About the Nature of Reality - Manjit Kumar [45]
An atom with stationary electrons positioned around a positive nucleus would be unstable, because the electrons with their negative charge would be irresistibly pulled towards it. If they moved around the nucleus, like planets orbiting the sun, the atom would still collapse. Newton had shown long ago that any object moving in a circle undergoes acceleration. According to Maxwell's theory of electromagnetism, if it is a charged particle, like an electron, it will continuously lose energy in the form of electromagnetic radiation as it accelerates. An orbiting electron would spiral into the nucleus within a thousandth of a billionth of a second. The very existence of the material world was compelling evidence against Rutherford's nuclear atom.
He had long been aware of what appeared to be an intractable problem. 'This necessary loss of energy from an accelerated electron,' Rutherford wrote in his 1906 book Radioactive Transformations, 'has been one of the greatest difficulties met with in endeavouring to deduce the constitution of a stable atom.'53 But in 1911 he chose to ignore the difficulty: 'The question of the stability of the atom proposed need not be considered at this stage, for this will obviously depend upon the minute structure of the atom, and on the motion of the constituent charged part.'54
Geiger's initial testing of Rutherford's scattering formula had been quick and limited in scope. Marsden now joined him in spending most of the next year conducting a more thorough investigation. By July 1912 their results confirmed the scattering formula and the main conclusions of Rutherford's theory.55 'The complete check,' Marsden recalled years later, 'was a laborious but exciting task.'56 In the process they also discovered that the charge of the nucleus, taking into account experimental error, was about half the atomic weight. With the exception of hydrogen, with an atomic weight of one, the number of electrons in all other atoms had to be approximately equal to half the atomic weight. It was now possible to nail down the number of electrons in a helium atom, for example, as two, where previously it could have been as many as four. However, this reduction in the number of electrons implied that Rutherford's atom radiated energy even more strongly than had previously been suspected.
As Rutherford recounted tales from the first Solvay conference for Bohr's benefit, he failed to mention that in Brussels neither he nor anyone else discussed his nuclear atom.
Back in Cambridge, the intellectual rapport that Bohr sought with Thomson never happened. Years later, Bohr identified one possible reason for the failure: 'I had no great knowledge of English and therefore I did not know how to express myself. And I could say only that this is incorrect. And he was not interested in the accusation that it was not correct.'57 Infamous for neglecting papers and letters from students and colleagues alike, Thomson was also no longer actively engaged in electron physics.
Increasingly disenchanted, Bohr met Rutherford again at the Cavendish research students' annual dinner. Held in early December, it was a rowdy, informal affair with toasts, songs and limericks following a ten-course meal. Once again struck by the personality of the man, Bohr seriously began thinking about swapping Cambridge and Thomson for Manchester and Rutherford. Later that month he went to Manchester and discussed the possibility with Rutherford. A young man separated from his fiancée, Bohr desperately wanted something tangible to show for their year apart. Telling Thomson that he wanted 'to know something about radioactivity',