Quantum_ Einstein, Bohr and the Great Debate About the Nature of Reality - Manjit Kumar [52]
Since the physics of Newton and Maxwell had been impeccably applied and forecast electrons crashing into the nucleus, Bohr accepted that the 'question of stability must therefore be treated from a different point of view'.12 He understood that to save Rutherford's atom would require a 'radical change', and he turned to the quantum discovered by a reluctant Planck and championed by Einstein.13 The fact that in the interaction between radiation and matter, energy was absorbed and emitted in packets of varying size rather than continuously, was something beyond the realm of time-honoured 'classical' physics. Even though like almost everyone else he did not believe in Einstein's light-quanta, it was clear to Bohr that the atom 'was in some way regulated by the quantum'.14 But in September 1912 he had no idea how.
All his life, Bohr loved to read detective stories. Like any good private eye, he looked for clues at the crime scene. The first were the predictions of instability. Certain that Rutherford's atom was stable, Bohr came up with an idea that proved crucial to his ongoing investigation: the concept of stationary states. Planck had constructed his blackbody formula to explain the available experimental data. Only then did he attempt to derive his equation and in the process stumbled across the quantum. Bohr adopted a similar strategy. He would begin by rebuilding Rutherford's atomic model so that electrons did not radiate energy as they orbited the nucleus. Only later would he try to justify what he had done.
Classical physics placed no restrictions on an electron's orbit inside an atom. But Bohr did. Like an architect designing a building to the strict requirements of a client, he restricted electrons to certain 'special' orbits in which they could not continuously emit radiation and spiral into the nucleus. It was a stroke of genius. Bohr believed that certain laws of physics were not valid in the atomic world and so he 'quantised' electron orbits. Just as Planck had quantised the absorption and emission of energy by his imaginary oscillators so as to derive his blackbody equation, Bohr abandoned the accepted notion that an electron could orbit an atomic nucleus at any given distance. An electron, he argued, could occupy only a few select orbits, the 'stationary states', out of all the possible orbits allowed by classical physics.
It was a condition that Bohr was perfectly entitled to impose as a theorist trying to piece together a viable working atomic model. It was a radical proposal, and for the moment all he had was an unconvincing circular argument that contradicted established physics – electrons occupied special orbits in which they did not radiate energy; electrons did not radiate energy because they occupied special orbits. Unless he could offer a real physical explanation for his stationary states, the permissible electron orbits, they would be dismissed as nothing more than theoretical scaffolding erected to hold up a discredited atomic structure.
'I hope to be able to finish the paper in a few weeks,' Bohr wrote to Rutherford at the beginning of November.15 Reading the letter and sensing Bohr's mounting anxiety, Rutherford replied that there was no reason 'to feel pressed to publish in a hurry' since it was unlikely anyone else was working along the same lines.16 Bohr was unconvinced as the weeks passed without success. If others were not already actively engaged in trying to solve the mystery of the atom, then it was only a matter of time. Struggling