Um dos grandes físicos deste século é um homem chamado Richard Feynman, que ensina em CalTech e sabe que tanto quanto sobre a maneira que o Cosmos trabalha quanto todo o homem vivo. Feynman participou dentre uma dúzia de teóricos extraordinários e ganhou alguns prêmios, incluindo uma viagem a Suécia. Mesmo assim, gosta de dizer a todos que na física não realizou tanto quanto alguns físicos renomados,e que nós não estamos nem mesmo perto de uma teoria universal da matéria e da energia como alguns teóricos pensam. Certamente, continua Feynman, os físicos de hoje poderiam pôr um sinal especial em seus escritórios para lembra-los do quanto não sabem. A mensagem seria muito simples. Consistiria simplemnete em uma unica palavra, ou melhor, em um número: 137.
Cento e trinta e sete é o valor de um número chamado de a  constante da fina-estrutura. Esta constante, 137, é a maneira que os físicos descrevem a probabilidade que um elétron se emitirá ou absorverá um photon. Porque este é o mecanismo físico básico da eletricidade e do magnetismo, a constante da fina-estrutura tem seu próprio símbolo, a letra grega a, “alfa.”.

Agora, o alfa não é nada mais, nada menos do que o quadrado da carga do elétron dividido pela velocidade de luz cronometrada na constante de Planck. Assim neste unico número estão contidos os guts do electromagnetismo (a carga do elétron), da relativitdade (a velocidade de luz), e dos mecânicos do quantum (constante de Planck). Tudo em um simples número! Não somente isso, este número não é como a constante de gás constante ou universal gravitacional, cheia dos medidores e os quilogramas e os graus Célsio. O alfa é um número puro, dimensionless – maravilha pequena que os povos estiveram fascinados.

Physicists would like to believe that these phenomena fit together tidily in accordance with one big plan. They would like the ratio of electromagnetism, relativity, and quantum mechanics to be a number like one, or maybe two times pi. They do not like its being 137 — a prime number, for heaven“s sake!

The significance of alpha was first spelled out in 1915 by a physicist named Arnold Sommerfeld — at the time, measurement errors made the value closer to 136 — and physics ever since has been littered with efforts to explain it. the most famous attempt was that of Sir Arthur Eddington, a prominent astronomer who believed that such constants could be used to produce a theory of the universe. He built a huge 16-dimensional equation full of these constants and claimed that alpha could be calculated from the number of terms: (16² – 16) / 2 + 16 = 136.

Unfortunately, experiments quickly showed that alpha was really closer to 137. Plucky Arthur Eddington was not dismayed. He said he had forgotten to add one more factor — alpha itself — and made the value 137. For thus, Punch magazine dubbed him Sir Arthur Adding-One. But Eddington was not deterred. Proudly he proclaimed that the firmament contains exactly (137 – 1) x 2²⁵⁶ protons. Of course, the old man may have been right; nobody has yet been able to count them all.

Throughout the Thirties and Forties, the greatest scientists of the day tried and failed to figure out the magic number 137. The great Werner Heisenberg told his friends that the problems of quantum theory would disappear only when 137 was explained, and spent years trying to explain it; fortunately, the problems did go away despite his failure. One of Heisenberg’s friends, theorist wolfgang Pauli, wasted endless research time trying to multiply pi by other numbers to get 137; Edward Teller, now a prominent advocate of star wars, derived alpha from gravitation; and a dotty Japanese showed that the difference in the masses of the proton and delta particle is equal to alpha. All this shows is that there are many ways you can multiply and add a bunch of numbers to get 137. The closest any of these people got to the answer, perhaps, was when Pauli died — in hospital room 137.

The best explanation of the mystery ever given to Victor Weisskopf, another leading theorist from that time, was provided by Gershom Scholem, one of the most eminent scholars of Jewish mysticism. When Scholem met Weisskopf, he asked about the prominent unsolved problems in physics. Weisskopf said, “Well, there’s this number, 137….” And Scholem’s eyes lit up! He said, “Did you know that one hundred thirty-seven is the number associated with the Cabala?”

After physicists slam into a problem for a few decades, they tend to go into greener pastures. Alpha calculating has been out of fashion for a while. Physics is making progress without it. But it is comforting to know that if you’re at a party, and some know-it-all is talking about how great the progress of science is, you can always say, “That’s true, my man. But why is alpha equal to one hundred thirty-seven?”

Charles C. Mann

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