What Are Weak Forces?

Newton, Faraday and Einstein each believed that there must be some sort of unity in the forces of nature. Faraday, having unified electricity and magnetism, conducted experiments to try to find a connection between these forces and gravity. From 1922 until his death in 1955, Einstein was trying mathematically to unify gravity with electromagnetism. In the event, the force that was eventually unified with electromagnetism is one that was unknown to Newton and Faraday, and perhaps not considered very important by Einstein. This is the so-called weak force. In previous chapters I have ignored the weak force, but now I must explain what it is.

In 1896 (a few months after the discovery of X-rays) Henri Becquerel in Paris discovered the radioactivity of uranium. Studied further by Marie and Pierre Curie, the nature of radioactivity was finally elucidated by Rutherford and Soddy in Montreal during the early 1900s.

In radioactivity, an atomic nucleus emits “rays”, unpredictably but with a definite probability per unit time, often changing into a different nucleus in the process. By a historical accident, three totally different processes are lumped under the heading “radioactivity”. One is the emission of alpha-particles, the nuclei of helium atoms, each made up of two protons and two neutrons. This happens as a result of the strong, nuclear forces. The only reason that it happens slowly (slowly compared to the time for an alpha particle to traverse the nucleus) is that the alpha particle's wave function has only a very small “tail” outside the nucleus.