The first intimations that β decay is but one manifestation of so — Weak interaction

"s were among the most paradoxical members of the zoo of elementary particles that were discovered after the war. Produced during radioactive decay, they supposedly had neither charge nor mass and they traveled, consequently, at the speed of light. Their only interaction with the world (besides gravity) was by something called the "weak" force, which causes some kinds of radioactive decay. It was so weak that, according to calculations, a typical neutrino could pass through a million miles of water unhindered—stars and planets were transparent to them."

"The weak force... least fits into our typical picture of what a force should do. ...the categories of attractive and repulsive do not really fit the weak force ... because it has the ability to change particles from one type to another. ...The weak force can change one into another provided they are in the same generation. The electron can be changed into an electron and vice versa, but the electron cannot be turned into the ..."

"In his theory of beta reactivity Fermi introduced a new type of interactions among elementary particles, which today we call "weak interactions". Many new manifestations of weak interactions, which could be interpreted using Fermis 1933 theory, were found in the following decades. The study of weak interactions has led to surprising discoveries, among which the violation of specular symmetry (known as parity symmetry or P symmetry), and the violation of time reversal symmetry (T symmetry) and of the symmetry between matter and antimatter (CP symmetry)."

"The... weak force... couples to both s and s, and is very short-ranged due to the large rest mass of the messenger quanta involved. Its effective strength is usually many orders of magnitude weaker than electromagnetism, and its action can cause particles to change identity, as when a neutron decays. Unlike the electromagnetic and strong forces, the weak force violates parity conservation."

"[T]he work of a number of theoretical physicists in the 1960s culminated in the electroweak theory that is designed to unify electromagnetism and the weak force... This theory is sometimes called the GWS Theory, from... Sheldon Glashow, Steven Weinberg and Abdus Salam... The main feature of the theory is that at extremely high temperatures the electromagnetic and weak forces are two components of a single force, the electroweak force. The symmetry between the two forces would only be apparent at temperatures of trillions of degrees... in the Big Bang. At lower temperatures... electromagnetism remains a long range force, but the weak force takes on the characteristics of... a very weak force that acts over extremely short distances. ...But the theory is dependent on the existence of the Higgs particle..."

"The weak force does not seem to hold anything together, only to break it apart. ...we do not observe s of the weak force. ...So the weak force seems a force apart... Interwoven with the surprising story of the weak force has been the story of s, arguably the most intriguing of the fundamental particles. ...the neutrinos provide a unique and valuable mirror on the weak force. ...In the 1920s, and for a while disputed the energy spectrum of electrons emitted in β decay. ...Chadwick demonstrated... that the spectrum was continuous, i.e. the electron could take on a whole range of energies. ...contrary to the single line expected from energy conservation if only... the electron and the nucleus, were involved... Neils Bohr advocated abandoning energy conservation... but in 1930 Wolfgang Pauli daringly proposed an unseen... neutrino... Paulis intuition... inspired Enrico Fermi in his tentative theory of β decay... to become the basis for ideas of a universal weak force."