Short answers, pulled from the story.
The weak interaction is the only fundamental force capable of changing the very identity of a particle, transforming a down quark into an up quark and turning a neutron into a proton in the process. This unique ability to alter flavor lies at the heart of radioactive decay and the fusion that powers stars. The force operates over a distance smaller than the diameter of a proton.
Enrico Fermi proposed the first mathematical description of the weak interaction in 1933. His theory suggested that beta decay resulted from a four-fermion interaction that acted as a contact force with no range. This model laid the groundwork for future physicists to explore the deeper structure of the weak force.
Chien Shiung Wu and her collaborators confirmed that the weak interaction violates parity in 1957. This discovery demonstrated that the weak force acts only on left-handed particles and right-handed antiparticles. Chen-Ning Yang and Tsung-Dao Lee earned the 1957 Nobel Prize in Physics for their hypothesis that the weak interaction might violate this law.
The existence of the W and Z bosons was not directly confirmed until 1983. Experiments at the Super Proton Synchrotron at CERN finally detected these massive particles. The W bosons have a mass of approximately 90 GeV/c2, which explains the short range of the weak force.
The weak interaction is essential for the fusion of hydrogen into helium in a star by converting a proton into a neutron that can fuse with another proton to form deuterium. This process is the first step in the chain of nuclear reactions that power stars and create heavier elements. Without the weak force, stars would burn out quickly and the universe would remain a cold, dark expanse of hydrogen.
James Cronin and Val Fitch provided clear evidence in kaon decays that charge-parity symmetry could be broken in 1964. They won the 1980 Nobel Prize in Physics for this discovery. The weak interaction is the only force that breaks this symmetry, creating a subtle imbalance that allowed matter to dominate over antimatter in the early universe.