Lesson Plan

Define a Grand Unified Theory (GUT) and explain why physicists pursue the unification of forces

Describe the electroweak theory and the prediction and confirmation of the W and Z bosons

Explain why the forces appear distinct at ordinary energies but unify at high energies, and why full unification is experimentally out of reach

Explain how Grand Unified Theories can be tested indirectly, using proton decay and the Super-Kamiokande experiment as the example

Explain the evolution of the four fundamental forces from the Big Bang onward through the cosmic epochs

23.3

"The search for a correct theory linking the forces, called the Grand Unified Theory (GUT), is explored in this section." "In the 1960s, the electroweak theory was developed by Steven Weinberg, Sheldon Glashow, and Abdus Salam. This theory proposed that the electromagnetic and weak nuclear forces are identical at sufficiently high energies." "Multiple current GUTs hypothesize that the stable proton should actually decay at a lifetime of 10³¹ years." "The recession of galaxies looks like the remnants of a gigantic explosion, the famous Big Bang. Extrapolating backward in time, the Big Bang would have occurred between 13 and 15 billion years ago, when all matter would have been at a single point." "As a result, modern cosmology suggests that all four forces would have existed as one force, a hypothetical superforce as suggested by the Theory of Everything."