At that distance, the strengths of the electromagnetic and weak nuclear forces are the same. Thus, the energy scale on the horizontal axis of Figure 23.20 also corresponds to shorter and shorter distances (going from left to right), with 100 GeV corresponding to approximately 10 −18 m, for example. This diagram is similar to the diagrams in Figure 23.6 and Figure 23.5 for the electromagnetic and strong nuclear forces.Īs discussed earlier, the short ranges and large masses of the weak carrier bosons require correspondingly high energies to create them. But experiments show that at extremely short distances and at extremely high energies, the strengths of the forces begin to become more similar, as seen in Figure 23.20.įigure 23.19 The exchange of a virtual Z 0 Z 0 particle (boson) carries the weak nuclear force between an electron and a neutrino in this Feynman diagram. For example, they are carried by different particles and have greatly different strengths. How can forces be unified? They are definitely distinct under most circumstances. In 1983, these carrier particles were observed at CERN with the predicted characteristics, including masses having those predicted values as given in Figure 23.17. Not only were three particles predicted, but the mass of each W + W + and W − W − boson was predicted to be 81 GeV/ c 2, and that of the Z 0 Z 0 boson was predicted to be 90 GeV/ c 2. One of the main consequences of the electroweak theory was the prediction of three short-range carrier particles, now known as the W +, W +, W −, W − ,Īnd Z 0 Z 0 bosons. At lower energies, like those in our present-day universe, the two forces remain united but manifest themselves in different ways. This theory proposed that the electromagnetic and weak nuclear forces are identical at sufficiently high energies. In the 1960s, the electroweak theory was developed by Steven Weinberg, Sheldon Glashow, and Abdus Salam.

The search for a correct theory linking the forces, called the Grand Unified Theory (GUT), is explored in this section. With these considerations in mind, it is natural to suggest that a theory may be constructed in which the strong nuclear, weak nuclear, and electromagnetic forces are all unified. As shown in Figure 23.19, carrier particles transmit three of the four fundamental forces in very similar ways. More recently, the weak nuclear force was united with the electromagnetic force.

In the nineteenth century, the distinct electric and magnetic forces were shown to be intimately connected and are now collectively called the electromagnetic force.

Present quests to show that the four basic forces are different manifestations of a single unified force that follow a long tradition.

Fundamental forces unification