Weak Nuclear ForceWeak interaction - Wikipedia, the free encyclopedia It is responsible for the radioactive decay of subatomic particles and initiates the process known as hydrogen fusion in stars. Weak interactions affect all known fermions; that is, particles whose spin (a property of all particles) is a half-integer In the Standard Model of particle physics the weak interaction is theorized as being caused by the exchange (i.e., emission or absorption) of W and Z bosons; as such, it is considered to be a non-contact force. The best known effect of this emission is beta decay, a form of radioactivity. The Z and W bosons are much heavier than protons or neutrons and it is the heaviness that accounts for the very short range of the weak interaction The Fundamental Forces and Their OriginsSome CharacteristicsStrong—always attractive; binds quarks in hadrons (baryons, mesons); and the residual strong force binds protons and neutrons in nuclei—attractive at short ranges, powerfully repulsive at very short ranges; responsible for nuclear chemistry; mediated by gluons; strong force—is the only fundamental force that does not diminish with distance; no free quarks because energy to pull quarks apart creates new quarks Electromagnetic—attractive and repulsive; binds electrons in shells to nuclei; responsible for chemistry; mediated by photons; light; infinite range but charge canceling Weak—mediated by W and Z bosons; affects all fermions; very short range due to heaviness of W and Z particles, e.g. much heavier than neutrons; at 10−18 meters, the weak interaction has a strength of a similar magnitude to the electromagnetic force; but at distances of around 3×10−17 m the weak interaction is 10,000 times weaker than the electromagnetic Electroweak—the electromagnetic and weak; at very high energies, the universe has four massless gauge boson fields similar to the photon and a complex scalar Higgs field doublet. At low energies, gauge symmetry is spontaneously broken down to the U(1) symmetry of electromagnetism (one of the Higgs fields acquires a vacuum expectation value). This symmetry breaking would produce three massless bosons, but they become integrated by three photon-like fields (through the Higgs mechanism) giving them mass. These three fields become the W+, W− and Z bosons of the weak interaction, while the fourth gauge field which remains massless is the photon of electromagnetism Gravity—the weakest; always attractive; infinite range Holding the Universe TogetherStrong—nuclear chemistry Electromagnetic—light; universe opaque in radiation era; transparent in matter era; ‘normal’ chemistry Weak—creation of matter during ‘big bang’ Gravity—holds universe together since all matter has mass and is always attractive QuestionsWhy four fundamental forces? Perhaps because that is what it takes—at least one way—to make a complex universe such as ours, i.e. each force has a function noted above and they act together to produce this complex universe; this is of course only an outline that might apply to many other universes Why symmetry and symmetry breaking? Conditions of stability in balance with evolution of complexity Why is the Universe isotropic? Perhaps because the entire universe was in communication before inflation Why do particles have the same properties everywhere? Why is the speed of light constant? Same answer as above Why do all particles have the same speed of interaction? Do they? Perhaps because they were co-created Why is the speed of light fundamental? Probably because it is the universal speed of interaction; therefore interaction is self limiting to that speed; i.e. ‘c’ is not just a number that is tacked on to things Why is gravity only attractive? This of course implies a similar question about other forces, i.e. why they are signed as they are? Perhaps in creation from the Void all particles are equally signed. However, a stable universe requires long distance attraction. Gravity is that force that provides that. It may also therefore be that since gravitation dominates the universe as an attractive whole, gravitational charge (mass) is possessed universally i.e. all particles ‘feel’ gravity Why symmetry? A stable universe will possess symmetry. Why symmetry breaking? A perfectly symmetric universe will be ‘too perfect’; i.e. cannot come into existence at least temporally for temporality requires too much determinateness; if in existence it will remain there, frozen, atemporal TopicsHadron, Lepton, Boson, Fermion, Higgs |