670 likes | 1.47k Views
The Four Fundamental Forces. Standards. Know that there are four fundamental forces in nature: gravitation, electromagnetism, weak nuclear force and strong nuclear force. 4 Fundamental Forces.
E N D
Standards • Know that there are four fundamental forces in nature: gravitation, electromagnetism, weak nuclear force and strong nuclear force
4 Fundamental Forces • There are 4 fundamental forces within all atoms, which dictate interactions between individual particles, and the large-scale behavior of all matter in the universe. • They are: • Gravitational force • Electromagnetic force • Strong nuclear force • Weak nuclear force
Gravitational Force • Force of attraction between each and every particle in the universe. • Always attractive: pulls matter together. • Weakest of the forces. • Very long ranged (furthest reach of all the forces, therefore of great importance in cosmology.
Gravitational Force • Even though it’s weak, it always wins over cosmological distances. • It is the most important force for understanding the large scale structure and evolution of the Universe.
Electromagnetic Force • Determines how electrically charged particles interact with each other and with magnetic fields. • Can be attractive or repulsive. • Long-ranged, but weaker than the strong force. • Holds electrons in their orbital shells around the nucleus of an atom
Weak Nuclear Force • a.k.a., weak interaction • Very powerful • Very short-ranged: acts on scale of atomic nuclei
Weak Nuclear Force • Causes radioactive decay in the form of beta decay • Beta decay – a neutron spontaneously breaks up into a proton, an electron, and an antineutrino • Responsible for synthesizing different chemical elements in stars and in supernova explosions
Strong Nuclear Force • a.k.a. strong interaction • Strongest of the forces • Very short-ranged • Is attractive • Keeps protons and neutrons bound together in the nuclei of atoms (prevents protons from flying apart because of the repulsion between their like-charges)
Strong Nuclear Force • Because it binds nuclear particles so tightly together, huge amounts of energy are released when nuclei are fused together (fusion) or broken apart (fission). • It is the underlying source of the vast quantities of energy that are generated by the nuclear reactions that power the stars.
Unification of the Forces • At the temperatures and energies in the universe today, the four forces are distinct from each other. • Theoretical physicists think this was not always so.
Unification of the Forces • In the very early universe, when temperatures were much higher, the weak, electromagnetic and strong forces were unified into a single force. • Theories that would unify these 3 forces are called Grand Unified Theories, or GUTs
Unification of the Forces • Superunified theories, or the Theory of Everything (TOE) unifies all 4 forces. • It is thought that all 4 forces were unified during the first instants of the BigBang.
Unification of the Forces • Combining these forces is one of the biggest problems in physics today. • It will take a unified theory to be able to understand what happened at the instant of the Big Bang, and for a fraction of a second after. • Unification is also needed to understand what happens in the bottom of black holes, at the singularity.