AST201H1 Chapter Notes - Chapter 22.1 - 22.3: Strong Interaction, Photon, Electroweak Interaction

• School: UTSG
• Department: Astronomy & Astrophysics
• Course: AST201H1
• Professor: Bryan Gaensler

Document Summary

22. 1 - 22. 3: the birth of the universe. Hubble"s discovery = all life began at one moment. See young galaxies that are in the process of forming --> gradual aging of universe. Cannot see back further in time to see when the universe began. Hot and dense collection of matter and radiation. Expansion and cooling of mixture of particles and photons. Cooling with time as it expands --> must have been hotter and denser in the past. Universe was so hot that photons could transform themselves into matter. Two photons collide with a total energy greater than twice the mass-energy of an election, they create two new particles --> negatively charged electron and positively charged twin (antielectron) When electron and antielectron meet --> destroy each other by transferring all their mass-energy back into photon energy. Early universe had photons, matter, antimatter all converting back and forth. Dominant force between particles in atoms and molecules.