ASTR-1010 Lecture Notes - Lecture 9: Electroweak Interaction, Grand Unified Theory, Positron
6 Oct 2016
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Document Summary
Universe has been expanding for 14 billion years: matter collected into galaxies, stars formed in those galaxies, producing heavy elements, 4. 6 billion years ago, the earth formed in the milky way. Before that time, light could not pass freely through the universe, so there is no possibility of seeing light from earlier times. Scientific models tell us what conditions were like in the early universe: universe is cooling and become less dense as it expands, so it must have been hotter and denser in the past. The universe was so hot during the first few seconds that photons could transform themselves into matter and vice versa. However, at the high temperatures that prevailed in the early universe, the four forces were not as distinct as they are today. Electroweak force: electromagnetic and weak forces merge together under conditions of very high temperatures.
