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Lecture 17

Astronomy 1011A/B Lecture 17: astronomy chapter 17

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Astronomy 1011A/B

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Chapter 17 Eras (I) The universe has gone through several major eras over its history. These eras are: The Planck Era the time before second when we require a theory of everything to describe what happened. As yet, we lack such a theory. The GUT Era At the start of this era, gravity became distinct from the other forces so that there were two forces: gravity and the GUT force (a combination of the electromagnetic, the weak, and the strong forces). The era ended when the strong force froze out of GUT force, leaving three forces operating (gravity, strong, and the electroweak force). When this happened, the energy released may have driven inflation, causing the universe to go from the size of an atom to the size of the solar system in second. The Electroweak Era This era was dominated by three forces: the strong, the electroweak, and gravity. At the end of this era, all four forces became distinct and have remained so for the rest of the history of the universe. The Particle Era This era started with the separation of the electromagnetic and the weak forces and ended when the universe became cool enough that particle production ceased. At the end of the particle era, all of the quarks in the universe combined into protons and neutrons. Eras (II) The Era of NucleosynthesisDuring this era, the temperature of the univer
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