ASTR 1020 Chapter 22: Eras and Evidence of the Big Bang Theory

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University of Colorado - Boulder
Astrophysical & Planetary Sciences
ASTR 1020
Webster Cash

The Birth of the Universe The Big Bang Theory - Everything began as a hot and dense collection of matter and radiation - It was so hot that photons could transform themselves into matter and vice versa. 𝐾 = 𝐾𝐾 . There were reactions that created and annihilated particles - The universe cools as it expands - There are 4 forces: - Gravity - Electromagnetic Force - depends on electrical charge of particle rather than mass. Responsible for all chemical and biological reactions. - The Strong Force - operates on extremely short distances. Binds protons and neutrons in atomic nuclei. - The Weak Force - operates on extremely short distances. Plays role in nuclear reactions like fusion and fission. Only force besides gravity that affects weakly interacting particles like neutrinos. - In early universe, the forces were not as distinct as they are today. They merge. Ex: Electroweak force, electroweak + strong force = the GUT force, or possibly all the forces could’ve combined into one “super force” - - Eras of the early universe - The Planck Era - Times before the universe was 10 −43 second old - Substantial energy fluctuations - We don’t have a theory to describe conditions in this era. - The GUT Era - Merger of strong, weak, and electromagnetic force at temps above10 K. 29 - Ended when GUT split into strong and electroweak forces when universe was 10 −38second old. - Inflation, a sudden and dramatic expansion of universe, happened - The Electroweak Era - Three forces now: gravity, strong, electroweak 15 - Temp dropped to 10 K, electromagnetic and weak forces separated - We have experimental data concerning the conditions in the universe at the end of this era, not from any time before it. - The Particle Era - The time between the end of the electroweak era and the moment when spontaneous particle production ceased. - Photons turned into particles that we no longer find in the universe today, like quarks. - Ended when the universe reached 1 millisecond and temp was at 10 K, it 12 wasn’t hot enough to produce protons and antiprotons spontaneously. Protons must have slightly outnumbered antiprotons at the end of this era. - The Era of Nucleosynthesis - Protons and neutrons left over began fusing into heavier nuclei, but gamma rays blasted them apart as fast as they formed.
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