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PCS 181 Lecture : Lecture 3

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copperbee918
30 Jan 2012
School
Ryerson University
Department
Physics
Course
PCS 181
Professor
Margaret Buckby

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Document Summary

Open universe: density of matter is low > gravity is weak > universe expands forever. Closed universe: density of matter is high > gravity will halt the expansion > universe will re-contract. If this happens repeatedly, we will have an oscillating universe. Flat universe: universe contains the so-called critical density of matter > galaxies barely manage to avoid re-collapse. Hydrogen and helium are depleted > no new stars can form. 1 x 1014 years existing stars run out of fuel. 1 x 1017 years all stars will have experienced ~100 disruptive encounters, flinging their planets into space. Evaporation of stars and collapse of galaxies into the central black holes. Protons decay (???) p+ > e+ + v (a positron and neutrino) e+ + e- > y (a photon = a burst of radiative energy) The big fizzle = an ever-expanding gas of electrons, protons, neutrons, photons.

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Physics: Principles with Applications
7th Edition, 2013
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ISBN: 9780321625922

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