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PCS 181 (133)
Lecture

# PCS 181 class 5.docx

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School
Ryerson University
Department
Physics
Course
PCS 181
Professor
Margaret Buckby
Semester
Winter

Description
PCS 181 PCS 181 Friday, January-25-13 Class 5 Future of a Closed or Oscillating Universe 1. The expansion phase = statements 1-5 2. At some unknown future time, re-contraction begins. The density of the universe increases. The number of black holes increases and they feast on everything within reach. 3. Black holes will meat and coalesce (merge) into one black hole = the universe = the new singularity = The Big Crunch How to Decide Among Those Futures  Is there sufficient matter to exert a strong gravitational force?  ≥ 5 protons per m^3 (meters cubed)of space  “calculations indicate that if there are ≥ 5 protons per m^3, the universe will collapse”  Gravity will dominate and re-contract the universe  Resulting in a closed or oscillating universe  < 5 protons per m^3  Gravitational attraction among all particles is insufficient to “close” the universe  Unopened universe that expands forever Density Measurement of Universe  The sum of all observed luminous matter  Research has concluded that there is not enough matter to re-collapse the universe (luminous matter)  This is flawed however, due to the fact that they only studied luminous matter  What about non-luminous matter:  Clouds of dark gas  Planets  Dead stars  Black holes  Neutrinos (small mass moving at the speed of light0  Dark matter (Vera Rubin proved its existence) Dark Matter  A galaxy rotation curve (that Rubin constructed) looked at different stars  Plots star distances vs their distance from the centre of the galaxy concluded that stars farther away from the centre are moving at similar speeds as those closer in Page 1 PCS 181  The explanation for this is that Dark Matter exerts an extra gravitational force Galaxy Rotation Curve Chart Rotation curve of a typical spiral galaxy: predicted (A) and observed (B) Dark Matter Cont.  Invisible mat
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