PCS 181 Lecture Notes - Galaxy Rotation Curve, Vera Rubin, Cyclic Model

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Published on 13 Apr 2013
School
Ryerson University
Department
Physics
Course
PCS 181
Page:
of 3
PCS 181
Page 1
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
PCS 181
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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 material called dark matter permeates the galaxies
It exists as a gravitational influence on the stars causing them to deviate from Newton’s and
Kepler’s Laws
Dark matter also affects members of a group of galaxies
The Nature and Composition of Dark Matter is Unknown
Could it be non-luminous normal matter?
Not possible because dominant element (hydrogen) gives a signal even when not lit up
Unknown types of particles give off no electromagnetic symbols
Gravitational effects from galaxies in a parallel universe
The Universe is Comprised of
4% Baryonic matter = normal matter (protons, neutrons, etc.0
23% Dark Matter
73% Dark Energy (presently causing an acceleration of our universe = another mystery)
Dark Energy
Totally empty space, the vacuum, contains energy
This energy is variously called dark energy quintessence the vacuum energy, the cosmological
constant
Dark energy drives the recently observed acceleration of the universe
Dark energy ≠ dark matter
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Dark matter is associated with the acceleration of the universe
Inflationary Cosmology = Inflation
Pans of virtual particles “pop” into existence from the vacuum and quickly annihilate each other
Virtual particles are permitted to exist by the laws of Quantum Mechanics
Quantum Mechanics
Proven to exist by the Casimir experiment
Inflation pre big bang there was an infinite energy field
Our whole universe simply “popped” into existence of this energy spontaneously converted into
matter
E = mc^2 -> m = E/C^2
Our brand new, still small universe has achieved thermal equilibrium
Next, a fraction of a second after achieving the big bang the universe expanded dramatically by
a factor of 10^30
This explains the universal CMB = 2.728K 3K in all directions of space

Document Summary

Future of a closed or oscillating universe: the expansion phase = statements 1-5, at some unknown future time, re-contraction begins. The number of black holes increases and they feast on everything within reach: black holes will meat and coalesce (merge) into one black hole. 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. Gravitational attraction among all particles is insufficient to close the 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. Neutrinos (small mass moving at the speed of light0. Dark matter (vera rubin proved its existence) A galaxy rotation curve (that rubin constructed) looked at different stars.