PCS 181 Lecture Notes - Lecture 3: Vera Rubin, Cyclic Model, Neutrino

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PCS 181 CLASS 5
Future of an open or flat universe
Time after Big Bang
1. 1 x 1012 years
2. 1 x 1014 years
3. 1 x 1017 years
4. 1 x 1018 years
5. 1 x 1030 years
6. 1 x 10100 years
7. Far future
Situation
- Hydrogen and helium are depleted -> no
new stars can form (hydrogen and
helium clouds have been used up for
formation of stars so new stars can’t
born )
- Existing stars run out of fuel
- All stars will have experienced ~10
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)
- Hawking-> Black Holes decay (research
report)
- The big fizzle = an ever-expanding gas of
electrons, protons, neutrons, photons
Black hole a lot of matter in small volume space. Collapse of material into small volume space
Super massive black holes one in Milky Way. Millions of times a black hole
Einstein-Rosen (research topic)
Future of a closed or oscillating universe
1. The expansion phase = statements 1. Through 5. Above
2. At some unknown future time, re-contraction begins. The density of the universe
increases, the number of Black Holes increases. They feast on everything within reach.
3. Black holes will meet and coalesce (merge) into ONE Black Hole=the universe=the new
singularity = THE BIG CRUNCH
How to decide among these futures
- Is there sufficient matter to exert a strong gravitational force?
> 5 protons per m3 of space
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gravity will dominate and re-contract the universe
a closed or oscillating universe
< 5 protons per m3 of space
gravitational attraction among all particles is insufficient to “close” the
Universe
an open Universe that expands forever
Density measurement of universe
The sum of all observed, luminous matter-> NOT enough matter to re-collapse the Universe.
What about non-luminous matter?
Clouds of dark gas, planets, dead stars, Black Holes, neutrinos….DARK MATTER (Vera Rubin)
DARK MATTER
- A Galaxy Rotation Curve
- Plots star velocities vs. their distance from the center of the galaxy.
- Vera Rubin -> star velocities measured at the edge of a galaxy violates Newtonian and
Keplerian laws. E.g. speed of star a=speed of star b
- KEPLER AND Newton
- A galaxy’s rotation curve compares the disk stars’ velocities with their distances from
the galaxy’s center
- Invisible material called DARK MATTER permeates the galaxies
- It exerts 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 the DARK MATTER are unknown
- Could it be non-luminous normal matter?
- Normal matter is mostly hydrogen in space
- Unknown types of particles?
- Gravitational effects from galaxies in a parallel universe?
The universe is composed of 4% Baryonic matter = normal matter (protons, neutrons, etc.)
23% dark matter
73% dark energy (presently causing an acceleration of our universe = another mystery!)
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Document Summary

Time after big bang: 1 x 1012 years. All stars will have experienced ~10 disruptive encounters, flinging their planets into space. Evaporation of stars and collapse of galaxies into the central black holes. P+ -> e+ + v(a positron and neutrino) E+ + e- ->y (a photon= a burst of radiative: 1 x 10100 years energy, far future. Hawking-> black holes decay (research report) electrons, protons, neutrons, photons. Black hole a lot of matter in small volume space. The big fizzle = an ever-expanding gas of. Super massive black holes one in milky way. Future of a closed or oscillating universe: the expansion phase = statements 1. Above: at some unknown future time, re-contraction begins. The density of the universe increases, the number of black holes increases. They feast on everything within reach: black holes will meet and coalesce (merge) into one black hole=the universe=the new singularity = the big crunch. Gravity will dominate and re-contract the universe.

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