Monday, December 12, 2005
PLEASE REMEMBER TO BRING YOUR ID TO THE FINAL!!!
What is the Big Bang?
 Explosion by which everything, previously bunched up, was
thrown outwards
 Beginning of the universe
What happened after it?
 Temperatures declined
 Universe expanded
Eras of the Universe
Plank Era
 Before the universe was 10-43 seconds old
 Intense radiation fills all of space, causing production of particles
and antiparticles, which then annihilate
 Not much of a clue of what’s happening!
…the universe is cooling down and expanding…
GUT Era
 Between 10-43 and 10-38 seconds
 Intense radiation fills all of space, causing production of particles
and antiparticles, which then annihilate
 So hot that the electromagnetic, weak, and strong forces are not
three separate forces; they all act as one, the GUT force
…the universe continues to cool and expand,
the strong force “freezes out” (separates) from the GUT force,
energy released may have caused rapidly expansion: “inflation”…
Electroweak Era
 Between 10-38 and 10-10 seconds
 The electromagnetic and weak forces remain merged into the
electroweak force
 Intense radiation fills all of space, causing production of particles
and antiparticles, which then annihilate
 Before the end of this era, Big Band theory has no support from
direct experimental evidence
… the universe cools and expands,
the electromagnetic and weak forces separate…
Particle Era
 Between 10-10 and 10-3 seconds
 Intense radiation fills all of space, causing production of particles
and antiparticles (like protons and antiprotons), which then
annihilate
 Photons turned into quarks
 Quarks combined to form protons and neutrons
 More matter than antimatter at the end of this era
… the universe cools and expands,
spontaneous particle antiparticle pair production ceases…
Era of Nucleosynthesis
 Between 10-3 seconds and 3 minutes
 Protons and neutrons fuse together and then, due to high
temperatures, break apart
… the universe cools and expands,
spontaneous fusion stops,
matter in universe is 75% H nuclei, 25% He nuclei…
Era of Nuclei
 Between 3 minutes and 380,000 years
 Photons “bounce” between close-packed electrons
 Photons ionize any atoms, so nuclei typically have no electron
cloud
… the universe cools and expands,
nuclei capture electrons,
photons are able to travel out across the universe,
enter the era of atoms, then the era of galaxies
Material after Exam 3
Chapter 13-18
For the final, focus on large important topics, rather than small details
What is a neutron star? pulsar? (be able to draw picture)
What is a black hole? Where can you find black holes? Evidence for
existence? Effect on surrounding environment (ex. AGN)
What are the components of different types of galaxies? What do
different types of galaxies look like? (be able to draw picture)
How do we think galaxies form? Evidence?
How does the star-gas-star cycle work?
How can we measure distances to different objects?
What evidence is there for dark matter? What could dark matter be?
What are the 3 possible fates of the universe? Which do we think will
happen, and why?
What is the Big Bang? Why do we think the universe started with a big
bang?
Sample Multiple Choice Questions (material since exam 3)
1. A
2. B
3. B
4. D
5. D
6. B
7. A
8. A
9. A
10. C
11. A
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
C
D
D
C
C
C
A
A
A
A
B
C
B
C