big bang, black holes, no math[宇宙大爆炸，黑洞，没有数学](69).ppt

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Big Bang, Black Holes, No MathASTR/PHYS 109Dr. David TobackLectures 20
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Was due Today – L20
Reading:
Unit 5
Pre-Lecture Reading Questions:
Unit 4 Revision: Stage 1
Unit 5: Stage 1
End-of-Chapter Quizzes:
Chapter 13
Papers:
Paper 2 Revision (if desired): Stage 2
Paper 3: Stage 2 due Wednesday
Honors Papers:
Stage 1 Revisions
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A Big Bang Occurs… Then What?
Universe goes through a phase of being hot and small with lots of high energy particles in thermal equilibrium
Then the Universe gets bigger and cooler
As it gets bigger, it “evolves”
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The History of the Universe
Universe expands as time passes
Universe cools down as time passes
1 second
10 billion years
10 billion degrees
1 degree
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Various Times
Explain what happens during each of a number of different periods in time
The VERY early universe
The first three Minutes
The next 300,000 years
The next billion years
~13 billion years later (now)
The ultimate fate of the universe?
The first four will take a couple of lectures
} Chap 14
} Chaps 15-17
} Unit 6
} Chap 13
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Where are we now in the history?
3 Minutes
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After the First Three Minutes
At about the 3 minute mark the temperature of the Universe is about 1 billion degrees
Electrons and positrons have mostly annihilated each other
No particles energetic enough to produce new ones
~1 electron for every proton
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What else?
The temperature drops so that the photons, on average, can’t even break up deuterium
Easier to start building up the heavier nuclei
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Proton + Proton
 Deuterium + Electron + Neutrino
Forming Heavy Nuclei in the Early Universe
Proton
Proton
Deuterium
Nuclear Reaction
Electron
Neutrino
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Nuclei and Low Energy Photons
Deuterium
Low Energy Photon
At the 3 minute mark, low energy photons only “bump” nuclei