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Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
1
Big Bang, Black Holes, No Math
ASTR/PHYS 109
Dr. David TobackLectures 20
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
2
Was due Today – L20• Reading:
– (Unit 4)• Pre-Lecture Reading Questions:
– Unit 4 Revision (if Desired): Stage 1, due Wednesday
• End-of-Chapter Quizzes:– Chapter 13
• Papers:– Paper 2 Revision (if desired): Stage 2 due
Wednesday– Paper 3: Stage 1, due today
• Honors Papers:– (Stage 2)– Final paper due on the last day of class
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
3
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”
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
4
The History of the Universe
Universe expands as time passes
Un
ivers
e c
ools
dow
n a
s t
ime
passes
1 second
10 billion years
10 billion degrees
1 degree
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
5
Various TimesExplain 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
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
6
Where are we now in the history?
3 Minutes
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
7
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
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
8
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
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
9
Proton + Proton Deuterium + Electron + Neutrino
Forming Heavy Nuclei in the Early Universe
Proton
Proton
DeuteriumNuclear Reaction
Electron
Neutrino
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
10
Nuclei and Low Energy Photons
Deuterium
Low Energy Photon
At the 3 minute mark, low energy photons only
“bump” nuclei
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
11
Proton + Deuterium 3He + Photon
Can Now Build Heavier Nuclei
Deuterium
Proton
3He
Nuclear Reaction
Photon
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
12
3He + 3He 4He + 2 Protons
Creating Stable Helium
3He
3He
4He
Nuclear Reaction
Proton
Proton
Replenishes the hydrogen in the Universe
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
13
Why so few atoms Heavier than Helium?
Nuclear Physics
Can build up Hydrogen and Helium one at a time
So What? Since 5He and 5Li decay quickly they don’t have enough time to find another proton to become 6Li and be stable
Almost no elements heavier than helium are produced in the early Universe
Next possibility, 5He or 5Li, isn’t stable
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
14
The Helium Story• Able to predict the fraction of the atoms in the
Universe that are Helium– 75% of atomic mass in hydrogen – 25% of observed mass in helium
•Same as saying about 91% of the atoms are hydrogen
• Helium is the same in every direction because it was created everywhere – Entire Universe had the same temperature
everywhere– If it was created mostly in stellar cooking
we’d see it coming from the directions where there are more stars• I.e., the direction of galaxies•More on this in Chapter 16
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
15
Time marches on…
•Universe continues to expand and cool
•Number of protons goes up and number of neutrons goes down–Why? Neutrons can decay into protons
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
16
Neutron Proton + Electron + Neutrino
Neutron Decay
Neutron
ProtonDecay
Electron
Neutrino
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
17
The End of an Era
•For the next couple hundred thousand years things don’t change much
•Nuclear processes eventually stop making new heavy nuclei since the Universe gets so big
•But it’s still MUCH too hot for atoms to form
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
18
The beginning of a new Era
•From 200,000-700,000 years the universe expands and cools
•All the protons, neutrons and electron combine to form atoms–Translation: Universe cools until the photons in the universe can’t knock all the electrons out of the atoms any more
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
19
Atoms in a Lower Temperature Universe
Proton
Electron
HydrogenAtom
ElectroMagnetic Reaction
At these lower temperatures photons can’t easily break up
atoms
Photon
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
20
Where are we now in the history?
200,000-700,000 years
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
21
Some Time Passes
The Transition From a Hot Universe to a Cool Universe
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
22
The Universe at ~700,000 Years Old
•At a temperature of about 3000K, photons, on average, can’t knock apart atoms
•We can now have stable atoms and all the electrons become part of atoms
•The atoms are now free to form into stars and galaxies
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
23
Give this special time in history a name
Call this time “Recombination” Crappy
Word!Atoms are combining for the first time, not
recombining!
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
24
Atoms in the Universe
Early Universe A couple hundredThousand Years Later
These days
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
25
Before and After the Creation of Atoms
Lots of electrons and protons in the UniversePhotons scatter from
charged particles
Protons and electrons combine
to form atoms Universe becomes
transparent for photons
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
26
Transparent Universe
The Universe now LOOKS different!•The light (photons) have no free
electrons to interact with •Since all the electrons are in atoms,
because of Quantum Mechanics, they largely ignore the photons
•Photons just travel in a straight line Like traveling through glass
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
27
Atoms in the UniverseEarly UniversePhotons bust apart atoms
A couple hundredThousand Years Later
Photons can only excite atoms
These daysUniverse is transparent to photons
Hydrogen
High energy photon
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
28
A Cartoon…
Before Recombination: Photons interact with charged particles Scatter and change directions
+
++
+
+
+
++
After Recombination: Atoms ignore the photons Photons travel in straight lines forever
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Cosmic Background Radiation
•The photons we see in the cosmic background radiation are essentially the photons AFTER they interacted with their last charged particle
•Well… they’ve been traveling for awhile so they’ve changed a little 29
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
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Photons in the UniverseAfter recombination, photons can travel freely through spaceTheir wavelength is only stretched (red shifted) by cosmic expansionObserve most photons as as the cosmic background radiation! Also can observe photons emitted from Galaxies a billion years ago (just reaching us now) as being red-shifted
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
31
Looking Back at the Early Universe
The more distant the objects we observe, the further back into the past of the universe we are looking
Evolution of the UniverseTopic 2: After The First Three
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Big Bang, Black Holes, No Math
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The next few billion years
After less than ~0.5 billion years, the first stars form Stars produce heavy elements (“Stellar Cooking”)
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
33
A Neutral Universe• After the electrons and protons
combine to form atoms the Universe is almost completely neutral i.e., neutrally charged
• Why is this so important? All the particles in the Universe stop attracting each other due to their electric charge–Not completely true, just true
outside the atoms –Basically can ignore electric charge
from here on out
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
34
Some Time Passes
The Transition From a “Charged” Universe to a “Neutral” Universe
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Aside on Dark Matter• Dark matter is a BIG part of this story
because there is 5 times more mass in the Universe in dark matter than in atoms–Will come back to this in Chapter 15
• However, the story doesn’t change much with Dark Matter since we think it is just another neutral particle
35
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
36
A Gravity Dominated Universe
•The only thing left is gravity! •The gravitational attraction between massive things ONLY makes them move towards each other
•Any single atom would be most attracted to the closest place with lots of mass
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
37
Wait a Half Billion Years
•As the years go by, mass clumps together
•By a half a billion years after the bang, most of the mass is in one of a large number of “clumps”
•Billions of these clumps, each becomes a galaxy!
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
38
Fast Forward…
•Fast forward 13 billion years –Temperature of space is now ~3 degrees
–Cosmic Background Radiation•We get people…•More on Stellar and Galaxy
Formation next
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
39
Looking Forward
•Finished Unit 4–Evolution of the Universe
•Starting Unit 5–Big Objects and Black Holes
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
40
For Next Time – L20• Reading:
– Unit 5• Pre-Lecture Reading Questions:
– Unit 4 Revision (if Desired): Stage 1– Unit 5: Stage 1
• End-of-Chapter Quizzes:– Chapter 14 (if we finished Chapter 14, else just 13)
• Papers:– Paper 2 Revision (if desired): Stage 2 due
Wednesday– Paper 3: Stage 2 due Monday before class
• Honors Papers:– (Stage 2)– Final paper due on the last day of class
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Full set of Readings So Far•Required:–BBBHNM: Chaps. 1-15
•Recommended:–TFTM: Chaps. 1-5–BHOT: Chaps. 1-7, 8 (68-85), 9 and 11 (117-122)–SHU: Chaps. 1-3, 4(77-93), 5(95-114), 6, 7 (up-to-page 159) –TOE: Chaps. 1-3
41
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Clicker Question
Why can we only see so far back into space?
a)Because before recombination the light in the universe was scattering off most of the particles
b)Because there are too many things in the way which block our ability to see
43
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Clicker Question
Which of the following requires the highest energy photon?
a)Breaking apart a Protonb)Breaking apart a helium nuclei
c)Breaking an electron out of a hydrogen atom 44
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Clicker QuestionOrder the following in the order of highest
required energy to lowest required energy
A.Breaking apart a ProtonB.Breaking apart a helium nucleiC.Breaking an electron out of a hydrogen
atoma) A>B>Cb) A>C>Bc) B>A>Cd) B>C>Ae) C>A>Bf) C>B>A
45
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Clicker Question
What was the last thing a typical photon in the universe (part of the Cosmic Background Radiation) did before we detected it?
a)Broke apart a Protonb)Broke apart a helium nucleic)Broke the electron out of a
hydrogen atom 46
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Clicker Question
Why do the photons in the universe appear to be in thermal equilibrium?
a)Because they all have exactly the same energy
b)They are in thermal equilibriumc)The universe was in thermal
equilibrium, and the photons are just one of the particles in the Universe
47
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Clicker Question
Why is hydrogen the most abundant element in the universe?
a)It is the lightest elementb)Any heavy elements that might
have been present would have been broken apart by high energy photons in the early universe
c)Both of these contribute
48
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Clicker QuestionQ: Which of the following statements is
MOST correct?a)The photons in the cosmic background
radiation are there because the Universe has been expanding for ~13 billion years
b)The photons in the cosmic background radiation are there because the universe was in thermal equilibrium
c)The photons in the cosmic background radiation are there because photons can exist forever
49
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Papers
50
•Papers:–Paper 0 Revision: Still working on re-grades. Will post in eCampus by Wednesday
–Paper 1 Revision: Let us know if you were misgraded
–Paper 2: •Bad Rubric fixed (everyone given credit for low-quality calibration)
•Working on re-grades–Paper 2 Revision: Changed due date to Wednesday before class
–Paper 3: Text due Wed before class
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
51
Prep for Today (Is now due) – L19
• Reading:– BBBHNM 14
• Reading questions:– Chapter 14
• End-of-Chapter Quizzes:– Chapter 13
• Paper Stuff– Paper 2 Revision: Text was due
before class. Calibrations and Review due Monday
– Paper 3: Text was due before class. Calibrations and Review due Monday
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
52
For Next Time – L19• Reading:
– Unit 5• Pre-Lecture Reading Questions:
– Unit 4 Revision (if Desired): Stage 1 Due Monday before class
– Unit 5: Stage 1 due Monday before class• End-of-Chapter Quizzes:
– Chapter 14 (if we finished Chapter 14, else just 13)• Papers:
– Don’t forget that ALL papers must be submitted to turnitin.com
– Paper 2 Revision (if desired): Stage 2 due Monday before class
– Paper 3: Stage 2 due Wednesday before class• Honors Papers:
– Stage 1 Revision
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
53
Prep For Next Time – L21•Note: May change depending on how far we get in lecture•Reading:–BBBHNM: All reading through Chapter 16
•Pre-Lecture Reading Questions:–All reading questions through 16
•End-of-Chapter Quizzes:–If we finished Chapter 14 then end-of-chapter quiz 14 (else just through Chapter 13)
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Prep for Next Time – P19
54
• Reading– BBBHNM 15– Recommended:
• SHU: 4(87-93)• TOE: 3• BHOT: 8(76-85)
• Reading questions– Chapter 15
• End-of-Chapter Quizzes– If we finished Chapter 14 then end-of-chapter quiz
14 (else just 13) • Papers
– Paper 2 Revision: Text was due before class. Calibrations and Review due Monday
– Paper 3: Text was due before class. Calibrations and Review due Monday
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
55
Prep For Next Time – L9• Note: May change depending on how far we get in
lecture• Reading:
–BBBHNM: All reading through Chapter 17• Reading Questions:
–All reading questions through 17• eLearning Quizzes:
–If we finished Chapter 14 then end-of-chapter quiz 14 (else just through Chapter 13)
• Papers:–Paper 3 text due in CPR and turnitin.com on Wednesday–Paper 3 calibrations, reviews and self-assessment before next class–Paper 2 revision: Text due Monday before class (if desired)
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
Papers
56
•Papers:–Paper 0 Revision: Still working on re-grades. Will post in eCampus by Wednesday
–Paper 1 Revision: Let us know if you were misgraded
–Paper 2: •Bad Rubric fixed (everyone given credit for low-quality calibration)
•Working on re-grades–Paper 2 Revision: Changed due date to Wednesday before class
–Paper 3: Text due Wed before class
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
57
Part II
In class Quiz for Next Time: What is happening in each region? {
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
58
Why not much Heavier than Helium?
Nuclear Physics
Can build up Hydrogen and Helium one at a time
So What? Since 5He and 5Li decay quickly they don’t have enough time to find another proton to become 6Li and be stable
Almost no elements heavier than helium are produced
Next possibility, 5He or 5Li, isn’t stable
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
59
Aside on Helium
Why is Helium important to the story?
Explains two things:1. Why the atoms in the Universe
are mostly Hydrogen and Helium, and not much else
2. Why the Helium, like the photons is evenly distributed around the universe
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
60
The Reading So Far and For Unit 5
Reading for Unit 5:• BBBHNM: Chaps. 15-17• SHU: 4(87-93)• TOE: 3• BHOT: 8(76-85)Full reading so far for Unit 5:• BBBHNM: Chaps. 1-17• TFTM: Chaps. 1-5• BHOT: Chaps. 1-7, 8 (68-85), 9 and 11 (117-
122)• SHU: Chaps. 1-3, 4(77-93), 5(95-114), 6, 7 (up-
to-page 159) • TOE: Chaps. 1-3Lecture prep: Turn in on eLearning
Two questions from Chapter 15 you want to know the answer to
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
61
Some Time Passes
The Transition From a Hot Universe to a Cool Universe
Electrons
Protons
Photons
Photons
Atoms
Electrons
Protons
Photons
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
6262
Writing Assignments
1. Short Assignment 1•Want to revise again? Talk
to me. Still not getting it? Need to get you to the writing center!
2. Short Assignment 2 is posted•Due Today
eLearning:Unit 3 now due Need to be working on Unit 4
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
6363
Papers AFTER Paper 2
Two options1. Research Paper
• If you want to do the research paper option you must turn in Stage 0 at the end of class today. Must be approved
•Stage 1 due Thurs Nov 5th • Final paper due the last day of class,
Tuesday Dec 8th
2. Two short papers like the first one•One on Black Holes (due mid Nov)•One on Dark Matter (due last day of
class)
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
64
Before 700,000 years: Summary
Photons are incessantly scattered by free electrons; photons are in equilibrium
with matter
Radiation dominated era
Photons-electron soup have the
same temperature (energy)
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
65
After 700,000 Years: “Recombination”
Protons and electrons combine to form atoms
universe becomes transparent for photons
Transition to matter dominated era
Crappy Word!Atoms are
combining for the first time,
not recombining!
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
66
A cartoon of an atom and a photon
Mostly this is happening now since the photons are low energy
Evolution of the UniverseTopic 2: After The First Three
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Big Bang, Black Holes, No Math
67
The Cosmic Background Radiation
After recombination, photons can travel freely through space
Their wavelength is only stretched (red shifted) by cosmic expansion
This is what we can observe today as the cosmic background
radiation!
Evolution of the UniverseTopic 2: After The First Three
Minutes
Big Bang, Black Holes, No Math
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Wait a Billion YearsAfter less than ~ 1 billion years, the first stars form Produce Heavy Elements in Stellar Cooking
Formation of the first stars