Big Bang, Black
Holes, No Math
ASTR/PHYS 109
Dr. David Toback
Lecture 21 & 22
Big Bang, Black
Holes, No Math
Big Objects and Black Holes
Topic 1: Galaxies
1
Was due Today – L22
• Reading:
– (Unit 5)
• Pre-Lecture Reading Questions:
– Unit 4 Revision (if Desired), Stage 2: Due before class
today
– Unit 5, Stage 2: Due before class today
• End-of-Chapter Quizzes:
– Chapter 14
• Papers:
– Paper 2 Revision (if desired), Stage 2: due before Class
today
– Paper 3, Stage 2: due before class today
• Honors Papers:
– Stages 1 & 2 must be approved explicitly
– Final paper due on the last day of class
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Topic 1: Galaxies
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Quick Review: Various Times
Walking through what happens during
each of a number of different
periods in time
– The VERY early universe
}
Chap 13
– The first three Minutes
– The next 300,000 years
}
Chap 14
– The next billion years
– ~13 billion years later (now) } Chaps 15-17
– The ultimate fate
} Unit 6
of the universe?
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Unit 5 Overview
• It turns out that the way Galaxies and
Stars form have similarities… start
there
• The way stars die depends on the star
itself… sometimes they die to form a
Black Hole
• Black Holes are some of the weirdest
things in the Universe…
– In many ways the formation of Black
Holes is like the Big Bang in Reverse
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Unit 5: Big Objects and Black Holes
1. Galaxies
2. Star Birth and
Death
• Black Hole
Formation
3. Properties of Black
Holes
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Today
5
Galaxy Formation: Overview
• Big picture: What Galaxies
“look like”
• A gravity dominated
Universe allows galaxies to
form
• When do galaxies form?
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What do galaxies look like?
All have common properties
1. Stars (produce the light
we see)
2. Gas (atoms not in stars)
3. Dark Matter (most of
the mass)
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Visualizing a Galaxy
• The light comes from the stars
• Most of the mass is Dark Matter
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In some ways, Dark
Matter surrounds
the stars in a
galaxy like the
water in a fishbowl
surrounds a fish in
the middle of the
bowl.
Not exactly the
same… denser in the
middle because of
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the pull of gravity 8
Topic 1: Galaxies
Two example “Types” of Galaxies
Spiral Galaxy: like the
Milky Way
Elliptical Galaxy:
• One giant bulge,
stars are like bees
buzzing around the
center, biggest
galaxies are
ellipticals
• Bulge in the middle
• Disk on the sides
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Topic 1: Galaxies
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From the Early Universe to Galaxies
• After about ~3 minutes
things are cool enough for
nuclei to form
• After ~300,000 years things
are cool enough for electrons
and nuclei combine to form
atoms
• Let’s move to a half a billion
years
after
the
bang
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Topic 1: Galaxies
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Where are we now in the history?
Half a billion years after the bang
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A Gravity Dominated Universe
• The gravitational attraction
between massive things ONLY
makes them move towards each
other through space
• Dark Matter and atoms are
neutral and massive
• Both are most attracted to the
closest place with lots of mass
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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”
• Huge numbers of these clumps,
each helps form galaxies!
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Topic 1: Galaxies
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Galaxy Creation Over Time
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Galaxy Formation Analogy:
People Jumping on a Trampoline
If two people touch, then will stick together
If they fall they create a big dent in the
trampoline (like a dent in space-time)
Once you get that first dent on the
trampoline everyone starts falling into it
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More Analogies
1. Water being poured into a
bowl and flowing to the
bottom
2. Water swirling in a bowl
3. Water in a bathtub with the
drain open (and ignoring what
happens to the water that
goes
down
the
drain)
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Water Flowing
• Think about water moving
towards a drain in the bathtub
– All falls in quickly  can get
bubbling at the drain
– Falls in slowly  Get swirling
• Different types of galaxies can
form
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Stars in Galaxies
• Atoms fall towards the center of the galaxy
or orbit around it
• Stars form where there are lots of atoms
• Once the atoms form stars there is a large
amount of distance between stars
– About 4 light years between us and our
nearest neighbor star
– A good exception is binary stars where two
stars formed together
• Stars can orbit around the center of the
galaxy
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Slow Atoms Outside the Galaxy
Where does the disk of
the Milky Way come
from?
Lots of atoms moving
around, far outside the
center of the galaxy
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Spinning into Shape
• Gravity attracts mass to the
densest place
–Center of the Galaxy
• As the mass is pulled in, it
starts moving slightly around
the center
• Why does this happen?
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Analogy: Ice Skater
Matter far away
• You’ve seen on
Pull
the
Matter
in
from the center
TV

Spins
faster
Spins slowly
• Try this at
home in a chair
that rotates
• Get yourself
spinning with
your arms and
legs stretched
out, then pull
them in
Can also think about
water falling into a
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drain
Topic 1: Galaxies
For those of you who have taken PHYS 218,
this is Conservation of Angular Momentum
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Dark Matter Vs. Atoms
• Dark Matter and Atoms behave
differently in galaxies
• When atoms get near each
other they can bump into each
other like people moving in a
movie theater
• Dark Matter is more like two
ships passing in the night
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Why is there a disk on the outside?
•
•
•
•
•
•
Focus on the atoms in the outer part of the galaxy… Not very dense
out there, so stars don’t form quickly
As atoms fall toward the center they are like the water from the
outer part of a sink
– They start bumping into other atoms, change the direction they are
moving
Once enough atoms are going in different directions a swirl CAN start;
atoms moving WITH the swirl can keep moving nicely and can go orbit
like a planet around the sun
– Like in a sink, an effective swirl can continue
– Atoms that try to go into other directions bang into the swirl and
lose energy (fall in, or go off into space)
Eventually, most of the atoms have either fallen in or become part of
the swirl
Eventually, the cloud gets drawn in close enough that the atoms get
close enough that they form stars
– Stars just stay in the disk orbit
Call this the disk
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Topic 1: Galaxies
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Visualize the process
Start right after things start to
contract…
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Topic 1: Galaxies
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Time progresses
As the galaxy contracts, things
can start moving very quickly
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More time Passes
Things start to “flatten out”
Said differently, the flay part can continue, but the
non-flat-part bets bumped out of orbit
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More time…
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Even more time…
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Even more time..
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Stable Galaxies
The stuff in this
stable state forms
Stars: Call this a
Galaxy
– Can give us disklike rotating
galaxies
– Can also form
other types like
elliptical galaxies
– Galaxies often
collide and get
even more
complicated
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Fun video
• Move from the simple view of a
galaxy forming to a more
complete computer model from
NASA
• How a disk galaxies gets
created
https://www.youtube.com/watch?&v=_Ssc1GsqHds
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Another fun video
Andromeda tied to
the rocks
Simulation of a future collision
between Andromeda and the
Milky Way, where the two
would create a combined galaxy
http://people.physics.tamu.edu/toback/109/Video/andromeda.avi
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Move from what galaxies
look like and how they
form to WHEN galaxies
form in the history of
the Universe
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When?
• Oldest observed galaxies appear about
500 million years after the bang
• Do we understand why this is? Use
computer simulations to see when, after
the Big Bang, galaxies form
• It turns out that if the Universe had
exactly the same temperature
everywhere it would take more than a
hundred billion years to get even one
galaxy
• What????
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Reason things might clump earlier?
• Clearly galaxies DID form before
that, so SOMETHING must have
caused them to start earlier
• Example of possible answer: If the
temperature weren’t perfectly
uniform then we could get clumping
earlier
• Go back to our trampoline analogy
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Kids on a Trampoline
The galaxies form shortly after we get
that first big dent in space time
• If we start with all the kids equally
spaced, then it will take longer to get
that first collision
• If two of the kids happen to start
slightly nearer each other, then those
two are more likely to get a collision
sooner and create the first dent sooner
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Topic 1: Galaxies
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Quantum Mechanics
• It turns out that when the Universe
is really small, the effects of
Quantum Mechanics can have a big
effect on the smoothness of the
Universe
• Can cause small variations in the
temperature at different places in
space
– Scientists gave this a cool name:
Quantum Big
fluctuations
Objects and Black Holes
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Topic 1: Galaxies
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So What?
• Different Temperature  Variation
in the amount of matter in
different places
• A region with slightly more matter
is more likely to be the place where
matter clumps
• Thus, Quantum Fluctuations in the
Early Universe could cause Galaxy
formation Big
toObjects
occur
earlier in time
and Black Holes
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Topic 1: Galaxies
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How would we look for this?
• How do we look at the
temperature in the Universe?
• Study the Cosmic Background
Radiation temperature
distribution
• Any variations in different
directions?
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Look for Variation in the Cosmic Background
Radiation
Look at the full
Temperature Map
(i.e, different colors correspond to
sky in a single map
different temperatures)
Stretch out a
Incredibly Uniform,
sphere onto a flat but are there small
page
variations?
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Exactly the same everywhere?
• Subtract off the same amount
everywhere
• What are we left with?
The overall temperature is
2.728 degrees Kelvin
The variation is very small
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DT = 3.353 mK
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Topic 1: Galaxies
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Hotter and Colder?
Colder here?
Hotter here?
DT = 3.353 mK
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What if we’re moving?
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Better Explanation
Doppler effect of
Moving away from this direction
our speed relative
to the rest frame
of the photon
background
Earth is going
around the sun at
~30 km/sec and
the solar system
is moving around
the Milky Way at
Moving toward this direction
~250 km/sec
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The Cosmic Background Radiation
Subtract
off all the
known
effects and
look for
“Variations”
Lots of
small
fluctuations
(Spots)
Everywhere
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Combining Quantum Mechanics and
General Relativity predict where the
galaxies form AND how long it takes
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Topic 1: Galaxies
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For Next Time – L21
• Reading:
– (Unit 5)
• Pre-Lecture Reading Questions:
– Unit 4 Revision (if Desired), Stage 2: Due before class
Wednesday
– Unit 5, Stage 2: Due before class Wednesday
• End-of-Chapter Quizzes:
– Chapter 15 (if we finished Chapter 15, else just 14)
• Papers:
– Paper 2 Revision (if desired), Stage 2: due before Class
Wednesday
– Paper 3, Stage 2: due before class Wednesday
• Honors Paper:
– Stages 1 & 2 must be approved explicitly
– Final paper due on the last day of class
Big Bang, Black
Holes, No Math
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Topic 1: Galaxies
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Full set of Readings So Far
•Required:
–BBBHNM: Chaps. 1-16
•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
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Holes, No Math
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Clicker Question
Order the following in the order of highest
required energy to lowest required energy
A. Breaking apart a Proton
B. Breaking apart a helium nuclei
C. Breaking an electron out of a hydrogen atom
a) A>B>C
b) B>A>C
c) B>C>A
d) C>A>B
e) C>B>A
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Clicker Question
How far back in time can we “see” (clear line of
sight from light) when we look into space?
a) To ~0.5 billion years after the bang (time
of creation of the first stars)
b) To ~250,000 years after the bang (time of
“recombination”, creation of atoms)
c) To ~3 minutes after the bang (creation of
heavy nuclei)
d) To ~microsecond after the bang (creation of
protons)
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Clicker Question
Why can we only see so far back
into space?
a) Because before recombination the
light in the universe was
scattering off of the charged
particles
b) Because there are too many things
in the way which block our ability
to see Big Objects and Black Holes
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Dark Matter in Galaxies
Finished looking at the things
that produce light we can see in
a Galaxy
Move to the parts which have
most of the mass
Since Dark Matter doesn’t
interact much, expect it to
engulf the Galaxy
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Topic 1: Galaxies
The Planets and the Sun
General Relativity does
a good job of
predicting the planets
path around the sun
assuming virtually all
the mass of the Solar
system is located at
the Sun
– Only small influence
due to the small
masses of the
other planets
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Dark Matter in Galaxies
• 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
• Important properties of Dark Matter:
– Massive
– Neutral
– Doesn’t interact much
– Not sure when it shows up in the Universe,
but we think it was before protons could
form
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Prep For Next Time – L22
• Note: May change depending on how
far we get in lecture
• Reading:
– BBBHNM: All reading through
Chapter 17
• Pre-Lecture Reading Questions:
– All reading questions through 17
• End-of-Chapter Quizzes:
– If we finished Chapter 15 then endof-chapter quiz 15 (else just through
Chapter 14)
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Papers - 22
• Papers:
– Paper 0: Grades posted. Check to see that
you got the correct grade.
– Paper 1 Revision: No known problems
– Paper 2:
• Bad Rubric fixed (everyone given credit
for low-quality calibration)
• Finished re-grades
– Paper 2 Revision: Opened a new version.
Need to resubmit ONLY if you want. Was
due before class. Let me know if you need it
re-opened
– Paper 3: Text was due today before class
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Prep for Next time – L23
• Reading:
– Chapter 18
• Pre-Lecture Reading Questions:
– Chapter 18
• End-of-Chapter Quizzes:
– Chapter 15 (Already Done)
• Papers:
– Paper 2 Revision: Was due before class
today. Let us know if you were mis-graded
– Paper 3: Calibrations, reviews and Selfassessment due Wednesday before class
Big Bang, Black
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Prep For Next Time – L10
• Note: May change depending on how far we get in
lecture
• Reading:
–BBBHNM: All reading through Chapter 18
• Reading Questions:
– All reading questions through 18
• eLearning Quizzes:
– If we finished Chapter 15 then end-of-chapter
quiz 15 (else just through Chapter 14)
• Papers:
– Paper 3 revisions (if desired) due before class on
Tuesday
Big Bang, Black
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Topic 1: Galaxies
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For Next Time – L21
• Reading:
– (Unit 5)
• Pre-Lecture Reading Questions:
– Unit 5 Revision (if desired): Stage 1 due Monday
• End-of-Chapter Quizzes:
– Chapter 15 (if we finished Chapter 15, else just
14)
• Papers:
– Paper 3 Revision (if desired): Will be opened
after any regrade requests
• Honors Papers:
– (Stage 2)
– Final paper due on the last day of class
Big Bang, Black
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Topic 1: Galaxies
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For Next Time – L22
• Reading:
– (Unit 5)
• Pre-Lecture Reading Questions:
– Unit 5 Revision (if desired): Stage 1 due Monday
• End-of-Chapter Quizzes:
– Chapter 15 (if we finished Chapter 15, else just
14)
• Papers:
– Paper 3 Revision (if desired): Stage 1 due
Wednesday
• Honors Papers:
– (Stage 2)
– Final paper due on the last day of class
Big Bang, Black
Holes, No Math
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Topic 1: Galaxies
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Prep for Today (Is now due) – L20
• Reading:
– BBBHNM 15
• Reading questions:
– Chapter 15
• End-of-Chapter Quizzes:
– Chapter 14
• Paper Stuff
– Paper 2 Revision: Text was due already.
Calibrations and Review are due Monday
– Paper 3: Text was due already. Calibrations
and Review due Monday
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Prep for Today (Is now due) – L21
• Reading:
– BBBHNM 16
• Reading questions:
– Chapter 16
• End-of-Chapter Quizzes:
– Chapter 14
• Paper Stuff
– Paper 2 Revision: Calibrations and Review
were due before class
– Paper 3: Calibrations and Review were due
before class
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Prep for Next Time – P20
• Reading
– BBBHNM 16
• Reading questions
– Chapter 16
• End-of-Chapter Quizzes
– If we finished Chapter 15 then end-ofchapter quiz 15 (else just 14)
• Paper Stuff
– Paper 2 Revision: Text was due already.
Calibrations and Review are due Monday
– Paper 3: Text was due already.
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and Black
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Black 63 Bigand
Calibrations
Review
dueHoles
Monday
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Topic 1: Galaxies
Prep for Next Time – P21
• Reading
– BBBHNM 16
• Reading questions
– Chapter 16
• End-of-Chapter Quizzes
– If we finished Chapter 15 then end-ofchapter quiz 15 (else just 14)
• Paper Stuff
– Paper 2 Revision: Calibrations and Review
were due before class
– Paper 3: Calibrations and Review were due
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Big Bang,
Black 64
before
class
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Topic 1: Galaxies
Billions of Years go by…
• As the regions get smaller,
they spin faster and faster
• Eventually, when it comes into a
type of equilibrium, gravity
can’t pull it in any further and
the atoms stop speeding up
– Kinda like the planets going
around the sun
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The Transition From a “Charged”
Universe to a “Neutral” Universe
Some Time
Passes
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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
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Subtract Further
Since we understand the Doppler
effect we can subtract if off
to see what’s left
Remember: Overall
temperature is
2.728 degrees
Kelvin
Now looking at
VERY VERY small
variations
DT = 18mK
Extra light from the Milky way,
Subtract
this off also…Big Objects and Black Holes
Big
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How it all ends up…
An example galaxy
like our own
This explains why
some galaxies
• Look mostly flat
• Have a halo
• Bulge at the
center…
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For Next Time
Topics
• Galaxy Formation  Done
• Stars  Next
• Black Holes  After that
Reading for Next time:
BBBHNM: Chap 16
Full reading 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 (upto-page 159)
• TOE: Chaps. 1-3
Lecture prep: Turn in on eLearning
Two questions
from Chapter
you want to
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to 1: Galaxies
Topic
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Math the answer
70
Papers 1 and 2
• Paper 1 and 2 grades are
posted on eLearning
• Can’t get to the Paper 2
grading anymore
– If you would like the
opportunity to re-submit
Paper 2 I’ll open it for you.
Big 71
Bang, Black
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Topic 1: Galaxies
Papers 3 and 4
• Paper 3:
– Due Wed. March 24th before class
– Calibrations and grading due on
Friday at noon
– Now open
• Paper 4:
– Will be assigned after we start
Chapter 17
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Other Stuff
• Elearning:
– Unit 3 now due
– Unit 4 now due
– Unit 5 in progress
• Make sure you pick up the
latest version of the online
textbook!!!
Big Objects and
– Been
updating
itBlack
allHoles
semester73
Big Bang,
Black
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Topic 1: Galaxies
Look for variation in the Cosmic Background
Radiation
Full sky in a
single map
Temperature Map
Incredibly Uniform,
Stretch out a sphere but are there Small
onto a flat page
Variations?
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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 through 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)
Objects and Black Holes
• Bang,
TOE:Black
Chaps. Big
1-3
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Topic 1: Galaxies
75
Papers 1 and 2
• Done with grades for both
– Graded unfairly? Let us know!
– Want to do better? We can help!
• Want to revise Paper 2?
– CPR now open, due Friday at noon
– You are required to do the calibrations for
the new papers
– You are required to do the reviews for
your peers
– Overall grade will reflect both original
and Black Holes
paper
theObjects
revision
Big 76
Bang,
Black and Big
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Topic 1: Galaxies
Writing Assignments
Short Assignments 1 & 2
• Re-do’s are still possible.
Want to revise again? Talk to
me.
eLearning:
Unit 4 now
Need to be working on Unit 5
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Topic 1: Galaxies
77
77
Evolution of the Early Universe
Electrons
Protons
Atoms
Photons
Some Time
Passes
Photons
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78
The Story of Galaxy Formation
After the Big Bang we
just had lots of stuff
floating around in space
• Can think of it as a
giant tank of gas
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79
Papers AFTER Paper 2
Two options
1.Two short papers like the first one
• One on Black Holes (due mid Nov)
• One on Dark Matter (due last day
of class)
2.Research Paper
• If you want this option you must get
Stage 0 approved ASAP
• Was due last week
• Stage 1 due Thurs Nov 5th
•
Final
paper
due
the
last
day
of
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Big Bang, Black
80
80
class,
Tuesday
Dec
8
Topic 1: Galaxies
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So What?
• Ok... New idea of galaxy formation. Lots of kids jumping on a
trampoline, not just straight up and down, but in random
directions. Each time they hit the ground they create a little
dent in the trampoline. Sooner or later two of the kids, because
they will get near each other (perhaps because the dents make
them more likely to get near each other) will hit each other and
fall to the trampoline itself and create a big dent. The other
kids jumping near that dent are now more likely to be bounced
towards the center (because of the indentation) and collide with
the other kids making an even bigger dent. Eventually, all the
kids that are nearby the dent will be located in the same place.
•
If we start with all the kids equally spaced, then it will
take longer to get that first big collision. If two of the kids
start nearer each other, then we're more likely to get a
collision sooner and get all the kids at the big dent sooner.
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81
Tigers in a Jungle
Let’s say we have a jungle with a number
of hungry tigers looking for food
If a tiger finds food they will get bigger
and be more effective at hunting
If they don’t find food, they won’t grow
and will starve, maybe get eaten by
another tiger
Since there is only so much food, it’s just
a matter of time before we are left
with a few well-fed tigers
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82
Not all Tigers are Located Equally
• Tigers nearer the food:
– Will get to eat slightly sooner
– Will be more energetic sooner, can go
hunting sooner and be a more effective
hunter sooner
 more likely to bigger quicker and thrive
• Tigers farther from the food:
– Will be longer until they eat and become
effective hunters
– Less food available if they get there later
 more likely to die
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Topic 1: Galaxies
83
Tigers in the Universe
• If all the Tigers are equally spaced
then it will take longer, on average,
before all the food is gone and we’re
left with a few well-fed tigers
• If there are “fluctuations” then some
of the Tigers will start closer and have
an advantage over other tigers  it will
take less time to have a Universe with
a few well-fed tigers
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Topic 1: Galaxies
84
Where is the party?
• How long it takes to get a good size Friday night
party can depend critically on how many cute people
there are at the beginning of a party
• Scenario 1) If a bunch of cute people happen to be
at same place early in the night  won’t take long
before LOTS of people will be attracted to that
party
• Scenario 2) If all the cute people are evenly
scattered all over then people who get to a party
might leave to see if there are more cute people
somewhere else  Will take longer before everyone
settles on a party and stays there
• Bottom line: Takes much less time to get a set of
good sized parties if the number of cute people isn’t
exactly uniform
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Topic 1: Galaxies
85
The Cosmic Background Radiation
The
famous
results
from the
WMAP
satellite
experiment
Big Bang, Black
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Topic 1: Galaxies
86
Look at the Spots
Look at the average separation of the spots
• Probes the geometry of space-time
– Not a simple relationship between the separation
of the spots and the geometry of space time
• Essentially:
– Lots of Mass (large density) Lots of clumping of
matter  Closed Universe
– Medium amount of Mass (medium density)  Some
clumping  Flat Universe
– Small amount of Mass (small density)  Small
clumping  Open Universe
• Model the different possibilities with a computer
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Topic 1: Galaxies
87
Ok… The Ripples are
WHERE the galaxies
form, but HOW do
they form?
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Topic 1: Galaxies
88
Wait a Billion Years
After less than ~1 billion
years, galaxies and the first
stars form
Formation of
the first stars
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Topic 1: Galaxies
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Today’s Lecture
• Overview of the story
• The Cosmic Background
Radiation data and why we
believe in our models of
Galaxy formation
• Example of Galaxy
Formation
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Schedule from Here on Out
• Mon Nov 10th: 22nd lecture (today): Galaxy Formation
– 1 page Research topic proposal due, must be
approved
– Rest of the semester reading due
• Wed Nov 12th: 23rd lecture: Stars
– Early version of Short Paper 2 due if you want
comments back early
• Mon Nov 17th: 24th lecture: Black Holes
• Wed Nov 19th: 25th lecture: Inflation
• Mon Nov 24th: 26th lecture: Dark Energy
• Wed Nov 26th: No class
– Research paper and 2nd short paper due at midnight
– Day before Thanksgiving. Class cancelled
• Dec 1st: No classes redefined day
• Dec 3rd: Reading
period,
no
classes
Big
Objects
and
Black Holes
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• DecNo8Math
: Finals week,
no final
Topic
1: Galaxies
Holes,
Looking for Ripples
To an excellent degree of precision the
temperature of the photons in the
Universe today is incredibly uniform
Gives us
confidence that
our story of
the Big Bang
and the
Evolution of
the Universe is
correct
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92
Hotter and Colder?
Colder here?
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Hotter here?
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Topic 1: Galaxies
93
Perfectly Flat?
Subtract off the same amount
everywhere
The overall temperature is
2.728 degrees Kelvin
The variation is very small
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Topic 1: Galaxies
94
Doppler Effect
Take into account
our relative speed
to the rest frame
of the photon
background
Earth is going
around the sun at
30 km/sec and
the solar system
is rotating around
the Milky Way at
250 km/sec
Big Bang, Black
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Moving away from this direction
Moving in this direction
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95
Subtract Further
Since we understand the Doppler
effect we can subtract if off
to see what’s left
Remember: Overall
temperature is
2.728 degrees
Kelvin
Now looking at
VERY VERY small
variations
Extra light from the Milky way
Subtract
this off also…Big Objects and Black Holes
Big
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Topic 1: Galaxies
96
Large Scale Structure
Distribution of bright galaxies in the Virgo region
indicates the Virgo cluster and presence of more
Big Objects and Black Holes
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distant, largerTopic
scale
structure
97
1: Galaxies
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Large Scale Structure (2)
A large survey
of distant
galaxies shows
the largest
structures in the
universe:
Filaments and
walls of galaxy
superclusters,
and
voids, basically
empty space.
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Topic 1: Galaxies
98
What if we’re moving?
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Topic 1: Galaxies
99
The Cosmic Background Radiation
The Famous COBE satellite map of the allsky structure of the Cosmic Background
Radiation
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Topic 1: Galaxies
100
• Add pictures from Seeds on
whether we believe the
structure formed first and then
galaxies formed
• Or if the galaxies formed and
then combined to create
structure
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Topic 1: Galaxies
101
The Growth of Clusters of Galaxies
Structures in the Universe could
have developed in two
fundamentally different ways:
a) Small structures (galaxies)
could have developed first, then
clustering into larger and larger
structures
b) The largest structures
(superclusters, voids) could have
developed first, then breaking
up into smaller and smaller
units.
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The latter scenario seems to be
favored by observational evidence.
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102
Topic 1: Galaxies
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
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BHOT 7 cont..,
• New CMB results: tiny ripples in the CMB can
be used as an indicator of the large-scale
geometry of the universe and they appear to
indicate that the universe is flat after all
• Since there doesn’t seem to be enough matter
and dark matter to account for this,
physicists have postulated the existence of
another as yet undetected substance to
explain it
• Dark Energy
• More on tall this stuff later… Supernovae
results…
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TFTM 3 cont…
• WMAP Pictures on variation in the
temperature?
• Some cool numbers: Earth is going
around the sun at 30 km/sec and
the solar system is rotating around
the Milky Way at 250 km/sec.
• Fix this number: 1 billion photons
per nuclear particle in the average
contents of the universe
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Topic 1: Galaxies
105
• The three WMAP pictures…
– Flat
– Dipole
– Variation
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106
• Slide 29
Maps based on 53 GHz (5.7 mm
wavelength) observations made with
the DMR over the entire 4-year
mission (top) on a scale from 0 - 4
K, showing the near-uniformity of
the CMB brightness, (middle) on a
scale intended to enhance the
contrast due to the dipole
described in the slide 19 caption,
and (bottom) following subtraction
of the dipole component. Emission
from the Milky Way Galaxy is
evident in the bottom image.
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107
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• This is some
text…
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• Eventually, when the region got
small enough it would be spinning
fast enough to balance the
attraction of gravity to balance the
attraction of gravity and in this
way, we believe, disk-like rotating
galaxies were born
• Others would form other times of
galaxies like elliptical galaxies
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111
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112
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SHU 5 cont…
• Pictures of the ripples
• Page 107
• COBE launched in 1989 (Nobel
prize for this in 2006),
• Picture on Page 112
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Topic 1: Galaxies
116