Big Bang, Black
Holes, No Math
ASTR/PHYS 109
Dr. David Toback
Lecture 26
Big Bang, Black
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Early Times & Fate of the Universe Topic 1:
Possibilities
1
Was due Today – L26
• Reading:
– (Unit 6)
• Pre-Lecture Reading Questions:
– Unit 6, Stage 2
• End-of-Chapter Quizzes:
– Chapter 17
• Papers:
– Paper 4, Stage 1: due Wednesday before class
• Honors Paper:
– Stages 1 & 2 must be approved explicitly
– Final paper due on the last day of class
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Early Times & Fate of the Universe
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End of Semester
• Class today and
Wednesday
• No class next Monday
(redefined as Friday)
• Last class is next
Wednesday
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Course Evaluations
Course evaluations will be done online:
• I believe you should have gotten
an email about this already
The Fall 2015 evaluation period:
• Begins Mon Dec 7th, 8AM
(http://evaluation.tamu.edu/)
• Ends Wed Dec 23rd, 5PM
Please do them… won’t take long
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Unit 6
Going back in time and going
forward in time
Before the first millionth of
a second
and the
Fate of the Universe
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Topic 1: Possibilities
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Outline of Unit 6
1.Possible Fates of the Today
Universe, Dark Matter and
Dark Energy
2.Particle Physics, Dark
Matter and the Very Early
Universe
3.Inflation
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Caveats
While the data is VERY powerful, some of
the interpretations of the data are not
fully “proven” or understood
Still need data to tell us about the
theory, and theory to tell us about the
data
New data and theoretical advances have
recently changed our understanding of
the Universe
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The Fate of our Universe
Will the Universe continue expanding
forever?
• That depends, mostly, on a few
things:
1. How fast is it expanding now
2. How much STUFF there is in
the Universe
3. How big it is now
4. Are the laws of physics really
understood?
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Why the first three are so important
• Gravity is trying to pull
space-time back together
again
–Attractive force
• Either it’s strong enough to
pull the universe back
together again, or it isn’t
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What about that last issue?
• Dark Energy fits into this story, but it
is an effect that only impacts on the
largest scales
• Takes 10 billion years and HUGE
distance scales to have ANY effect
• Start by discussing all-but-Dark Energy
first (gravity), then come back to it
– Kinda like when we did the expanding
universe
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Gravity: Three Possibilities
There are only a
few possibilities
Use an analogy…
Shooting a bullet
into the air at
the surface of
the Earth
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Possibility 1: Small Speed
Universe ends in a Big Crunch
• If the bullet is shot up with a small
speed, gravity will eventually stop it
and it will fall back to the Earth
• Can think of the gun shooting the
bullet as an explosion (our big bang)
• If the “Bang” is too small, all the
stuff in the Universe will eventually
all fall back together as the spacetime collapses on itself… like a giant
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black
Topic 1: Possibilities
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Continue the analogy…
It’s a balance between the
speed of the bullet and the
density of the object the
bullet is trying to leave
Does the bullet have a
speed below the escape
velocity?
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& Fate of the Universe
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Topic 1: Possibilities
A bullet has a speed smaller
than the escape velocity
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The Sun
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Topic 1: Possibilities
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Possibility 2: Big Speed
Universe expands forever
If the bullet has a speed greater
than the escape velocity, gravity
will not be strong enough to pull it
back
 Will keep on going away from
the Earth forever
 Like launching a rocket into
outer space but using a slingshot,
not thrusters that keep firing
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The Moon has a “small” escape Velocity
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To infinity and beyond
• As the bullet gets further and further
from the moon the gravitational
attraction gets smaller and smaller… It
still slows the bullet down, but less and
less…
• Eventually, the attraction is so small
(since they are so far away from each
other) that the bullet effectively moves
off into space at the same speed
forever
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Back to the Universe
• Since there is a lot of mass in
the Universe, if it were
expanding slowly enough the
force of gravity would cause it
to eventually stop expanding and
then start contracting again
• Even with a large speed today
gravity might force it to stop
expanding and then contract
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A Universe Ending in a Big Crunch
• Remember this is only an
analogy  There is no center or
edge of the Universe
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A Universe That Expands Forever
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How do we tell which is right?
• Looking at distant galaxies shows that
the Universe is expanding
• Since there is lots of mass in the
Universe, the expansion should be
slowing down
– Like a ball thrown up into the air, it
should slow down
– Question: How much is it slowing
down? Do an experiment!
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How do we measure the deceleration?
•Look at Supernovae
since they are
REALLY bright for
about a month so
we can see them
from far away
•We believe we
understand these
explosions really
well
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Measuring the “Deceleration” of the Universe
• Can use the brightness of
Supernova to tell how far they are
away
• Can use spectral lines to tell how
fast
they
are
moving
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& Fate of the Universe
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What Does the Data Say?
• The most distant things in the Universe are
further away than we think they should be
• The Universe doesn’t appear to be slowing
down, it’s speeding up!
• Accelerating!
• It’s like there was an explosion and then
something CONTINUES to force the stuff
further apart
• Throw a ball into the air and the ball
speeds up!??!
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The Accelerating Universe
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Fate of The
What the ???
•Is there some Force that
that is pushing things apart
faster?
•Gravity, as we know it,
only attracts… Give it a
name: Dark Energy
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Why do we call it Dark Energy?
• Can’t see it
Call it Dark
• Doesn’t seem to interact gravitationally
like mass
 Not mass or matter, but is forcing
the Universe apart so it has energy
(E=mc2). Not Dark Matter
• From the acceleration can measure how
much energy must be “doing the forcing”
~72%
theTimes
critical
& Fate density
of the Universe
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Dark Energy and Dark Matter
related?
• Not clear dark matter and dark energy
have anything to do with each other
– Just because we use the word DARK
for both doesn’t mean we know how
they are related
• Probably IS something fundamental that
is similar, but we don’t know enough
about either to say anything useful yet
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It all adds up!
• Add up all the mass/energy in the
Universe
– Atoms account for ~5%
– Dark Matter is about 5 times more
mass in a galaxy than atoms  ~23%
– Dark Energy is about
~72%
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The Evolution and Fate of the Universe
Dark Energy overcomes the
deceleration of Gravity about 6
billion years ago, Universe
starts accelerating
Deceleration
due to
Gravity for
the first 6
billion years
Dark Energy Makes the
Universe Accelerate (keep
expanding Faster and faster)
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We don’t
know the
nature of
Dark
Energy
 Lots of
possible
Fates…
but it
looks like
we’ll
expand
forever…
and it
could get
REALLY
cold!
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Early Times & Fate of The Universe Topic 5: Dar
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Energy
Lots of Questions
How will we figure
out the fate of
the Universe?
Need to know the
Nature of Dark
Energy
What is Dark
Energy?
We don’t know
yet… Just
starting to have
ideas..
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This result was so important that it was
Early Times & Fate
of the
awarded
the Universe
Nobel Prize for 2012 33
Topic 1: Possibilities
For Next Time – L26
• Reading:
– (Unit 6)
• Pre-Lecture Reading Questions:
– Unit 6 Revision (if desired), Stage 1: Due Wednesday before
class
• End-of-Chapter Quizzes:
– If we finished Chapter 18, then Chapter 18 (if not, then just
Chapter 17)
• Papers:
– Paper 4, Stage 1: due Wednesday before class, but Stage 2
is due Monday!!
• Honors Paper:
– Stages 1 & 2 must be approved explicitly
– Final paper due on the last day of class
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End of the Semester - Part 1
• End of Chapter quizzes
• All quizzes due by Wed December 16th at 11:55PM
• This includes AMS 2
– End of semester measure of some of the things
you learned
– Will need to do it before you can finish all the
end of chapter quizzes
– If they are not complete, you will get an Incomplete
for the course
• If you need an extension, let me know ahead of
time
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Early Times & Fate of the Universe
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End of Semester Part 2
• Grades:
– All paper and PLRQ grades are in
CPR and won’t get ported to
eCampus
– Will start calculating grades after
Dec 16th
– Please do the Course Evaluations
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2 paragraph in-class quiz
• Paragraph 1: What are the
most important properties of a
black hole?
• Paragraph 2: How do black holes
form?
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1 Paragraph in-class Quiz
What is the evidence for
stellar black holes?
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Clicker Question
Can you "fill up" a black
hole?
a) Yes
b) No
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Clicker Question
Can a Black Hole orbit
another star?
a) Yes
b) No
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Clicker Question
Could the Earth
orbit a black hole?
a)Yes
b)No
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Clicker Question
What would happen if two black
holes collided?
a)They would make a supermassive
black hole
b)They would just make a black
hole that is the mass of the two
black holes that started
c) Black holes can’t collide
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Clicker Question
If there really is dark energy,
what is the ultimate fate of our
universe?
a) Big crunch
b) Expand forever, but slowing
down
c) Expand forever, but speeding
upBlack Early Times & Fate of the Universe
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Topic 1: Possibilities
Clicker Question
What does dark energy do to the
photons in the universe?
a) Makes them more energetic by adding
energy to the universe
b) Stretches them by stretching spacespace time making them more
energetic
c) Stretches them by stretching spacespace time making them less energetic
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Clicker Question
Dark energy is forcing the
universe to accelerate. What is
accelerating?
A) The galaxies moving through
space
B) The expansion of space-time
C) Only the dark matter
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Clicker Question
What is happening to the
density of the universe over
time?
a) Increases
b) Decreases
c) Stays the same
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Clicker Question
If space-time is expanding, why aren't
atoms expanding?
a) They are
b) Because the electric charge attraction
and quantum mechanics keep the
atoms the same size in space
c) Both are true, but A is a more
important effect than B
d) Both are true, but B is more true
that
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Topic 1: Possibilities
Clicker Question
What does dark energy do to the
temperature in the universe?
a)Raises it by adding energy to
the universe
b)Lowers it by stretching spacetime
c) Dark Energy doesn’t affect
temperature
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Topic 1: Possibilities
Clicker Question
What will happen to galaxies 100 billion
years in the future?
a) They'll stay the way they are now
because dark matter will keep them
together
b) They'll slowly get ripped apart because
dark energy will expand the universe so
quickly it will overcome the attraction
of gravity
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If space-time is expanding, why
isn't our galaxy expanding?
A) It is
B) Because the gravitational attraction of
masses pulls the galaxy back together
again
C) Both are true, but A is a more
important effect than B
D) Both are true, but B is more true that
A.
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Let's say I have two galaxies in space and
they are exactly stationary relative to each
other. Over a billion years, what will
happen?
A) They will attract each other by gravity so
that they are moving towards each other
B) They will each expand as space-time expands,
and the distance between them will grow as
space-time expands
C) The galaxies will stay the same size, and the
distance between them will grow as space-time
expands.
D) It depends on the overall distance between
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them.
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If the acceleration of the universe
continues, will we ever notice this with our
own eyes?
A) No, only very sensitive
experiments can measure the
expansion of the universe
B) Yes, it is just a matter of time
before the nearest stars are so far
away from us that we can't see
them anymore.
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Possibility 3: In between
• It will approach zero speed as it
gets farther from the Earth
• It’s true that it can orbit the
Earth it has just the right
speed, but that’s not what we
are talking about here…
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Look at it the Other Way
Since we can observe the speed of
the expansion of the Universe we ask
the question the other way
“Is the density of the universe big
enough to make the Universe
contract again?
Collapse back on itself?
A Big Crunch?”
Timesa
& Fate
of the Universe
Big Bang,
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Does
have
“critical”
density?
55
Topic 1: Possibilities
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Summary: 3 Possibilities
1.Over the critical density: Collapse
(an anti-big bang, or a Big Crunch,
Gnab Gib)
2.Under the critical mass: Expanding
forever, but slows down and
eventually hits a constant speed
3.Exactly critical mass: Eventually
stops expanding just barely
enough… Speeds get smaller and
smaller, although never quite
reaches zero
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Look at all three together
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Topic 1: Possibilities
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Critical Density
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Well?
• Which universe do we
live in?
• Need to know the
present rate of
expansion and the
density of the universe
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Topic 1: Possibilities
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Measure Both
• Can measure the speed of expansion
fairly accurately
– What Hubble originally measured
• What do we know about the density of
the Universe?
– Add up the mass of all the stars we
can see
– Add in all the stuff between the stars
(hydrogen and helium gas)
This density is about 5% of the critical
density
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& Fateup
of the
Universe
Big
Black
• Bang,
Dark
Matter
makes
about
23%
60
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Topic 1: Possibilities
Below the Critical Density?
• The naïve scientist would
conclude that we “must” be in a
Universe that would expand
forever
• Is this right?
• How could we check this?
• Any evidence we’re missing
something?
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Topic 1: Possibilities
Other Ways?
Are there other ways to
predict the Fate of the
Universe?
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Topic 1: Possibilities
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The Data
Measure the Density of
the Universe from the
Cosmic Background
Radiation
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Topic 1: Possibilities
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The Cosmic Background Radiation
Look at the size
of the spots
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Topic 1: Possibilities
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Look at the Spots
We know what the size of the spots
should be back during recombination, but
we can ask how much the light was lensed
as it moved through space
Big
Crunch
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Critical
Density
Expands
Forever
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Topic 1: Possibilities
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Computer Simulations
Big
Crunch
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Critical
Density
Early Times & Fate of the Universe
Topic 1: Possibilities
Expands
Forever
66
Which Universe Do We Live In?
Big Crunch
Critical
Expand Forever?
Looks like
a
Universe
The
with the
Data
Critical
Density67
Early Times & Fate of the Universe
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Topic 1: Possibilities
Summarizing the Data
1. Speed of far-away galaxies moving
away from us gives us the speed of
expansion fairly accurately
2. The measured density of the “known
matter and dark matter” is about is
about 28% of the critical density
3. The background radiation says the
density is consistent with being 100%
of the critical density
Something is inconsistent…
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It all adds up!
• Add up all the mass/energy in the
Universe
– Atoms account for ~5%
– Dark Matter is about 5 times more
mass in a galaxy than atoms  ~23%
– Dark Energy is about
~72%
Cosmic Background
Radiation says the
Universe has
100%
of
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the
critical
density
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Early Times & Fate of The Universe Topic 5: Dark
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Energy
Was due today– L26
• Reading:
– Already due
• Pre-Lecture Reading Questions:
– Already due
– Can do make ups in CPR. Instructions at
http://people.physics.tamu.edu/toback/109/Question_Guideline_109_CPR.pdf
– Will need to submit 4 questions, and do the entire CPR
assignment to get credit
• End-of-Chapter Quizzes:
– All end-of-chapter quizzes are due by 11:55PM of Monday
December 2nd. This includes AMS-2
• Papers:
– Paper 3: Working on recent re-grade requests
– Paper 3 Revision: Text due tomorrow before 4:10PM. Rest of
assignment. Monday before 4:10PM
– Paper 4: Text due tomorrow before 4:10PM. Rest of
assignment. Monday before 4:10PM
Early Times & Fate of the Universe
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Topic 1: Possibilities
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Prep for Next time – L26
• Reading:
– Already due
• Pre-Lecture Reading Questions:
– Already due. If you want to do a make up, you
need to email me
• End-of-Chapter Quizzes:
– All end-of-chapter quizzes are due by 11:55PM
of Monday December 2nd. This includes AMS-2
• Papers:
– Paper 3: Working on recent re-grade requests
– Paper 3 Revision: Text due Monday before class
– Paper 4: Text due Monday before class
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Course Evaluations
Course evaluations will be done online:
• You should have gotten an email about
this already
The Fall 2013 evaluation period will:
• Begin on Wednesday November 27th at
8AM
• Ends on Friday December 13th at 5PM
– Please do them… won’t take long
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Adding it up
• Atoms and the other
known particles make
up about 5% of the
Critical Density
– Most in atoms
– Other stuff in
photons, neutrinos
etc.
• Dark Matter makes up
about
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Look at the Spots
Look at the average separation of the spots
• Essentially:
– Large amount of mass (large density)
Large distance between spots  Big Crunch
– Medium amount of Mass (medium density)
Medium distance between spots  Critical
Density
– Small amount of Mass (small density) 
Small distance between spots  Universe
expands forever
• Model the different possibilities with a
computer
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Which Universe Do We Live In?
Crunch
Critical
Forever?
Looks like
a
Universe
The
with the
Data
Critical
Density75
Early Times & Fate of the Universe
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Topic 1: Possibilities
End of the Semester – L12
• Only 3 more days of class
– Today, Nov 20th, and Nov 27th
• Need to finish all the end of Chapter
quizzes as well as AMS 2
– That’s the end of semester evaluation
– Need to finish this before you can
finish all the end of chapter quizzes
• Will not do the 5th paper, but will allow
a paper 4 revision
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End of the Semester – L13
• All Reading Questions are now due
• Chapter 17 End of Chapter questions now due
• All chapters due by Tues Dec 4th at midnight
• Only 2 more days of class
– Today, and Nov 27th
• Need to finish all the end of Chapter quizzes as well as AMS 2
– That’s the end of semester evaluation
– Need to finish this before you can finish all the end of
chapter quizzes
– If they are not complete, you will get an Incomplete for the
course
• Will not do the 5th paper, but will allow a paper 4 revision with a
short time scale
– Text due Monday Dec 3rd
Early
– Rest
due by
Dec Times
7th & Fate of the Universe
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Topic 1: Possibilities
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Prep For Next Time – L12
• Reading:
–BBBHNM: All reading through Chapter 20
•Reading Questions:
– All reading questions through 20
• eLearning Quizzes:
– Chapter 18
• Papers:
– Text of Paper 4 assignment due
Wednesday at 11:55PM
– Calibrations, Reviews and Self-assessment
due before class on Monday
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Prep For Next Time – L12
• Note: May change depending on how far we get in
lecture
• Reading:
–BBBHNM: All reading through Chapter 20
• Reading Questions:
– All reading questions through 20
• eLearning Quizzes:
– If we finished Chapter 18 then end-of-chapter
quiz 18 (else just through Chapter 17)
• Papers:
– Text of Paper 4 assignment due Wednesday at
11:55PM
– Calibrations, Reviews and Self-assessment due
before class on Monday
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Prep For Next Time – L12
• Reading:
–BBBHNM: All reading through Chapter
20
•Reading Questions:
– All reading questions through 20
• eLearning Quizzes:
– Quizzes through Chapter 17
• Papers:
– Text of Paper 4 assignment due
before class on Tuesday
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Prep For Next Time – L13
• Note: May change depending on how far we get in
lecture
• Reading:
–BBBHNM: All reading through Chapter 20
• Reading Questions:
– All reading questions through 20
• eLearning Quizzes:
– If we finished Chapter 18 then end-of-chapter
quiz 18 (else just through Chapter 17)
• Papers:
– Rest of Paper 4 assignment due before class on
Tuesday
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Prep for Next Time – P24
• Reading
– Reading the rest of BBBHNM
• Reading questions
– Chapter 18, 19 and 22 (can do in installments)
• End-of-Chapter Quizzes
– If we finished Chapter 18 then end-of-chapter
quiz 18 (else just 17)
• Papers
– Paper 2 Revision or Paper 3: Misgraded? Let us
know.
– Paper 3 Revision: Due Monday before class. Want
feedback? Due Thursday for quick response
– Paper 4: Due Wednesday before class. One week
after
Big Bang,
Blackwe finish Chapter 17
82
Holes, No Math
Prep for Next Time – P25
• Reading
– Reading the rest of BBBHNM
• Reading questions
– Chapter 18, 19 and 22 (can do in installments)
• End-of-Chapter Quizzes
– If we finished this lecture, do Chapter 18, 19
and 22 (else just 17)
• Papers
– Paper 1, 2 or 3: Misgraded? Let us know
– Paper 3 revision: Was due today, Reviews due
next Monday
– Paper 4: Due Wednesday (same format as last
two papers)
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83
Prep for Next Time – P26
• Reading
– Reading the rest of BBBHNM
• Reading questions
– Chapter 18, 19,20 and 22 (can do in installments)
• End-of-Chapter Quizzes
– If we finished this lecture, do Chapter 18, 19
and 22 (else just 17)
• Papers
– Paper 1, 2 or 3: Misgraded? Let us know
– Paper 3 revision: Was due Monday, Reviews due
next Monday
– Paper 4: Was due today (same format as last
two papers), Reviews due next Wednesday
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84
Full set of Readings So Far
• Required:
– BBBHNM: Chaps. 1-19
• Recommended:
– TFTM: Chaps. 1-5
– BHOT: Chaps. 1-7, 8 (68-76), 9 and
11 (117-137), 12
– SHU: Chaps. 1-3, 4(77-86), 5(95114), 6-8 (up-to-page 164)
– TOE: Chaps. 1-3
– Seeds (Cosmology in the 21st Century)
Big Bang, Black
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The Cosmological Constant
• Back in the 1920’s, when
there was no evidence that
the Universe was
expanding, Einstein tried to
explain why it wasn’t
collapsing
• He put in a special “forcetype thing” in General
Relativity so that it
wouldn’t predict that the
Universe was decelerating
• Call this “trick” the
Cosmological Constant
Big Bang, Black Holes, No Math
Big 86
Bang, Black Early Times & Fate of The Universe Topic 5: Dark
Holes, No Math
Energy
The Cosmological Constant?
The story goes that when
Einstein saw Hubble’s data
that the Universe is
expanding he called this
trick his “greatest blunder”
• Was Einstein right after all
(albeit for the wrong
reasons)?
• Is this “force” accelerating
the way the Universe is
expanding?
Big Bang, Black Holes, No Math
Big 87
Bang, Black Early Times & Fate of The Universe Topic 5: Dark
Holes, No Math
Energy
Prep for Today (Is now due) – L24
• Reading:
– BBBHNM 18 & 19
• Reading questions:
– Chapter 18 & 19
• End-of-Chapter Quizzes:
– Chapter 17
• Paper Stuff
– Paper 1, 2 or 3: Misgraded? Let us know
– Paper 3 revision: Due Monday
– Paper 4: Due Monday (same format as last
two papers)
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Prep for Today (Is now due) – L25
• Reading:
– Rest of BBBHNM
• Reading questions:
– Chapter 18, 19 and 22
• End-of-Chapter Quizzes:
– Chapter 17
• Paper Stuff
– Paper 1, 2 or 3: Misgraded? Let us know
– Paper 3 revision: Was due today, Reviews
due next Monday
– Paper 4: Due Wednesday (same format as
last two papers)
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Prep for Today (Is now due) – L26
• Reading:
– Rest of BBBHNM
• Reading questions:
– Chapter 18, 19, 20 and 22
• End-of-Chapter Quizzes:
– Chapter 17
• Paper Stuff
– Paper 1, 2 or 3: Misgraded? Let us know
– Paper 3 revision: Was due Monday, Reviews
due next Monday
– Paper 4: Was due today (same format as
last two papers), Reviews due next
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Wednesday
Holes, No
Math
End of the Semester – L26
• Only 2 more days of class
– Today and next Monday
• Will try to cover all but Chapter 21
• Need to finish all the end of Chapter
quizzes as well as AMS 2
– That’s the end of semester evaluation
– Won’t do Chapter 21 in eLearning
• Will not do the last paper, but will allow
a paper 4 revision
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
91
Some Recent Results
• Short and Sweet lecture on some
interesting data from the last ten
years
• This new data has completely
changed our view of the evolution
and fate of the Universe
• Still working on this stuff… Take it
with a grain of salt…
Big 92
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Big Bang, Black Holes, No Math
Early Times &
Fate of The
Overview of Section 6
The things that determine the
Fate of the Universe are the
dominant effects in the VERY
early Universe
Thus, to understand either
requires learning about both
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
93
Prep for Next Time – P24
• Reading
– BBBHNM 19 & 20
• Reading questions
– Chapter 19 & 20
• End-of-Chapter Quizzes
– If we finished Chapter 18 then end-of-chapter
quiz 18 (else just 17)
• Papers
– Paper 1, 2 or 3: Misgraded? Let us know
– Paper 3 revision: Due Monday
– Paper 4: Due Monday (same format as last two
papers)
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94
Today’s Lecture: Outline
The Fate of the Universe is
determined by what type of
Universe we live in
• Different Models of the Fate of
the Universe
• The impact of each and how we
could tell
• What the data says
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
95
What Type of
Universe do we live
in?
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Early Times & Fate of the Universe
Topic 1: Possibilities
96
Course Evaluations
This semester course evaluations
will be done online
"Department of Physics On-Line
Course Evaluation System“
http://evaluation.tamu.edu/
Please, take a few minutes to fill
these out. I really appreciate
it!
97 Bang, Black
Big
Holes, No Math
Schedule from here on out
• Mon Nov 22: Ch 19 & 20(?)
• Wed Nov 24: No class, Thanksgiving
(paper 4 due)
• Mon Nov 29: Ch 20 & 21 (?)
• Wed Dec 1: Ch 21 & 22
– last day of class
– paper 5 due
– Honors paper due
Big Bang, Black
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98
Course Evaluations
This semester two separate course
evaluations will be done online (until
Midnight, Tues May 4th)
1. "Department of Physics On-Line
Course Evaluation System“
http://evaluation.tamu.edu/
2. SLATE Award Evaluations
http://pica.tamu.edu
Please, take a few minutes to fill
Big Bang, Black
Holes,these
No Math out. I really appreciate it!
99
For Next Time
What are we missing?
• Chap 19: Evidence for Dark Matter
After that
• Chap 20: Particle Physics
• Chap 21: Inflation
• Chap 22: Dark Energy
Full reading through Unit 6:
• BBBHNM: Chaps. 1-22
• TFTM: Chaps. 1-5
• BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137), 12
• SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (up-to-page 164)
• TOE: Chaps. 1-3
• Seeds (Cosmology in the 21st Century)
Lecture prep: Turn in on eLearning
Two questions from Chapter 19 you want to know the answer to
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
100
The Reading for Unit 6
Full reading for Unit 6:
• BBBHNM: Chaps. 18-22
• SHU: 8 (159-164)
• BHOT: 11 (122-137), 12
• Seeds (Cosmology in the 21st Century, Web Handout)
Full reading through Unit 6:
• BBBHNM: Chaps. 1-22
• TFTM: Chaps. 1-5
• BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-137),
12
• SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (upto-page 164)
• TOE: Chaps. 1-3
• Seeds (Cosmology in the 21st Century)
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Topic 1: Possibilities
101
Papers
• Paper 1 is done
• Paper 2 grades are on eLearning
– All grades fixed, revision papers posted
• Paper 3:
– We have fixed papers for calibration problems
– Still mis-graded? Let us know!
– Do CPR if you submitted a revisions
• Paper 4:
– Due next Monday before class
• Paper 5 (last paper, no final)
– Assigned after we start Chap 20
Big 102
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Writing Assignments
Short Assignments 1 & 2
Re-do’s are still possible.
Want to revise again? Talk to
me
eLearning:
Unit 5 now due
Need to be working on Unit 6
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
103
Papers AFTER Paper 2
Two options
1.Two short papers like the first one
• One on Black Holes (due Thursday
before class)
• One on Dark Matter (due last day
of class)
2.Research Paper
If you want this option Stage 1 must
be approved ASAP
• Was due last week
• Final paper due the last day of
Early Times & Fate of thethUniverse
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Black
104
Tuesday
Dec
8
Topic 1: Possibilities
Holes, No Math
Today’s Lecture: Evidence
• Using the Density to predict the
Fate of the Universe
• Measuring the Curvature of
Space-Time to predict the Fate
of the Universe
• Measuring the Curvature of
Space-Time
• Summarizing the data so far…
Big Bang, Black
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Topic 1: Possibilities
105
Density of the Universe and General Relativity
General
Relativity
teaches us that
the Density of
the Universe
determines the
Curvature of
Space-Time
Big Bang, Black
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Remember, we’re not
talking about local
curvature, but the
curvature of the entire
universe
Early Times & Fate of the Universe
Topic 1: Possibilities
106
Density of the Universe and General Relativity
What type is our
Universe?
• Local
depression?
• Essentially
Flat?
• Something else?
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
107
Size scale of the Universe
Look at the Same Picture Again
Big Bang, Black
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Universe will expand forever
Universe will collapse again
Early Times & Fate of the Universe
Topic 1: Possibilities
The
curvature
of the
Universe
may tell
us the
fate
108
Other Ways?
Can we measure the
curvature of the Universe?
Is the evidence
consistent with a curved
(open) universe?
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Topic 1: Possibilities
109
Surface of a sphere
2-dimensional analogy
of the Universe
For a creature living on the
sphere, having no sense of
the third dimension, there’s
no center (on the sphere!):
All points are equal
Alternative: Any point on
the surface can be defined
as the center of a
coordinate system
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
110
Shape and Geometry of the Universe
Flat surface
(zero curvature)
Closed surface
(positive curvature)
Open surface
(negative curvature)
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
111
Shape and Geometry of the Universe
How can a 2-D
creature investigate
the geometry of the
sphere?
Measure curvature of
its space!
180
270?
Question: How many
degrees in a
triangle?
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
112
The Expanding Universe
The fate of our expanding
Universe depends, mostly, on
two things:
1. How fast is it expanding
now
2. The density of the
Universe
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Topic 1: Possibilities
113
Size scale of the Universe
Draw This Out
Big Bang, Black
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Density less than the critical density
 universe will expand forever
Density more than the
critical density  Universe
will collapse again
Early Times & Fate of the Universe
Topic 1: Possibilities
114
Measuring the Density
• What do we know about the
density?
– Add up the mass of all the
stars we can see
– Add in all the stuff between
the stars
The observed density is about
4% of the critical density
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
115
For Next Time
• Evidence we are in a critical Universe
• After that:
– Other stuff out there?
Reading for next time:
BBBHNM: Chapter 15 (assuming I finish it)
So far:
• BBBHNM: Chaps. 1-15
• TFTM: Chaps. 1-5
• Prelude
• BHOT: Chaps. 1-7, 8 (68-76), 9 and 11 (117-122)
• SHU: Chaps. 1-3, 4(77-86), 5(95-114), 6-8 (up-topage 164)
• TOE: Chaps. 1 & 2
• Seeds
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
116
Big Bang, Black
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ASTR/PHYS 289
Dr. David Toback
Lectures 19 & 20
Big Bang, Black
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Early Times & Fate of the Universe Topic 1:
Possibilities
117
Unit 6
Going back in time and going
forward in time
Before the first millionth of
a second
and the
Fate of the Universe
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
118
Overview of Unit 5
The things that determine the
Fate of the Universe are the
dominant effects in the VERY
early Universe
Thus, to understand either
requires learning about both
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
119
Outline of Section 5
1.Possible Fates of the Universe
Today
2.Flatness
3.The Case for Dark Matter
4.Particle Physics and Dark
Matter
• The Standard Model and
Supersymmetry
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
120
The Question of the Day
What type of
Universe do we
live in?
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
121
Size scale of the Universe
Draw This Out
Big Bang, Black
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Density less than the critical density
 universe will expand forever
Density more than the
critical density  Universe
will collapse again
Early Times & Fate of the Universe
Topic 1: Possibilities
122
Other Names
Also have other names for these
1. Closed Universe (collapses)
2. Open Universe (stays open
forever)
3. Critical Universe (has the
critical density to just barely
stay open)
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
123
Possibility 1: Closed
The Universe expands, but
eventually collapses back onto
itself
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
124
Possibility 2: Open
Gravity can’t overcome the speed
The Universe Expands forever
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
125
Possibility 3: Critical
The option right in-between the
other two
Call this the Critical Density
The Universe expands and slowly
asymptotes to zero speed
Big Bang, Black
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Topic 1: Possibilities
126
A Simulation
http://bigbang.physics.tamu.edu/Figures/StolenAnimations/cannonball_mass_vs_orbit.swf
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Early Times & Fate of the Universe
Topic 1: Possibilities
127
In class Quiz
What is
happening
in this
region?
Big Bang, Black
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{
Early Times & Fate of the Universe
Topic 1: Possibilities
128
For Next Time
• Evidence we are in a
critical Universe
• After that:
–Other stuff out there?
–Inflation…
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
129
Size scale of the Universe
Draw This Out
Big Bang, Black
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r < rc  universe
will expand forever
r > rc  Universe
will collapse back
Early Times & Fate of the Universe
Topic 1: Possibilities
130
Outline of Section 5
1. Possible Fates of the Universe
2. Flatness
3. The Case for Dark Matter
4. Particle Physics and Dark Matter
• The Standard Model and
Supersymmetry
5. Inflation
6. Dark Energy and the Accelerating
Universe
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
131
TFTM 2 still continued…
• Figure 4 on open vs. closed
universes…
• Later parts of this chapter are
pretty out of date unfortunately
(need to really know what the
answers are)
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Early Times & Fate of the Universe
Topic 1: Possibilities
132
SHU 12
• Some random notes on (p 236) on
why we can’t just look further and
further out into the universe to see
what happened.
• “Theory tells us that at extremely
hot temperatures everything has to
be opaque; we will not be able to
distinguish shape and structure. It
is rather as if everything is hidden
within an intense hot fog
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Topic 1: Possibilities
133
• So, even if we can find ways to build
more and more powerful telescopes,
capable of seeing even deeper into space
than the quasars, we already know that
we will not be able to see right back
into the time of the big bang….
• As we journey back in time, we will hit
this fog of intense heat some 300,000
years before we hit the big bang.)
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
134
• Note: No THING can travel
faster than the speed of light
• However: Space can expand
faster than the speed of light…
This is a consequence of General
Relativity
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Early Times & Fate of the Universe
Topic 1: Possibilities
135
• Some text
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
136
BHOT 7 cont…
• However, there is lots of “dark
matter” that we cannot see
direction but which we know
must be there because of its
influence of its gravitation
attraction on the orbits of stars
in the galaxies.
• More on this later…
Big Bang, Black
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Topic 1: Possibilities
137
TOE 2
• “A static universe should start
contracting under the influence of
gravity
• But suppose that, instead of being
static, the universe was expanding
• If it was expanding fairly slowly,
the force of gravity would cause it
to eventually stop expanding and
then start contracting
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
138
BHOT 7 cont…
• “A static universe is unstable, for there is no
comparable repulsive force to balance the
gravitational pull that all the stars and
galaxies exert on each other
• Therefore even if at sometime the universe
had been static, it wouldn’t have remained
static because the mutual gravitational
attraction of all the stars and galaxies would
soon have started it contracting
• In fact, even if the universe was expanding
fairly slowly, the force of gravity would cause
it to eventually stop expanding, and it would
start to contract
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
139
TFTM 2 cont…
• Friedman models? Infinite
universe or closed universe that
will eventually collapse? Critical
point in between the two?
Big Bang, Black
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Topic 1: Possibilities
140
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Early Times & Fate of the Universe
Topic 1: Possibilities
141
Deceleration of The Universe
• Expansion of the universe should be
slowed down by mutual gravitational
attraction of the galaxies
• Fate of the universe depends on the
matter density in the universe
• Define “critical density”, rc, which
is just enough to slow the cosmic
expansion to a halt at infinity
Big Bang, Black
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Topic 1: Possibilities
142
Note: Universe is not infinite in
space, but there is no
boundary: Gravity is so strong
that space is bent around onto
itself (kind of like the surface
of the earth)
Big Bang, Black
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Topic 1: Possibilities
143
Big Bang, Black
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Topic 1: Possibilities
144
• Learned a lot lately
• TOE 2, BHOT 7 dark matter,
dark energy, WMAP and
flatness…
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
145
Evidence of Flatness
Look at the full
Temperature
Map
sky in a single map
Stretch out a
sphere onto a flat Incredibly Uniform!
page
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
146
Perfectly Flat?
• Subtract off the same amount
everywhere
• What are we left with?
The overall temperature is
2.728 degrees Kelvin
The variation is very small
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
147
Hotter and Colder?
Colder here?
Big Bang, Black
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Hotter here?
Early Times & Fate of the Universe
Topic 1: Possibilities
148
What if we’re moving?
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
149
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
rotating around
the Milky Way at
Moving in this direction
250 km/sec
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
150
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…
Early Times & Fate of the Universe
Big
Bang, Black
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Topic 1: Possibilities
151
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
152
Evidence of Flatness?
Measure the temperature of the photons
in the Universe today to be incredibly
uniform
Gives us
confidence that
our story of
the Big Bang
and the
Evolution of
the Universe is
correct
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
153
Analysis of the Cosmic Background
Fluctuations
Analyze
frequency of
occurrence of
fluctuations on a
particular angular
scale
Universe has a
flat geometry
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
154
• First time 1-20
• Second time: 1-
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
155
• The reading for this is SHU 6
and BHOT 11
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
156
Reminder
• Universe is not infinite in space,
but there is no boundary
• Gravity is so strong that space
is bent around onto itself
– Kind of like the surface of the
earth
Big Bang, Black
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Early Times & Fate of the Universe
Topic 1: Possibilities
157
The Cosmic Background Radiation
The Famous COBE satellite map of the allsky structure of the Cosmic Background
Radiation
Big Bang, Black
Holes, No Math
Early Times & Fate of the Universe
Topic 1: Possibilities
158
The Cosmic Background Radiation
The
famous
new results
from the
recent
WMAP
satellite
experiment
Clear variation
Consistent with the General Relativity models of galaxy
formation and Quantum Fluctuations
Big Bang, Black
Holes, No Math
Early Times & Fate of the Universe
Topic 1: Possibilities
159
Subtract Further
Since we understand the Doppler
effect we can subtract if off
See what’s left…
Big Bang, Black
Holes, No Math
Early Times & Fate of the Universe
Topic 1: Possibilities
160
Shape and Geometry of the Universe
Closed surface
(positive curvature)
Big Bang, Black
Holes, No Math
Flat surface
(zero curvature)
Open surface
(negative curvature)
Early Times & Fate of the Universe
Topic 1: Possibilities
161
• Talk about the different types
of Universes and the curvature
• How would we tell?
Big Bang, Black
Holes, No Math
Early Times & Fate of the Universe
Topic 1: Possibilities
162
• Should we talk
about Curvature?
• Evidence that the
Universe is flat
and that this
implies we’re
missing some of
the
matter/density?
Big Bang, Black
Holes, No Math
Early Times & Fate of the Universe
Topic 1: Possibilities
163
• Learned a lot lately
• TOE 2, BHOT 7 dark matter,
dark energy, WMAP and
flatness…
Big Bang, Black
Holes, No Math
Early Times & Fate of the Universe
Topic 1: Possibilities
164
TFTM 2 still continued…
• Figure 4 on open vs. closed
universes…
• Later parts of this chapter are
pretty out of date unfortunately
(need to really know what the
answers are)
Big Bang, Black
Holes, No Math
Early Times & Fate of the Universe
Topic 1: Possibilities
165
SHU 12
• Some random notes on (p 236) on
why we can’t just look further and
further out into the universe to see
what happened.
• “Theory tells us that at extremely
hot temperatures everything has to
be opaque; we will not be able to
distinguish shape and structure. It
is rather as if everything is hidden
within an intense hot fog
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• So, even if we can find ways to build
more and more powerful telescopes,
capable of seeing even deeper into space
than the quasars, we already know that
we will not be able to see right back
into the time of the big bang….
• As we journey back in time, we will hit
this fog of intense heat some 300,000
years before we hit the big bang.)
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• Some text
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TOE 2
• “A static universe should start
contracting under the influence of
gravity
• But suppose that, instead of being
static, the universe was expanding
• If it was expanding fairly slowly,
the force of gravity would cause it
to eventually stop expanding and
then start contracting
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BHOT 7 cont…
• “A static universe is unstable, for there is no
comparable repulsive force to balance the
gravitational pull that all the stars and
galaxies exert on each other
• Therefore even if at sometime the universe
had been static, it wouldn’t have remained
static because the mutual gravitational
attraction of all the stars and galaxies would
soon have started it contracting
• In fact, even if the universe was expanding
fairly slowly, the force of gravity would cause
it to eventually stop expanding, and it would
start to contract
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TFTM 2 cont…
• Friedman models? Infinite
universe or closed universe that
will eventually collapse? Critical
point in between the two?
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Deceleration of The Universe
• Expansion of the universe should be
slowed down by mutual gravitational
attraction of the galaxies
• Fate of the universe depends on the
matter density in the universe
• Define “critical density”, rc, which
is just enough to slow the cosmic
expansion to a halt at infinity
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Deceleration of the Universe
• Expansion of the universe should be slowed
down by mutual gravitational attraction of the
galaxies.
• Fate of the universe depends on the matter
density in the universe.
• Define “critical density”, rc, which is just
enough to slow the cosmic expansion to a halt
at infinity.
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st
21
Century Cosmology
The solution: Inflation!
• Inflation: period of
sudden expansion
during the very
early evolution of
the universe
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• Triggered by the
sudden energy
release from the
decoupling of the
strong and
electroweak forces
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Topic 1: Possibilities
Cosmology and General Relativity
According to the theory of general
relativity, gravity is caused by
the curvature of space-time.
The effects of gravity on the largest
cosmological scales should be related to the
curvature of space-time!
The curvature of space-time, in turn, is
determined by the distribution of mass and
energy in the universe.
Space-time tells matter how to move;
matter tells space-time how to curve.
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