1. Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr
Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lectures 8, 9 & 10

2. Prep For Today (is now due) – L9
Reading:
(BBBHNM Unit 2)
Pre-Lecture Reading Questions
eCampus quizzes (all 6)
Unit 1 Revision (if needed): Stage 2
Let us know if you were misgraded on the original
Unit 2 Revision (if desired): Stage 1
Due date move to Monday. Let us know if you were misgraded
End-of-Chapter Quizzes
Chapter 5, parts a & b
Paper 1:
Not yet assigned

3. Prep For Today (is now due) – L10
Reading:
(BBBHNM Unit 2)
Pre-Lecture Reading Questions
eCampus quizzes (all 6)
Unit 1 Revision (if needed):
Let us know if you were misgraded on the original
Unit 2 Revision (if desired): Stage 1
End-of-Chapter Quizzes
Chapter 5, parts a & b
Paper 1:
Not yet assigned

4. Heads Up: Paper 1 What is the evidence for Dark Matter?
This will be the topic of Paper 1
In order to understand the evidence, we next talk about gravity and Dark Matter
Will be due 1 week after we finish Chapter 6

5. Papers in CPR/Schedule
Schedule is Like PLRQ since it is in CPR:
Each Paper has 4 (or 6) Steps:
Mentioned after we start the chapter (just did that)
Assigned after we finish the chapter
Submit text 1 week later (Stage 1)
Calibrations/Reviews/Self-Assessment due the week after that (Stage 2)
Revision (optional): Stage 1 due one week later
If you did a Stage 1, Calibrations/Reviews/Self-Assessment due one week after that

6. Style of the Paper
Explain it to someone who isn’t taking the class (no jargon)
~600 words (This is the equivalent of both side of a sheet of paper, double spaced)
No citations! Use your own words
Text should be professional. You are “trusted guide” not a “buddy” or “comedian”

7. Paper Format Must follow expected Format Usually 5 paragraphs. Needs:
Introduction paragraph
1 paragraph per piece of evidence (3 total?)
Conclusion paragraph that ties it together

8. Help Available for Stage I
Submit a draft for feedback from the TA
Submit on eCampus in “Rough Drafts (Optional)”
Drafts due Sunday at midnight
If you submit late, we can try to give feedback but we can’t guarantee it
We also recommend going to the writing center

9. Biggest reason people don’t do well
Read ALL the instructions on CPR
See the FAQ on papers
Don’t forget to submit to turnitin.com
We are NOT giving you the Rubrics for the papers, but lots of hints about what the Rubric questions will contain are in the Writing Prompt and Goals sections

10. Best Guess Schedule Paper 1: Due after we finish Ch 6, Feb 25 Paper 2:
Due after we finish Ch 8, Mar 2?
Paper 3:
Due after we finish Ch 12, Mar 23?
Paper 4:
Due after we finish Ch 17, April 8?

11. For People in the Honors Section
Stage 0 (not in CPR): Due Feb 25th
For details see

12. Outline for Unit 2: Physics We Need
Topics
Light and Doppler Shifts  Done
Gravity, General Relativity and Dark Matter Today
Atomic Physics and Quantum Mechanics  After that
Nuclear Physics and Chemistry
Temperature and Thermal Equilibrium

13. Why Gravity Next?
By looking at photons/light we can learn about things here on Earth as well as about inner/outer space
What else do we need to describe/understand the Universe? Quantum Mechanics and Gravity
To understand the answer to these questions we need to learn more

14. The Two Great Theories
General Relativity: (Gravity) Predictions about the very large, from sizes of a few meters to the size of the universe (1024 miles across)
Quantum Mechanics: Predictions about the very small (atoms, particles,<10-10 m)
Chapter 6
Chapter 7

15. Overview of Gravity for the Course
What’s so important about Gravity?
Newton’s Gravity
Einstein’s Gravity
Curved Space-Time, and evidence for it with Dark Matter

16. Gravity: Why do we care? Gravity: The great attraction in the Universe
Gravity is the theory that predicts the attraction and the motion of BIG things over large distances:
Planets
Suns
Galaxies
How Galaxies form etc.

17. Newton and Gravity Physics 201 or 218
Everything moves in a straight line unless acted upon by a force
Gravity is a force
Every object in the universe attracts every other object in the universe
The further the distance between the objects, the smaller the attraction
The bigger the mass, the bigger the attraction
Light is massless  not affected by gravity
Physics 201
or 218

18. Large Number of Scales Kinda amazing!
Gravity covers the attraction between
An apple near the Earth
The Earth and the Moon
The Earth and the Sun
The Sun and our galaxy
Our galaxy and the universe
Every particle in the universe and an apple
The Earth and you
Bevo and Reveille

19. Gravity continued…
The force of Gravity makes the Moon “fall” towards the Earth
 Call this an orbit
Does a great job of explaining how the planets move around the Sun
Without gravity, the Moon would fly off into space and ignore the Earth completely

20. What’s next?
Tell you the different, and surprising, way that Einstein describes space, time and gravity Then tell why his description of why the Earth goes around the Sun is better than Newton’s

21. 2nd year Grad School Course
Einstein in the 1910’s
In the early 1910’s Einstein was thinking about some recent experimental results that didn’t make any sense to him using Newton’s theories
Decided we need new ways of thinking about space, time and Gravity
Einstein says that Newton’s Laws aren’t really quite right…
Einstein’s theory is known as the “General Theory of Relativity”
2nd year Grad School Course

22. Light *ALWAYS* moves at the speed of light to all observers
Observational Fact
Light *ALWAYS* moves at the speed of light to all observers
So what?

23. What happens if I’m driving a car moving at half the speed of light and I turn the headlights on?

24. Two observers get different answers
The light is one foot ahead of that car!
The light is two feet ahead of me!

25. What happens if I’m driving a car moving at half the speed of light and I turn the headlights on?
Einstein says “it’s relative”, both observers are correct Space and Time are more related than we thought

26. Start with Space-Time Can’t think of Space and Time as separate
Space (measured with a ruler)
Time (measured with a clock)
 Single combined entity which we call four dimensional space-time
If the four dimensions are related, unexpected things that we’re not used to can happen

27. Need to talk about what we mean by Curved Space-Time
Other Weirdness
Space and time are not only more related than we thought, Space can Curve
Need to talk about what we mean by Curved Space-Time

28. We’ll start by using the strange “new” words of General Relativity in an example about why we care, and THEN explain them a bit more Space-Time and Gravity

29. This is a VERY different way of thinking about things…
Newton vs. Einstein
Newton: The Earth moves around the Sun because of “the force of gravity” is pulling it
Einstein: There is no “force” of Gravity, the Earth moves in a “straight line” around the Sun in the curved space-time created by the Sun
This is a VERY different way of thinking about things…

30. 1st floor of the Mitchell Physics building (MPHY)
Curved Space?
An analogy is to think of curved space-time as looking like one of those gravity wells you’ve seen downstairs
1st floor of the Mitchell Physics building (MPHY)

31. Moving in Curved Space: Analogy
Let’s say my friend and I are at the equator and we both start working due North
Exactly parallel to each other
We will notice that we “mysteriously” are getting closer to each other, and will eventually bump into each other
Is there a Force drawing us together? No… moving in curved space time LOOKS like a force
The rules of geometry are different in curved space

32. Another Weird Thing: Mass Curves Space-Time
Think of each of the heavy things in the universe (stars, planets etc.) like a ball in the middle of a taut rubber sheet that represents space-time
The weight of the ball will make it sink into the rubber sheet, creating a cone shaped dent around it

33. The heavier the ball the bigger the dent in space-time!
Mass Curves Space
The heavier the ball the bigger the dent in space-time!

34. Mass in curved space-time
A mass moves in a “straight line” in curved space-time
In this example, this straight line in curved space makes the path of the small ball look like something is pushing it toward the big ball in 3-dimensions

35. The Earth and the Sun
Newton: The Earth moves around the Sun because of “the force of gravity” is pulling it
Einstein: There is no force, the Earth moves in a straight line in four dimensions, but the curved space around the Sun makes it go in an orbit in the three space dimensions

36. The way the Planets go Around the Sun in General Relativity

37. Ok…
Both Newton and Einstein correctly predict how the planets go around the Sun
Actually mostly their predictions for the locations of the planets at any given time are almost identical
How do we decide if one is right and one is wrong?
Do an experiment!!!

38. When do General Relativity and Newton predict different things?
Ok… One equation, but I’m guessing you’ve heard this one
E=MC2
Ok… what is this equation saying? Energy and mass may not be the same, but in Einstein’s theory they are equivalent

39. It has energy, but no mass
So what?
What about light?
It has energy, but no mass
To Einstein, its mass doesn’t matter, it is a particle that moves in curved space-time

40. What happens to light as it goes past the Sun?
Path
doesn’t curve
Path
does curve
Newton’s theory: Only things with “real” mass “feel” the force of gravity
General Relativity: Objects move according to the curve of space-time, regardless of whether they have mass or not

41. Do an Experiment 1st Experiment: Can see the star directly
Looks like its over here!
2nd Experiment: Sun in the way
If Einstein is right, the Sun curves the path of the starlight
If Newton is right, we won’t see the star
Question: Where does the star appear when you do the experiment?
Gross exaggeration of sizes

42. The Great Experiment of 1915
Look at a star’s position “behind” the sun as it “passes” in between us and the star during an eclipse to block the glare of the sunlight

43. Another View

44. Evidence and More Evidence
The results exactly agreed with Einstein’s predictions
Contradict the predictions of Newton
Over time, even more compelling evidence has come in in favor of General Relativity  observations of Dark Matter in galaxies
Next give some of the evidence for dark matter and that the story hangs together

45. Evidence galaxies contain Dark Matter
Described the Dark Matter in the Universe and in galaxies in Chapter 2
In order to better understand dark matter in galaxies, its useful to show some evidence that there IS Dark Matter in galaxies
Start by considering the case that there IS no Dark Matter in galaxies

46. How stars move in galaxies
Laws of gravity accurately predict the orbits of planets and stars as they move around the solar system and galaxy
The brightest region of both places is the center  lots of mass there
For the solar system, the data agree perfectly, but for the outer part of galaxies it should look like stars in orbit around a massive center
Problem: This isn’t what the data shows

47. The Data

48. Does this work for Stars?
Watch how fast a star rotates around the center of the galaxy…
Simulation without
Dark Matter
Simulation with lots of
Dark Matter particles in the galaxy
Data looks like this

49. Data well explained by lots of “Dark Matter” we can’t see This is where it gets its name In some sense, the name is a statement of almost all we know about it (it doesn’t interact with light, and it has mass)

50. Maybe there isn’t dark matter and General Relativity is wrong?
Another Experiment
Maybe there isn’t dark matter and General Relativity is wrong?
Look at the gravitational impact on light that travels through the Universe, through a galaxy, and towards us

51. Einstein Ring’s?

52. Another view

53. Einstein Ring The “near” galaxy
The light from the “far” galaxy spread out into a ring
Amount of lensing explained by extra mass of dark matter

54. Winner: General Relativity
Many observations indicate that General Relativity correctly describes the motion of light, galaxies and stars in the Universe we live in  space and time are related
Space can curve, stretch, change etc.
Curved space-time will be very important in later chapters when we talk about the expansion of the Universe
Dark matter is an important part of the evolution of our universe

55. Paper 1 Abbreviated description: What is the evidence for Dark Matter?
More detail on CPR, you REALLY need to read ALL the instructions
Explain it to someone who isn’t taking the class (no jargon)
Follow the required Format:
Introduction paragraph
~1 paragraph per piece of evidence
Conclusion paragraph that ties it together
Help:
Example of good paper
The first 9 Rubric questions

56. Outline for Unit 2: Physics We Need
Topics
Light and Doppler Shifts Done
Gravity, General Relativity, and Dark Matter Done
Atomic Physics and Quantum Mechanics  Next
Nuclear Physics and Chemistry
Temperature and Thermal Equilibrium

57. Prep For Next Time – L8 Reading: (BBBHNM Unit 2)
Pre-Lecture Reading Questions
eCampus quizzes (all 6)
Unit 1 Revision (if needed): Stage 2
Let us know if you were misgraded
Unit 2 Revision (if desired): Stage 1
End-of-Chapter Quizzes
If we finished Chapter 6 then End-of-Chapter Quiz 6 (else, just through Chapter 5, parts a & b)
Paper 1:
If we finished Chapter 6: Stage 1 due Monday before class
Can submit a draft for feedback on eCampus if you like
MUST submit to turnitin on eCampus

58. Prep For Next Time – L9 Reading: (BBBHNM Unit 2)
Pre-Lecture Reading Questions
eCampus quizzes (all 6)
Unit 1 Revision: Let us know if you were misgraded
Unit 2 Revision (if desired): Stage 1
Let us know if you were misgraded
End-of-Chapter Quizzes
If we finished Chapter 6 then End-of-Chapter Quiz 6 (else, just through Chapter 5, parts a & b)
Paper 1:
If we finished Chapter 6: Stage 1 due Wednesday before class
Can submit a draft for feedback on eCampus if you like by Sunday night
MUST submit to turnitin on eCampus

59. End of Lecture

60. Clicker Quiz Which of the following travels the fastest? Radio waves
Gamma rays
Red light
Blue light
They all move at the same speed

61. Clicker Quiz
We observe two objects in space. From other studies, we can tell that object X is emitting infrared light and the object Y is emitting Ultraviolet light. We observe the color of the light object X to be Red and the color of Object Y to be blue.
Which statement is true?
X and Y are moving towards us
X and Y are moving away from us
X is moving towards us and Y is moving away from us
X is moving away from us and Y is moving towards us

62. Clicker Question
What would happen to the Einstein ring around a galaxy who's Dark Matter suddenly wasn't there?
Nothing
It would get smaller
It would get bigger
It would disappear
None of the above

63. Clicker Question
What would happen if you were shot by a gun that fires "dark matter” bullets which have the same size and mass as a regular bullet?
Your molecules would significantly spread out from an expansion of space-time
A black hole would form inside you
Objects behind you would be gravitationally lensed
Your body would barely notice
You would die like you would if you got shot with any kind of bullet

64. Clicker Question Why is dark matter "dark“?
Because it is closely linked to dark energy
Because it has no mass
Because it is made of black holes
Because it doesn’t interact with light

65. Clicker Question As far as we know, Dark Matter exists:
Everywhere in the universe
Only near black holes
Mostly in or around galaxies
It doesn't exist
We don't know where it exists

66. Clicker Question
A man shoots a red photon straight up into the air next to a very tall building. The photon rises in the air. Which statements are true:
The photon slows down as it rises, the same way a rock would
The photon loses energy, the same way a rock would
The photon gets blue-shifted

67. Clicker Question
Instead of throwing a rock into the air, a man shoots a red photon straight up into the air next to a very tall building. The following question are about the photon when it reaches the top of the building. Which of the following statements are true
Question 1: Speed
The speed of the photon stays the same
The speed of the photon slows down like a rock would
Question 2: Energy
The energy of the photon stays the same
The energy of the photon gets lower (like the kinetic energy would for a rock)
The energy of the photon gets larger (since it is getting closer to outer space)
Question 3: Color
The color of the photon stays the same
The color of the photon is red-shifted (gets a longer wavelength)
The color of the photon is blue-shifted (gets a shorter wavelength)

68. Prep For Next Time – L8 Reading: None Pre-Lecture Reading Questions
Let me know if you think you were misgraded
Unit 1 Revision: Grades will be posted in eCampus soon, instructions to follow if you didn’t pass
Unit 2 Revision (if desired): Stage 1 due in CPR Monday before class
End-of-Chapter Quizzes
If we finished Chapter 6 then End-of-Chapter Quiz 6 (else, just through Chapter 5)

69. Prep For Next Time – L9 Reading: (BBBHNM Unit 2)
Pre-Lecture Reading Questions:
Let us know if you have been misgraded
Unit 1 Revision: New grades posted soon.
Unit 2 Revision (if desired): Stage 2
End-of-Chapter Quizzes:
If we finished Chapter 6 then End-of-Chapter Quiz 6 (else, just through Chapter 5)
Paper 1:
Stage 1 due Monday before class
Can submit a draft for feedback on eCampus if you like
MUST submit to turnitin on eCampus

70. PLRQ 1 Revision
We still have a number of people who haven’t passed all the parts yet
I opened Stage 2 to let people finish it, thus the updated grades have not been posted on eCampus
When they are done, I will send an with new instructions – We will have a special way for student who need a third try

71. Back to Our Example Gravity well analogy:
In Relativity: It’s not that there is something “pulling" towards the center, instead space is curved and the penny is just moving in a straight line in curved space

72. Starting to think about “Curved Space-Time”
Analogy in 3 dimensions
General Relativity talks about 4-dimensional space-time
Our eyes can only see in 3 space dimensions
To us something moving in a “straight line” in 4-dimensional curved space time “looks” like its moving in a curved path in the 3-dimensional space we’re used to

73. Prep For Next Time – L5
Note: May change depending on how far we get in lecture
Reading:
BBBHNM: All reading through Chapter 9
Reading Questions:
All reading questions through 9
eLearning Quizzes
If we finished Chapter 6 then end-of-chapter quiz 6 (else just up to Chapter 5)
Paper 1
Revisions if needed

74. Prep For Next Time – L9 Reading: BBBHNM: Chapter 7 (already assigned)
Pre-Lecture Reading Questions:
Chapter 7 (already assigned)
End-of-Chapter Quizzes:
Did not finished Chapter 6, so just Chapter 5 (already due)
Paper:
Paper 0: Submit to CPR and turnitin on eCampus by Friday
Calibrations after that
Will assign Paper 1 next time since we will finish Chapter 6

75. Prep For Next Time – L9
Note: May change depending on how far we get in lecture
Reading:
BBBHNM: Chapter 7 (already assigned)
Pre-Lecture Reading Questions:
Chapter 7 (already assigned)
End-of-Chapter Quizzes:
If we finished Chapter 6, then Chapter 6. If not, just Chapter 5 (already due)
Paper:
Needed to be submitted to CPR and turnitin on eCampus
Be working on Calibrations.
Due Wednesday
Paper 1 coming up, will be due one week after we finish Chapter 6.

76. Prep For Next Time – L10
Note: May change depending on how far we get in lecture
Reading:
BBBHNM: Chapter 7 (already due)
Pre-Lecture Reading Questions:
Chapter 7 (already due)
End-of-Chapter Quizzes:
If we finished Chapter 6, then Chapter 6. If not, just Chapter 5 (already due)
Papers:
Paper 0 due to CPR and turnitin on eCampus on Friday
Be working on Calibrations
If we finished Chapter 6, Paper 1 will be due next Wednesday before class

77. Was Due For Today– L8 Reading BBBHNM: None
Pre-Lecture Reading Questions:
None
End-of-Chapter Quizzes
Chapter 5
Paper Stuff
Paper 0 in CPR and turnitin.com before class

78. Was Due For Today– L9 Reading BBBHNM: Chapter 7
Pre-Lecture Reading Questions:
Chapter 7
End-of-Chapter Quizzes
Chapter 5 was already due
Paper Stuff
Will talk about this today

79. Was Due For Today– L10 Reading BBBHNM: Chapter 7 (already due)
Pre-Lecture Reading Questions:
Chapter 7 (already due)
End-of-Chapter Quizzes
Chapter 5 parts A&B (already due)
Paper Stuff
Working on Paper 0, due Friday

80. Paper 0, Questions 1-5
Does the paper make it easy to understand what question is being answered, what the answer is, and how it will be answered? If anyone of those are missing, or if you can't follow the argument, then choose No. If the argument is clear, but not said very well (or is wordy), then you should still give a Yes. If the paper is clear to you, but would not be clear to someone who hasn’t taken the course choose No. Being easy to read isn't a good enough reason to give a Yes. Having a sentence or two that are hard to understand (or poorly written) within a basically clear paper is fine, and can still deserve a Yes if it is otherwise ok.
Are the pieces of evidence clearly and correctly enumerated in the opening paragraph? This includes the electrons going around atoms, the Moon orbiting the Earth, and planets orbiting the Sun.
Does the structure of the paper follow the instructions? Specifically: Is there an introduction paragraph, separate paragraphs discussing evidence, and a conclusion paragraph? If any are missing, choose No. Does the paper directly address the question and make the argument to answer it? If the paper addresses the question and makes an argument (right or wrong) to answer it, choose Yes (we will address the wrongness in a later question). Do not choose No due to a poorly written or confusing introduction. The paper does not need to have only three paragraphs, and the pieces of evidence can be intertwined within them. Do not choose No due to missing evidence or more than three paragraphs. Do not choose No just because evidence is not constrained to these paragraphs. If the paper does not end with a conclusion paragraph, choose No. Do not choose No due to a poorly written or confusing conclusion.
Is the paper generally free of extraneous evidence? If there is any significant evidence that is off topic or an argument that has nothing to do with the topic, choose “No.” If there is significant evidence from outside class, choose No. Do not choose “No” due to evidence that is unnecessary if the evidence is relevant to the topic.
Does the paper only use language and words that can be understood by the average lay-person? If the author uses an acronym, like GR, for general relativity that is ok but only if the acronym is clearly defined. If they use an acronym that isn't defined, then select No. Similarly, just because you saw these words in a high-school science class does not mean they are understood by the average person. The average person on the street would know what an atom is, but not know what a spectral line is.

81. Paper 0, Questions 6-10
Does the essay use language formal enough to give to a statesman? If the paper uses jokes, slang or other informal language, choose No. Do not choose No due to poor grammar, spelling mistakes, incomplete sentences, or poor sentence structure (we will take off points in a different question for this). Do not choose No due to the use of an acronym, like USA, since it is common usage and not slang.
Is the essay generally free of instances of bad grammar, incomplete sentences or spelling mistakes? If there are more than two minor mistakes, choose No.
Does the paper make clear how and why the evidence presented relates to the argument? If the facts are mentioned but show no clear connection to the argument, then choose No. If the facts are not addressed throughout the paper, then choose No. If it states the data without saying why it is evidence then choose No.
Do the middle (evidence) paragraphs clearly tie into the overall structure?
Does the paper use the scientific method and evidence based decision making? It’s OK if the words “scientific method” and “evidence-based decision making” are not mentioned specifically.

82. Paper 0, Questions 11-15
Does the essay make it clear what the Scientific Method is and why it is important in this paper?
Does the essay clearly tie together the pieces of evidence using the scientific method in the conclusion?
Does this paper say that the Moon orbits the Earth?
Does the paper mention explicitly that the Earth is much more massive than the Moon, and that it is important to why the Moon orbits the Earth instead of the other way around? If it mentions that the Earth is more massive, and that this is what is important, then this is good enough. If it just says that it is more massive without saying why that is important in some way, then answer No. If it says "bigger" or "larger" (or that the Moon is "smaller") that is good enough.
Does the paper mention that the Earth or the planets orbit the Sun? Either is fine. If neither is mentioned, then give a No.

83. Paper 0, Questions 16-20
Does the paper mention explicitly that the Sun is much more massive than the things orbiting it, and that it is important to say why they orbit the Sun instead of the other way around? If it mentions that the Sun is more massive, and that this is what is important, then this is good enough. If it just says that it is more massive without saying why that is important in some way, then answer No. If it says "bigger" or "larger" (or that the planets are "smaller") that is good enough.
Does the paper mention that electrons orbit protons or that electrons orbit a nucleus? Either one is fine.
Does the paper mention explicitly that the proton (or nucleus) is much more massive than the electron orbiting it, and that it is important to why they orbit the proton (or nucleus) instead of the other way around? If it mentions that the proton or nucleus is more massive, and that this is what is important, then this is good enough. If it just says that it is more massive without saying why that is important in some way, then answer No. If it says "bigger" or "larger" (or that the electron is "smaller") that is good enough.
Does the essay spend an appropriate amount of time on each topic?
Does the conclusion paragraph tie together all the big picture issues discussed in the other paragraphs? If the conclusion does not summarize the evidence, then chose No. If the conclusion simply re-states the pieces of evidence, then choose No.

84. Clusters of galaxies can smear out the light from a single galaxy into a long “arc”

85. Our best Understanding
Oversimplified view of a spiral galaxy
In some ways, Dark Matter surrounds the 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 the pull of gravity

86. Lensing of Galaxies Prism
Dark Matter “Lenses” the galaxies behind them like a prism or a pair of bad eyeglasses
Evidence that the light coming to us is passing through lots of matter we can’t see directly

87. General Relativity and Light
The large mass of the Sun can bend the path of light
Result: The apparent position of a star “moved” as the light passed from outer space, past the Sun, and to us
Is here
“Looks” like its here
Light’s path in curved
space time

88. Looking at Light from the Universe
Galaxy
Light from a Galaxy
Another Galaxy
Hydrogen
Cloud
Looks like a Galaxy behind a cloud of heavy “stuff” that isn’t just stars and hydrogen
Looks like a Galaxy behind a cloud of hydrogen
Looks like a Galaxy

89. Prep for Today (Is now due) – L8
Reading:
BBBHNM 7
Reading questions:
Chapter 7
End-of-Chapter Quiz:
Chapters 5
Paper 1:
Phase II is due Friday at 5:45PM

90. Phase I and Phase II in CPR
Phase I: (Due 1 week after we finish Chapter 4)
Turn it into CRP (online)
Need to also submit a copy to the version of turnitin.com on eLearning
Phase II: (Due one week after Phase I)
Three-Part Calibrations/Reviewing
Calibrations, learning to use the Rubrics
Grade three other papers
Grade your own paper

91. Prep for Next Time – P7 Reading: BBBHNM 7 Recommended:
SHU: 6 and 7 (up-to page 153)
BHOT: 9 and 11 ( )
Reading questions
Two questions from Chapter 7 or the recommended reading
End-of-Chapter Quizzes
If we finished Chapter 6, quiz due before the next class (else just 5)
Paper 1
Phase II is due Friday at 5:45PM

92. Prep for Next Time – P8 Reading: None Reading questions
End-of-Chapter Quizzes
If we finished Chapter 6, quiz due before the next class (else just 5)
Paper 1
Phase II is due Friday at 5:45PM

93. Full set of Readings So Far
Required:
BBBHNM: Chap 1-7
Recommended:
BHOT: Chap. 1-6, 9 and 11 ( )
SHU: Chap. 1-3, 6 and 7 (up-to page 153)
TOE: Chap. 1

94. Overview of Physics We Need
Cosmology, the Big Bang and Black Holes are some of the most interesting things that can be understood
However, to UNDERSTAND them better, and the EVIDENCE for them, we need to learn some physics

95. The Good, the Bad and the Ugly
Both make lots of predictions that are observed in experiment
Example: What does Light do and how does it behave
Bad:
Don’t always make predictions that are inconsistent with each other, although wean’t yet test any of those predictions
Example: Different predictions for the center of a Black Hole

96. ???
Maybe just need to modify one or the other (or both?) and combine to make a “quantum theory of gravity”?
Could be, but been working on it for more than 60 years, no luck yet
Maybe both are wrong?
Either way, they are our best understanding at the moment  Lots of experiments are INCREDIBLY well described by them  Makes us think there is SOME truth in there somewhere…

97. Why do we need the world to be this complicated?
Data says that light always moves at the speed of light.
Einstein says that the laws of physics should be the same for all freely moving observers, no matter what their speed
So What?
Since nothing can move faster through space than light (it always moves at the speed of light) this has enormous implications for the way both space and time are related
Space (measured with a ruler)
Time (measured with a clock)

98. The Great Experiment of 1915
Look at a star’s position “behind” the sun as it “passes” in between us and the star
Result: The apparent position of a star is different when the sun is close to the path
In other words, we observe that the gravity of the sun “bent” the path of the “no mass” light object coming from the star
Light’s path in curved
space time

99. The heavier the ball the bigger the dent in space-time!
Mass Curves Space
The heavier the ball the bigger the dent in space-time!

100. Stars
Space-time is curved or “warped” a lot by stars

101. Interesting Aside
Interesting to note that if Newton’s laws were even slightly different, the orbits of the planets would not be circles or ellipses
Would spiral into the sun or escape completely…

102. Today’s Lecture Today we’ll talk about Gravity and General Relativity
If there are questions that you want answers to then you should write them down and we’ll get back to you
Only tell you the things about Gravity and General Relativity you need to know

103. How this “Looks” to us in the Real World
General Relativity talks about 4-dimensional space-time
Our eyes can only see in 3 dimensions
To us something moving in a “straight line” in 4-dimensional curved space time “looks” like its moving in a curved path in the 3-dimensional space we know and love

104. In-Class Writing Assignment
Write down, during the course of lecture
Two questions you want to know the answer to
If you ask them during lecture, you can still write them down

105. 2nd Issue for General Relativity
In General Relativity, bodies always follow a straight line in four dimensional space-time unless there is a force
Gravity is not a force
Compare to Newton: “Unless there is a force things move in a straight line in three dimensions; gravity provides a force”

106. In General Relativity, bodies always follow a straight line in four dimensional space-time unless there is a force
Why is this important?
Better yet,
Why do we care?

107. General Relativity says that what appears to be the force of gravity pulling a mass is actually a mass moving in straight line in curved space-time

108. This is a BIG statement
This is a VERY different way of thinking. Let’s spend some on this
In General Relativity, bodies always follow a straight line in four dimensional space-time unless there is a force
Gravity is not a force
Compare to Newton: “Unless there is a force things move in a straight line in three dimensions; gravity provides a force”

109. Einstein and General Relativity
Laws of physics should be the same for all freely moving observers, no matter what their speed
Changes our concept of time…
There is no absolute time!
Space is not separate from time, we need to combine them into 4 dimensional space-time
2nd year Grad School Course

110. General Relativity
Gravity is not a force like other forces, but rather the weird consequence that space-time is not flat
Space-time is curved or “warped” by the distribution of mass and energy in it

111. Outline
Overview for the next set of lectures
Physics We Need
De-mystifying the strange theories
Overview of Today’s lecture
Gravity and General Relativity

113. Today’s Lecture Today we’ll talk about Gravity and General Relativity
I wasn’t planning on going over EVERYTHING in BHOT because I don’t think we need it for our story
Can cover extra questions in recitation
Only tell you the things about Gravity and General Relativity you need to know

114. Next Few Lectures De-mystifying the strange theories For next time:
Reading: BHOT 4-6 (Gravity)
Lecture Prep: Create two multiple choice questions based on the reading
Next round of reading after that:
SHU: 3 (p55-69)
SHU: 6 and 7 (up-to page 153)
BHOT: 9 and 11 ( )

115. Section 2 The reading for the next 5 lectures: Today: Gravity
BHOT: Mostly 4 and 6
Next lecture
BHOT: 5 and SHU: 3 (first part, p55-69)
After that
SHU: 6 and 7 (to page 153)
BHOT: 9

118. Outline Definitely: Doppler shifts Spectral lines Newtonian gravity
Might need?
Quantum Mechanics
Curved space
Other stuff
Atomic model: Electrons that surround a nucleus
Nuclear model: A nucleus is protons and neutrons that are held together
What is the Milky Way?
Feynman diagrams here?
What is temperature?

120. Do we need to do atomic Physics and chemistry first (textbook?)?
Speed of light is really freaking large
Photons are particles, but also a wave… have a wavelength…

121. BHOT: 4: General Relativity vs. Quantum Mechanics
Gravity and Theory of the very big
Quantum Mechanics
Theory of the very small
Aren’t consistent with each other, but both are incredibly successful in their areas
Looking for a quantum theory of gravity
Jonathan: Pictures from BHOT chapts 1-4

124. BHOT 6 cont:
Time runs differently at different heights in a gravitational field. Need to talk about this? Its cool, but so what…