1. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 1 Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lectures 15

2. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 2 Was due Today – L15 Reading: –(Unit 3) Pre-Lecture Reading Questions: –Unit 3, Stage 2 End-of-Chapter Quizzes: –Chapter 9 Papers: –Paper 1 Revision, Stage 1 Due Wed after Spring Break, but Stage 2 will be Mon March 30 –Paper 2, Stage 1: Due before class on Wednesday (Text needs to be in turnitin on eCampus) Honors Paper: –Stage 1 due before Midnight tonight

3. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 3 Starting Unit 3 Finished Unit 2: Physics We Need 1.Light and Doppler Shifts 2.Gravity, General Relativity and Dark Matter 3.Atomic Physics and Quantum Mechanics 4.Nuclear Physics and Chemistry 5.Temperature and Thermal Equilibrium Starting Unit 3: Evidence for Big Bang 1.The Exploding Universe 2.Expanding Space-Time 3.Photons and Hydrogen in the Universe

4. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 4 Where we are going… First give three pieces of evidence for the Big Bang –Don’t worry… you don’t need to memorize them now –Will keep coming back to them over and over again –Will be in the lecture notes Then tell the story about how they all fit together Will be the topic of Paper 3

5. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 5 Overview: Evidence for the Big Bang 1.We observe all distant galaxies to be moving away from us –The further away the galaxy is the faster it is moving away from us –True no matter which direction we look 2.We observe low energy photons (microwaves) uniformly distributed in all directions which are consistent with a temperature of about 2.7 degrees above absolute zero (Kelvin) 3.The atoms in the Universe are basically Hydrogen and Helium and not much else

6. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 6 3 Lecture Outline 1.The Exploding Universe Today 2.Expanding Space-Time Next Lecture 3.Photons and Hydrogen in the Universe The Lecture After That

7. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 7 Today’s Outline Looking at Galaxies Light from distant galaxies is Red Shifted and appears the same in all directions The Exploding Universe A problem…

8. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 8 Galaxies before 1920’s Before the 20’s, when the telescopes became powerful enough, there was no convincing evidence that there was anything outside the Milky Way When Einstein first wrote about the Universe, he meant “The Milky Way”

9. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 9 Edwin Hubble In the 1920’s Hubble established that there are distant galaxies made of individual stars –VERY far away Now know that in the same way that Sun is just one star of many, the Milky Way is just one of about a 100 billion galaxies

10. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 10 What can we Learn from Galaxies? Measure some important things: How far away are they? How fast are they moving? What directions are they moving?

11. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 11 How do you measure the distance to a galaxy? Use a special Star called a “Cepheid Variable” We know how much light they emit –Like a 100 Watt Light bulb If we measure how much light we see, we can figure out how far away it is If we can find a Cepheid in a galaxy, then we can figure out how far away that galaxy is

12. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 12 What is Their Velocity? How fast are they moving? What direction are they moving? Use the Doppler shift and measure their spectral lines!

13. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 13 Observing a Galaxy Galaxy Emitting Light Not MovingMoving away from us

14. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 14 Put it all together Measure distance from how much light reaches us Measure speed from Doppler shift of Spectral lines

15. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Distances Andromeda (the closest galaxy to our own) is ~2 million light years away! –More than 10 times farther away than the furthest thing in our own galaxy We see galaxies over 10 billion light years away 15

16. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 16 Speeds A fast star can travel a few hundred kilometers per second! Put this in perspective  Big: Can travel 10 billion kilometers in a year  Small: That’s less than a 1000 th of the distance to the star nearest us

17. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 17 Is there a trend? Most of the galaxies are red shifted –Moving away from us More importantly: The further away they are the faster they are rushing away from us! Perhaps even more important: Looks the same in all directions! Individual Galaxies Call this simple relationship “Hubble’s Law”

18. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 18 Put this in Perspective They are traveling away from us really quickly –From New York to California in ~1 second Can’t see this effect in our galaxy –Furthest stars in our galaxy are ~10 5 light years away –Thousand times smaller size

19. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 19 So What? We live in a Universe where things are clearly moving! Galaxies are moving away from us very quickly Is something pushing them?

20. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Why are Things Flying Apart? The answer turns out to be complicated We’ll start with a hypothesis that turns out to be wrong but helps us understand Then we’ll go back and explain it more correctly 20

21. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 21 An Explosion? Georges Lemaitre (1927): The galaxies are not flying apart because something is “forcing” them apart, they are moving apart because they were part of an “explosion” a long time ago

22. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 22 Is the data consistent with the simplest picture of an exploding Universe?

23. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 23 A Simple Explosion

24. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 24 A Snapshot in Time Fast Stuff is far from the explosion Slow Stuff is close to the explosion

25. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 25 A (wrong) Hypothesis… Fast Stuff is far from the location of the explosion Slow Stuff is close to the location of the explosion Consistent with this data

26. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 26 A Beginning? If galaxies are rushing apart from us then at some point in the past they must have all have been closer together

27. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 27 Running Backward in Time

28. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 28 Bottom Line The data about the velocities of the galaxies provides evidence that we live in a Universe that exploded into existence a long time ago We now know it was about 14 billion years ago

29. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 29 The Story is Always more Complicated Let’s think about our data a little more carefully Say it again: Galaxies are moving away from us AND moving the same way in EVERY direction Simple explanation? We’re located at the center of the explosion and we’re not moving!

30. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 30 Consistent with what we observe! We’re at the CENTER and NOT MOVING: Red Shifted Light

31. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 31 If We’re at the Center Equal amounts of stuff on each side Consistent with what we observe! Fast Stuff Slow Stuff Medium Speed

32. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 32 Not what we observe! Another possibility: We’re at the center and MOVING

33. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 33 If We’re Not At The Center Lots of stuff on this side Not much stuff on this side Not what we observe! Fast Stuff Slow Stuff Medium Speed

34. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 34 ??? Do we REALLY believe we’re the center of the Universe AND that we’re not moving? Is there a better explanation?

35. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 35 For Next Time– L15 Reading: –(BBBHNM Unit 3) Pre-Lecture Reading Questions: –Let us know if you were misgraded End-of-Chapter Quizzes: –If we finished Chapter 10 then end-of-chapter quiz 10 (else just up to Chapter 9) Papers: –Paper 1 Revision, Stage 1 Due Wed after Spring Break, but Stage 2 will due Monday, March 30 –Paper 2, Stage 2: Due Wed March 25, before class Honors Paper: –Stage 1 due tonight before midnight

36. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Full set of Readings So Far Required: –BBBHNM: Chaps. 1-12 Recommended: –TFTM: Chaps. 1-3 –BHOT: Chaps. 1-7, 9 and 11 (117-122) –SHU: Chaps. 1-3, 4(77-86), 5(95-104), 6, 7 (up-to-page 153) –TOE: Chaps. 1 & 2 36

37. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 37

38. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 38 Clicker Question Which best describes the two galaxies below? a)Both are moving towards us, but the left one is moving faster than the one on the right b)Both are moving towards us, but the right one is moving faster than the one on the left c)Both are moving away from us, but the left one is moving faster than the one on the right d)Both are moving away from us, but the right one is moving faster than the one on the left

39. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Clicker Question Two stars in the Milky Way have the same temperature. Are they in thermal equilibrium with each other? a)Yes b)No 39

40. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Clicker Question True or False: Once a bunch of atoms are in thermal equilibrium, the energy of an individual atom doesn’t change a)True b)False 40

41. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Clicker Question True or False: If I have a bunch of electrons, positrons and photons in thermal equilibrium, we will never have another positron annihilate with an electron and raise the number of photons a)True b)False 41

42. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Clicker Question Why can electrons, positrons, and photons be in thermal equilibrium with each other, even if they are creating and annihilating one another? a)They can be the same temperature b)They are in thermal contact c)Can only become in thermal equilibrium when interactions cease d)A and B 42

43. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Clicker Question On a cold winter morning, which is a lower temperature, a metal sign pole or a wooden bench? a)The metal pole b)The wooden bench c)They are the same temperature d)They are at absolute zero 43

44. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Clicker Question Let’s say you were the person observing the galaxies, but each other person in the room were a galaxy. Which person in the room is moving away from you most quickly? a)Back left b)Back right c)Front left d)Front right 44

45. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 45 Prep For Next Time – L7 Reading: –BBBHNM: All reading through Chapter 12 Reading Questions: –All reading questions through 12, due before class eLearning Quizzes: –Through Chapter 9, due before class Papers: –Paper 2 text feedback (if desired) due Monday March 11th for guaranteed feedback. –Due Tuesday March 19 th in CPR and turnitin.

46. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 46 For Next Time– L14 Reading: –(BBBHNM Unit 3) Pre-Lecture Reading Questions: –Let us know if you were misgraded –Unit 3, Stage 2 End-of-Chapter Quizzes: –If we finished Chapter 10 then end-of-chapter quiz 10 (else just up to Chapter 9) Papers: –Paper 1 Revision (if desired), Stage 1 due Monday before class (Text needs to be in turnitin on eCampus) –Paper 2, Stage 1 due before class Monday (Text needs to be in turnitin on eCampus) Honors Paper: –(Stage 0) –Stage 1 due Mon Oct 20 th

47. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 47 Was due Today– L16 Reading: –Chapter 10 Pre-Lecture Reading Questions: –Chapter 10 End of Chapter Quizzes: –Chapter 9 Papers: –Paper 0 Revision (if you didn’t pass the first time – See eCampus score, not CPR Score): Calibrations/Reviews due Monday before class –Paper 1: Scores are on CPR (won’t go on eCampus). If you want to do a revision, that will be due next Wednesday before class. –Paper 2: Text due today before class, Calibrations/Reviews due next Wednesday before class –Honors Paper: Stage 0 due Today

48. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 48 Prep For Next Time – L16 Note: May change depending on how far we get in lecture Reading: –BBBHNM: Chapters 11 and 12 Pre-Lecture Reading Questions: –Chapter 11 and 12 End of Chapter Quizzes: –Chapter 10 if we finished 10 today, if not just 9 (already assigned) Papers: –Paper 0 Revision (if you didn’t pass the first time – See eCampus score, not CPR Score): Calibrations/Reviews due Monday before class –Paper 1: Scores are on CPR (won’t go on eCampus). If you want to do a revision, that will be due next Wednesday before class. –Paper 2: Text due today before class, Calibrations/Reviews due next Wednesday before class –Honors Paper: Stage 0 due Today

49. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 49 Prep For Next Time – L7 Note: May change depending on how far we get in lecture Reading: –BBBHNM: All reading through Chapter 12 Reading Questions: –All reading questions through 12 eLearning Quizzes: –If we finished Chapter 10 then end-of-chapter quiz 10 (else just through Chapter 9) Papers: –Paper 2 text feedback (if desired) due Monday March 11th for guaranteed feedback. –Due Tuesday March 19 th in CPR and turnitin.

50. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 50 Was due Today – L8 Reading: –BBBHNM: All reading through Chapter 12 Reading Questions: –All reading questions through 12 eLearning Quizzes: –Chapter 9 Paper 2: –Due Tuesday March 19 th (tomorrow) in CPR and turnitin

51. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Tentative Due Dates – L8 Monday March 18 th –Paper 3 Assigned –Reading for Chap 11 and 12, EOC quizzes for 9 due Tuesday March 19 th –Paper 2 Text due in CPR and eLearning (1-day extension) Friday March 22 nd Want feedback on a Paper 2 draft? Due today in eLearning Monday March 25 th –Paper 2 Reviews due in CPR Wednesday March 27 th –Paper 3 text due in CPR and eLearning (2-day extension) Monday April 1 st –Paper 3 Reviews due in CPR 51

52. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 52 Prep for Next Time – P13 Reading: –BBBHNM 11 Reading questions: –Two questions on BBBHNM 11 End-of-Chapter Quizzes: –If we finished Chapter 10, end-of- chapter 10 (else just 9) Paper 2: –Text due Tuesday at 5:45PM –Calibrations/Reviews due Monday March 19

53. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 53 Prep for Today (Is due now) – L14 Reading: –BBBHNM 11 Reading questions: –Chapter 11 or the recommended reading End-of-Chapter Quizzes: –Chapter 9 Paper 2: –Text was due Yesterday at 5:45PM –Calibrations/Reviews due Monday March 19

54. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 54 Prep for Next Time – P14 Reading: –BBBHNM 11 Reading questions: –Two questions on BBBHNM 11 End-of-Chapter Quizzes: –If we finished Chapter 10, end-of- chapter 10 (else just 9) Paper 2: –Text was due Yesterday at 5:45PM –Calibrations/Reviews due Monday March 19

55. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Prep for Next Time – P14 55 Reading –BBBHNM 11 Reading questions –Chapter 11 End-of-Chapter Quizzes –If we finished Chapter 10 then end- of-chapter quiz 10 (else just 9) Paper Stuff: –Paper 1 Revision: CPR due Friday 6PM –Paper 2 Submission: Wed 4PM in CPR

56. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 56 Galaxies Not Moving? What if the galaxies were not moving in any way? What would happen? But, everything attracted by gravity! –All objects will eventually be drawn to each other –A stationary rock will just fall to the surface of the Earth This would require something to hold them in place

57. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 57 Thermal Equilibrium? What would we expect if our universe were in thermal equilibrium? –If we (as observers) are stationary: Half the stars will be moving away from us, half will be moving towards us, all roughly with the same speed –If we’re moving: Faster (higher temperature) on one side than the other

58. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 58 Rotating? Maybe the galaxies are rotating around some center of the Universe? Like the planets around the sun? Like the stars around the center of our galaxy? Is there something at the center that’s drawing them in?

59. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 59 Other options? Einstein’s Gravity (General Relativity) says that space-time can be getting smaller, but it can also be expanding –Things can be moving further apart, like a rock after it’s been throw up in the air –Observe either?

60. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Enough guessing… what does the data say? 60

61. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 61 So What? Looks like Thermal Equilibrium in that it appears to be the same in all directions Not faster on one side than the other Doesn’t look like thermal equilibrium in that we don’t observe half the stars moving away from us, half moving towards us! We live in a Universe where things are clearly moving! Is something pushing them apart?

62. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 62 What Else Can I Learn? If the expansion rate is 15 kilometers per second per million light years of separation, then dividing these we get that everything was at the same place about 20 billion years ago –The age of the Universe! Not quite right… things must have been slowing down due to gravity (the galaxies attract each other and slow each other down). Take into account how long the light has been traveling. –Better estimate: The age of the universe is ~13.5 billion years

63. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 63 What Else Can I Learn? Take into account the expansion rate and how much its being slowed down by gravity  get that everything was at the same place about 14 billion years ago –The age of the Universe! –Current best estimate is that the age of the universe is ~13.7 billion years

64. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 64 Corroborating Evidence? Carbon dating and other studies suggest that the Earth is about 5 billion years old Similar studies show that the Milky Way is about 13 billion years old –The story hangs together

65. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 65 The Opposition In 1915, when Einstein came up with General Relativity, we only knew about our own galaxy and that ISN’T big enough for these velocity effects to be noticeable –People thought the Universe was essentially not moving –Discovery of the rotation of the Milky Way was discovered in the 20s also SOMETHING must be keeping it that way  Cosmological constant (anti-gravity force) was built into the fabric of space-time More on this when we come to Dark Energy

66. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 66 For Next Time Finished: The Exploding Universe Next Time: Expanding Space-Time After That: Cosmic Background Radiation Reading for next time –BBBHNM: Chapter 11 Full reading so far: BBBHNM: Chaps. 1-11 TFTM: Chaps. 1-3 BHOT: Chaps. 1-7, 9 and 11 (117-122) SHU: Chaps. 1-3, 4(77-86), 5(95-104), 6, 7 (up-to- page 153) TOE: Chaps. 1 & 2 Lecture prep: Turn in two questions on Chapter 11 on eLearning before class

67. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 67 Another Random Fact In 1951 the Catholic church officially pronounced the idea of the Big Bang model to be in accordance with the Bible Liked the idea of an experimental verification of a moment of creation

68. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 68 History Belgian Jesuit priest (1927) working at the Vatican Observatory (Georges Lemaitre) History: The Vatican was interested in finding cosmological models consistent with the notion of creation in the bible: A beginning!

69. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 69 The Reading For Unit 3 Reading for the start of Unit 3 BBBHNM: Chapter 10 TFTM: 1-3 BHOT: 7 SHU: Rest of chapter 3, 4(77-86), 5(95-104) TOE: 2 Full reading so far: BBBHNM: Chaps. 1-10 TFTM: Chaps. 1-3 Prelude BHOT: Chaps. 1-7, 9 and 11 (117-122) SHU: Chaps. 1-3, 4(77-86), 5(95-104), 6, 7 (up-to- page 153) TOE: Chaps. 1 & 2

70. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Paper 1 Stuff Done with grades –Graded unfairly? Let us know! Passing score: –Text score: more than 21 points (70%) –Calibrations: more than 15 points –Reviews: more than 15 points –Overall score: more than 70 points Revision due date was today at noon –Updated assignment requirements and rubric –Do full CPR grading –Grading right after that  Due one week later 70

71. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math Paper 2 and Other Stuff Now open for submissions Extended due date: –Friday at noon CPR grading right after that  due one week later Unit 2 eLearning was due today, before class Need to start Unit 3 71

72. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 72 Get Velocity from Spectral Lines Expect Spectral lines at certain Wavelengths How much do they “shift” for each Galaxy?

73. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 73 The Doppler Effect and Light More Blue More Red

74. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 74 Writing Assignments 1.Short Assignment 1 is due before the beginning of Class Thurs Oct 15 th Any revisions will be due 1 week after it is returned 2.Short Assignment 2 is posted Currently Due Thursday Oct 27 th which is one week after we finish Chapter 12 3.Research Paper is posted Stage 0 due Thurs Oct 29th Stage 1 due Thurs Nov 5 th Final paper due the last day of class, Tuesday Dec 8 th Unit 2 eLearning stuff now due Need to start Unit 3 eLearning stuff

75. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 75 History, Part 1 Late 1700’s: Lots of visible stars out there, mostly in specific set of directions –The Milky Way 1750 Thomas Wright: Found more stars were seen clustered together when looking in one direction than in others First ideas of clustering of stars…

76. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 76 The Milky Way Could be explained if most of the visible stars were arranged in a single disk-like configuration –Now: Can see about 5000 stars with the naked eye (~0.0001% of the total number)

77. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 77 The 1920’s Started looking with more powerful telescopes “Hazy stuff” in the heavens –Dust clouds or “nebulae” Are these more clusters of stars?

78. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 78 Problem The visible stars are close to us (in a cosmic sense)! –Inferring what the universe is like from them would be asking what are people around the United States is like by just looking at the people in College Station

79. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 79 More on the Milky Way The Milky Way is a spiral galaxy about one hundred thousand light years across and slowly rotating The stars in the spiral arms orbit the center about every several hundred million years

80. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 80 The Necessity of a Big Bang If galaxies are moving away from each other with a speed proportional to distance, there must have been a beginning, when everything was concentrated in one single point: The Big Bang! ?

81. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 81 Olbers’s Paradox Why is the sky dark at night? If the universe is infinite, then every line of sight should end on the surface of a star at some point The night sky should be as bright as the surface of stars!

82. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 82 Solution to Olbers’s Paradox If the universe had a beginning, then we can only see light from galaxies that have had time to travel to us since the beginning of the universe The visible universe is finite!

83. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 83 The Reading For Unit 3

84. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 84

85. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 85 Some text

86. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 86

87. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 87 Expanding Universe Goes here on in next section on GR? Clearly there is an expansion –Lecture 1: Big Bang –GR: Space is expanding rather than we are expanding into an already expanding space

88. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 88 But everything expands away from everything else as well. Hmmm… Experimental evidence for this? How do we know the difference between us being at the center of the explosion and being in an expanding space?

89. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 89 TFTM: 1-3 BHOT: 7 SHU: 3 (69-77)-XX TOE: Does TOE 2 go here? Entered in: TFTM 1 - 3, BHOT 7, part of SHU 3.

90. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 90 If we not at the Center Different amounts of stuff on either side of us… Stuff that’s closeStuff that’s far away

91. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 91 Keep them here for now. Cosmic Background Radiation, Red Shift, Isotope Abundance as Evidence of age, (nucleosythesis, WMAP experiment, particle antiparticle asymmetry)

92. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 92 TFTM 1 cont… Basic particles… Electrons Positrons Photons Neutrinos Proton Neutrons Hydrogen Helium

93. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 93 This chapter marks a watershed in our study of astronomy. Since Chapter 1, our discussion has focused on learning to understand the universe. Our outward journey has discussed the appearance of the night sky, the birth and death of stars, and the interactions of the galaxies. Now we reach the limit of our journey in space and time, the origin and evolution of the universe as a whole. The ideas in this chapter are the biggest and the most difficult in all of science. Our imaginations can hardly grasp such ideas as the edge of the universe and the first instant of time. Perhaps it is fitting that the biggest questions are the most challenging. But this chapter is not an end to our story. Once we complete it, we will have a grasp of the nature of the universe, and we will be ready to focus on our place in that universe—the subject of the rest of this book. Guidepost

94. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 94 Hubble’s Law Distant galaxies are receding from us with a speed proportional to distance

95. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 95 I. Introduction to the Universe A. The Edge-Center Problem B. The Necessity of a Beginning C. Cosmic Expansion D. The Necessity of a Big Bang E. The Cosmic Background Radiation F. The Story of the Big Bang

96. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 96 II. The Shape of Space and Time A. Looking at the Universe B. The Shape of the Expanding Universe C. Model Universes D. Dark Matter in Cosmology Does this all go here? Some in GR section…

97. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 97 TFTM 2 Cont… The history of why we believe in galaxies… First observed nebulae ()… lots of them. With better telescopes we could begin to pick out individual stars within them. Kant in 1755 said “gee, maybe these are galaxies like our own Milky Way?” (paraphrase…)

98. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 98 Cephids BHOT page 51

99. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 99 The Age of the Universe Knowing the current rate of expansion of the universe, we can estimate the time it took for galaxies to move as far apart as they are today: T ≈ d/v = 1/H ~ 14 billion years Time = distance / velocity velocity = (Hubble constant) * distance The most distant galaxies known are seen as they were only about 1 billion years after the Big Bang.

100. Evidence for the Big Bang Topic 1: The Exploding Universe Big Bang, Black Holes, No Math 100 Yet more text…