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Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 6, 7 & 8

Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 6, 7 & 8 Prep for Today (Is now due) – L6 Reading: BBBHNM 5 Recommended BHOT: Chap. 1-3 SHU: Chap. 1-2, 3 (p55-69) TOE: Chap. 1 eLearning Quizzes: Chapters 2-3 Reading questions

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Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 6, 7 & 8

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  1. Big Bang, Black Holes, No MathASTR/PHYS 109Dr. David TobackLecture 6, 7 & 8

  2. Prep for Today (Is now due) – L6 • Reading: • BBBHNM 5 • Recommended • BHOT: Chap. 1-3 • SHU: Chap. 1-2, 3 (p55-69) • TOE: Chap. 1 • eLearning Quizzes: • Chapters 2-3 • Reading questions • Two questions from Chapter 5 or the recommended reading • Turned in on eLearning BEFORE class

  3. Prep for Today (Is now due) – L7 • Reading: • BBBHNM 6 • Recommended • BHOT: Chap. 1-6 • SHU: Chap. 1-2, 3 (p55-69) • TOE: Chap. 1 • eLearning Quizzes: • Chapters 2-4 • Reading questions • Two questions from Chapter 6 or the recommended reading • Turned in on eLearning BEFORE class • Started looking at Paper 1

  4. Prep for Today (Is now due) – L8 • Reading: • BBBHNM 6 • Recommended • BHOT: Chap. 1-6 • SHU: Chap. 1-2, 3 (p55-69) • TOE: Chap. 1 • eLearning Quizzes: • Chapters 2-4 • Reading questions • Two questions from Chapter 6 or the recommended reading were due Monday • Turned in on eLearning • Turned in Paper 1

  5. Paper 1 is now posted • What is the evidence for the Earth going around the Sun? • Explain it to someone who isn’t taking the class (no jargon) • Format: • Introduction paragraph • 1 paragraph per piece of evidence • Conclusion paragraph that ties it together • http://faculty.physics.tamu.edu/toback/109/WritingAssignments/samplepaper.shtml

  6. Paper Notes • ~2 pages, double spaced (~600 words) • No citations! Use your own words • Text should be professional. You are “trusted guide” not a “buddy” or “comedian”

  7. Administrative Stuff • Posted on CPR • Can get there from my website or eLearning • Read all the directions carefully • http://cpr.tamu.edu/cpr/resources/documents/misc/Student_Handout.pdf • You will need to submit a copy of your final paper ALSO to the turnitin.com line on eLearning • Due 1 week from today at noon

  8. Paper 1 Stuff – L8 • Your draft was due today at Noon • The calibration and review portions are due next Wed at Noon • http://faculty.physics.tamu.edu/toback/109/WritingAssignments/CPR_Grading.pdf • Paper 2 will be due 1 week after we finish Chapter 8

  9. eLearning Quizzes • You are expected to be working on the quizzes on eLearning • You cannot pass this course without having gotten a perfect score on all of them • You make take as many of each quiz as you like to get perfect scores without penalty • Due before the class AFTER we finish a chapter

  10. Next Set of Topics: Physics We Need Finished our introduction • Big and small things in the Universe • Scientific Method Next we move on learn some of the physics we need in order to understand why scientists have confidence in the Big Bang Theory

  11. 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

  12. The Topics • Some stuff we need learn a little about: • Light and Doppler Shifts • Gravity • Atomic Physics and Quantum Mechanics • Nuclear Physics and Chemistry • Temperature and Thermal Equilibrium • We won’t spend too long on each, just enough to get back to the big picture… • Since there is no perfect way to present them (they all tie into each other) we’ll just start somewhere and get going…

  13. Back to the Big Picture Questions we’re trying to answer: • How did the Universe come into being? • How did it evolve into what we know today? • What is the evidence for all of this?

  14. Light What we know about the universe comes from multiple places One of the most important is from looking at the heavens Need to know more about the “light we see”

  15. Outline for Light • Light is a wave and a particle… • Light is REALLY fast, but does have a finite speed • Doppler effect

  16. Part 1: Light is a Wave • The light we see is a “wave”, like waves on an ocean • Best described by it’s wavelength

  17. Why do we believe light is a wave? • How do waves behave? • Water waves and Sound waves • Can “see” water waves hitting a wall and what happens to them when they hit two small openings in a wall Waves move this way Big Waves Here Small Waves Here

  18. Why do we believe light is a wave? Shine light from a laser at two small holes in a wall and see what comes out on the wall behind it The waves make patterns on the wall the same way water waves do (Physics 202 & 208)

  19. The Wavelength of Light • Shine white light at a prism and it breaks up into its different colors • Each color has a different wavelength which we can measure

  20. What if we look more closely? • What if we look at smaller and smaller “amounts” of light? • The light we see is actually LOTS of particles all moving together • Call these Photons Lots of photons where its bright Very few photons where its dark

  21. Photons What do we know about photons? • Photons are a type of particle • Like an electron or proton • Higher energy  smaller wavelength • Has no mass, but does have energy • Aside for those of you who are interested: It has momentum

  22. White Light = Lots of Different Color Photons

  23. Light is more than the colors we see You may have thought of Radio Waves and X-rays as different things, but they are just light with different wavelengths

  24. A Particle and a Wave • Actually it’s really more complicated than that • Light is both a wave and a particle… can describe it as either… it has properties of both

  25. Part 2: The Speed of Light “Not just a good idea, it’s the law!”

  26. Light has a Finite Speed Light has been measured to have a specific speed • 3 x 108 meters per second • 186,000 miles per second • 1 foot per nanosecond • Really FAST • The fastest speed allowed

  27. Maxwell’s Theory • 1865: James Clerk Maxwell and others showed light was a wave and calculated its expected speed • Gave the observed speed of light! • Confidence that his theories were correct • We can now measure the speed of light to incredible precision Physics 208 2.99792458 x 108 m/s

  28. A Light Year • Some things are so far away that its easier to express their distance in light-years • Light travels at 3 x 108 meters/second and there are p x 107 seconds/year  ~1016 m in a light year • If a star is a light year away and it must have taken a year for the light to get to us, we are observing the star the way it was a year ago • If we look at light from something billions of light years away, we are “observing” things that happened billions of years ago

  29. Part 3: The Doppler Effect • 1842: Christian Doppler • What happens to waves when the “thing” creating the waves is moving towards us? • Or we’re moving towards it? Physics 221

  30. Example with Sound From a Stationary Car The sound we hear is actually a wave • Sound waves

  31. Now the Car is Moving Things coming at us have their waves “scrunched up” Things moving away have their waves “stretched”

  32. The Doppler “Effect” for Cars Hears a Lower Pitched Sound Hears a Higher Pitched Sound A car blaring its horn and going past you will give the famous “Eeeeeeee-Yowwwwww” sound

  33. What Does This Have to with Light? • Since both sound and light are waves, the Doppler “Effect” applies equally to both • Normally can’t see this effect for light since its wavelength is small and its speed is fast • Can in special cases: • Things need to be moving really fast, like stars and galaxies • Need really good measuring devices like the ones Astronomers have

  34. Doppler Effect and Light Red Shift Sees light with a larger wavelength Blue Shift Sees light with a smaller wavelength Galaxy moves to the right 

  35. Look at Light from Galaxies • The light from galaxies moving away from us will appear to have longer wavelength light • The light is more Red, or shifted to the Red side of the light spectrum • “Red Shifted” • The light from galaxies moving towards us will appear with shorter wavelength • The light is more Blue, or shifted to the Blue side of the light spectrum • “Blue Shifted”

  36. The Doppler Effect in Action Doppler Effect

  37. Three Observers What does an object emitting light look like to different observers when it is • Not moving • Moving Doppler Shift

  38. Look at some cases Next lets look at three cases where an “explosions” occurs and things expand from that point • I’m stationary and the exploding things are moving away from me (I’m the center of the Universe) • I’m moving along with the exploding things • Same as case two, but how it would look to me in my reference frame

  39. Two Objects Moving Away from Me What it looks like when I’m stationary (or in my reference frame)

  40. Two Objects Moving Away From Me What it looks like when I’m moving relative to the objects

  41. Same Thing: My Reference Frame Why were these three cases important? Sorry… you’ll have to wait until we look at galaxies sending us light

  42. Doppler Effect and Light: Summary Compare the light coming from a car that’s parked and one that’s coming towards you If a car is coming toward you with its lights on • The color of the light changes • The speed of the light does not!

  43. Putting It All Together Since stars can be billions of light years away and are moving quickly we can use the Doppler effect on light to measure the speed and direction of all objects in the night sky (Can also use it to tell us what Stars are made of, but for that we need to learn about quantum mechanics…)

  44. Outline for Unit 2: Physics We Need • Light and Doppler Shifts Done • Gravity Next • Atomic Physics and Quantum Mechanics • Nuclear Physics and Chemistry • Temperature and Thermal Equilibrium

  45. Prep for Next Time – L6 • Reading: • BBBHNM 6 • Recommended: BHOT 4-6 • Reading questions • Two questions from Chapter 6 or the recommended reading • Turn in on eLearning BEFORE class • eLearning Quiz • Chapter 4 • Start working on Paper 1

  46. Prep for Next Time – P7 • Reading: • BBBHNM 6 • Recommended: BHOT 4-6 • Reading questions • Two questions from Chapter 6 or the recommended reading • Turn in on eLearning BEFORE class • eLearning Quiz • If we finished Chapter 5, quiz due before the next class (else just 4) • Start working on Paper 1

  47. Prep for Next Time – P8 • Reading: (Was due Monday) • BBBHNM 6 • Recommended: BHOT 4-6 • Reading questions • Two questions from Chapter 6 or the recommended reading were due Monday • No new reading questions • eLearning Quiz • Chapter 5 quiz due before the next class • Calibrations for Paper 1 due Wed at noon

  48. Full set of Readings So Far • Required: • BBBHNM: Chap 1-6 • Recommended: • BHOT: Chap. 1-6 • SHU: Chap. 1-3 • TOE: Chap. 1

  49. End of Lecture

  50. In-Class Quizzes • Turn in your two questions on the reading • During class you will write down two more • This is a separate quiz • If you didn’t get a grade you wanted on one of the first few reading quizzes see me about trying again

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