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INST 2403 The Expanding Universe

INST 2403 The Expanding Universe. INST 2403 The Expanding Universe. Dr. Uwe Trittmann Utrittmann@Otterbein.edu Office: Science 107 Phone: 823-1806 Secretary: Celina Chou (823-1316), Science 308 Office Hours: MW 1-1:30& 3-3:30pm or by appointment. Course Materials. Textbooks:

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INST 2403 The Expanding Universe

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  1. INST 2403The Expanding Universe

  2. INST 2403The Expanding Universe Dr. Uwe Trittmann Utrittmann@Otterbein.edu Office: Science 107 Phone: 823-1806 Secretary: Celina Chou (823-1316), Science 308 Office Hours: MW 1-1:30& 3-3:30pm or by appointment.

  3. Course Materials • Textbooks: • Astronomy: A Beginner’s Guide to the Universe, 7thEdition, by Chaisson and McMillan (Addison-Wesley 2012) • Lecture Tutorials for Introductory Astronomy, 3rd ed., by Edward E. Prather, Tim P. Slater, Jeff Adams, and Gina Brissenden (Benjamin Cummings) • Need to buy WebAssign access, too! • Course Web Page: http://faculty.otterbein.edu/utrittmann/is2403-02/ • Observatory schedule, lecture notes, study guides, the syllabus, notices, online resources, …

  4. Assignments and Grading

  5. Daily Homework & Warm-Ups • Before class (8am): answer warm-up questions online about reading for the day • http://neutrino.otterbein.edu/~tagg/Courses/Tools/WarmupDB/IS_Astro_F14_2 • After Class: use WebAssign, an online homework system daily! • Password & username: first initial plus last name all lowercase, e.g. utrittmann

  6. iSkylab • Equivalent of a term paper, but more experimental • 4 different stages • Start early - weather is always a factor • Ask questions! • Due Sep 24, Oct 27, Nov 19, Dec 8

  7. Every Day (MWF) • Do the textbook reading • Look over the Powerpoint slides for the day • Answer the Warm-Up questions due 8am • Come to lecture & participate • Ask questions about homework, etc. • Do the homework due at night

  8. A Glance at this Class • The whole universe in 14 weeks!? • Expect to work at least as hard for this course as for your major classes; 2hrs out of class per class • The focus is on concepts, not facts; on the methods and tools of science: • How do we know? • How can we measure it? • How can we predict it?

  9. Teaching Philosophy • Teaching is merely an invitation to learn • You have to learn yourself! • Operational instead of Declarative Knowledge • Peer instruction • Class discussions • Participation (Credit!) • Must engage with the material

  10. Peer Instruction: How it works • Peer instruction is learning by instructing your fellow students and being instructed by them • The process involves 6 steps: • Mini-lecture by course instructor • Conceptual multiple-choice question is put up • Flash-cards are used to “poll the audience” • A few minutes of discussion between students • “Final answer” via flash-cards • The instructor explains the correct answer

  11. Who was the first man on the Moon? • Yuri Gagarin • Buzz Aldrin • Neil Armstrong • John Glenn

  12. Concept Questions • Concept questions maybe easy to answer, but are not simple • You need background knowledge to answer them • They teach you how to use facts and knowledge to find the answer to a problem • They test if you got the concept rather than just knowing facts

  13. It is New Moon. In one week, what will the phase of the Moon be? • New Moon • First Quarter Moon • Full Moon • Last Quarter Moon

  14. Why it works • Carefully chosen questions • It is easier to be convinced and to convince if the reasoning is sound and hence the answer correct Right to right Wrong to right Right to wrong No 2nd answer wrong to wrong How answers are revised in a typical question

  15. Science and Quantitative Reasoning • Without quantitative reasoning there is no progress in science (Galileo) • However, (quantitative) reasoning is also very useful in everyday life • Interest rate, gas mileage, buying a used car, that guy from Nigeria…

  16. Making Sense of Numbers • Want to compare to relevant scale  choose convenient units • Underlying concepts have to be clear • There is evidence that the disconnect between scientists and the public starts at simple concepts, like area, volume, ratios and graphs • We’ll start there and we’ll move up to the stars!

  17. Example: Relevant Scales • The mass of the Earth is 6 x 1024 kg • This number can be used in equations easily • Nobody has a sense of how heavy that is • Need to compare to relevant scales • Mass of Sun: 2 x 1030 kg  Sun’ mass = 300,000 Earth masses • Mass of Jupiter: 2.4 x 1027 kg 300 Earth mass = 1 Jupiter mass • Mass of Venus: 4.7 x 1024 kg  1 Venus mass =1 Earth mass • Relevant Scale: 1 EM = 1 Earth mass

  18. Example II • The radius of the Earth is 6 x 106 m • Convert to miles (1mile = 1600m): 3800 miles • That is something we can fathom • Now: use it to get insight!

  19. Insight from Numbers • We know ANY volume scales like the radius to the third power • Volume of Earth: 63 x (106) 3 m3 = 216 x1018 m3 = 1 EV • Sun (radius 7 x108m): 1.5 million Earth Volumes • But: only 300,000 times the Earth mass! • Conclusion: the Sun is made from material that is 5 times lighter than the stuff the Earth is made of!

  20. Asking questions to ask questions • Scientists often come off as pretending to know everything (Sheldon) • In fact, they have a healthy self-confidence that they can at least say something about everything • Why? They simplify things enough to make a rough estimate, then compare to reality • Correct? Hah! I was right! • Not correct? How interesting! We can explore more!

  21. Example: How many people live in Australia? • No idea. • But: Need to say something • Can get size of this continent • Know size & inhabitants of USA • Proportionality tells us there should be XX million Australians • Conclusion: there are much fewer! • Next Question: Why?

  22. Don’t be fooled by what you see! • The sun and the moon appear to be the same size in the sky (0.5 degrees) • Alpha Centauri appears to be much dimmer than the Sun • Alpha Centauri and Vega appear to be equally bright • Are you upside down?

  23. Think! • The moon and the sun COULD be at different distances • Alpha Centauri and Vega COULD be different types of stars • YOU could be upside down! • The apple COULD attract the Earth with the same force  Expand your universe!

  24. Top Down • The Universe is accelerating its Expansion • How do we know? • Supernovae are dimmer than they should be in a standard expanding universe • What is a supernova? What is a standard universe? • SN are massive stars exploding at the end of their lives • How do we know?

  25. Top Down • Stars are hot gas balls that fuse H to He; they run out of fuel • How do we know? • Can measure spectra, compare to the sun • What is a spectrum? How does the sun “work”? • The sun is 300,000 more massive than the earth, consists of H & He, produces a lot of energy  must be fusion • How do we know?

  26. Top Down • Measure distance to sun, use Newton gravity to obtain mass, measure H & He spectra in lab • How do we measure distance to sun? • What is Newton gravity? • What are spectra in the lab? • Use Kepler’s laws, observe special configuration of planets from different positions on earth • What are Kepler’s laws? How big is Earth?

  27. Top Down • Planets go around the sun in ellipses • How do we know? • The observer’s view is different for different places on Earth  radius • How do we know Look at the sky!

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