Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 5 & 6

1. Big Bang, Black Holes, No MathASTR/PHYS 109Dr. David TobackLecture 5 & 6

2. Prep for Today (Is now due) – L5 • Reading: • BBBHNM 5BBBHNM: Chap 1-4 • Recommended • BHOT: Chap. 1-3 • SHU: Chap. 1-2 • TOE: Chap. 1 • eLearning Quizzes: • Chapters 2-3 • Reading questions • Turn in now

3. 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

4. Next Topic: Scientific Methods Unit 1: • Introduction  Done • Going Big  Done • Going Small  Done • Scientific Methods Today we move on to the Questions and How we go about answering them

5. Plan for the Next Few Weeks } • More on the Questions and How we go about answering them • Some of the history to teach us about the method • Need to learn some physics Today } Next Unit

6. Next few Weeks Continued… To learn Cosmology will also need to learn a bit about: • Light and Doppler Shifts • Gravity • Atomic Physics and Quantum Mechanics • Nuclear Physics and Chemistry • Temperature and Thermal Equilibrium Won’t spend too long on these, just enough to get back to the big picture…

7. History and The Scientific Method • What are the Questions and how do we go about answering them? • Scientific Method • How do we know what we know? Why do we believe the stories we heard growing up? • History as example… • Observation (looking at the heavens)

8. How do we know what we know? • We have a lot of experience in the world around us • Unfortunately, our experience is really lousy in guiding us to really understanding the bigger (and smaller) world around us unless we’re really careful • As you’ve already seen, the world is incredibly complex and much of it is different from what we experience

9. Worse… Actually, it’s even worse • What we “believe” can deceive us from understanding how things actually work • Unfortunately, our history is littered with “Just-so stories…” that have set back our understanding

10. History and Just-So Stories State of our understanding 2500 years ago: “The earth is, obviously, flat…” So, how DID they figure out the earth is round? • Ships on the horizon: Top of the mast first • Aristotle (340 BC): The earth’s shadow on the moon

11. How did people ages ago understand the stuff in the sky? People have been trying to understand the heavens for ages and arguing about what’s really going on… Pumbaa: Timon? Timon: Yeah? Pumbaa: Ever wonder what those sparkly dots are up there? Timon: Pumbaa. I don't wonder; I know. Pumbaa: Oh. What are they? Timon: They're fireflies. Fireflies that uh... got stuck up in that big... bluish-black... thing. Pumbaa: Oh. Gee. I always thought that they were balls of gas burning billions of miles away. Timon: Pumbaa, wit' you, everything's gas. • More serious observers noticed that all the “stars” move together, except for 5 that move weirdly… • Call these (and Sun and Moon) “wanderers” or Planets (Greek for wanderer) http://bigbang.physics.tamu.edu/Animations/BallsOfGas.mpg

12. Ptolemy’s Universe (2nd century) Observe that the Sun, Moon and the other “wanderers” orbit the Earth in mostly circular paths Every so often the planets move backward for awhile, but these could be me mini-orbits way out there (epicycles)… Hmmm…

13. Looking at Mars in the Stars

14. Epicycles… http://bigbang.physics.tamu.edu/Figures/StolenAnimations/mars_retrograde_motion.swf.swf

15. What we “believe” can mislead us • We “see” the sun/moon go around the Earth, must be so! • The Church demanded that this model be accepted for Religious reasons… • Man should be at the center of the universe • Circular orbits – Perfection! • This model was accepted for nearly 1500 years

16. Cracks in the `early cosmology’ In 1514, Copernicus wrote that Planets and Earth orbit the Sun Much simpler in some ways  no epicycles More complicated in others  Earth must be rotating

17. If we lived in the 1500’s, why should we believe this crazy guy? The Earth isn’t at REST and rotates? • Shouldn’t we FEEL this? • If the Earth is rotating why don’t we fall off like an ant on a bicycle wheel? • Why don’t we feel a wind as we rotate?

18. An interesting aside… • The Church was COMPLETELY opposed to this view for religious reasons • Then again…Copernicus was a polish priest and was lucky enough to live far from Rome so he could safely be ignored by the Church • Interesting how the church seems to both be the great mover forward, and the great obstacle…

19. Cracks in the `early cosmology’ Should his view have just “been accepted”? Perhaps his theory was just a “different interpretation” of the same data? • Both models are consistent with observations Need more evidence! Need a better TOOL to test, experimentally, which is correct Early 1600’s: Kepler and Galileo started gathering data from telescopes

20. The Moons of Jupiter • Data changes everything… • Moons orbit Jupiter!  Solid evidence that not EVERYTHING orbits the Earth! • Planet paths are ellipses, not PERFECT circles, but pretty understandable • Copernicus’s models now better predicts the observed data

21. Phases of the Moon • Can understand the phases of the Moon because of the locations of all three

22. The Phases of Venus • Venus has phases, like the moon • No good way to explain this in Ptolemy’s system

23. Interesting aside Continued: The backlash… • These findings contradicted the Church! • Now scientists have a problem: Galileo was a leading scientist in Italy (close to Rome!) and he was Loud! • The Church spurned this as heretical and set back science (nearly ex-communicated, sentenced to life of house arrest)

24. The next generation…Newton • Newton writes that there is Gravity and that it is a Force • So what? The same force that pulls an apple to the ground from a tree ALSO pulls the Moon towards the Earth and keeps it in orbit • This “explains” the orbits (and why we don’t fall off a spinning Earth) Isaac Newton 1687

25. Scientific Method The history is fun, but we have a problem: • How do we separate true stories from stories we’d like to believe, but aren’t actually true? • Need EVIDENCE and a good Scientific THEORY • Good hypothesis testing

26. “It’s a theory…” • Theory:“A set of rules that relate quantities in a model to observations we make” • Hypothesis:“A tentative assumption that is useful in that it predicts the outcome of an experiment and can be tested”

27. Science • For us to “believe” in a theory, or said better, to think it might correspond to truth, we agree that it has to be tested in such a way it can be tested over and over again such that the results must always confirm the theory • Do things function in a “predictable” manner? • What happens when you test a hypothesis?

28. What Makes a Good Theory? Two requirements: • It must accurately describe a large number of types of observations based on a few arbitrary elements • For example g, the acceleration due to gravity • It must make DEFINTEPREDICTIONS about the results of FUTURE (not yet done) observations • Creates a testable hypothesis

29. Yet more on Scientific Method • It also must be falsifiable • If we do an experiment and the results disagree with the predictions of the theory, then the theory is wrong or has to be modified… • But, if we can make predictions for an experiment that’s never been done with incredible accuracy and the data agrees then it gives us really good reason to believe there really are underlying principles in the world we live in

30. What science does not promise Science does not promise eternal truths Only promises the systematic elimination of false hypotheses and the establishment of what is currently the most likely explanation of an aspect of reality…

31. Better experiments… At some point our experiments get so good that we can “observe” things that our eyes can’t see directly • The very small • The very faint and/or far away What happens if the theories that explain what we can see with our eyes don’t explain what we see in a microscope?

32. Weirdness… Have to try new weirder theories • What if we come up with a theory that accurately “predicts” the results of both the experiments we can do with our eyes AND the really sensitive ones we can do with really special microscopes? • What if that theory is counter to our intuition?

33. More weirdness • What if our weird theory then makes further weird predictions? • What if it predicts that if we do a simple experiment we will get crazy results? • What if we DO the experiment and GET the crazy results? At what point do start believing there is some “truth” to the theory?

34. Fact is Stranger than Fiction • Typically we tend to believe that theories that do a good job of predicting the results of experiments have some basis in reality • In the 1920’s scientists starting coming up with such theories:General Relativity and Quantum Mechanics are good examples… • Will talk in the next unit what’s weird about them, and what weird things they predict and explain

35. 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

36. 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”

37. 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

38. Next Topics: Unit 2 • Light and Doppler Shifts • Gravity • Atomic Physics and Quantum Mechanics • Nuclear Physics and Chemistry • Temperature and Thermal Equilibrium

39. Prep for Next Time • Reading: • BBBHNM 5 • Recommended: SHU: 3 (p55-69) • Reading questions • Two questions from Chapter 5 or the recommended reading • Turn in on eLearning BEFORE class • eLearning Quiz • Chapter 4 • Start working on Paper 1

40. Full set of Readings So Far • Required: • BBBHNM: Chap 1-5 • Recommended: • BHOT: Chap. 1-3 • SHU: Chap. 1-3 (p55-69) • TOE: Chap. 1

41. End of Lecture

42. The Church and Science • It’s easy to pick on the church with hindsight • Then again, much of the great progress in our understanding of the physical world comes because science (and lots of other things) were its beneficiary • In today’s lingo “The Church” was the one of the few funding agencies for hundreds of years… • What if you weren’t independently wealthy and wanted to do science? (Want to learn to read???) And be able to eat? Either become a priest or a monk… Maybe work for a King?

43. Reading Quizzes • We are not looking for questions where we could get the answer on Google (which you could do) • Wrong questions: • How big is the largest planet we’ve found? • When was the telescope invented?

44. Epicycles…

46. Copernicus Continued • This is a test…

47. Ptolemy • Eight “bodies” rotating the earth in circular orbits (2nd century BC). • People accepted this theory even though it had problems (moon should be twice as big..) • Church liked it… it stuck and was largely unquestioned • It didn’t offend anyone

48. Kepler

49. Ptolomy

50. Brahe