Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 1 Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 5 & 6

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 2 Prep For Today (is now due) – L6 Reading: –BBBHNM Unit 2 (Chapters 5-9) Pre-Lecture Reading Questions –eCampus Quizzes 1-6 Check these, some were fixed and changed scores –Unit 2: Stage 1 –Unit 1 Revision (if needed) Stage 1: Due Wed before class End-of-Chapter Quizzes –Chapter 3

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 3 Next Topic: Scientific Methods Unit 1: 1.Introduction  Done 2.Going Big  Done 3.Going Small  Done 4.Evidence and the Scientific Method Today we move on to the Questions and How we go about answering them

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 4 Plan for the Next Few Weeks 1.More on the Questions and How we go about answering them 2.Some of the history to teach us about the method 3.Need to learn some physics } Today } Next Unit

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 5 Next few Weeks Continued… To learn Cosmology will need to learn a bit about: 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 Won’t spend too long on these, just enough to get back to the big picture…

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 6 Evidence and The Scientific Method What are the clues at the scene of the crime? How can we use the clues to figure out what happened? Any WHY? Scientific Method –How do we know what we know? –What is the evidence for some of the “true things” we heard growing up? E.g.Earth goes around the Sun

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 7 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 –We can misinterpret the clues As you’ve already seen, the world is incredibly complex and much of it is different from what we experience –Good clues are hard to find, sometimes hard to interpret

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Single example to Show the Scientific Method in Action People have watched the sky and noticed that the stars (the dots of light in the sky) basically all move together over the course of the night and over years Five of them behave differently –Start this story in the 2 nd century 8

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Fun Videos of Just the Stars 9 Start with things you can see with your own eyes! Video of stars moving with Polaris (north star) at the center Video of stars moving, including the Milky Way (from Chile)

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 10 Ptolemy’s Universe (2 nd century) The Sun, Moon and Stars go around once a day, but a few (the planets) change their position relative to the other stars a little every night Every so often the planets move backward through the stars for awhile Hypothesis: They orbit the Earth in mostly circular paths Best guess: these are mini- orbits way out there (epicycles)… Hmmm…

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Looking at Mars in the Stars 11

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 12 How Ptolemy envisioned it y.model.swf://bigbang.physics.tamu.edu/Figures/StolenAnimations/ptolem y.model.swf The big circle is the main orbit, and the little circle is the epicycle This explains why the planets seem to go back and forth out there in space (retrograde motion) every so often

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 13 Cracks in the `early cosmology’ In 1514, Copernicus hypothesized that Planets and Earth orbit the Sun Much simpler in some ways  no epicycles More complicated in others  Says Earth is rotating

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 14 Epicycles??? etrograde_motion.swf://bigbang.physics.tamu.edu/Figures/StolenAnimations/mars_r etrograde_motion.swf A more modern view of the motion of the Earth and Mars and the stars behind them (from the point of view of the center) How would this explain the epicycles that people saw?

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 15 If we lived in the 1500’s, should we believe Copernicus? 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? Why doesn’t it rotate under us when we jump?

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 16 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

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 17 Data Provides Evidence Discover moons orbiting Jupiter!  Solid evidence that not EVERYTHING orbits the Earth!

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Another Piece of Evidence Can understand the phases of the Moon because of the locations of all three Not eclipses 18

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Venus Consider the two different versions of how Venus is predicted to move in space 19

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math The Phases of Venus 20 Venus has a full set of phases, like the moon Sunlight shining off Venus and to our eyes No good way to explain this if Venus goes around the Earth

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math More data With better data Kepler realizes an even better description of the data is that all planet orbit the Sun in an ellipse, not a circle Sun-centered model now agrees with the high-quality observed data, Earth centered does not No good REASON for ellipses though… then again, no good reason they should be circles (except people LIKE circles, and they are more “perfect”) 21

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 22 The next generation…Newton Newton puts forward his theory of Gravity and describes it as a Force So what? The same force that pulls an apple to the ground from a tree ALSO pulls the planets towards the Sun and keeps them in orbit This “explains” why both the orbits are ellipses AND why we don’t fall off a spinning Earth Isaac Newton 1687

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 23 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

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 24 Outline for Unit 2: Physics We Need Topics 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

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math PLRQ Unit 1 Grades Criteria for Pass/Revise grades for CPR Unit 1 are described in the FAQ and the Lecture notes Will post the grades in eCampus after we are done with re-grade requests You should go to eCampus to make sure you got the grade you think you did. Many people are surprised. Let us know if you think you were misgraded or we gave you the wrong grade What do you do if your eCampus grade says “Revise”? –See 109FAQ.shtml#CPRGrades 109FAQ.shtml#CPRGrades 25

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 26 Prep For Next Time – L5 Reading: –Required: BBBHNM Unit 2 (Chapters 5-9) –Recommended Reading: See P3 of Pre-Lecture Reading Questions –Stage 1 for Unit 2 due before Class –Stage 1 in CPR for Unit 1 Revision will be assigned after grades are posted End-of-Chapter Quizzes –If we finished Chapter 4 then End-of- Chapter Quiz 4 (else just Chapter 3)

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 27 Prep For Next Time – L6 Reading: –BBBHNM Unit 2 Pre-Lecture Reading Questions –eCampus quizzes (all 6) –Unit 1 Revision (if needed): Stage 1 before Class Let us know if you were misgraded –Unit 2: Stage 2 due before class End-of-Chapter Quizzes –If we finished Chapter 4 then End-of- Chapter Quiz 4 (else just Chapter 3)

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Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 29 Clicker Quiz A muon is observed to decay into an electron and two different neutrinos. Is a muon considered a fundamental particle? a)No, because it has the electrons and neutrinos inside it so it can't be fundamental. b)Yes, because it isn't composed of electrons and neutrinos, it just decays into them c)No, because fundamental particles can't decay

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 30 Clicker Quiz Q: What does it mean for an electron to be "stable?" a)It is balanced with exactly one proton b)Its orbit ring exists in one plane (no wobble) c)It has reached minimum size ( m) d)Undisturbed, it can go on living forever and ever e)They don't appear to be made of anything smaller

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Paper 0 Stuff Want feedback before turning it in? –Post it in eCampus in.doc (or.pdf) for comments by the TA by 5PM Friday –Make sure you polish it If you have lots of grammar and spelling mistakes we’ll just make you resubmit it 31

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math PLRQ Concerns Many people don’t seem to realize that there were two different PLRQ assignments –In eCampus: Quizzes 1-4 –In CPR: Submit questions (Stage 1) and do all the Review parts (Stage 2) in CPR Let us know if you think you were misgraded How to tell if you need to do a Revision –Only the grade in eCampus matters –Why didn’t I pass? What do you need to do if your eCampus grade says “Revise”? –See 109FAQ.shtml#CPRGrades 109FAQ.shtml#CPRGrades 32

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 33 Prep For Today (is now due) – L5 Reading: –None Pre-Lecture Reading Questions –Unit 1: Grades posted. End-of-Chapter Quizzes –Chapters 2 and 3

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 34 Prep For Next Time – L5 Reading: –Required: BBBHNM Unit 2 (Chapters 5-9) –Recommended Reading: See P3 of f f Pre-Lecture Reading Questions –Unit 1 Revision (if Needed): Stage 1 in CPR due before class Let me know if you think you were misgraded Must do entire assignment if your grade in eCampus says “Revise” –Unit 2: Stage 1 due before class No more eCampus stuff for PLRQ End-of-Chapter Quizzes –If we finished Chapter 4 then End-of-Chapter Quiz 4

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Some words; “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; can be tested” 35

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 36 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 Does the world function in a “predictable” manner? What happens when you test a hypothesis?

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 37 What Makes a Good Theory? Two requirements: 1.It must accurately describe a large class of observations, clues, or other pieces of evidence. –For example g, the acceleration due to gravity. Same everywhere on the Earth? 2.It must make DEFINTE PREDICTIONS about the results of FUTURE (not yet done) observations or experiments Creates testable hypotheses An astronaut hits a golf ball on the moon. Can we predict its path?

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 38 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 –It has been said that “even the most beautiful theory can be slain by a single ugly fact” If the theory makes predictions for a new experiment and the data agrees then it gives us really good reason to believe there really are underlying principles in the world we live in

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 39 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…

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Everyday Conversation Explanations that stand the test of time and LOTS of experiments are what we call Theories –Gravity, Quantum Mechanics etc. When someone says “Well… It’s a theory” we know what they mean. They mean “it’s a hypothesis” –We don’t yell at them for the same reason we don’t get upset when someone says the “Sun is setting” 40

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 41 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?

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 42 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?

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 43 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? Do we change our mind if we don’t LIKE the implications of the theory? (The Earth isn’t the center of the universe)

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 44 Fact is Stranger than Fiction Typically we have confidence in 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… Stood up to 90 years of experiments –Will talk in the next unit about what’s weird about them, and what weird things they predict and explain

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Another Piece of Evidence Can understand the phases of the Moon because of the locations of all three Not eclipses 45

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math The Phases of Venus Venus has a full set of phases, like the moon –Sunlight shining off Venus and to our eyes No good way to explain this if Venus rotates around the Earth 46

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Class trip to Cyclotron Clicker question Any interest in a class trip to the Cyclotron? If so, which day would you be most interested A = Wednesday B = Friday C = Other day please!!! D = Not likely to make it 47

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 48 Prep For Next Time – L5 Reading: –BBBHNM: Chap 5 Reading Questions: –Two questions from Chapter 5 or the recommended reading End-of-Chapter Quizzes –If we finished Chapter 4 then end-of-chapter quiz 4 (else just 3)

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 49 Prep For Next Time – L4 Note: May change depending on how far we get in lecture (some may have already been due) Reading: –BBBHNM: All reading up to Chapter 6 Pre-Lecture Reading Questions: –Two reading questions from Chapter 6 End-of-Chapter Quizzes –If we finished Chapter 4 then end-of-chapter quiz 4 (else just 3) Paper 0 –Paper 0 has been posted on CPR –If we finished Chapter 4, then Paper 0 is due one week from today

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 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 50

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 51 Prep for Today (Is now due) – L5 Reading: –BBBHNM: Chap 4 Reading questions –Two questions from Chapter 4 End-of-Chapter Quizzes: –Chapter 3

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Phase I, Phase II and Phase III Phase I: (Paper due 1 week after we finish Chapter 4) Turn in a polished draft to eCampus TA’s will provide feedback, but not if there are multiple spelling/grammar mistakes Pass/Fail grade Phase II: (Due one week after Phase I) A revised version will be done 1 week later on CPR When you submit to CPR (after revision), you will need to also submit a copy of your to the turnitin.com line on eCampus Phase III: (Due one week after Phase II) Calibrations and Reviewing due one week after you submit 52

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math Paper 0 Stuff – L9 faculty.physics.tamu.edu/toback/109/WritingAssignments/ Phase I: Due last Wednesday –You will get feedback soon, work on revisions now – if you need an extension Phase II: –Due in CPR/Turnitin.com Wednesday Phase III: –Will talk more about CPR and reviewing Wednesday –Following Wednesday 53

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 54 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

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 55 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

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 56 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

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 57 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?

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 58 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)

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 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? 59

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 60 Epicycles…

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Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 62 Copernicus Continued This is a test…

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 63 Ptolemy Eight “bodies” rotating the earth in circular orbits (2 nd 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

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 64 Kepler

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 65 Ptolomy

Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 66 Brahe

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Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 68 SHU: Chapter 1 Eratosthenes (Greek mathematician) Different length shadows at the same TIME of day. Pictures? Pages 22 and 23

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Introduction Topic 4: Scientific Methods Big Bang, Black Holes, No Math 73 Greek view of the universe