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Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 12 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 1 Was due Today – L12 • Reading: – (BBBHNM Unit 2) • Pre-Lecture Reading Questions – Unit 1 Grades: If you received a Contact Instructor, send me an email. Will work with you. – Let us know if you were misgraded on any assignments • End-of-Chapter Quizzes: – End-of-Chapter Quiz 7a & 7b • Paper 1: – (Stage 2 due Wednesday before class in CPR) • Make sure you have submitted to both CPR and turnitin on eCampus • Honor’s Paper: – Stage 1: Due March 7th. You should have your source materials and be finishing reading them soon Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 2 Heads Up: Paper 2 • What is the evidence that Stars are made of Atoms? • This will be the topic of Paper 2 • In order to understand the evidence, we next talk about Atoms and how they work • Will be assigned after we finish Chapter 8 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 3 Outline for Unit 2: Physics We Need 1. Light and Doppler Shifts Done 2. Gravity, General Relativity and Dark MatterDone 3. Atomic Physics and Quantum Mechanics Done 4. Nuclear Physics and Chemistry This time 5. Temperature and Thermal Equilibrium Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 4 Looking at the Lights in the Sky What we know about the universe comes from multiple places So far: • Learned about the light coming from the sky • Learned that atoms can produce this Physics We Need Big light Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 5 Questions We’re Trying to Answer • What are stars made of? • What can we learn from looking at them? • How do we know? What is the evidence Today: More about different types of atoms that produce the light A “smoking gun” piece of evidence that the light from the sky is from atoms out there Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 6 Outline • Overview • What protons and neutrons are made of: Quarks • How protons and neutrons interact & combine to form a nucleus • Chemistry • Spectral lines – Light from stars! • Learning about the stars Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 7 Overview of the story • Big things are made from LOTS of small things • Small things: The Fundamental Building Blocks of Nature – What is the “stuff” in atoms • ElectroMagnetism (electric charge) – What holds electrons and protons together • Quantum Mechanics – Why atoms form the way they do – Electron in orbits – Atoms absorbing and emitting photons (light) • Different TYPES of Atoms – The Strong Force – Keeping protons and neutrons together (atomic nuclei) – Nuclear Physics and Chemistry – Different atoms Different light… • Studying the Stars using their light – Spectral lines of the atoms – Atomic “fingerprints” – The light we see from the stars Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry Last Lecture This Lecture 8 Smaller Building Blocks of Nature • Atoms are made of a nucleus surrounded by electrons –Many types of nuclei –Only one kind of electron • Nuclei is composed of neutrons and protons –Neutrons and protons are two different types of nucleons • Nucleons are made of quarks Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 9 Chemistry • We can put nucleons together in lots of different ways… • Each different way corresponds to a different type of atom Knew about the periodic table in the 19th century Understood it was just combinations of protons and Physics We Need neutrons in the 1920’s 10 Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry Observation: Different Kinds of Atoms • The kind of atom depends on the number of protons in the nucleus • Helium (He), with 2 protons, 2 neutrons and 2 electrons Different numbers of neutrons ↔ different isotopes Helium 4 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 11 Why do nucleons stick together? • If what holds the atom together is the opposite charge of the protons and the electrons… Why don’t the same sign charges of the protons “blow the nucleus apart?” Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 12 What Nucleons are Made Of • Each nucleon is made of 3 quarks • Two different types of quark • Called “up” quarks and “down” quarks • Each quark has fractional charge Big Bang, Black Holes, No Math More to say Physics We Need 13 this later Topic 4: Nuclear Physicsabout & Chemistry What holds the quarks together? • The strong force holds the quarks together inside the nucleon • The force mediator is the “gluon” – Quarks talk to each other via gluons Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 14 The Answer The same strong force keeps the nucleons together Essentially the gluons “leak” out of the nucleons and provide the attractive force Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 15 So what? • Why do we care about all the different kinds of atoms? • What does this have to do with Stars and the Big Bang? • The different mass and charge of each nucleus means that each as a different set of energy levels – Each one has unique fingerprints! Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 16 Different energy levels for each different type of atom Fingerprinting the different atoms Hydrogen Helium Boron Can use light of different energies to identify atoms: Different Colors Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 17 Atomic Fingerprints • Each atom produces a large number of different wavelengths with VERY SPECIFIC values • Quantum Mechanics predicts ALL of them • If you see all the ones you expect and none you don’t, that gives you confidence Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 18 More on Fingerprinting • Look at light from a light bulb with Hydrogen gas in the way • Different lines will be absorbed by Helium • Can now identify a mystery gas! Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 19 Overview of the story • Big things are made from LOTS of small things • Small things: The Fundamental Building Blocks of Nature – What is the “stuff” in atoms • ElectroMagnetism (electric charge) – What holds electrons and protons together • Quantum Mechanics – Why atoms form the way they do – Electron in orbits – Atoms absorbing and emitting photons (light) • Different TYPES of Atoms – The Strong Force – Keeping protons and neutrons together (atomic nuclei) – Nuclear Physics and Chemistry – Different atoms Different light… • Studying the Stars using their light – Spectral lines of the atoms – Atomic “fingerprints” – The light we see from the stars Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry Last Lecture This Lecture 20 Using Light From Stars •Can look at the light from the stars to “see” if they are made of atoms •Figure out what TYPE of atoms… •How stars are formed… •What makes them shine… Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 21 What is a Star? • Our best understanding is that stars are great big balls of (mostly) hydrogen gas • The hydrogen interacts and produces the light we see – Makes them shine… • What is the evidence for this? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 22 Stars • What would happen inside a giant ball of hydrogen? – Interactions • What would it look like to us? – Light from the interactions – Next look at Physics Big Bang, Black interactions We Need Holes, No Math Topic 4: Nuclear Physics & Chemistry 23 Hydrogen Interactions Proton Proton + Proton Deuterium + Anti-Electron + Neutrino Nuclear Reaction AntiElectron Deuterium Neutrino Proton Big Bang, Black Holes, No Math The Deuterium, neutrino and the AntiPhysics We Need 24 Electron get energy in the reaction Topic 4: Nuclear Physics & Chemistry More interactions Deuterium Proton + Deuterium Helium3 + Photon Photon Nuclear Reaction Helium3 Proton Physics Needalmost any Big Bang, Black Photon canWe have Holes, No Math Topic 4: Nuclear Physics & Chemistry 25 energy Creating Stable Helium Helium3 Helium3 + Helium3 Helium4 + 2 Protons Nuclear Reaction Proton Helium4 Helium3 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry Proton 26 Stars • Nuclear interactions in the center of the star create lots of energy which is eventually emitted as light from the surface of the star – Shines white (or yellow) • This light passes through other atoms of the star – Light is “absorbed” by the outer atoms Spectral lines • Tells us what the stars are made of Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 27 Looking at the Stars Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 28 Analyzing Absorption Spectra • Each element produces a specific set of absorption (and emission) lines • Using this information, we can study the composition of stars See only spectral lines for known atoms Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 29 Remarkable… • The Sun and stars are mostly made of Helium and Hydrogen • Our Sun is made of the same stuff as all the other stars! • The stuff out in the universe is made of the same stuff that is found here on Earth! Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 30 Even More Remarkable If all the stuff “out there” looks the same as the stuff here on Earth then: –The particles out there (electrons, protons, photons etc.) are the same as they are here – The laws of physics that govern putting together protons, nuclei and atoms are likely to be the same everywhere! – Provides evidence that it’s been this way for billions of years! Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 31 Now that we know what stars are made of and what they are SUPPOSED to look like, can we learn anything else? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 32 •What if the stars were MOVING? •Can we tell? Yes! Doppler effect How? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 33 Atoms with Different Speeds • If an atom emits a photon it will correspond to an energy that reflects the change of two energy levels • However if the atom is MOVING the light will be shifted to a different color Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 34 Observing an Atom Atom Emitting Light Not Moving Moving to the right Can use this to study the motions of the stars Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 35 Looking at the Stars Provides additional evidence stars are made of atoms Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 36 Lecture on Chapter 8 now complete Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 37 Paper 2 • Abbreviated description: What is the evidence that Stars are made of Atoms? – More detail on CPR, you REALLY need to read ALL the instructions • 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/WritingAssignmen ts/samplepaper.shtml Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 38 Phase I and Phase II in CPR Phase I: (Due 1 week after we finish Chapter 8) • Submit online two ways: CPR and turnitin.com Phase II: (Due one week after Phase I) • Three-Part Calibrations/Reviewing 1. Calibrations, learning to use the Rubrics 2. Grade three other papers 3. Grade your own paper Want feedback before you submit? Get it to the TA on eCampus by Friday for guaranteed feedback. Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 39 Outline for Unit 2: Physics We Need 1. Light and Doppler Shifts Done 2. Gravity, General Relativity and Dark Matter Done 3. Atomic Physics and Quantum Mechanics Done 4. Nuclear Physics and Chemistry Done 5. Temperature and Thermal Equilibrium Next time Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 40 Prep For Next Time – L12 • Reading: – (BBBHNM Unit 2) • Pre-Lecture Reading Questions – Unit 1 Grades: If you received a Contact Instructor, send me an email. Will work with you. – Let us know if you were misgraded on any assignments • End-of-Chapter Quizzes: – If we finished Chapter 8 then End-of-Chapter Quiz 8 (else, just 7a and 7b) • Paper 1: – Stage 2 due Wednesday before class in CPR • Make sure you have submitted to both CPR and turnitin on eCampus • Honor’s Paper: – Stage 1: Due March 7th. You should have your source materials and be finishing reading them soon Physics We Need Big Bang, Black 41 Holes, No Math Topic 4: Nuclear Physics & Chemistry Full set of Readings So Far •Required: – BBBHNM: Chap 1-9 •Recommended: – BHOT: Chap. 1-6, 9 and 11 (117-122) – SHU: Chap. 1-3, 6 and 7 (upto page 153) – TOE: Chap. 1 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 42 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 43 Clicker Question A star is observed with the following light pattern. Which way is it moving? a) Towards us, slow speed b) Away from us, slow speed c) Towards us, high speed d) Away from us, high speed e) Stationary Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 44 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 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 45 Clicker Question A hydrogen atom is hit by a photon and the electron absorbs the photon and moves to an excited state. Later, a photon with the exact same energy is emitted from the atom, and the electron moves back to its original state. Is this the same photon as before? a) Yes, it was inside the electron b) Yes, it was bouncing around inside the atom c) No, the electron “destroyed” the original photon and created the new photon d) No, the nucleus “destroyed” the original photon and created the new photon Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 46 Clicker Question As far as we know, Dark Matter exists: a) Everywhere in the universe b) Only near black holes c) Mostly in or around galaxies d) It doesn't exist e) We don't know where it Physics We Need Big Bang, Black 47 exists Holes, No Math Topic 4: Nuclear Physics & Chemistry Clicker Question A man shoots a red photon straight up into the air next to a very tall building. The photon rises in the air. Which statements are true: a) The photon slows down as it rises, the same way a rock would b) The photon loses energy, the same way a rock would c) The photon gets blue-shifted Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 48 Clicker Question Instead of throwing a rock into the air, a man shoots a red photon straight up into the air next to a very tall building. The following question are about the photon when it reaches the top of the building. Which of the following statements are true Question 1: Speed a) The speed of the photon stays the same b) The speed of the photon slows down like a rock would Question 2: Energy a) The energy of the photon stays the same b) The energy of the photon gets lower (like the kinetic energy would for a rock) c) The energy of the photon gets larger (since it is getting closer to outer space) Question 3: Color a) The color of the photon stays the same b) The color of the photon becomes more red (gets a longer wavelength) c) The color of the photon becomes more blue (gets a shorter wavelength) Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 49 Clicker Question Two mystery galaxies (on the right) only have a single spectral line in the visible spectrum as shown below. If the above galaxy is stationary, which way is the below galaxy moving? a) Towards us b) Away from us c) It is also stationary d) Not enough information Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 50 Extra Credit • Still offering extra credit for people who find typos in the Textbook • Extra credit for people who find mistakes for any/all eCampus quizzes or CPR assignments • Now offering extra credit for students who send good clicker questions. If it becomes the basis for one used in class I will give you extra credit Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 51 Was due Today – L13 • Reading: – (BBBHNM Unit 2) • Pre-Lecture Reading Questions: – Let us know if you were misgraded – Unit 1 in CPR • You MUST pass this portion to pass the class • Grades on eCampus, Contact me if you haven’t passed yet (additional quizzes needed) • End-of-Chapter Quizzes: – Chapter 7a & 7b quizzes • Paper 1: – (Stage 2 is due Monday before class) – (Text needs to be in turnitin on eCampus) • Honors Paper: – Stage 1 due March 11th Physics We Need Big Bang, Black 52 Holes, No Math Topic 4: Nuclear Physics & Chemistry Prep For Next Time – L6 • Final • Reading: –BBBHNM: All reading through Chapter 10 •Reading Questions: – All reading questions through 10 • eLearning Quizzes: – Chapter 7 • Paper 2: – Calibrations and grading if you didn’t pass Paper 1, due before class on Monday Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 53 Prep for Next Time – L12 • • • • • Reading: – (BBBHNM Unit 2) Pre-Lecture Reading Questions: – Let us know if you were misgraded – Unit 1 Grades Posted in eCampus, contact if needed End-of-Chapter Quizzes: – If we finished Chapter 8 then end-of-chapter quiz 8 (else just up to Chapter 7a & b) Papers: – Paper 1: • Stage 2 is due before class on Monday • (Text needs to be in turnitin on eCampus) – Paper 2: • If we finished Chapter 8, Stage 1 is due Monday before class • Also due in turnitin Honors Paper: – Stage 1 due Wed March 11th Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 54 Prep for Next Time – L13 • • • • • Reading: – (BBBHNM Unit 2) Pre-Lecture Reading Questions: – Let us know if you were misgraded – Unit 1 Grades Posted in eCampus, contact if needed (more quizzes to take) End-of-Chapter Quizzes: – If we finished Chapter 8 then end-of-chapter quiz 8 (else just up to Chapter 7a & b) Papers: – Paper 1: • Stage 2 is due before class on Monday • (Text needs to be in turnitin on eCampus) – Paper 2: • If we finished Chapter 8, Stage 1 is due Monday before class • Also due in turnitin Honors Paper: – Stage 1 due Wed March 11th Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 55 Tentative Due Dates • • • • • • • • Monday March 4th (Today) – Paper 1 revisions due – Paper 2 assigned Monday March 11th – No class, Spring Break. – Want feedback on a Paper 2 draft? Due today in eLearning Monday March 18th – Paper 3 Assigned – Reading for Chap 11 and 12, EOC quizzes for 9 due Tuesday March 19th – Paper 2 Text due in CPR and eLearning (1-day extension) Friday March 22nd • Want feedback on a Paper 2 draft? Due today in eLearning Monday March 25th – Paper 2 Reviews due in CPR Wednesday March 27th – Paper 3 text due in CPR and eLearning (2-day extension) Monday April 1st – Paper 3 Reviews due in CPR Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 56 Prep for Next Time – P11 • Reading: – BBBHNM 9 • Reading questions: – Chapter 9 or the recommended reading • End-of-Chapter Quizzes: – If we finished Chapter 8, end-of-chapter quiz due before next class (else just 7) • Papers: – Paper 1 Resubmissions: • CPR Calibrations due Monday – Start working on Paper 2 • Paper 2 due Monday in CPR/Turnitin.com Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 57 Prep For Next Time – L13 • Note: May change depending on how far we get in lecture • Reading: – BBBHNM: All reading through Chapter 9 • Pre-Lecture Reading Questions: – Through Chapter 9 • End of Chapter Quizzes: – If we finished Chapter 8 then end-of-chapter quiz 8 (else just up to Chapter 7) • Papers: – Paper 0: Was due Friday. Pass/Revise grades will be posted by the end of the night or after all regrades – Paper 0 Revision (if necessary – See eCampus score, not CPR Score): Open now, Text due Monday before class. All Calibrations/Reviews following Monday – Paper 1: Text was due before class. All Calibrations/Reviews due this coming Monday – Paper 2 (if we finished Chapter 8): Due Monday before class. Physics We Need Big Bang, Black 58 Holes, No Math Topic 4: Nuclear Physics & Chemistry Prep for Next Time – P11 • Reading: – BBBHNM 9 • Reading questions: – Chapter 9 or the recommended reading • End-of-Chapter Quizzes: – If we finished Chapter 8, end-ofchapter quiz due before next class (else just 7) • Paper: – If you see problems with the grading of your Paper 1 send us email Physics We Need Big Bang, Black 59 – Work on revision if needed Holes, No Math Topic 4: Nuclear Physics & Chemistry Was due Today – L13 • Reading: – (BBBHNM Unit 2) • Pre-Lecture Reading Questions: – Let us know if you were misgraded – Unit 1 Revision grades posted in eCampus • End-of-Chapter Quizzes: – (Chapter 7a & 7b quizzes) • Papers: – Paper 1, Stage 2: due before class – Paper 2: Will be assigned today • Honors Paper: – Stage 1 due October 19th before class Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 60 Prep for Next Time – P12 • Reading: – BBBHNM 9 • Reading questions: – Chapter 9 or the recommended reading • End-of-Chapter Quizzes: – If we finished Chapter 8, end-of-chapter quiz due before next class (else just 7) • Paper: – If you see problems with the grading of your Paper 1 send us email – Work on revision if needed – Start working on paper 2 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 61 Prep for Today (Is now due) – L11 • Reading: –BBBHNM 8 • End-of-Chapter Quizzes: – Chapters 2-6 • Reading questions: –Two questions from Chapter 8 or recommended reading • Paper 1: –CPR work was due today Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 62 Prep for Today (Is now due) – L12 • Reading: –BBBHNM 9 • End-of-Chapter Quizzes: – Chapter 7 • Reading questions: –Two questions from Chapter 9 • Paper 1: –Working on Revisions if necessary Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 63 Paper 0 Notes • If you believe you were misgraded on Paper 0 let us know ASAP • If you did not pass all the pieces of Paper 0 you need to do a full revision in CPR including calibrations and grading – If you did well on the text, you don’t need to change much • Pass/Revise Grading will be posted on eCampus after we have responded to all the requests for regrades • You need a passing grade on paper 0 to pass Physics We Need Big Bang, Black the course 64 Holes, No Math Topic 4: Nuclear Physics & Chemistry Sad Truth • Every semester we have people who don’t listen to what is said in class and just look at their score on CPR and decide they have passed. • Your score will be on eCampus. Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 65 Protons and Neutrons • A carbon atom has 6 protons (blue) and 6 neutrons (grey) • VERY tightly packed Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 66 Review of a Helium Atom Again look at the stuff as we zoom in http://bigbang.physics.tamu.edu/Figures/StolenAnimations/Animation_Atom.mpg Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 67 Exciting Atoms Atom in Excited State Atom in Ground State Proton Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 68 Excited Atoms Emit Light Atom in Ground State Atom in Excited State Photon with a specific energy Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 69 Analyzing Absorption Spectra • Each element produces a specific set of absorption (and emission) lines • Comparing the relative strengths of these sets of lines, we can study the composition of stars See only spectral lines for known atoms Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 70 Paper Notes • ~600 words (This is the equivalent of both side of a sheet of paper, double spaced) • No citations! Use your own words • Text should be professional. You are “trusted guide” not a “buddy” or “comedian” Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 71 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 72 A “moving” Spectral Line… More Red More Blue Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 73 Light from the Stars A light bulb (or a star) will emit light at all wavelengths and thus produce a continuous spectrum Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 74 What about the Gas Outside a Star? • What will we see if we look at the Gas outside the star? • Light from the star will hit the gas, and we see the light from the gas itself Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 75 The light from excited atoms If the light hits a bunch of low speed atoms (typically call this a gas) at specific wavelengths it can create an emission spectrum Light excites electrons in atoms to higher energy states Transition back to lower states emits light at specific energies (wavelengths) Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 76 When atoms “get in the way” If a continuous spectrum of light passes through atoms, it can create an absorption spectrum Light excites electrons in atoms to higher energy states Wavelengths corresponding to the transition energies are absorbed from thePhysics continuous We spectrum Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 77 The Spectra of Stars Inner parts of a star produces a continuous spectrum Outer parts absorb light at specific wavelengths The light spectrum shows spectral lines! Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 78 Papers for the Course • There will be three papers for the course – http://faculty.physics.tamu.edu/toba ck/109/WritingAssignments/ • Due dates are posted there • Paper 1 will be assigned after we start Chapter 9, due one week after we finish Chapter 9 • You should start thinking about your research paperPhysics topic We Need Big Bang, Black 79 Holes, No Math Topic 4: Nuclear Physics & Chemistry Creating Stable Helium Helium3 Helium3 + Helium3 Helium4 + 2 Protons Nuclear Reaction Proton Helium4 Helium3 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry Proton 80 Writing Assignments 1. Short Assignment 1 is Due Wednesday March 4th before the beginning of Class • Instructions on how to turn it in are on the web 2. Short Assignment 2 is posted • Currently Due Wed March 25 3. Research Paper is posted • Stage 0 due March 30th • Stage 1 due April 13th • Final paper due the last day of class, May 4th Need to be finishing Unit 2 WebCT stuff Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 81 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 82 Making Molecules • H20 picture from Giancoli Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 83 • How atoms combine to form molecules? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 84 Chemistry • How do we make up the different kinds of atoms • Different number of protons and neutrons in the nucleus and electrons • Energy states • Quantum mechanics • Spectral lines. Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 85 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 86 BHOT 11 cont… • Gravity continued… We think of gravity being caused by the exchange of virtual gravitons (not yet confirmed). • Gravity is the weakest of the forces by a lot • Two important things to know: – It acts even at long distances – It is (as far as we know) always attractive • So what, if objects are really far away we might never notice gravity, but if they are really HEAVY then the attraction can be big. • Earth going around the Sun. • Others tend to cancel out. Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 87 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 88 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 89 Uncertainty Principle • Uncertainty Principle determines the size of an atom and a nucleus • DPDX > h Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 90 More so what… • One more particle that we need to talk about, and that’s a photon (“gamma ray”). • A photon is actually light (a gamma ray hits our eyes and that’s how we “see”) • It also turns out that photons also play an important role in atoms • Why do the electrons “orbit” the nucleus? • The protons have positive charge, the neutrons are neutral, and the electrons are negatively charge. • Since positive and negative charges attract each other, the electrons are attracted to the nucleus and that’s what keeps them “in orbit” – Again, the truth is MUCH more complicated than this, but its actually a good understanding… Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 91 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 92 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 93 How do the particles talk to each other? Feynman Diagrams e d W u e Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 94 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 95 Chemistry • We can put nucleons together in lots of different ways… • Each different way corresponds to a different type of atom Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 96 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 97 Quantum Mechanics • Some quick discussions of quantum mechanics (particles and waves, probability, small sizes and big energies) and • What do we do for Quantum mechanics – QM and Gribbins' book? – The great experiments? Two slit? Bohr model? Heated metal? – Also mention to special relativity, general relativity, thermodynamics as applied to stars and blackbody radiation, quantum mechanics, and any other general scientific ideas? Later perhaps? – Need QM for now? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 98 SHU 6 • Anti-matter here? Page 149 • When matter and anti-matter meet they annihilate and disappear in a burst of energy • How could all the matter in the universe exist and be easily detectible if theoretically there should be just as much antimatter around? Either the matter and antimatter should have annihilated each other, or we ought to be able to detect as much antimatter in the universe, which we clearly do not. • Evidence for anti-electrons (positrons) in 1932. • Ends on page 153 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 99 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 100 Questions… • How large are electrons and quarks? – We don’t know… that’s what I (and others) do for a living… • What are they “made of”? Are they made of anything? Strings? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 101 Fundamental Building Blocks • This is a lecture on the fundamental building blocks of nature… • Need a textbook for this… • Charm of Strange Quarks??? • Where is my lecture from Physics 101? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 102 BHOT 11 cont… • Force 2: Electromagnetic force • Most people know about this also, it is what causes the interactions between electrically charge particles that we know and love • Electrons and protons • Electrons and quarks • Ignores electrically neutral particles such as neutrons and neutrinos. Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 103 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 104 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 105 In Class Quiz Answer the following question: Why do we believe that stars are made of atoms? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 106 Looking Forward With an understanding of how to build up nucleons, nuclei, atoms, molecules and matter here on earth we begin to have confidence that we can understand how to build up planets and moons, stars and galaxies in the sky If we can understand how the objects in the universe were formed we have a chance to understand where it all came from Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 107 Yet more remarkable • Want to explain WHY most of the universe is Hydrogen • Its not crazy to think that the reason its mostly hydrogen is because it started out as mostly quarks and just turned into Hydrogen, and not much else because its HARD to form the other stuff Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 108 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 109 Why Do Stars Shine? •Stars are Hydrogen balls •During the reactions of the Hydrogen (protons) creating heavier elements some of the light escapes •This is why stars shine Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 110 Different Types of Nuclei • How do we CREATE different types of nuclei in nature? • Collisions between nuclei allow them to combine • Decay of nuclei allow them to change Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 111 • Video here of photon coming in and exciting an atom then de-exciting… This explains excitations and then spectral lines. • Prism of light coming from Page 54 of BHOT • Jonathan! • Feynman diagram on page 71 of BHOT. Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 112 History • 1816: Spectral lines: von Fraunhofer • Different lines from different atoms • 1880 Huggins: Spectral lines indicate what the chemical elements are Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 113 Chemistry • How do we make up the different kinds of atoms • Different number of protons and neutrons in the nucleus and electrons • Energy states • Quantum mechanics • Spectral lines. Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 114 Fundamental continued • It turns out there are lots of different types of nuclei – This is the domain of nuclear physics • It turns out that a nucleus is actually just a collection of protons and neutrons – Hydrogen: a single proton – Helium: 2 protons and 2 neutrons – Sodium: XX protons and XX neutrons – More on what holds all this together later… – More on what protons and neutrons are made of later (answer for now… quarks) Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 115 Moving towards the fundamental building blocks • What is gas made of? – It turns out its made of molecules of different types – CN, others? • What are molecules made of? – It turns out molecules are made of different types of atoms put together in different ways – Hydrogen, Helium, Sodium, Carbon, Nitrogen etc… Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 116 Spectral lines and Stars • Atoms have excited states… these photons from the surface of the star excites the atom and is absorbed. • Ok… they’re re-emitted later when the atom de-excites, but that goes in a random direction so we don’t see it. Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 117 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 118 Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 119 Summary • Given enough nucleons and time you can eventually make helium • Lots of energy released in the creation process • From Helium and more protons you can make even heavier things… Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 120 Forming Protons Quark qqq Proton Nuclear Reaction Quark Proton Quark Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 121 • The same force holds the nucleons together Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 122 How Atoms Combine • Need this? Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 123 Electron Orbits • Electron orbits in the electron cloud are restricted to very specific radii and energies. r3, E3 r2, E2 r1, E1 • These characteristic electron energies are different for each individual Physics We Need element Big Bang, Black 124 Holes, No Math Topic 4: Nuclear Physics & Chemistry Spectral Lines • Shine white light on a bunch of atoms: • Prism shows the colors in white light going in • After going through the atoms we are left with spectral lines – The excited states absorb and then re-emit in some different direction Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 125 • Note about this video: They change the colors for the last slide!!! • And the colors are screwed up for Helium on the last slide also! Physics We Need Big Bang, Black Holes, No Math Topic 4: Nuclear Physics & Chemistry 126