Big Bang Black Holes No Math ASTRPHYS 109
Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lectures 9, 10 & 11 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 1
Prep For Today (is now due) – L 9 • • • Reading: – BBBHNM Unit 2 (Chapters 5 -9): Was due already – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned Pre-Lecture Reading Questions: – Unit 2 Text Submission: Was due before class • Updated instructions. Please see them before you submit • Submit in e. Campus quiz • Submit ONLY 4 questions, need all 4 to be excellent to pass • Pass/Revise assignment. If you don’t pass we will set up dates for Revisions after you get Feedback – Unit 2 Quiz: Not yet assigned. • Will open up for you in e. Campus AFTER the written submission is graded and only if you get a Pass. Also requires Unit 1 and EOC 3. • Final due date not yet assigned, Will probably assign next time End-of-Chapter Quizzes: – End-of-Chapter Quiz 4: Was due before class today Honors Section: – “Final draft of Stage 0”: Was due before class Physics We Need Bang, 2 – In a. Black heavy reading stage. Need to hear from you at least once every 7 days Big Holes, No Math Topic 1: Light and Doppler Shifts
Prep For Today (is now due) – L 10 • • • Reading: – (BBBHNM Unit 2, Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned Pre-Lecture Reading Questions: – Unit 2 Text Submission: Were already due • Grading still in process • Updated instructions. Please see them before you submit • Submit in e. Campus quiz, Submit ONLY 4 questions, need all 4 to be excellent to pass • Pass/Revise assignment. If you don’t pass we will set up dates for Revisions after you get Feedback – Unit 2 Quiz: Not yet assigned, but you can star as soon as you Pass Text Submission Stage • Will open up for you in e. Campus AFTER the written submission is graded and only if you get a Pass. Also requires Unit 1 and EOC 3. • Final due date not yet assigned, Will probably assign next time End-of-Chapter Quizzes – (Chapter 4) Honors Section: – “Final draft of Stage 0”: Was due already, should be working on Steps 1 and 2 of Stage 1 – In a heavy reading stage. Need to hear from you at least once every 7 days Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 3
Prep For Today (is now due) – L 11 • Reading: – (BBBHNM Unit 2, Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf • e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned, may assign next time • Pre-Lecture Reading Questions: – Unit 2 Text Submission: Due before next class • Most grades posted: 10 = Pass, 5 = Revise • If you didn’t pass, please Revise and Resubmit • Updated instructions. Please see them before you submit, or if you need more than 2 attempts – Unit 2 Quiz: Will likely assign today, probably due before next class • Will only open after you pass the Written stage • End-of-Chapter Quizzes – (Chapter 4) • Honors Section: – “Stage 1, Step 1” due before next class Big Bang, – In a. Black heavy reading stage. Physics Need to We hear Need from you at least once every 7 4 days. Math Topic 1: Light and Doppler Shifts Holes, No
Next Set of Topics: Physics We Need Finished our introduction • Big and small things in the Universe • Evidence and the 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 Physics We Need Big Bang, Black Theory Holes, No Math Topic 1: Light and Doppler Shifts 5
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? Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 6
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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 7
The Topics • Some stuff we need to learn a little 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 • 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… Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 8
Light What we know about the universe comes from multiple places One of the most important is from looking at both outer space and “inner” space Need to know more about the “light we see” Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 9
Outline for Light 1. Light is a wave… 2. …and a particle 3. Light is REALLY fast, but does have a finite speed 4. Doppler effect Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 10
Part 1: Light is a Wave • The light we see is a “wave”, like waves on an ocean • Best described by it’s wavelength Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 11
Why do we believe light is a wave? • Water and Sound are also both waves – Does light behave like water or sound? • Can “see” water waves hitting a wall and what happens to them when they hit two small openings in a wall Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 12
Water waves moving towards a wall You are in the sky looking down at the waves as they go by (Would see the same thing if you drop a rock in some water) Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 13
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 Can measure the wavelength (Physics 208) Physics 202 We & Need Big Bang, Black 14 Holes, No Math Topic 1: Light and Doppler Shifts
The Wavelength of Light • Have also observed that when we shine white light at a prism and it breaks up into its different colors • Each color has a different wavelength which we can also measure Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 15
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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 16
Part 2: Light is a particle • 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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts Very few photons where its dark 17
White Light = Lots of Different Color Photons Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 18
Another view… Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 19
The Energy of Particles We can think about Energy in many ways • One way is the “energy of motion” – Kinetic Energy in the language of PHYS 201 and 206 • For a particle (with mass) in motion: – The higher the speed the particle has, the more energy it has – The more mass the particle has (the heavier it is) the more energy it has Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 20
Clicker Question for Energy Which has more energy? (Which will do more damage to a tree? ) 1. A) A Prius moving at 10 mi/hr or B) An SUV at 10 mi/hr? 2. A) An SUV moving at 10 mi/hr or B) An SUV moving at 60 mi/hr? 3. A) A Prius moving at 60 mi/hr or B) An SUV moving at 10 mi/hr? C) Depends on the masses of the Prius and the SUV Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 21
Photons What do we know about photons? • Photons are a type of fundamental particle – Like an electron or a quark • Higher energy smaller wavelength • Has no mass, but does have energy – Aside for those of you who are interested: It has momentum Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 22
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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 23
Part 3: The Speed of Light “Not just a good idea, it’s the law!” Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 24
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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 25
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 208 299, 792, 458 m/s Physics We Need Big Bang, Black Topic 1: Light and Doppler Shifts Holes, No Math 26
A Light-Year • Some things are so far away that it’s easier to express their distance in light-years – Light travels at 3 x 108 meters/second and there about 3 x 107 seconds/year 16 m in a light-year ~10 Physics We Need Big Bang, Black Holes, No Math Topic 1: Light and Doppler Shifts 27
A Time Machine-Like Viewer • The Sun is 8 light-minutes away, so we are seeing the Sun as it was 8 minutes AGO • 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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 28
Part 4: 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? Big Bang, Black Holes, No Math Physics 221 Physics We Need Topic 1: Light and Doppler Shifts 29
Example with Sound From a Stationary Car The sound we hear is actually a wave – Sound waves Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 30
Now the Car is Moving Things moving away have their waves “stretched” Big Bang, Black Holes, No Math Things coming at us have their waves “scrunched up” Physics We Need Topic 1: Light and Doppler Shifts 31
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 Physics We Need Biggive Bang, the Blackfamous “Eeeeeeee-Yowwwwww” sound Holes, No Math Topic 1: Light and Doppler Shifts 32
What Does This Have to do 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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 33
Doppler Effect and Light Red Shift Sees light with a larger wavelength Big Bang, Black Holes, No Math Galaxy moves to the right Blue Shift Sees light with a smaller wavelength Physics We Need Topic 1: Light and Doppler Shifts 34
Look at Light from Galaxies Big Bang, Black Holes, No Math • 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” Physics We Need Topic 1: Light and Doppler Shifts 35
The Doppler Effect in Action Doppler Effect Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 36
Three Observers What does an object emitting light look like to different observers when it is 1) Not moving 2) Moving Doppler Shift Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 37
Look at some cases Next lets look at two cases where an “explosion” occurs and things move away from that location 1. I stay at the explosion point, but the other stuff goes off into space (I’m at the “center” of the explosion) 2. I’m just one of the things that got blasted into space. I move along with them 1. How would this look to an outside observer? 2. How it would look to me in my reference frame? Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 38
Case 1: Two Objects as they move away from an Explosion (I’m at the explosion site) What it looks like when I’m stationary (or in my reference frame) Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 39
Case 2: Two Objects and Me Moving Away from the Explosion site (seen by someone else) What it looks like when I’m moving relative to the objects Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 40
Case 2: Two Objects and Me Moving Away from the Explosion Site (from my perspective) Why were these cases important? Sorry… you’ll have to wait until we look at galaxies sending us light Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 41
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 1. The color of the light changes 2. The speed of the light does not! Physics We Need Big Bang, Black 42 Holes, No Math Topic 1: Light and Doppler Shifts
Putting It All Together Since stars can be billions of lightyears 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 – More in Chapter 10 (Can also use it to tell us what Stars are made of, but for that we need to learn about quantum mechanics…) Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 43
Lecture on Chapter 5 now complete Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 44
Outline for Unit 2: Physics We Need 1. Light and Doppler Shifts Done 2. Gravity, General Relativity and Dark Matter Next 3. Atomic Physics and Quantum Mechanics 4. Nuclear Physics and Chemistry 5. Temperature and Thermal Equilibrium Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 45
Prep For Next Time – L 9 • • • Reading: – (BBBHNM Unit 2, Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned Pre-Lecture Reading Questions: – Unit 2 Text Submission: Was due before class • Updated instructions. Please see them before you submit • Submit in e. Campus quiz • Submit ONLY 4 questions, need all 4 to be excellent to pass • Pass/Revise assignment. If you don’t pass we will set up dates for Revisions after you get Feedback – Unit 2 Quiz: Not yet assigned, but you can star as soon as you Pass Text Submission Stage • Will open up for you in e. Campus AFTER the written submission is graded and only if you get a Pass. Also requires Unit 1 and EOC 3. • Final due date not yet assigned, Will probably assign next time End-of-Chapter Quizzes – If we finished Chapter 5 then End-of-Chapter Quizzes 5 a & b (else just Chapter 4) before the next class Honors Section: – “Final draft of Stage 0”: Was due before class – In a heavy reading stage. Need to hear from you at least once every 7 days Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 46
Prep For Next Time – L 9 • • • Reading: – (BBBHNM Unit 2, Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned Pre-Lecture Reading Questions: – Unit 2 Text Submission: Was due before class • Updated instructions. Please see them before you submit • Submit in e. Campus quiz • Submit ONLY 4 questions, need all 4 to be excellent to pass • Pass/Revise assignment. If you don’t pass we will set up dates for Revisions after you get Feedback – Unit 2 Quiz: Not yet assigned, but you can star as soon as you Pass Text Submission Stage • Will open up for you in e. Campus AFTER the written submission is graded and only if you get a Pass. Also requires Unit 1 and EOC 3. • Final due date not yet assigned, Will probably assign next time End-of-Chapter Quizzes – (Chapter 4) Honors Section: – “Final draft of Stage 0”: Was due before class – In a heavy reading stage. Need to hear from you at least once every 7 days Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 47
Prep For Next Time – L 10 • • • Reading: – (BBBHNM Unit 2, Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned Pre-Lecture Reading Questions: – Unit 2 Text Submission: Were already due • Grading still in process • Updated instructions. Please see them before you submit • Submit in e. Campus quiz, Submit ONLY 4 questions, need all 4 to be excellent to pass • Pass/Revise assignment. If you don’t pass we will set up dates for Revisions after you get Feedback – Unit 2 Quiz: Not yet assigned, but you can star as soon as you Pass Text Submission Stage • Will open up for you in e. Campus AFTER the written submission is graded and only if you get a Pass. Also requires Unit 1 and EOC 3. • Final due date not yet assigned, Will probably assign next time End-of-Chapter Quizzes – If we finished Chapter 5 then End-of-Chapter Quizzes 5 a & b (else just Chapter 4) before the next class Honors Section: – “Final draft of Stage 0”: Was due already, should be working on Steps 1 and 2 of Stage 1 – In a heavy reading stage. Need to hear from you at least once every 7 days Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 48
Prep For Next Time – L 10 • • • Reading: – (BBBHNM Unit 2, Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned Pre-Lecture Reading Questions: – Unit 2 Text Submission: Were already due • Grading still in process • Updated instructions. Please see them before you submit • Submit in e. Campus quiz, Submit ONLY 4 questions, need all 4 to be excellent to pass • Pass/Revise assignment. If you don’t pass we will set up dates for Revisions after you get Feedback – Unit 2 Quiz: Not yet assigned, but you can star as soon as you Pass Text Submission Stage • Will open up for you in e. Campus AFTER the written submission is graded and only if you get a Pass. Also requires Unit 1 and EOC 3. • Final due date not yet assigned, Will probably assign next time End-of-Chapter Quizzes – (Chapter 4) Honors Section: – “Final draft of Stage 0”: Was due already, should be working on Steps 1 and 2 of Stage 1 – In a heavy reading stage. Need to hear from you at least once every 7 days Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 49
Prep For Next Time – L 11 • • • Reading: – (BBBHNM Unit 2, Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned, may assign next time Pre-Lecture Reading Questions: – Unit 2 Text Submission: Due before next class • Most grades posted: 10 = Pass, 5 = Revise • If you didn’t pass, please Revise and Resubmit • Updated instructions. Please see them before you submit, or if you need more than 2 attempts – Unit 2 Quiz: Due before next class • Will only open after you pass the Written stage End-of-Chapter Quizzes – If we finished Chapter 5 then End-of-Chapter Quizzes 5 a & b (else just Chapter 4) Honors Section: – “Stage 1, Step ” due before next class – In a heavy reading stage. Need to hear from you at least once every 7 days Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 50
Prep For Next Time – L 11 • • • Reading: – (BBBHNM Unit 2, Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf e. Campus Stuff – Warm-up Quiz Part 4 (Peerceptiv): Not yet assigned, may assign next time Pre-Lecture Reading Questions: – Unit 2 Text Submission: Due before next class • Most grades posted: 10 = Pass, 5 = Revise • If you didn’t pass, please Revise and Resubmit • Updated instructions. Please see them before you submit, or if you need more than 2 attempts – Unit 2 Quiz: Due before next class • Will only open after you pass the Written stage End-of-Chapter Quizzes – End-of-Chapter Quizzes 5 a & b Honors Section: – “Stage 1, Step 1” due before next class – In a heavy reading stage. Need to hear from you at least once every 7 days Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 51
Prep For Next Time – LX • • • i. Clicker: – Make sure to register by clicking on the link in e. Campus (will be in the Home area) Reading: – (BBBHNM Unit 2/Chapters 5 -9) – Recommended Reading: • See P 3 of http: //people. physics. tamu. edu/toback/109/Syllabus. pdf Warmup Quizzes: – Warm-up Quiz Part 4 (Peerceptiv): Postponed - Will assign soon Pre-Lecture Reading Questions: – Unit 2 Text Submission: Was due already • Pass/Revise assignment: – Most grades posted: 10 = Pass, 5 = Revise – If you don’t pass post 4 questions (can re-use excellent ones) to “PLRQ Unit 2 Revision”. If you don’t pass a second time, submit to “PLRQ Unit 2 – Revision 2” – Final due dates will be assigned soon. we will set up dates for Revisions after you get Feedback – Unit 2 Quiz: Will open up for you in e. Campus AFTER they are graded and you get a Pass. Also requires Unit 1 and EOC 3. Final due date not yet assigned End-of-Chapter Quizzes – If we finished Chapter 5 then End-of-Chapter Quizzes 5 a & b (else just Chapter 4) Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 52
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Clicker Quiz Which of the following travels the fastest? A. Radio waves B. Gamma rays C. Red light D. Blue light E. They all move at Physics We Need Big Bang, Black the same speed Topic 1: Light and Doppler Shifts Holes, No Math 54
Clicker Quiz We observe two objects in space. From other studies, we can tell that object X is emitting Infrared Light and the Object Y is emitting Ultraviolet Light. We observe the color of Object X to be Red and the color of Object Y to be Blue. Which statement is true? a) X and Y are moving towards us b) X and Y are moving away from us c) X is moving towards us and Y is moving away from us d) X is moving away from us and Y is moving towards us Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 55
Why do we believe light is a wave? • How do waves Waves move this way 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 Big Bang, Black Holes, No Math Big Waves Here Small Waves Here Physics We Need 56 Topic 1: Light and Doppler Shifts
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 Big Bang, Black Holes, No Math LOTS of photons A few photons Lots of photons Physics We Need 57 Topic 1: Light and Doppler Shifts
In-Class Writing Assignment Write down, during the course of lecture, Two questions you want to know the answer to Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 58
Reading Full reading so far: • BBBHNM: Chap 1 -6 • Prelude • BHOT: Chap. 1 -6, 9 and 11 (117 -122) • SHU: Chap. 1 -3, 6, 7 (up-topage 153) • TOE: Chap. 1 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 59
Before we start the next topic • Don’t forget to take your e. Learning quizzes – Can’t pass the course without getting 100% on all of them • Make sure your name and DATE are on EVERYTHING you turn in Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 60
How do we answer these questions? As previously discussed we have two avenues: • Theory • Experiment What do both have to say about Light? Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 61
Light as a Wave Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 62
Quiz • What time is lecture on Wednesday? • Where are we meeting? – Name – Today’s date Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 63
Before we begin • As a special treat the class will attend a special Department of Physics colloquium on the LHC this Wednesday (Sept 17 th) • Class will start at 4 PM in the teaching wing of the Engineering/Physics building, room 202 (big class room) • Class will be over by 5 PM • You will be expected to sign in with me or Mike as your in class quiz Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 64
Light is more than the colors we see X-rays Ultraviolet Visible Microwaves color Infrared Radio Waves Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 65
In-Class Writing Assignment Write down, during the course of lecture Two questions you want to know the answer to Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 66
Web. CT • It has come to my attention that people are not finishing the quizzes in Web. CT • If they don’t get finished we will start requiring people to do them in Recitation to help enforce that they are done – You should be done with Quizzes 1 -3 now – Done with Quizzes 4 -6 by the end of next week Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 67
A Different Example It is as if a traveling salesman were to send a letter home once a week during his travels • While he is traveling away from home, each successive letter will have a little farther to go than the one the week before Letters will arrive a little more than a week apart • On the way home each successive letter will have a shortest distance to travel will arrive more frequently than once a week Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 68
Old beliefs • Light is so fast that people used to believe that it was simply instantaneous • You can measure the speed of sound pretty easily – Listen to the alumni side at a football game. When they sing, they’re always LATE! • Couldn’t answer the question with an experiment until 1600’s Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 69
Why do we believe it has a finite speed? • Danish Astronomer Ole Christian Roemer in 1676 • Moons of Jupiter are helpful again! • Look at the eclipses of the moons of Jupiter as it moves towards us and away from us Big Bang, Black Holes, No Math We can measure this really accurately now, but that’s another story… Physics We Need Topic 1: Light and Doppler Shifts 70
Eclipses of the Jupiter’s Moon Now you see it! Now you don’t! Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 71
Measure the Time Between Eclipses • When Jupiter is moving towards us we get shorter times between eclipses • When Jupiter is moving away from us we get longer times between eclipses Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 72
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Announcements • Recitation tomorrow in ENPH 210 • No office hours today – Call/email if you need to meet • Web. CT Quizzez Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 74
Light: Wave and Particle Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 75
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• Stars can be billions of light years away! • Binary system: SHU p 68 • Had a way of measuring both the direction and speed of travel of every source of light in the night sky Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 77
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• However, in reality they are separate particles (feynman diagram? ) and each photon interacts with an atom individually. Again a diagram? • Individual interacting with an atom (Figure here) Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 80
• Question: How do we measure the distance to Jupiter? Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 81
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Doppler and Light • Galaxies moving. Effect towards us have shorter wavelength light • The light is more Blue, or shifted to the Blue side of the light spectrum • “Blue Shifted” • Galaxies moving away from us have longer wavelength light • The light is more Red, or shifted to the Red side of the Replace with P 65 from SHU light spectrum • “Red Shifted”Physics We Need Big Bang, Black Holes, No Math Topic 1: Light and Doppler Shifts 83
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• We know the Doppler effect in sound… Both volume and pitch change. Picture SHU p 65 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 86
Why do we believe light is a wave? • Shine white light at a prism and it breaks up into its different colors • These different colors are waves with different wavelengths Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 87
Light is a wave The light we see is a “wave” and it is best described by it’s wavelength Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 88
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Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 92
• This is a test Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 93
For People in the Honors Section Stage 0 (not in CPR): th Due Monday Sept 26 For details see http: //people. physics. tamu. edu/toback/109/Honors/ Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 94
Unit 1 and Later Units PLRQ Unit 1 in CPR is different than the others since we want to make sure you get good at CPR • It is Pass/Revise • You must pass ALL four parts separately, just a 70% overall score is NOT good enough. You will need: – >70% on the overall score – >35/50 on the text portion of your paper – >14/20 on the calibration portion – >14/20 on the reviews – >7/10 on the self-assessment • I’ll post the grades in e. Campus • If you don’t pass the first time, you will have to do a Revision Assignment (all the parts) until you pass • Later units are just your combined score for all parts – You can do a revision if you want to get a better grade – We will average the two scores Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 95
PLRQ Unit 1 Grades • Criteria for Pass/Revise grades for CPR Unit 1 are described in the FAQ (http: //people. physics. tamu. edu/toback/109 FAQ. shtml#CPRGrades) • Send an email to 109 help@physics. tamu. edu if you think you were misgraded or we gave you the wrong grade • Will post the grades in e. Campus after we are done with re-grade requests • You should go to e. Campus to make sure you got the grade you think you did. Many people are surprised. • What do you do if your e. Campus grade says “Revise”? – http: //people. physics. tamu. edu/toback/109 FAQ. shtml#Requirements Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 96
Paper 0, Questions 1 -5 1. 2. 3. 4. 5. Does the paper make it easy to understand what question is being answered, what the answer is, and how it will be answered? If anyone of those are missing, or if you can't follow the argument, then choose No. If the argument is clear, but not said very well (or is wordy), then you should still give a Yes. If the paper is clear to you, but would not be clear to someone who hasn’t taken the course choose No. Being easy to read isn't a good enough reason to give a Yes. Having a sentence or two that are hard to understand (or poorly written) within a basically clear paper is fine, and can still deserve a Yes if it is otherwise ok. Are the pieces of evidence clearly and correctly enumerated in the opening paragraph? This includes the electrons going around atoms, the Moon orbiting the Earth, and planets orbiting the Sun. Does the structure of the paper follow the instructions? Specifically: Is there an introduction paragraph, separate paragraphs discussing evidence, and a conclusion paragraph? If any are missing, choose No. Does the paper directly address the question and make the argument to answer it? If the paper addresses the question and makes an argument (right or wrong) to answer it, choose Yes (we will address the wrongness in a later question). Do not choose No due to a poorly written or confusing introduction. The paper does not need to have only three paragraphs, and the pieces of evidence can be intertwined within them. Do not choose No due to missing evidence or more than three paragraphs. Do not choose No just because evidence is not constrained to these paragraphs. If the paper does not end with a conclusion paragraph, choose No. Do not choose No due to a poorly written or confusing conclusion. Is the paper generally free of extraneous evidence? If there is any significant evidence that is off topic or an argument that has nothing to do with the topic, choose “No. ” If there is significant evidence from outside class, choose No. Do not choose “No” due to evidence that is unnecessary if the evidence is relevant to the topic. Does the paper only use language and words that can be understood by the average lay-person? If the author uses an acronym, like GR, for general relativity that is ok but only if the acronym is clearly defined. If they use an acronym that isn't defined, then select No. Similarly, just because you saw these words in a high-school science class does not mean they are understood by the average person. The average person on the street would know what an atom is, but not know what a spectral line is. Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 97
Paper 0, Questions 6 -10 6. Does the essay use language formal enough to give to a statesman? If the paper uses jokes, slang or other informal language, choose No. Do not choose No due to poor grammar, spelling mistakes, incomplete sentences, or poor sentence structure (we will take off points in a different question for this). Do not choose No due to the use of an acronym, like USA, since it is common usage and not slang. 7. Is the essay generally free of instances of bad grammar, incomplete sentences or spelling mistakes? If there are more than two minor mistakes, choose No. 8. Does the paper make clear how and why the evidence presented relates to the argument? If the facts are mentioned but show no clear connection to the argument, then choose No. If the facts are not addressed throughout the paper, then choose No. If it states the data without saying why it is evidence then choose No. 9. Do the middle (evidence) paragraphs clearly tie into the overall structure? 10. Does the paper use the scientific method and evidence based decision making? It’s OK if the words “scientific method” and “evidence-based Physics We Need Big Bang, Black 98 decision making” are not mentioned specifically. Holes, No Math Topic 1: Light and Doppler Shifts
Paper 0, Questions 11 -15 11. Does the essay make it clear what the Scientific Method is and why it is important in this paper? 12. Does the essay clearly tie together the pieces of evidence using the scientific method in the conclusion? 13. Does this paper say that the Moon orbits the Earth? 14. Does the paper mention explicitly that the Earth is much more massive than the Moon, and that it is important to why the Moon orbits the Earth instead of the other way around? If it mentions that the Earth is more massive, and that this is what is important, then this is good enough. If it just says that it is more massive without saying why that is important in some way, then answer No. If it says "bigger" or "larger" (or that the Moon is "smaller") that is good enough. 15. Does the paper mention that the Earth or the planets orbit the Sun? Either is fine. If neither is mentioned, then give a No. Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 99
Paper 0, Questions 16 -20 16. Does the paper mention explicitly that the Sun is much more massive than the things orbiting it, and that it is important to say why they orbit the Sun instead of the other way around? If it mentions that the Sun is more massive, and that this is what is important, then this is good enough. If it just says that it is more massive without saying why that is important in some way, then answer No. If it says "bigger" or "larger" (or that the planets are "smaller") that is good enough. 17. Does the paper mention that electrons orbit protons or that electrons orbit a nucleus? Either one is fine. 18. Does the paper mention explicitly that the proton (or nucleus) is much more massive than the electron orbiting it, and that it is important to why they orbit the proton (or nucleus) instead of the other way around? If it mentions that the proton or nucleus is more massive, and that this is what is important, then this is good enough. If it just says that it is more massive without saying why that is important in some way, then answer No. If it says "bigger" or "larger" (or that the electron is "smaller") that is good enough. 19. Does the essay spend an appropriate amount of time on each topic? 20. Does the conclusion paragraph tie together all the big picture issues discussed in the other paragraphs? If the conclusion does not summarize the evidence, then chose No. If the conclusion simply re-states the pieces of evidence, then Physics We Need Big Bang, choose Black No. 100 Holes, No Math Topic 1: Light and Doppler Shifts
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