Transcript Slide 1

Big Bang, Black Holes, No Math ASTR/PHYS 109 Dr. David Toback Lecture 7 & 8

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 1

Prep For Today (is now due) – L7

Reading: BBBHNM Unit 2Pre-Lecture Reading QuestionseCampus quizzes (all 6)Unit 1 Revision (if needed): Stage 1

due date postponed until Monday

Let us know if you were misgradedUnit 2: Stage 1End-of-Chapter QuizzesChapter 4

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 2

Prep For Today (is now due) – L8

Reading: (BBBHNM Unit 2)Pre-Lecture Reading QuestionseCampus quizzes (all 6)Many of you need to check theseUnit 1 Revision (if needed): Stage 1Let us know if you were misgradedUnit 2: Stage 2End-of-Chapter Quizzes(Chapter 4)

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 3

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 Theory Holes, No Math Topic 1: Light and Doppler Shifts 4

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 5

The Topics

Some stuff we need 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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 6

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 7

Light

What we know about 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 8

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 9

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 10

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

Water waves moving towards a wall

You are in the sky looking down at the waves as they go by Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 12

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 Big Bang, Black Holes, No Math (Physics 202 & 208) 13

The Wavelength of Light

Shine white

light at a prism and it breaks up into its different colors

Each color

has a different wavelength which we can measure Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 14

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 15

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

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts Lots of photons where its bright Very few photons where its dark

White Light = Lots of Different Color Photons Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 17

Another view…

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 18

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 218

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 19

Clicker Question for Energy

Which has more energy? (Which will do more damage to a tree?) 1. A) A Prius moving at 10mi/hr or B) An SUV at 10mi/hr?

2. A) An SUV moving at 10mi/hr or B) An SUV moving with 60mi/hr?

3. A) A Prius moving at 60mi/hr or B) An SUV moving at 10mi/hr?

C) Depends on the masses of the Prius and the SUV

Big Bang, Black Holes, No Math Topic 1: Light and Doppler Shifts 20

Photons

What do we know about photons?

Photons are a type of particleLike an electron or protonHigher energy

smaller wavelength

Has no mass, but does have energyAside 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 21

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 22

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 23

Light has a Finite Speed

Light has been measured to have a specific speed

3 x 10

8

meters per second

186,000 miles per second1 foot per nanosecondReally FASTThe fastest speed allowed

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 24

Maxwell’s Theory

Maxwell and others wave and calculated its expected speed

Gave the observed

speed of light!

theories were correct

We can now measure

incredible precision Physics 208 2.99792458 x 10 8 Big Bang, Black Holes, No Math m/s Topic 1: Light and Doppler Shifts 25

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 10

are

p

x 10

7 8

meters/second and there seconds/year

~10

16

m in a light-year

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 26

Time Machine

The Sun is 8 light-minutes away, so we

are seeing the Sun as it was 8 minute 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 27

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 28

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 29

Now the Car is Moving

Things moving away have their waves “stretched” Things coming at us have their waves “scrunched up” Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 30

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 give the famous “Eeeeeeee-Yowwwwww” sound 31

What Does This Have to 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 32

Doppler Effect and Light

Red Shift

Sees light with a

larger

wavelength Galaxy moves to the right

Blue Shift

Sees light with a

smaller

wavelength Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 33

Look at Light from Galaxies

Big Bang, Black Holes, No Math

The light from galaxies

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”

Topic 1: Light and Doppler Shifts 34

The Doppler Effect in Action

Doppler Effect

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 35

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 36

Look at some cases

Next lets look at three cases where an “explosion” occurs and things expand from that point 1. I’m stationary and the exploding things are moving away from me (I’m the center of the explosion) 2. I’m moving along with the exploding things 3. Same as case 2, but 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 37

Two Objects Moving Away from Me

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 38

Two Objects Moving Away From Me

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 39

Same Thing: My Reference Frame

Why were these three cases important?

Sorry… you’ll have to wait until we Big Bang, Black Holes, No Math 40

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

c o l o r

of the light changes 2.The speed of the light does not!

Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 41

Putting It All Together

Since stars can be billions of light years 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 (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 42

Outline for Unit 2: Physics We Need 1. Light and Doppler Shifts

Done 2. Gravity, General Relativity and Dark Matter Mechanics Equilibrium

Next 3. Atomic Physics and Quantum 4. Nuclear Physics and Chemistry 5. Temperature and Thermal Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 43

Prep For Next Time – L7

Reading:(BBBHNM Unit 2)Pre-Lecture Reading QuestionseCampus quizzes (all 6)Unit 1 Revision (if needed): Stage 1 Let us know if you were misgradedUnit 2: Stage 2End-of-Chapter QuizzesIf we finished Chapter 5 then End-

of-Chapter Quiz 5 (else just Chapter 4) Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 44

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 45

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 (10 ever smaller -19 m) d) Undisturbed, it can go on living forever and e) They don't appear to be made of anything Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 46

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 the same speed 47

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 the light 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 48

Paper 0, Questions 1-5

1. 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.

2. 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.

3. 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. 4. 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.

5. 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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 49

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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 50

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 51

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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 52

Prep For Next Time – L6

Reading:Required: BBBHNM Unit 2Recommended Reading:See P3 of

http://people.physics.tamu.edu/toback/109/Syllabus.pdf

Pre-Lecture Reading QuestionsUnit 1 Revision (if Needed): Stage 2 in CPR due

Monday before class

Unit 2: Stage 2 due Monday before classEnd-of-Chapter QuizzesIf we finished Chapter 5 then End-of-Chapter

Quiz 5 (else, just through Chapter 4) Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 53

Prep For Next Time – L7

Reading:Required: BBBHNM Unit 2Recommended Reading:See P3 of

http://people.physics.tamu.edu/toback/109/Syllabus.pdf

Pre-Lecture Reading QuestionsUnit 1 Revision: Let me know if you were

misgraded

Unit 2: Let me know if you were misgradedUnit 2 Revision (if desired): Stage 1 due Monday

before class

End-of-Chapter QuizzesIf we finished Chapter 5 then End-of-Chapter

Quiz 5 (else, just through Chapter 4) Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 54

Was due today – L7

Reading:BBBHNM: All reading through Chapter 6Pre-Lecture Reading Questions:All reading questions through Chapter 6End-of-Chapter Quizzes:All end-of-chapter quizzes through 4Papers:Should have been working on Paper 0Read the “Writing Prompt” and other

stuff on CPR Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 55

Paper 1 Stuff

I have extended the due date until Friday at

5:45PM

Want feedback before turning it in? Post it in eLearning in .doc (or .pdf) for

comments by the TA by 5PM tomorrow

Make sure you polish itIf you have lots of grammar and spelling

mistakes we’ll just make you resubmit it

Will be due in CPR and turnitin.com in one

week Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 56

Prep for Next Time – L6

Reading: BBBHNM 6Recommended: BHOT 4-6Reading questionsTwo questions from Chapter 6 or the

recommended reading

End-of-Chapter QuizzesIf we finished Chapter 5 then end-of-

chapter quiz 5 (else just 4)

Be working on Paper 1

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 57

Prep for Next Time – L7

Reading: NoneReading questionsNone End-of-Chapter QuizzesIf we finished Chapter 5 then end-of-

chapter quiz 5 (else just 4)

Paper 1Phase II is due Friday at 5:45PM

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 58

Prep For Next Time – L6

Note: May change depending on how far we get in ReadingBBBHNM: NoneReading Questions:NoneEnd-of-Chapter QuizzesIf we finished Chapter 5 then end-of-chapter

quiz 5 (else just up to Chapter 4)

Paper StuffPaper 0 in CPR and turnitin.com before classWill talk more about Calibrations next time

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 59

Prep For Next Time – L7

Note: May change depending on how far we get in ReadingBBBHNM: NoneReading Questions:NoneEnd-of-Chapter QuizzesIf we finished Chapter 5 then end-of-chapter

quiz 5 (else just up to Chapter 4)

Paper StuffPaper 0 in CPR and turnitin.com before classWill talk more about Calibrations next time

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 60

Full set of Readings So Far

Required:BBBHNM: Chap 1-

6

Recommended:BHOT: Chap. 1-

6

SHU: Chap. 1-

3

TOE: Chap. 1

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 61

Prep for Today (is due now) – L6

Reading:BBBHNM: Chap 5Reading Questions:Two questions from Chapter 5

or the recommended reading

End-of-Chapter QuizzesChapter 4

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 62

Prep for Today (is due now) – L7

Reading:BBBHNM: Chap 6Reading Questions:Two questions from Chapter 6 or the

recommended reading

End-of-Chapter QuizzesChapter 4Paper 1Phase I (CPR and turnitin) was due FridayPhase II (Calibrations) due Friday at 5:45

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 63

Why do we believe light is a wave?

How do waves

behave?

Water waves and

Sound waves

Can “see” water

waves hitting a wall and what when they hit wall Big Bang, Black Holes, No Math Waves move this way happens to them two small openings in a Big Waves Here Small Waves Here Physics We Need Topic 1: Light and Doppler Shifts 64

Phase I, Phase II and Phase III

Phase I: (Paper due 1 week after we finish Chapter 4)

Turn in a polished draft to eLearningTA’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 CPRWhen you submit to CPR (after revision), you will need

to also submit a copy of your to the turnitin.com line on eLearning Phase III: (Due one week after Phase II)

Calibrations and Reviewing due one week after you

submit Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 65

eLearning Quizzes – L8

You are expected to be working on You cannot pass this course without

having gotten a perfect score on all of them

You make take as many of each

quiz as you like to get perfect scores without penalty

Due before the class AFTER we

finish a chapter Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 66

In-Class Quizzes

Turn in your two questions on the

reading

During class you will write down two

more

This is a separate quizIf you didn’t get a grade you

wanted on one of the first few reading quizzes see me about trying again Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 67

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 Lots of photons Physics We Need Topic 1: Light and Doppler Shifts A few photons 68

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 69

Reading

Full reading so far:

BBBHNM: Chap 1-6PreludeBHOT: Chap. 1-6, 9 and 11

(117-122)

SHU: Chap. 1-3, 6, 7 (up-to-

page 153)

TOE: Chap. 1

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 70

Before we start the next topic

Don’t forget to take your

eLearning 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 71

How do we answer these questions?

As previously discussed we have two avenues:

TheoryExperiment

What do both have to say about Light?

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 72

Light as a Wave

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 73

Quiz

What time is lecture on

Wednesday?

Where are we meeting?NameToday’s date

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 74

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 4PM in the teaching

wing of the Engineering/Physics building, room 202 (big class room)

Class will be over by 5PMYou 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 75

Light is more than the colors we see X-rays Ultraviolet Visible

c o l o r

Microwaves Infrared Radio Waves Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 76

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 77

WebCT

It has come to my attention that people

are not finishing the quizzes in WebCT

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 78

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

a week

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 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 79

Old beliefs

Light is so fast that people used to

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 80

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 81

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 82

Measure the Time Between Eclipses

When Jupiter is

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 83

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 84

Announcements

Recitation tomorrow in ENPH

210

No office hours todayCall/email if you need to meetWebCT Quizzez

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 85

Light: Wave and Particle

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 86

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 87

Stars can be billions of light

years away!

Binary system: SHU p68Had 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 88

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 89

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 90

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 91

Question: How do we measure

the distance to Jupiter?

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 92

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 93

Doppler Effect and Light

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 “Red Shifted”

Big Bang, Black Holes, No Math Replace with P65 from SHU Physics We Need Topic 1: Light and Doppler Shifts 94

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 95

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 96

We know the Doppler effect in

sound… Both volume and pitch change. Picture SHU p65 Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 97

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 98

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 99

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 100

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 101

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 102

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 103

This is a test

Big Bang, Black Holes, No Math Physics We Need Topic 1: Light and Doppler Shifts 104