Learner Centered Astronomy A Teaching Excellence Workshop Ed Prather and Gina Brissenden University...

Learner Centered Astronomy A Teaching Excellence Workshop

Ed Prather and Gina Brissenden

University of ArizonaCenter for Astronomy Education

Sponsored by the NASA Navigator Public Engagement Programs

http://astronomy101.jpl.nasa.gov

What Can I do Besides Lecture to Engage Students in their Learning?

• Ask students questions (not all questions are equal). Use demonstrations (interactive lecture demos)

• Surprise quizzes (graded/ungraded)

• In-class writing (with/without discussion)- muddiest point- summary of today's main points- 5-minute free writing

• Think-Pair-Share (Peer Instruction-ConcepTests)

• Small Group Interactions

• Student Debates (individual/group)

• Whole Class Discussions

• Jigsawing

Let's Try an In-Class Small Group Activity

Lecture-Tutorials for Introductory AstronomyPrather, Slater, Adams and Brissenden

(2nd edition 2007)

How Research on Student Beliefs and Reasoning Difficulties are used to

Promote a Learner-Centered Introductory Astronomy

Classroom

Are you really teaching if your students are not

learning?

Another talk about the teaching and learning…..

“I’ve seen it performed many times, but I can’t remember ever sleeping through it so peacefully.”

How often do you hear the following from your students?

• I just can’t do science!• I just can’t do math!• I understand your lectures and the readings, but I

can’t do the homework.• I did all of the homework three times, but I can’t do

well on your tests.• I just can’t do history!

From a teaching and learning perspective, just what is it that makes astronomy different?

Astronomy Diagnostics Test (ADT)

If you could see stars during the day, this is what the sky would look like at noon on a given day. The Sun is near the stars of the constellation Gemini. Near which constellation would you expect the Sun to be located at sunset?

A) Leo C) Gemini E) Pisces

B) Cancer D) Taurus

11% 73%

South West East

Cancer

Gemini

Taurus

Pisces

OOPS!!

BUT I AM A GREAT TEACHER!!!!

The Real Situation- from How People Learn

“Students enter your lecture hall with preconceptions about how the world works. If their initial understanding is not engaged, they may fail to grasp the new concepts and information that are taught, or they may learn them for the purposes of a test but revert to their preconceptions outside the classroom”

HOW PEOPLE LEARN, National Research Council,

National Academy Press, 2000.

From How People Learn

“Humans are viewed as goal-directed agents who actively seek information. They come to formal education with a range of prior knowledge, skills, beliefs, and concepts that significantly influence what they notice about the environment and how they organize and interpret it. This, in turn, affects their abilities to remember, reason, solve problems, and acquire new knowledge. … If students’ initial ideas and beliefs are ignored, the understandings that they develop can be very different from what the teacher intends.”

HOW PEOPLE LEARN, National Research Council,

National Academy Press, 2000.

• Students enter the classroom with preconceptions about how the world works. If their initial understanding is not fully engaged, they may fail to grasp new concepts in meaningful ways that last beyond the purposes of an exam.

• To fully develop competence, students must: (1) have a deep foundation of factual knowledge, (2) understand interrelationships among facts and concepts and (3) organize knowledge in ways that facilitate retrieval and application

• A “metacognitive” approach to instruction can help students learn to take control of their own learning and monitor progress.

How People Learn: Brain, Mind, Experience, and School (Expanded Edition),National Research Council, National Academy Press, 2000.

How People Learn

Key results from research into education and cognition

1. Learning is productive / constructive - learning requires mental effort

2. Knowledge is associative / linked to prior mental models and cognitive structures

3. The cognitive response is context dependent – what and how you learn depends on the educational setting

4. Most people require some social interactions in order to learn deeply and effectively

• The introductory course for non-science majors could be significantly improved

• Although the lecture approach is largely insufficient, there are instructional strategies available to accompany lecture that intellectually engage students

• Large enrollment courses can use learner-centered instructional strategies

• Awareness of and exposure to active learning techniques will motivate faculty to try them

Our Assumptions

Active Learning

• Active learning is when students take active responsibility for participating in and monitoring of their own learning by engaging in critical reasoning about the ideas presented in the class.

A Commonly Held Inaccurate Model of a Student’s Conceptual Framework

A Commonly Held Inaccurate Model of Teaching and Learning

So What Can You Do About It?

• Lecture more loudly?

Assumption #1 - Lecture is ineffective at promoting deep conceptual change.

• This was NOT a traditional case study that had a control group and used two treatments with a randomized population of participants

• Population – students enrolled in the introductory astronomy course for non-science majors

• Instrument used: A 68 items research based multiple choice questionnaire

• Pre-Course: two forms, A&B, which each contained a subset of questions

• Post-Lecture: questions administered in subsets that directly reflected topic of lecture

Celestial Motion of Objects

You observe a star rising directly to the east. When this star reaches its highest position above the horizon, where will it be?

a) high in the northern sky b) high in the eastern sky c) high in the southern sky d) high in the western sky e) directly overhead

• Before Lecture (N=42): 2% correct

The diagram below shows Earth and the Sun as well as five different possible positions for the Moon. Which position of the Moon best corresponds with the phase of the Moon shown in the figure at the right?

NOT TO SCALE

Orbit of the Moon

What Causes Moon Phases

NOT TO SCALE

Orbit of the Moon

The graph below shows the blackbody spectra for three different stars. Which of the stars is at the highest temperature?

a) Star A

b) Star B

c) Star C Star C

Star B

Star A

Wavelength

Blackbody Radiation LT

The graph at right shows the blackbody spectra for three different stars. Which of the stars is at the highest temperature?

a) Star A

b) Star B

c) Star CStar C

Star B

Star A

Wavelength

H-R Diagrams and Spectral Class

A red giant of spectral type K9 and a red main sequence star of the same spectral type have the same

a) luminosity.

b) temperature.

c) absolute magnitude.

a) luminosity.

b) temperature.

If our universe is expanding, what are the implications for the separation between two stars within our galaxy?

a) The two stars are moving farther apart. b) The two stars are moving closer together. c) The two stars are remaining approximately the

same distance apart.

Expansion of the Universe

Looking at Distant ObjectsImagine that you simultaneously receive the satellite transmission of two pictures of two people that live on planets orbiting two different stars. Each image shows the people at their 21st birthday parties. Consider the following possible interpretations that could be made from your observations. Which do you think is the most plausible interpretation?

a) Both people are the same age but at different distances from you.b) The people are actually different ages but at the same distance from you.c) The person that is closer to you is actually the older of the two people.d) The person that is farther from you is actually the older of the two people.

Looking at Distant Objects

Imagine that you simultaneously receive the satellite transmission of two pictures of two people that live on planets orbiting two different stars. Each image shows the people at their 21st birthday parties. Consider the following possible interpretations that could be made from your observations. Which do you think is the most plausible interpretation?

Pre-Course mean: 30% (nA=39,nB=42)

• Lecture more loudly?

Funky Winkerbean

BY TOM BATIUK

• After Lecture (N = 135): 19% correct

NOT TO SCALE

Orbit of the Moon

NOT TO SCALE

Orbit of the Moon

• After Lecture (N=127): 53% correct

a) Star A

b) Star B

c) Star CStar C

Star B

Star A

Wavelength

a) Star A

b) Star B

c) Star CStar C

Star B

Star A

Wavelength

a) luminosity.

b) temperature.

a) luminosity.

b) temperature.

Looking at Distant Objects

Imagine that you simultaneously receive the satellite transmission of two pictures of two people that live on planets orbiting two different stars. Each image shows the people at their 21st birthday parties. Consider the following possible interpretations that could be made from your observations. Which do you think is the most plausible interpretation?

Assumption #1: Lecture is ineffective at promoting deep conceptual change.

• Post-Lecture: questions administered in subsets that directly reflected topic of lecture

Pre-Course mean: 30% (nA=39,nB=42)Post-Lecture mean: 52% (n ~ 100)

• Lecture more loudly?• It’s not what the instructor does that matters;

rather, it is what the students do that matters• Create a learner-centered environment that

promotes the intellectual engagement of your students

• For large-enrollment lectures, we created Lecture-Tutorials for Introductory Astronomy

Development of Lecture-Tutorialsfor Introductory Astronomy

• Based on the topics faculty most often cover • Require ~15-minutes and are designed for easy

implementation into existing traditional lecture courses• Socratic-dialogue driven, highly-structured collaborative

learning activities designed to:• elicit misconceptions• confront naïve, incomplete, or inaccurate ideas• resolve contradictions• demonstrate the power of THEIR conceptual models

Idealized Classroom Implementation• Professor lectures for approximately 20 minutes on core

ideas of the topic to prepare students for working on the activity

• Students are posed a conceptually challenging question on the presented lecture material to set the stage for the activity to come

• Class is divided into pairs or small groups and instructed to work collaboratively and reach consensus on the questions presented in the lecture-tutorial activity

• Professor “debriefs” the activity interactively highlighting the difficulties in reasoning and common problems

• Professor returns to lecture mode on next course topic

Drum roll please

Lecture-Tutorial

Motion

North Star

Earth’s Equator

Celestial Sphere Rotation

Celestial Sphere

Star A

Star B

Figure 1

Horizon

Idealized Classroom Implementation• Professor lectures for approximately 20 minutes on core

ideas of the topic to prepare students for working on the activity

• Students are posed a conceptually challenging question on the presented lecture material to set the stage for the activity to come

• Class is divided into pairs or small groups and instructed to work collaboratively and reach consensus on the questions presented in the lecture-tutorial activity

• Professor “debriefs” the activity interactively highlighting the difficulties in reasoning and common problems

• Professor returns to lecture mode on next course topic

What Do You Do During a Small Group Activity?

• This is the chance to actually get to talk with your students about their learning of astronomy.

• Nudge groups with helpful question to steer their group discussion in the right direction.

• Ask two nearby groups to check their answer and to account for any differences to facilitate class interactions.

• Pull in non-participants by asking them what and why the other group members answered the way that they did.

• Offer thought provoking questions that help students engage with the concepts.

• Circle the wagons afterward ( i.e., debrief )

Always in pursuit of the TEACHABLE MOMENT

Topics

• Light and EM Spect.• Trig. Parallax• Cosmology and B.B.• Telescopes and Star

Maps• Solar System• Our Sun

• Solar System Motion• Moon Phases• Stellar Evolution• Char. of Milky Way• Celestial Sphere• Stellar Magnitudes• Stellar Spectra

Topics

• Light and EM Spect.• Trig. Parallax• Cosmology and B.B.• Telescopes and Star

Maps• Solar System• Our Sun

• Solar System Motion• Moon Phases• Stellar Evolution• Char. of Milky Way• Celestial Sphere• Stellar Magnitudes• Stellar Spectra

Topics

• Cause of Moon Phases

• Predicting Moon Phases

Predicting Moon PhasesWhich of the following is possible?

a) a waxing crescent Moon on the eastern horizon just after sunset.

b) a waning gibbous on the western horizon just after sunset.

c) a waning crescent Moon on the eastern horizon just before sunrise.

d) a full Moon on the western horizon at sunsete) a first quarter moon rising at dawn.

Predicting Moon PhasesWhich of the following is possible?

a) a waxing crescent Moon on the eastern horizon just after sunset.

b) a waning gibbous on the western horizon just after sunset.

c) a waning crescent Moon on the eastern horizon just before sunrise.

d) a full Moon on the western horizon at sunsete) a first quarter moon rising at dawn.

Consider the following debate between two students about the cause of the phases of the Moon.

Which, if either, do you agree with and why?

Student 1: The phase of the Moon depends on how the Moon, Sun and Earth are aligned with one another. During some alignments only a small portion of the Moon’s surface will receive light from the Sun, in which case we would see a crescent moon.

Consider the following debate between two students about the cause of the phases of the Moon. Which,

if either, do you agree with? Why?Student 1: The phase of the Moon depends on how the

Moon, Sun and Earth are aligned with one another. During some alignments only a small portion of the Moon’s surface will receive light from the Sun, in which case we would see a crescent moon.

Student 2: I disagree. The moon would always get the same amount of sunlight it’s just that in some alignments Earth casts a larger shadow on the Moon. That’s why the Moon isn’t always a full moon.

Modern Topics too!!

• Milky Way Scales• Expansion of the Universe• Looking at Distant Objects

Assumption #2: Lecture-Tutorials can intellectually engage students at a

level that is more effective than traditional lecture at promoting deep

conceptual change.

• Post Lecture-Tutorial: questions administered in subsets

Pre-Course mean: 30% (nA=39,nB=42)Post-Lecture mean: 52% (n ~ 100)

• Before Lecture (N=42): 2% correct• After Lecture (N = 135): 19% correct• After Lecture Tutorial (N=134): 66%

correct

a) Star A

b) Star B

c) Star CStar C

Star B

Star A

Wavelength

a) Star A

b) Star B

c) Star CStar C

Star B

Star A

Wavelength

• Before Lecture (N=42): 12% correct• After Lecture (N=120): 16% correct• After Lecture Tutorial (N=80): 80%

correct

NOT TO SCALE

Orbit of the Moon

NOT TO SCALE

Orbit of the Moon

correct

a) luminosity.

b) temperature.

H-R Diagrams and Spectral ClassA red giant of spectral type K9 and a red main sequence star of the same spectral type have the same

a) luminosity.

b) temperature.

correct

• Before Lecture (N=39): 19% correct• After Lecture (N = 85): 27% correct• After Lecture Tutorial (N=75): 56%

correct

• Before Lecture (N=39): 53% correct• After Lecture (N = 94): 51% correct• After Lecture Tutorial (N=77): 77% correct

Assumption #2: Lecture-Tutorials can intellectually engage students at a level

that is more effective than traditional lecture at promoting deep conceptual

change.• Post Lecture-Tutorial: questions

administered in subsets Pre-Course mean: 30% (nA=39,nB=42)Post-Lecture mean: 52% (n ~ 100)Post-Lecture Tutorial: 72% (n ~ 100)

Qualitative Results(focus group)

Students believe that the tutorials are one of the greatest strength of the class

• “I liked the Tutorial, they were very helpful. I am not a science person but feel that I learned a lot from them.

• “Why don’t all professors use tutorials during class?”• “The student interaction and tutorials are a very effective

approach to both teaching and learning. I guarantee most students will retain most of this course.”

“And then the tutorials? I don’t know who ever thought of that. But it’s really how classes should be taught….The tutorials [review concepts] because they break it down. You start with something so simple…and then it slowly gets to more.” –Marti

Qualitative Results(interview)

“I know the worksheets are real helpful. I found it sometimes hard to talk to as many people as I wanted to talk to and finish the worksheet in time.” – Joe

Qualitative Results(interviews)

For those of you who prefer to emphasize quantitative or mathematical reasoning we have

created - Ranking Tasks for Introductory Astronomy

But wait there is more!!

Results: over Eight Core Topics

Pretest

Post-Lecture

Post-Ranking TasksStudy Trial

Percent

Correct

( N ~ 100 ) Core Topics

Seasons

Kepler’s Laws

Star Magnitude & Distance

Motion of the Sky

Phases of the Moon

Gravity

Luminosity of Stars

Doppler Effect

Results: Averages for Eight Core Topics

Pretest

Post-Lecture

Percent

Correct

Both gains are statistically

significant* at .05 level.*Based on series of 8 mixed-factors ANOVA & Least Significant Differences tests.

( N ~ 100 )

Best results with lecture!

More difficult gains!

Results: Averages for Eight Core Topics

Pretest

Post-Lecture

Percent

Correct

( N ~ 100 )

Best results with lecture!

More difficult gains!

Post-Lecture to Post-Ranking Task:

Hake’s Normalized Gain = 0.41 (“moderately large effect”)

Cohen’s d = 0.62 (“Large effect”)

Other Effects of Ranking Tasks?

Gender?

High/Low Students on Pretest?

( Based on repeated factor ANOVA )

Ranking Tasks: Gender Effect?

Pretest

Post-Lecture

Percent

Correct

( N ~ 100 )

Male Female

Ranking Tasks benefited both groups equally.

Ranking Tasks: High vs Low Pretests Groups?

Pretest

Post-Lecture

Percent

Correct

( N ~ 100 )

Upper Median Group

Lower Median Group

Ranking Tasks benefited both groups equally.

Student Attitudes about Ranking Tasks

Students reported that …

“RTs contributed to my interest in course topics?” 52%

“RTs were enjoyable part of classroom experience?” 62%

“RTs helped me prepare for tests?” 72%

“RTs helped my learning of course material?” 83%

What Do You Do During a Small Group Activity?

• This is the chance to actually get to talk with your students about their learning of astronomy.

• Nudge groups with helpful question to steer their group discussion in the right direction.

• Ask two nearby groups to check their answer and to account for any differences to facilitate class interactions.

• Pull in non-participants by asking them what and why the other group members answered the way that they did.

• Offer thought provoking questions that help students engage with the concepts.

• Circle the wagons afterward ( i.e., debrief )

Always in pursuit of the TEACHABLE MOMENT

Always in pursuit of the TEACHABLE

MOMENT

Some Benefits to Doing Activities in Groups • Capitalize on students in your class who like to

socialize

• Revisit complicated concepts in ways besides lecture

• Actually talk to your students about concepts

• Emphasize learning the material that will be on test during class time

• Demonstrate to students that science is about doing stuff, a social endeavor that involves collaboration, not memorizing lists of facts

Critical Questions • What are YOUR beliefs about teaching and learning and how do

they guide your instruction?

• How do YOU want your students to be different as a result of the experiences you design?

• What do YOU know about the research on how STUDENTS learn?

• What strategies and resources are available that are proven to actively engage students and improve their understanding?

• What evidence would YOU accept that your students have made significant gains in conceptual understanding, as well as attitudinal and skill domains?

Just how does one create learning

sequences that motivate students to learn what

we want them to know?Creating the Learner-Centered Environment

How do you decide what to teach out of all that could be covered?

How do you choose which learning strategies to integrate into you class and make it meaningful for the

students?

You must choose to engineer this sequence by considering the answers to the following questions:

What is the highest level question(s) you would want your students to be able to answer? Choose a question(s) that would demonstrate that they really understand?

What activities and experiences do your students need to engage with in order to develop their understanding?

What feedback do you and your students need so you both know you are ready for the next steps and to guide your instruction?

What limited “interactive lecturing” do you need to do to set students up for successful learning experiences in their activities?

Example: Moon PhasesWhat is the highest level question(s) you would want your students to be able to answer? Choose a question(s) that would demonstrate that they really understand?

Now start thinking through the instruction sequence in terms of what a students needs to know to be able to answer this question.

If the moon is in the new phase today, how many of the moon phases shown above would the moon go through during the next 11 days.

A. only oneB. twoC. threeD. more than threeE. none

Which of the following groups of moon phases can be seen (above the horizon) at 11:00 am?

A. Third Quarter, Waning Crescent, and Waxing CrescentB. New Moon, First Quarter, and Waxing GibbousC. Waxing Gibbous, Full Moon, Waning GibbousD. Waxing Crescent, First Quarter, Waxing Gibbous

If the moon is highest in the sky this morning at 6:00 am, what phase will the Moon be in one week from now?

A. fullB. waxing crescentC. waning crescentD. waning gibbousE. new

Example: Moon Phases

Think Pair Share Questions Lecture Tutorials

Case Studies Ranking Tasks

Computer simulations & labs Writing Prompts

and many more

You actually need to work through the activity you choose before you can move forward or you will not be able to design the lecture that supports the activity.

How many phases shown in the picture at the right will the Moon go through in one day?

How long does it take the Earth to complete one rotation? How far will the Moon have moved?

How long does it take the Moon to complete one orbit? How many of the phases will the Moon have gone through in this time?

How much of the Moons total surface is illuminated when it is in the phase identified?

How much of the illuminated surface of the Moon is visible from Earth when it is in the phase identified?

What time is it when the phase identified is highest in the sky? Rising? Setting? What phase will it be in in two weeks….

Questions that a student needs to be asked` (during the interactive lecture) :

Discovering the Night Sky

- Tail Gate Party #1 (a.k.a Exam #1 Review Session): From 4:00 pm – 6:00pm on Tues Sep 12th in RM N210 - Exam #1: Wednesday, Sep 13th Here – N210

How are the motions and positions of Earth and the Sun connected to what

happens on Earth?

• Earth’s rotation on its axis determines the length of the day.

• Earth’s orbit around the Sun determines the length of the year.

• The tilt of Earth’s rotational axis with respect to the plane of Earth’s orbit causes the seasons.

The changing phases of the Moon originally inspired the concept of the month

Moon Phase Names• New Moon• Waxing Crescent• First Quarter• Waxing Gibbous• Full Moon • Waning Gibbous• Third Quarter• Waning Crescent

Watch Movie at:http://aa.usno.navy.mil/graphics/Moon_movie.gif

http://antwrp.gsfc.nasa.gov/apod/image/9911/lunation_ajc.gif OR

http://www.solarviews.com/raw/moon/vmoon2.mpg

The Causes of Moon Phases

• Think to yourself about the answer to this question:

What causes the phases of the Moon?

Take out a piece of paper and quickly write out a brief answer.

Although the Moon is always

½ lit by the Sun, we see

different amounts of the lit portion from

Earth depending on

where the Moon is

located in its orbit.

How long does it take to complete the full cycle of Moon

Phases?A. About a dayB. About a weekC. About a monthD. About a yearE. None of the above

Check your answer with your partner!!

Earth depending on

where the Moon is

located in its orbit.

Let’s Watch some Moon Phase Animations!

Pay attention to where the Moon, Sun and Earth are located and how the Moon appears from Earth at each of these positions.

Look at how much of the Moon is illuminated when at each position.

Look at which side of the Moon is illuminated when at each position.

Earth depending on

where the Moon is

located in its month-long

orbit.

How many phases shown in the picture at the right will the Moon go through in one day?

How long does it take the Earth to complete one rotation? How far will the Moon have moved?

How long does it take the Moon to complete one orbit? How many of the phases will the Moon have gone through in this time?

How much of the Moons total surface is illuminated when it is in the New Phase? Full Phase?

How much of the illuminated surface of the Moon is visible from Earth when it is in the First Quarter Phase, Full Phase?

What time is it when the Waxing Gibbous Phase is highest in the sky, Rising? Setting? What phase will it be in one week later….

What time is it when the waxing

crescent moon is highest in the

sky? When does it first

rises? When does it set?

What moon phase would be

rising in the East at 3pm?

What Moon phase would be

setting in the West at 3pm?

The Moon Phase is highest in the sky at 9pm today. What phase will the Moon be in three weeks after today?

Lecture Tutorials: Cause and Predicting Moon Phases pgs (25 – 32)

• Work with a partner!• Read the instructions and questions carefully.• Discuss the concepts and your answers with one

another. Take time to understand it now!!!!• Come to a consensus answer you both agree on.• If you get stuck or are not sure of your answer,

ask another group.• If you get really stuck or don’t understand what

the Lecture Tutorial is asking, ask one of us for help.

Which Moon position (A-E), shown in the diagram at right, best corresponds with the moon phase shown below?

Orbit of the Moon

Which of the situations shown above occurs at a time closest to sunset?

If the Moon were in the phase shown above, what phase would it be in two weeks later?

If the moon is in the Full phase today, how many of the moon phases shown above would the moon go through during the next 11 days.

A. only oneB. twoC. threeD. more than threeE. none

Which of the following groups of moon phases can be seen (above the horizon) at 3:00 am?

A. Third Quarter, Waning Crescent, and Waxing CrescentB. New Moon, First Quarter, and Waxing GibbousC. Third Quarter, Full Moon, Waning GibbousD. Waxing Crescent, First Quarter, Waxing GibbousE. None of the above is correct

Just how does one create learning

sequences that motivate students to learn what

we want them to know?Creating the Learner-Centered Environment

How do you decide what to teach out of all that could be covered?

How do you choose which learning strategies to integrate into you class and make it meaningful for the

students?

You must choose to engineer this sequence by considering the answers to the following questions:

Example: Doppler ShiftWhat is the highest level question(s) you would want your students to be able to answer? Choose a question(s) that would demonstrate that they really understand?

Use the four spectra shown at right for objects A-D, to answer the next question. Note that one of the spectra is from an object at rest (not moving) and the remaining spectra come from objects that are all moving toward the observer.

Object C

Object D

Object A

Object B

Which of the four objects A-D is moving with the fastest speed?a.Object Ab.Object Bc.Object Cd.Object De.More than one object is moving with the fastest speed.

- Example Doppler ShiftWhat is the highest level question(s) you would want your students to be able to answer? Choose a question(s) that would demonstrate that they really understand?

You actually need to work through the activity you choose before you can move forward or you will not be able to design the lecture that supports the activity.

Think Pair Share Lecture Tutorials

CLEA Ranking Tasks

Class-Action Project Light

and many more

BLUE RED

Spectrum A

Spectrum B

Questions that a student needs to be asked (during the interactive lecture) :

Consider the two spectra shown above of two different Stars A and B.

Which star appears blueshifted?Which star is moving toward you?If it actually turns out that both stars are redshifted relative to a stationary source of light – which star is moving the fastest?

Questions that a student needs to be asked` (during the interactive lecture) :

Consider the star moving counterclockwise.

• When was the star moving toward Earth?

• The star’s light is redshifted by the greatest amount when it is at position ______

• The star’s light would not appear shifted at all when it is at ____________

The Origin and Nature of Light

• Celebration of Knowledge #2 (aka Exam #2) is Wednesday October 11th in N210

• Tailgate Party (aka exam review) is Tuesday October 10th in N210 from 4-6pm here in N210

• HW #5 – Handed out in class September 29th on the topic of Luminosity Area and Temperature, and Due IN-CLASS Wednesday October 4th

The Origin and Nature of Light

• HW#6 – Masteringastronomy online homework on properties of light, atoms and the Doppler Shift. Available October 4th, Due October 11th by 9am.

What physical situation (or object) makes this spectrum?

What can we learn by analyzing starlight?

• A star’s temperature

• A star’s chemical composition

- peak wavelength of the spectral curve

- dips in the spectral curve or the lines in the absorption spectrum

• A star’s motion

The Doppler Effect

• Definition: “The change in wavelength of radiation (light) due to the relative motion between the source and the observer along the line of sight.”

Astronomers use the Doppler Effect to learn about the radial (along the line of sight) motions

of stars, and other astronomical objects.

Real Life Examples of Doppler Effect

• Doppler Radar (for weather)

• Airplane navigation system

• Speed Detection used by Law Enforcement Officers…

• Ok, anything with radar!!!

The Doppler Effect

• Definition: “The change in wavelength of radiation (light) due to the relative motion between the source and the observer along the line of sight.”

Doppler Effect• When something which is giving off light moves

towards or away from you, the wavelength of the emitted light is changed or shifted

Doppler Effect

• When the source of light is moving away from the observer the wavelength of the emitted light will appear to increase. We call this a “redshift”.

Doppler Effect

• When the source of light is moving towards the observer the wavelength of the emitted light will appear to decrease. We call this a “blueshift”.

The Doppler Effect

• Definition: “The change in wavelength of radiation due to relative motion between the source and the observer along the line of sight.”

Doppler Effect• “Along the line of sight” means the

Doppler Effect happens only if the object which is emitting light is moving towards you or away from you.– An object moving “side to side” or

perpendicular, relative to your line of sight, will not experience a Doppler Effect.

Not moving

Redshift

Blueshift

Star moving away from you

Star moving toward you

Astronomy Application

Doppler Shifts• Redshift (to longer wavelengths): The source is

moving away from the observer• Blueshift (to shorter wavelengths): The source is

moving towards the observer

= wavelength shift

o = wavelength if source is not movingv = velocity of source

c = speed of light

BLUE RED

Spectrum A

Spectrum B

BLUE RED

Spectrum A

Spectrum B

Consider the two spectra shown above of two different Stars A and B.

Which star appears blueshifted?Which star is moving toward you?If it actually turns out that both stars are redshifted relative to a stationary source of light – which star is moving the fastest?

Questions that a student needs to be asked :

Consider the star moving counterclockwise.

• When was the star moving toward Earth?

• The star’s light is redshifted by the greatest amount when it is at position ______

• The star’s light would not appear shifted at all when it is at ____________

Doppler Shift Lecture Tutorial Handout

• Work with a partner!• Read the instructions and questions carefully.• Discuss the concepts and your answers with

one another. Take time to understand it now!!!!• Come to a consensus answer you both agree

on and write complete thoughts into your LT.• If you get stuck or are not sure of your answer,

ask another group.

The Doppler Effect causes light from a source moving away to:

1. be shifted to shorter wavelengths.

2. be shifted to longer wavelengths.

3. changes in velocity.

4. Both a and c above

5. Both b and c above

You observe two spectra (shown below) that are redshifted relative to that of a stationary source of light. Which of the following statements best describes how the sources of light that produced the two spectra were moving?

BLUE RED

Spectrum A

Spectrum B

1. Source A is moving faster than source B.

2. Source B is moving faster than source A.

3. Both sources are moving with the same speed.

4. It is impossible to tell from looking at these spectra.

A bright star is moving toward Earth. If you were to look at the spectrum of this

star, what would it look like?

1. an absorption spectrum that is redshifted relative to an unmoving star

2. an emission spectrum that is redshifted relative to an unmoving star

3. a continuous spectrum that is blueshifted relative to an unmoving star

4. an absorption spectrum that is blueshifted relative to an unmoving star

5. a continuous spectrum that is redshifted relative to an unmoving star

What can we learn by analyzing starlight?

• A star’s temperature

• A star’s chemical composition

- peak wavelength of the spectral curve

- dips in the spectral curve or the lines in the absorption spectrum

• A star’s motion- Doppler shift

Solving Our "Problems"

Work in a group to complete the following assignment:

• You are going to be teaching about the subject of ____________

• What is the highest level question(s) you would want your students to be able to answer? Choose a question(s) that would demonstrate that they really understand?

Learner Centered Astronomy A Teaching Excellence Workshop Ed Prather and Gina Brissenden University...

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