Core Course Review Documentation
Foundational Component Area: LIFE & PHYSICAL SCIENCES
Component Area Option? No
Proposed Course: Descriptive Astronomy (Phys 1533)
Credit Hours: 3 (2 hours lecture, 1 hour lab)
Proposed by: Jacqueline Dunn
Date: January 16, 2013
Please document how the proposed course meets each of the following requirements. (You
may provide a written explanation or copy and paste the appropriate information from the
syllabus.)
Content:
Courses in this category focus on describing, explaining, and predicting natural
phenomena using the scientific method.
Descriptive Astronomy covers the basic components of the universe. Students learn how
stars and planetary systems are formed, why we have the galaxies that we see, and
ultimately how and why the universe exists the way it does. The relationships between the
science of astronomy, astronomical beliefs, and various cultures (both historical and
current) are also explored. Students are presented with a historical development of the
science of astronomy, leading them through the process of the scientific method. Content is
addressed through lectures, readings, and hands-on laboratory activities.
SKILLS:
Courses involve the understanding of interactions among natural phenomena and the
implications of scientific principles on the physical world and on human experiences.
Students will be able to:





Explain the development of the universe beginning with the Big Bang and ending with
the formation and evolution of our solar system.
Apply the scientific method in evaluating scientific theories.
Acknowledge commonly held biases and recognize the impact those biases can have on
their evaluation of scientific theories.
Analyze data to form conclusions regarding various astronomical processes.
Recognize the impact of the study of astronomy in their day to day lives.
ASSESSMENT OF CORE OBJECTIVES:
Assessments should be authentic, intentional and
direct. The following four Core Objectives must be addressed in each course approved to fulfill this
category requirement:
Critical Thinking Skills - to include creative thinking, innovation, inquiry, and analysis, evaluation
and synthesis of information
Critical thinking skills are developed through inquiry-based activities contained in the text
Lecture-Tutorials for Introductory Astronomy. A specific tutorial activity used in this
assessment is attached in this file. Students will complete the tutorial over the greenhouse
effect (at the end of this file). Students will be evaluated to see if they have exceeded the
benchmark level of the AACU VALUE Rubric for Critical Thinking (attached in this file).
Communication Skills - to include effective development, interpretation and expression of ideas
through written, oral, and visual communication
Oral communication skills are developed through preparation of PowerPoint presentations
concerning the impact of astronomy on a culture of their choice and written
communication skills are developed through an accompanying paper. Students are
assigned a semester project that consists of a three-page paper and five to ten minute
presentation on the astronomical beliefs of a culture of their choice. Students will be
evaluated to see if they have exceeded the benchmark level of the Assessment for
Communication Skills Rubric (see attachment in this file), which focuses on Visual
Communication, and has been created based on the AACU VALUE Rubrics for Oral and
Written Communication (attached).
Empirical and Quantitative Skills - to include the manipulation and analysis of numerical data or
observable facts resulting in informed conclusions
Empirical analytical skills and quantitative skills are developed through assigned readings
and laboratory activities that require students to gather and analyze data. The specific
assessment used in this course is a laboratory exercise where students are asked to draw
conclusions based on data collected relating to the colors of galaxies (see attached in this
file). Students will be evaluated to see if they have exceeded the benchmark level of the
AACU VALUE Rubric for Quantitative Literacy (attached in this file).
Teamwork - to include the ability to consider different points of view and to work effectively with
others to support a shared purpose or goal
Teamwork skills are developed through group projects in class and in the laboratory along
with group discussions based on the Lecture Tutorials mentioned above (an example is
attached in this file). The specific assessment will be for the Lecture Tutorials on the
Greenhouse Effect, also used to assess Critical Thinking. For students who meet in class,
the assessment is based on their participation in the group work sessions. For students
who take the online section of the course, the assessment is based on their participation in
the assigned associated discussions. In both cases, students will be evaluated to see if they
have exceeded the benchmark level of the AACU VALUE Rubric for Teamwork (attached in
this file).
ADDITIONAL INFORMATION: Provide any additional information supporting course
inclusion in the core (optional).
Descriptive Astronomy provides students with a great foundation in general science and is it
includes basic concepts from physics, chemistry, and geosciences in addition to solely
astronomical concepts.
PLEASE ATTACH THE FOLLOWING
1.
2.
3.
4.
5.
Syllabus
Assessment for Critical Thinking Skills
Assessment for Communication Skills
Assessment for Empirical & Quantitative Skills
Assessment for Teamwork
Phys 1533 – Descriptive Astronomy
Online Section
Instructor: Dr. Jackie Dunn
Office: McCoy Hall, 219D
Office Phone: (940) 397-4184 (less reliable)
Email: jackie.dunn@mwsu.edu (more reliable)
Textbook: Astronomy, A Beginner’s Guide to the Universe, 6th Edition with
MasteringAstronomy by Chaisson & McMillan (ISBN: 0321598768) and LectureTutorials for Introductory Astronomy, 2nd Edition by Prather, Slater, Adams, &
Brissenden (ISBN: 0132392267)
Grading: Labs – 15%, Homework/Quizzes – 15%,
Discussion/Participation – 10%, Exams (3 @ 15% each) – 45%
Project
–
15%,
Course Description: This course is designed to introduce the student to the basic
concepts of astronomy. AKA The Universe in a Semester.
Lab: Labs will sometimes come from the Lecture Tutorials handbook, other times it will
involve making use of resources available on the internet.
Expectations: Students should read the chapters to be covered prior to looking over
the lectures and attempting any assignments.
Cheating and plagiarism will not be tolerated. If you take a direct quote from a source
for one of your assignments, please indicate so by using quotation marks and citing the
source. It should go without saying that any work you hand in should be your own.
Note: In accordance with the law, MSU provides students with documented disabilities
academic accommodations. If you are a student with a disability, please contact me.
Note: By enrolling in this course, the student expressly grants MSU a "limited right" in
all intellectual property created by the student for the purpose of this course. The
"limited right" shall include but shall not be limited to the right to reproduce the student's
work product in order to verify originality and authenticity, and for educational purposes.
Exams: Exams will be made available on the dates listed below. The final exam will be
cumulative. Each exam will be available online for approximately 1 week. Unless you
make arrangements with me prior to the exam, there will be no exceptions to the due
dates. Exams will be timed exercises. You will receive more information on their format
one week prior to the first exam.
Exam 1:
September 29, 2012
Exam 2:
November 10, 2012
Final Exam: December 8, 2012
Schedule of Topics:
Assessment for Critical Thinking Skills
Lecture-Tutorials for Introductory Astronomy, 2nd Edition by Prather, Slater, Adams, &
Brissenden (ISBN: 0132392267)
The lecture tutorials are self-contained exercises designed to be completed within about 15
minutes. Each tutorial covers a different subject matter within astronomy. The students
are led through a series of questions in such a way that they will normally recognize any
misunderstandings on their in the end (basically, the same question is posed to them in
different forms multiple times.) Some tutorials involve interpreting data or diagrams to
draw conclusions. The students discuss their answers with each other in small groups and
attempt to reach a consensus.
The specific lecture tutorial used to assess Critical Thinking in PHYS 1533 is over the
Greenhouse Effect. The tutorial is attached at the end of this file.
The AACU critical thinking rubric is applied (see below).
Capstone
Milestones
Benchmark
4
3
2
1
Explanation of
issues
Issue/problem to be
considered critically is
stated clearly and
described
comprehensively,
delivering all relevant
information necessary
for full understanding.
Issue/problem to be
considered critically is
stated, described, and
clarified so that
understanding is not
seriously impeded by
omissions.
Issue/problem to be
considered critically is
stated but description
leaves some terms
undefined, ambiguities
unexplored,
boundaries
undetermined, and/or
backgrounds
unknown.
Issue/problem to be
considered critically is
stated without
clarification or
description.
Evidence
Selecting and using
information to
investigate a point of
view or conclusion
Information is taken
from source(s) with
enough
interpretation/evaluati
on to develop a
comprehensive
analysis or synthesis.
Viewpoints of experts
are questioned
thoroughly.
Information is taken
from source(s) with
enough
interpretation/evaluati
on to develop a
coherent analysis or
synthesis.
Viewpoints of experts
are subject to
questioning.
Information is taken
from source(s) with
some
interpretation/evaluati
on, but not enough to
develop a coherent
analysis or synthesis.
Viewpoints of experts
are taken as mostly
fact, with little
questioning.
Information is taken
from source(s) without
any
interpretation/evaluati
on.
Viewpoints of experts
are taken as fact,
without question.
Influence of
context and
assumptions
Thoroughly
(systematically and
methodically) analyzes
own and others'
assumptions and
carefully evaluates the
relevance of contexts
when presenting a
position.
Identifies own and
others' assumptions
and several relevant
contexts when
presenting a position.
Questions some
assumptions.
Identifies several
relevant contexts when
presenting a position.
May be more aware of
others' assumptions
than one's own (or
vice versa).
Shows an emerging
awareness of present
assumptions
(sometimes labels
assertions as
assumptions). Begins
to identify some
contexts when
presenting a position.
Student's
position
(perspective,
thesis/hypothes
Specific position
(perspective,
thesis/hypothesis) is
imaginative, taking
Specific position
(perspective,
thesis/hypothesis)
takes into account the
Specific position
(perspective,
thesis/hypothesis)
acknowledges different
Specific position
(perspective,
thesis/hypothesis) is
stated, but is simplistic
is)
into account the
complexities of an
issue.
Limits of position
(perspective,
thesis/hypothesis) are
acknowledged.
Others' points of
view are synthesized
within position
(perspective,
thesis/hypothesis).
complexities of an
issue.
Others' points of
view are
acknowledged within
position (perspective,
thesis/hypothesis).
sides of an issue.
and obvious.
Conclusions and
related
outcomes
(implications
and
consequences)
Conclusions and
related outcomes
(consequences and
implications) are
logical and reflect
student’s informed
evaluation and ability
to place evidence and
perspectives discussed
in priority order.
Conclusion is logically
tied to a range of
information, including
opposing viewpoints;
related outcomes
(consequences and
implications) are
identified clearly.
Conclusion is logically
tied to information
(because information
is chosen to fit the
desired conclusion);
some related outcomes
(consequences and
implications) are
identified clearly.
Conclusion is
inconsistently tied to
some of the
information discussed;
related outcomes
(consequences and
implications) are
oversimplified.
Assessment for Communication Skills
Students are assigned a semester project that consists of a three page paper and five to ten
minute presentation on the astronomical beliefs of a culture of their choice.
Paper Rubric:
Points
Grammar
Style
5
No more than a few
typos or other
grammatical problems.
Paper flows naturally
and paragraphs are
used correctly.
Content
Paper is 3 full pages in
length. Covers an
appropriate breadth of
topics and topics are
not repeated.
References Has required minimum
of 3 references, with at
least 1 print reference.
Citations are used
correctly throughout.
3
More than four typos per
page or other significant
grammatical error.
1
Has 3 references, but all
are internet sources. Only
has 2 references. Missing
some citations within the
text.
Lacks any references,
or includes a reference
list without including
any citations within the
body of the paper.
Significant
grammatical problems
(poor sentence
structure, etc.) and
many misspelled
words.
Transitions between
Paper is written
topics may be occasionally without any
sudden or topics may be
paragraphs or jumps
grouped together
from one topic to the
inappropriately.
next with no
transitions.
Content is slightly
Paper is less than 2.5
repetitive. Paper may be
pages in length. Ideas
just shy of 3 full pages in
are repeated multiple
length.
times.
Presentation Rubric:
Points
Content
5
Appropriate amount
of content to fill the
allotted time.
3
Slightly less or more
content than what
was needed for the
allotted time (under
or over by less than
a two minutes).
Creativity
Uses graphics
appropriately and
often. May make use
of props.
Speaks to audience.
No significant breaks
in speech.
Conducted in a
professional manner.
Uses graphics
appropriately, but
doesn’t include any
extras (no props).
Loses train of
thought but recovers
well. Conducted in a
less serious manner
(too many jokes, not
Style
1
Significantly less or
more content than
what was needed for
the allotted time
(under or over by
more than two
minutes).
Little or no graphics.
Rarely or never
makes eye contact
with audience. May
treat entire talk as a
joke. Not
formal enough, etc.)
or reads straight
from paper.
professional at all.
Assessment for Empirical & Quantitative Skills
Students are assigned a laboratory exercise where they gather archived information on the
colors of galaxies and then use that information to answer specific questions about what
types of stars are most likely present based on the color information. The exercise is
copied below, after the rubric.
The AACU quantitative literacy rubric is applied (copied below).
Capstone
4
Milestones
3
2
Benchmark
1
Interpretation
Ability to explain
information presented in
mathematical forms (e.g.,
equations, graphs, diagrams,
tables, words)
Provides accurate
explanations of
information presented
in mathematical forms.
Makes appropriate
inferences based on
that information. For
example, accurately
explains the trend data
shown in a graph and
makes reasonable
predictions regarding what
the data suggest about
future events.
Provides accurate
explanations of
information presented
in mathematical forms.
For instance, accurately
explains the trend data
shown in a graph.
Provides somewhat
accurate explanations of
information presented
in mathematical forms,
but occasionally makes
minor errors related to
computations or units.
For instance, accurately
explains trend data shown
in a graph, but may
miscalculate the slope of the
trend line.
Attempts to explain
information presented
in mathematical forms,
but draws incorrect
conclusions about what
the information means.
For example, attempts to
explain the trend data
shown in a graph, but will
frequently misinterpret the
nature of that trend,
perhaps by confusing
positive and negative trends.
Representation
Ability to convert relevant
information into various
mathematical forms (e.g.,
equations, graphs, diagrams,
tables, words)
Skillfully converts
relevant information
into an insightful
mathematical portrayal
in a way that
contributes to a further
or deeper
understanding.
Competently converts
relevant information
into an appropriate
and desired
mathematical
portrayal.
Completes conversion
of information but
resulting mathematical
portrayal is only partially
appropriate or accurate.
Completes conversion
of information but
resulting mathematical
portrayal is
inappropriate or
inaccurate.
Calculation
Calculations attempted
are essentially all
successful and
sufficiently
comprehensive to
solve the problem.
Calculations are also
presented elegantly
(clearly, concisely, etc.)
Calculations attempted
are essentially all
successful and
sufficiently
comprehensive to
solve the problem.
Calculations attempted
are either unsuccessful
or
represent only a portion
of the calculations
required to
comprehensively solve
the problem.
Calculations are
attempted but are both
unsuccessful and are
not comprehensive.
Application / Analysis
Ability to make judgments
and draw appropriate
conclusions based on the
quantitative analysis of data,
while recognizing the limits
of this analysis
Uses the quantitative
analysis of data as the
basis for deep and
thoughtful judgments,
drawing insightful,
carefully qualified
conclusions from this
work.
Uses the quantitative
analysis of data as the
basis for competent
judgments, drawing
reasonable and
appropriately qualified
conclusions from this
work.
Uses the quantitative
analysis of data as the
basis for workmanlike
(without inspiration or
nuance, ordinary)
judgments, drawing
plausible conclusions
from this work.
Uses the quantitative
analysis of data as the
basis for tentative,
basic judgments,
although is hesitant or
uncertain about
drawing conclusions
from this work.
Assumptions
Ability to make and evaluate
important assumptions in
estimation, modeling, and
data analysis
Explicitly describes
assumptions and
provides compelling
rationale for why each
assumption is
appropriate. Shows
awareness that
confidence in final
conclusions is limited
by the accuracy of the
assumptions.
Explicitly describes
assumptions and
provides compelling
rationale for why
assumptions are
appropriate.
Explicitly describes
assumptions.
Attempts to describe
assumptions.
Communication
Expressing quantitative
evidence in support of the
argument or purpose of the
work (in terms of what
evidence is used and how it is
formatted, presented, and
contextualized)
Uses quantitative
information in
connection with the
argument or purpose
of the work, presents
it in an effective
format, and explicates
it with consistently
high quality.
Uses quantitative
information in
connection with the
argument or purpose
of the work, though
data may be presented
in a less than
completely effective
format or some parts
of the explication may
be uneven.
Uses quantitative
information, but does
not effectively connect
it to the argument or
purpose of the work.
Presents an argument
for which quantitative
evidence is pertinent,
but does not provide
adequate explicit
numerical support.
(May use quasiquantitative words such
as "many," "few,"
"increasing," "small,"
and the like in place of
actual quantities.)
Assessment for Teamwork
Sections that meet on campus:
Lecture-Tutorials for Introductory Astronomy, 2nd Edition by Prather, Slater, Adams, &
Brissenden (ISBN: 0132392267)
The lecture tutorials are self-contained exercises designed to be completed within about 15
minutes. Each tutorial covers a different subject matter within astronomy. The students
are led through a series of questions in such a way that they will normally recognize any
misunderstandings on their in the end (basically, the same question is posed to them in
different forms multiple times.) Some tutorials involve interpreting data or diagrams to
draw conclusions. The students discuss their answers with each other in small groups and
attempt to reach a consensus. A sample lecture tutorial is attached at the end of this file.
Sections that meet online only:
Based on the same assignments above, students are required to participate in online
discussions of the answers for selected tutorials. The instructor only gives students the
correct answers if the group as a whole fails to reach a consensus through these
discussions. The goal of the discussions is to mimic the work done in person within a small
group as much as is possible in the online environment.
In both cases above, the AACU teamwork rubric is applied (copied below).
Capstone
4
Milestones
3
2
Benchmark
1
Contributes
to Team
Meetings
Helps the team move
forward by articulating
the merits of alternative
ideas or proposals.
Offers alternative
solutions or courses of
action that build on the
ideas of others.
Offers new suggestions
to advance the work of
the group.
Shares ideas but does not
advance the work of the
group.
Facilitates the
Contributions
of Team
Members
Engages team members
in ways that facilitate
their contributions to
meetings by both
constructively building
upon or synthesizing the
contributions of others
as well as noticing when
someone is not
participating and
inviting them to engage.
Engages team members
in ways that facilitate
their contributions to
meetings by
constructively building
upon or synthesizing the
contributions of others.
Engages team members
in ways that facilitate
their contributions to
meetings by restating
the views of other team
members and/or asking
questions for
clarification.
Engages team members
by taking turns and
listening to others without
interrupting.
Individual
Contributions
Outside of
Team
Meetings
Completes all assigned
tasks by deadline;
work accomplished is
thorough,
comprehensive, and
advances the project.
Proactively helps other
team members complete
their assigned tasks to a
similar level of
excellence.
Completes all assigned
tasks by deadline;
work accomplished is
thorough,
comprehensive, and
advances the project.
Completes all assigned
tasks by deadline;
work accomplished
advances the project.
Completes all assigned
tasks by deadline.
Fosters
Supports a constructive
Supports a constructive
Supports a constructive
Supports a constructive
Constructive
Team
Climate
team climate by doing
team climate by
team climate by
team climate by doing any
all of the following:
doing any three of the
doing any two of the
one of the following:
• Treats team
following:
following:
• Treats team
members
• Treats team
• Treats team
members
respectfully by
members
members
respectfully by
being polite
respectfully by
respectfully by
being polite and
and
being polite
being polite
constructive in
constructive in
and
and
communication.
communication
constructive in
constructive in
• Uses positive
.
communication
communication
vocal or written
• Uses positive
.
.
tone, facial
vocal or
• Uses positive
• Uses positive
expressions,
written tone,
vocal or
vocal or
and/or body
facial
written tone,
written tone,
language to
expressions,
facial
facial
convey a positive
and/or body
expressions,
expressions,
attitude about the
language to
and/or body
and/or body
team and its
convey a
language to
language to
work.
positive
convey a
convey a
• Motivates
attitude about
positive
positive
teammates by
the team and
attitude about
attitude about
expressing
its work.
the team and
the team and
confidence about
• Motivates
its work.
its work.
the importance
teammates by
• Motivates
• Motivates
of the task and
expressing
teammates by
teammates by
the team's ability
confidence
expressing
expressing
to accomplish it.
about the
confidence
confidence
• Provides
importance of
about the
about the
assistance and/or
the task and the
importance of
importance of
encouragement
team's ability
the task and the
the task and the
to team
to accomplish
team's ability
team's ability
members.
it.
to accomplish
to accomplish
• Provides
it.
it.
assistance
• Provides
• Provides
and/or
assistance
assistance
encouragement
and/or
and/or
to team
encouragement
encouragement
members.
to team
to team
members.
members.
Responds to
Conflict
Addresses destructive
conflict directly and
constructively, helping
to manage/resolve it in a
way that strengthens
overall team
cohesiveness and future
effectiveness.
Identifies and
acknowledges conflict
and stays engaged with
it.
Redirecting focus
Passively accepts alternate
toward common ground, viewpoints/ideas/opinions.
toward task at hand
(away from conflict).
Greenhouse Effect
Section 1: Effective temperature of Earth
The Earth system gives off the same amount of energy that it absorbs from the Sun. If this did not happen
and our planet absorbed more energy than it gives off, Earth would continuously become warmer and
warmer.
Incoming Solar Radiation
Outgoing Planet Radiation
By setting the incoming solar radiation absorbed by Earth equal to the outgoing radiation emitted by
Earth, we can estimate that the effective temperature of Earth would be 255K (0F). Note that this
estimate assumes that Earth has no atmosphere and reflects 30% of the incoming sunlight.
1) How would the surface of our planet be different if its temperature was 0F?
2) Give one possible reason why the average surface temperature of our planet actually turns out
to be much warmer at 288K (58F).
Section 2: Photon spectrum versus solar spectrum
3) Does a photon with a short wavelength have more or less energy than a photon with a long
wavelength?
CAPER TEAM
DRAFT EDITION, 2005
LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY
18
Greenhouse Effect
In the graphs below, the wavelength of a given photon is shown on the horizontal axis. The energy
per photon is shown on the vertical axis. The line or curve drawn is provided to illustrate the
relationship between the energy of a photon versus the wavelength of that photon.
B
C
X-ray
short
UV
VIS
IR
Radio
wavelength
Energy per photon
Energy per photon
Energy per photon
A
X-ray
short
long
UV
VIS
IR
Radio
wavelength
long
X-ray
short
UV
VIS
IR
Radio
wavelength
4) Which graph above most correctly represents how you think the energy of a photon is related
to its wavelength? Explain your answer.
The previous two questions dealt with the energy of an individual photon. However, objects give off
different numbers of photons at each wavelength depending upon their temperature. Figure 1 below
shows the energy spectrum for our Sun along with the percent of energy radiated by the Sun in the
ultraviolet (UV), visible, and infrared portions of the electromagnetic spectrum.
Solar Spectrum
5
Energy Units
4
3
2
UV
7%
1
0
0
100
200
300
400
IR
37%
VIS
44%
500
600
700
800
900 1000 1100 1200 1300 1400 1500
Wavelength (nm)
Figure 1
5) How many times greater is the amount of visible light given off by the Sun compared to the amount
of ultraviolet light given off by the Sun? Show how you got to this result.
CAPER TEAM
DRAFT EDITION, 2005
LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY
19
long
Greenhouse Effect
6) Why aren’t x-ray and ultraviolet photons as important for heating Earth as visible and infrared
photons?
7) Consider the following debate between two students regarding the energy given off by the Sun.
Student #1 – I think that the Sun gives off most of its energy at ultraviolet wavelengths because
ultraviolet light is more intense than visible light and more efficient at carrying energy.
Student #2 – Actually, x-rays are even more energetic than ultraviolet photons. Shouldn’t they be
the most important energy source coming from the Sun?
Student #3 – Hold up, even though UV and x-ray photons are more energetic than visible photons,
the Sun gives off way more visible and infrared photons. So I think that these longer wavelength
photons account for most of the energy coming from the Sun.
Do you agree and/or disagree with any or all of these students? Explain your reasoning.
CAPER TEAM
DRAFT EDITION, 2005
LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY
20
Greenhouse Effect
Section #3: Atmospheric absorption of light
The temperature of the surface of our planet is affected primarily by the energy we receive from the Sun
that is able to reach Earth’s surface. However, a photon’s ability to penetrate all the way through our
atmosphere and reach the ground depends upon its wavelength. Figure 2 below shows that certain
wavelengths of light are absorbed in our atmosphere before they can travel all the way to the surface of
Earth.
UV
VIS
O2 & O 3
IR
H2O H2O CO2
CO2 H2O
O3
CO2
H2O (rotation)
H2O
Taken from Goody & Walker, Atmospheres, Prentice-Hall: 1972.
Figure 2
8) Light is absorbed at each of the following wavelengths. For each, list the molecule(s) in the
atmosphere that is responsible for this absorption.
Wavelength
1.4 microns
Molecule(s) Responsible for Absorption
1.7 microns
2.7 microns
6 microns
9 microns
15 microns
30-100 microns
9) Roughly what percentage of ultraviolet light (between 0.1-0.4 microns) is absorbed before
reaching Earth’s surface? Describe the difference in absorption between UV light with shorter
wavelengths (0.1 – 0.3 microns) and UV light with longer wavelengths (0.3 – 0.4 microns).
10) Roughly what percentage of visible light (between 0.4-0.7 microns) is absorbed before reaching
Earth’s surface?
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Greenhouse Effect
11) Comparing the visible and the infrared parts of the spectrum, which would you say has an
easier time getting through our atmosphere?
12) Compare the absorption graph in Figure 2 with the energy spectrum of our Sun in Figure 1.
Which wavelength of light would you say is most responsible for heating the surface of our
planet? Explain your answer and refer to both figures in your explanation.
Section 4: Spectrum from Earth’s surface
Once visible light from the Sun reaches the surface of Earth, it can either be reflected back towards
space as visible light or be absorbed by the ground. This absorbed visible light causes the
temperature of the surface to increase. The ground then gives off energy based upon its increased
temperature.
C
Energy
Energy
B
Energy
A
X-ray
short
UV
VIS
IR
Radio
wavelength
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DRAFT EDITION, 2005
long
X-ray
short
UV
VIS
IR
Radio
wavelength
long
X-ray
short
UV
VIS
IR
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Radio
wavelength
long
Greenhouse Effect
13) Which of the diagrams (A, B, or C) above most accurately represents the energy given off by
Earth’s surface as a function of wavelength? Explain your reasoning.
14) At what wavelength does Earth’s surface give off the most energy?
15) Will the light given off by Earth’s surface easily travel back through the atmosphere to space
or will it be absorbed by molecules in the atmosphere? Explain your reasoning.
16) What happens to the temperature of the atmosphere as it absorbs light from either the Sun
or from Earth’s surface?
Section 5: The Greenhouse Effect
You should now have a picture of visible light traveling all the way through the atmosphere to the surface
of Earth while infrared light (both from the Sun and from Earth’s surface) cannot travel very far through
the atmosphere without being absorbed. It is important to note that this absorbed infrared light doesn’t
disappear and also isn’t trapped in the atmosphere forever; rather, it simply travels a shorter distance
through the atmosphere before it is absorbed and then given off again in a random direction. So, while
visible light can travel all the way through the atmosphere without being absorbed, infrared light is
continuously absorbed and given off and absorbed and given off many times as it travels through the
atmosphere.
CAPER TEAM
DRAFT EDITION, 2005
LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY
23
Greenhouse Effect
The diagrams below show possible paths for visible and infrared light as they travel through Earth’s
atmosphere. Visible light is represented with dashed arrows; infrared light is shown with solid
arrows. Note that three out of the eight diagrams properly depict possible paths for visible and
infrared light through the atmosphere.
A
VIS
B
C
IR
VIS
IR
D
VIS
IR
IR
top of atmosphere
IR
Earth’s surface
E
VIS
G
F
IR
IR
IR
IR
H
VIS
VIS
top of atmosphere
IR
Earth’s surface
CAPER TEAM
DRAFT EDITION, 2005
LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY
24
Greenhouse Effect
17) List the FIVE diagrams that incorrectly depict how visible and infrared light travel through
the atmosphere? For each, describe what is wrong with the diagram.
18) Of the remaining three diagrams, which shows visible light reflecting off the surface of the
earth and traveling back out to space as visible light? If this light is completely reflected,
does it do any heating of the surface?
19) In the space below, redraw the TWO diagrams that properly show how visible and infrared
light travel through the atmosphere and lead to an enhanced surface temperature.
top of atmosphere
Earth’s surface
CAPER TEAM
DRAFT EDITION, 2005
LECTURE-TUTORIALS FOR INTRODUCTORY ASTRONOMY
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Greenhouse Effect
20) What is the source of visible photons that heat the surface of Earth? What are the TWO
sources of infrared photons that heat the air in our atmosphere?
21) If the surface of Earth immediately gave off to outer space the same amount of energy as it
received from the Sun, the surface would be 255K (0F). Where does the additional energy
come from that heats the surface of Earth to its measured value of 288K (58F)?
The transfer of energy that you diagrammed in Question #19 is the source of the natural
“Greenhouse Effect.” Because Earth has an atmosphere that inhibits the transport of infrared light,
the atmosphere becomes warmer and gives energy back to the surface, leading to a surface
temperature that is 58F warmer than Earth’s effective temperature of 255K (0F).
22) Go back to your answer to Question #8. What are the primary “greenhouse gases” in our
atmosphere? What characteristic makes them greenhouse gases?
23) Imagine that in the middle of the night you pointed a very sensitive infrared camera at the
sky and took a picture. Would your picture be dark (indicating no detected infrared light)
or bright (indicating many infrared photons)? Explain your reasoning.
24) Is your answer to Question #23 consistent with what you know about the greenhouse
effect? Why or why not?
CAPER TEAM
DRAFT EDITION, 2005
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