Astronomy final exam question: Pluto and Earth's moon switch

Astronomy 210 Final Exam, fall semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss how Pluto and how Earth's moon would each be classified by the International Astronomical Union if they were to exchange positions. (Consider them to be approximately the same mass.)

Solution and grading rubric:

• p = 20/20:
  Correct. Pluto would become a moon of Earth's, while the Earth's moon would orbit the sun directly (and not be a moon), retain its round shape (and thus not be solar system debris), but as it would neither clear out nor dominate the Kuiper belt anymore than Pluto did, it would now be classified as a
  dwarf planet, and not a planet. (May use dwarf planet synonymously with "planetoid" or "small planet.")
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. One of the classifications is problematic, but the IAU classification scheme is systematically applied to both objects.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Some discussion of difference in lifetimes, but compounded/confounded with other factors. Problematic application of IAU classification scheme.
  
• v = 8/20: Limited relevant discussion of supporting evidence of at least some
  merit, but in an inconsistent or unclear manner. Uses criteria other than that defined by the IAU classification scheme.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70158
p: 20 students
r: 17 students
t: 10 students
v: 15 students
x: 3 students
y: 3 students
z: 1 student

A sample "p" response (from student 0805):
An illustrated "p" response (from student 1616):
A "p" response (from student 0013) anthropomorphizing Pluto and Earth's moon:
A sample "v" response (from student 3825) speculating on the mind-boggling implications of this Pluto-Earth's moon switch:
A sample "x" response (from student 5588) equating Pluto and Earth's moon:
A sample "y" response (from student 6948):

Astronomy final exam question: closer Mars?

Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] If Mars had originally formed closer to the Sun, discuss whether its atmosphere would now be thinner than, thicker than, or the same as it is today. Explain your reasoning.

Solution and grading rubric:

• p = 20/20:
  Correct. Mars lost its atmosphere due to two effects--its weak gravity (due to its small mass) is unable to hold on to molecules in its atmosphere, and lack of an ozone layer allowed ultraviolet light to break down molecules into constituent atoms, allowing them to more easily escape. Having Mars form closer to the Sun would exacerbate both effects, as a higher temperature would cause molecules/atoms in the atmosphere to move faster. (May refer to escaping molecules as due to the Sun "burning off" the atmosphere, or calls this process "outgassing").
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses how Mars would then be warm enough to have oceans and water vapor would contribute to a temporarily more thicker atmosphere.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Some discussion of difference in lifetimes, but compounded/confounded with other factors. Garbled discussion, but recognition of related factors such as mass, ozone layer, distance from Sun, temperature, and greenhouse effect.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Involving unrelated factors, such as an inverse correlation between distance from Sun and thickness of atmosphere, Mars now being in the habitable zone and thus sustaining life, or heat causing Mars' surface to begin outgassing.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70158
p: 18 students
r: 11 students
t: 15 students
v: 24 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response for Mars having a thinner atmosphere (from student 3259):

A sample "p" response for Mars having a thicker (albeit, temporarily so) atmosphere (from student 7070):

A sample "r" response (from student 0013):

Examples of sample "t" responses, discussing how the position would determine the thinness/thickness of an atmosphere, but with no discussion as to why this would be so (here, from student 0725):

(...and from student 1616):

(...and from student 9933):

Astronomy final exam question: supergiant and white dwarf star cluster?

Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] Why is it not possible to have both white dwarfs and supergiants in the same star cluster? Explain using the properties of mass and stellar lifetimes.

Solution and grading rubric:

• p = 20/20:
  Correct. Discusses how all stars in a cluster are born at the same time and have the same age, but supergiants arise from massive stars, which have much faster evolution rates/shorter lifetimes than medium mass stars, which eventually become white dwarfs.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. At least understands how lifetimes depends on masses, but does not explicitly connect end stages to mass (i.e., may not distinguish convincingly between using "white dwarf" interchangeably with "red dwarf").
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Some discussion of difference in lifetimes, but compounded/confounded with other factors. May argue that this is possible if the supergiants came from "elsewhere" to mingle with white dwarfs.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May discuss how these stars feed on or disrupt each other, etc.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70158
p: 10 students
r: 25 students
t: 16 students
v: 16 students
x: 0 students
y: 1 student
z: 0 students

A sample "p" response (from student 4562):

Another sample "p" response (from student 9057):

And another sample "p" response (from student 3008):

A sample "r" response (from student 3578), conflating white dwarfs with red dwarfs:

Several other sample "r" responses (starting with student 1616), conflating white dwarfs with red dwarfs, but in the framework of the "house party" model (discussed in class) of stellar evolution rates in star clusters (massive stars = people who come early, stay briefly, leave early; low mass stars = people who show up very late, stay over and never leave):


(...and from student 1990):

(...and from student 2007):

A sample "t" response (from student 7787), positing that stars in the same cluster must all have the same mass:

Another sample "t" response (from student 4409), burying the correct answer with a list of ruminative speculation:

Two sample "v" responses (starting with student 1327), discussing how supergiants would somehow interfere with white dwarfs if they were in the same star cluster:

(...and from student 3825):

A sample "v" response (from student 4018) discussing how supergiants and white dwarfs in the same star cluster would incongruous:

Astronomy final exam question: the Drake equation

Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] The Drake equation estimates the number of technological civilizations in the Milky Way by:
(A) estimating the number of inhabited planets, and lifetimes of technological civilizations.
(B) estimating the number of possible signals receivable by radio telescopes.
(C) extrapolating the past progress of Earth technology.
(D) assuming that it is impossible for there to be only one technological civilization.

Section 70158
(A) : 51 students
(B) : 10 students
(C) : 3 students
(D) : 5 students

Correct answer: (A)

Response (A) is the definition of the Drake equation.

This was asked previously this semester as a quiz question.

"Difficulty level": 64% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33

Astronomy final exam question: metal rich vs. metal poor stars

Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

Older stars are metal poor, while newer stars are metal rich because:
(A) metals produced by older stars were released by supernova explosions, and became part of newer stars.
(B) dark matter gradually converts metal rich stars into metal poor stars.
(C) older stars concentrate more of their metals into their cores, leaving their outer layers metal poor.
(D) older stars have had more time to break down heavy elements into lighter elements.

Section 70158
(A) : 41 students
(B) : 1 student
(C) : 14 students
(D) : 12 students

Correct answer: (A)

Stars produce metals (elements heavier than hydrogen and helium) in their cores during their giant/supergiant phases, up through type Ia/II supernovae explosions. Along with their unused hydrogen, these metals are then scattered into the interstellar medium, which are then incorporated into later generations of stars. An old, early generation star will have metals only in its core, while a young, later generation star will have metals sprinkled in its outer layers.

This was asked previously this semester as a quiz question.

"Difficulty level": 64% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33

Astronomy final exam question: blue main sequence star vs. blue supergiant

Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] A blue main sequence star is known to be smaller than a blue supergiant because it is:
(A) same luminosity as, but cooler than a blue supergiant.
(B) same luminosity as, but hotter than a blue supergiant.
(C) same temperature as, but less luminous than a blue supergiant.
(D) same temperature as, but more luminous than a blue supergiant.

Section 70158
(A) : 11 students
(B) : 8 students
(C) : 41 students
(D) : 1 student

Correct answer: (C)

From Wien's law, the main sequence star and the supergiant must have the same temperature, because they have the same color. From the Stefan-Boltzmann law, for two stars of the same temperature, the less luminous star must be smaller in size.

This was asked previously this semester as a quiz question.

"Difficulty level": 67% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.74

Kudos: Astronomy 210 students, Fall Semester 2008

"Have a fun Holiday P-Dizzle!!!" by Student 3008
Astronomy 210
December 2008
Cuesta College, San Luis Obispo, CA


"Merry X-mas P-dog!!" by Student 7120
Astronomy 210
December 2008
Cuesta College, San Luis Obispo, CA

This is in reference to an Astronomy 210 final exam question.

Kudos/rant: Astronomy 210 student, Fall Semester 2008

"I actually don't mind astronomy" by Student 7120
Astronomy 210
December 2008
Cuesta College, San Luis Obispo, CA

This is in reference to an Astronomy 210 final exam question.

Astronomy final exam question: Ceres as dwarf planet

Astronomy 210 Final Exam, fall semester 2008
Cuesta College, San Luis Obispo, CA

Discuss why Ceres, which orbits in the asteroid belt, is now a dwarf planet under the International Astronomical Union classification scheme.

Solution and grading rubric:

• p :
  Correct. Discuss how Ceres directly orbits the sun (and thus not a moon), and has a rounded shape (and thus not an asteroid), but because it neither has cleared nor dominates its orbit, it is not a planet, but a dwarf planet.
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problematic discussion of IAU classification scheme.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Section 70160
p: 13 students
r: 8 students
t: 6 students
v: 0 students
x: 0 students
y: 3 students
z: 0 students

A sample "p" response, listing the IAU planetary criteria (from student 8187):

Another sample "p" response detailing how the IUA planetary criteria apply to Ceres (from student 4731):

A concise "p" response (from student 3111):

A whimsical "p" response (from student 8945), referring to a "Certificate of Achievement" awarded to each student on the last day of instruction:

A passionate "p" response (from student 0911), relating to fellow dwarf planet Pluto on a personal basis:

A sample "t" response (from student 1186), at least conveying the main idea with an illustration, despite questionable legibility:

Astronomy final exam question: Venus vs. Earth carbon dioxide

Astronomy 210 Final Exam, fall semester 2008
Cuesta College, San Luis Obispo, CA

Discuss why Venus' atmosphere currently has more carbon dioxide than Earth's atmosphere, even though volcanic activity on both planets outgassed the same amount of carbon dioxide. Explain using the properties of greenhouse gases and geological activity.

Solution and grading rubric:

• p:
  Correct. Due to Venus being closer to the sun than Earth, Venus' oceans evaporated and this water vapor contributed to its "runaway greenhouse effect," as there is no way to reduce the carbon dioxide in its atmosphere, compared to Earth's oceans, which do manage to provide a sink for its carbon dioxide.
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May involve plants in addition to oceans.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Garbled discussion, but recognition of related factors such as distance from Sun, mass, temperature, and the greenhouse effect.
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May discuss how certain stars are fainter, or blocked by intervening matter, etc.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Involving unrelated factors.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Section 70160
p: 16 students
r: 3 students
t: 9 students
v: 2 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response, illustrated (from student 1225):
Another sample illustrated "p" response (from student 0911):
A somewhat macabre illustrated "r" response (from student 1083):

Astronomy final exam question: no metal-rich stars in distant galaxies?

Astronomy 210 Final Exam, fall semester 2008
Cuesta College, San Luis Obispo, CA

Discuss why there are no metal-rich stars observed in the extremely distant galaxies that can be observed. Explain your answer using the properties of stars and light.

Solution and grading rubric:

• p:
  Correct. Discusses "look-back time," where the finite speed of light makes distant objects appear as they did in the past; and how the first generation of stars would be nearly hydrogen only, and contain very few metals.
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. At least understands nucleosynthesis process of metal-poor to metal-rich subsequent generations of stars.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors.
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May discuss how certain stars are fainter, or blocked by intervening matter, etc.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Section 70160
p: 10 students
r: 6 students
t: 0 students
v: 12 students
x: 0 students
y: 2 students
z: 0 students

A sample "p" response (from student 6789):
A sample "r" response (from student 4207), only implying lookback time, but understanding the element-building process of subsequent star generations:
A series of sample "p" responses showing the ingenuity and creativity (here, from student 0911) in illustrating the finite speed of light and nucleosynthesis:
(..and from student 1208):
(...and lastly from student 1225):

Education research: preliminary MPEX comparison (Cuesta College, Fall Semester 2008)

The Maryland Physics Expectations survey (MPEX) was administered to Cuesta College Physics 205A (college physics, algebra-based, mandatory adjunct laboratory) students at Cuesta College, San Luis Obispo, CA. The MPEX was given during the first week of the semester, and then on the last week of the semester, to quantify student attitudes, beliefs, and assumptions about physics using six question categories, rating responses as either favorable or unfavorable towards:

1. Independence--beliefs about learning physics--whether it means receiving information or involves an active process of reconstructing one's own understanding;
   
2. Coherence--beliefs about the structure of physics knowledge--as a collection of isolated pieces or as a single coherent system;
   
3. Concepts--beliefs about the content of physics knowledge--as formulas or as concepts that underlie the formulas;
   
4. Reality Link--beliefs about the connection between physics and reality--whether physics is unrelated to experiences outside the classroom or whether it is useful to think about them together;
   
5. Math Link--beliefs about the role of mathematics in learning physics--whether the mathematical;
   formalism is used as a way of representing information about physical phenomena or mathematics is just used to calculate numbers;
   
6. Effort--beliefs about the kind of activities and work necessary to make sense out of physics--whether they expect to think carefully and evaluate what they are doing based on available materials and feedback or not.

Cuesta College
Physics 205A Fall Semester 2008 sections 70854, 70855
(N = 30, matched pairs, 
         excluding negative informed consent form responses)

Percentage of favorable:unfavorable responses
        Overall Indep.  Coher.  Concept Real.   Math    Effort
Initial 56:22   47:14   45:32   52:27   66:13   55:20   71:12
Final   51:28   44:24   53:25   49:35   68:11   42:35   52:27

Perhaps most notable this semester is a higher gain in coherence, no loss in reality, and a smaller losses in concept and effort compared to previous semesters. Unique to this semester, compared to previous semesters was not just the mere implementation of electronic response system "clickers" (Classroom Performance System, einstruction.com), but the use of known best practices of using clickers (i.e., "think-(pair)-share"), from current education research. More analysis on the impact of using clickers on this introductory astronomy class will be forthcoming on this blog.

Previous posts:

• Education research: preliminary MPEX comparison (Cuesta College, Spring Semester 2008)
  
• Education research: preliminary MPEX comparison (Cuesta College, Fall Semester 2007)
  (More detailed discussion on interpreting historical MPEX results at Cuesta College.)
  
• Education research: student expectations in physics
  (Background on the MPEX by E. F. Redish, J. M. Saul, and R. N. Steinberg.)

Astronomy final exam question: life on massive main sequence star exoplanets

Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] Why are planets that orbit massive main sequence stars not thought to be good candidates for life to exist?
(A) Massive main sequence stars are too luminous.
(B) Massive main sequence stars have short lifetimes.
(C) These planets would be geologically dead.
(D) These planets would be too large.

Section 70160
(A) : 1 students
(B) : 27 students
(C) : 2 students
(D) : 0 students

Correct answer: (B)

Massive star have main sequence lifetimes on order of millions of years (or even less), much less than how biological life arose from chemical evolution arose on Earth (on order of billions of years), with the caveat that this process would take the same amount of time elsewhere.

"Difficulty level": 91% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25

Astronomy final exam question: stellar distances

Astronomy 210 Final Exam, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] ε Eridani is a star that has an apparent magnitude m = +3.72 and an absolute visual magnitude M_V = +6.2. Approximately how far away is ε Eridani from Earth?
(A) Much farther away than 10 parsecs.
(B) A little farther away than 10 parsecs.
(C) Exactly 10 parsecs away.
(D) Closer than 10 parsecs away.

Section 70160
(A) : 6 students
(B) : 3 students
(C) : 0 students
(D) : 13 students

Correct answer: (D)

When brought to the "fair distance" of 10 parsecs (thus changing its apparent magnitude to absolute visual magnitude), ε Eridani now seems to be dimmer, indicating that it must have moved away to the Earth during this process. Thus ε Eridani must be closer than this fair distance of 10 parsecs.

"Difficulty level": 73%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

"P-dog" scribble

"P-dog" by L. M.
Astronomy 210L
Fall Semester 2008
Cuesta College, San Luis Obispo, CA

This doodle was found on the back of an introductory astronomy exam, presumably a caricature of the instructor.

Physics quiz question: thermal contraction of opening in metal plate

Physics 205A Quiz 7, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Conceptual Question 13.4

[3.0 points.] A square opening is made in a metal plate. The metal plate is cooled down from room temperature to a final temperature of 100 K. What happens to the size of the square opening as the metal plate cools down?
(A) The square opening becomes smaller.
(B) The square opening becomes larger.
(C) The square opening remains the same size as before.
(D) (Not enough information is given.)

Correct answer: (A)

All dimensions in a rigid object will contract proportionally when cooled (and expand proportionally if heated).

Student responses
Sections 70854, 70855
(A) : 26 students
(B) : 8 students
(C) : 2 students
(D) : 0 students

"Difficulty level": 72%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60

Physics quiz question: mass, moles and molar mass of He

Physics 205A Quiz 7, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 1/e, Problem 13.36

[3.0 points.] How many grams of He atoms are there in 5.0 moles?
(A) 0.80 g.
(B) 1.3 g.
(C) 6.8 g.
(D) 20 g.

Correct answer: (D)

The molar mass of He is 4.0 unified atomic mass units; that is, there are 4.0 g per mole of He atoms. Since there are 5.0 moles of He atoms, then there are 20 g of He atoms. Response (A) is 4.0/5.0; response (B) is 5.0/4.0; response (C) is 4.0*1.7 (in reference to another sample of 1.7 moles of Ne atoms discussed in a later, related question).

Student responses
Sections 70854, 70855
(A) : 6 students
(B) : 5 students
(C) : 2 students
(D) : 23 students

"Difficulty level": 63%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.49

Astronomy quiz question: Mars' shield volcanoes

Astronomy 210 Quiz 7, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] Shield volcanoes on Mars appear to be caused by:
(A) oceans, when it was younger.
(B) runaway greenhouse effect.
(C) heavy bombardment.
(D) vertical motion of magma under the crust.

Section 70158
(A) : 7 students
(B) : 8 students
(C) : 3 students
(D) : 33 students

Correct answer: (D)

Magma flowing up through hot spots in the thick, static crust of Mars have built up large shield volcanoes on Mars.

"Difficulty level": 74% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.62

Astronomy quiz question: cause of plate tectonics

Astronomy 210 Quiz 7, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] What causes Earth's plate tectonics?
(A) Convection currents underneath the crust.
(B) Tidal forces from the moon.
(C) Gradual slowing rotation.
(D) Asteroid impacts that cracked the crust.

Section 70160
(A) : 28 students
(B) : 1 student
(C) : 0 students
(D) : 1 student

Correct answer: (A)

Lateral mantle flow below pulls the crust in certain directions; hot, rising magma produces new crust formation at midocean rifts; while cool, sinking magma occurs at subduction zones.

"Difficulty level": 94% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.13

Section 70158
(A) : 59 students
(B) : 4 students
(C) : 4 students
(D) : 1 student

"Difficulty level": 88% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33

Astronomy quiz question: IAU classification scheme for asteroids

Astronomy 210 Quiz 7, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[4.0 points.] Listed below are the minimal qualifications established by the International Astronomical Union for a planet:

• I. Orbits the sun.
• II. Shape "rounded-out" by gravity.
• III. Cleared/dominates orbit around sun.

Which of these qualifications are met by an asteroid?
(A) I only.
(B) II only.
(C) III only.
(D) Both I and II.
(E) Both II and III.
(F) Both I and III.
(G) (None of the above choices.)

Section 70160
(A) : 15 students
(B) : 1 student
(C) : 1 student
(D) : 2 students
(E) : 3 students
(F) : 2 students
(G) : 6 students

Correct answer: (A)

Asteroids orbit the sun, typically between Mars and Jupiter. However, they are irregularly shaped (if they were spherical, they would be dwarf planets), and they have not cleared out nor dominate their orbits (if they did, they would be planets).

"Difficulty level": 55% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.88

Education research: SPCI gains (Cuesta College, Fall Semester 2008)

The Star Properties Concept Inventory (SPCI, developed by Janelle Bailey, University of Nevada-Las Vegas) was administered to Astronomy 210 (one-semester introductory astronomy) students at Cuesta College, San Luis Obispo, CA during the last week of instruction, at both the main San Luis Obispo campus and the North County campus at Paso Robles.

     Cuesta College    Cuesta College
     Astronomy 210     Astronomy 210
     SLO campus        NC campus
     Fall Semester     Fall Semester
     2008              2008
N    66 students*      26 students*
low   4                 6
mean 10.7 +/- 3.0      12.5 +/- 3.3
high 17                17

*Excludes students with negative informed consent forms (*.pdf), the use of which is discussed in a previous post.

A "Student" t-test of the null hypothesis results in p = 0.013, thus there is a significant difference between students at these two Cuesta College campuses. In comparison, the t-test of pre-test scores from both campuses was p = 0.28, which was not significant.

The averages for each section of the initial and final SPCI scores (given as percentages, with standard deviations), as well as the Hake normalized gain <g> are given below:

Astronomy 210 Fall Semester 2008 section 70158 (SLO campus)
<initial%> = 29% +/- 12% (N = 86)
  <final%> = 47% +/- 12% (N = 66)
       <g> = 0.23 +/- 0.18 (matched-pairs); 0.24 (class-wise)

Astronomy 210 Fall Semester 2008 section 70160 (NC campus)
<initial%> = 32% +/-  9% (N = 32)
  <final%> = 54% +/- 14% (N = 26)
       <g> = 0.32 +/- 0.19 (matched-pairs); 0.33 (class-wise)

For this NC campus section, this Hake gain is greater than previous gains for introductory astronomy classes, as discussed in previous posts on this blog.

Notable about both these Astronomy 210 classes at Cuesta College this semester is not just the mere implementation of electronic response system "clickers" (Classroom Performance System, einstruction.com), but the use of known best practices of using clickers (i.e., "think-(pair)-share"), from current education research. However, there seemed to have been much more peer-interaction in the smaller NC campus class than in the larger, "diffuse" SLO campus. More analysis on the impact of using clickers on this introductory astronomy class will be forthcoming on this blog.

For earlier results at Cuesta College and further discussion of the SPCI, see previous posts:

Education research: SPCI gains (Cuesta College, Spring Semester 2006-Spring Semester 2007).

Education research: SPCI gains (Cuesta College, Summer Session 2007).

Education research: SPCI gains (Cuesta College, Fall Semester 2007).

Education research: SPCI gains (Cuesta College, Spring Semester 2008).

FCI post-test comparison: Cuesta College versus UC-Davis

Students at both Cuesta College (San Luis Obispo, CA) and the University of California at Davis were administered the Force Concept Inventory (Doug Hestenes, et al.) during the last week of instruction, in order to follow up on the pre-test results from the first week of instruction (which showed no statistical difference between pre-test scores).

     Cuesta College    UC-Davis
     Physics 5A        Physics 7B
     Fall Semester     Summer Session II
     2008              2002
N    33 students       76 students
low   6                 3
mean 14.0 +/- 5.0      12.9 +/- 5.5
high 27                26

A "Student" t-test of the null hypothesis results in p = 0.0077, thus there is a significant difference between Cuesta College and UC-Davis FCI post-test scores.

The pre- to post-test gain for this semester at Cuesta College is:

Physics 205A Fall Semester 2008 sections 70854, 70855
<initial%> = 30% +/- 20% (N = 53)
  <final%> = 53% +/- 18% (N = 33)
       <g> = 0.29 +/- 0.24 (matched-pairs); 0.33 (class-wise)

This Hake gain is greater than previous gains for algebra-based introductory physics at Cuesta College (0.21-0.23), UC-Davis (0.16), and for calculus-based introductory physics at Cuesta College (0.14-0.16), as discussed in previous postings on this blog.

Notable about this Physics 205A class at Cuesta College is not just the mere implementation of electronic response system "clickers" (Classroom Performance System, einstruction.com), but the use of known best practices of using clickers (i.e., "think-(pair)-share"), from current education research. More analysis on the impact of using clickers on this introductory physics class will be forthcoming on this blog.

Previous FCI results:

• Cuesta College versus UC-Davis, Spring semester 2008 pre-tests and post-tests.
• Cuesta College versus UC-Davis, Fall semester 2007 pre-tests and post-tests.

Extraterrestrial hypothesis tryptich

081206-1060907-invert
http://www.flickr.com/photos/waiferx/3087116819/
Originally uploaded by Waifer X

081206-1060910-invert
http://www.flickr.com/photos/waiferx/3087119633/
Originally uploaded by Waifer X


081206-1060911-invert
http://www.flickr.com/photos/waiferx/3088597420/
Originally uploaded by Waifer X

Dramatizations of the original 1974 Arecibo message, the Drake equation, and the purported 2001 Chibolton crop circle "reply."

Erasing slate: like life?

"If only life was like erasing slate." by Anonymous
December 1, 2008
Cuesta College, San Luis Obispo, CA

Latest scribbling on the lift-and-erase slate in the hallway, outside the office door.

Astronomy midterm question: no-center universe expansion

Astronomy 210 Midterm 2, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss why the expansion for the universe has no center, using observations and evidence related to the Hubble law in your explanation.

Solution and grading rubric:

• p = 20/20:
  Correct. Argument involves redshifts (and thus recession velocities) being proportional to distances (i.e., Hubble's law), and how this implies that there is no unique center, any other galaxy would observe a similar Hubble's law. May also invoke no-edge, no-center argument of an non-finite universe.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors.
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 23 students
r: 3 students
t: 2 students
v: 2 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response, discussing Hubble's law (from student 1225):

Another "p" response, discussing "Cosmic Haterade" (from student 7120):

Astronomy midterm question: star cluster age

Astronomy 210 Midterm 2, Fall Semester 2008
Cuesta College, San Luis Obispo, CA

[20 points.] Shown at right is an H-R diagram of a star cluster, where all of these stars have the same age. Discuss whether this star cluster is very young or is very old, and explain why.

Solution and grading rubric:

• p = 20/20:
  Correct. Massive stars evolve quickly, and have already gone through their main sequence lifetimes to the supergiant stage, so this cannot be a very young star cluster. Low mass stars evolve slowly, so for these stars to have reached the main sequence, this must be a very old star cluster.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. May state that this is a young star cluster, but understands how massive and low mass stars evolve differently.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Uses other criteria to determine age of star cluster.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 14 students
r: 1 student
t: 11 students
v: 3 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response, discussing the "house party" analogy of how stellar evolution rates depend on mass (from student 3089):