Leap year day t-shirts

Optical Illusion of Leap Year, by haxrox
shirt.woot.com

Several clever entries from Design Derby #30: Leap Year T-shirts at shirt.woot.com.

Come on Earth! Pick Up the Pace!, by KLSwoot
shirt.woot.com

Do the Math (First place derby winner) by Iambusyeating
shirt.woot.com

The cheerleader effect, part II

Colorado State University Cheerleaders
NBC Sports

Not exactly a true inverted pyramid (the top two cheerleaders are not standing on the shoulders of the bottom cheerleader, but a nice visual to motivate why the inner core of the Earth is hot, yet solid. See previous post discussing the "Cheerleader Effect" (hydrostatic equilibrium).

Sunshine vs. Little Miss Sunshine

Photoshop Phriday: Before and After Movies III, by Fenring
February 22, 2008
somethingawful.com

Astronomy midterm question: retrograde Mars

Astronomy 10 Midterm 1, spring semester 2008
Cuesta College, San Luis Obispo, CA

An observer in San Luis Obispo, CA notices that Mars is on the meridian at midnight. Discuss whether Mars is undergoing prograde (proper) or retrograde motion with respect to the background stars on that night. Explain your answer using a diagram showing the positions and motions of an observer, Mars, and Earth.

Solution and grading rubric:

• p:
  Correct. Draws heliocentric orbits of Mars (outer) and Earth (inner), with Mars being on the meridian of a midnight observer located on Earth. Since Mars is at opposition, Earth is in the process of "lapping" it, resulting in Mars appearing to move retrograde (east-to-west, "backwards") with respect to the background stars. Diagram and discussion consistent, with some minor details omitted.
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Diagram problematic/incomplete (e.g. Mars' orbit inside Earth's, or observer missing), but demonstrates some understanding of relative orbital motion and prograde/retrograde motion with respect to the background stars.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Some attempt at explaining the "lapping" illusion to motivate retrograde discussion. May conclude prograde but diagram is otherwise correct.
  
• 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 distributions:
Section 4160
p: 15 students
r: 4 students
t: 5 students
v: 14 students
x: 1 student
y: 0 students
z: 0 students

Section 5166
p: 18 students
r: 4 students
t: 9 students
v: 35 students
x: 0 students
y: 0 students
z: 1 student

A sample "p" response (from student 1316):
This "p" response (from student 2431) explicitly shows the changing line-of-sight that Mars makes as it is "lapped" by Earth, resulting in retrograde motion with respect to the background stars:
Another "p" response (from student 2887), with anthropomorphized celestial bodies:

Astronomy midterm question: total lunar eclipse

Astronomy 10 Midterm 1, spring semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q2.4

At 7:30 PM at night, you are currently observing a total lunar eclipse in San Luis Obispo, CA. Suppose you decided to call a friend who lives in Seattle, WA, which is north of San Luis Obispo, CA. Explain what kind of eclipse (if any) your friend would be able to see in Seattle, WA at the same time, or why not, using a diagram of Earth, the moon, and shadow zones. Assume that the skies are clear in both San Luis Obispo, CA and Seattle, WA.

Solution and grading rubric:

• p:
  Correct. Clear and correct diagram of the observer, Earth, the moon and the sun shown. For a total lunar eclipse, the moon is completely in the umbra of Earth. All observers on the night side of Earth will be able to see this total lunar eclipse. Note that a total penumbral lunar eclipse may be discussed instead, as long as all observers on the night side of Earth see the same thing.
  
• 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. Earth-moon-sun diagram is essentially correct (showing a total lunar eclipse), but argument is based on observers being in different shadow zones, which is not possible, as all observers on the night side of Earth are in the umbra of Earth.
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Serious but flawed attempt at an Earth-moon-sun diagram, with major inconsistencies or errors, typically showing a total/partial/annular solar eclipse.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distributions:
Section 5166
p: 27 students
r: 4 students
t: 16 students
v: 18 students
x: 2 students
y: 0 students
z: 0 students

Notably this midterm was given during the umbral phase of the February 20, 2008 total lunar eclipse! Some students who had finished early were able to go outside and make Danjon L-scale ratings of the darkness of the umbral shadow on the Moon.

A sample of a "p" response (from student 0429) is shown below, clearly showing that observers in Seattle, WA and San Luis Obispo, CA would both see the Moon in the umbra of Earth:
Another "p" response (from student 1207) more elaborately illustrating the relevant geography:
Yet more elaborate geography in another "p" response (from student 1652):
An extended "p" response covering both total and partial lunar eclipse cases (from student 1886):

Astronomy midterm question: 18-hour work day

Astronomy 10 Midterm 1, spring semester 2008
Cuesta College, San Luis Obispo, CA

It is remarked that if you are busy in Ukraine, you would typically work from sunrise to moonrise[*]. Discuss what phase the moon would have when rising to signal the end of an approximately 18 hour work shift that began at sunrise. Support your answer using a diagram showing the positions of the sun, moon, Earth, and an observer on Earth.

[*] The Week, volume 5, issue 212, p. 48-49.

Solution and grading rubric:

• p:
  Correct. Assuming sunrise at 6 AM, then end of an 18 hour work shift would be at 12 AM midnight. "Phase 7," or the "third quarter moon," or the "last quarter moon" would rise at midnight.
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. At least clearly indicates that end of workshift is midnight, but has slightly incorrect phase for moonrise on east horizon at that time.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. As (r), but chooses full moon, which is directly overhead at midnight.
  
• 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 distributions:
Section 4160
p: 10 students
r: 4 students
t: 12 students
v: 12 students
x: 1 student
y: 0 students
z: 0 students

A sample of a "p" response (from student 2887) is shown below:
Another "p" response (from student 4607) decries the hardships of the Ukraine work ethic:

Overheard: quiz before or after long weekend?

Physics 5A, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Physics 5A (college physics, algebra-based) at Cuesta College during Spring semester 2008 meets Mondays, Wednesdays, and Fridays. Quizzes (and midterms) are scheduled on Fridays. However, due to students getting both Friday and Monday off for a four-day weekend(!) to celebrate both Lincoln's and Washington's birthdays separately, the quiz normally scheduled for that Friday was moved forward to the preceding Wednesday, instead of the following Wednesday.

Conversation on the Monday before the quiz:

Student: "Why can't the quiz be pushed back to after the four-day weekend?"

Instructor: "If you're not ready for this quiz before this four-day weekend...you won't be ready for the quiz after the four-day weekend."

Valentine Dome, on Valentine Moon

Flickr.com: IMGP1525.JPG
Originally uploaded by Waifer X
February 14, 2008

Hand-held Pentax Optio S40, eyepiece projection shot through Orion SkyQuest 10" Newtonian reflector, Dobsonian mount, cropped to remove (most) vignetting. Mare Imbrium on the upper left, Mare Vaporum on the lower left, and Mare Serenitatis on the right, featuring the Valentine Dome (barely resolved). Fair-to-good seeing conditions at Cuesta College North County Campus, Paso Robles, CA. Click on the photo link for geographic (lunagraphic?) annotations.

Astronomy clicker question: telescope site selection

Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal M1.4

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the end of their learning cycle:

[0.3 points.] Which one of the following choices best describes the least important consideration that astronomers look for when evaluating an observing site for a given electromagnetic radiation telescope?
(A) How clear the weather is at the site.
(B) How much atmospheric turbulence there is at the site.
(C) How far away the site is from Earth-based sources of that form of electromagnetic radiation.
(D) How transparent the atmosphere is to that form of electromagnetic radiation.
(E) How cold the temperature is at the site.

Correct answer: (E)

Students invariably make comments along the lines of, "astronomers can suck it up," when it comes through working in cold conditions.

Student responses
Section 4160
(A) : 0 students
(B) : 0 students
(C) : 0 students
(D) : 0 students
(E) : 30 students

Astronomy clicker question: most dangerous photon

Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal M1.1

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the beginning of their learning cycle:

[0.3 points.] Which type of light ("electromagnetic radiation") particle is the most dangerous to be exposed to?
(A) A gamma ray photon.
(B) An x-ray photon.
(C) A microwave photon.
(D) (Each of these light particles (A)-(C) are equally dangerous.)

Correct answer: (A)

The energy of a photon is inversely dependent on wavelength; the gamma ray photon is the shortest wavelength of these photons, while the microwave photon has the longest wavelength. Many students explain picking gamma ray photons because of the origins of the Incredible Hulk. There may still be a concern with long-exposure to microwave photons, even though they contain the least amount of energy per particle, due to the number of photons involved.

Student responses
Section 4160
(A) : 19 students
(B) : 2 students
(C) : 1 student
(D) : 7 students

Section 5166
(A) : 26 students
(B) : 5 students
(C) : 3 students
(D) : 17 students

Astronomy clicker question: planet-hunting

Astronomy 10, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q3.1

Students were asked the following clicker question (Classroom Performance System, einstruction.com) at the end of their learning cycle:

[0.3 points.] How can you determine if a bright object in the sky is a planet (and not a star), without using a telescope?
(A) If it does not twinkle.
(B) If it does not show up on a starwheel.
(C) If it does not appear in exactly the same location in the sky each night.
(D) (All of the above choices (A)-(C).)

Correct answer: (D)

The large angular diameter of planets make them less susceptible to atmosphere turbulence, so they do not seem to "twinkle" like point-like stars (response (A)). Planets also move with respect to the background stars as they (and the Earth) move around the Sun, and thus cannot be permanently positioned on a starwheel (responses (B) and (C)). Thus the most correct, inclusive answer is (D).

Student responses
Section 4160
(A) : 6 students
(B) : 1 student
(C) : 10 students
(D) : 13 students

Astronomy quiz question: Moon rise times

Astronomy 10 Quiz 2, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q2.2

[3.0 points.] An observer in San Luis Obispo, CA observes that the Moon rises in the east at exactly 6:00 PM. Which one of the following choices best describes the time that the Moon will rise in the east, on the following evening?
(A) Nearly an hour earlier than 6:00 PM.
(B) Exactly 6:00 PM.
(C) Nearly an hour later than 6:00 PM.
(D) (It cannot be determined when the Moon will rise the following evening, unless the date/season is given.)
(E) (It is impossible in San Luis Obispo, CA for the Moon to rise at 6:00 PM.)

Correct answer: (C)

As seen from above, the Moon revolves counterclockwise in its approximately 29 day-orbit around the Earth, while the Earth rotates counterclockwise in approximately 24 hours. Thus the Moon will have moved approximately 1/29th further along its orbit by the time an observer on the Earth notices it is rising again, and thus the Moon will appear to rise slightly later each consecutive day.

Student responses
Section 4160
(A) : 8 students
(B) : 5 students
(C) : 16 students
(D) : 9 students
(E) : 1 student

Student responses
Section 5166
(A) : 12 students
(B) : 13 students
(C) : 28 students
(D) : 12 students
(E) : 1 student

Astronomy quiz question: monthly solar and lunar eclipses

Astronomy 10 Quiz 2, Spring Semester 2008
Cuesta College, San Luis Obispo, CA

Astronomy 10 learning goal Q2.4

[3.0 points.] Which one of the following choices best describes what would happen if the orbit of the Moon around the Earth was not tilted with respect to the orbit of the Earth around the Sun?
(A) There would never be any solar or lunar eclipses of any type.
(B) There would only be annular solar eclipses, and partial lunar eclipses.
(C) There would be a solar eclipse and a lunar eclipse every month.
(D) The Moon would then always block the Sun, making a permanent solar eclipse.
(E) The Earth would then always be between the Sun and Moon, making a permanent lunar eclipse.

Correct answer: (C)

The reason why there is no solar eclipse and lunar eclipse every month is that the orbit of the Moon around the Earth is tilted, such that the new Moon does not usually pass directly between the Sun and the Earth, and the full Moon does not usually pass directly between the Earth and the Moon.

Student responses
Section 4160
(A) : 4 students
(B) : 6 students
(C) : 25 students
(D) : 1 student
(E) : 3 students

Student responses
Section 5166
(A) : 5 students
(B) : 6 students
(C) : 50 students
(D) : 3 students
(E) : 2 students