Multiple Choice Items:

1. In which moon phase is a solar eclipse possible?

1. Full

2. New

3. Third Quarter

4. Waxing Gibbous

2. Which pair of moon phases are associated with Spring tides?

1. any phase during spring

2. Third Quarter and New

3. First Quarter and Third Quarter

4. Full and New

3. Which best describes an astronomical unit?

6. the mean distance between the Earth and the sun

7. a large amount of money

8. the distance light travels in a year

9. the distance between the sun and Polaris

4. How far does the gravitational influence of the sun reach?

11. to the edge of the solar system

12. to the dwarf planet Eris

13. until canceled by another star

14. until the orbit of Neptune

5. How are the inner planets and the outer planets different?

16. The inner planets are gas giants, the outer planets are rocky.

17. The inner planets are rocky, the outer planets are gas giants.

18. The inner planets are much larger than the outer planets.

19. The inner planets have more moons than the outer planets.

6. Moon Alpha and Moon Beta orbit the same planet. Beta is twice as far from the planet as Alpha. How much gravitational attraction does the planet exert on Beta, compared to Alpha?

20. half as much

21. twice as much

22. the same amount

23. a quarter as much

Multiple-Choice Answer Key:

Short Answer Items:

7. You are designing a space probe to visit an asteroid just beyond the orbit of Mars. In fact the asteroid is exactly twice as far from the sun as the Earth. You know that, like gravity, radiation received from the sun falls off as you get farther from the sun in the same inverse-squared ratio. The probe needs 200 watts, and you have a solar panel that has proven in tests that it can generate 200 watts when facing the sun from Earth’s orbit. How many of these panels will you need to generate the same 200 watts when the probe has reached the asteroid?

8. Sometime in the future you are working as an editor for a book publishing company. Someone who is a space pilot for one of the new colonies on the moon has submitted a manuscript making dramatic claims that aliens from another star are closely watching what humanity is doing in space. Among other things, he says that on one standard four-day trip to Earth’s moon he decided to take his rocket on a side trip to Jupiter to meet with the aliens, and then returned to the moon before he was missed. Do you decide to believe his story and accept the book for publication? Or do you reject the book because you don’t believe his story? Give your reason for your decision.

Short-Answer Key and Scoring Rubrics:

Question 7 Scoring Rubric:

Question 8 Scoring Rubric:

Performance Assessment:

As the planetary astronomy professor at your local university some decades from now, you are in your office when you get a message from a correspondence student, currently on Mars, claiming to have overheard a discussion there of the discovery of two additional Martian moons. They are no bigger than the two previously known moons of Mars, tiny Phobos and Deimos, but are in different orbits with different orbital periods. The student has already named them Alpha and Beta, and has heard that their orbital characteristics around Mars are like this:

	Orbital Distance (in planet diameters)	Orbital Period (hours)
Alpha	3	10
Beta	5	21.5

You wonder if this could be true. You know that Kepler’s Third Law, where D³ = P² (orbital distance cubed equals orbital period squared) can be applied to the moons orbiting a specific planet, as well as planets orbiting the sun. Of course, the law refers to ratios rather than absolute values, so you recalculate the orbital characteristics of Alpha and Beta in terms of a ratio based on the orbit of Alpha. You add a column dividing D³ by P². If the result is close to 1 for Beta, that means the D³ = P² ratio holds true, the two moons do follow Kepler’s law, and therefore could be real.

	Orbital Distance (in planet diameters)	Orbital Period (hours)	D3/P2
Alpha	1 (3/3)	1 (10/10)	1
Beta	1.66 (5/3)	2.15 (21.5/10)	0.99 (1.663 = 4.5743 and 2.152 = 4.62, so 4.57/4.62 = 0.99)

Wildly excited by the results, you compose a tweet announcing this to your many avid followers. (In the future, planetary astronomy is considered glamorous.) Your blogosphere immediately erupts with arguments for and against the validity of the new discovery. There are six themes in the responses:

9. The orbital data for Alpha and Beta match those of two fictional Martian moons mentioned in Gulliver’s Travels, a political satire written in 1726 by Jonathan Swift.

10. Considering #1, the graduate student may have overheard a conversation about the book. The fact that the data concerning Swift’s moons fit Kepler’s Third Law must be a coincidence.

11. On the contrary, the fact that the data for the moons fits Kepler’s Third Law proves they are real.

12. It is not possible that Alpha and Beta could been gone undetected this long, especially now that we have regular travel to Mars.

13. Numbers do not lie. Professional jealousy must have kept astronomers from acknowledging Swift’s discovery after Phobos and Deimos were discovered in 1877.

14. Numbers do not lie, and therefore D³/P² should give similar results for Alpha and Beta when calculated with data for Phobos and Deimos, sincethey are in the same Martian gravity. At least that should be the case if Alpha and Beta are real.

Deciding to follow up on #6, you dig out the orbital data for Phobos and Deimos. (The names, incidentally, mean Fear and Terror, those being the attendants of Mars, god of war.) You recalculate the data for all the moons as ratios of the orbit of Phobos, which you know to be a real moon whose orbit is a product of real gravity. The question is whether the orbits of Alpha and Beta are products of that same Martian gravity, or fictional gravity.

After examining this last chart, what announcement do you make concerning Alpha and Beta? What reasons do you give? You can cite any data in the spreadsheets and use any arguments that surfaced in the blogosphere.

Performance Assessment Scoring Rubric: