Learning Critical Thinking Through Astronomy, Week 12

I’m finally getting a bit ahead this week.

This week is all about lunar illumination and Activity0303. This activity is interesting in that students frequently change the questions on the activity to match what they want to be asked rather than what I’m asking them. It’s quite predictable, which could possibly mean my questions are defective but I think it means I have latched onto their psyches somehow. Either way, it’s entertaining.

I have decided to completely remove the existing Section 2 and replace it with a kinesthetic activity with styrofoam balls and a bright light bulb. It’s traditional, but I have yet to find something better, especially when framed as in the first part of the activity.

I want students to understand that Moon’s visual appearance is always a combination of the side that’s illuminated and the side that isn’t illuminated. Some combination of those two sides always faces Earth. There are no shadows involved. Yes, one could make the argument that Moon’s unilluminated side lies inside Moon’s own shadow, but I can only recall one instance of a student pointing that out. Most students insist that Earth’s shadow somehow “blocks” something.

Later this week, we will informally extend this activity into modeling solar and lunar eclipses.

Incidentally, speaking of blocking light, we as astronomy instructors need to be more careful with the distinction between eclipses and occultations. The former doesn’t involve anylight being physically blocked, while the latter does. The relative angular sizes of the objects involved plays a role in how the phenomenon is named. An eclipse is when one object stands in another object’s shadow. An occultation is when light from one object is physically blocked by another object. Unfortunately (or perhaps fortunately), this means that what we typically call a “solar eclipse” isn’t that at all; it’s really either an Earth eclipse (Earth stands on Moon’s shadow) or a solar occultation (Sun is occulted by Moon). I think the distinction is important because different physical mechanisms should have different names. I can just hear Arnold Arons saying that. I know…pedantic again, but I’ll take it. Someone has to point this stuff out. The astronomy community certainly doesn’t.

Comments and feedback welcome.


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