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## 03 May 2011

### Basic astronomy unit in general physics -- can you help me?

For most of a decade I've been teaching a three-week "astronomy" unit to my general physics class.  The students are generally excited by the idea of learning astronomy, which is a boon to the teacher of a class of seniors in May.

My inspiration for the unit was a one-week summer course I took at the University of Montana called "The Celestial Navigation of Lewis and Clark."  Burrito Girl (my wife and sidekick) and I spent a week learning how to use a sextant, and how to determine latititue and longitude from the sextant reading.  We also visited some sites where L&C actually made camp, there finding National Park Service employees giving demonstrations of period instruments.

*It was a bit disappointing to learn that the celestial observations that L&C diligently recorded throughout their trip proved to be essentially worthless.  By far the more accurate map of their journey was reconstructed from Clark's "dead reckoning" intuitive estimates of travel distances as recorded in his log.

The first day of class consisted of a crash course on local astronomy -- nightly and yearly motions of the sun, moon, and stars.  Though the terminology ("celestial equator," "ecliptic") was new to me, the general concepts were not new -- for example, stars, including the sun, apparently rotate counterclockwise around the north star.    To the majority of the class, though, who were not physicists, these ideas of motions of the stars and planets WERE new and difficult.  Even in their final presentation, a group of classmates indicated that the sun would be directly overhead in Montana at noon on June 21.  Oops.  I thought it might be useful for me to teach my classes some of these basics.

Between the material from the U Montana course and some exercises I picked up from a CAPER* workshop, I took three weeks to cover:

*CAPER stands for Conceptual Astronomy and Physics Education Research. "Teams" of astro professors at several university work under this umbrella. At an AAPT meeting I picked up some of their "lecture tutorials," which have been most useful in this unit. Much of this sort of work is online -- search under "CAPER."

* motion of the earth, moon, and sun
* apparent motion of the stars
* measuring stellar distances with parallax
* use of a sextant to determine longitude and latitude

My fundamental goal is to bust the standard misconceptions.  If nothing else, I want students to know that seasons don't depend on the earth's distance from the sun, and that moon phases are NOT a result of earth's shadow.  Just getting this much retention is more difficult than you might imagine.

We culminate the unit with a nighttime observing session.  That's easy to arrange at a boarding school -- we just gather behind the dorms after lights out.  We use Starry Night software on a laptop, or Star Walk on an iPad, to help deterime what we're looking at.

What about homework assignments?  Well, I do assign homework.  Many of the problems are based on end-of-chapter questions in the two astro textbooks I have.  These are based on what we did in class, but sometimes thought provoking -- "How high will the sun be at noon on June 21 at our latitude?"  "Star A is measured to move at most 2 arcseconds in relation to the fixed stars over the course of a year.  How many light years away is this star?"  "Using a map but not online search tools, choose an American city in which the sun sets as late as possible."

Your help?  I want to find multiple choice quesitons for quizzing and testing purposes.  For standard physics topics, I have AP and Regents and SATII and Physics Bowl test banks.  These provide a virtually limitless source of multiple choice ideas.  But for astronomy, I've only found a few online sources -- and these have been pretty danged lousy.

Can anyone point me to a well written bank of multiple choice questions based on basic astronomy concepts?  I can and have written some of my own questions, but I always like to have some external validation for what I'm doing.  Post a comment, or email.  And a future post will discuss the observing session -- assuming it's not clouded out for the third year in a row.

GCJ