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Classdome March 2015
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From the Classdome

March 2015

Updating classroom lessons

We are deep in the “testing season” at our school, where it is almost as wild and crazy as football season. It also provides me with a 3-week window to update and edit presentations before the end-of-school-year push.

I have observed this school year that a couple of my presentations have some dated information or use techniques that are not as engaging as it should be for the students.

One of my presentations getting a lot of my time this break is my lesson on meteors, asteroids, meteorites, meteoroids, and comets. The information hasn’t really changed and there isn’t a new definition for asteroid.

The issue is that it doesn’t mention recent events, like how to say Chelyabinsk, and I felt the use of the word bolide for 6-8 grade students was a bit extreme. I don’t have to rewrite the entire presentation; I just need to adapt the sections with the problems and re-render them.

Working on gravity

One of the other lessons that is getting some time from me is the one on gravity. I have worked with Dr. Siobahn Morgan at the University of Northern Iowa’s AJJAR resources ( for many years, I even got to be one of the field testers of a couple of the Kepler’s Law simulators.

The simulators are simple enough for my younger students to use without an issue, yet give enough accurate information for reliable simulation.

 The issue has been that they are Java-based and periodically need updates and permissions to function. If you are running it as a kiosk the changes in plugins and addons aren’t that bad, but I am running a lab with 30 computers that at any moment it would seem one of the computers will miss an update and the simulator will not load.

So, for a couple of the labs, I have had to recreate them in JavaScript without the graphics portion (the little simulated person getting squished by a planet’s high gravity) or visualization of the eccentricity of a planet’s orbit.  While these visuals did not provide essential information for the lab, they were nice to help engage the students. 

The gravity lesson I am rewriting deals with jumping on different planets. I did not want the students in sixth grade to have to calculate gravity for our simulated planets that were already based on Earth mass and radius and I could quickly simulate using G=m/r^2 to calculate the ratio. 

The first step is for them to measure their standing jump height in centimeters, and use this number in the simulator (Word version of table here.)

   Planet       Mass       Radius       Gravity       Jump
Inky 1 1    
Stinky 1 2    
Blinky 2 1    
Bob 2 2    


The simulator’s output includes the planet’s gravity and jump height without the orginal AJJAR simulator’s animated jumping character.  For the reflection question, they have to answer these statements describing the relationship of mass and radius to gravity:

  • If mass increases and radius stays the same, what happens to the gravity?
  • If radius increases and mass stays the same, what happens to the gravity?
  • As gravity increases, what happens to your jump height?

Older students have access to a data table with the mass and radius for each planet in the solar system measured in terms of “Earth.” We then experiment with some of the data from exoplanet discoveries to find the possible surface gravity.

Unlike many of my lessons, I do not have the students make a graph; it is easier to have them just look at the relationships between mass and radius. Not only the inverse, but also the inverse-squared relationship between radius and gravity, is one of those ah-ha moments that the students will have.

The AJJAR simulation that taps into my students’ inner 2-year-old is called Craters (

If you do it correctly, eventually you create an impact so large that it destroys the Earth. For this lesson, to try to rein in the destruction, I have them fill out Table 2. (Find the Word version here.)

While none of these will get to the magic planet killer, it is good for them to look at the relationships between the different values.

I didn’t just rewrite old presentations during this season; I also am preparing a new lesson on ancient explorers, starting with how to use the sun and Polaris to navigate and taking it all the way up to how to use a sextant.

When the social studies teacher first approached me about bringing his classes to the planetarium he was thinking about sundials. When he showed me the text that went with the unit, we decided that learning how to use a sextant would be a better application in the planetarium. Navigating with the stars was a nice bridge to the next unit they will be covering, which is tools and inventions.

 My original plan was to just use the star projector to simulate the pristine sky you would see without light pollution. In my initial tests, however, I felt that starting the lesson immediately in the dark would make it difficult for the audience to see me use the meridian markers, so I am going to use the fulldome system to have them learn the process of using a sextant and then switch them to the star projector to apply the skills.



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