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Dr. Rhett Herman
Professor of Physics and Adjunct Professor of Geology
Director, Radford University Planetarium

Office: 135 Curie Hall
(540) 831-5441 (office phone)
(540) 831-5652 (department)
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School of Environmental and Physical Science
PO Box 6949
Radford University
Radford, Virginia 24142

There are a number of spreadsheet programs available. I have used Microsoft Excel to obtain the results described in an article in the American Journal of Physics. I have linked those two spreadsheets below.

Planetary models: two-planetary-models.xls. This spreadsheet "builds" a planet from r=0 to the surface, which is taken where the pressure P either goes to zero (for the solid planet) or falls below some pre-determined value (for the ideal gas planet).

Earth atmosphere model: atmospheric-model.xls This spreadsheet models Earth and its atmosphere as a two-layer interacting system. While a number of spreadsheets allow iterative calculations and scroll bars I happened to use Excel and thus wanted to explain how to invoke these abilities in Excel (they are typically disabled by default).

Instructions for enabling iterative calculations and scroll bars in Excel

To enable iterations in Microsoft Excel go through the “Office button” and into “Excel options.” Under the “Formulas” section and “Calculations” subsection check the box for “Enable iterative calculations.” Set the “Maximum iterations” for the number of iterations to be executed every time the control key is hit. Set the “manual” option to enable calculations to be initiated by pressing the control key. While a single press of the control key executes a set number of iterations, holding down the control key does not necessarily trigger that set number of iterations one right after another. However simply holding down this key is typically the most convenient way to execute a reasonably large number of iterations in a relatively short time.

Resetting the value of an iteratively defined cell (one with circular references) is done by first clicking in the cell, then clicking in the cell's definition in the formula bar at the top of the spreadsheet, and finally hitting return. This will return the cell to its original value of whatever constants may be in the cell.

Scroll bars in Microsoft Excel 2007 are inserted by going to the “Developer” tab. One of the options within the “Insert” button is a scroll bar. To change the parameters on the scroll bar right click on it and choose “format control.” If the “Developer” tab is not visible then it is enabled through the “Office button.” Under that button click “Excel options” and choose the “Popular” section. Check the box that says “Show the Developer tab in the ribbon.”