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:
twoplanetarymodels.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 predetermined value
(for the ideal gas planet).
Earth atmosphere model:
atmosphericmodel.xls This spreadsheet models Earth and its
atmosphere as a twolayer 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.”
