The EJS Gnomon model simulates the shadow cast by a gnomon (the part of a sundial that casts the shadow) over the course of a day for any day of the year and any latitude on Earth. The program gives you the option to use mean Sun (which moves relative to the stars at a constant rate throughout the year) or true Sun (which varies its apparent speed relative to the background stars). The default is to use true Sun. The program also shows the observer's horizon plane on the spherical Earth, as well as the ecliptic and the apparent path of Sun. The Earth View can be set to let Earth rotate or remain fixed
EJS Gnomon model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_astronomy_Gnomon.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for astronomy are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.
Please note that this resource requires
at least version 1.5 of
Gnomon for Teachers
A customizable Gnomon Model that allows teachers to set the display parameters. The customized simulation is automatically saved with associated curricular in a new jar file that can be redistributed. download 1260kb .jar
Published: July 28, 2012
Gnomon Model: Student Version
EJS Gnomon Model: Student Version is a simulation for college students. It is distributed as a ready-to-run (compiled) Java archive and has the Shadows and Gnomons activity worksheet pdf built-in. Double clicking the ejs_Gnomon_ShadowsAndGnomons.jar file will run the program if Java is installed. download 1424kb .jar
Published: July 28, 2012
Gnomon Model Source Code
The source code zip archive contains an XML representation of the Ejs Gnomon Model. Unzip this archive in your Ejs workspace to compile and run this model using Ejs. download 43kb .zip
Published: August 18, 2009
%0 Computer Program %A Timberlake, Todd %D August 18, 2009 %T Gnomon Model %7 1.0 %8 August 18, 2009 %U http://www.compadre.org/Repository/document/ServeFile.cfm?ID=9378&DocID=1276
Disclaimer: ComPADRE offers citation styles as a guide only. We cannot offer interpretations about citations as this is an automated procedure. Please refer to the style manuals in the Citation Source Information area for clarifications.
The Eratosthenes model displays the shadows cast by two gnomons (sticks) at different locations on Earth. This simulation can be used to help illustrate how Eratosthenes was able to measure the diameter of Earth using the shadows cast by two gnomons.