The Sidereal and Solar Day model illustrates the difference between the sidereal and solar day. The planets of our solar system both orbit around Sun and rotate on their axis. These two rotations allow for multiple definitions of what a day is.  This simulation shows the orbit and rotation of a planet (blue) around Sun (orange). It uses an orange arrow to represent where Sun would be seen in the sky relative to the background stars.  A point on the rotating planet is shown with a red arrow to indicate where that point faces relative to the background stars. In order to account for the true scale of the distance of the stars away from the planer, a longer red arrow from Sun points in the same direction as the arrow on the planet to indicate where this point faces relative to the background stars.  Users can toggle between the geocentric and heliocentric point of view. The parameters are initially set to model the orbit and rotation of Earth.

Sidereal and Solar Day 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_SiderealSolarDay.jar file will run the program if Java is installed.

Please note that this resource requires at least version 1.5 of Java (JRE).