written by Todd Timberlake and Mario Belloni

The Astronomical Parallax 2D Javascript Model illustrates the phenomenon of parallax in astronomy. Parallax is the apparent displacement of an object relative to the background that is caused by the motion of the observer (rather than the motion of the object itself, or of the background). This simulation illustrates the parallax of an object in space that results from the Earth's rotational or orbital motions.

The simulation has two different modes. The default is an Earth Rotation Mode. In this mode the simulation illustrates the parallax caused by Earth's rotation on its axis. The other mode for the simulation is Earth Orbit Mode. In this mode the simulation illustrates the parallax caused by Earth's orbit around the Sun. Now the observer moves along Earth's orbital path (shown as a blue circle with the orange Sun in the center). The bottom window shows the apparent motion of the object being observed.

The Astronomical Parallax 2D JS Model was developed using the Easy Java Simulations (EJS) version 5.  It is distributed as a ready-to-run html page and requires only a browser with JavaScript support.

• Download ejss_model_parallax2dJS.zip - 119kb Compressed File

Published September 2, 2013
Last Modified December 30, 2014

This file has previous versions.

An EPUB file containing the Astronomical Parallax simulation,
a general description, and the features of the simulation.

• Download ejss_model_astroParallax.epub - 127kb Compressed File

Published June 27, 2014
Last Modified July 28, 2018

This file is included in the full-text index.
This file has previous versions.

Source Code for the Astronomical Parallax 2D JS Model program.

• Download ejss_src_parallax2dJS.zip - 43kb Compressed File

Released under a This material is released under the Creative Commons Attribution-Noncommercial-Share Alike 3.0.

Published September 2, 2013
Last Modified December 30, 2014

This file has previous versions.