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.