APS Excellence in Physics Education Award
November 2019

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Science SPORE Prize
November 2011

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The Open Source Physics Project is supported by NSF DUE-0442581.

Computer Program Detail Page

Item Picture
Astronomical Parallax 2D
written by Todd Timberlake
The Astronomical Parallax 2D 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 top window shows an observer (indicated by a green dot) on the equator of Earth (blue disk). The green line shows that observer's line of sight to an object in space (indicated by a red dot). This line of sight extends to show where the object would appear against a more distant background. When the simulation is played the observer moves around the Earth as Earth rotates. Parallax causes the apparent position of the object to move back and forth between two extreme locations (indicated by open red circles). The bottom window shows the apparent motion of the object against the stars, as seen by the observer. [Note: to keep the simulation simple it is assumed that Earth's equator is aligned with the ecliptic plane (the plane of Earth's orbit). In actual fact they are tilted by 23.5 degrees, but this cannot be represented in a simple 2D simulation.]

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 now shows the apparent motion of the Sun as well as that of the object being observed.

Please note that this resource requires at least version 1.5 of Java (JRE).
1 source code document is available
Subjects Levels Resource Types
- Astronomy Education
= Curricula
- Cosmic Time and Distance
= Parallax
- Historical Astronomy
= History of Astronomy
- Lower Undergraduate
- Middle School
- High School
- Instructional Material
= Demonstration
= Interactive Simulation
= Simulation
Intended Users Formats Ratings
- Learners
- Educators
- General Publics
- application/java
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Access Rights:
Free access
This material is released under a GNU General Public License Version 3 license.
EJS, Easy Java Simulations, OSP, Open Source Physics, apparent position, orbit, parallax, rotation
Record Creator:
Metadata instance created May 13, 2011 by Todd Timberlake
Record Updated:
January 25, 2023 by Lyle Barbato
Last Update
when Cataloged:
May 13, 2011
Other Collections:

ComPADRE is beta testing Citation Styles!

Record Link
AIP Format
T. Timberlake, Computer Program ASTRONOMICAL PARALLAX 2D, Version 1.0 (2011), WWW Document, (https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11201&DocID=2244).
T. Timberlake, Computer Program ASTRONOMICAL PARALLAX 2D, Version 1.0 (2011), <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11201&DocID=2244>.
APA Format
Timberlake, T. (2011). Astronomical Parallax 2D (Version 1.0) [Computer software]. Retrieved June 12, 2024, from https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11201&DocID=2244
Chicago Format
Timberlake, Todd. "Astronomical Parallax 2D." Version 1.0. https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11201&DocID=2244 (accessed 12 June 2024).
MLA Format
Timberlake, Todd. Astronomical Parallax 2D. Vers. 1.0. Computer software. 2011. Java (JRE) 1.5. 12 June 2024 <https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11201&DocID=2244>.
BibTeX Export Format
@misc{ Author = "Todd Timberlake", Title = {Astronomical Parallax 2D}, Month = {May}, Year = {2011} }
Refer Export Format

%A Todd Timberlake %T Astronomical Parallax 2D %D May 13, 2011 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11201&DocID=2244 %O 1.0 %O application/java

EndNote Export Format

%0 Computer Program %A Timberlake, Todd %D May 13, 2011 %T Astronomical Parallax 2D %7 1.0 %8 May 13, 2011 %U https://www.compadre.org/Repository/document/ServeFile.cfm?ID=11201&DocID=2244

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Astronomical Parallax 2D:

Is Based On Easy Java Simulations Modeling and Authoring Tool

The Easy Java Simulations Modeling and Authoring Tool is needed to explore the computational model used in the Astronomical Parallax 2D.

relation by Wolfgang Christian
Covers the Same Topic As Astronomical Parallax 2D JS Model

The Astronomical Parallax 2D Model is the Java version of the  Javascript-based Astronomical Parallax 2D Model.

relation by Mario Belloni

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