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written by Richard McCray and Andrew Koelemay
This applet illustrates the challenges of communicating with extraterrestrial civilizations. It shows a galaxy with a diameter of 100,000 light years. The user is able to control the average lifetime of communicating civilizations and the birth rate of such civilizations in the Milky Way galaxy. After hitting start, Earth appears and begins transmitting its signal. When Earth receives a signal from another civilization, a line appears connecting them. The applet will automatically pause when Earth ceases to communicate. Signals change color when a civilization ceases to exist.

This is part of a larger collection of applets by STEM Colorado focused mostly on topics in astronomy.

Please note that this resource requires at least version 1.4.2_06 of Java.
Subjects Levels Resource Types
- Space Exploration
- Lower Undergraduate
- High School
- Upper Undergraduate
- Instructional Material
= Activity
= Interactive Simulation
Intended Users Formats Ratings
- Learners
- application/java
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Access Rights:
Free access
© 2004 Richard McCray
communicating through space, communication, extraterrestrial civilization, life in space, life on other planets
Record Cloner:
Metadata instance created August 27, 2008 by Alea Smith
Record Updated:
August 28, 2008 by Cathy Ezrailson
Last Update
when Cataloged:
August 27, 2008
Other Collections:

ComPADRE is beta testing Citation Styles!

Record Link
AIP Format
R. McCray and A. Koelemay, (2004), WWW Document, (
R. McCray and A. Koelemay, STEM Colorado: Galactic Communication, (2004), <>.
APA Format
McCray, R., & Koelemay, A. (2008, August 27). STEM Colorado: Galactic Communication. Retrieved February 16, 2019, from
Chicago Format
McCray, Richard, and Andrew Koelemay. STEM Colorado: Galactic Communication. August 27, 2008. (accessed 16 February 2019).
MLA Format
McCray, Richard, and Andrew Koelemay. STEM Colorado: Galactic Communication. 2004. 27 Aug. 2008. 16 Feb. 2019 <>.
BibTeX Export Format
@misc{ Author = "Richard McCray and Andrew Koelemay", Title = {STEM Colorado: Galactic Communication}, Volume = {2019}, Number = {16 February 2019}, Month = {August 27, 2008}, Year = {2004} }
Refer Export Format

%A Richard McCray
%A Andrew Koelemay
%T STEM Colorado: Galactic Communication
%D August 27, 2008
%O application/java

EndNote Export Format

%0 Electronic Source
%A McCray, Richard
%A Koelemay, Andrew
%D August 27, 2008
%T STEM Colorado: Galactic Communication
%V 2019
%N 16 February 2019
%8 August 27, 2008
%9 application/java

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.

Citation Source Information

The AIP Style presented is based on information from the AIP Style Manual.

The APA Style presented is based on information from APA Electronic References.

The Chicago Style presented is based on information from Examples of Chicago-Style Documentation.

The MLA Style presented is based on information from the MLA FAQ.

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