About Einstein's Rocket

General Info

This set of Java applets is designed to teach the basic principles of special relativity. The first applet goes through various thought experiments to give you an understanding of why relativity works the way it does. The second applet (1-D Space Rally) helps demonstrate why the "twin paradox" is, in fact, not a paradox. And the third applet contains several games which allow you to get a better intuition about the effects of relativity on motion at high velocities. To access the applets, simply click the links at the top of this page.

This page is best viewed in a modern browser with support for CSS.

If the applets will not load, check to make sure that your browser supports Java and has Java enabled.


These three programs were originally designed and written for an Apple II by Joel Primack and Eric Eckert in the early 1980s. The Java version was coded by Devin Kelly-Sneed under the supervision of Joel Primack.

Contact Info

If you encounter a bug in any of the applets or in the website, please send an email describing the problem to EinsteinsRocket@gmail.com. If possible, also include what operating system and browser you're using, as well as any other info that you think may helpful to us in solving the problem. Non-bug related feedback is also welcome at the same email address.

Copyright 2005 Regents of the University of California