Spacetime > Run the program > Get Java
The Spacetime program is a JAVA application. If the program does not start when you try to run it, then your computer is not JAVA enabled. You need to download and install the JAVA Runtime Environment from the website
Click DOWNLOAD NOW and follow the instructions that appear on the screen. This will install the JAVA version compatible with your particular operating system. You can now run JAVA applications and view Java applets —small computer programs embedded in web pages.