belladivediva, you may want to take a look at Medibuntu, which is a collection of popular applications (including Google Earth) that aren't in the Ubuntu standard repositories.
By adding a repository containing Google Earth rather than downloading the binaries, you can keep Google Earth up to date along with the rest of your system, and you won't have to worry about setting file permissions and so on.
http://www.medibuntu.org/ (see the "Repository Howto" link)