How do you find what version Google Earth I have?

When the google Earth application is running, open the Help menu and select the "About google Earth" item. This will open a popup window with google Earth version (e.g. 7.3.0.3830), build date, renderer (OpenGL or DirectX), etc.

With Apple iphone or iTouch, start google Earth application. Open menu, then click Settings and scroll to end of the list to find the google Earth version.