AFAIK, one of the features of Aperture is that it doesn't create a new photo (or mess up the original one) when you edit. It simply stores information in its database about what you did when you edited it. When you go to redisplay the edited photo again, it uses the original photo, and then re-applies the edits. Saves a lot of disk space by doing that, but that does essentially break using Finder to view photos (if you want to see the edited photos, anyway).
Exporting versions will create a new photo (JPG, whatever) of your edited photos, but probably way more work than you want to get into.