not very interesting
To begin, it seems as if you assume that your audience has a moderate grasp of physics terminology and basic theories. In my opinion, hardly ANYone ever really has a grasp of physics terminology and theories. Putting that aside, it was a unique idea to try to explain relativity, but putting it in a 5 minute flash presentation is a feat in itself. Making it enjoyable is also another problem. Your explanations were not the most simple and it was paragraph after paragraph that had numerous spelling mistakes. The sparse animation needed better, more eye-catching graphics and movements, along with a background of some sort. Try dumbing down the explanations even more, and possibly learn a bit of actionscript so that you may be able to make this concept more interactive and interesting. Either way, I'm sure it has plenty of potential, so much luck to you.