How can you prove the Law of Conservation of Energy in that case?

I think that's a very hard question for anyone to answer. I thought about the question for a while, and I still couldn't answer it. I think another option would be to search similar questions on Yahoo or Google search. If you know anyone else in the subject, try calling them or e-mailing them with the question. I am sorry if I am not helping much, but it's just a though. I really hope it helps.