Chapter Three THE IDEA TAKES SHAPE... PRESIDENTIAL APPROVAL IS GRANTED FOLLOWING the eventful breakfast, developments came fast. Samuel Marx carried the idea to Louis B. Mayer, M-G-M studio head. Other studio executives were called into session, and the enthusiasm was unanimous. There was just one stumbling block. It was realized at once that such a picture could not be filmed in its proper scope without cooperation from government, military and scientific leaders who formed an integral part of the story.   Marx was dispatched immediately to Oak Ridge, accompanied by Owen. They were met at their plane by Dr. Tompkins, who greeted them with, "I'm glad you're here. I hope M-G-M wiII want to make this picture because we scientists are frightened to death!".   The visitors from Hollywood were fingerprinted, photographed and questioned. From a meeting of scientists, they were given an outline of the exciting events leading up to the atomic discovery. They went from one key figure to another. Each gave his personal approval of the film, but declared that official approval should come from someone in higher authority.   The same was true in Washington, D. C. where they went next. Major General Leslie R. Groves and Brigadier General Thomas Farrell recounted the higher phases of the project's military side. But, authority for such a picture still had to come from higher up.   Finally, they reached the President of the United States!.