So copyright is simply an economic mechanism that permits an orderly marketplace to develop in products that have no physical, tangible weight. Well, you could write a book and call it Forrest Gump, give it that title, but you could not write a book that had the same scenes in it, the same story line in it, the same episodes in it that Forrest Gump had in it. Then you would be guilty of copyright infringement. Well, you know, obviously in all law there is a gray area, and there is a lot of litigation about precisely those cases where somebody has appeared to reuse certain elements of an existing work. You see that all the time in movies, in literature, in spy novels, in thrillers.
Space movies come out and all of a sudden space films are a very important genre.
You have Star Wars, you have Star Trek, and so forth. There is another important factor that does not exist in patent law but exists in copyright law. One of the things you have to show in copyright is that you actually copied somebody. Independent creation of a work immunizes you from copyright. So if you just happen to think up exactly the same story as someone else, even if it were almost identical, you would not be liable for copyright infringement.