I mean, the whole idea of observers - that's a pedagogical thing. It's very convenient when you're trying to understand something to imagine doing an experiment or think about an observer doing something. But that doesn't have anything to do with physical law, that has to do with the understanding of the law. A physical law is a description of nature, not a description of observers. Using the word observer in any place in physics at all - it's irrelevant. It's never part of a physical theorem. Look, they apply quantum mechanical laws to the Big Bang! There were no observers there!
Robert Serber - The Second Creation
