Does the unobserved past exist in a super position in the sense of quantum mechanics? Has anyone seen this question asked before? If the question is meaningful, what answer seems most likely. If the question is not meaningful, where does it fail? Is it possible details of the big bang, including whether there was a big bang as opposed to a different origin of the universe that many potential answers exist in a super position, that will not collapse until an observation suitable to cause it's wave function to collapse is made?
It's an intriguing idea but sadly it isn't really compatible with current mainstream physics. You might have picked up the idea of an 'observer' from accounts of quantum theory, in some of which 'observers' and 'measurements' play a special role. However, there is no need to invoke either role, generally speaking, when you are talking about reality on a macroscopic scale. Our daily life on Earth goes on regardless of whether anyone is making observations or measurements in the sense adopted in quantum theory. Finally, the wave functions of quantum theory are always superpositions of one sort or another, so in general there isn't anything remarkable about a superposition- it just means that you can always express a wave function as a blend of other wave functions.