There Are No Laws of Physics, There’s Only the Landscape
Off-topic question that seems to trivial to take to Stack Exchange but I am struggling to find an answer to, maybe a physicist comes by and can provide an answer or relevant reference.<p>Let&#x27;s take a spin 1&#x2F;2 in the superposition state |0&gt; + |1&gt; ignoring normalization and then add the rest of the universe including a measuring device, an observer, and all the other bits and pieces of the environment. This state then undergoes unitary time evolution past the point where we measured the spin and the observer had a look at the measuring device.<p>It now seems to me that if the final state is a definite |0&gt; or a definite |1&gt;, then this measurement outcome must already have been present in the initial state, not necessarily as hidden variables of the spin but somewhere, for example in the micro states of the measuring device. If the final state could indeed be either |0&gt; or |1&gt; independent of the initial state, time evolution would not be unitary, it would not even be a function of the initial state.<p>The only other option seems to be that the final state is still a superposition and we have to reach for something like the multiverse interpretation to reconcile the fact that we indeed observe a definite final state. So what is the correct or at least common way to think about this? Time evolution is only approximately or sometimes unitary? The measurement outcome is, similar to decoherence, determined by the environment? The final state is still a superposition? Non of those seems to be a particularly attractive choice. Or did I somewhere make a stupid mistake?