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Say you discover a star 100 light years away. Before you spotted it with your telescope, it was in a superposition of states, some of which would lead it to become a nova in the near future. Your observation brings into reality a state that does NOT lead to a nova. Did you just save the star, you who are 100 years into its future? Do we create the past, so to speak, when we look at it from the future? Do we affect the evolution of galaxies millions of light years from us simply by observing them today? What is the quantum effect of delayed observation?

John Wheeler had a similar idea with his "participatory universe" -- his famous "U". See wired.com/story/black-holes-will-destroy-all-quantum-states: "By looking back to the early universe, these observers somehow made it real." enter image description here

Maurice Mizrahi
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There is a popular misconception that an observer in quantum mechanics means human (or some other sentient being). As discussed in What is an observer in quantum mechanics? this is not the case. A quantum system interacts with its environment and this leads to a process called decoherence. We humans a hundred light years from the star are part of that star's environment but a negligibly minor part compared to all the matter near to the star.

However decoherence is not by itself a full explanation for the collapse of the wavefunction, and indeed there is no universally accepted full explanation. It's usual to combine decoherence with something like many worlds to explain why we humans only observe eigenstates of our measurement operator, though we should emphasise that many worlds is only one of many ideas about the measurement process. In any case to suggest that your observation of the star plays a significant role in determining its state seems far-fetched.

John Rennie
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