The Observation Factor
Part of the motivation for this page comes from Allan Randall's Computational Metaphysics. Allan concludes his metaphysical excursion in a strangely truncated form of idealism based on Strong AI and the Many Worlds interpretation of quantum mechanics. All of this because he has forgotten about Wigner's Friend, I believe.
Wigner's Friend is an extension to Schrodinger's Cat thought experiment. It simply raises the question of who observes the observers. This is a question that has famously been left unanswered. Somewhere else on the Internet it must have been stated that no one short of God can observe the observers. (Actually I find one example of "observe the observers" & quantum, and there is ample mention of God and everything else. Remind me to peruse it later.)
It remains the standard view that the observer role in QM may be satisfied by virtually any registering mechanism, which need not be artifactual. The moon has very adequately registered the impact of asteroids, or so it is generally surmised.
More technically, a registration process is supposed to be any trace of an event, where 'trace' is a disturbance in a medium, such as the ionization path of a cosmic ray. The wave function of a neutrino from the Sun spreads out uniformly until it interacts with another particle deep in the Earth, for instance. Its wave function has been collapsed by the interaction. This is fairly straight forward. But what about the molecules in the air? How spread out are they? Supposedly this is only until they collide with the next air molecule. But now we have no trace. At best we can observe the gross diffusion of pollutants. Otherwise the measurement process becomes anti-entropic or Maxwell demonic, i.e. physically impossible. So an air molecule can spread out to the moon and beyond, if it so chooses. Who is to stop it? The measurement process has become lost in the interstices of quantum statistics, where there is no trace of the individuality that defines any actual measurement.
Let us now stand this problem on its head. To measure a quantum system there must be an external 'classical' system. Suppose, however, that the quantum system in question is the universe. What would it take to collapse the wave function of the universe? This is a notoriously open question in cosmology, especially relative to the quantum fluctuation origin of the Big Bang. How do we know that our universe is not merely a virtual quantum universe that could at any moment dissolve back into a sea of probability?
Think of those infinitely(?) many other uninhabitable, unobservable quantum universes. Do they or can they be assigned any physical reality? Do they exist only in the imagination of the quantum cosmologists, like a herd of unicorns? Physicists, by professional necessity, are most adept at sweeping the quantum problems under the rug. Or perhaps they are passing the quantum buck. If so, where does the Quantum stop?
Before attempting to answer that, we might well wonder why the Quantum in the first place.