Piero Scaruffi(Copyright © 2013 Piero Scaruffi | Legal restrictions )
These are excerpts and elaborations from my book "The Nature of Consciousness"
The Measurement as Interaction
According to Quantum Theory, our universe needs both kinds of processes. Von Neumann tried to figure out how they interact and realized that the answer lies in the "measurement" of the system.
Reality seems to proceed on two parallel tracks. The Schroedinger equation determines (in a deterministic manner) the evolution of the state of the system, but that state is a set of possible states each with its own probability of happening. So long as nobody observes the system, the Schroedinger equation predicts future probabilities of the system. Then Heisenberg's principle causes that wave function to "collapse" whenever the system is observed. The collapse causes the system to choose only one of the possible states. Once the observer has observed the system, only a part of the wave survives and evolves according to the Schroedinger equation. At this point the Schroedinger equation can calculate a new set of possible states. And so forth. The two views are both necessary to explain the evolution of the universe. They are not alternative views of the universe. One complements the other.
Note that the observer does more than just observe something: the observer also decides "what" to observe. That decision has an effect on the state of the system, because it forces the system to choose among all the possible states. Nature's role is really only to choose one of those possible states, and Quantum Theory can only presume that this is done randomly.
Von Neumann pointed out that measurement of a system consists in a process of interactions between the instrument and the system, whereby the states of the instrument become dependent on the states of the system. There is a chain of interactions that leads from the system to the observer’s consciousness. For example, a part of the instrument is linked to the system, another part of the instrument is linked to the previous part, and so forth until the interaction reaches the observer’s eye, then an interaction occurs between the eye and the brain and finally the chain arrives to the observer’s consciousness. Eventually, states of the observer’s consciousness are made dependent on states of the system, and the observer “knows” what the value of the observable is. Somewhere along this process the collapse has occurred, otherwise the end result of the chain would be that the observer’s consciousness would exhibit the same probabilistic behavior of the observable: if the observer reads one specific value on the instrument, it means that the wave of possibilities has collapsed (has chosen just that one specific value) somewhere between the system and the observer’s consciousness. At which point? What exactly causes the "collapse"? The instrument? The lens? The electrons inside the instrument? The observer's retina? The observer's nervous system? The observer's consciousness?
What constitutes a valid observer? Does it have to be big? Does it have to be in the brain? Does it have to be conscious? Does it have to be human?
Von Neumann showed mathematically that Quantum Theory is indifferent: it makes no difference to the statistical predictions of Quantum Theory where exactly this happens and what causes it. But humans are curious and would like to find out.
In a sense, Von Neumann was trying to reconcile "objective being" and "subjective knowing". In classical Physics they are one and the same, but in Quantum Physics they are different, and it is not completely clear how subjective knowing relates to objective being.
Later, the Hungarian physicist Eugene Wigner introduced another step in Von Neumann’s thought experiment: what if a friend is part of the chain that leads to the observation? If a friend measures the position of a particle and then relates to me the result, for me the wave “collapses” only when she tells me the result of her experiment. But the wave has already collapsed for her when she carried out the measurement. Did the wave collapse also for me at the same time? If not, do our waves collapse to the same value? Or does each of us live in an independent universe?
Von Neumann’s interpretation was in turn interpreted as implying that the observer somehow “creates” reality. Copernicus shocked the human race by telling us that we are not at the center of the world; Quantum Physics is telling us that we (our very consciousness) is at the center of the world. We are gods who create our own universe.
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