3.4.4.5 Observer Effect
The act of observing a situation or phenomenon must necessarily interfere with it. This observer effect is often negligible in classical situations when the observed objects are large, but for quantum systems, the observed object may experience a considerable change as a result of mere observation, even in cases of passive observation that do not directly act upon the object.
Many sophisticated experiments have been performed, especially using advanced versions of Young’s double-slit that will be discussed in section 4.4.9; all showing that the mere effect of watching greatly affects how the particles, or waves, enter through the slits and produce the interference pattern.
These results have led to speculation that the conscious mind can actually affect reality, though most physicists consider this to be a misconception of Quantum Mechanics, that results from misunderstanding of the quantum wave-function and the quantum measurement process. It will be shown, however, in chapter VI, how the Duality of Time explains the effect of the observer, consciousness, and other related essential quantum mechanical concepts.
As we have seen in section 4.4.2, the uncertainty principle has been frequently confused with the observer effect, even by Heisenberg himself who introduced and formulated this principle in 1927. The subtle difference is that the uncertainty principle is a theoretical restriction on how precisely we may measure complementary variables, such as the position and momentum of a particle, at the same time, while the observer effect is a result of the the disturbance that is inevitably introduced by the observer when taking the measurement.
The wave-function collapse, for which several popular interpretations assert that measurement causes a discontinuous change into an eigenstate of the operator associated with the quantity that was measured, a change which is not time-reversible.
The superposition principle of quantum physics dictates that a measurement will result in the wave-function collapse into a particular state among the other possible eigenvalues. Once the system is measured, and we know its current state, this prevents it from being in one of its other possible states. This situation is related to what is called the quantum Zeno effect, in which a quantum state would decay if left alone, but does not decay because of its continuous observation. The name comes from Zeno’s Arrow Paradox that we have discussed in section 5 of chapter II.