ergo
This line of argument brings us to an interesting notion: that of the interaction boundary. Let us assume an observer and a system to be observed-any observer and any system. Between them, imagine a boundary, and call it an interaction boundary. This boundary is strictly mathematical; it has no necessary physical reality. In order for the observers to learn about the system, they must cause at least one quantum of "information" (energy, momentum, spin, or what-have-you) to pass from themselves through the boundary. The quantum of information is absorbed by the system (or it might be reflected back) and the system is thereby perturbed. Because it has undergone a perturbation, it causes another quantum of information to pass back through the boundary to the observer. The "observation" is the observer's subjective response to receiving this information. In a simple diagram, the situation looks like this:
O | S
where O and S represent the observer and the system, the vertical line represents the interaction boundary, and the arrows represent the information exchanged in the act of observation.
In this scheme, no observation can be made without first perturbing the system. The observation is never one of the system "at rest," but of the system perturbed. If represents the state of the system before the perturbation and ±represents the state immediately after, then the observation approaches the ideal only if
<< .
If I is the information selected by the observer to send across the interaction boundary, then it is apparent that must be a function of I: i.e.,
= (I).
Thus, the observation is affected by choices made by the observer, as quantum mechanics seems to teach. In the case of atomic and some molecular phenomena, the inequality
<<
does not hold; in fact so that the perturbation is comparable in magnitude to the state itself. Because all information is exchanged in quanta (modern physics does not allow for the "smooth exchange" of arbitrarily small pieces of information), this situation necessarily gives rise to an inescapable uncertainty in such observations. The quantum theory takes this uncertainty into account as the Heisenberg Uncertainty Principle.
Uncertainty is not strictly a law of Nature, but is a result of natural laws that reveal a kind of granularity at certain levels of existence. Observers in modern physics truly become participants in their observation, whatever that observation might be.
