Observer Effect

Leslie Eastman

Kei Itoh

This concept paper proposes a broader definition of the observer effect: not only the disturbance caused by observation, but also the way visibility, invisibility, and apparent naturalness are shaped by the observer’s structure, position, ability, environment, connecting apparatus, and descriptive system. It distinguishes active observer effects, where observation alters the object, from passive observer effects, where being an observer constrains what can be seen, resolved, reconstructed, and theoretically closed. Passive observer effects are further divided into internal effects, arising from the observer’s own structure and performance, and external effects, arising from the observer’s environment and position. Based on this framework, the paper offers a unified way to organize human observers, instruments, theoretical descriptions, approximations, assumptions, and even the axiomatization of vague concepts. Unreviewed conceptual preprint. PDFs in English and Japanese. Generative AI tools were used for language refinement and translation support; the author takes full responsibility for the final text, references, and claims. Keywordsobserver effect, internal observer, passive observer effect, relative a priori order, observational instrument, composite observer, effective state space, approximation, ideal system, axiomatic physics

Massimiliano Sassoli de Bianchi

Kenneth Paul Baclawski

The observer effect is the fact that observing a situation or phenomenon necessarily changes it. Observer effects are especially prominent in physics where observation and uncertainty are fundamental aspects of modern quantum mechanics. Observer effects are well known in fields other than physics, such as sociology, psychology, linguistics and computer science, but none of these other fields have experienced the same level of publicity and controversy as physics. This may be responsible for the widely held implicit assumption that “real” observer effects are exhibited only by quantum objects and not by classical objects. This misunderstanding may be due, to some extent, to confusing the observer effect with the Heisenberg uncertainty principle and with other quantum uncertainty principles. In fact, observer effects occur in both classical and quantum systems. This article presents a number of examples of observer effects in purely classical processes. It also introduces a framework for understanding and analyzing many of such effects for classical systems. Ignoring observer effects can cause errors in experiments at a macroscopic level where no quantum effects would be discernible. Consequently, there are practical reasons for being careful to address observer effects.

A. M. Bonch-Bruevich, V. A. Khodovoǐ

CONTENTS I. Introduction 637 II. Theory of the Stark Effect 638 1. The Stark Effect in a Constant Electric Field 638 2. The Stark Effect in Alternating Electric Fields 640 III. The Study of the Stark Effect in a Constant Electric Field 643 1. Observation of the Shifts of Centers of Gravity of Absorption Lines in Atomic Beams 643 2. Study of the Stark Effect by Observation of Electric Double Refraction 644 3. Study of the Stark Effect by the Method of Comparison with Hyperfine Splitting 646 4. Observation of the Stark Effect by Radiospectroscopic Methods 646 5. Study of the Stark Effect by the Method of Double Radiooptical Resonance 647 6. Observation of the Stark Effect by Level-crossing and Beat Methods 649 IV. The Study of the Stark Effect in Fields of Optical Frequency 651 1. Observation of Shifts and Splittings of Levels of the Ground State of Hg 199 by Resonance Light 651 2. Observation of Shifts and Splittings of Levels of Potassium Atoms in the Radiation Field of a Ruby Laser 653 V. Conclusion 654 Literature Cited 656