Hossein Jorjani
First publication: 2026 – 07 – 19
One of the recurring themes in twentieth-century philosophy and sociology is the claim that the act of observation affects the object being observed. This idea appears in a variety of forms, ranging from discussions of quantum mechanics to debates in the social sciences. Yet these examples are often grouped together under a single heading despite involving fundamentally different mechanisms. A clearer understanding requires attention to the scale and nature of the system under investigation.
Consider first the case of the Moon. The distance between the Earth and the Moon may be measured using telescopes, radar, or laser-ranging techniques. Such observations undoubtedly increase human knowledge of the Earth–Moon system. However, the act of observation does not meaningfully alter the distance being measured. The energy transferred by a telescope or laser beam is negligible in comparison with the mass and momentum of the Earth–Moon system. In this case, observation affects the observer’s knowledge but has no practically significant effect upon the observed object.
A very different situation arises in quantum mechanics. To determine the position, momentum, or other properties of an electron, one must interact with it through physical processes involving photons or other particles. Because the systems under investigation are extremely small, the interaction required for measurement may be comparable in magnitude to the phenomenon being measured. In this context, observation can alter the state of the observed system itself. The observer effect is therefore not merely epistemological but a physical consequence of the interaction between measuring apparatus and object.
A third type of observer effect appears in human and social systems. Consider a financial market. A journalist or television commentator reports that a particular company is likely to prosper or fail. Investors react to the report by buying or selling shares. Their actions alter the market, thereby changing the very phenomenon that was originally being described. Here the mechanism is neither astronomical nor quantum. It is reflexive. Human agents respond to information about themselves and their environment, and their responses help shape subsequent events.
These examples illustrate that observer effects are not a single phenomenon. Their existence, magnitude, and mechanism depend upon the scale and nature of the system under investigation. A proposition that is valid for subatomic particles cannot automatically be generalized to astronomical bodies, nor can reflexive processes characteristic of human societies be extended to nature as a whole.
Hossein Jorjani 