The idea that the presence of an observer can affect the outcome of a double-slit or photon experiment is often misunderstood or misrepresented. This misconception stems from a misinterpretation of the role of observation in quantum mechanics.
In quantum mechanics, the act of measurement or observation does indeed have an effect on the system being observed. This is known as the measurement problem or the observer effect. However, it's important to note that the term "observer" in this context does not refer to a conscious observer or human being.
In the case of the double-slit experiment, the observer effect refers to the fact that when a measurement is made to determine which path the photon takes (whether it passes through one slit or both), the interference pattern disappears. This is because the act of measurement disturbs the system and collapses it into a definite state, destroying the interference pattern.
It's true that in experiments, we often use devices like photomultiplier tubes or semiconductor detectors to make measurements. These devices are not conscious observers but rather instruments designed to detect the presence or absence of photons. However, the key point is that any interaction with the quantum system, whether it's a measurement device or any other physical system, can disrupt the interference pattern.
The observer effect is not limited to human observers but applies to any interaction that extracts information from the quantum system. The act of measurement, regardless of the specific apparatus used, disturbs the system and alters its behavior. This is a fundamental aspect of quantum mechanics.
It's important to avoid conflating the observer effect in quantum mechanics with consciousness or the idea that the human mind has some magical power to alter physical reality. Quantum mechanics is a well-established and extensively tested theory that accurately describes the behavior of particles at the microscopic scale. The observer effect is simply a consequence of the probabilistic nature of quantum mechanics and the unavoidable disturbance caused by any measurement process.