Physics/Observer/Effect
Observer Effect (Physics)
Overview
- The observer effect is the disturbance of a system by the act of observing it. To learn anything about a system, an instrument has to interact with it, and the interaction changes what is being measured.
Examples
- Checking a tire's pressure lets a little air out of the tire.
- A mercury thermometer has to absorb or give up heat to reach the temperature of what it measures, so it shifts that temperature slightly.
- Seeing an electron takes at least one photon striking it. The collision changes the electron's momentum and position.
In quantum mechanics
- Measuring a quantum system changes its state. A system in Superposition is found in a single outcome once it is measured.
- In the double-slit experiment, placing a detector at the slits to learn which one each particle passes through erases the interference pattern on the screen.
- The observer effect is related to Heisenberg's uncertainty principle, which is a separate result: the uncertainty principle limits how precisely pairs of quantities such as position and momentum can be defined at all, however gently they are measured.
Misconceptions
- The "observer" is any instrument or interaction that records information. Detectors produce the same effect whether or not a conscious person reads them, and research does not support the claim that consciousness changes physical reality.
Sources