Observer effect

The observer effect is a principle of physics and states that any interaction between a particle and a measuring device will inevitably change the state of the particle. This is because the act of measurement itself imposes a disturbance on the particle’s wave function, which is the mathematical description of its state.

  • The concept of observation refers to the act of engaging with an electron or other particle, achieved through measuring its position or momentum.
  • In the context of quantum mechanics, observation isn’t a passive undertaking, observation actively alters a particle’s state.
  • This means that any kind of interaction with an atom, or with one of its constituent particles, that provides insight into its state results in a change to that state. The act of observation is always intrusive and will always change the state of the object being observed.
  • It can be challenging to reconcile this with our daily experience, where we believe we can observe things without inducing any change in them.
  • The observer effect implies that:
    • Measuring a particle’s position compels it to assume a specific location.
    • Measuring a particle’s momentum compels it to adopt a particular measurable value.
  • The observer effect applies to all quantum systems, including atoms, molecules, and photons.
  • The observer effect is not fully understood. There are many different theories about how it works, but no one theory is universally accepted.