Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

What does 'observing' mean

  1. Mar 30, 2012 #1

    Please can anyone tell me what 'observing' means for example when we 'observe' a particle its wavefunction collapses, however surely observation is the wrong word as human conscience has absolutely nothing to do with this.

    Any help is greatly appreciated, thank you
  2. jcsd
  3. Mar 30, 2012 #2
    I'm no expert, I only have a basic understanding of QM, but I think observing means gathering information about something. It has nothing to do with human consciousness, but it does have something to do with the concept of information. Say a computer program gathers information about a particle and deduces stuff based on that. Its wave function will collapse. The weirdest thing (again, this could be wrong) is that if some sensor picks up stuff and then the information is deleted or made inaccessible before it's gathered by anything, the wave function won't collapse?
  4. Mar 30, 2012 #3


    User Avatar
    Science Advisor

    "Observation" means that the particle interacts with the environment containing many degrees of freedom, which causes decoherence of the particle state. Decoherence can be visualized as a split of the wave function into separate branches which do not communicate with each other. In this way each particular branch perceives the rest of the of the world as if other branches did not exist, which looks like collapse to the branch.

    The unsolved problem is why should a particular branch perceive anything in the first place. One of the possibilities is that it DOES have something to do with conscience, but there are other (more "physical" in spirit) possibilities too. The prominent examples of such possibilities are many-world interpretation and Bohmian interpretation.
  5. Apr 1, 2012 #4
    Whenever I hear or read the word "observation" in relation to quantum mechanics, I always take it to really mean "interacting," because in the quantum world, observations can only come about through an interaction. So of course it makes sense that observations change the results of the experiments.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook