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Does 'isolated' mean 'free'?

  1. May 20, 2015 #1
    Is there redundancy in the phrase ‘an isolated free particle’?

    Do not the words ‘free’ and ‘isolated’ imply each other?

    Any help is much appreciated.

  2. jcsd
  3. May 20, 2015 #2


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    Staff: Mentor

    Perhaps they should, but natural language is sufficiently imprecise that we're better off with a bit of redundancy.
  4. May 20, 2015 #3
    Thanks Nugatory.

    I wonder whether Dirac would have used the phrase ‘an isolated free particle’!
  5. May 21, 2015 #4


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    Science Advisor
    Gold Member

    No, I don't think there is redundancy.
    E.g. an ion in an ion trap can be extremely well isolated from the environment but you could hardly refer to it as "free".
    The electrons in a free electron laser are (obviously) free, but since they are radiating they are not isolated.

    I think of "isolation" as referring to the absence of interaction with the environment, whereas "free" means that the motion of the object itself is not restricted.
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