OBSERVER

Observer

The term observer in special relativity refers most commonly to an inertial reference frame. Less often it may refer to an arbitrary non-inertial reference frame; in particular, a Rindler frame is sometimes called an "accelerating observer". In such cases an inertial reference frame may be called an "inertial observer" to avoid ambiguity. Note that these uses differ significantly from the ordinary English meaning of "observer". Reference frames are inherently nonlocal constructs, covering all of space and time or a nontrivial part of it; thus it does not make sense to speak of an observer having a location. Also, an inertial observer ...

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observer

Noun

  1. One who makes observations, monitors or takes notice
    Most impartial observers agreed that Sampras had not served well.
  2. One who adheres or follows laws, guidelines, etc.
    I shall be an observer of the local customs.
  3. A person sent as a representative, to a meeting or other function to monitor but not to participate
    The UN sent many observers to the country's first elections.
  4. A crew member on an aircraft who makes observations of enemy positions or aircraft
    The only crew-member to survive the crash was the Canadian observer.
  5. A sentry etc. manning an observation post
    We waited till dusk when the observers' vision was poorest.


The above text is a snippet from Wiktionary: observer
and as such is available under the Creative Commons Attribution/Share-Alike License.

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