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Difference between timelike and space like events

  1. Aug 27, 2014 #1
    hi, I need an explanatory difference between timelike and space like events . examples will do, i know the mathematics
  2. jcsd
  3. Aug 27, 2014 #2


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    First of all, an event by itself is neither timelike or spacelike. You have to have a pair of events and then the spacetime interval between those two events can be timelike or spacelike or null, depending on the specific events.

    Recall that an event has four coordinate, one of time and three of space. If the two events in question can be occupied by a single small inertial object with mass, such as a clock, then the spacetime interval is timelike and the period measured by the clock is the interval.

    If it is not possible for a massive object to be present at both events, then the question is can a ruler measure the spacial distance between the two event such that the time coordinates for the two events are equal. In this case the spacetime interval is spacelike and the ruler measures the interval.

    If neither of the above are true, then the spacetime interval is null, meaning that it isn't either of the above. Sometimes it is called lightlike, meaning that a photon can be present at both events.

    It's important to realize that the spacetime interval for any two events is either a space interval or a time interval or it's not an interval.
  4. Aug 27, 2014 #3

    Simon Bridge

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    No such thing - events are points in space-time and so are neither time-like nor space-like.
    If you know the maths then you already know the difference between time-like and space-like intervals.
    JIC: https://www.physicsforums.com/showthread.php?t=195101

    [edit] beaten to it :)
  5. Aug 27, 2014 #4


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    An event in itself cannot be time- or space-like. This is a property of a pair of events that can have time- or space-like separation. Time-like separated events are within each other's light cones and will always occur at different times in all frames while events with space-like separation are outside of each other's light cones and will be at different spatial points in all frames.
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