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Time a vector?

  1. Aug 21, 2011 #1
    Is time a vector?

    I don't think so, because we can't go back in time therefore it can't follow vector rules.

    However, I'm not sure this works in all cases (such as in a cases where v is close to c).

    Thanks for the help.
     
  2. jcsd
  3. Aug 21, 2011 #2

    BruceW

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    Homework Helper

    In relativity, time is one component of the spacetime 4-vector.
    Also, it is theoretically possible to go meet your former self according to general relativity.
     
  4. Aug 21, 2011 #3
    You can make time a scalar or a vector in a particular theory...the test is whether such a formulation matches observations and leads to any predictions. Is it useful??

    While time is a vector in relativity it is not in Newtonian physics.

    A vector has magnitude and direction....it doesn't have to point everywhere nor is our ability to "go" with a vector a criteria....for example, you also cannot "go" where an acceleration vector does.
     
  5. Aug 21, 2011 #4
    Oh I think I've seen that somewhere, but I thought we took the time out. E.G. [tex]{S(x,y,z,t)}[/tex] and then we did something like [tex]{S(x,y,z)*e^{-i\omega t}}[/tex] but I doubt that is what you're talking about haha.

    Anyway, thanks for the help!

    A vector also has to follow basic laws (addition, subtraction, etc). If you can't go back in time, then you can never have a negative time value which is possible following the laws of subtraction.For example, [tex]{C=B-A}[/tex] with [tex]{B=1}[/tex] and [tex]{A=2}[/tex] then [tex]{C=-1}[/tex] which wouldn't make sense to me.

    Anyways, thanks for your input and help!
     
  6. Aug 21, 2011 #5

    BruceW

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    Homework Helper

    No problem. It looks like you're talking about some quantum energy eigenstate. This can't be done for a general quantum state. Also, I was talking about relativity, not quantum mechanics.
    In relativity, we can talk about each spacetime event being specified by 4 components (i.e. a 4-vector). We only know which is the time component when we define it ourselves. So time is not a separate entity from space in relativity.
     
  7. Aug 21, 2011 #6
    Brain fart on my part haha, I guess when I was typing that I forgot that you were talking about general relativity >.<!

    Thanks for all the help though, I have little knowledge of relativity so I guess I have to start studying some of it :D!
     
  8. Oct 4, 2011 #7

    Dale

    Staff: Mentor

    The laws that a vector must satisfy are listed here.
    http://en.wikipedia.org/wiki/Vector_space#Definition

    There is no requirement that you be able to "go" backwards in time for time to be a vector. A negative time simply means that one thing happened earlier than another.
     
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