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What are the 4 dimensions?

  1. Apr 16, 2007 #1
    The 4 dimensions are the 3 spatial and the one time but is there any order for which these can be listed?
    Also is it possible that the sub-atomic particles exist on another dimesion (such as photons, neutrinos, and etc.)? And this is why we have such a challenging problem understanding the particles.
  2. jcsd
  3. Apr 16, 2007 #2


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    We understand fundemental particles fairly well with our boring 4 dimensions. And so far there's no hard evidence for extra dimensions, although some theories make use of them.

    I don't know what you mean by 'is there any order for ... listed'. You can list them in any order you like as long as you remember it.

    After all, you know '11 o'clock' is a time and not a street address.
  4. Apr 17, 2007 #3
    There's three spacial dimensions because you require 3 independent variables to uniquely define a point in space. This doesn't say anything about the layout of those dimensions, ie your choice of basis, and for the most part your basis choice is entirely up to you. There is no 'natural basis' to things, with orthogonal x,y,z vectors pointing in a specific orientation, you have to pick such a thing every time do you a calculation or a modelling scenario.

    As such, if you pick your coordinates x,y,z in a certain orientation, someone else can come along and say "I prefer my coordinates as y,z,x in this orientation". Now yours and his are equivalent under a certain transformation and your choices should have no bearing at all on th end result of your calculations (ie no change in the physics). Thus it seems there's no 'order' to the dimensions at all. You can tell there's 3 of them but how you label them throughout space is pretty much up to you (up to the matter of self consistency obviously).
  5. Apr 17, 2007 #4
    Thank You!
  6. May 16, 2007 #5
    True, but the points in space are not the same thinh as particles in space (even if they are point particles). Particles move with regards to points in space, so it seems to me we need four variables. No?
    Last edited: May 16, 2007
  7. Aug 4, 2007 #6
    Why not allow for 4 spatial dimensions, with one of them what the clock measures, then add time as a fifth non-spatial dimension which gives order to flow of information from past to future ?
  8. Aug 4, 2007 #7
    Particles do indeed move. That's why the classical phase space for a single particle is 6 dimensional. You need three more variables to specify the momenta in 3 chosen directions.
  9. Aug 6, 2007 #8
    A friend of mine asked me the same question in which you are wondering, the three spatial dimensions and the additional time dimension do not require to be placed in any particular order, rearrange them as you like, it's just a method of remembering. The three spatial dimensions are more traditional than that of time, so rightly they are usually represented prior to time.
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