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If I said that we are living in a Universe with 3 time dimensions and 1 spatial dimension, would I be wrong?

By that I mean if the spacetime interval was evaluated as -time1^2-time2^2-time3^2+space1^2 instead of space1^2+space2^2+space3^2-time1^2.

Is there an absolute difference between a spatial and a time dimension, or are they like the positive and negative electrical charges?

Edit: This came to me after reading a question considering more than 1 time dimensions. I think it was about a 2+2 universe, which prompted the question "Which 2 would be the time dimensions?"

So I guess the real questions is, is time's property the fact that it is a single dimension of its type/sign, instead of 3? Could we talk about spacetimes only for 1+N pseudo-euclidean spaces, but not for M+N where M>1 and N>1?

And also, if we have 3 time dimensions and 1 space dimension, and the spacetime interval was

sashoalm
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1 Answers1

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Time-like dimensions are those where motion is only possible in one direction (we call that forward because it's pessimistic to say you can only go backward) and observing is only possible in the reverse direction (that's a direct result of motion only being allowed in one direction). Spatial dimensions are those where motion is possible in both directions as is observation.

The spacetime interval can be written with either the mostly plus or the mostly minus signature, (+ - - -) or (- + + +), without changing the fact that there is only one time dimension and three spatial dimensions.

When you see something like "in an m+n universe", m is the number of spatial dimensions and n is the number of temporal dimensions.

Jim
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