Why do some books give opposite signs for the spacetime interval?

[Amith2006]

Homework Statement

I am bit confused about the expression for finding the space time intervel. Some books say it is,
(spacetime intervel)$$^{2}$$=(time intervel)$$^{2}$$ - (space intervel)$$^{2}$$
while some books say it is,
(spacetime intervel)$$^{2}$$=(space intervel)$$^{2}$$ - (time intervel)$$^{2}$$

Homework Equations

The Attempt at a Solution

 

[Cyosis]

It's just a convention, pick one and stick to it. The physics will be the same.

 

[LithiumHelios]

As mentioned above it's just based on the adopted convention. http://en.wikipedia.org/wiki/Sign_convention#relativity - This wiki article on the sign conventions employed may help clear things up. It is something of an arbitrary choice though as long as you remain consistent.

 

[Amith2006]

The criteria for an intervel being time like or space like just get interchanged. Maybe it is not a universal fact as u say. Anyway, thanks guys.