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robphy said:\eta_{\mu\nu} p^{\mu} q^{\nu}=p_t q_t - p_x q_x - p_y q_y -p_z q_z = (1)(1)-(1)(-1)-(0)(0)-(0)(0)=2... so p is not Minkowski-orthogonal to q. [In your required equation, (-a+b=0) means of course a=b ].
You're right, I was quite confused.
I was ultimately interested in defining a coordinate system. It looks like the right way to do it is to say that given a plane defined by two space-like vectors x and y (and their linear combinations) that there are two unique (except for their magnitude) null vectors perpendicular to that plane (for example z+t and z-t for the x-y plane), and that these 4 vectors (two space-like and two null) span the space-time and can thus serve as a coordinate system.
Hopefully I got it right this time around (I've seen null coordinates used, but I haven't used them much personally).