[qorrect]

That's Lorentzian geometry and Minkowski space from the 1900's and created for Relativity.

This is Euclidian geometry, much older and more 'accepted'.

[r14c]

I imagine there would still be a relationship with `c` in a fourth spatial dimension, but it might be useful for taking shortcuts around 3d space without having to violate causality.

[NomDePlum]

I'm sure you are right on that.

I'm going to have to plead ignorance on this. Which will likely not surprise you.

I'll have more than the cursory read through the article in an attempt to educate myself.