Minkovski said time is speed, did here. Where did he publish that, exactly?

Not Minkowski; Einstein himself.

In post #204 of my final thread on Minkowski, Farsight once provided us a link to this, an English translation of possibly the most famous document in science history:

http://einsteinpapers.press.princeton.edu/vol4-trans/258?ajax
You will note both the title and the author. This is not a pseudoscience.

And the link to the particular page in question:

http://einsteinpapers.press.princeton.edu/vol4-trans/271?ajax
Einstein acknowledges the work of H. Minkowski on the development of his Theory of Relativity, and then goes on to say:

"Minkowski started out from the premise that the "time coordinate" enters the fundamental equations of the theory of relativity in exactly the same way as the spatial coordinates if t is replaced by the imaginary quantity: square root(-1) * ct = ict which is proportional to it. The equations of the theory of relativity thereby become equations in a four dimensional space; and only in the number of dimensions are the formal properties of this four-dimensional space distinguished from the formal properties of the space of Euclidean geometry."

The last time I pointed this out, you replied (post #237) in part:

"You're not making much sense. If t=ict, then t/t = 1, not ic

Can you do maths at all?"

To answer your previous question more directly, can you? A PROPORTIONAL relationship is not the same as equality. There may be a constant factor of proportionality involved, and that factor is not necessarily equal to 1. That proportionality constant could be a number greater than 10,000, for example, and it would really make no difference to Minkowski's formulation of the role of time in Special Relativity, nor very much to his math.

A velocity that is faster than light might impact the assumption of c as a universal speed limit for the bulk propagation of energy, but there would either need to be an extension to the theory, or else it might require another theory partitioned for the same reason a more general theory with gravitation was advanced.

While researching the answer for your question, I also happened across something else I missed. Evidently Minkowski once wrote that "for any two events, simultaneity does not actually exist". Now that's a gem of an idea I would tend to agree with, other than for quantum entanglement spin flips, that is. Don't know how I could possibly have missed it in that other thread.

And so Minkowski's formulation of relativity involves complex math in order to assure that the direction of time's arrow cannot reverse in a manner that would permit light to propagate backwards through time. At the same time, it is understood that the factor c means a universal and invariant speed limit so that v < c in all cases where bound or unbound energy travels or propagates throughout a universe where it is assumed there are no large gravitating masses in the special case (Special Relativity). In the general case, there are new equations to deal with (General Relativity).

And thanks again for your patience, James R.

One of the beauties of this forum is that the responses to questions are challenging enough to think about for a while, and help us try to deepen our understanding, as meager as might be the case. That's why I still like to read what certain people have to say here.