Dave wrote:

predicting the properties of something that is impossible to make is
impossible.

Egad, not at all.

The elements we use in circuit analysis, for example -- pure
resistances, capacitances, inductances, sources, and so forth -- are all
impossible to make. Yet we know their properties in exacting detail. One
cannot cut a stick to a length of exactly pi meters, yet the properties
of pi are precisely known. For that matter, we can't even make a stick
that's exactly one meter long, but the meter is very well defined.

Those are just a very few of the vast number of things which are
impossible to make yet whose properties are known. Math, science and
engineering wouldn't be possible without them.

Roy Lewallen, W7EL