(I've already asked this question on Meta, but as one answer (by Joseph Weissman) pointed out this is already a philosophical question; so I thought it worth asking here).
I've asked a number of physics questions in philosophy, none of which included equations, and are determined by the larger, and as far as I can see philosophical questions about the natural world; traditionally, ie in Maxwells time, it would be called Natural Philosophy; and in fact Thomson & Tait (Thomson was knighted as Lord Kelvin, and in whose honour the natural scale of temperature is designated in Kelvin) brought out a book called The Principles of Natural Philosophy; this is a long and honourable tradition.
Yet people often attack these questions as not belonging to Philosophy.
A quick perusal of the SEP shows that there are many topics that it covers; for example:
Further, Oxford University has a faculty named Physics and Philosophy which is housed in the Humanities; from which course description one can see that:
The physics corresponds to the more theoretical side of the standard three-year Oxford Physics course while the philosophy focuses on modern philosophy, particularly metaphysics and the theory of knowledge.
They acknowledge a 'bridging subject', the Philosophy of Physics which interperlotes between the two disciplines.
and their interests lie broadly in:
interests in classical space-time theories, foundations of classical statistical mechanics, quantum mechanics, quantum field theory and quantum gravity.
These are, when suitably interpreted, the interests of the classical Milesian Materialists.
However, on this site, it seems that questions of Physics which are broadly philosophical in the above sense seem to be outlawed, as being not considered as philosophy. In my personal opinion, for what its worth, Philosophy ought to be considered a broad school, one looks at Aristotle for example who covered a broad swathe of scientia (knowledge) covering ethics, politics, and natural philosophy as well as metaphysics.
So the question here is how does one determine when a question of physics is philosophical enough, by what authority or by what criteria can we designate them? There is the obvious possibility that an inter-disciplinary subject such as this will offend the purists of both schools - still as the above examples show, it is possible.