Phases of nature as emergent phenomena
Much has been made of emergence recently — how complex systems develop / exhibit behaviours based on the interaction of simpler individual components. An example might be how extraordinarily complex economies can develop, through the interaction of thousands or millions of individual “agents” in an economy, buying or selling as per their individual whims.
It occurred to me that the phases of nature (solid, liquid, gas, plasma — or “earth”, “water”, air”, “fire” for any Aristotelian holdouts) are themselves emergent phenomena.
An individual molecule can’t be solid or liquid: these stuctures require the coming-together of a bunch of molecules, either into a lattice structure (solid) or a continuous-but-not-as-ordered one (liquid).
Gases consist of molecules floating about freely (unbonded and unconstrained to each other) but if you only had a single molecule in a vacuum… there would be a distinct lack of other atoms by which to assess which phase it belongs to.
And since plasmas are gases where some fraction of molecules are ionically charged… i imagine you need a multiple number of molecules to assess whether they could be termed a plasma or not. (If a lone molecule was present, and it was charged, one would presumably call it an ion, not a plasma.)
I’ll check in with a physics professor on this topic. Hopefully I’m correct. 