Temperature is a property of assemblies of particles, and in this case the “particles” are the bowling balls (dust, rocks), not necessarily atoms. Nothing in th

Temperature is a property of assemblies of particles, and in this case the “particles” are the bowling balls (dust, rocks), not necessarily atoms. Nothing in the formulation requires it to be atoms. Of course then you get rocks sitting at a different internal temperature than the temperature of the overall cloud of rocks, and yes, over time that would reach an equilibrium. However, heat transfer in space, for large objects, is slow enough that this can be a very long time indeed.