I think I understand than an example of Newton's first law (intertial frames) would be a single asteroid in vaccum with no other bodies around, a comet in such free space or likewise. Then I think the asteroid or comet would continue just moving in the direction of the tangent vector from the original force if no other force acts. But would that theory also apply to non-newtonian gas or a non-newtonian fluid in the same situation? Or considering a particle small enough that quatum mechanics should apply instead of newtonian mechanics, would it still be apprioriate to presume that newton's first law will hold for microscopic particle in a vacuum?
Or would non-newtonian bodies, fluids and gases move randomly instead and we should believe that newton's first principle only holds for objects affected only or mostly by gravity?