Rather, what we think of as a "solid" has very different definition than what we would intuitively think. But in the end, that's just semantics. (According to t

Rather, what we think of as a "solid" has very different definition than what we would intuitively think. But in the end, that's just semantics. (According to the linked prof. Moriarty, the "boundary" of a solid is the point in space where quantum degeneracy pressure is in balance with van der Waals forces – so there is a well-defined boundary!) Also, I think that "point particles" are a rather illusory concept. More like, interactions between particles are highly localized when observed by a macroscopic classical observer.