and intricate than what the metaphor suggests, and certainly the non-spatial (or pre-spatial) entities cannot be represented as simple corpuscular entities.

Wave-packet spreading
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The problem that we need first to consider is the evolution of the *probability of presence* (in space) of a microscopic entity, such as a single atom, when it evolves freely, i.e., when no external forces or other entities (microscopic or macroscopic) interact with it (apart the measuring system). The term “probability of presence” should be understood in the sense of the probability with which the microscopic entity in question lends itself to the creation of a spatial localization, in a given region of space $R$, at a given time $t$, through its interaction with a measuring apparatus [@Aerts1999; @Sassoli2012]. In quantum theory, this probability is given by the squared modulus $|\psi_t({\bf x})|^2$ of the wave function (or wave packet) $\psi_t({\bf x})$ (describing the state of the entity in question, at time $t$), integrated over the spatial region $R$, that is: $${\cal P}_t(R)=\int_R d{\bf x}\, |\psi_t ({\bf x})|^2.$$ What I am now going to do is to estimate the width of such wave packet in the simplest case of a hydrogen atom, which is the first 