in $10$ s its approximate width will be of $500$ km, and so forth. In other words, the *effective speed* with which the radial dimension of the center of mass wave packet grows, is approximately $50$ km/s, that is $180,000$ km/h, which is a speed of all respect, and corresponds, in our previous metaphor, to the maximum speed of the diver (from our ordinary spatial perspective this is however only a *potential* speed, and certainly not an *actual* speed, as it is not associated with a body moving through our ordinary space).

Disassembling the body
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Summarizing, for a hydrogen atom we have determined the approximate behavior of that part of the wave function which describes the potential spatial localization of its center of mass. In doing so, we have ignored for simplicity the relative motion between the proton of the nucleus and the orbital electron, as well as their spins. More precisely, we have calculated how the width of the center of mass wave function varies over time in (configuration) space, due to the so-called phenomenon of the *spreading of the wave function*, which can be understood as being a consequence of Heisenberg’s uncertainty principle.

What is important to 