If you have arrived here without reading this blog post, please do so first, so that you have the context for the images below.
Please note that the distance between A and B below is kept constant from drawing to drawing only for ease of comparison -- the scale here is completely irrelevant: the only thing that matters are the relations.
The imagination follows the consequences of the harmonic relationship as point P moves towards the right, through infinity, and back around from the left, constituting one cycle.
and then of course, we go back to #1.