I've posted a similar question here before, but to no avail. My question is, what is the cause for the propagation of a matter wave? In the same sense that oscillating electric and magnetic fields carry light across space (for lack of a better explanation), and every wave propagates through a medium of some sort i.e. sound through air, light through spacetime. What causes the propagation of a de Broglie wave? And what does a de Broglie wave propagate through? Also, if one adopts the copenhagen interpretation that this wave represents probability densities, what actually is the cause for this evolution of probabilties? I understand Schrodinger's equation describes this evolution, but as far as I understand it doesn't explain the fundamental root cause for this evolution. Also, please don't post any links to Wikipedia articles, there's a reason I come here with these questions after reading these articles.