It is known that light is a wave of propagating electric and magnetic fields (that does not require any medium, so please do not throw in any luminferous aether into this discussion) Like all waves when light waves interfere destructively, they (the resultant electric and magnetic fields) cancel out at the region, but continue to propagate and pass through each other as if nothing happen Similarly for water waves (let's ignore the non linear ones such as deep ocean waves for the purpose of this discussion) and waves on the string, where at region of destructive interference, the displacement of the water molecules and string molecules are zero. The waves (periodic disturbance of the displacement of the molecules that carry it, not sure if this is a good way to phrase it) propagate through each other as if nothing happened Now my question is Assume: 1. Two electrons (thus not particle A or B in our previous discussion in a previous thread, hence no such issue of the wavefunctions residing in different Hibert Space hence they cannot interfere) So we knew that if we mod square the wavefunction, we obtained the probability of finding the particle represented by the wavefunction From the Davisson-Germer experiment, we learnt that electrons have wave like properties and form interference pattern like light waves. Doing the maths, if we mod square the wavefunction at the region of destructive interference, ideally we expect there is zero probability of finding an electron My question is, as far as the current tread of mainstream physics, what is actually interfering that can result in a change of probability of finding the electron? Or more concisely, light waves (and all waves in general interfere) because the two waves have differing phases so (my understanding) 1. Light waves (the differing in phase is caused by the difference in oscillation of electric and magnetic fields, where one light wave might be leading the other) 2. Mechanical waves such as water waves, waves on string, 'Mexican Wave' (the differing in phase is caused by the difference in the periodic disturbance in a sequence of particles (in the general sense) that form the wave, again one might be leading the other) BUT 3. Matter waves/De Brogile waves: (The differing in phase is caused by the difference in oscillation of ???, which is shown mathematically in the wvafunction. But what exactly is this ??? that is not even a physical entity like an electric field) Please supplement more info if I have left out something by accident thanks! P.S. From this rather recent journal article http://physics.aps.org/articles/v6/58 The wavefunction (actually the probability distribution) of hydrogen is imaged Thus the wavefunction is really there, but what is the physical meaning of the phase of a matter wave? which so far the only thing observable from it is how when two wavefunctions in the same Hibert Space (i.e. particles with sufficiently identical properties) interfere with each other, result in a probability distribution that differs from the two wavefunction alone?