At the root of reality there's some "wavy" equation that propagates changes at a certain speed (of light). The exact form of the equation is of little significa

At the root of reality there's some "wavy" equation that propagates changes at a certain speed (of light). The exact form of the equation is of little significance, only its "waviness" matters. This waviness is often called causality. Such equation in a confined area, any area, always and necessarily has many repetitive modes where the original state repeats itself after a certain interval, but all thosr modes exist in abstract, i.e. potentially. An external driving force allows to select one of those modes. This is probably a tautology, but maybe someone will find it interesting.