Decoding the Mystery of Wave Function Collapse

We provide a reasonable explanation for measurement where no wave function in the sense of quantum mechanics is collapsed. The wave functions of the particles in the measuring device should be considered together with the measured particle as one system. The measurement is actually a physical process, which makes the wave functions of different paths orthogonal. The collapsed wave function is just an equivalent one to explain certain physical phenomena. There is no physical transition or process from the wave function in quantum mechanics to the equivalent one. Our understanding of measurement also provides reasonable explanations for both EPR paradox and the experiments of delayed quantum eraser