The aspect of inherent unity and connectedness of the physical reality manifests itself in several ways in modern science. In the 'double-slit experiment', when both slits are open, the light-waves going through them interfere with each other to form a pattern of alternating light and dark bands on a screen. When only one slit is open, the light-waves going through it illuminate the screen in the ordinary way. The great multitude of photons, of which a single photon eventually will be a part, distributes itself in one way if both slits are open.
The question is, assuming that a single photon goes through one of the two slits, how does it know whether or not the other slit is open? Somehow it does. An interference pattern always forms when we open both slits, and it never forms when we close one of the slits.