Such synchronicities occur, he theorized, when a strong need arises in the psyche of an individual. He described three types that he had observed: the coinciding of a thought or feeling with an outside event; a dream, vision or premonition of something that then happens in the future; and a dream or vision that coincides with an event occurring at a distance. No one has come up with a definition that has superceded his, although there has been debate on whether events linked to precognition and clairvoyance should be included as synchronicity.
Some scientists see a theoretical grounding for synchronicity in quantum physics, fractal geometry, and chaos theory. They are finding that the isolation and separation of objects from each other is more apparent than real; at deeper levels, everything -- atoms, cells, molecules, plants, animals, people -- participates in a sensitive, flowing web of information. Physicists have shown, for example, that if two photons are separated, no matter by how far, a change in one creates a simultaneous change in the other. (Source: flowpower.com)