I am in the process of trying to understand, in basic terms, how the many-worlds interpretation (MWI) might explain the EPR experiment. In this context it is hoped that the scope for what appears to be almost unlimited speculation might be reduced. It seems that the original EPR experiment of 1935 was initially trying to disprove Heisenberg’s uncertainty principle. Later this description was modified, by Bohm (?), into a pion system disintegrating into an electron and positron, which then puts the issue of locality into better perspective. Based on limited reading, see links below, it seems that the MWI (1957+) assumes that the wave function does not collapse and does not depend on an observer. As such: Does the MWI argue that the wave function has to have some form of physical existence? Presumably, no physical verification of this wave has ever been detected? While the following example is more than a little contrived, it is only seeking to clarify a limited number of basic issues within the context defined above, if at all possible. The example is orientated around two observers on two space-stations, e.g. A & B, separated by 10 light-years. Therefore, any ‘normal’ signalling would take a minimum of 10 years, if restricted to light speed. At a location close to A, a quantum system is evolving in time, according to Schrodinger’s wave equation (?), such that a composite pion particle with zero charge and spin disintegrates into an electron and a positron, where each must ultimately have opposite spin. While presumably still in a quantum entangled state, the electron and positron are described as ‘propagating’ in opposite directions, through the vacuum of space, towards A & B respectively. Does it make sense to describe the pion particle disintegrating into an electron and a positron, while in a quantum superposition wave state? Can quantum waves propagate energy and momentum, if only a mathematical construct? On the assumption that the original pion was close to A, the electron arrives at A in a matter of days, while it would take the positron 10+? years to reach B. At A, an observer measures the spin of the electron, but within the context of the MWI, it is assumed that this observer now has to split into two realities, i.e. one who measures up-spin, and one who measures down-spin, as the MWI appears to suggest that the wave function doesn’t collapse, therefore both spin probabilities have to exist, albeit in different realities. Is the description above basically valid within the many-worlds interpretation? In the first split reality of A, it would seem that there is an electron with down-spin, such that there must be a positron with up-spin heading towards B; while in the other split reality, there is an electron with up-spin with a positron with down-spin heading towards B. As such, there appears to be the suggestion that two split observers must eventually exist at B, i.e. in different but associated realities, destined to measure a positron with the corresponding spin, but this interpretation then appears to raise a number of questions: As an entangled system, do both spin permutations instantly exist when the observer at A makes the measurement on the electron? When do the two split observers at B come into existence? Does the inference of the MWI ultimately propagate outwards to become many-universes and, if so, is the propagation assumed to be instantaneous? Does the MWI account for the apparent duplication of energy in each reality? Does it make sense to assume that a quantum superposition exists in normal spacetime? Sorry, this is possibly too many questions for one post, but I wanted to just table the issues I am trying to resolve within this thread as a whole. Thanks Initial cross references: Wikipedia: http://en.wikipedia.org/wiki/Many-worlds_interpretation http://en.wikipedia.org/wiki/Quantum_decoherence The Everett FAQ: One of the reasons in raising this thread was to help in the process of understanding all the arguments put forward in this link: http://www.hedweb.com/manworld.htm PF Threads: Two recent PF discussions involving many exchanges. https://www.physicsforums.com/showthread.php?t=522754&highlight=EPR+many-worlds The first post of this thread is worth a read. I haven’t really reviewed all 655 entries.May be somebody can point to any that are particularly relevant. https://www.physicsforums.com/showthread.php?t=497228&highlight=EPR+many-worlds Thread discussed some of the perceived problems. Again, I have not yet reviewed all 210 entries, but didn't come across any that seem to specifically addressed my more basic issues.