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## Main Question or Discussion Point

Id like comments on this statement because although I see it as true, the fact that MWI isnt generally accepted while QM is suggests it may be false.

The way I see it, if QM is an accurate description of the universe (i.e. it is not just an approximation of some underlying theory), then MWI is the only logical explanation. This comes mainly from the phenomena of superposition and decoherence. Observation in QM is the act of a macroscopic object interacting with a particle in a superposition. The wave function of the particle collapses into a delta function and it is the delta function that is observed. The way observation takes place is that some particle in the macroscopic object interacts with the observed particle and then interacts with all of the other particles in the object (which then at almost the speed of light interacts with the entire planet).

The problem with this is that there appears to be a discontinuity in the act of observation. A single particle interacting with another particle does not collapse either wave function. What happens, according to QM, is that a two particle system is made that itself is in some superposition (of course the system's wave function can sometimes be two delta functions).

These two results seem to be contradictory, since the macroscopic object interacting with a particle is simply a large number of particles interacting with each other. The only way to resolve this "paradox", that when YOU interact with a particle it appears to decohere but when a particle interacts with another particle neither appears to decohere, is to accept MWI. This provides an answer to this problem by saying that when a particle interacts with another particle, the local universe splits into each possible collapse and from the particle's "view", the other one has decohered (and it is always decohered). This explains why when we interact with a particle it appears to decohere by saying that the universe splits around us and in each universe the particle has decohered. To an observer outside of the light cone surrounding the event however, the entire system would be in a superposition.

The way I see it, if QM is an accurate description of the universe (i.e. it is not just an approximation of some underlying theory), then MWI is the only logical explanation. This comes mainly from the phenomena of superposition and decoherence. Observation in QM is the act of a macroscopic object interacting with a particle in a superposition. The wave function of the particle collapses into a delta function and it is the delta function that is observed. The way observation takes place is that some particle in the macroscopic object interacts with the observed particle and then interacts with all of the other particles in the object (which then at almost the speed of light interacts with the entire planet).

The problem with this is that there appears to be a discontinuity in the act of observation. A single particle interacting with another particle does not collapse either wave function. What happens, according to QM, is that a two particle system is made that itself is in some superposition (of course the system's wave function can sometimes be two delta functions).

These two results seem to be contradictory, since the macroscopic object interacting with a particle is simply a large number of particles interacting with each other. The only way to resolve this "paradox", that when YOU interact with a particle it appears to decohere but when a particle interacts with another particle neither appears to decohere, is to accept MWI. This provides an answer to this problem by saying that when a particle interacts with another particle, the local universe splits into each possible collapse and from the particle's "view", the other one has decohered (and it is always decohered). This explains why when we interact with a particle it appears to decohere by saying that the universe splits around us and in each universe the particle has decohered. To an observer outside of the light cone surrounding the event however, the entire system would be in a superposition.