- #1
Derek P
- 297
- 43
In another thread, @Nugatory asked
"how exactly does it turn out that both spacelike-separated observers end up in the same world without some appeal to non-locality?"
Worlds are defined by their observed macroscopic values. They separate through decoherence. It is a physical process. Since decoherence is so fast, it effectively propagates as a sphere expanding at the speed of light. Thus the whole universe does not split, the splits are in the future light cones from the two observations. Only where the cones intersect have both worlds split. Alice can know that Bob's worlds have separated, her world is, however, not yet split by anything over at Bob's place.
"how exactly does it turn out that both spacelike-separated observers end up in the same world without some appeal to non-locality?"
Worlds are defined by their observed macroscopic values. They separate through decoherence. It is a physical process. Since decoherence is so fast, it effectively propagates as a sphere expanding at the speed of light. Thus the whole universe does not split, the splits are in the future light cones from the two observations. Only where the cones intersect have both worlds split. Alice can know that Bob's worlds have separated, her world is, however, not yet split by anything over at Bob's place.