possible worlds that split off when the photon was created
I don’t think this is a very good way of thinking about what happens. I think worlds appear as fairly robust features of the wavefunction when quantum superpositions get entangled with large systems that differ in lots of degrees of freedom based on the state of the superposition.
So, when the intergalactic photon interacts non-trivially with a large system (e.g. Earth), a world becomes distinct in the wavefunction, because there’s a lump of amplitude that is separated from other lumps of amplitude by distance in many, many dimensions. This means it basically doesn’t interact with the rest of the wavefunction, and so looks like a distinct world.
I don’t think this is a very good way of thinking about what happens. I think worlds appear as fairly robust features of the wavefunction when quantum superpositions get entangled with large systems that differ in lots of degrees of freedom based on the state of the superposition.
So, when the intergalactic photon interacts non-trivially with a large system (e.g. Earth), a world becomes distinct in the wavefunction, because there’s a lump of amplitude that is separated from other lumps of amplitude by distance in many, many dimensions. This means it basically doesn’t interact with the rest of the wavefunction, and so looks like a distinct world.