David Quinn wrote:I understand the aesthetic appeal of this type of model, but again, what about the absurdities?
Well, really, I agree. You are calling it "absurd", I was calling it "weird". The problem is not so much that
this model is absurd, but that they
all are.
The problem is in constructing a model - a metaphor that we can understand - that agrees with the equations. The equations are very well verified. They just don't agree with our intuitions.
Your examples of what you consider absurd, actually radically understate the point. In Many Worlds, a new universe is generated every time a subatomic particle interacts with another subatomic particle in such a way that it must assume a definite state.
For instance, if you are lying on the beach wearing polarized sunglasses, every time a photon hits the lens it has to "decide" which way it is polarized, which determines if it goes through the lens or not. This happens many times per second. I don't know exactly how many, but let's say a billion times a second. Overall, the earth alone would be generating many trillions of new universes every second.
I earlier said an infinite number of universes, but actually I'm not sure if it is truly infinite or just a number so extremely huge that it hurts my head to think about it (trillions per second times billions of years times billions of worlds - each new universe also spawning trillions of new ones...)
But from another point of view, is having many quadrillions of universes more absurd than having two?
And is having two more absurd than having one?
...
To change the subject a bit, here's the part that I think is difficult, or philosophically interesting.
Let's say we have two interpretations, one being multiple worlds (which rejects contrafactual definiteness) and another being one which rejects local realism, say the Copenhagen interpretation.
Further, let's say that there is no way to tell, from a physical experiment, which is correct. They are both consistent with the same set of equations. You can not tell whether you are in a Copenhagen universe or a Many Worlds universe, based on the physical evidence. (This may or may not be true.)
That means there is no difference between the two models. They are both
saying the same thing. Contrafactual definiteness
means the same thing as local realism. From our point of view, they seem like two radically different propositions, but the physical universe doesn't see it from our point of view. It just is what it is.