[LeGrande]

Actually the dispute continues as to whether the wave function collapse is a physical phenomenon or whether it is just an epiphenomenon.

Yes And I can quote wiki too : ) "Decoherence does not generate actual wave function collapse. It only provides an explanation for the appearance of wavefunction collapse. The quantum nature of the system is simply "leaked" into the environment. A total superposition of the universal wavefunction still occurs, but its ultimate fate remains an interpretational issue."

If you mean an observation by an observer "in" space/time cannot change the structure of space/time, physical laws and constants - I'd say that is probably true.

Agreed

If you mean an observation by an observer "in" space/time cannot change the world (collapse a wave function whether actual or epiphenomenal) - I'd say that is probably not true.

Our observations collapse the wave function.

Besides I disagree, the falling tree does make a sound even if no one is there to hear it. And I point to the sound waves in the cosmic microwave background radiation as evidence that sound occurred at the moment light (photons) came into existence even though there was no one "in" space/time to hear it.

I agree too. I don't think the moon disappears when I am not looking at it : )

I think the crux of our disagreement boils down to I think that the observer can determine the outcome of the wavefunction collapse. In other words if the experimenter is looking for wave properties that is what he can get, or if he is looking for particle properties he can get that too. The experimenter can't get both at the same time though, it is a choice that the experimenter makes.

It was explained to me this way. If you reach into a black box with a fork, you will pull out ice cubes and if you reach into the black box with a spoon you will pull out water. The choice between a spoon or a fork determines what comes out of the black box.

[Alamo-Girl]

Our observations collapse the wave function.

Everett's many-world theory disagrees with you.

I think the crux of our disagreement boils down to I think that the observer can determine the outcome of the wavefunction collapse. In other words if the experimenter is looking for wave properties that is what he can get, or if he is looking for particle properties he can get that too. The experimenter can't get both at the same time though, it is a choice that the experimenter makes.

It was explained to me this way. If you reach into a black box with a fork, you will pull out ice cubes and if you reach into the black box with a spoon you will pull out water. The choice between a spoon or a fork determines what comes out of the black box.

That is a good metaphor for wave/particle duality.

However, the "observer problem" goes far beyond wave/particle duality.