many thanks for the detailed answer, John! Yes, I will look up Mermin's
lecture. I have read his pieces before, and he really is a fascinating as
well as lucid author.
One question regarding your answer. You wrote:
"3) Following Mermin's lecture there is a question about the
role of an anthropomorphic "observer", sometimes referred to
as "Wigner's friend". As a general rule, anything involving
anthropomorphic observers is misleading and worse than useless.
This applies to "observers" in special relativity as well as
in quantum mechanics."
How should one think about "observer" in QM and relativity? The term is
widely used but what does it really mean? Or perhaps Mermin's lecture will
clear it up.