In this post, I pointed out that even though the phrase "copy the brain" occurs all over the Internet, my post might be the first in history to state that it is "impossible to copy the brain," an illuminating observation about the pervasive assumption that brains can be copied.
"Wigner's Friend is impossible"
"Macroscopic quantum superpositions are impossible"
Obviously, I’m not the first person to doubt that they are possible, but the fact that the above phrases yield nothing (until you remove "not possible" or "impossible," yielding thousands of results) should tell us something. It is practically established doctrine in the philosophy and foundations of physics that the Schrodinger’s Cat and Wigner’s Friend thought experiments, along with the ability to measure a macroscopic system in quantum superposition, are possible in principle.
The thing is – they’re not.
Here is my newest YouTube video, entitled “Why Macroscopic Quantum Superpositions are Impossible in Principle.” The concepts are elaborated in preprints here and here, with a more comprehensive explanation of (my current understanding of) quantum mechanics in this blog post.
A brief (13-minute) version of the above video can be found here: