I'd have expected that other-Sean-Carroll, in the other world that split off at the point of the observation, observed down, didn't he? (Since Carroll is a many

I'd have expected that other-Sean-Carroll, in the other world that split off at the point of the observation, observed down, didn't he? (Since Carroll is a many-worlds fundamentalist and insists that the unitary evolution of the Schrodinger equation is the underlying truth, with the apparent existence of this or that particular branch of the many worlds tree being some kind of epiphenomenon. Unless I misunderstood his claims.) In any case, I think many-worlders like Carroll would fall into the "perspectival" camp in the terms of the linked article: > A counterexample that allows for nonabsoluteness of observed events is the “many worlds” interpretation of quantum mechanics. In this view, our example wave function will branch into multiple contemporaneous realities, such that in one “world,” the system will come up heads, while in another, it’ll be tails. In this conception, there is no collapse. “So the question of what happens is not absolute; it’s relative to a world,” Ormrod says. Of course, in trying to avoid the collapse-induced measurement problem, the many worlds interpretation introduces the mind-numbing branching of wave functions and runaway proliferation of worlds at each and every fork in the quantum road—an unpalatable scenario for many. > Nevertheless, the many worlds interpretation is an example of what are called perspectival theories, wherein the outcome of a measurement depends on the observer’s perspective. The claim referenced in the article is that those who, unlike "perspectivists", prefer to think of the world we live in as objectively real, or in the article's terms believe in "absoluteness" of observations, will have to give up one of three widely held assumptions: 1) Bell nonlocality, which brings with it the assumption of free will on the part of experimentalists (Gerard t'Hooft can get off the bus at this point), 2) information preservation (information is never really destroyed, it just gets harder and harder to retrieve) and 3) local dynamics: "the transformation of the full system can be decomposed into transformations of its individual parts". I don't pretend to fully understand any of these three, but where the article looks at local dynamics as the weak sister my (uninformed) instinct would be to look harder at information preservation: if "wavefunction collapse" is objectively real, for example, why should the details of the pre-collapse superposed state be in-principle-retrievable after the collapse?