1) entangled particles are collapsed “instantaneously”. But it’s not really instantaneous because those particles can’t reach the initial observer/measurement until the speed of light.
2) Superpositions are collapsed which apparently causes different behavior than if they’re collapsed later. e.g. the double slit experiment, where measuring the electrons before the slit causes the interference pattern to disappear. This and Bell’s theorem are very unintuitive but they don’t necessarily break the speed of light.
What if electrons are shot through a very long double slit, where they may or may not be measured early on but the observers at the end don’t know this? This still doesn’t break the speed of light because once the electrons create the interference pattern which the observers can measure to determine if they are entangled, the electrons are already local to the observers.
Bell’s theorem just shows there is no one “hidden state” in entangled electrons before they are measured. The entanglement seems to create the relation “chargeA = !chargeB” without setting “A” or “B”, but when A is finally resolved, it still takes the speed of light for this information to reach B.
The only thing we know is happening for sure is interaction, which when studied using the so-called density matrices of the interacting subsystems gives insight into how any subsystem "sees" another one. You get all the "parallel universes" as separate terms this way, and see ways in which these terms evolve independently of each other and ways in which they can linearly interfere. This is all continuous evolution under the Schroedinger equation by the way.
You unfortunately won't get any satisfactory answer to this but you can definitely scratch the itch if you take the time to study some QM and decoherence theory.
AFAIUI any measurement necessarily interacts with the system, and that interaction changes the wave equation. Measurements are not different from other interactions.
IMO the word "measurement" is over-utilized in this space. My layman interpretation is A interacts with B, collapsing each other's waveform from the perspective of the other. At some point in the causality chain my eyeballs might be B, but there's nothing special about my eyeballs vs. a sensor vs. a piece of dust.
Someone more knowledgeable might be able to say what interpretation this would be considered, and how it differs from competing ones.
