Clicked this thinking it was about the double slit experiment observer-effect. Maybe that's not exactly a paradox, but I still can't wrap my head around it.
1. Abandon for a moment the idea that we are special
2. Imagine what the most simplified agent that "experiences" things would look like. For example a simple machine that observed am experiment and reduces it into a simple "do I see interference bands or do I see only one band?" and records it to some simple memory.
3. Let the wave in superposition interact with the machine and compute what happens to the machine now that it is itself entangled with the wave
4. Very hard math
5. The machine is in a superposition state of various state, each observing the wave collapse
> Let the wave in superposition interact with the machine
This is the key point right, that an observation cannot be made without a very real, physical, interaction, that necessarily influences the thing being observed?
After the interaction your become part of the same quantum system and that affects what you can observe next.
When you become a system where the state is a superposition of "electron spin up + you see an electron spin up" and "electron spin down + you see an electron spin down" then you when you observe the electron in spin down you'll always see the electron as spin down because, you guessed it, the "you" in this story is the "you see an electron spin down" you of the superposition of yous
My gut says though, that the main problem is probably thinking it is ever possible to be outside the experiment.
Other than taking enough physics to get a EE degree, I don't know physics. One explanation I've heard from a physicist appeals to me. He said something like:
All the confusion about wave/particle duality is because we explain physics in terms of intuitions we have in our daily lives. Sometimes the analogy that is most convenient is to use a wave metaphor, and sometimes the best analogy is to use a particle metaphor ... but in both cases it is neither particle nor wave.
When I think of wave-particle duality, I think its just the expression of 2 facts. Matter waves show interference effects. Matter waves are only ever observed in a definite position, never in a superposition.
But position isnt special right? We never observe a superposition of momentum (move at 2 speeds) either. And neither are macroscopic states, we never observed an (1/sqrt(2))(alive + dead) cat either.
So evolution isn't observation and intermediate states aren't real.