I have a question on a particular version of the double slit experiment (I know there are many). I am not sure I understood it correctly, so I am going to explain it in a very basic manner and in my own words. You tell me if my explanation is correct or not, and then I have another question. This particular version of the experiment had many mirrors and half-silvered mirrors with light bouncing this way and that, and also some kind of splitter which split the light into what I believe were entangled particles. I don't want to go into the details of that (indeed my eyes glazed over reading about it), and I don't want you to go into the details of it either. All that is important to me is that I get the basic 'gist' of it, and the outcome. 1) Split light into entangled photons. 2) We'll call the first photon the 'control.' It simply has a path directly to the 'wall' if you will, where it will leave a mark as either a particle (a 'dot') or a wave pattern. This is also the shortest path in the experiment, so this photon will arrive and strike before any other photon. 3) The second photon goes through the double-slit, and a detector which can detect which slit it went through lies between the slits (after it has passed through) and the 'wall' where it will strike. we either choose to activate the detector after the photon has passed through the slits but before it hits the wall, or we don't. If I understood the experiment correctly (and I probably didn't, which is why I am here), the 'marks' left on the 'wall' by the two photons ('control' and 'other') always 'match,' meaning they are both either always a 'dot' or a wave. It is as if (one interpretation) the first 'control' photon to hit has the power to go back in time and alter its decision on whether to strike as a wave or a 'dot' depending on what choice the observer made and therefore what choice the 'other' photon made. Do I have this correct? If that is correct, here is my question. Could we not make the path of the 'other' (non-control) photon much longer, to where we would have seconds to minutes to determine what the first photon (control) did? For instance bounce the non-control photon off a mirror on the moon for all I care. The point is to simply see what the first photon does ('dot' or wave) then make the choice to do the opposite for the other photon and see what happens. My first prediction is that you will say I have totally (or largely) misunderstood this whole thing. My second prediction is that you will say that both photon will strike as a wave no matter what we do. But would anyone say that our choice for the 2nd photon (bouncing off the moon or whatever) will somehow affect the first photon we saw hitting seconds or minutes ago, i.e. could we witness 'dot' for 1st photon, select 'wave' for 2nd photon, then see the recording for the 1st photon magically change to wave as well? Or would we magically lack the free will to make the 2nd photon do the opposite of the first photon? Thank you for your patience, and I await your response.