Who built the Holodecks?
Seriously, who actually made the holodecks? Where did they come from? My head-canon: Holodecks are alien technology that the Federation duplicates without understanding how it really works. Largely-separate power grids. Weird behavior in power outages. Poor safety controls. Different storage technology. Regular accidental sentience. Holodecks can accurately model unknown physics TNG’s “A Matter of Perspective” did this first, correctly simulating an energy converter prototype. Voyager used holodecks in “Threshold”, in order to model warp-ten travel.