For 20 years, half my work has been multiple exposure. Both on the fly, and running the film through the Camera multiple time. (Easy on a Nikon. Cock a manual Nikon, sprocket on right always lines up the same. Use same sprocket hole on film, carefully uptake slack on right spool. With lens cap on, advance to any frame you want with near pin-camera registration. You will have to map exposures on paper though to control outcome, grid viewfinder helps too)
Hilbert is a famous mathematician, he greatly influenced the Manhatten project scientists. Teller, Szalard sat before him. Hilbert convieved multiple dimensions or "Hilbert Space".
Most people think in 3-4 dimensions-- but Hilbert Space is much richer, and better describes the Universe.