I made a long-delayed redstone circuit using repeaters and a button, wired up to a (non-sticky) piston. The piston would push 1 sand block out of a giant pillar I was standing on (up to max height) to make me fall down along with the stack. It would also trigger some TNT laying around the base of the sand pillar. While standing on the top of the tower I could see some of the world dissapear (meaning the TNT had exploded, obviously). I fell down a couple of blocks along with the sand. The weird thing was: the TNT never dissapeared from my screen (whilst on top AND when I was at the base of the pillar). Basically there is TNT, some redstone circuitry and sand being rendered (and I could stand on them), but upon interacting (e.g. placing a button or a block) they would dissapear. (Basically some blocks were rendered (and you could stand on them still) while they were non-existant after a TNT explosion).