About dwarven physics: I actually spent a few minutes today wondering how dwarves can mine out a tile, use the rock to build a wall elsewhere, dismantle the wall and get the rock back, build a workshop out of it, dismantle the workshop, fire the same rock in a catapult, and in the event of the ammo surviving carving three mugs out of it. And basically every other weirdness involving material quantity seeming very variable.
I came to the conclusion that walls aren't actually made of the material they represent. They're composed of shadow matter that fills a fourth dimension only known to dwarves, and therefore called the Dwarf Dimension. For each DF tile, there exists a slot carved in shadow matter that only Dwarves can properly manipulate. Any material inserted into such slot will act like a seed and cause the shadow matter of the tile to mimic the contents of the slot, causing the wall or floor to spontaneously appear as a result of the change. Similarly, the deconstruction (or mining) happens by dislodging the seed, causing the shadow matter to forget the wall and disappear.
Of course, this could apply to workshops as well - how on earth does a dwarf create a workshop from a single rock of granite without changing the rock in any way? Simple - the architect carves the workshop out of shadow matter, and the granite will act as a seed that causes the shop to form.
I also think that mechanisms are wired through the Dwarf Dimension.