A semicomplete multipartite digraph is obtained by replacing each edge of a complete multipartite graph by an arc or by a pair of two mutually opposite arcs.
Fremen are able to use Maker Hooks to steer a sandworm by hooking into gaps in the sandworm's plating, forcing the creatures to instinctively move in the opposite direction.
They came to the conclusion that immediately after the Big Bang, in one direction, the universe arose that we know and live in and in the opposite direction the anti universe was born.