Beelzebub is deep in conversation with the captain of the spaceship Karnak which is currently stalled, awaiting the dispersal of the gaseous tail of the ‘madcap’ comet Sakoor. Beelzebub has taken the opportunity afforded by the delay to explain to his grandson, Hassein, all about the strangely underdeveloped spirituality of the ‘three-brained’ creatures of the planet Earth, in whose solar system, Oors, Beelzebub was for so long exiled. The conversation with the captain was all about the evolution of spaceship propulsion systems. The first system discussed was very basic, a combination of two elements that ‘filled’ the universe. It is not enlarged upon in any depth. The system that...