The first stanza

The first stanza of “The Second Coming” is a powerful description of apocalypse, opening with the indelible image of the falcon circling ever higher, in ever-widening spirals, so far that “The falcon cannot hear the falconer.” The centrifugal impetus described by those circles in the air tends to chaos and disintegration—“Things fall apart; the centre cannot hold;”—and more than chaos and disintegration, to war—“The blood-dimmed tide”—to fundamental doubt—“The best lack all conviction”—and to the rule of misguided evil—“the worst / Are full of passionate intensity.”
The centrifugal impetus of those widening circles in the air, however, is no parallel to the Big Bang theory of the universe, in which everything speeding away from everything else finally dissipates into nothingness. In Yeats’ mystical/philosophical theory of the world, in the scheme he outlined in his book A Vision, the gyres are intersecting cones, one widening out while the other focuses in to a single point. History is not a one-way trip into chaos, and the passage between the gyres not the end of the world altogether, but a transition to a new world, or to another dimension.