On this day, the sun

The poet begins by marking a specific day, emphasizing a particular moment in time.

Appeared- no, not slowly over the horizon

The appearance of the sun is described, but the poet clarifies that it is not the gradual and typical rising of the sun over the horizon.

But right in the city square.

The sun’s appearance is not in the natural setting but is situated directly in the city square, suggesting an unnatural event.

A blast of dazzle poured over,

Describes a sudden and intense burst of light or brilliance.

Not from the middle sky,

The dazzling light is not originating from the usual midday sky, indicating an unusual and extraordinary event.

But from the earth torn raggedly open.

The source of the intense light is revealed to be the earth itself, torn open violently.

Human shadows, dazed and lost, pitched

Describes the immediate aftermath of the event, where people are disoriented, confused, and thrown in various directions.

In every direction: this blaze,

The chaos caused by the event is emphasized as people are scattered in all directions. The term “blaze” suggests both intense light and the destructive nature of the event.

Not risen from the east,

Reiterates that the extraordinary light is not a natural sunrise from the east.

Smashed in the city’s heartAn immense wheel

The city is metaphorically described as having its heart smashed, and an enormous wheel is introduced, symbolizing destruction.

Of Death’s swart suncar spinning down and about

This wheel is further described as belonging to Death (swart suncar), suggesting a destructive force spinning in every direction.

In every direction.

Reiterates the widespread and all-encompassing nature of the destruction.

Instant of a sun’s rise and set.

Describes the event as occurring within the brief span of time it takes for the sun to rise and set, emphasizing the suddenness of the devastation.

Vision-annihilating flare one compressed afternoon.

The brilliance of the light is so intense that it annihilates vision, describing the event as a compressed, intense occurrence happening in a single afternoon.

And then?

A pause in the narrative, prompting the reader to consider what happens next.

It was not human shadows that lengthened, paled, and died;

Contrasts with the natural phenomenon of shadows lengthening in the evening; here, it refers to the human shadows being affected by the catastrophic event.

It was men suddenly become as mist, then gone.

Describes the fate of the people, who, in an instant, turn into mist and vanish, signifying the immediate and complete destruction.

The shadows stay:

Despite the disappearance of the people, their shadows remain.

Burned on rocks, stones of these vacant streets.

The enduring impact is captured as the shadows are burned onto the surfaces of rocks and stones, which now define the empty streets.

A sun conjured by men converted men into air, to nothing;

Reflects on the irony that the same sun (nuclear explosion) created by human beings has turned them into nothingness, into thin air.

White shadows singed on the black rock give back Man’s witness to himself.

Describes the lasting marks of destruction – the white shadows on the blackened rocks serve as a testament to the destructive power of humanity, a witness to man’s capability for immense harm.