Noctilucent
Clouds like oysters, nacred
blobs of rising light,
shining over sacred
petals of the night,
Crops of solar flares
that meddle in the sky,
illuminating lairs
of fireflies
That glide up trellis
and up stair
in the endless
summer, where
Lumens flare
like double suns,
optical illusions
and accidental airs
That blossom in
the Hubble’s lee
like Roman candles,
where moonlit trees
Are the gnomons
of the night, spirits
of the Stone Men
and Inuits
Who draw the shadows
in the gloom,
the mysterium
of our little room,
Moorings of the storm
where eddies flit
and exit in the wind
around the steady stars,
Axes of the curtains
and the jets that stream
above our hidden loom:
the underlying circuits
And divinities
that bloom in us,
the nocturnal circus
that clarifies the luminous.
Explanation
Night-shining or noctilucent clouds are illuminated by the sun when it is just below the horizon. They are composed of ice crystals that form on meteor dust and are most visible in summer at high latitudes, such as in Sweden, Ireland, or Alaska, when air becomes warm enough to ascend to great heights in the mesosphere, some fifty miles above the earth.
Warm air rises, and warmer air rises farther. So such air is a victim of its own success, brought to one extreme by the other extreme. In the high latitudes, it can be colder than minus 200 degrees Fahrenheit. Such extremely cold air meeting unusually warm vapor forms condensation, or crystals, through which the sun shines. Conditions have to be just right: enough meteor dust, the sun just set, and an observer in place at just that moment.