夜里发光的——专指那种太阳落尽后仍在天顶泛着电蓝色的云：地球最高的云，挂在大气层边缘。 Night-shining — above all, of the electric-blue clouds that keep glowing after sunset: Earth's highest clouds, hung at the edge of the atmosphere.
Night-shining — above all, of the electric-blue clouds that keep glowing after sunset: Earth's highest clouds, hung at the edge of the atmosphere. 夜里发光的——专指那种太阳落尽后仍在天顶泛着电蓝色的云：地球最高的云，挂在大气层边缘。
词源etymology
拉丁语 nox, noctis（夜）＋ lucere（发光）——「夜里发光的」。 构词平平，履历不凡：它被气象学选中，去命名地球上最高、最奇怪的云。
Latin nox, noctis (night) + lucere (to shine) — “night-shining.” Plain word-building, uncommon résumé: meteorology picked it to name the highest, strangest clouds on Earth.
背景the story
夜光云悬在约八十公里的中间层——比普通云高十倍，高到日落之后阳光仍能从地平线下 斜照上去，把它点成电蓝色：地面已经入夜，它还在白昼里。
它的档案有个著名的悬案：1885 年才被首次记录——恰好在喀拉喀托火山大爆发两年后。 是火山把水汽与尘埃送上了天，还是此前根本无人抬头？学界至今仍在争论。 一种云的「出生年份」，成了大气科学的一桩公案。
Noctilucent clouds hang in the mesosphere, near eighty kilometers up — ten times higher than weather, high enough that after sunset the sun still reaches them from below the horizon and lights them electric blue: night on the ground, daylight up there.
Their file holds a famous cold case: first recorded only in 1885 — two years after Krakatoa. Did the eruption loft the water and dust that made them visible, or had nobody simply looked up before? The debate continues. The birth year of a cloud remains an open case in atmospheric science.
中文里的邻居neighbors in chinese
气象学译名就叫「夜光云」——三字全等，这是术语的本分。 诗的那半，中文早有储备：「天光云影」在白昼，「夜未央」有夜无光； 最近的意境是苏轼那句**「庭下如积水空明」**——夜里发亮的不是云是月光， 但那份「夜与光同在」的错愕，是同一种。
The meteorological Chinese is exactly 夜光云 — three characters, a perfect technical match, as terminology should be. For the poetry half, the nearest Chinese mood is Su Shi’s 庭下如积水空明 — the courtyard “limpid as standing water” at night: what shines there is moonlight, not cloud, but the small shock of night and light coexisting is the same shock.
Past eleven and the northwest sky still held a noctilucent shimmer, like a screen that wouldn't sleep. 自拟例句 our own example, not a quotation Noctilucent season is midsummer's consolation prize for the missing stars. 自拟例句 our own example, not a quotation 词典词（MW／OED），科学与自然写作的正规军；noctilucent clouds 是标准术语。 写夏夜、写高纬度的旅行，它自带一层大气层边缘的凉。
A dictionary word (MW/OED), regular army in science and nature writing; “noctilucent clouds” is the standard term. In midsummer-night and high-latitude travel writing it carries its own chill from the edge of the atmosphere.