A high-altitude cloud that is luminous at night, especially in summer in high latitudes.
- One of them is something that I've never actually seen but I had seen pictures of; it's a thing called a noctilucent cloud, this is a cloud that occurs at about 86 kilometres, it may be present more often than we see it.
- ‘Humbug’ refers to natural phenomena such as heavenly bodies, noctilucent clouds, ball lightning, and man-made objects such as glowing blimps.
- Evidence of these changes comes from sightings of noctilucent clouds, very unusual clouds seen only in polar regions and known to be in the mesosphere.
Late 19th century: from Latin nox, noct- 'night' + lucere 'to shine' + -ent.
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