Ash Wyllie writes:

Look up _radiational cooling_.

I'm familiar with it, and with blackbody radiation.

Space is in the single digits absolute, and the atmosphere is pretty
much transparent to radiation.

The atmosphere not only absorbs and reflects the blackbody radiation
emitted by most objects on the ground at ordinary temperatures, it
also emits radiation of its own (as does anything with a non-zero
absolute temperature).

Objects will radiate energy trying to heat up interstellar space,
and cool in the process.

The surface of the planet is not part of interstellar space.

Everything on the surface of the Earth cools through emission of
radiation, but aircraft do not do this to any greater extent than
anything else, and they don't cool to subfreezing temperatures in air
that is above freezing.

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