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In the upper part of the atmosphere the kinetic temperature of air is of the order of 1000 K, even then one feels severe cold, why?

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  • $\begingroup$ feeling hot or cold is the body registering energy loss or energy gain, it is not a measure of temperature , it is heat transfer that the body evaluates. $\endgroup$
    – anna v
    Mar 23 '18 at 12:39
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"In the upper part of the atmosphere ... one feels severe cold" - I guess this statement requires some qualification, as this depends on whether one is exposed to sun radiation.

In the upper atmosphere (thermosphere starts at about 85 km), the air density is negligible for most purposes, and I don't think anybody has ever been at such altitude (without a spaceship or a spacesuit), and if people found themselves there, their immediate problems would be lack of oxygen and blood boiling, not cold.

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  • $\begingroup$ Yes. Well, the blood boiling does actually cause a rapid cooling as well, but that's not the primary problem it brings about... $\endgroup$ Mar 23 '18 at 15:44
  • $\begingroup$ Can you feel cold when you're dead? I think I'll go ask that tree that fell in the forest. $\endgroup$ Mar 24 '18 at 4:27
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As we go up in the atmosphere , the number of molecules per unit volume decreases . The quantity of heat per unit volume or the heat density is low . But the translational kinetic energy per molecule is quite large. As the kinetic temperature is the measure of translational kinetic energy, so the kinetic temperature is quite high in the upper atmosphere but one feels severe cold due to low heat density.

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The sensation of "cold" is really a measure of how rapidly a body is losing heat.

The thermosphere (extreme upper atmosphere) does have a high kinetic temperature, and its molecules do transfer heat to any cooler body they collide with. But since the density of the thermosphere is extremely low, the energy they transfer is also very low.

A body loses much more energy than it gains from the thermosphere, thanks to radiation exchange with deep space, which is at about 3K (-270C).

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  • $\begingroup$ I like this answer best. It answers the question: How can something I have less of make me cold? $\endgroup$ Mar 24 '18 at 4:29
  • $\begingroup$ @Alchimista that isn't what comment's are for. $\endgroup$ Mar 24 '18 at 16:08
  • $\begingroup$ So boring I thought you were asking in comment. I misunderstood you quoting for asking " how can .....". Sorry again I don't see well and miss the double dot $\endgroup$
    – Alchimista
    Mar 24 '18 at 18:36

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