Ok, so let me generalise a bit... a good operating temperature for humans is perhaps 10 to 30 degrees C, roughly speaking.

So shift that up 20 degrees to 50 degrees and we're in serious trouble?

So what if we drop it 60 degrees to minus 50?!!!!

http://www.msn.com/en-gb/news/other/pass...ailsignout

Don't your eyeballs freeze?!!!

No, your eyeballs won't freeze at -50C. Humans (with sufficient protection, natch) work in temperatures approaching -90C.

But you're essentially correct: -50C and +50C are at the extreme limits of human endurance.

Boru

But that begs the question, why can most people only operate in a fifth of that range?

(November 26, 2014 at 4:58 pm)lifesagift Wrote: But that begs the question, why can most people only operate in a fifth of that range?

Define "operate". You won't be nearly as efficient at the extremes.

In extreme cold or heat, without proper protective clothing/shelter, you will die very quickly (literally within hours in the most extreme conditions). Even with proper protection from the weather, precautions have to be taken.

In siberian Russia, YOU take off plane.

Ok, still working on it

(November 26, 2014 at 4:58 pm)lifesagift Wrote: But that begs the question, why can most people only operate in a fifth of that range?

Because human beings - like all other organisms - have limited adaptability. Functioning in that temperature range is one of the things that make us human. There are plenty of organisms which function in other temperature ranges, pressure ranges, chemical environments and so on (look up 'extremeophiles - fascinating stuff).

Like everything else, we fit into an ecological niche. This is why bracket fungi don't grow in deserts and why jellyfish aren't arboreal.

Boru

(November 26, 2014 at 4:53 pm)BrianSoddingBoru4 Wrote: But you're essentially correct: -50C and +50C are at the extreme limits of human endurance.

Boru

Human normal metabolic function adds heat and yet human body can not operate more the 2-3 degrees above its normal operating temperature of 37C. So human body must be able to shed heat. This become impossible when ambient temperature exceeds 40-45C on a sustained basis, so the human would die without mechanical cooling.

Likewise humans can only produce so much heat per hour and the speed with which humans lose heat increases with lowering ambient temperature. Without extensive thermal insulation humans would gradually suffer lowering body temperature and eventuaally die when ambient temperature drops below 0C.

So the real operating temperature range for humans without additional artificial insulation and cooling is more like 0-40C.

If you add artificial insulation and artificial cooling, the range expands dramatically. The best example is a space suit. A human in a space suit can survive -150C to 150C, sometimes both at the same time.

With great application of industrial resource it is conceivable humans can live on a sustained basis between -150C and 150C.

It's not the extremes our bodies can handle that would get us if the earth got either hot or cold. The problem would be food production.

(November 26, 2014 at 5:29 pm)BrianSoddingBoru4 Wrote: This is why bracket fungi don't grow in deserts and why jellyfish aren't arboreal.

Boru

Not so fast my friend...

From what I understand, it's theorized that we may have evolved a great deal of our innovation as an animal due to climate instability in Africa. I forget the ages, but the climate in Africa where we evolved was unstable and varied dramatically for a million years or so. Looking at that in hindsight, it becomes obvious that we developed to tolerate certain temperature ranges because we didn't need to adapt to more extreme conditions throught our evolutionary history. We didn't start moving out of Africa and into less hospitable climes until very late in our evolutionary history. Now that we depend on machines, clothing and technology to assist our climate control, we'll probably never directly evolve to take advantage of more extreme climes, but our technology may not have such limits.