Both a matter of some fundamental science and a particularly elegant technology. The technology is the Australian Aboriginal firestarter. What makes it elegant is that it is simple, easy to use, makes a good demonstration of a physical principle, and is extremely obvious -- in retrospect. The way it works is that you take an airtight tube with a snugly fitting piston in it. Put the tube, with the piston at the top end, over some dry tinder. Then slam down the piston, while holding the tube hard against the ground.
The principle is that as you compress a gas, while keeping it insulated from the surroundings, it heats up. Compress it enough, and you get to the ignition point of your tinder. As far as I've seen, after doing a little looking when I saw the description of the Australian Aboriginal firestarter, they are the first people by some thousands of years to make use of the technology. Brilliant! elegant!
The next technology to make use of the principle, as far as I know, is the Diesel engine, late 1800s.
For our climate concerns, we don't deal with such extreme or rapid compressions. But the principle holds: If we take a blob of air, insulated from the surroundings and increase the pressure on it (because we're pulling it from lower pressure part of the atmosphere to higher), it warms up. The converse is also true -- if we decrease the pressure (by moving to a higher (lower pressure) part of the atmoshere), then the gas cools off.
This is another part of dealing with potential temperatures -- we'll get rigorous about by just how much the air warms or cools. But that's another note.
If you have other examples of technologies or cultures using air compression heating between the firestarter and Diesel engine, please do mention them here or by email to me at plutarchspam at aim dot net. (It's a valid address, the 'spam' in it is part of the name. You could also use the bobg at radix dot net that is in my profile, but I get so much unfiltered spam there that chances are good I'll miss your note.)
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