It all began when i had this question which sounds absolutely logical: The higher above sea level we go, the colder it gets, but the higher we go, the closer to the sun we are. So how can it get colder? If not hotter, it should at least maintain the same temperature. The answer is simple, if you know some physics of course. The higher we go, the lower the pressure it is. When a gas is compressed (its pressure is increased), it gets hotter. On the opposite, when it is de-compressed (like it happens when we go higher), it gets colder.
This is exactly how the fire pistons work. It has an air-tight piston with a very dry piece of cloth inside. When the air is compressed inside, it rapidly increased its temperature to the point of ignition! Fire pistons are not new to campers and survival enthusiasts, but did you know that the fire piston sparked the discovery of the diesel engine???