dietz%usc-cse@USC-ECL@sri-unix (12/09/82)
When the cigarette fire reaches your lips it doesn't "scald" them. Under high enough partial pressure of oxygen (perhaps less than one atmosphere) the human body itself will sustain combustion. Anyone have the exact point at which this happens? As I recall it is a very important consideration in using hyperbaric chambers. An interesting aside... I recall reading that if the partial pressure of O2 in the Earth's atmosphere was just fractionally higher then wet (green) wood would burn very easily, and we wouldn't have any plants.
REM@MIT-MC@sri-unix (12/10/82)
From: Robert Elton Maas <REM at MIT-MC> Re "if Earth had more Oxygen" -- You're mistaken. It's the plants that made the oxygen in the first place. At first it was a toxic waste product that quickly killed off most lifeforms (things like tetanus for example that can't stand oxygen). Later creatures evolved protective mechanisms, and creatures that could burn organic materials in oxygen to produce energy evolved, for example animals. If the plants ever made so much oxygen that their own bodies burned up, there'd be a big fire and afterward there wouldn't be so much free oxygen around. In fact that sort of happens now. Forest fires are natural. When there are too many trees crowded together too tightly and they are too dry, a fire starts and burns some of them down, decreasing the number of easily flammable trees around. Luckily the whole planet doesn't dry up at the same time, so these fires seldom spread over whole continents and thus seldom cause extinctions, and also luckily there's lots of lightning to start fires at all sorts of randomtimes when not enough dry timber has built up to have much of a big fire at all. Of course this negative-feedback loop could be unstable, but fortunately it isn't in Earth's case, it nicely limits itself to where just the driest of the plants in the driest of climates catch fire, the rest just get eaten by bacteria when they die, and the oxygen level stays at a reasonable level (at least we think it's reasonable. I'm sure Tetanus would disagree).