There’s a lot of dry wood in the forests around us. It stays there for a while. Only from time to time something happens that starts a fire.
Fill a room with a mixture of oxygen and hydrogen – at ‘room temperature’, and nothing happens. Strike a match and… you get a big noise and a little water. Don’t try this at home, you won’t live to tell the story. The noise is really big.
White phosphorus has to be kept under water. Whenever it gets in contact with humid air at a temperature above 30 degrees Celsius it starts to burn. And it cannot be extinguished in any other way than by submerging the whole thing under water.
Put a TNT stick (make sure it isn’t dynamite) into fire and it will simply burn. Fuse it properly and it will detonate whenever you ‘tell’ it to.
Let’s consider life now.
All the chemical elements, and a huge number of the organic molecules, which are the building blocks of any living organism have been around for eons while ‘life’ is a relatively recent occurrence.
Males and females – both animals and plants, roam around freely. Yet no offspring appears before something happens between a male and a female. This – the need for something to occur outside the individual organism, is valid also for bacteria – they need certain conditions to multiply, and viruses – which need the assistance of other, suitable, organisms.
Whenever conditions are right enough, sooner or later ‘life’ will surely appear. Or so it has happened all over our Earth. Till now, at least.
Whenever a living organism follows it’s normal set of instructions – its DNA remains fully functional, everything goes ‘as advertised’. If, by any reason, enough DNA is damaged beyond repair, the hell breaks loose. Being diagnosed with Cancer is enough to blow up even the most stable mind.
I’ve kept the most striking similitude for the last.
Both combustion and life continue only as long as certain conditions are met. Both need enough oxygen and fuel/nutrition.
There are also two big differences between them. One regarding ‘time’ – the successions of ‘moves’ which constitute the processes, and the other regarding ‘space’.
Combustion follows a set of pre-existing rules. The chemical composition of the combustible might change the ignition temperature but that’s all it can do. Or it may add – as it’s the case for explosives, the possibility of detonation. But, again, both combustion and detonation follow a set of rules which are valid ‘across the board’. For all combustible and explosive substances.
On it’s turn, life follows two broad sets of rules. It has to obey all those which govern chemistry and physics – read combustion and detonation, and, on top of that, it has it’s own set of detailed instructions. Which vary from species to species.
I’ve left for the end the difference regarding ‘space’ because this one is very simple.
‘Combustion’ will extend all over the place where combustible is ‘continuous’, in a single ‘event’, while ‘life’ is, by definition, about finite organisms which multiply to make ‘good use’ of the available resources.
This being the reason for which combustion stops whenever the combustible available in an enclosed place is exhausted while life can resist a certain period of ‘famine’.
nicichiarasa 