Friday, August 11, 2017
Fire and Life
Recently a colleague in the history department at Northern stumped me. I am ashamed to admit this, as his question went directly to the matters I have been thinking about for years. The question was this: is fire alive?
It is a very good and obvious question. Fire must breathe. It consumes fuel and turns it into energy, just as living organisms do. It also produces waste. Is there an essential difference between a campfire and a living organism?
I didn’t think about this seriously until I was actually looking at a fire, after backpacking up into the Wind River Range in Wyoming. By then, the answer had occurred to me. I think that this is one of those questions that is a key to understanding. So here is my reply. Fire is almost the opposite of a living organism.
A fire begins, necessarily, with a situation of low entropy. Consider a glass of water with an ice cube floating in it on the dining room table. If I isolate the glass as a system in thought I note that the system is in a state of low entropy. All the cold stuff is in the ice cube; all the lukewarm stuff is in the liquid surrounding it. This is a highly ordered system.
As the ice begins to melt, the system becomes gradually less and less ordered. The water locked in ice warms up and releases its energy into the surrounding liquid. Eventually, the system is at equilibrium. All the water is at roughly the same temperature: a disordered state. The system has gone from a state of low entropy to a state of high entropy.
Fires follow a similar trajectory. I pile a bunch of firewood in the pit and set it alight. At that moment, the system is highly ordered. All the energy is in the wood and much less in the pit and the surrounding air (good thing, that!). As the wood burns it moves steadily toward a system of high entropy, which is why I have to keep adding more wood. Fire moves always in that direction: from low to higher states of entropy.
Entropic processes can be exploited to resist entropic processes. If I have a pot of water at the same temperature as the surrounding air (high entropy) and I put it on the fire, it will heat up. Now all the hot stuff is in the pot and the surrounding air is cooler (low entropy). Boiling water exploits entropic processes to resist entropy.
Living organisms do precisely that in order to continually recreate themselves. The sun is constantly bleeding its stored energy into space. The tree takes that energy and uses it to build its trunk and branches. I use its bones to build my fire. I pour the boiling water into a bag of freeze dried food, full of organically sequestered energy, and eat it. Being a warm-blooded creature, this allows me to resist equilibrium with the steadily cooling air around me.
Fire is a purely entropic process, as much as an ice cube melting in water. Living organisms exploit such processes in order to resist such processes. That is why I am alive and my campfire is not. I would add one other thing. Living organisms are always part of a lineage. I have a mommy and a daddy. A single celled organism has its predecessor. My campfire had none of the above. That seems to me to be more important that it looks.
I finish with a final, rather depressing note. My high school physics teacher said that the universe is dying a heat death. He meant that the cosmos as a whole is basically a campfire. We living organisms and all the bright lights in the sky will eventually burn out. All the energy in creation will be evenly distributed and nothing more will ever be done.
This is not something to be worried about. The earth will be uninhabitable long before that happens. It is a reminder to be astounded and grateful that such as ourselves should stand under this canopy of stars.