It's alive, it's alive!

by Neil Fraser, February 1993

Students in most elementary schools are introduced to "the five qualifiers of life". These five rules of thumb are designed to help determine whether an object is alive or not. The five rules are:

  1. Does it move?
  2. Does it eat and excrete?
  3. Does it react to stimuli?
  4. Does it grow or repair itself?
  5. Does it reproduce?

[Photograph of forest fire]With a little thought it is easy to confirm that all these so-called "laws" apply to humans. One can also use these rules to demonstrate that an organism as simple as lichen is alive. However, these rules are not perfect, and the clinching proof of this imperfection is fire.

Fire can move from room to room in a burning house (rule #1). It consumes flammable items and oxygen while excreting ashes and carbon dioxide (rule #2). Fire demonstrates its ability to react when it is fed quantities of water or gunpowder (rule #3). Anyone who has seen a forest fire can attest to the fact that fire can grow (rule #4). Fire can reproduce by throwing sparks outside the domain of the parent fire, and thus potentially starting another fire (rule #5). Thus, according to these rules, fire is alive!

The obvious conclusion is that the five rules are at fault. On the other hand, why are we so sure fire is not alive? Fire is clearly not sentient or intelligent, but neither are organisms like lichen. Indeed, the similarities between a forest fire and lichen growing on a rock are uncanny. They both start growing from a single location. They grow outward in an expanding circle, feeding on the nutrients around them. Then they both run out of nutrients in the center of their circular patch and the center starts to die leaving an ever-expanding ring. This process continues until all the nutrients on the surface have been consumed. Then there is a pause while the surface replenishes its covering of nutrients. To bridge the gap between two stones, lichen is continuously emitting spores which attempt to start a new organism where they land. A forest fire emits sparks which are carried high by the fire's own updraft. The sparks then rain down on the surrounding area, thereby allowing the fire to cross rivers and other obstacles.

One apparent difference between fire and lichen is that although they can both jettison 'seeds' that create offspring, lichen can only be created from those 'seeds', whereas fire can also be started by lightning, cigarette lighters, and photon torpedoes. However, this is not entirely correct. It is not true that lichen can only be created from spores. Once upon a time lichen had to be created from scratch (whether this was done by the complex mechanisms of evolution, or in an instant by a god is irrelevant). Fire would appear to be simple enough for it to be created from scratch much more easily than any DNA or RNA-based life form. Indeed, the concept that life-forms cannot be spontaneously created by nature is a new one. A couple of centuries ago it was believed that mice could spontaneously appear given the correct conditions. This idea is correct, though the process takes a few billion years. In the case of fire the idea is literally correct. Fire, like any other life form, may either be created from a parent, or it may be evolved from scratch. It is just a matter of scale.

The question remains: is fire a life form on the order of lichen? It is a strange possibility, but not one to be dismissed as absurd. After all, if a forest fire is alive, might the stars not be sentient?


This piece was written during my last year of high school. The English teacher graded it without reading it.
Photo credit: Alaskan Type I Incident Management Team

Last modified: 12 November 2000