Fire, Civilization, and Planets

The world watched in horror this week as the great Cathedral of Notre Dame burned. As this ancient symbol of beauty and aspiration was engulfed in flames, our feeling of helplessness was heartbreaking.

As I reflected on my own emotions and all the different meanings this tragedy evoked, I finally came to a “long view”—which might bring us all some measure of comfort. Globally, we all were experiencing something rather ancient, stretching backward through time with roots in what it means to be human—and what it means to be embodied on a living planet.

A quick Google search of famous fires shows how often our greatest work in the effort of constructing civilization has fallen to fires. Parts of London were lost to devastating fires at least six times between 1130 and 1666. In its great fire of 1212, more than 3,000 people died, some of whom were trapped on that era’s version of London Bridge. The Great Chicago Fire of 1871 took tens of thousands of structures and left nearly 100,000 homeless. A year later, another great fire left 65 acres of Boston in ruin. Tokyo and San Francisco felt the one-two punch of earthquakes followed by devastating fires in the early years of the 20th century. And the grandparent of them all is the great fire of Rome in 64 AD. The fire raged for six days only to be reignited to burn for another three days, leaving two thirds of the city destroyed.

In our modern era, when professional fire-fighting is both a science and an established part of society, it’s harder for us to understand what fire meant in to peoples of the past. Individuals still lose homes to conflagrations today, but it almost never happens that entire cities—the fundamental unit and symbol of civilization—are lost. The collective experience of watching a whole city go up in flames was far more common and more extensive for most of our collective history.

This was primarily because in the past, the materials we had for building civilization were so much more combustible. While stone has always been available, wood was the only relatively cheap material available for building many densely packed cities. We build with what’s available at the time, and to a large degree, that has meant using the sturdy materials—like wood—that are themselves the product of life. And that realization leads us to consider the place of fire in life, and even on entire planets.

Oxygen plentiful, but combustible

Combustion is defined as the “rapid chemical combination of a substance with oxygen, involving the production of heat and light.” But consider for a moment that the only reason we have oxygen in our atmosphere is because life, in the form of blue-green bacteria, evolved a novel form of photosynthesis more than 2.5 billion years ago.

By learning how to use water as the basis for photosynthetic reactions, these creatures bequeathed the planet an oxygen-rich atmosphere in which “open air” combustion became possible. That meant that the energy stored in biomatter, be it dung or wood, could burn. It could become fuel for forest fires ignited by lightning strikes, or city fires ignited by a lantern kicked over by a cow. (The Great Chicago Fire was not started this way, but for more than a century, the legend made for a good story.)

Thus, for our kind of planet with an oxygen atmosphere, combustion is quick and easy to get started. Fire appeared to come naturally to our pre-Homo sapiens ancestors. It was in that way that fires were first tamed, becoming the energy source that would eventually be used in ways ranging from cooking to metallurgy. On Earth at least, taming fire would become a first step on the way to building civilization.

That is how the wheel spins. We live on a planet were fires are part of the landscape, and we used them to change the landscape in myriad ways. But it’s always been an uneasy relationship.

Fire gives, and fire takes. For me, the Notre Dame tragedy reminded us all of just how long, and how sometimes difficult, that relationship has been.


Adam Frank is a professor of astrophysics at the University of Rochester.