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Przekrój
Right now, there are over 10,000 active fires worldwide. In fact, you, Dear Reader, are burning too, ...
2019-06-17 10:00:00

Everybody Burns
The Creative Chaos of Combustion

Everybody Burns

The British comic Eddie Izzard expressed it best: “Shiva was the God of Creation and Destruction. Which is a good god to be. Whoom [creates thing]. What do you think? Do you like that? You don’t like that? Whoom [destroys thing]. If you’re just the God of Creation, you’re going Whoom [creates thing]. What do you think? Do you like that? You don’t? All right, I'll put it in the garage.”

Read in 11 minutes

Traditional iconography presents Shiva the Destroyer as a close cousin of Agni, the god of fire, “with a tawny beard, sharp jaws and burning teeth”; he feeds on wood, and smoke is his flag. His creative aspect was expressed in turn in dance. Therefore, the most complete image of creation and destruction in the Hindu world is that of Shiva dancing in flames. The fire that creates.

Each cell of our body is indeed a kind of micro-Shiva.

After all, metabolism is nothing more than a continuous cycle of destruction and creation. The human body, as well as any heterotrophic bacteria that you can grow on a sweetened Petri dish, bases its functioning on one fundamental equation. One molecule of glucose and six molecules of O2 give six molecules of CO2, six molecules of H2O and energy. Although the actual chemical reactions that are executed in the process can be extremely complex, the basic logic is expressed in that simplified equation. And do you know what this process is called? Combustion.

To a chemist, the concept of ‘combustion’ means any process involving the release of energy, especially if this is accompanied by the release of heat and light. The light of the human body is much less spectacular than the light of a match, as it is emitted in infrared, rather than the visible range. Yet the idea is still the same. If we were to observe at an atomic scale all that goes on during the combustion of a fuel, be it cellulose in a match or glucose in a human cell, we would simply see how oxygen molecules ‘pick off’ carbon molecules one after the other from a given organic compound. Every such reaction would be accompanied by a slight tugging movement, which on an appropriately large scale would simply equate to heat.

Thirty-six point six Celsius

Therefore, we can imagine the human body as a fireplace running around on two feet, in which fuel fed through the mouth is gradually burned at a strictly-controlled pace, monitored by a thermostat located in the hypothalamus of the brain. A person of average height who does not exert any special effort burns around 50 kcal an hour. This means that this person needs to be supplied with fuel having an energy value of about 1200 kcal to merely maintain the status quo. If we were to execute a rather unhealthy yet biochemically elegant sugar-based diet, we could supply the required daily calorie dose with 194,000 crystals of regular table sugar (sucrose). That’s a bit more than two crystals a second, which fully and literally evaporate, because they are converted into carbon dioxide and water vapour that leave our bodies forever. All this fuss to maintain our existence. Any additional activities, from picking your nose to creating an oil painting, mean that more crystals need to be burnt. If you want to understand how metabolism works, simply imagine these two little crystals of sugar dissipating in the air, two with every passing second.

To live, our body needs to constantly destroy not only the small particles of the world surrounding it, but also parts of itself. Each day, billions of cells in the human body are digested and dissolved in body fluids in a process referred to as programmed cell death. The technical term for this is apoptosis, which is a Greek word meaning ‘to fall off’ (like leaves, for example). Cells of the skin, brain, liver, intestines or lungs die in this manner. On the one hand, this ensures constant cell replacement and keeps the tissues fresh, while on the other, apoptosis sometimes plays the more noble role of the sculptor of our anatomy during foetal development. The most famous example are the ‘paddle-like’ hand plates that develop in the human embryo around day 33 of pregnancy. Only later do the primordia of finger bones develop, and afterwards, the cells between the fingers die. The fingers should already be separated by day 54 of pregnancy. If, however, some stubborn group of cells decides not to commit honorary suicide, the child will be born with conjoined fingers.

The body of an adult should hold a strict balance between cell division, when one cell becomes two cells, and apoptosis, when one cell becomes zero cells (there are no other possibilities to change this ‘life balance’; a situation in which zero cells became one cell happened only once in the history of life on Earth). The prevalence of cell death over cell division is the basis of Parkinson’s disease, to give just one example, while a tumour is nothing more than a structure built of excessively multiplied cells.

Last example. You know the saying: “No pain, no gain”? The phrase was made popular, or, as some claim, even coined, by Jane Fonda, who would repeat it like a mantra in her fitness exercise video, released in 1982 as Jane Fonda’s Workout (the VHS cassette version sold the greatest number of copies ever in the history of the medium). The term gain here refers to increased muscle mass, and in this sense, it is still used in bodybuilding circles. The term pain on the other hand, refers to, well, the muscle pain associated with any really solid workout. The other saying used by Fonda was: “Feel the burn!” Exactly. To create thicker muscle tissue, the older thinner tissue simply needs to be pulled.

Creative chaos

There is a beautiful branch of physics that allows us to express these intuitive feelings in a quantitative and – what is becoming quite rare – intuitively comprehensible manner at the same time. I speak of thermodynamics.

Initially, thermodynamics was used to describe the conversion of energy in steam engines. Yet with each passing decade, it would prove helpful in describing more and more natural phenomena. Today, it is one of those fundamental super-branches of science, and its tentacles penetrate absolutely every area of world knowledge, from chemistry and biology to earth sciences and outer space. The key point about a world in which many fundamental issues of thermodynamics are concentrated is that in every real physical process, part of the energy is dissipated, most often in the form of heat. To put it simply: there is no such thing as an engine that does not heat up.

Engineers who struggle with this truth are for the most part fighting for the performance of their ‘engines’ (which do not need to be engines in the precise meaning of the word). Any friction or heat, grinding or wear, any banging, knocking and hissing are the empirical effects of energy dissipation. The noiseless sliding doors and quietly humming powertrains of spaceships that appear in science fiction films constitute a demonstration of technical progress no less convincing than a teleportation machine. Indeed, it is nearly impossible for us to imagine that we board a spaceship built by a super intelligent extra-terrestrial civilization, and on our way to the office of the President of the Galaxy we walk past a technical room in which the characteristic clatter of an old diesel engine resonates.

However, in the mid-20th century, it was revealed that the diffusion of energy (or, technically speaking, its dissipation) also had a creative aspect. Many of the most beautiful forms of order in the universe are created in so-called dissipative systems in which energy ‘poured out’ of a certain process is ‘poured into’ spatial structures.

A canonical example of this phenomenon is turbulence. Let’s imagine we are observing from above a stream flowing around a medium-sized rock. If the water is flowing at a lazy snail’s pace, it gently goes around the rock from both sides, and the separated streams smoothly join back together right after without any additional phenomena. However, if we were to inject a bit more energy (kinetic) into the system and the water were to accelerate, a vortex starts to appear, sometimes in a very complex and quite aesthetic configuration. For example, in a very narrow range of velocity, we can observe the so-called ‘von Karmann vortices’, which separate alternately once from one side and then from the other, with opposite rotation direction (‘cyclone’ and ‘anticyclone’). Leonardo da Vinci’s notes contain beautiful sketches of such vortices. If the water starts flowing even faster though, the stream will start to bubble and splatter on the rock, and we end up with one big bubbling surge without any sophisticated forms of order.

This story illustrates the core principle that if we are on the lookout for interesting and sophisticated phenomena, the flow of energy can neither be too small nor too big. If not enough energy flows through the system, we have stagnation. Yet if there’s too much, we have complete randomness and noise. Somewhere between these boring extremities is a narrow range, referred to sometimes as the ‘edge of chaos’, where things start to get interesting. Each one of us can recreate yet another classic visualization of this phenomenon in the comfort of our own homes, even at this very moment. All you need is a leaky faucet.

Representing stagnation in its purest form is a closed faucet, which emits a sound of, well, silence. And what sound do we get when we open the tap all the way? We get what is almost pure noise. Hiding between these two uninteresting extremities is a fascinating area of creative chaos. Let’s start by gently opening the faucet, in such a way that water starts to slowly drip at a steady pace. Plink…plink…plink… Slowly, we increase the flow until we get ‘plink plink plink plink’. Now we need the steady hand of a safe-cracker. Lurking in the narrow range between quick plinks and the moment in which the drops of water come together to create a stream is the regime of chaos. Two plinks. Short pause. Three plinks. Two plinks. Pause. One plink. Plink plink… plink… plink plink plink… plink plink… plink plink… plink… plink plink plink… and so on, into eternity, in a sequence that even the mightiest of supercomputers in the world would not be able to foresee, but which is in no way random in the common meaning of the word.

Believe it or not, the dripping faucet experiment is the subject of hundreds of articles, written mainly by mathematicians specialized in chaos theory, and with each year, new forms of order are found in the sequence of plinking drops of water (this experiment was introduced into the world of science by eccentric biochemist Otto Eberhard Rössler, one of the intellectual fathers of the chaos theory; he became famous in June 2008 when he filed a lawsuit against the administration of the Great Haldron Collider for having allegedly brought a threat of calamity onto the inhabitants of Earth due to mini black holes generated in the collider).

Let it burn!

It’s hard to find a more fitting demonstration of the creative power of destruction – and of the rule of the golden mean while we’re at it – than natural fires in forests and grassy ecosystems. As this article is being written, Global Forest Watch reports that exactly 10,077 fires are raging in the world, most of them due to natural causes. Once we stifle our innate fear of its deadly force, we come to realize that fire takes on an array of important ecological roles. The authors of “Fire in the Earth System”, a general overview article published in Science in 2009, argue that the biosphere of our planet would even be consigned to oblivion if we would in some way thwart all the fires that break out. Fire regulates the level of oxygen and carbon dioxide in the atmosphere, constitutes one of the links in the global cycle of phosphorus, is an agent that controls the spread of forests and grasslands, while for many plants, fire is even a required factor for reproduction.

Shore pine, for example, has adapted to fire through evolution, and its cones open in high temperatures when the fire melts the layers of sap that keep them sealed. After a fire in the forest, it starts to sprout very quickly, overpowering other plants. Many experts have even put forth the assumption that its especially thin bark is an adaptation to increase the probability that the tree will fall over and feed the fire. The easily flammable eucalyptus oils probably take on a similar role in accelerating the spread of fires in the Australian bush. Also growing in Australia is the byblis – its seeds ‘awaken’ from a dormant state under the influence of smoke.

Simply put, Mother Nature has fires pencilled into the budget. A report published in 2006 analysed the cause of the increased number of especially intense fires in the western United States. One of the main hypotheses is… the human fear of fire. It seems that the most effective and certainly least expensive method of fire risk management is to simply let a fire burn out naturally. Let’s go back to the figure mentioned above: we have 10,000 fires raging throughout the world today. Over the course of a year, this figure fluctuates from 5,000 to 40,000. The vast majority of these fires do not constitute a direct threat to people, yet diligent fighting of these fires, often life-threatening, means that a constantly growing pile of flammable materials remain in the environment. And only when these materials start to burn later on – which is unavoidable from the perspective of coming decades – could a real catastrophe occur.

The other extremity are of course fires initiated by people, due to their stupidity and carelessness, malice or the mistaken belief that ‘we know better’. It looks like we don’t know any better after all. According to estimations made by scientists, fires have been erupting on our planet for at least 400 million years, or since the time that the first plants appeared on land that had sufficient amounts of biomass to maintain a fire. People have been trying to control this process for only a few thousand years, guided not so much by fear as by intuition, which sometimes leads us to a dead end.

Our aversion to fire is, of course, the result of the fear for our lives, but it is also due to purely aesthetic reasons. Scorched earth and charred remains of trees are an unpleasant sight for us – one we would like to avoid – while from a purely biological point of view, it is simply a healthy consequence of one of the natural phenomena that does not have any long-term negative effects. After all, in only a few years, which from the perspective of the evolution of the biosphere is but a blink of the eye, a forest will be growing in the same place once again.

In the report quoted above, the authors call on us to ‘make friends with fire’, tempting readers with a picture of a splendid northern hawk-owl (Surnia ulula), posing on a burnt stump amid young plants sprouting from the scorched earth. The caption below the photo informs us that this species is particularly prevalent in forests recovering from a fire, while you’ll never see a northern hawk-owl in a forest saved from a fire. The bird eyeing us from the pages of the report does not in any way remind us of the triumphant Shiva dancing in flames. Its calm yellow-black eyes seem to be saying: “Don’t panic, people. It’s only a fire.”

 

Translated by Mark Ordon

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Łukasz Lamża

is a philosopher of nature who writes popular scientific articles, particularly in “Tygodnik Powszechny”. He’s specifically trained in astrophysics and cosmology, but fortunately he sometimes comes down to Earth.