Thermal Flows

In this piece, I want to think about heat as thermal flow, rather than as a property of something. This shifts focus from the ‘thing’ that is hot, to the vibrancy, movement and exchange of energy itself: warmth, intensity or dissipation. I want to do this because so often in our daily talk about heat we speak about objects, absolutes and finite measurements: “this day is a hot one”; “the maximum temperature exceeds 30 degrees”; “we are experiencing a heatwave”. Yet, implicit in all these apparently black and white presences and absences of heat is an awareness of change and variance in intensity and magnitude in relation to particular spaces, captured at particular times. Understood in this way, heat becomes thermal flow.
 
How can we pay better attention to such thermal flows, and what implications do they have for an imagination of space, place and time, and what living with heat really means? This think-piece is loosely inspired by thermodynamics, but translates that initial impetus into how heat emerges and has effects informed by a more-than-human and poststructuralist ontology and epistemology. It should be noted at the outset that this imaginary is culturally situated. Very different ontologies and epistemologies of heat, and indeed of thermal flows, have emerged in different cultural contexts (see Yavari 2021; Howes 2005; Messer 1981), which transgress, oppose and exceed the ontology of thermal flows presented here.
 
To elucidate this, I outline a series of four principles and follow up with a reflection on what these mean for space, place and time. The first principle of thinking about heat in terms of thermal flows is contingency. Heat does not come from nowhere, nor does it move freely, but is shaped by that which it moves through. As such, heat is never simply present or absent, but actively generated, produced, dissipated or removed as an effect of something else. This also means that heat is neither ‘neutral’ nor ‘background’ even though it is often relegated to this role. Even the warmth of the sun, relatively constant over billions of years, is contingent, and has an expiry date. When we think of the heat our bodies move through on a daily basis, it is the sum of a vast array of complex processes – solar insolation making its way through various gasses in the atmosphere, trapped and re-radiated in different wavelengths from different surfaces such as grass and concrete, the heat produced by running car engines, and the heat produced by human bodies, all come together to heat the atmosphere and objects around us, merging and interacting with the metabolic heat produced by our own bodies. If any of these heat-generating and transferring process are altered, the materials will change the thermal flows we encounter. Such changes have both causes and consequences, and this inherent contingency – and our ability to intercede in such relations — opens up apparently neutral, objective processes to questions of ethics and politics.

 
The second principle of thinking about heat in terms of thermal flows is relationality, or the relative-ness of heat. In thermodynamic terms, everything above absolute zero (-273.15°C) is technically ‘hot’ (Starosielski, 2021); -273.15°C marks the complete absence of thermal energy and it is not physically possible for anything to get cooler than this. Rather than getting into a discussion of thermodynamics per se, I want to use this observation to make the point that what we term hot or cold in everyday speech is usually relational – even the absolute claim that “today is a hot day” relies implicitly on the experience of other days as colder to have meaning. Due to its intrinsic embeddedness in experience and comparison, heat is also relative in the sense of being codified and understood in particular ways in particular contexts: Thirteen degrees is “hot” in the arctic circle but also “cold” in the sub-tropics; a rise of 5 degrees in the daily maximum is common in temperate regions, but extreme in tropical regions. What this means is that, even when, in and of themselves, thermal flows (and any changes in its intensity or magnitude) may be the same, their location in space and time co-creates their significance, physically and semantically. Implicit here too is that thermal flows are relational in their meaning depending on who or what is sensing them: different amounts of heat and the media through which they are transferred has a different significance for a building than for a person; different cultures have different norms of how much physical discomfort is tolerated, and different behaviours and norms of dress which shapes how much impact conditions have on them, and therefore whether they are perceived as extreme (‘hot’ or ‘cold’) or not (de Vet, 2017; Jerstad, 2016).
 
The third principle for thinking about thermal flows is dynamism. When thinking about thermal flows, we should assume they have potential to modulate and transform. In this sense, we need to be careful of assuming that heat (or cold) is uniform and unchanging. It is not. Just as heat has effects on the matter it moves through, it also changes in itself as it flows through matter. Thermal flows then are dynamic, and any apparent stasis in thermal conditions is in fact actively achieved through a careful balancing of material and energetic relationships. Imagine sitting outside on a sunny day, wearing a black pair of jeans and a white T-shirt; you can feel the fabric on your legs heating up intensely, while your torso remains cool. Both parts of your body (and pieces of clothing) are hit by the same type and amount of radiation, yet the white fabric reflects particular wavelengths of light while the black fabric absorbs and transforms the the same wavelengths of light into thermal radiation. When we think about heat and thermal flows then, we must always think of it as being-in-process – always potentially changing in its form and intensity. This also opens up thinking to seeing thermal flows – and energy more broadly — as moments of potential for intervention; we can wear light coloured clothing or paint roofs white to intervene in energetic (and thermal) flows, such that, while they appear “natural” and beyond the scope of human activity, they are in fact (at least somewhat) open to modulation.
 
The fourth principle of thermal flows is that heat ‘does work’ and has consequences. While this is inherent to thermodynamics (heat converted into work), it is also important to translate it into a social, more-than-human framing that whenever heat flows through something it has an effect. Most obviously, it may be warming up or cooling down that object… but that is rarely all. In the case of infrastructures made from metal materials, for instance, increases in thermal flows might result in the metal expanding – railway lines lengthening, power lines sagging – and contracting as they cool. Heat might also expand certain materials – water turning to ice and busting pipes; or conversely, water warming enough to evaporate as puddles disappear from roads or sweat evaporates off skin, taking some of the heat with it. More complex work is also done by heat – pleasant ambient temperatures may help keep human bodies in safe operating ranges for basic bodily functions, but as human bodies overheat, not only do these chemical and physical processes start to collapse, but behaviours change, and tempers fray. In these ways we see that thermal flows almost always have a (material, energetic and social) consequence. Sometimes thermal flows and their relations to certain processes are so regular that these consequences disappear into the background (Oppermann & Walker, 2018), it is only when the regular patterning of these thermal flows are disrupted that they become noticeable – for example, when the central heating breaks down in a care home. When considering heat or cold then, we must ask ourselves, what work is this thermal flow doing, and what intensity and type of flow is required to maintain such effects?
 
The contingency, relationality, dynamism and consequences of thermal flows has wider implications for how we think about space, place and time. Starting with space, this means that, rather than being made up of matter in a purely dimensional sense, such matter – and the space it constitutes – is animated, interrupted, transgressed, repositioned and transformed by thermal flows, and, indeed, energy more broadly. Furthermore, while material spaces can be neatly delineated, thermal flows may transgress and erode their boundaries. In this sense, all space is more connected than we may typically realise. Think of the heat produced by air-conditioning units: the ‘space’ of our homes is cooled, but the thermal exchange and mechanistic energy that produces that interior cool creates, in balance, heat on the ‘outside’ of our homes, in another space, where heat builds up and travels through the streets, floods the urban environment, moves into bodies of pedestrians warms the exterior of other homes. In this way, thermal flows blur spatial boundaries and weave spatially ‘bounded’ activities into the fabric of life at its most extensive definition, from the body to home to city to the atmosphere.
 
What does this mean for place? If space becomes place when meaning is attributed to it or cultural values are inscribed in it, and space is simultaneously co-constituted by thermal flows, it follows that all places are implicitly characterised by thermal flows of certain intensities or qualities. Furthermore, the character of that place could change as thermal flows change, and a place may be the amalgam of various and varying thermal flows over time. Think of a mountain campsite. As a space – a mere geographic location — it might be characterised by temperatures typical to its geographical location and altitude, but as a place it is characterised by dynamic and multiple thermal flows: the crisp cool air of the morning tempered by the warm rays of the sun; the baking heat of the afternoon and crunch of dry leaves; the chill of the night beaten back by the heat from a campfire. Place, produced by all of these meanings tied to a certain space, and the interaction of energy with the materials and objects contained within it, is deeply shaped by thermal flows.
 
What does this mean for time? The dynamism of thermal flows can certainly be measured as change over time, typically clock-time, which might be used to describe losses or gains or movements of heat lasting from seconds (in the case of your microwave dinner) to millennia (the greenhouse effect). However, thermal flows also have their own inherent temporality which produce an evental time, made by the effects and durations of their movement and transformation. In this sense, the time that ‘matters’ (literally and figuratively) for the melting of the icecaps is not really seconds, but decades; the time that matters for the overheating of the human body is not decades but hours. Time itself comes to matter then as a metric of thermal flows and their consequences.
 
In sum then, in talking about heat and cold, we might challenge ourselves to think more expansively about them as thermal flows. Rather than static characteristics of objects or things, heat and cold are both shorthand for thermal flows. Thermal flows are, as the name implies, far from static: they are dynamic, contingent, relational. They both are, and have, consequences, doing work on other things and are, themselves, transformed in the process. They shape space, place and time. This makes them immensely important insofar as thermal flows can be actively intervened in to recalibrate the emergence of certain changes in matter, certain energetic experiences, and of space, place and time.
 

References

de Vet, E. (2017). Experiencing and responding to everyday weather in Darwin, Australia: the important role of tolerance. Weather, Climate, and Society, 9(2), 141-154.
Elden, S. (2013). Secure the volume: Vertical geopolitics and the depth of power. Political Geography, 34, 35-51.
Howes, D. (2005). Skinscapes: Embodiment, culture, and environment. The book of touch. Oxford: Berg, 27-39.
Jerstad, H. (2016). Mundane Energies: the working body as a heat source in the Indian Himalayas. Anthropology Today, 32(4), 7-10.
Messer, E. (1981). Hot-cold classification: theoretical and practical implications of a Mexican study. Social Science & Medicine. Part B: Medical Anthropology, 15(2), 133-145.
Oppermann, E., & Walker, G. (2018). Immersed in Thermal Flows: Heat as Productive of and Produced by Social Practices. In Y. Strengers & C. Maller (Eds.), Social Practices and Dynamic Non-humans: Nature, Materials and Technologies (pp. 129-148). Switzerland: Springer.
Starosielski, N. (2021). Media Hot and Cold. Durham: Duke University Press.
Yavari, M., ed. (2021). Hot and Cold Theory: The Path Towards Personalized Medicine. Switzerland: Springer.