Looking around, the public is largely ignorant of one of the most vital forces driving modern technological development: thermodynamics, the branch of physics that sets out the rules governing the relationships between heat, or thermal energy, and other forms of energy. Everyday life will once again be affected by what happens in its laboratories.

The first law of thermodynamics – also known as the law of energy conservation, or, more practically, as the law of no free lunches – plays an underlying role in many technological developments. According to this law, energy is conserved. It neither create nor destroy energy, but merely interconvert it between one form and another. The principle finds practical use in power plants, where fossil fuel, nuclear reactions or renewable sources of energy such as photovoltaics and wind power are used to generate electricity (eg, to push electrons through a circuit). But the principle is also central to the engineering of efficient technologies. Before the development of a technology one form of energy might be wasteful, after the development of the technology the same form of energy could be used efficiently, thereby minimising the amount of energy lost in the conversion process.

An even more important concept introduced by the second law of thermodynamics is that of entropy, a subtle measure of disorder. It states that, in an isolated system, the total entropy always increases with time. None of this is very illuminating – except for one fact about the second law. It is only because of the inevitable increase in entropy of such engines that engineers have to struggle so hard to extract energy from a fuel. They do so by minimising friction or other irreversible processes through which a larger fraction of useable energy gets lost as heat.

But it also finds a variety of applications outside the realm of producing energy. In materials science, there are many examples where thermodynamic principles are used in order to develop new materials with bespoke properties for a wide range of applications, from lighter and stronger airplanes, through more efficient consumer appliances to smarter skin patch implants. Thermodynamics can enable this by offering a fundamental understanding of the behaviour of one material in response to another, thereby enabling us to predict how a material will perform under given conditions, leading to the discovery of novel and previously unavailable materials.

Today, thermodynamics is also a focus of public attention. It figures in efforts to counter climate change. Researchers are using thermodynamic models to analyse the distribution of energy on Earth and to forecast the enduring effects of anthropogenic greenhouse gas emissions. The better we understand the thermodynamic processes driving climate change, the more precise our climate models will be – and the easier it will be to shape the responses of policy makers and to find effective mitigation strategies. 

In summary then, the laws of thermodynamics are powering innovation in fields as diverse as engines to viral vaccines. By exploiting our expanding knowledge of thermodynamics – both in terms of understanding its universality and in how complex systems leverage thermodynamics to achieve their own goals – we are developing new technologies that are more efficient, sustainable and resilient. Thermodynamics will therefore remain a powerhouse of innovation in the 21st century. Given its role in physics, it will continue to have a central position in the scientific understanding of the world as well as in the technologies we rely on for life, health and ease, not just this century but likely far into the future.

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