Category Archives: Thermodynamics

Boltzmann’s brain

Ludwig Boltzmann developed a statistical explanation of the second law of thermodynamics by defining entropy as being proportional to the logarithm of the number ways in which we can arrange a system [see ‘Entropy on the brain‘ on November 29th 2017].  The mathematical expression of this definition is engraved on his head-stone.  The second law states that the entropy of the universe is always increasing and Boltzmann argued it implies that the universe must have been created in a very low entropy state.  Four decades earlier, in 1854, William Thomson concluded the dissipation of heat arising from the second law would lead to the ‘death’ of the universe [see ‘Cosmic heat death‘ on February 18th, 2015] while the big bang theory for the creation of the universe evolved about twenty years after Boltzmann’s death.  The probability of a very low entropy state required to bring the universe into existance is very small because it implies random fluctuations in energy and matter leading to a highly ordered state.  One analogy would be the probability of dead leaves floating on the surface of a pond arranging themselves to spell your name.  It is easy to think of fluctuations that are more likely to occur, involving smaller systems, such as one that would bring only our solar system into existence, or progressively more likely, only our planet, only the room in which you are sitting reading this blog, or only your brain.  The last would imply that everything is in your imagination and ultimately that is why Boltzmann’s argument is not widely accepted although we do not have a good explanation for the apparent low entropy state at the start of the universe.  Jean-Paul Sartre wrote in his book Nausea ‘I exist because I think…and I cannot stop myself from thinking.  At this very moment – it’s frightful – if I exist, it is because I am horrified at existing.’  Perhaps most people would find horrifying the logical extension of Boltzmann’s arguments about the start of the universe to everything only existing in our mind.  Boltzmann’s work on statistical mechanics and the second law of thermodynamics is widely accepted and support the case for him being genius; however, his work raised more questions than answers and was widely criticised during his lifetime which led to him taking his own life in 1906.

Sources:

Paul Sen, Einstein’s fridge: the science of fire, ice and the universe.  London: Harper Collins, 2021.

Jean-Paul Sartre, Nausea.  London: Penguin Modern Classics, 2000.

Fridges slow down time

Photograph of the interior of a large domestic fridgeWe sense the passage of time by the changes that occur around us (see ‘We inhabit time as fish live in water‘ on July 24th, 2019) and these changes are brought about by processes that generate entropy.   Entropy is often referred to as the arrow of time because forwards in time is always the direction in which the entropy of the universe increases, as demanded by the second law of thermodynamics (see for example ‘Subtle balance of sustainable orderliness‘ on June 22nd, 2016).  The temperature in a refrigerator is sufficiently low that it slows down the processes of decay in the food stored in it (see’ Life-time battle‘ on January 30th, 2013) which effectively slows down time locally in the fridge.  However, there is a price to pay because the process of creating of the cold zone in the fridge increases the entropy in the universe and moves the universe infinitesimally closer to cosmic heat death (see ‘Will it all be over soon?‘ on November 2nd, 2016).  So, cooling the food in your fridge slows down time locally but brings the end of the universe a tiny bit closer.  Perhaps that’s not worth worrying about until you start thinking about how many fridges there are in the world (about half a billion are sold every year) and how many other devices are generating entropy.  The end of the universe might still be billions of years away but all that anthropogenic entropy is contributing to the increase in the temperature of the Earth’s ecosystem.

When you invent the ship, you also invent the shipwreck

I recently came across this quote from Paul Virilio, a French philosopher who lived from 1932 to 2018.  Actually, it is only the first part of a statement he made during an interview with Philippe Petit in 1996.  ‘When you invent the ship, you also invent the shipwreck; when you invent the plane you also invent the plane crash; and when you invent electricity, you invent electrocution. Every technology carries its own negativity, which is invented at the same time as technical progress.’  These events have a catastrophic level of negativity; however, there is a more insidious form of negativity induced by every new technology. It arises as a consequence of the second law of thermodynamics which demands that the entropy of the universe increases in all real processes.  In other words, that the degree of disorder in the universe is increased every time we use technology to do something useful, in fact whenever anything happens the second law ensures some negativity.  This implies that the capacity to do something useful, often measured in terms of energy, is decreased not just by doing the useful thing but also by creating disorder.  Technology helps us to do more useful things more quickly; but the downside is that faster processes tend to create more entropy and disorder.  Most of this negativity is not as obvious as a shipwreck or plane crash but instead often takes the form of pollution that eventually and inexorably disrupts the world making it a less hospitable home for us and the rest of nature.  The forthcoming COP26 conference is generating much talk about the need for climate action but very little about the reality that we cannot avoid the demands of the second law and hence need to rethink how, when and what technology we use.

Sources:

Elaine Moore, When Big Dating leaves you standing, FT Weekend, July 8th, 2021.

Paul Virilio, and Petit Philippe. Politics of the Very Worst, New York: Semiotext(e), 1999, p. 89 (available from https://mitpress.mit.edu/books/politics-very-worst).

Are these the laws of engineering?

While shopping on-line for books during a pandemic lockdown allows you to buy new books, I found it difficult browse online and find new authors. Perhaps because the algorithms employed by the booksellers are too busy guessing my interests or promoting the latest book that they want me to buy. So it was a pleasure to be able to walk into a bookshop again in a couple of months ago. One of the new authors that I discovered was Niall Williams. I have just finished reading his 2019 novel ‘This is happiness‘ which weaves together the life of an Irish village in which nothing ever changes until the coming of electricity, a tale of coming of age and another of burying the past. In the middle of this beautifully-told story, a salesman is extolling the virtues of the electrical gadgets that they can install in their new electrified homes and says that ‘the first law of engineering was to make the world a better place’. The narrator quietly tells us the second law, which the salesman doesn’t state, ‘that without exception everything that was engineered would one day break down … usually one day after each machine had become indispensable to living’. This is a consequence of the second law of thermodynamics, which is that entropy, or disorder, increases in all real processes. Hence, the localised order, which we create when something is engineered, is constantly being eroded until eventually the disorder leads to a break down. Or, as Murphy’s law states ‘Anything that can go wrong will go wrong’. However, the definition of the first law of engineering was the one that caught my eye and resonated with a corny introduction that I used in a talk on why we need to change the way we teach engineering. I played a recording of Louis Armstrong singing ‘What a wonderful world‘ and then talked about the wonderful world that engineers have created before highlighting the unsustainable environmental costs of our ‘wonderful’ engineered world and that it is inaccessible to a large portion of the world’s population. I gave that talk many times to groups of engineering professors in the USA between about 2006 and 2012; maybe I had some impact but there is still a lot of changes needed to achieve a sustainable society. So, the first law of engineering should be to make the world a better place for everyone.

Reference:

Niall Williams, This is happiness, London: Bloomsbury Publishing, 2019