This process is irreversible, and the lost energy can’t be retrieved to carry out useful work. Inside a factory, the grating of pistons and the clanging of metal causes the continual dissipation of tiny amounts of energy. Real machines are different from the ideal versions in mathematical models. This work culminated in the modern formulation of thermodynamics, which relies on the concept of entropy, a term coined in the 1860s. The coolant will get warmer, but it will still be at a lower temperature than the kitchen outside, so it cannot spontaneously transfer that extra heat into the room: some work (typically electrical) must be performed to pump it out and keep the coolant sufficiently cold to do its job.Īs statistical methods were taken up by physicists during the 19th century, probability theory was used to analyse the relationship between the fluctuations of countless tiny molecules and the large-scale observable behaviour of a system. Similarly, food placed inside a refrigerator will get colder as its heat passes into the concealed coolant. As Sen puts it, ‘Heat never spontaneously flows from cold to hot.’ If I hold a hot stone in my cold hands, it will cool down. The word itself combines the Greek terms for heat and force, but its application now extends way beyond machinery to include biological processes, quantum mechanics and information processing.Īll fridges, including Einstein’s, are governed by the laws of thermodynamics, which rest on the distinction between heat and temperature. The study of thermodynamics began in the 17th century with attempts to create a vacuum inside a glass globe – the subject of Joseph Wright’s famous picture An Experiment on a Bird in the Air Pump (1768) – but it wasn’t established as a science until the Victorian era, when Scottish physicists drew on French research to improve the efficiency of the massive steam engines driving industrialisation. In Einstein’s Fridge, Paul Sen exhorts us to study thermodynamics so that we might make better-informed decisions about how to save the world.

This year, it has been kept at that setting as a ‘Covid wake-up call’, but the chief apocalyptic risks are still nuclear destruction and climate change.

In 1990, when the existence of global warming was routinely contested, a Nasa scientist spoke frankly on television: ‘It’s easier to get funding if you can show evidence of impending human disasters … Science benefits from scary scenarios.’ Last year, the Doomsday Clock was set to a hundred seconds before midnight, indicating that man-made global apocalypse is closer than at any point since the clock was created in 1947.

Science by Patricia Fara