Can understanding the science of bubbles help us understand how humans speak? Yes, say physicists

Accents and dialects were once solely the domain of linguists, but now British physicist James Burridge, of the University of Portsmouth’s School of Mathematics and Physics, has become interested in their evolution, variation and flux. He is a physicist who has spent most of his life applying physics to things seemingly unrelated to physics. His interests include naturally occurring rock formations and the dynamics of how games play out – he is interested in looking for ways to make predictions about things that are seemingly unpredictable. But he has a particular interest in language and dialects, and the use of physics to model them. His inspiration: bubble baths (pronounced “bāths” or “băths”– your choice).

Bubbles are governed by the laws of fluid dynamics, the branch of physics related to the behaviour of liquids and gases. In the 18th century, the Swiss mathematician and physicist Leonhard Euler believed that a set of laws could be developed to explain the behaviour of fluid based on Isaac Newton’s deterministic laws of motion. In other words, if we know the initial state of a fluid system and the laws that govern its behaviour, we should be able to predict its future entirely. Euler’s equations, however, were not able to take into account the fact that fluids in the real world have viscosity and exhibit friction.

Two individuals independently took up this challenge. In 1822, Claude-Louis Navier, a French engineer and physicist, made the first attempt. He observed how fluids flow through pipes and developed a set of equations that represented viscous stress. A few years later, George Gabriel Stokes, an Irish physicist and mathematician, published similar equations. Unlike Navier, he derived his equations from a microscopic perspective, considering the interactions between individual fluid particles. Navier’s and Stokes’s work did not gain prominence for many years. But later in the 19th century, experimental investigations into fluid mechanics confirmed the accuracy of their work. The Navier–Stokes equations now represent a set of complex rules that encapsulate the dynamic behaviour of fluids.

Like the laws of motion and thermodynamics that we’ve already looked at, they are predicated on the conservation of three things: mass, momentum and energy. Conservation of mass means that the mass of a fluid system remains constant over time. Conservation of momentum, which is defined as mass multiplied by velocity, means that the total momentum of a fluid system must remain constant over time, unless acted upon by an external force. And conservation of energy states that the total energy of a fluid system remains constant over time, unless acted upon by an external force.

The laws of fluid dynamics can be used to describe a wide variety of phenomena, including the flow of water in rivers and pipes, the flight of aeroplanes as air passes over the wings, the movement of air masses in the atmosphere…and the behaviour of soapy bubbles in a bubble bath.

All bubbles are formed by surface tension. One implication of the conservation laws described above is that they try to make their surface area as small as possible. The 3D shape with the lowest surface area is a sphere, so that’s why a solitary bubble on its own is spherical.

Bubble baths and dialects might sound like they have absolutely nothing in common, but Burridge found a link. He argues that the same physics that describes bubbles can offer new insights into the formation of language patterns. The boundaries of a bubble, Burridge believes, are analogous to isoglosses – lines drawn on a map to show the boundaries of the regions where different language components change. Just as bubbles seek to keep their surface area as small as possible, the shape and size of these linguistic boundaries adjust to the dynamics of social interactions, population movements and geographical features.

You can picture this by imagining a map of a country, but instead of cities and rivers, you see a cluster of bubbles. Each bubble represents a different dialect region. These bubbles aren’t perfectly round; they’re squashed and squeezed by their neighbours, forming irregular shapes and intricate patterns. The country is a container and these dialect bubbles are jostling for space, constantly pushing and reshaping their boundaries. Some are big and dominant while others are small and squeezed. The borders of the country act like the sides of a jar (albeit a jar with a very irregular shape), containing the bubbles and forcing them into the most efficient arrangement.

Burridge’s insight was to identify how surface tension, combined with other factors like variations in population density and the shape of the country, produces the patterns we see. He found that the same physics that describes bubbles can predict what dialects we hear, and where and when.

It can also predict how language will change. Factors like population movement and migration can cause small linguistic bubbles to merge into bigger ones, and Burridge believes that this model may allow us to predict the dialects of the future. Or, in many cases, the end of these dialects. The implications of Burridge’s work paint a stark picture. Over the next 50 years, it is predicted that many regional dialects will become increasingly alike to their neighbours, if not entirely obsolete.

In some ways, this is unsurprising and not especially alarming. We all know that language changes. The English of this book is very different to the English of Geoffrey Chaucer, 800 years ago – or even of Shakespeare, who wrote in the middle of that time gap. Loss of languages is not like the existential threat posed by risks like climate change or economic inequality. It was not one of the topics discussed at Davos. But it can represent the loss of something important.

Excerpted with permission from The Art of Physics: Eight Elegant Ideas to Make Sense of Almost Everything, Zahaan Bharmal, Bonnier Books.