Think Bubbly thoughts (Part II)

Having sent off an abstract for an upcoming conference, two papers and finishing another off this week, I’m finally getting on with the job (in a typically glacial academia style). Some reflections are thenceforth warranted before I embark on writing the “big paper” as it’s affectionately known in my head; a step I’ve been looking forward to ever since the “mini-Eureka” moment in my kitchen circa November 2015. To the uninitiated, this amounts to (incidentally the start of my recent invited paper at the Physical Review Fluids journal):

The intensely colourful flow patterns on the surface of a soap bubble can mesmerise and provoke fascination among young children and the scientific community alike.

I was instantly provoked (of course).

Writing this post at the start of my typical work day (which is normally 13:30) is unusual when I should be running simulations, but it is not entirely out of character as some thoughts have entered unconsciously during the previous sleep that I may need to untangle before I can type another line of Python.

The problem or rather the situation is actually better expressed in sociology. As ever, I have the long-held belief that a bubble uncannily mimics aspects of life, and it is the job of the scientist to translate between these two completely separate realms.

In the “big paper”, I aim to describe the fluid dynamics moments before a bubble rupture. This is a decidedly non-trivial task which combines the best part of physical chemistry, fluid dynamics and quantum physics at around the 100 nanometre length-scale, talk about daunting.


You may have seen the picture above, an early relic of my PhD after a cup too many tea.. What it illustrates are the patterns that appear naturally near the “black region” which forms the centre of our work.

The premise is quite simple: given a miniscule perturabation, large organised patterns/cracks will start to appear and eventually the bubble pops. It was surprising that the “kick” required to start the rupture is mindnumbingly tiny. I mean, 1000 times smaller than the thickness of the bubble film, which is already ~100 nanometer thin.

This ångström-ic kick brings us to the point of this post. This seemingly small perturbation leading to the incoming rapture is not unlike the butterfly effect in real life (yes, the bubble is almostly certainly chaotic – both in the strict mathematical definition and the literal).

Sweeping societal changes are triggered by small divisions, a convenient if over-done example would be the elections of a certain country (call it the Unified territories of Ruritania) – small low-level perturbations can reveal the underlying divisions in a society. Hence you can say that the patterns you see in the picture above are symptoms of the bubble itself and the “kick” merely raises it to the surface – the small black region can lead to the collapse of the entire bubble, even if the rest of the bubble do not conform to its behaviours (or indeed, are nothing alike).

So what to do?

Certainly in the case of the bubble, I can suggest a fundamental change in the fluid property, such that the ingrained rupture patterns would no longer be malignant. But if that’s not possible, then it would be in the bubble’s best interest (unless you enjoy the sadistic consequences of its demise) to smooth out any micro-perturbations which may occur.

As for the society, it is less clear. But it is telling that the bubble rupture is almost entirely controlled by the top/extreme 1-2% which are triggered by the tiniest perturbations to completion. It is a tad disturbing that a bubble of all things would be so vulnerable to fluid dynamical hijacking, but it does seem that those at the extreme (with the thinnest film) do sadly cause the most damage.

And on that bubbly thought, I may need to go do some real work :)


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