Video found here: https://www.nikonsmallworld.com/galleries/2020-small-world-in-motion-competition/internal-flow-dynamics-of-coalescing-micro-droplets

Image Credit: Kazi Fazle Rabbi and Dr. Xiao Yan

Reason for selecting this video: Droplet coalescence is incredibly hard to capture due to the scale of droplets. The physics of coalescence occurs at a minute scale that necessitates high-resolution imaging and magnification to capture. This photographer was able to capture multiple droplets of various sizes and visualize their interaction due to their proximity. Further, the photographer managed to record the internal dynamics of the smaller droplet after the larger droplet envelopes it (that’s the mushroom cloud in the middle of the larger drop).

From an artistic perspective, the photographer made a few choices that augment the physics and depict the beauty of droplet coalescence. I appreciated that the editor chose to show the droplet coalescence both chronologically and in reverse. This “bounce-back” effect illustrates how quickly the droplets converge and the beauty of both the coalescence and separation (even if this separation effect is not exactly real). The illuminated background juxtaposed with the darker (likely ink-stained) boundaries of the droplets, allows the audience to see the clear boundaries of the droplet, the scale of the coalescence, and the ejection of the smaller droplets as a result of the larger droplet ingesting the smaller droplet. I find beauty in the physics depicted in this image but, disregarding that, I find the “still-life” effect of the droplets alone rather alluring. This video illustrates the interaction of the smallest of objects and the profundity of their scale in dictating their interaction.