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The B-Z Reaction: The Moving or the Still Image?

In this first installment of Inside the Image, I decided to describe one of my own pictures and raise what I believe is an interesting question at the very end of the article. But first, an explanation of what is the above series of pictures that I made several years ago on film.

I first captured each image over time, about 11 seconds apart with my Nikon F3, using a 105 macro lens. I then scanned the images on my Imacon scanner and then edited the number of images down to 12 to create this grid in Photoshop on my Mac. You’re seeing a reaction of chemicals taking place over time, called the Belousav-Zhabotinsky (B-Z) reaction, named after the discoverers. My co-author George Whitesides describes it best in our book, “On the Surface of Things, Images of the Extraordinary in Science”:

Waves of chemical reaction ripple outward on the surface of a chemical pond. To a stationary observer staring at a point on the surface, the colors — mirroring the concentration of reactants and products — oscillate. These patterns are startling in their regularity and complexity.
A solution of the reactants was poured into a dish. The reaction began when a pin was quickly inserted into the solution. The first product formed in an autocatalytic reaction: the first small amounts of this product that formed accelerated the formation of more of it. The first reaction swept outward, generating high concentrations of the initial product as it moved. A second reaction then occurred that involved the product of the first as a reactant. This second reaction followed the first, destroying the initial product and forming a second. The combination of these two processes — a wave of the first reaction forming an initial product, and subsequent wave of the second destroying — caused successive waves of reaction to ripple outward. An indicator molecule — an observer of these processes — signaled the passage of successive waves of reactions, turning from orange to white as the first reaction took place, and from white back to orange for the second.