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

By Felice Frankel

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.

The mathematical description of these reactions is analogous to those used to describe predator — prey relations involving wolves and lemmings. First, the lemmings eat grass, and their number grows. The wolves find the abundant lemmings to be a fine supply of food. The population of wolves grows and that of lemmings declines, until there are no longer enough lemmings to support the wolves. The population of wolves then declines, that of lemmings again increases, and the cycle repeats itself.

These stable oscillation patterns catch the eye and demonstrate how chemical energy can be converted to unexpectedly regular patterns, and how oscillations in time can be converted to oscillations in space. They hint at structure in life — the most spectacular processes that burn chemical energy and generate complexity. Some of the reactions occurring in simple organisms seem to oscillate, and more complex regularities exist throughout nature: the pacemaker of the heart, the trains of spikes nerve cells used to talk to the brain, the aggregation of slime molds, the patterns in the fur of animals, and the extraordinary geometrical organization that characterized the early stages in the development of the embryo.

Most of what we study in science takes place over time. It’s all about seeing change, so it makes sense to capture that change in moving images. (If we can! Many times it’s impossible.) After all, that is what animation or film is — a series of still images. But we might be missing some important observations if we only look at “moving” pictures. If we study one frame next to another, as we may here in this grid, we might get to see “more” in a way. We can compare one moment to the next and truly see more of what’s going on. See for yourself. Are you seeing the same information in both of these visual expressions of the B-Z Reaction?