One of the traditional ways to explain a scientific subject is the historical approach: start at the beginning of the endeavor and explain why people asked the questions they did, how they answered them, and how each answer blossomed into new potential. It’s a popular way of teaching science, too, because it emphasizes the process that leads to new discovery. Middle World: The Restless Heart of Matter and Life(amzn/b&n/abe/pwll), by Mark Haw, exemplifies the technique. Not only is it effective, but this one slim book manages to begin with a simple, curious observation in 1827 and ends up synthesizing many of the major ideas of modern physics, chemistry, and biology!
That beginning is with Robert Brown, a botanist scrutinizing pollen grains dancing in a drop of water. He was hoping to discover how fertilization occurs in plants, but instead noted a physical phenomenon that would be posthumously named after him, Brownian motion. We learn that he set off on his voyage of discovery with a literal ocean voyage during the Napoleonic wars; that his ship fought off pirates shortly after setting sail; that he circumnavigated the Australian continent in a shabby, disintegrating ship, on a trip in which many of the crew died of malnutrition; and that he did all that to pull weeds, i.e. “botanize” for the Crown. That was an era of heroic science, and I have to confess that I did feel like a bit of a poseur after reading all that.
Brownian motion, though, was a mystery — one that was unexplained in Brown’s lifetime — and to many seemed to violate Newton’s laws. It wasn’t rule-like behavior — it was random and complex and didn’t fit into the conception of a clockwork universe that glided along on smooth trackways of causality and predictability. How to reconcile Newton with chance?
And then the book just takes off. We get Carnot, Thomson, and Clausius and an introduction to thermodynamics; Maxwell and Boltzmann and atoms and molecules; then the Miracle Year and Einstein’s hat trick, which included a theory of Brownian motion; Langevin and Perrin, the man who proved atoms. The entire revolution in physics is presented from the perspective of trying to explain a botanist’s observation of a few pollen grains. It works, too — it’s a beautiful summary of how science works, proceeding from question through trial and error testing to theory and refinement. The reconciliation with Newton requires an understanding of the Middle World, this broad domain between the atomic and the macroscopic, where behavior is in flux and the rules have to be explained in statistical terms — where cause has probabilistic, not hard and fast deterministic, effects.
In the 20th century, Haw tells us about the really cool stuff: modern chemistry and biochemistry, and how the behavior of the objects in the Middle World is central to understanding those processes. For example, he talks specifically about observations of kinesin, an important transport molecule in cells that you can see portrayed in this animation of activity in a cell as a two-legged stalk attached to a gigantic vesicle, making a stately march along a microtubule. Only in reality, a molecule’s progress is anything but steady and stately—it’s a wiggly jitterbug, buffeted by the soup of surrounding molecules, and it sometimes takes a step back, or two steps forward, or lurches and halts. Our “molecular machines” are not at all like the familiar ones in the macroworld, they are ruled by chaos and chance and all biochemistry does is skew the odds to get an average response in a particular direction, a tricky balancing act between randomness and order.
The final chapters explain that the study of the Middle World is not done. The next steps include new challenges, like nanotechnology and life itself.
It’s a phenomenal book. It’s slender and makes for an easy read, yet still it explains fundamental concepts well, in terms of the experiments that led to their discovery. There’s a reason we make biology students take physics and chemistry, and it’s because their essential ideas are all tightly interlinked — and this book makes a good case that viewing molecules as inhabitants of that Middle World is a powerfully unifying perspective.