I recently read an interesting vignette about Robert Brown, namesake of the phenomena known as Brownian Motion. Back in 1827, Brown noted the jittery motion of pollen grains on the surface of water, but struggled to explain his observations. We’ll get to his investigations in a moment, but what I hadn’t known until I read the vignette was that thirty years before Darwin made his famous journey on the Beagle, Brown made his own journey on the Investigator. Brown was a botanist and both collected and catalogued numerous new plant species in his trip to Australia. Brown is also famous for introducing the term nucleus – the particle in eukaryotic cells that stores genetic material.
Like any capable investigator, Brown tried all sorts of things. He used different particles instead of pollen. He tried different fluids. He systematically altered the ‘reaction’ conditions. As told by Tom McLeish in his book Faith & Wisdom in Science from which I read this vignette: “Beautifully designed tests of various possible causes of the motion ruled them out one by one.” Not fluid current. Not electrical effects. Not magnetic forces. Not external mechanical vibrations. Not the presence of light. “All the more tantalizing must have been his realization that the motion is universal – not depending on the particularities of particle or fluid.”
The mystery wasn’t solved in Brown’s time. McLeish has some words of wisdom: “Sometimes even the deepest questions simply arise before the time to answer them has come. One of the most impressive demonstrations of self-restraint within any scientific writing must be Brown’s masterly scientific detective work, its long list of dead ends and his explanation of why he was not proposing a theory for the effect… Brown wisely guessed that satisfying the temptation to suggest various untested causes might well have set others along false trails before they had allowed imagination sufficient free reign.”
Interestingly, one of the popular explanations at the time, not espoused by Brown, was that the jittery motion was indication of a ‘vital force’. Apparently, the great Michael Faraday devoted much time and energy to telling the public not to jump to such conclusions. Faraday had suspected that atomic theory had legs, but back then the idea of all matter being made of seemingly occultic invisible elementary particles was far from established.
The solution came in 1905 in one of Einstein’s famous annus mirabilis articles. I’ve had students read it in an introductory college science class. (I annotated it heavily to help the students.) Why was Einstein able to come up with the explanation? Because he was a certified genius? Or perhaps because ‘chance favors the prepared mind’? McLeish makes the following connections: “Einstein felt discomfort with the idea of one law to govern one aspect of the world, while a different law held elsewhere… of the atomic theory – that if these particles existed then they must be in constant yet random motion… that this motion would generate the manifestation of the property we call ‘heat’ in collections of very large numbers of atoms… Brown’s pollen granules were placed among a collection of molecules in seething thermal motion… would have to pick up the random packets of energy that were jumping from particle to particle.”
The rest is a few lines of algebra to complete the proof. (Which is why introductory college students can appreciate it.)
Brown noticed something that wasn’t part of his main research interest and pursued it relentlessly. He was a botanist. I suspect that pollen moving on the surface of water was uninteresting to most botanists of his time. Brown wasn’t just curious, he was also careful. Careful in his experiments. Careful in drawing conclusions. While I’ve certainly pursued side avenues as a scientist, none were seemingly as mundane as what Brown looked at. I’m also quick to discard something that seems ‘non-promising’. One doesn’t have the luxury of squandering time and resources in this age of competitive research. But perhaps that’s part of the problem – the scientific research enterprise is skewed towards productivity and efficiency. We’re also (too) quick to trumpet success in the business. Brown’s non-conclusive efforts would be considered failure in today’s cut-throat world of scientific reputations and dollars. Maybe that’s why I found it refreshing to read about Robert Brown, the investigator.
P.S. I highly recommend the Introduction in McLeish's book. His parable of sonology is superb.
P.P.S. I found it interesting that Terrence Deacon also invokes Brownian motion to discuss how macroscopic work comes from the microscopic world.
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