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Boltzmann’s Atom by David Lindley

It might be hard to imagine now, but at the end of the 1800s, the scientific community was beginning to think it had more or less wrapped up all-things physics. Newton’s mechanics were well understood and Maxwell had recently shown how light behaved as a wave, giving a unified theory of electricity and magnetism. Little could they all imagine that everything would be turned on its head in just a few short years.

Presaging this transformation of physics was Ludwig Boltzmann, who was one of the leading figures of what we now call statistical mechanics. He showed how we could move beyond treating individual particles and think about them as large groups, think about their average properties. This allowed him to consider the properties of solids and liquids and gases on a scale that more directly connects with every day life. Maybe most importantly, he showed how the properties of these groups, or ensembles, of particles connected to the concept of entropy, which was a fairly vague concept before him. His impact to physics is immeasurable, and is enshrined in various concepts that bear his name, not least amongst them being the Maxwell-Boltzmann distribution and the Boltzmann factor.

However, during his life, his ideas were not so quick to catch on and were, in particular, challenged by people like Ernst Mach (yes, the one who devised the Mach scale of speed), who exposed a view that physics should only describe what is directly observed, that there was no room for theorizing what caused those observations. That, combined with Boltzmann’s relative isolation in a small university and his own near-schizophrenia with his status, led to a relatively slow acceptance of his ideas. Boltzmann’s ideas had, at their core, the concept of atoms, a concept that was not at all widely accepted during his time. As late as 1897, leading scientists such as Mach could exclaim “I don’t believe that atoms exist!”

Of course, there were theories of atoms before Boltzmann, dating back to the ancient Greeks. Lindley traces the development of our theories of atomic particles and Boltzmann’s contributions to those theories. Boltzmann’s own theoretical advances made predictions, based on the assumption of atoms, that were later validated and helped conclusively show that atoms do indeed exist (Einstein also played a critical role with his theory of Brownian motion). That Boltzmann’s assumptions were fundamentally correct was not a given, and that they led to predictions that agreed with observation did not prove them to be true. As Lindley notes: “You make an assumption and explore the consequences. This is exactly what scientists continue to do today, and the fact that a certain assumption leads to all kinds of highly successful predictions and explanations does not, strictly speaking, prove that the original assumption is correct.

Lindley’s portrait of Boltzmann is both the story of a man who had some very profound personal issues and the history of a branch of science that presaged the quantum revolution. The story of the advancement of science is fascinating in its own right, as generations of scientists tried to tease out what, at the microscopic scale, was driving the macroscopic observations we make every day. Lindley describes the scientific environment of the time, in which a few big heavyweights dominated the discourse. A single scientist, working in relative isolation, like Boltzmann, could make huge impacts on his field. This isn’t as true today, where we seem to be delving more into details than bigger swaths of truth. Not that there aren’t any new big truths to discover, but rather that the kinds of technological advances that are rewarded demand digging into the details. And, the democratization of science — the shifting of science being a rich-man’s hobby to a true profession pursued by large armies of people — have made it so that it is harder to stand out in the proverbial field.

As for himself, Boltzmann was never happy. He always desired more recognition for his achievements and that typically meant moving to bigger and better positions at other universities. However, the moment he accepted such a position, he was riddled with doubts and often tried to undo the appointment. Particularly in Austria, where appointments were at least brought to the attention of the royals, this led to some level of infamy for the poor man. His vacillations were likely a reflection of some deeper level of depression or other mental condition, as he ultimately took his own life.

Finally, Lindley also provides some metacommentary on the scientific process itself. This is both through the continual argument between people like Mach and Boltzmann (Mach particularly disliked theorizing, stating, for example, that “the object of natural science is the connection of phenomena, but theories are like dry leaves which fall away when they have ceased to be the lungs of the tree of science“) as well as his own observations: “Science demands an element of creativity, and an element of faith. The creativity comes in thinking up hypotheses and theories that no one has ever thought of before. The faith comes in thinking that these hypotheses, when shown to be useful or successful in some way, bear a relation to what is loosely called reality.” Late in his life, Boltzmann, spurred on by the attacks by Mach and his followers, turned toward philosophy, in an attempt to understand the nature of truth. However, he never really became a philosopher, telling a colleague “Shouldn’t the irresistible urge to philosophize be compared to the vomiting caused by migraines, in that something is trying to struggle out even though there’s nothing inside?

Altogether, Boltzmann’s Atom is an excellent portrait of a man and of an era in science. It is a lesson in how science advances, not necessarily through the unstoppable march of progress, but in fits and spurts as different personalities come and go. Boltzmann himself is an intriguing figure that bridges two different eras of science. We tend to forget both that science doesn’t always follow an obvious linear path in the search for understanding and that the people that push it forward are human with very human foibles. Boltzmann’s Atom reminds us of both.

Boltzmann’s Atom by David Lindley

1009394Ludwig Boltzmann was one of the fathers of statistical mechanics, that field of physics that treats large collections of particles and has allowed us to understand how materials, which are large collections of atoms, behave. That atoms comprise everything around us is almost self-evident today, but only about 100 years ago, many scientists did not believe atoms existed. Scientists like Boltzmann postulated atoms to derive theories that could explain, for example, how gases behave when you squeeze them or heat them up, but, at the time, they were a theoretical construct. Sure, earlier scientists and philosophers had speculated on the existence of atoms, all the way back to the ancient Greeks, but no one had ever seen an atom, so building a whole theory on the assumption that atoms exist seemed, to many scientists, the utmost folly. They thought it was pointless to build theories on hypothetical entities that might never be observed.

In spite of pushback from many established scientists, Boltzmann dedicated his life to developing theories that relied upon the assumption that atoms exist. He was only fully vindicated when Albert Einstein published his paper explaining the origin of Brownian motion, that motion you can see in a microscope in which a particle of pollen, for example, seems to wander randomly around the slide. What caused that motion? Einstein showed it was atoms bombarding the pollen grain from all sides. He did this by using Boltzmann’s theories.

David Lindley’s Boltzmann’s Atom explores the state of physics during the end of the 1800s and how scientists like Boltzmann laid the foundation for modern theories about atoms. Not only did Boltzmann’s work establish some of the pillars of statistical mechanics, but, in some sense, laid the groundwork for the forth-coming quantum revolution. Lindley describes the scientific atmosphere, especially the conflict between pure theorists like Boltzmann and more pragmatic scientists that felt that theoretical physics was not fundamentally science. Ultimately, Boltzmann’s ideas prevailed, but that basic conflict still exists, particularly as modern scientists build theories based on super-strings and membranes, entities that no one knows how we will ever see. The debates we have today about the future of science and whether such theories are really science remind one of the similar debate over atoms.

Not only does Lindley provide a fascinating history of science, but he delves into the life of Boltzmann himself, who was a complicated man. Boltzmann seemed to never be at peace, never happy with the perceived lack of recognition his theories had during his life. He always felt isolated and alone, never in the center of the science world. He always felt like he was missing out, much like the social wallflower that hangs back against the wall at the party. Lindley’s portrayal of Boltzmann and the other scientists of the era shows that scientists are all too human, with their ambitions, egos, and insecurities. That the pillars of such an important branch of physics were such people provides a reality check on how science actually occurs. Breakthroughs aren’t automatically embraced by the community, but often need time to be assimilated, often via the passing of the old guard, before they are truly appreciated. Science, like all human endeavors, can be messy, and the life of Boltzmann highlights this fact.

Having read this accounting of Boltzmann’s life right after that of Alexander Hamilton’s, I am struck by the anxieties we have today. We fret that politics has degenerated or that science is at the cusp of some existential crisis. We always believe that our situation is somehow special, that things are at a tipping point never encountered before. However, reading about these men and their roles in the history of science and the United States, respectively, one cannot but be struck by how little things have changed. Sure, politics are nasty now, but they were nasty way back during the founding. Sure, theoretical physics has an uncertain future, but it did so back when atoms were being discussed. Things are different, but they really aren’t at some level. As they say, those who don’t know their history are doomed to repeat it.