LITMIR.BIZ

      The identification of these elements was not a proof of a discrete model of matter. There was no reason that this picture of the ingredients of my dice couldn’t be a formula for the way a continuous structure combines. Although the chemists were tending towards an atomistic view of the universe, this was far from the case in the physics community. Those, like the German physicist Ludwig Boltzmann, who proposed atomic models of matter were laughed out of the lab.

      Boltzmann believed that this atomic theory was a powerful way to interpret the concept of heat based on the idea that a gas was made up of tiny molecules bashing around like a huge game of micro-billiards. Heat was just the combined kinetic energy of these tiny moving balls. Using this model, combined with ideas of probability and statistics, he was successfully able to explain the large-scale behaviour of a gas. But most physicists were still committed to a continuous view of matter and were very dismissive of Boltzmann’s ideas.

      Boltzmann was so ridiculed that he was forced to retreat from his belief that this billiard-ball theory of matter represented a true picture of reality, and instead was obliged to refer to it as a heuristic model if he wanted to get his ideas in print. As Ernst Mach, his great nemesis in the debate about the reality of atoms, declared mockingly: ‘Have you ever seen an atom?’

      Boltzmann was plagued by fits of depression, and there is evidence that he was in fact bipolar. The rejection of his ideas by the scientific community is believed to have contributed to the depression that struck in 1906 and that led to him hanging himself during a holiday with his family near Trieste while his daughter and wife were out swimming.

      It was a tragic end, not least because the most convincing evidence that he was right was just emerging. And it was one of the big names of physics who produced ideas that supported the atomistic view and were very hard to ignore. The work that Einstein and others did on Brownian motion would prove extremely difficult to explain for those who, like Mach, believed in a continuous view of the world.

       POLLEN PING-PONG

      Although conventional microscopes don’t allow one to see individual atoms, they did allow scientists in the nineteenth century to see the effect that these atoms were having on their surroundings. It’s called Brownian motion after Robert Brown, who in 1827 noticed the random behaviour of small particles of pollen floating on the surface of water. Since pollen was organic, Brown’s first thought was that it might be exhibiting signs of life as it jumped around the surface. A similar random behaviour of coal dust floating on alcohol had also been observed by Dutch scientist Jan Ingenhousz in 1785. When Brown saw the pollen’s behaviour replicated by inorganic matter, he was rather stumped as to what was causing the jittery motion.

      It’s striking that the idea that it might be invisible atoms bashing into the larger visible material had been suggested by the Roman poet Lucretius in his didactic poem On the Nature of Things:

      Observe what happens when sunbeams are admitted into a building and shed light on its shadowy places. You will see a multitude of tiny particles mingling in a multitude of ways … their dancing is an actual indication of underlying movements of matter that are hidden from our sight … It originates with the atoms which move of themselves. Then those small compound bodies that are least removed from the impetus of the atoms are set in motion by the impact of their invisible blows and in turn cannon against slightly larger bodies. So the movement mounts up from the atoms and gradually emerges to the level of our senses, so that those bodies are in motion that we see in sunbeams, moved by blows that remain invisible.

      This was written in 60 BC, but it would take Einstein’s mathematical analysis of the motion to confirm this atomic explanation of the random movement in Lucretius’ sunbeams and Brown’s pollen.

      The goal is to provide some model that will produce the strange motion exhibited by the small pieces of pollen on the surface of the water. If you divide the surface into a grid, there seems to be an equal probability that the pollen will move left–right–up–down. It is similar to the motion of a drunken man who randomly makes steps according to the toss of a four-sided dice. The picture below shows the paths of various particles of pollen as plotted by the French physicist Jean Baptiste Perrin, who took up the challenge of explaining the pollen’s motion in his book Les Atomes.