Time for another post about the history of atom theory from award-winning physics professor (and my dad) Dean Zollman. Today, we meet one of the giants of science history, Isaac Newton. Not only did his work introduce new theories and discoveries; he also set the stage for the future. – Kim
By Dean Zollman
At the Royal Society’s celebration of the 300th anniversary of Isaac Newton’s birth, Niels Bohr said, “Truly, it may be stated that Newton’s genius did not only bring order to all knowledge attainable at his time, but even led him to an amazing degree to anticipate later discoveries and developments.” This statement can be supported in a variety of topics including the models of the composition of matter.
Isaac Newton (1642-1727) is considered by many, if not most, historians of science as the most important physicist and mathematician of all time. His work in the calculus, optics, motion, and gravitation set the stage for much of the science that has occurred since then. Almost all of his theories and discoveries represented huge departures from previous scientific thought.
Newton did not write extensive scientific documents about atoms or the structure of matter. Instead, thoughts about these topics are scattered in his other publications. He leaves no doubt that he believes that matter consists of particles which are in motion through a vacuum, which he called pores. He also concludes that the pores can be the largest part of the volume of a substance. For example, based on the transparency of water he writes in Opticks (first edition, 1704), “Water has above forty times more pores than parts.”
By the second edition of Opticks, he had established a hierarchical structure for matter. Particles had empty spaces between them. But each of the particles were in turn made of smaller particles and these smaller objects had empty spaces between them “till you come to solid Particles, such as have no Pores or Empty Spaces within them.”
A great contribution to our understanding of matter was Newton’s model of how matter was held together. From the Greeks through contemporaries of Newton, atoms needed to be in contact to stick together. Different types of atoms had different mechanisms such as hooks and loops to cause cohesion. (Makes you wonder why they did not invent Velcro.) From his study of gravity, Newton understood that forces could act at a distance. He applied this idea to the smallest particle of matter.
In his 31st Query in Opticks (second edition), Newton discusses this force and shows some of the reason that Niels Bohr said that Newton anticipated many things to come. For example, when speculating about the nature of the force, he describes, “[the attractions] which reach to so small distances as hitherto escape Observation; and perhaps electrical Attraction may reach to such small distances, when without being excited by Friction.” (In Newton’s time, electrical charges were separated and electrical phenomena studied by rubbing, much the way you get an electrical shock by shuffling across a carpet and touching a piece of metal. Thus, Newton was anticipating that electrical forces in nature could be created in other ways.)
Another look forward, also in the 31st Query, combined his hierarchical model with the attraction between particles:
“The smallest Particles of Matter may cohere by the strongest Attractions and compose bigger particles of weaker Virtue; and many of these may cohere and compose bigger Particles, whose Virtues is still weaker and so on for divers Successions, until the Progression end in the biggest Particles on which the Operations in Chymistry, and the Colours of natural Bodies depend, and which by cohering compose Bodies of a sensible Magnitude.”
Today, when thinking about the structure of matter, we consider quarks, protons, neutrons and electrons, atoms and molecules. Interactions such as the strong force and the electromagnetic force with vastly different strengths and ranges are involved in holding the various forms of matter together. Thus, Newton was on the right track about 300 years ahead of the rest of us.
As we have discussed in previous posts, religion played an important factor in discussions about atoms and the structure of matter. Newton weighed in on this aspect as well. In the Principia Mathematica, Newton discussed the ideas concerning God that had been attributed to the ancient Greeks such as Democritus and Epicurus: “They are thus compelled to fall back into all the impieties of the most despicable sects, of those who are stupid enough to believe that everything happens by chance, and not through a supremely intelligent Providence; of these men who imagine that matter has always necessarily exited everywhere, that it is infinite and eternal.” Rather strong words for those who did not see a role for God in the creation and development of the universe.
Light and optics were major subjects of Newton’s investigations. He learned that white light was composed of the colors, investigated the properties of lenses and prisms, and built the first telescope that used mirrors. To explain these observations, he developed a theory of light, which was built on light being small particles. That theory explained his observations but did not stand up after interference of light was discovered. In the early 19th century, a wave model of light was proposed and evidentially became the dominant model. (Things became more complex in the 20th century with the discovery of quantum effects. More on that later.) However, overall Newton’s ideas about the nature of matter provided important steps forward in humankind’s understanding.
In addition to his significant contributions to physics and mathematics, Newton conducted experiments in alchemy during most of his life. He did not publish about his alchemy but wrote extensively about his experiments in private documents.
Many of these writings remained in a collection that was not looked at by historians until the 20th century. These rather recent studies have revealed some of the influence of alchemy on Newton’s thoughts about the structure of matter. Next time, we will look at this aspect as well as the more general impact of alchemy and alchemists on theories for atoms.
Images via Wikimedia Commons, public domain unless otherwise noted
Dean Zollman is university distinguished professor of physics at Kansas State University where he has been a faculty member for more than 40 years. During his career he has received four major awards — the American Association of Physics Teachers’ Oersted Medal (2014), the National Science Foundation Director’s Award for Distinguished Teacher Scholars (2004), the Carnegie Foundation for the Advancement of Teaching Doctoral University Professor of the Year (1996), and AAPT’s Robert A. Millikan Medal (1995). His present research concentrates on the teaching and learning of physics and on science teacher preparation.