The Human Side of Science: Edison and Tesla, Watson and Crick, and Other Personal Stories behind Science's Big Ideas (2016)
Chapter 1: Democritus and Aristotle Ponder the Existence of Atoms
It is as easy to count atomies as to resolve the propositions of a lover.
—William Shakespeare, As You Like It, act 3, scene 2 (1599)
The idea that matter consists of atoms is pervasive in modern culture, even though no one has ever seen them directly. One of the best and most interesting pictures we've got was produced in 1989. It was obtained by a scanning tunneling microscope at the IBM Almaden Research Center in San Jose, California. A beam of xenon atoms was shot at a chilled nickel crystal, and the atoms that stuck to the crystal were manipulated by the microscope's probe into the pattern shown below:
“IBM” spelled out in 35 atoms. Courtesy of IBM.
SLICING AND DICING MATTER
The reality of atoms answers a fundamental question that is simple enough to frame: If any material object is cut into smaller and smaller pieces, would there be some limit, after which no further cuts could be made, or would the material be infinitely cuttable?
Ancient Greeks. Used with permission from Sidney Harris.
To get to the heart of this question, we need to go back, back, way back. How far? As many wags have suggested, “The ancient Greeks thought of everything first.” Atoms are a case in point.
Leucippus (fifth century BCE). From Wikimedia Commons, user Jean-Jacques MILAN.
Democritus (460 BCE–370 BCE). By Antoine Coypel (1661–1722). From Wikimedia Commons, user Fæ.
DEMOCRITUS: MATTER IS DISCONTINUOUS
Democritus (460 BCE—370 BCE) was born in the far north of Greece, in Abdera. He was taught by Leucippus, and many of his and Leucippus's ideas are so interwoven they are difficult to separate. As a young man, Democritus traveled extensively, spending a great deal of his inheritance from a wealthy father. He visited Asia, Ethiopia, India, and spent a long time in Egypt. Democritus's writings have not survived intact, so only secondary sources exist to help convey his ideas.
I am the most travelled of all my contemporaries; I have extended my field of enquiry wider than anyone else; I have seen more countries and climes and have heard more speeches of learned men.1
Although he was virtually unknown in Athens (he went there once to visit Anaxagoras and was ignored), his students and neighbors in Abdera regarded him highly because he was invariably cheerful and ready to see the humorous side of life. He was referred to as the “Laughing Philosopher.” He and Leucippus were materialists in that they looked for mechanistic explanations of phenomena, rather than deeper causes. They thought perception through the senses was so subjective that it was unreliable, so they discounted observations as relevant evidence.
Democritus (and, by extension, Leucippus) answered the fundamental question about divisibility of matter by postulating the existence of an uncuttable unit called an atom (Greek a = “not,” tomos = “to cut”) as the fundamental unit of matter.
The first principles of the universe are atoms and empty space; everything else is merely thought to exist.2
Aristotle (384 BCE–322 BCE). By Raphael (1483–1520). From Wikimedia Commons, user Dencey~commonswiki.
ARISTOTLE: MATTER IS CONTINUOUS
Aristotle (384–322 BCE) was born in the small city of Stagira in northeastern Greece, and he studied at Plato's Academy in Athens, where he started at about age seventeen. Plato (427–347 BCE), in turn, was a student of Socrates (469–399 BCE). After Plato's death, Aristotle left Athens for about twelve years. During that time, he tutored young people who went on to become kings, including Alexander (the Great). Upon his return to Athens in about 335 BCE, Aristotle established a school called the Lyceum.
Athens was the cultural hub of Greece and featured a tradition of discussion of all issues great and small. Aristotle and his students walked as they talked, earning them the title the “Peripatetic Philosophers.” Although Aristotle agreed with Plato about many things, he and Plato also had significant differences of opinion. For example, Plato's reasoning was deductive in that it proceeded from general principles to specific instances. For example, all chairs have four legs, therefore this chair has four legs. On the other hand, Aristotle's reasoning was inductive in that it broadened from the specific to the general. For example, I have seen five tables, all of which have four legs. Therefore, all tables have four legs. Aristotle's emphasis on specifics led him to make systematic observations about living things, especially marine life, which set biology on a sound footing that lasted for centuries.
Aristotle invented and systematized logic as a tool for scientific inquiry. The overall scientific process used by Aristotle was one of careful observation, followed by logical reasoning about causes. Despite his extraordinarily wide-ranging scholarship that laid the groundwork for many intellectual pursuits during his own time and long thereafter, even a man as perceptive as Aristotle surprisingly made a few errors. His analyses of motion in general and planetary motion in particular were both flawed, leading to later difficulties, as we'll see in subsequent chapters. One particular error seems quite blatant, namely:
Males have more teeth than females in the case of men, sheep, goats, and swine.3
With his emphasis on careful observation, many have wondered why Aristotle didn't simply count the teeth of both sexes and make a proper comparison.
More than two hundred treatises are credited to Aristotle. The thirty-one surviving works are suspected to be rough lecture notes, perhaps even taken by students and not intended for publication. Most of these were lost for a while but were later translated into Arabic and analyzed extensively by Muslim scholars. Some think Aristotle was the last person who knew everything that could be known at the time he lived.
Aristotle's brain. Used with permission from Sidney Harris.
When analyzing the question about matter's fundamental constituents, Aristotle comes down squarely against there being any smallest unit:
Neither is there a smallest part of what is small, but there is always a smaller (for it is impossible that what is should cease to be). Likewise there is always something larger than what is large.4
Aristotle thought matter was made from the four elements suggested by one of his predecessors, named Empedocles, who identified them as fire, air, earth, and water. Aristotle added one more element, æther, the material of heavenly bodies.
Aristotle's Elements. This file comes from Wellcome Images, a website operated by Wellcome Trust, a global charitable foundation based in the United Kingdom. From Wikimedia Commons, user Fæ.
DEMOCRITUS VERSUS ARISTOTLE
There is no record of Democritus and Aristotle ever having met, however, Aristotle knew of Democritus and his ideas and argued forcefully against them. One of his treatises was titled “On Democritus,” but, unfortunately, only commentary survives.
Here is an example of Aristotle's argument against the atomic theory of Democritus:
He (Democritus) ascribes the genesis and the separation opposed to it not only to animals but also to plants and to worlds, and comprehensively to all sensible bodies. If, then, genesis is combination of atoms, and destruction separation of them, then even according to Democritus “genesis” must be change of quality. Indeed, Empedocles, too, says that that which comes into being is not the same, except in kind, with that which has perished, and yet Alexander says that Empedocles assumes the existence of change of quality, not of coming into being. Are we then to say that the All is composed of indivisible substances? Some thinkers did, in point of fact, give way to both arguments. To the argument that all things are one if being means one thing, they conceded that not-being is; to that from bisection, they yielded by positing atomic magnitudes. But obviously it is not true that if being means one thing, and cannot at the same time mean the contradictory of this, there will be nothing which is not, for even if what is not cannot be without qualification, there is no reason why it should not be a particular not-being. To say that all things will be one, if there is nothing besides Being itself, is absurd. For who understands “being itself” to be anything but a particular substance? But if this is so, there is nothing to prevent there being many beings, as has been said. It is, then, clearly impossible for Being to be one in this sense.5
Although this may seem befuddling to us, perhaps it made more sense in Aristotle's day.
Aristotle's teacher, Plato, was said to be even more extreme in his opposition to Democritus. Although Plato's writings never mentioned Democritus by name, Aristotle's pupil, Aristoxenus, wrote that Plato wanted to burn Democritus's books, but they were too widely distributed for his idea to succeed. Ironically, the major reason we know about Democritus's ideas is because of their mention in Aristotle's students’ writings. Since Aristotle taught in Athens and had many students and followers, his ideas would have won any popularity contest with those of Democritus.
Bonus Material: Aristotle/Democritus Internet interview. See To Dig Deeper for details.
AND THE WINNER IS…
Actually, neither Democritus nor Aristotle was completely correct.
In the modern view, matter is made of small units, usually molecules. Molecules are, in turn, made from atoms, but these atoms are not indivisible, as Democritus thought. Atoms have an outer cloud of negatively charged electrons moving around a positively charged nucleus. The nucleus contains positively charged protons and neutral neutrons. Neither of these, however, are fundamental particles. They are in turn made of even smaller particles called quarks. And quarks are made of…well, we don't know yet. Further, unlike the situation in ancient Greece, today's scientific ideas require the support of experimental evidence, which can get quite involved, to say nothing of the expense of conducting experiments to obtain such evidence.
Ideas were paramount in the Greek times, but there was no system of checks and balances in science the way it operates in the modern world. The next chapter takes us on a sometimes painful journey toward the modern system.
Philosopher-scientists. Used with permission from Sidney Harris.