2,637 Years of Physics from Thales of Miletos to the Modern Era. Sheldon Cohen
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a condensed state it presents as mist, then as water, and finally as solid matter, the density of which depends upon the degree of condensation. Air, he felt, was one aspect of a series of changes from fire to air to wind to cloud to water to earth to stones. He attempted to confirm his thesis by simple experimental observation such as blowing on his hand with lips open widely and with pursed lips. In the first instance the air is warm. In the second instance the air is cold. This suggested that air is warm when rarified and cold when concentrated.
Anaximenes’ thesis that natural processes are responsible for the formation and change taking place in our world was an important development in the evolution of scientific thought. His contribution was to be the first to suggest a theory and try to prove it by thoughtful observation. At least this was a step in the right direction. Anaximenes had expanded this centuries old thesis. Others would soon enter the fray, such as….
Heraclitus of Ephesus (533-475 BCE)
added other elements to the century long discussion by insisting that fire was the source of everything. His main thought was to suggest that it also had life as manifested by its ever-changing ability. It evolved from fuel to fire to smoke to clouds to rain to oceans to earth. Heraclitus stood for the thesis that there was a unity of the world, but it depended upon and was consistent with constant change of opposites such as heat and cold, day and night, and life and death. This change suggested equilibrium, and his contribution was to suggest that such equilibrium indicated orderliness in our world.
Heraclitus was considered the most influential Greek philosopher before Socrates. What this deep thinking did to his mind is open to conjecture, however, for he was said to have retreated into the forest where he lived on plants, and tried to cure the dropsy (leg swelling) which he developed by covering himself with manure. It didn’t work.
The problem for the ancient Greek philosophers was the difficulty in attempting to develop a theory of a single entity evolving into the great variety of objects in the world.
To reconcile this conundrum,
Empodocles of Sicily (fifth century BCE)
suggested that rather than one basic element there were four: air, fire, earth, and water. These basic four elements, mixed and partially combined and separated, thus resulting in the various familiar forms of matter.
In the future, philosophers who adopted the primary building block theory suggested that the four basic elements of air, fire, earth, and water were each made of different atoms. This somewhat brought the atomos concept back into thought. Even with only four basic building blocks, the various combinations of these could result in a great variety of different forms of matter. If the proportions of the building blocks remained the same, there were twenty-four different combinations. Now consider the infinite number of combinations that would occur if you varied the amounts of each of the four basic elements.
For the first time, a combination of actual basic substances could unite to explain the great variety of forms and events which make up our experience.
In addition to the four basic elements of our earthly experience, there was a fifth: the aether that permeated the heavens as far as the eye could see. The aether, considered an invisible, elastic medium distributed through all space beyond the earth’s atmosphere remained a building block of physics for twenty-four centuries. More later.
Anaxagoras (500-428 BCE)
suggested that rather than the four basic elements of earth, air, fire, and water, there were infinite seeds composing all matter and not just the basic four. The proportion of the various seeds explained the great diversity of everything around us. From this concept of infinite seeds, or building blocks, it was a simple leap to the idea that there was a smallest, ultimate basic building block of all matter---the atom. It was postulated that in solid bodies, the atoms were held together by mysterious forces, while in gases, the atoms were separate and free to move in space. Over time, the atomists began to forge ahead as the theory of the four basic substances began to wane.
It was the Greek philosopher…
Leucippus (490-? BCE)
who strongly supported the concept of unbreakable tiny fragments, further promoting the atomos concept.
If traveling to Athens from a northwesterly direction, one will pass the Democritus Nuclear Research Laboratory. Naming this facility for…
Democritus (460-370 BCE)
honors a man whose atomos philosophy comes close to modern physics theory. Although he was not the first to espouse atomism, his use of this concept allowed him to develop a much more detailed, and what would prove to be a much more insightful view of the way the world functioned physically.
He believed that space was a vacuum, but in spite of this property of emptiness it could be thought of as existing as did the visual realities of our world. In the void of space, and in the world around us, there were an infinite number of atoms, so small that they were incapable of further division. These atoms made up the physical world. He postulated that all changes occurring in the universe were merely dependent on the density of the atoms and their movement in relation to each other. Nature itself was nothing more than a complex interaction of atoms that followed the laws of mathematics. Initially atoms moved incoherently, but over time they would randomly interact and combine in a multitude of ways responsible for the origin of the universe and the laws of mechanics and motion. As time would subsequently prove, this was a very advanced thought.
Thinking was expanding and getting closer to the mark.
He made many contributions to geometry and is credited with mathematical ideas that Isaac Newton would define many years later as the integral calculus.
It is little wonder that the Greeks thought to name a nuclear research facility after Demorcratus. He was greatly ahead of his time.
Plato (429-347 BCE) and
Aristotle (384-322 BCE)
accepted the atomos theory, and since they were so widely respected, their viewpoint held sway. Opposing views were not silenced, however.
Epicurus (341-270 BCE)
Espoused atomos with great vigor and is supposed to have written several hundred books, but none of them survived. Epicurus attracted a following, however, and one of these was a Roman known as…
Lucretius (96-? BCE).
who wrote a long poem, which survived through the Middle Ages, and which described Lucretius’s views on atomos.
Now we take a long jump into the future (1500 years) while the above mentioned theories held sway and new technology would make possible advances heretofore impossible.
Pierre Gassendi (1592-1655)
was a French philosopher who read Lucretius 1500 years later, and espoused his views on atomos. Since the printing press was now well established, his books on the subject had a wide audience. For the first time the question could be posed to thousands. Prior to this point the subject of atomism could not be settled due to the inability to experimentally confirm or deny the theory. It served only as an interesting intellectual discussion that could not be resolved one way or the other. There needed to be some method of experimentation that could bring some rationale to the discussion.
What we have been dealing with to this point reflects an effort to acquire knowledge through the power of reasoning alone. The name for those who were responsible for this effort of comprehension was “philosophers” (Greek meaning lovers of wisdom).
Even in those days, philosophy took on two directions: first a turning within