Читать книгу The History of Physics from 2000BCE to 1945 - Sheldon J.D. Cohen - Страница 3

As soon as man developed the capability to contemplate who he was in relation to the world about him, he began to wonder if there was a singleness about all objects in his environment. Certainly the differences were visually vast, but could there be a common indivisible building block for all things animate and inanimate?

For instance: if you were able to cut a gold bar in half, and then cut the half piece in half, and then cut the quarter piece in half, and then the eighth, and then the sixteenth, etcetera, when do you have to stop? Is there a point when you would end up with a fragment that could no longer be broken down into a smaller piece (the smallest possible piece still identifiable as gold)? The Greeks named this infinitesimally tiny end piece atomos (atom) or ‘unbreakable’ in Greek.

Some philosophers disputed the atomistic concept and felt that the animate and inanimate objects of the world were made of a material common to our senses, and everything else was a variation and combination of this primary substance.

Thales of Miletos (624-546 BCE) was one of the first to theorize about this concept seriously. The founder of ancient Greek philosophy and physics, Thales suggested that water was the most fundamental structure that led to all other things. His reasoning: the ability of water to become vapor and exhibit motion. This capacity for change and motion, according to the Greeks, indicated life. Thales felt that our universe was a living organism directed by water as the primary substance.

Explanations for natural phenomenon had always relied on myth. Thale’s contribution was a first step in the evolution of thinking from myth to reason.

Thales was also one of the first to study the force of attraction between bodies. Even primitive man undoubtedly recognized this attractive force, but no one ever studied the phenomenon with the intent of understanding what such attraction meant.

Miletos, on the Aegean sea in an area that is now Turkey, was near a town known as Magnesia. Magnesia had abundant deposits of lodestone a naturally occurring type of iron ore well known to attract iron, but no other substance. Someone named this attractive force magnetism and a substance that had this became a “magnet.”

In addition, Thales discovered that rubbing amber with cat fur, caused the amber to attract light objects like feathers or straw. Clearly, this represented a mysterious attractive force, and the Greeks therefore believed that the amber had a ‘soul.’ They considered this force different from magnetism that only involved iron, because many substances also had the ability to attract other objects when rubbed.

The nature of this force would remain a mystery for twenty five hundred years, but would prove to be a major scientific discovery from which great advances evolved, for this attractive force was static electricity.

Thales was forever steeped in study. Plato tells the story about Thales once falling into a well while focusing his attention on the stars above. A servant girl, who pulled him out, stated that he was so eager to know the stars that he paid no attention to what was under his feet. They wrote on his tomb: Here in a narrow tomb great Thales lies; yet his renown for wisdom reached the skies.

Three centuries later, another Greek philosopher, Theophrastus (371-286 BCE) determined that other substances when rubbed shared amber’s unusual attractive power. Could this represent a universal force shared by matter?

Anaximander (610-546 BCE) one of Thales pupils, disputed Thale’s thesis. He denied that the fundamental building block was anything of form and structure such as the water of Thale’s hypothesis, but rather permeated the world and was infinite and timeless and transformed itself into various forms of matter discernable by our senses. This suggested that the real unifying force was more mysterious than could be visualized and lay currently hidden and undiscovered.

Aniximander’s contribution was to suggest that theories based upon the reality of the world around us, and on our visual senses, were perhaps too primitive in terms of the understanding of the time to suggest any real unifying mechanism. More discoveries were necessary before a solid foundation evolved into factual theories. In the meantime, his suggestion of an infinite and timeless primordial building block was closer to the mark, but again would have a many centuries wait for clarification.

Anaximenes (570-528 BCE) disputed both Thales and Anaximander, and suggested that air was the primary building block from which all else was created. Since air was continuously in motion, it was life. In a state of even dispersal,, it presents itself as the air we breathe. In 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.

His 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.

Heraclitus of Ephesus (533-475 BCE) insisted that fire was the source of everything. It too 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 an equilibrium, and his contribution was to suggest that such equilibrium indicated an 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 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 then one basic element there were four: air, fire, earth, and water.

The basic four elements, mixed and partially combined and separated, resulted 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. 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.

Anaxagoras (500-428 BCE) suggested that rather then 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 then 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.

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 him.

Plato (429-347 BCE) and Aristotle (384-322 BCE) never accepted the atomos theory, and since they were so widely respected, their viewpoint held sway. Oposing 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). He wrote a long poem, which survived through the Middle Ages, and which described Lucretius’s views on atomos.

It would take 1500 years until Pierre Gassendi (1592-1655), a French philosopher read Lucretius and espoused his views on atomism. 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 for lovers of wisdom).

Even in those days, philosophy took on two directions: first a turning within to attempt an understanding of human behavior, of morality and ethics; second a turning out to seek explanations of other than the mind---nature to be exact. Such study, the phenomenon of nature throughout the universe, was termed natural philosophy. The word science would not make its appearance until the nineteenth century.