The History of Physics from 2000BCE to 1945. Sheldon J.D. Cohen

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      The History of Physics from 2000BCE to 1945

      by

      Sheldon Cohen

      Copyright 2012 Sheldon Cohen,

      All rights reserved.

      Published in eBook format by eBookIt.com

       http://www.eBookIt.com

      ISBN-13: 978-1-4566-0743-2

      No part of this book may be reproduced in any form or by any electronic or mechanical means including information storage and retrieval systems, without permission in writing from the author. The only exception is by a reviewer, who may quote short excerpts in a review.

      THE FIRST THOUGHT EXPERIMENT: IS THERE A PRIMORDIAL BUILDING BLOCK?

      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 СКАЧАТЬ