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       Chapter 2 The Changing View of Matter and Energy

      If God created the world, where was he before the Creation? … Know that the world is uncreated, as time itself is, without beginning and end. Mahapurana (India, ninth century)

      What is matter, and how does it move? These are questions that have occupied the thoughts of physicists from ancient times to the present day, and they were fundamental queries for Isaac Newton.

      Our modern view is based upon the rather exotic world of quantum theory, but for most everyday purposes the way in which we manipulate matter and energy relies upon rules and systems discovered between Newton’s lifetime and the present century. For many historians of science, Newton’s ideas about how matter behaves and how energies and forces operate can be seen as a watershed in the development of physics. Indeed, some perceive his work as making possible the Industrial Revolution. Newton provided a focus: he was an individual scientist who drew together the many threads that led from ancient times to his fathering of modern empirical science (a study based upon mathematical analysis as well as experimental evidence). Behind Newton lay some 2,000 years of changing ideas about the nature of the universe; his great achievement was to clarify and to bring together the individual breakthroughs of men like Galileo, Descartes and Kepler and to produce a general overview – a set of laws and rules that has given modern physics a definite structure.

      The ancient Greeks were the first to record their ideas about the nature of matter, and we know of several different schools of reasoning. The two most important for our purposes are the teachings of Aristotle and the ideas of a rival theory – the atomic hypothesis of Democritus.

      The Greek philosophy that prevailed up to Newton’s time was that traditionally attributed to Aristotle – the notion of the four elements: earth, water, air and fire. The alternative was the ideas of Democritus, born some seventy-five years before Aristotle, in 460 BC, who taught that matter is made up of tiny invisible parts, or atoms. Because Aristotle and Plato both largely disapproved of Democritus’s atomic theory, however, it was almost completely ignored from Aristotle’s day until its partial revival during the seventeenth century.

      The first person to formulate the idea of the four elements was actually a Sicilian philosopher named Empedocles, some half-century before Aristotle’s birth, but the idea was refined and made popular by Aristotle. It is thought that the concept first arose from watching the action of burning. For example, when green wood is burned, the fire is visible by its own light, the smoke vanishes into air, water boils from the wood, and the remaining ashes are clearly earth-like. This gave rise to the idea that everything in the universe is composed of different proportions of these four fundamental elements – an idea which became the foundation of Aristotle’s work in natural philosophy that was handed down to future generations.

      Aristotle was born in 384 BC at Stagira in Chalcidice. The son of the physician to Philip, King of Macedon, he later became the pupil of Plato and, in middle age, the teacher of Alexander the Great. He wrote a collection of tracts that were not only influential in his own time but whose rediscovery in an incomplete form by European scholars during the thirteenth century heralded a return to learning and the earliest emergence of the Renaissance. Those most relevant to his thoughts on natural philosophy (what by the eighteenth century had become known as physics) were On Generation and Corruption and Physical Discourse, which concentrated upon ideas concerning matter, form, motion, time and the heavenly and earthly realms.

      To Aristotle, the earthly realm was composed of a blend of the four elements which, if left to settle, would form layers: water falling through air (or air moving up through water, as do bubbles), solid earth falling through water and air, and fire existing in the top layer because it moves up through air. Using this model, Aristotle would have explained the fall of an apple as being due to the earthy and watery parts of the solid apple trying to find their natural place in the universe, falling through air to reach the ground. As well as popularising the idea of the four elements, Aristotle also pioneered the concept of the Unmoved Mover – the name he gave to the omnipotent being who maintained the movement of the heavens, keeping the Sun and the planets travelling around the Earth.

      Aristotle’s work was encyclopedic in range, and he wrote on almost all subjects known at the time, covering logic, philosophy, biology, astronomy and physics. His strongest subjects were logic and, of the sciences, biology; his weakest was physics. Most significant for how Aristotle arrived at many of his scientific ideas was his creation of syllogistic logic: the principle that a conclusion can be reached as a logical consequence of two preceding premisses. An example of this is the collection of statements ‘All elephants are animals; all animals are living things; therefore all elephants are living things.’

      Syllogisms are powerful tools in the study of logic, and were used as a fundamental mathematical procedure until the nineteenth century, when they were superseded by more versatile ideas, but their use is a rather superficial way to conduct science, because syllogistic logic does not contain an element of experiment: syllogisms consist merely of two statements and a conclusion based upon superficial observation or deductive reasoning.

      Plato, Aristotle’s teacher (and the man who established the school at the Academy in Athens which lasted nine centuries), actively disliked experiment and so it was never established as a guiding principle for Greek natural philosophy. Instead, Aristotle and the generations of Greek thinkers who followed him created a rigid set of rules based upon syllogistic logic only, producing a distorted picture of reality. But, because of Aristotle’s stature, this limited approach became endowed with an aura of infallibility which persisted until the beginning of the modern era. The historian Charles Singer has said of this unfortunate process:

      The whole theory of science was so interpreted, and the whole of logic was so constructed, as to lead up to the ideal of demonstrative science [i.e. conclusions reached through reasoning alone], which in its turn rested on a false analogy which assimilated it to the

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