User:Anthony.Sebastian/Sandbox-3

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Our entire body operates by electricity. Gnarled living electrical cables extend into the depths of our brains; intense electric and magnetic force fields stretch into our cells, flinging food or neuro- transmitters across microscopic barrier membranes; even our DNA is controlled by potent electrical forces.       — David Bodanis

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3CO₂ + 6H₂O +343 kcal light energy → C₃H₆O₃ [triose] + 30₂ +3H₂O

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Matter (chemistry) for CZ

From the perspective of classical mechanics, or more specifically, Newtonian mechanics, chemists describe matter as anything that occupies space and has mass. That includes the subatomic particles that scientists can discern as having physical extension and mass, all the chemical elements, or elementary substances — "the substances from which everything tangible is made," — and all the substances chemical elements make up.

A minimal account of matter from the chemist´s Newtonian perspective requires discussion of the meanings of the terms 'thing' (or 'anything' or 'somthing' or 'everything'), 'mass', 'substance', 'chemical elements', and 'compounds'. This article uses the word 'object' generically to refer to something that occupies space and has mass.

Overview

Thing

Chemists define matter as anything (any thing) that occupies space and has mass. They do not, in conjunction, define thing, presumably because they assume common knowledge of what the word 'thing' means. Indeed, semantic linguists have discovered that the word 'thing' has a primary meaning not definable without using words whose definitions ultimately require the word 'thing'. They find that ulike most words in the English lexicon, the word 'thing' occurs universally among the Earth's languages, though not universally pronounced as pronounced in English. 'Thing' qualifies as one of approximately 60 additional universal semantic primitives, or semantic primes, which, though themselves indefinable, serve as the basic set of words for defining all the other words in the lexicon.

Though semantically primitive, 'thing' still has meaning, a meaning a child learns from the way its elders use it, the word's origin going back to the deep-time beginnings of human speech, however prononced then. A child hears his English-speaking parents frequently uttering 'thing' in reference to what we would call material objects: "This drawer has too many things in it", "Give me that thing before you hurt yourself", "Put your things away".

We would understand, then, that anything that occupies space and has mass represents matter, providing we know the meaning of the words 'occupy', 'space', and 'mass'. A semanticist might readily define the first to in terms of semantic primitives, but not so readily the third, 'mass', considered in the next section.

Mass

See: Mass

Mass gives a measure of the quantity of matter in an object, expressed in kilograms (kg), a basic unit of the International System of Units (SI units). Three related measures of mass exist, referred to as 'inertial mass', 'passive gravitational mass', and 'active gravitational mass'. Physicists have established that the three measures give equivalent values despite their different conceptual bases.

Inertial mass relates to a quantity of matter's resistance to motion in response to an applied force, resistance measured in terms of the degree of acceleration it undergoes in response to the applied force. For a given force, an object with a larger mass accelerates more slowly than an object with a smaller mass. For an iron block to achieve the same acceleration of a wood block requires a larger force than that acting on the wood block. Newton´s Second Law of Motion formulates the mass: force equals mass times acceleration, F=ma, mass expressed in kilograms, force expressed in newtons, and acceleration expressed in meters per second per second. From the chemist´s Newtonian perspective, one cannot create mass or destroy it, consequent to the law of conservation of mass.

Passive gravitational mass gives a measure of the quantity of matter in virtue of its reference to the property of an object to react to a gravitational field, that is, to react by attraction to another mass generating a mass-attracting force, a reaction which Newton called gravitation. The magnitude of the force attracting the object measures its weight, which increases with larger attracting masses, but the object´s mass remains constant, indicating no fixed weight for any given quantity of matter in an object.

Active gravitational mass gives a measure of the quantity of matter in virtue of its reference to the property of an object to create a field of force surrounding it that attracts another object — its property of creating a so-called gravitational field.

The equivalence of inertial mass and passive gravitational mass derives from Newton´s law of universal gravitation and the observation that different masses accelerate equally when let loose from the same height in a given gravitational field. The equivalence of passive and active gravitational mass derives both from Newton´s law of universal gravitation, Newton´s law of action and reaction, and the observation that one cannot shield an object from the force of gravity. The derivations are the provenance of physics.

Three points to note:

1. An object´s mass gives a measure of the quantity of matter comprising the object;
2. Objects have the same mass whether measured as inertial, passive, or gravitational mass;
3. Einstein´s theories of special and general relativity modify the Newtonian concept of mass, which however give a useful measure of mass for most purposes in general chemistry.

 

Substances

Chemistry conceptualizes matter as consisting of distinguishable types, referred to as 'substances'. Examples of substances include such commonly recognized space-occupying masses as water in a glass container, the glass container itself, copper wire, a gem of pure diamond, air enclosed in a balloon, atoms, and molecules.

Different substances have different properties, either physical or chemical properties, depending on whether or not testing for the property involves the formation of another substance or substances.

All substances fall under two generic categories, 'pure substances' and 'mixtures'. Chemists classify as the quintessentially pure substances the chemical elements, types of matter composed solely of a single species of atom, such as the copper atoms fashioned into copper wire, the carbon atoms comprising a diamond gem, or iron atoms in a chunk of purified iron. Ninety-four different species of atoms occur naturally on Earth, each collection, or sample, of which that consists solely of atoms of a single species constitutes a pure substance of the type of matter referred to as a chemical element, or elementary substance.

Compounds

The atoms of two or more different chemical elements potentially can bind to each other, in constant proportions, by any one of a variety of types of chemical bonds, forming in the process new types of pure substances referred to as 'compounds'. Water exemplifies a compound, composed of units of hydrogen and oxygen atoms tightly bonded, in the same proportion per bonded unit particle, in this case, two hydrogen atoms and one oxygen atom per unit particle of compound, expressed in chemical formula as H₂O. Chemists have identified the bonds in a unit particle of the water compound as so-called covalent bonds, a type of bond that involves electron sharing between the two hydrogen atoms and the oxygen atom, and refer to the unit particle as a molecule. Chemists express quantities of H₂O with a variety of measures of mass, such as kilograms, a basic quantitative unit in the International System of Units (SI units), among six other basic quantitative units, and as moles, defined in terms of the number of atoms of a specified isotope of carbon in a specified quantity of isotope expresed in kilograms.

Alcmaeon's extant fragments

Health is the equality of rights of the functions.

J.B. Wilbur lists the English translation of the extant fragments of Alcmaeon's book:

• Alcmaeon of Croton, son of Peirithous, said the following to Brotinus and Leon and Bathyllus: concerning things unseen, (as) concerning things mortal, the gods have certainty, whereas to us as men conjecture (only is possible).

• Men perish because they cannot join the beginning to the end.

• (In mules, the males are sterile because of the fineness and coldness of the seed, and the females because their wombs do not open).

• Health is the equality of rights of the functions, wet-dry, cold-hot, bitter-sweet and the rest; but single rule among them causes disease; the single rule of either pair is deleterious. Disease occurs sometimes from an internal cause such as excess of heat or cold, sometimes from an external cause such as excess or deficiency of food, sometimes in a certain part, such as blood, marrow or brain; but these parts also are sometimes affected by external causes, such as certain waters or a particular site or fatigue or constraint or similar reasons. But health is the harmonious mixture of the qualities.

• It is easier to guard against an enemy than against a friend.

Notes from SEP re Alcmaeon

lcmaeon from SEP

Book written between 500-450 BC. 1st to identify brain as seat of understanding Distinguished unerstandin rom perception Sense organs connected to brain by hannels Developed argument for soul immortality Physiology: sleep, death, embryonic development Influenced later greek philosopher

Aristotle wrote a treatise responding to him, Plato adopted his argument for the immortality of the soul, and both Plato and Philolaus accepted his view that the brain is the seat of intelligence.

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Liven in croton, so italy Physician-pilosopher Strong medical tradition developed in crotonj

Pythagorean or not? Aristotle wrote a separate book on Alcmaeon

The overwhelming majority of scholars since 1950 have accordingly regarded Alcmaeon as a figure independent of the Pythagoreans (e.g., Guthrie 1962 and Lloyd 1991, 167; Zhmud 1997, 70-71, is one of the few exceptions), although, as a fellow citizen of Croton, he will have been familiar with their thought.

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One group of scholars dates the publication of Alcmaeon's book to around 500 (Burkert 1972, 292; Kirk, Raven, Schofield 1983, 339 [early 5th]) so that he would have been born around 540. Another group has him born around 510 so that his book would have been published in 470 or later (Guthrie 1962, 358 [480-440 BC]; Lloyd 1991, 168 [490-430 BC]). In either case Alcmaeon probably wrote before Empedocles, Anaxagoras and Philolaus. He is either the contemporary or the predecessor of Parmenides.

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He thus takes the stance of the scientist who draws inferences from what can be perceived, and he implicitly rejects the claims of those who base their account of the world on the certainty of a divine revelation (e.g., Pythagoras, Parmenides B1).

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Socrates connects this view of the brain with an empiricist epistemology, which Aristotle will later adopt (Posterior Analytics 100a3 ff.). This epistemology involves three steps: first, the brain provides the sensations of hearing, sight and smell, then, memory and opinion arise from these, and finally, when memory and opinion achieve fixity, knowledge arises. Some scholars suppose that this entire epistemology is Alcmaeon's (e.g., Barnes 1982, 149 ff.), while others more cautiously note that we only have explicit evidence that Alcmaeon took the first step (e.g., Vlastos 1970, 47, n.8).

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he only conclusions we can reasonably draw about Alcmaeon from the passage are that he excised the eyeball of an animal and observed poroi (channels, i.e. the optic nerve) leading from the eye in the direction of the brain (Lloyd 1975). Theophrastus' account of Alcmaeon's theory of sensation implies that he thought that there were such channels leading from each of the senses to the brain: All the senses are connected in some way with the brain. As a result, they are incapacitated when it is disturbed or changes its place, for it then stops the channels, through which the senses operate. (DK, A5)

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It would be a serious mistake then to say that Alcmaeon discovered dissection or that he was the father of anatomy, since there is no evidence that he used dissection systematically or even that he did more than excise a single eyeball.

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The idea that health depends on a balance of opposed factors in the body is a commonplace in Greek medical writers. Although Alcmaeon is the earliest figure to whom such a conception of health is attributed, it may well be that he is not presenting an original thesis but rather drawing on the earlier medical tradition in Croton. Perhaps what is distinctive to Alcmaeon is the use of the specific political metaphor and terminology (isonomia, monarchia). Just as Anaximander explained the order of the cosmos in terms of justice in the city-state, so Alcmaeon used a political metaphor to explain the order of the human body.

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Contrary to a popular Greek view, which regarded the father alone as providing seed, a view that would be followed by Aristotle (Lloyd 1983, 86 ff.), Alcmaeon argued that both parents contribute seed (DK, A13) and that the child takes the sex of the parent who contributes the most seed (DK, A14).

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More significantly, he used analogies with animals and plants in developing his accounts of human physiology. Thus, the pubic hair that develops when human males are about to produce seed for the first time at age fourteen is analogous to the flowering of plants before they produce seed (DK, A15); milk in mammals is analogous to egg white in birds (DK, A16).

Pasted from <http://plato.stanford.edu/archives/win2008/entries/alcmaeon/> Alcmaeon agrees with these Pythagoreans in regarding the opposites as principles of things. Aristotle complains, however, that Alcmaeon did not arrive at a definite set of opposites but spoke haphazardly of white, black, sweet, bitter, good, bad, large and small, and only threw in vague comments about the remaining opposites. It may well be that Alcmaeon's primary discussion of opposites was in relation to his account of the human body (DK, B4; see the discussion of his medical theories above). Aristotle's language supports this suggestion to some extent, when he summarizes Alcmaeon's view as that "the majority of human things (tôn anthrôpinôn) are in pairs" (Metaph. 986a31). Isocrates (DK, A3) says that Alcmaeon, in contrast to Empedocles, who postulated four elements, said that there were only two, and, according to a heterodox view, Alcmaeon posited fire and earth as basic elements (Lebedev 1993).

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• Long, A. A., (ed.), 1999, The Cambridge Companion to Early Greek Philosophy, Cambridge: Cambridge University Press

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• Taylor, C. C. W., (ed.), 1997, Routledge History of Philosophy, Volume 1: From the Beginning to Plato, London: Routledge

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Sep au Carl Huffman

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