I can do no better than to follow the example set by Asimov, and start my explanation of nuclear physics, as he would do, at the very beginning. Even more, I'm going to use one of Asimov's own book as a source - Atom: Journey Across the Subatomic Cosmos.
The Theory of the Atom
Just why, and how, did a Greek philosopher (or naturalist - science didn't come into vogue until the 1300s, and is from the Latin word "scientia") - knowledge) ever think of the idea that matter was made from atoms, and that an atom could not be broken down into any smaller parts.
Asimov explains it this way.
Natural philosophers back in the time of the ancient Greeks were curious and posed questions to themselves - and others.
"Suppose you had a heap of thousands of small, smooth pebbles. If you were divide this heap into two smaller heaps, and then teo smaller again and again (by getting rid of one of the heaps each time, and dividing the remainder) how long could this process go on.
No matter how large your initial heap of pebbles, eventually you would be left with just two pebbles, and if you threw one away, you'd be left with one.
(According to Asimov, if you started with a million pebbles, you'd be down to two pebbles after about twenty divisions).
Now, take your final pebble, and pound it with a hammer to reduce it to the smallest possible fragments. Imagine then, finally, that the pebble has been ground into dust so fine you can't see it, can that continue to be divided by two?
The Greek philosopher Leucippus (490 - ? BC) is the first person we know by name who considered this problem of dividing matter. He insisted that, sooner or later, a fragment would reach so small a size that it could not be broken down into anything smaller.
Democritus (460-370 BC), a pupil of Leucippis, believed in his theory, and called this finalk fragment an "atomos" - "unbreakable." According to Democritus, al matter consisted of a collection of atoms, and if there was space between the atoms, that space contained nothing - it was a void.
Democritus is said to have written 60 books (handwritten, of course). But Democritus' theory was scoffed at in his own time, and none of his books survive.
Plato and Aristotle didn't accept the view of atoms, they believed, and taught, that matter could be divided endlessly. Epicurus, on the other hand, did believe and teach the theory of atoms. He wrote 300 books, none of them survive.
If none of those books survived, how do we know about them?
Roman Titus Lucretius Carus (96-55 BC, living 200 years after Epicurus) also believed in the theory of atoms. Known as Lucretius, he published a long poem, in 56 BC, the year before his death, "De Rerun Natura (On the nature of things). In it, he explained Epicurus' theory of atomism in great detail.
This book was popular in its time. But after about 4 AD, with Christianity growing in power, Lucretius was denounced for what was considered to be atheism. His books were no longer copied (still hand copied) and extant books were destroyed or lost.
One copy - one - survived the Middle Ages and was discovered in 1417 (in Florence). It was recopied then, and 50 years later, when Gutenberg invented the printing press, it was one of the first items to be printed.
This poem, then, spread throughout western Europe and was the chief source of knowledge of the ancient theories of atomism.
According to Wikipedia:
Purpose of the poemAccording to Lucretius's frequent statements in his poem, the main purpose of the work was to free Gaius Memmius's (and presumably all of mankind's) mind of superstition and the fear of death. He attempts this by expounding the philosophical system of Epicurus, whom Lucretius apotheosizes as the hero of his epic poem.
Lucretius identifies superstition (religio in the Latin) with the notion that the gods/supernatural powers created our world or interfere with its operations in any way. He argues against fear of such gods by demonstrating through observations and logical argument that the operations of the world can be accounted for entirely in terms of natural phenomena—the regular but purposeless motions and interactions of tiny atoms in empty space—instead of in terms of the will of the gods.
He argues against the fear of death by stating that death is the dissipation of a being's material mind. Lucretius uses the analogy of a vessel, stating that the physical body is the vessel that holds both the mind (mens) and spirit (anima) of a human being. Neither the mind nor spirit can survive independent of the body. Thus Lucretius states that once the vessel (the body) shatters (dies) its contents (mind and spirit) can, logically, no longer exist. So, as a simple ceasing-to-be, death can be neither good nor bad for this being. Being completely devoid of sensation and thought, a dead person cannot miss being alive. According to Lucretius, fear of death is a projection of terrors experienced in life, of pain that only a living (intact) mind can feel. Lucretius also puts forward the 'symmetry argument' against the fear of death. In it, he says that people who fear the prospect of eternal non-existence after death should think back to the eternity of non-existence before their birth, which they probably do not fear.
[edit] Structure of the poemThe structure of the poem over the six books falls into two main parts. The first three books provide a fundamental account of being and nothingness, matter and space, the atoms and their movement, the infinity of the universe both as regards time and space, the regularity of reproduction (no prodigies, everything in its proper habitat), the nature of mind (animus, directing thought) and spirit (anima, sentience) as material bodily entities, and their mortality, since they and their functions (consciousness, pain) end with the bodies that contain them and with which they are interwoven. The last three books give an atomic and materialist explanation of phenomena preoccupying human reflection, such as vision and the senses, sex and reproduction, natural forces and agriculture, the heavens, and disease.
[edit] Style of the poemHis poem De Rerum Natura (usually translated as"On the Nature of Things" or "On the Nature of the Universe") transmits the ideas of Epicurean physics, which includes Atomism, and psychology. Lucretius was one of the first Epicureans to write in Latin.
Lucretius compares his work in this poem to that of a doctor healing a child: just as the doctor may put honey on the rim of a cup containing bitter wormwood (most likely Absinth Wormwood) believed to have healing properties, the patient is "tricked" into accepting something beneficial but difficult to swallow, "but not deceived" by the doctor (Book IV lines 12-19). The meaning of this refrain found throughout the poem is debatable.
Stylistically, most scholars attribute the full blossoming of Latin hexameter to Virgil. De Rerum Natura however, is of indisputable importance for the part it played in naturalizing Greek philosophical ideas and discourse in the Latin language and its influence on Virgil and other later poets. Lucretius's hexameter is very distinct from the smooth urbanity of Virgil or Ovid. His use of heterodynes, assonance, and vigorously syncopated Latin forms create a harsh acoustic to some ears, although this is probably merely an impression created by contrast with later poets and general unfamiliarity with Latin poetry recited by skilled readers. John Donne has a similar reputation in English poetry because of his powerful and thought-laden discourse. The sustained energy of Lucretius's poetry (even when treating highly technical particularities, such as the movement of atoms through space or the films which give rise to vision when they strike the eye) is virtually unparalleled in Latin literature, with the possible exception of parts of Tacitus's Annals, or perhaps Books II and IV of the Aeneid. The six books contain many formulaic elements such as deliberately repeated lines, refrains, and regularized emotional peaks.
Among many poetic high points a few should be mentioned. The introduction to Book I (the invocation to Venus and Spring) is unsurpassed, both in its initial ecstatic address to the life-force and regeneration, and in the celebration of the courage and clear-sightedness of Epicurus and the vitriolic polemic against superstition (Latin: "religio") which provide the bridge to the main didactic body of the poem. The opening sections of the various books emphasize the novelty of the undertaking Lucretius has set himself and the gratitude mankind owes to Epicurus for delivering it from unfounded terrors and an empty, joyless and servile life. And the great conclusions to Book III (on death and why it holds no terrors) and Book VI (on disease, especially the plague) are as graphic as anything in literature, as are various accounts throughout the poem of storms, battles, fire and flood.
No comments:
Post a Comment