CHAPTER IV

SCIENCE IN THE GOLDEN AGE OF GREECE

Our science, in contrast with others, is not founded on a single period of human history, but has accompanied the development of culture through all its stages. Mathematics is as much interwoven with Greek culture as with the most modern problems in engineering. She not only lends a hand to the progressive natural sciences, but participates at the same time in the abstract investigations of logicians and philosophers. - Klein.

There still remain three studies suitable for freemen. Calculation in arithmetic is one of them; the measurement of length, surface, and depth is the second; and the third has to do with the revolutions of the stars in reference to one another . . . there is in them something that is necessary and cannot be set aside . . . if I am not mistaken, [something of] divine necessity. - Plato.

LITERATURE AND ART. The fifth century B.C. witnessed that astonishing flowering of the Greek genius in literature and military glory which has made it ever since famous. The battles of Marathon and Salamis had flung back the Asiatic hosts which threatened to overrun and enslave Europe, and had transformed the Greeks from a group of jealous and parochial city states into a great democratic nation. Trade prospered, wealth increased, and for about a century letters, art, and science flourished as never before and never since. History began to be written by Herodotus and Thucydides. The drama was developed by Eschylus, Sophocles, and Euripides to such a pitch that even to-day, after the lapse of nearly 2500 years, crowds listen with eager interest to the Edipus of Sophocles and the Iphigenia of Euripides, while the poetry of Pindar and the wit of Aristophanes have never lost their charm. In architecture and the plastic arts the Parthenon and its sculptures still testify to Greek supremacy.

In science, also, great names testify to memorable deeds. No such perfection, to be sure, was attained in science as in literature and in sculpture, but vast progress was made in mathematical science beyond anything hitherto accomplished, and the foundations were securely laid for a rational interpretation of man and of nature. Literature, architecture, sculpture, and the drama require no special apparatus or reagents. Mathematical science also is not dependent upon such externals, being in this respect like literature and art, and we find geometry and arithmetic at the outset moving forward far more rapidly than natural or physical science.

PARMENIDES.-The recognition of the spherical shape of the earth and its division into zones are attributed not only to the Pythagoreans, but also to Parmenides of Elis, who lived in the early part of the fifth century. He introduced a system of concentric spheres analogous to that soon to be so highly developed by Eudoxus. He identified the evening and the morning stars, and attributed the moon's brightness to reflected light. He regarded the sun as consisting of hot and subtle matter detached from the Milky Way, the moon chiefly of the dark and cold.

EMPEDOCLES. - Passing over the guesses of Heraclitus and Parmenides at the riddle of existence and of man and nature, we may pause for a moment to examine the speculations of Empedocles (about 455 B.C.). A native of Agrigentum in southern Sicily, Empedocles was regarded as poet, philosopher, seer, and immortal god. He appears to have been a close observer of nature, understanding the true cause of solar eclipses and believing the moon to be twice as far from the sun as from the earth. The latter is held in place by the rapidly rotating heavens "as the water remains in a goblet which is swung quickly round in a circle." Aristotle attributes to Empedocles that analysis of the universe into the four "elements," earth, air, fire, and water, which until comparatively recent times was universally accepted as fundamental. It is, nevertheless, not only misleading but absurd to hold with Gomperz ("Greek Thinkers," I, 230) that Empedocles' theory of the four elements "takes us at a bound into

the heart of modern chemistry." The facts seem rather to be that Empedocles put together and hospitably accepted and clarified the theories of his various predecessors. He is the first sanitarian of whom we have any record, for Empedocles is credited with having cut down a hill of his native city and thus cured a plague by letting in the north wind, and to have done a similar service to the neighboring "parsley" city of Selinus (Selinunte) by simply draining a local marsh.

The following is a fragment from the writings of Empedocles:

So all beings breathe in and out; all have bloodless tubes of flesh spread over the outside of the body, and at the openings of these the outer layers of skin are pierced all over with close-set ducts, so that the blood remains within, while a facile opening is cut for the air to pass through. Then whenever the soft blood speeds away from these, the air speeds bubbling in with impetuous wave, and whenever the blood leaps back the air is breathed out; as when a girl, playing with a clepsydra of shining brass, takes in her fair hand the narrow opening of the tube and dips it in the soft mass of silvery water, the water does not at once flow into the vessel, but the body of air within pressing on the close-set holes checks it till she uncovers the compressed stream; but then when the air gives way the determined amount of water enters. And so in the same way when the water occupies the depths of the bronze vessel, as long as the narrow opening and passage is blocked up by human flesh, the air outside, striving eagerly to enter, holds back the water inside behind the gates of the resounding tube, keeping control of its end, until she lets go with her hand. Then, on the other hand, the very opposite takes place to what happened before; the determined amount of water runs off as the air enters. Thus in the same way when the soft blood, surging violently through the members, rushes back into the interior, a swift stream of air comes in with hurrying wave, and whenever it [the blood] leaps back, the air is breathed out again in equal quantity. Fairbanks.

ANAXAGORAS. (500-428 B.C.) For the student of science Anaxagoras, a native of Clazomene in Asia Minor, is more important than Empedocles. Turning aside from wealth and civic distinction in his enthusiasm for science, he seems to have occupied

himself with the problem of squaring the circle, a problem attacked even by the Egyptians with some degree of success, and destined to exercise great influence on the development of Greek geometry. The beginnings of perspective are also attributed to him, in connection with studies of the stage. He was particularly interested in a great meteorite - the appearance of which he was afterwards said to have predicted - supposing it to have fallen from the sun, and inferring that the latter was a "mass of red-hot iron greater than the Peloponnesus," not very distant from the earth. Like the Pythagoreans he assigned as the order of distances:- moon, sun, Venus, Mercury, Mars, Jupiter, Saturn. The earth's axis was inclined, in order that there might be variations of climate and habitability. He explained the moon's phases correctly, also solar and lunar eclipses, but he misinterpreted the Milky Way as due to the shadow cast by the earth. His theory of the nature and origin of the cosmos, viz. that it was material and had come by the combination and differentiation of primitive elementary substances or "seeds" of matter, was repugnant to those holding the polytheistic dogmas of his time and brought him into popular disfavor. Convicted of impiety, he died in exile, 428 B.C. By his insistence upon the importance of minute invisible "seeds" or particles of matter he paved the way for the "atomism" of Leucippus and Democritus. THE ATOMISTS. A very little observation of external nature shows that disintegration is forever going on. Ice turns to water, water to vapor, rocks to sand and sand to dust in other words, masses to particles. Furthermore, dust vanishes and vapor disappears, while clouds and fogs, rain and snow, make their appearance without obvious cause, and dust accumulates from invisible sources. What is more reasonable than to suppose that visible things-rocks and ice and water - become gradually resolved into invisible particles, and that these in their turn condense into new visible substances at some later time? For these or similar ideas the material "seeds" of Anaxagoras had, as stated above, paved the way, when later emphasized by Leucippus and his more famous pupil Democritus. Of the life of Leucippus

almost nothing is known, but he was probably a contemporary of Empedocles and Anaxagoras, and possibly a pupil of Zeno. Leucippus assumed the existence of empty space as well as of matter, and held that of atoms all things are constituted. Space is infinite in magnitude, atoms infinite in number and indivisible, with only quantitative differences. Atoms are always in activity, and worlds are produced by atoms variously shaped and weighted, falling in empty space and giving rise to an eddying motion by mutual impact.

DEMOCRITUS OF ABDERA was a pupil and associate of Leucippus, whose theories of empty space and material atoms he developed and made so famous that his own name alone is often associated with them. Of his life, his works, and his death little is certainly known, but he may be regarded as marking the culmination and conclusion of the Ionian school; and his reputation, both in antiquity and in medieval times, was immense. Like contemporary and preceding philosophers, his writings were in verse, and Cicero is said to have deemed his style worthy of comparison with that of Plato. His somewhat boastful comparison of his own geometrical power with that of the Egyptian rope-stretchers has been quoted.

Democritus appears to have agreed closely in his interpretation of nature with Leucippus, and regarded empty space and atoms as cosmic elements. He also held that by the motion of the atoms was produced the world with all that it contains. Soul and fire are of one nature, their atoms small, smooth, and round. By inhaling them life is maintained. Hence the soul perishes with and in the same sense as the body, a doctrine which made Democritus odious to later generations. Dante, for example, places him far down in hell as "ascribing the world to chance."

The atomic theory of perception held that from every object "images" of that object are being given off in all directions, some of which enter the organs of sense and cause sensations." Democritus further held that sensations are the only sources of our knowledge. He was regarded as one of the extreme sceptics of antiquity, as e.g. in this saying, "We know nothing: not even