Astronomical Myths Part 13

It is remarkable to notice that the proofs then used by geographers of the sphericity of the earth are just those which we should use now. Thus Strabo says, "The indirect proof is drawn from the centripetal force in general, and the tendency that all bodies have in particular towards a centre of gravity. The direct proof results from the phenomena observed on the sea and in the sky. It is evident, for example, that it is the curvature of the earth that alone prevents the sailor from seeing at a distance the lights that are placed at the ordinary height of the eye, and which must be placed a little higher to become visible even at a greater distance; in the same way, if the eye is a little raised it will see things which previously were hidden." Homer had already made the same remark.

On this globe, representing the world, Strabo and the cosmographers of his time placed the habitable world in a surface which he describes in the following way: "Suppose a great circle, perpendicular to the equator, and pa.s.sing through the poles to be described about the sphere.

It is plain that the surface will be divided by this circle, and by the equator into four equal parts. The northern and southern hemispheres contain, each of them, two of these parts. Now on any one of these quarters of the sphere let us trace a quadrilateral which shall have for its southern boundary the half of the equator, for northern boundary a circle marking the commencement of polar cold, and for the other sides two equal and opposite segments of the circle that pa.s.ses through the poles. It is on one such quadrilateral that the habitable world is placed." He figures it as an island, because it is surrounded on all sides by the sea. It is plain that Strabo had a good idea of the nature of gravity, because he does not distinguish in any way an upper or a lower hemisphere, and declares that the quadrilateral on which the habitable world is situated may be any one of the four formed in this way.

The form of the habitable world is that of a "chlamys," or cloak. This follows, he says, both from geometry and the great spread of the sea, which, enveloping the land, covers it both to the east and to the west and reduces it to a shortened and truncated form of such a figure that its greatest breadth preserved has only a third of its length. As to the actual length and breadth, he says, "it measures seventy thousand stadia in length, and is bounded by a sea whose immensity and solitude renders it impa.s.sable; while the breadth is less than thirty thousand stadia, and has for boundaries the double region where the excess of heat on one side and the excess of cold on the other render it uninhabitable."

The habitable world was thus much longer from east to west than it was broad from north to south; from whence come our terms _longitude_, whose degrees are counted in the former direction, and _lat.i.tude_, reckoned in the latter direction.

Eratosthenes, and after him Hipparchus, while he gives larger numbers than the preceding for the dimensions of the inhabited part of the earth, namely, thirty-eight thousand stadia of breadth and eighty thousand of length, declares that physical laws accord with calculations to prove that the length of the habitable earth must be taken from the rising to the setting of the sun. This length extends from the extremity of India to that of Iberia, and the breadth from the parallel of Ethiopia to that of Ierne.

That the earth is an island, Strabo considers to be proved by the testimony of our senses. For wherever men have reached to the extremities of the earth they have found the sea, and for regions where this has not been verified it is established by reasoning. Those who have retraced their steps have not done so because their pa.s.sage was barred by any continent, but because their supplies have run short, and they were afraid of the solitude; the water always ran freely in front of them.

It is extraordinary that Strabo and the astronomers of that age, who recognised so clearly the sphericity of the earth and the real insignificance of mountains, should yet have supposed the stars to have played so humble a part, but so it was; and we find Strabo arguing in what we may call quite the contrary direction. He says, "the larger the ma.s.s of water that is spread round the earth, so much more easy is it to conceive how the vapours arising from it are sufficient to nourish the heavenly bodies."

[Ill.u.s.tration: FIG. 33.--THE EARTH OF THE LATER GREEKS.]

Among the Latin cosmographers we may here cite one who flourished in the first century after Christ, Pomponius Mela, who wrote a treatise, called _De Situ Orbis_. From whatever source, whether traditional or otherwise, he arrived at the conclusion, he divided the earth into two continents, our own and that of the Antichthones, which reached to our antipodes.

This map was in use till the time of Christopher Columbus, who modified it in the matter of the position of this second continent, which till then remained a matter of mystery.

[Ill.u.s.tration: FIG. 34.--POMPONIUS MELA'S COSMOGRAPHY.]

Of those who in ancient times added to the knowledge then possessed of cosmography, we should not omit to mention the name of Pytheas, of Ma.r.s.eilles, who flourished in the fourth century before our era. His chief observations, however, were not so closely related to geography as to the relation of the earth with the heavenly bodies. By the observation of the gnomon at mid-day on the day of the solstice he determined the obliquity of the ecliptic in his epoch. By the observation of the height of the pole, he discovered that in his time it was not marked by any star, but formed a quadrilateral with three neighbouring stars, [Greek: b] of the little Bear and [Greek: k] and [Greek: a] of the Dragon.

CHAPTER X.

COSMOGRAPHY AND GEOGRAPHY OF THE CHURCH.

After the writers mentioned in the last chapter a long interval elapsed without any progress being made in the knowledge of the shape or configuration of the earth. From the fall of the Roman Empire, whose colonies themselves gave a certain knowledge of geography, down to the fifteenth century, when the great impetus was given to discovery by the adventurous voyagers of Spain and Portugal, there was nothing but servile copying from ancient authors, who were even misrepresented when they were not understood. Even the peninsula of India was only known by the accounts of Orientals and the writings of the Ancients until the beginning of the fifteenth century. Vague notions, too, were held as to the limits of Africa, and even of Europe and Asia--while of course they knew nothing of America, in spite of their marking on their maps an antichthonal continent to the south.

Denys, the traveller, a Greek writer of the first century, and Priscian, his Latin commentator of the fourth, still maintained the old errors with regard to the earth. According to them the earth is not round, but leaf-shaped; its boundaries are not so arranged as to form everywhere a regular circle. Macrobius, in his system of the world, proves clearly that he had no notion that Africa was continued to the south of Ethiopia, that is of the tenth degree of N. lat.i.tude. He thought, like Cleanthus and Crates and other ancient authors, that the regions that lay nearest the tropics, and were burnt by the sun, could not be inhabited; and that the equatorial regions were occupied by the ocean.

He divided the hemisphere into five zones, of which only two were habitable. "One of them," he said, "is occupied by us, and the other by men of whose nature we are ignorant."

Orosus, writing in the same century (fourth), and whose work exercised so great an influence on the cosmographers of the middle ages and on those who made the maps of the world during that long period, was ignorant of the form or boundaries of Africa, and of the contours of the peninsulas of Southern Asia. He made the heavens rest upon the earth.

S. Basil, also of the fourth century, placed the firmament on the earth, and on this heaven a second, whose upper surface was flat, notwithstanding that the inner surface which is turned towards us is in the form of a vault; and he explains in this way how the waters can be held there. S. Cyril shows how useful this reservoir of water is to the life of men and of plants.

Diodorus, Bishop of Tarsus, in the same century, also divided the world into two stages, and compared it to a tent. Severia.n.u.s, Bishop of Gabala, about the same time, compared the world to a house of which the earth is the ground floor, the lower heavens the ceiling, and the upper, or heaven of heavens, the roof. This double heaven was also admitted by Eusebius of Caesaraea.

In the fifth, sixth, and seventh centuries science made no progress whatever. It was still taught that there were limits to the ocean. Thus Lactantius a.s.serted that there could not be inhabitants beyond the line of the tropics. This Father of the Church considered it a monstrous opinion that the earth is round, that the heavens turn about it, and that all parts of the earth are inhabited. "There are some people," he says, "so extravagant as to persuade themselves that there are men who have their heads downwards and their feet upwards; that all that lies down here is hung up there; that the trees and herbs grow downwards; and that the snow and hail fall upwards.... Those people who maintain such opinions do so for no other purpose than to amuse themselves by disputation, and to show their spirit; otherwise it would be easy to prove by invincible argument that it is impossible for the heavens to be underneath the earth." (Divine Inst.i.tution). Saint Augustin also, in his _City of G.o.d_, says: "There is no reason to believe in that fabulous hypothesis of the antipodes, that is to say, of men who inhabit the other side of the earth--where the sun rises when it sets with us, and who have their feet opposed to ours." ... "But even if it were demonstrated by any argument that the earth and world have a spherical form, it would be too absurd to pretend that any hardy voyagers, after having traversed the immensity of the ocean, had been able to reach that part of the world and there implant a detached branch of the primaeval human family."

In the same strain wrote S. Basil, S. Ambrose, S. Justin Martyr, S.

Chrysostom, Procopius of Gaza, Severia.n.u.s, Diodorus Bishop of Tarsus, and the greater number of the thinkers of that epoch.

Eusebius of Caesaraea was bold enough on one occasion to write in his Commentaries on the Psalms, that, "according to the opinion of some the earth is round;" but he draws back in another work from so rash an a.s.sertion. Even in the fifteenth century the monks of Salamanca and Alcala opposed the old arguments against the antipodes to all the theories of Columbus.

[Ill.u.s.tration: FIG. 35.--THE EARTH'S SHADOW.]

In the middle of the sixteenth century Gregory of Tours adopted also the opinion that the intertropical zone was uninhabitable, and, like other historians, he taught that the Nile came from the unknown land in the east, descended to the south, crossed the ocean which separated the antichthone from Africa, and then alone became: visible. The geographical and cosmographical ideas that were then prevalent may also be judged of by what S. Avitus, a Latin poet of the sixth century and nephew of the Emperor Flavius Avitus, says in his poem on the Creation, where he describes the terrestrial Paradise. "Beyond India," he writes, "_where the world commences_, where the confines of heaven and earth are joined, is an exalted asylum, inaccessible to mortals, and closed by eternal barriers, since the first sin was committed."

In a treatise on astronomy, published a little after this in 1581, by Apian and Gemma Frison, they very distinctly state their belief in a round earth, though they do not go into details of its surface. The argument is the old one from eclipses, but the figures they give in ill.u.s.tration are very amusing, with three or four men of the size of the moon disporting themselves on the earth's surface. As, however, they all have their feet to the globe representing the earth, and consequently have their feet in opposite directions at the antipodes, the idea is very clearly shown.

[Ill.u.s.tration: FIG. 36.]

"If," they say, "the earth were square, its shadow on the moon would be square also.

"If the earth were triangular, its shadow, during an eclipse of the moon, would also be triangular.

[Ill.u.s.tration: FIG. 37.]

"If the earth had six sides, its shadow would have the same figure.

[Ill.u.s.tration: FIG. 38.]

"Since, then, the shadow of the earth is round, it is a proof that the earth is round also."

This of course is one of the proofs that would be employed in the present day for the same purpose.

The most remarkable of all the fantastical systems, however, the _chef d'oeuvre_ of the cosmography of that age, was the famous system of the square earth, with solid walls for supporting the heavens. Its author was _Cosmas_, surnamed _Indicopleustes_ after his voyage to India and Ethiopia. He was at first a merchant, and afterwards a monk. He died in 550. His ma.n.u.script was ent.i.tled "Christian Topography," and was written in 535. It was with the object of refuting the opinions of those who gave a spherical form to the earth that Cosmas composed his work after the systems of the Church Fathers, and in opposition to the cosmography of the Gentiles. He reduced to a systematic form the opinions of the Fathers, and undertook to explain all the phenomena of the heavens in accordance with the Scriptures. In his first book he refutes the opinion of the sphericity of the earth, which he regarded as a heresy. In the second he expounds his own system, and the fifth to the ninth he devotes to the courses of the stars. This mongrel composition is a singular mixture of the doctrines of the Indians, Chaldeans, Greeks, and Christian Fathers.

With respect to his opponents he says, "There are on all sides vigorous attacks against the Church," and accuses them of misunderstanding Scripture, being misled by the eclipses of the sun and moon. He makes great fun of the idea of rain falling upwards, and yet accuses his opponents of making the earth at the same time the centre and the base of the universe. The zeal with which these pretended refutations are used proves, no doubt, that in the sixth century there were some men, more sensible and better instructed than others, who preserved the deposit of progress accomplished by the Grecian genius in the Alexandrian school, and defended the labours of Hipparchus and Ptolemy; while it is manifest that the greater number of their contemporaries kept the old Indian and Homeric traditions, which were easier to understand, and more accessible to the false witness of the senses, and not improved by combination with texts of Scripture misinterpreted. In fact, cosmographical science in the general opinion retrograded instead of advancing.

According to Cosmas and his map of the world, the habitable earth is a plane surface. But instead of being supposed, as in the time of Thales, to be a disc, he represented it in the form of a parallelogram, whose long sides are twice the shorter ones, so that man is on the earth like a bird in a cage. This parallelogram is surrounded by the ocean, which breaks in in four great gulfs, namely, the Mediterranean and Caspian seas, and the Persian and Arabian gulfs.

Beyond the ocean in every direction there exists another continent which cannot be reached by man, but of which one part was once inhabited by him before the Deluge. To the east, just as in other maps of the world, and in later systems, he placed the _Terrestrial Paradise_, and the four rivers that watered Eden, which come by subterranean channels to water the post-diluvian earth.

After the Fall, Adam was driven from Paradise; but he and his descendants remained on its coasts until the Deluge carried the ark of Noah to our present earth.

On the four outsides of the earth rise four perpendicular walls, which surround it, and join together at the top in a vault, the heavens forming the cupola of this singular edifice.

The world, according to Cosmas, was therefore a large oblong box, and it was divided into two parts; the first, the abode of men, reaches from the earth to the firmament, above which the stars accomplish their revolutions; there dwell the angels, who cannot go any higher. The second reaches upwards from the firmament to the upper vault, which crowns and terminates the world. On this firmament rest the waters of the heavens.

Cosmas justifies this system by declaring that, according to the doctrine of the Fathers and the Commentators on the Bible, the earth has the form of the Tabernacle that Moses erected in the desert; which was like an oblong box, twice as long as broad. But we may find other similarities,--for this land beyond the ocean recalls the Atlantic of the ancients, and the Mahomedans, and Orientals in general, say that the earth is surrounded by a high mountain, which is a similar idea to the walls of Cosmas.

[Ill.u.s.tration: FIG. 39.--THE COSMOGRAPHY OF COSMAS.]

"G.o.d," he says, "in creating the earth, rested it on nothing. The earth is therefore sustained by the power of G.o.d, the Creator of all things, supporting all things by the word of His power. If below the earth, or outside of it, anything existed, it would fall of its own accord. So G.o.d made the earth the base of the universe, and ordained that it should sustain itself by its own proper gravity."

After having made a great square box of the universe, it remained for him to explain the celestial phenomena, such as the succession of days and nights and the vicissitudes of the seasons.

[Ill.u.s.tration: FIG. 40.--THE SQUARE EARTH.]

This is the remarkable explanation he gives. He says that the earth, that is, the oblong table circ.u.mscribed on all sides by high walls, is divided into three parts; first the habitable earth, which occupies the middle; secondly, the ocean which surrounds this on all sides; and thirdly, another dry land which surrounds the ocean, terminated itself by these high walls on which the firmament rests. According to him the habitable earth is always higher as we go north, so that southern countries are always much lower than northern. For this reason, he says, the Tigris and Euphrates, which run towards the south, are much more rapid than the Nile, which runs northwards. At the extreme north there is a large conical mountain, behind which the sun, moon, planets, and comets all set. These stars never pa.s.s below the earth, they only pa.s.s behind this great mountain, which hides them for a longer or shorter time from our observation. According as the sun departs from or approaches the north, and consequently is lower or higher in the heavens, he disappears at a point nearer to or further from the base of the mountain, and so is behind it a longer or shorter time, whence the inequality of the days and nights, the vicissitudes of the seasons, eclipses, and other phenomena. This idea is not peculiar to Cosmas, for according to the Indians, the mountain of Someirat is in the centre of the earth, and when the sun appears to set, he is really only hiding behind this mountain.

His idea, too, of the manner in which the motions are performed is strange, but may be matched elsewhere. "All the stars are created," he says, "to regulate the days and nights, the months and the years, and they move, not at all by the motion of the heaven itself, but by the action of certain divine Beings, or _lampadoph.o.r.es_. G.o.d made the angels for His service, and He has charged some of them with the motion of the air, others with that of the sun, or the moon, or the other stars, and others again with the collecting of clouds and preparing the rain."