The science of discworld.., p.11
The Science of Discworld IV, page 11
Anders: Hey, don’t take that, it’s not scheduled.
Borman: You got a colour film, Jim?fn2
Anders: Hand me that roll of colour quick, will you!
The rest was a triumph of astronautical narrativium over managerial mission schedules.
Even though we now know the world is round, some diehards still refuse to accept the evidence. They ‘know’ that the Moon landings never happened; they were all faked in Hollywood studios. There is no question that this is possible now; movie-makers routinely use computer-generated imagery to create far more complicated things – among them the movie Apollo 13, made 25 years later, with highly realistic special effects. It’s doubtful that the imagery existed then, but of course secret guv’mint projects were concealing technological advances that they only made public much later … Though not, apparently, the relatively straightforward engineering technologies needed to put a man on the Moon. The theory that the Moon landings never happened makes perfect sense provided you think it is possible to sustain a global conspiracy ultimately involving millions of people, prominent among whom were the Russians, who were trying to beat the Americans to their lunar prize.
We don’t want to dissect conspiracy theories, or make any further attempt to convince you that Neil Armstrong and Buzz Aldrin really did land on the Moon in 1969, or, for that matter, that they didn’t. Instead, we want to examine one of the reasons why many people used to believe, and a fair number still believe, that the Earth is flat. Or some other shape that is not the nice round globe of the Earth we encounter in geography lessons.
This reason is the role of inference, as opposed to direct observation. Inferences are always open to interpretation, and there is often enough wiggle-room to permit apparently logical escape routes. Devotees of a flat Earth have used this wiggle-room to devise more-or-less plausible explanations for most of the usual arguments that it is round. Explaining away one piece of evidence for a round Earth often conflicts with explaining away some other piece of evidence, but in a point-scoring debate, few in the audience notice. We, your humble authors, actually have a totally convincing proof that the Earth is round, which does not depend on photos from space, but we’ll save it until the end of this chapter.
Before the 1960s, even the most technologically developed nations could not observe our planet from any vantage point higher than a plane could fly or a balloon could rise. In earlier times, the available evidence was limited to what a groundhog could observe with its own senses, and Pan narrans’s insatiable need to tell explanatory stories led to some imaginative proposals.
One of the earliest cosmologies that we know something about is that of ancient Egypt in the early dynastic period, around 3000 BC. It remained surprisingly unchanged for much of the next three millennia, although new elements came in from time to time and fashions changed. The basis for Egyptian cosmology seems to have been informal observations of natural phenomena, laced with imagination and thickly coated in religious imagery.
Egyptian thinking was strongly influenced by their natural coordinate system, which provided four very clear cardinal directions, each having a deep meaning. Egypt was the ‘black land’ sandwiched between two regions of ‘red land’: a thin fertile strip between wide deserts – though early on the desert areas were more like savannah than the arid expanses they are today. The Nile ran roughly from south to north, and the prevailing wind went the other way. The extent to which this axis was embedded in Egyptian thinking can be gauged from the hieroglyphs for south (a boat with its sails raised) and north (a boat with sails furled). The Sun – considered a god from predynastic times – rose in the east and set in the west.
In Egyptian mythology, the Earth was flat, with a sort-of square aspect because of the importance of the cardinal directions. It was associated with the god Geb. The goddess Nut formed a gigantic arch above the Earth, corresponding to the sky and the heavens. In between was the air god Shu. Various features of the night sky echoed those on the ground; in particular, the Milky Way, a bright, dramatic band of light in the night-time desert sky, corresponded to the Nile. Since the Sun disappeared from the sky in the west and reappeared in the east, it obviously passed under the Earth, through the solid body of the ground. During the night, the Sun god Ra battled with the demons and gods of the underworld, emerging victorious – or at least, as a survivor – each morning. Thanks, you appreciate, to the strenuous efforts and rituals of the priesthood.
Cosmology, you will recall, is the theory of the form of the universe, and it goes hand in hand with cosmogony, its origins. The Egyptians had several creation myths, originating in different regions of the country, and different myths were often combined in a mix-and-match way. A common element in most versions was mentioned earlier: the emergence of the Earth when the primal mound rose from the sea of chaos. The triangular shape of the pyramids is thought to represent, among other things, this primal mound. It has long been known that the Temple of Karnak in present-day Luxor had a ritual function as a representation of this primal mound, but there may be more to it than that. Recently archaeologist Angus Graham has been making geophysical surveys; using electrical resistivity tomography to detect the former course of the Nile through the silt it deposited, he has shown that in ancient times Karnak was located on an island in the middle of the Nile. As the annual floods receded, it would have re-enacted the emergence of the primal mound literally, not just symbolically.
Despite their religious interest in the night sky, the Egyptians seem not to have made a systematic study of astronomy for its own sake. For that, we must turn to another ancient culture: Babylon.
Babylon was one of a variety of civilisations in the Mesopotamian region, the fertile lands between the Tigris and Euphrates rivers. Today this area comprises Iraq, plus parts of Iran, Syria and Turkey. The city of Babylon was in central Mesopotamia, about 80 km south of present-day Baghdad.
During the Bronze Age, Mesopotamia included the empires of the Old Babylonians, Sumerians, Assyrians and Old Akkadians. The New Babylonian and New Akkadian empires followed in the Iron Age. The Sumerians invented cuneiform writing, triangular marks in clay made by a stick, around 3500 BC. They studied the heavens, were aware of the ‘wandering stars’ that we now call planets, and worshipped them as gods. An ancient Sumerian tablet refers to seven heavens and seven Earths.
Babylonian history is usually divided into two periods. The city-state of Babylon became a regional power when the sixth king, Hammurabi, took charge in 1792 BC, and the Old Babylonian period dates from then until about 625 BC. The New Babylonian period followed when Nabopolassar took control following a civil war triggered by the death of the Assyrian king Ashurbanipal. Many more cuneiform astronomical texts survive from the New period than from the Old, but there are enough Old Babylonian texts to demonstrate that their study of the heavens was systematic and organised. The Old Babylonian astronomers produced the first known star catalogue around 1200 BC, but many of the star names are Sumerian, so Sumerian astronomers must have made systematic studies of the heavens even earlier.
The Babylonians paved the way for modern astronomy, and possibly science as well. They observed the motions of celestial bodies, especially the planets, carefully and accurately. Then they looked for patterns, using mathematics to analyse the data. They discovered that many astronomical phenomena are periodic: they repeat at fairly regular intervals. There is a tablet that records how the amount of daylight changes over the year, and a series of tablets called the Enûma Anu Enlil contains the Venus Table of Ammisaduqa, a 21-year record of the motions of Venus and the earliest known discovery of periodic events in planetary motion. This tablet, made around 700 BC, is a copy of an older one, possibly from the early part of the Old Babylonian era.
The Babylonians were assiduous observers, but they had no great interest in theoretical explanations, and we know little about their cosmology. Tablets contain phrases such as ‘the circumference of heaven and earth’, suggesting that they imagined the Earth and the cosmos united in a single round object. The two components were of equal importance, and both revolved in circles. The Babylonians did not link their scientific studies of the planets to their religious views of the cosmos, and they seem not to have thought that the planets themselves move in circles.
After 400 BC, the centre of natural philosophy in the ancient world shifted to Greece. Philolaus, a member of the cult founded by Pythagoras, viewed the cosmos as a central fire, around which the Sun, Moon, Earth and planets all revolve in circles. We don’t notice the fire because it is hidden by the bulk of the Earth. Around 300 BC, Aristarchus of Samos came up with perhaps the first heliocentric cosmology, by the simple expedient of replacing the central fire by the Sun.
The novel idea that the Earth revolves around the Sun received a general thumbs-down from almost everyone else, including virtually all early Greek philosophers. Thales thought that a flat Earth floated on water. Anaximander thought it was a thick disc with a flat top. Anaximenes held that a flat Earth rode on air like the other celestial bodies. Xenophanes maintained that we lived on the flat top of a semi-infinite cylinder, extending downwards for ever (shades of ‘turtles all the way down’). Anaxagoras accepted that the Earth was flat, but Archelaus insisted it was saucer-shaped, which is why we don’t all see the Sun rising and setting at the same time.
Most ancient natural philosophers preferred the theories of Aristotle and Ptolemy, who placed the Earth where any sensible person naturally would: at the centre of things. Plutarch, in a work about the Man in the Moon – the apparent face formed by the darker regions – wrote that the head of the Stoics, Cleanthes, urged that Aristarchus should be called to account for lack of piety towards the gods. Why? Because he had dared to set ‘the hearth of the universe’ (Earth) in motion, and suggested that the heavens are static whereas the Earth rotates in ‘an oblique circle’ and – even worse – spins on its axis.
The heliocentric theory found favour with just one of Aristarchus’s successors, Seleucus of Seleucia, a hundred years later. By then, the Greeks were aware that the Earth is round, and Eratosthenes obtained a fairly accurate estimate of its size by observing the altitude of the midday Sun at Alexandria and Syene, present-day Aswan.
One variant Egyptian creation myth, the Ogdoad, replaces the primal mound by a cosmic egg. The Milky Way emerged from the ocean of chaos as a mound, associated with the goddess Hathor. A heavenly goose laid an egg on the mound, and inside it was Ra. Later, when the cult of the god Thoth rose to prominence, the goose mutated into an Ibis, an aspect of Thoth.
The image of the cosmos as an egg is common to many cultures. Typically either the universe or important deities come into existence when the egg hatches. The egg may be all that initially exists, or it may rest on a primal ocean. In Hindu mythology the Brahmanda Purana, a Sanskrit religious text, describes the cosmic egg at length. Here brahm means either ‘cosmos’ or ‘expanding’ and anda means ‘egg’. The Rig Veda refers to hiranyagarbha, ‘golden womb’. This floated in nothing until it fragmented into two parts, heaven and Earth. In Chinese Buddhism, Taoist monks told of a god called Pangu, born inside the cosmic egg, who broke it into heaven and Earth when he emerged. In Japanese mythology, a cosmic egg floats in a vast sea.
The Finnish epic Kalevala has a novel slant on creation, which it attributes to a duck that laid fragments of an egg on the knee of the air goddess Ilmatar:
One egg’s lower half transformed
And became the Earth below,
And its upper half transmuted
And became the sky above.
From the yolk the Sun was made,
Light of day to shine upon us;
From the white the Moon was made,
Light of night to gleam above us.
This extract exemplifies a common feature of many myths: they are human-centred. They explain the vast, enigmatic cosmos in terms of a familiar everyday object. An egg is round, like the Sun and the Moon. A living creature emerges from it, so the egg functions as a symbol for the source of all life. Crack one open, and you see two main colours: yellow yolk, and white. These just happen to be the colours of the Sun and the Moon. It is no wonder that images of this kind became so widespread. It just takes a certain combination of logic and mysticism, akin to the Egyptian association between the Sun god and a dung-beetle because both pushed a ball around.
The same combination is characteristic of Discworld narrativium; it is why so much on Discworld ‘makes sense’ even though it is about wizards, witches, trolls, vampires, elves and magic. All you need is a small amount of ‘suspension of disbelief’, as they say in science fiction circles. After that, everything is perfectly sensible. The main difference in ancient times was that there was very little disbelief to suspend. The universe-centred way of thinking was confined to a few deep thinkers in a few cultures.
As Greek civilisation became subsumed under the Romans, the main centres for the study of the natural world moved to Arabia, India, and China. Europe entered a lengthy period often referred to as the Dark Ages, a name that suggests (correctly) that we know very little about them, and also (incorrectly) that this is because nothing much happened on an intellectual level. There was a lot of scholarly effort, but most of it went into theology and rhetoric. What we now consider to be fledgling science struggled.
It is often claimed that in medieval times the Earth was thought to be a flat disc, but the evidence is ambiguous, except very early on. Around AD 350 St John Chrysostom deduced from the Bible that the Earth floated on the waters below the firmament of heaven, a view shared by St Athanasius at much the same time. In about AD 400 Bishop Severian of Gabala considered the Earth to be flat. Unusually, he also believed that the Sun did not travel beneath it during the hours of darkness, but instead nipped back round to the north, hidden from view. By 550 Cosmas Indicopleustes, an Egyptian monk, was doggedly following Egyptian tradition and offered theological arguments for a flat Earth, but with a new twist: the shape was that of a parallelogram surrounded by four oceans.
Many medieval writers definitely knew the world was round, although many believed that no humans lived on its underside, the antipodes. The important regions of the world formed a hemisphere, and in drawings and text it was easy to confuse this with a flat disc. A famous case is the seventh century AD Bishop Isidore of Seville, who wrote in his Etymologiae: ‘The mass of solid land is called round after the roundness of a circle, because it is like a wheel. Because of this, the Ocean flowing round it is contained in a circular limit, and it is divided into three parts, one part being called Asia, the second Europe, and the third Africa.’
At first sight, ‘round’ here seems to mean a flat disc, not a sphere. Maps of the period, known as T and O, T-O, O-T, or orbis terrarum maps, draw a round O outside a capital T. This divides the O into three parts: Asia above the horizontal stroke, Europe and Africa to the left and right of the vertical stroke. Rotate it through a right angle and it looks much like a modern map, though distorted. The oceans all join up and there is a complete ring of water surrounding the land. However, the map could be a projection into the plane of a hemisphere, and that seems to be the prevailing opinion among scholars today. On the other hand, the statement that the oceans are ‘contained in a circular limit’ is difficult to reconcile with a round Earth, especially since the reason is stated to be ‘it is like a wheel’. Do the scholars protest too much?
Be that as it may, there are many references from early Christian times indicating knowledge of a round Earth, but that raised a more difficult theological issue. A round Earth requires the existence of antipodal regions, diametrically opposite to the geographical regions that were then known to Europeans. The existence of these regions wasn’t a problem, but there was general disbelief that they were, or could be, inhabited. The objection was not that people would fall off, but that no one had been there to see whether there was any land – and if there were, whether there were people. It was a perfectly scientific objection: the problem was lack of evidence. Shortly after the sack of Rome in 410, Saint Augustine of Hippo addressed the issue in his City of God:
… as to the fable that there are Antipodes, that is to say, men on the opposite side of the Earth … that is on no ground credible … Although it be supposed or scientifically demonstrated that the world is of a round and spherical form, yet it does not follow that the other side of the Earth is bare of water; nor even, though it be bare, does it immediately follow that it is peopled … Since these people would have to be descended from Adam, they would have had to travel to the other side of the Earth at some point … It is too absurd to say, that some men might have taken ship and traversed the whole wide ocean, and crossed from this side of the world to the other, and that thus even the inhabitants of that distant region are descended from that one first man.
Full marks for geography, then.
The history of flat versus round Earth is complex, open to many divergent interpretations, and littered with myths. A common one is that Columbus had to overcome a widespread belief that the Earth was flat in order to persuade the Spanish royal family to allow him to try to sail westwards to India. Actually, the main obstacles were twofold: the correct belief that the round Earth was too big for this to work according to Columbus’s schedule, and the cost.
Columbus fudged the figures.
Educated people seriously began to wonder whether the Earth really might be flat, or at least not the conventional spheroid, in the Victorian era, around 1850. Paradoxically, the new spirit of scientific enquiry was encouraging some people to question well-established observations of the shape of our planet. It is worth remembering that this was also a period when belief in the spirit world flourished. It wasn’t just Biblical creation that was coming under fire from science. Although no reputable scientists seem to have reverted to believing in a flat Earth, several prominent figures in society did. What motivated them was often a fundamentalist attitude to the Bible, coupled with naive or idiosyncratic interpretations of its contents.
