Star trails over the Yepun telescope in Chile circle the Celestial South Pole.
The celestial poles remain useful theoretical concepts today, referring to the points where the Earth’s axis of rotation, extended out arbitrarily far, meets an imaginary sphere on which the distant stars appear to sit. If you are standing at either of the geographic poles, the corresponding celestial pole should be directly above your head, staying still as the rest of the stars seem to circle around it. However, on a long timescale this point also changes position relative to the stars: the Earth’s axis of rotation precesses – it wobbles like a top – causing the Celestial South Pole to move in a circle over a period of nearly 26,000 years. This phenomenon (distinct from the polar motion described earlier) is caused by the Earth’s ‘squashed sphere’ shape and the gravitational pull of other bodies in the solar system.
At present, the Celestial North Pole is located within the constellation of the Little Bear (Ursa Minor). The constellation’s brightest star, once known as Cynosura, is now called Polaris, the Pole Star (or ‘lodestar’). It has not always been the Pole Star, however: the Celestial Pole moves away from and towards different stars during its 26,000-year cycle. Since late antiquity, Polaris has been close enough to the Celestial North Pole to act as a beacon for navigators, and has been moving ever closer in the period since. It will reach its nearest point around AD 2100, after which its distance from the Celestial Pole will start to increase, and eventually another star will take on its role. The Celestial South Pole has no conveniently bright stellar guide of this kind to mark its whereabouts: it has to make do with a dim constellation, and its designated pole star – Sigma Octantis or Polaris Australis – is not easy to see even when the weather is clear.
Earth’s tilted axis of rotation is responsible for the diurnal extremes in the polar regions. The axis ‘points’ in either direction towards the celestial poles.
Most commonly confused with the geographic poles are the magnetic poles: the two points where the Earth’s magnetic field lines are perpendicular to its surface. A compass needle that is free to move vertically should point directly down at the Magnetic North Pole and up at the South; the magnetic poles are correspondingly referred to as the ‘dip’ poles. The existence of these planetary magnetic poles was first postulated to explain the behaviour of magnetic materials. Early forms of the compass were employed by the Chinese by the first century AD and by the twelfth century they had entered into usage by Europeans. There were various speculations about why the lodestones used in these compasses aligned themselves along a north–south line, including a postulated enormous lodestone at the Geographical North Pole or special properties of the Pole Star itself. A French scholar known as Petrus Peregrinus (‘the wanderer’) in the later thirteenth century first noticed the polarity of the lodestone, likening its two poles to the celestial northern and southern poles of the cosmos.12
At this stage the north indicated by the stars (what has since been called ‘true north’) and the north indicated by a compass (‘magnetic north’) were thought to be one and the same. In fact, in most locations, a compass needle deviates from the direction of the North Geographic Pole by a significant angle, meaning that there is a considerable distance between true and magnetic north; the same goes for the south. However, this phenomenon, known as ‘declination’, was recognized only slowly over the next few centuries. The concept that the Earth has its own magnetic field – that it is itself, in effect, a giant magnet – was first suggested in 1600 by William Gilbert, physician to Elizabeth I. In Gilbert’s model the Earth’s magnetic and rotational axes are aligned, putting the magnetic and geographic poles in the same place. Gilbert knew about declination but explained it by suggesting that the magnetism of rocks in the continents caused local deviations of the compass needle. Just a few years later his idea was modified, so that the magnetic axis was now tilted away from the rotational one, placing the magnetic poles well apart from their geographic counterparts, although still in high latitudes. The theory – which essentially postulates an enormous tilted bar magnet (a magnetic ‘dipole’) sitting at the planet’s centre – did not, however, explain observations particularly well. The patterns of declination were far too complex to fit this simple model.13
To make matters more complex, it was increasingly recognized that declination – and hence the relative position of the geographic and magnetic poles – varied over time. This suggested that the magnetic poles, like Petrus Peregrinus, were wanderers. Scientists continued to suggest explanations: Edmond Halley (of comet fame) in the late seventeenth century postulated the existence of four magnetic poles – one pair in the north, the other in the south. Halley speculated that the Earth contained within itself another sphere: two of the magnetic poles were produced by the outer sphere of the Earth and two by his speculative inner sphere. The two spheres rotated at different speeds, in Halley’s model, explaining the way that the deviation of the compass needle from true north varied over time. There could, he suggested, be a series of nested shells inside the Earth; he even raised the possibility of the planet’s interior being inhabited.14
As understandings of both magnetism and the Earth’s interior progressed over the following three centuries, increasingly precise theories were developed. The tilted, centred bar-magnet model is now understood as a very roughly approximate version of the actual situation. The term ‘geomagnetic pole’ is applied to the two points, north and south, where the field lines of this imaginary bar magnet would be perpendicular to the Earth’s surface. In actuality, however, the Earth’s magnetic field is a dynamic system with some components that act like big bar magnets and others that do not (‘dipole’ and ‘non-dipole’). The movement of molten metal within Earth’s mantle accounts for the wandering of the magnetic poles, and the influence of electrically charged particles from the sun produces an additional daily, roughly elliptical motion. These particles also create auroral effects (the northern and southern ‘lights’). There are, however, only two magnetic poles – points where the Earth’s magnetic field is perpendicular to its surface – which are the net product of this complex system. Unlike the geomagnetic poles, the northern and southern magnetic poles are not directly opposite each other, nor do they move at the same rate.
For nineteenth-century scientists and navigators, a practical question remained: where on Earth are the magnetic poles? What are their coordinates of latitude and longitude? Unsurprisingly, the Magnetic North Pole was the first point of focus: British naval expeditions searching for the Northwest Passage also took detailed magnetic observations. In 1831 John Ross captained an expedition during which a small party led by his nephew James Clark Ross finally reached the spot. Like Amundsen, Ross knew he was not technically on the precise Pole, but rather very close to it: ‘if popular conversation’, he later wrote, ‘gives to this voyage the credit of having placed its flag on the very point, on the summit of that mysterious pole which it perhaps views as a visible and tangible reality, it can now correct itself as it may please’.15 Neither was he necessarily the first person to reach its immediate vicinity, since he took his observations from conveniently located abandoned Inuit huts. Nonetheless, he was justifiably happy with his scientific achievement and, fewer than ten years later, he was leading an expedition in the Antarctic that hoped to reach the Magnetic South Pole.
This task was close to impossible at the time, as Ross discovered when he fixed the Pole’s location: his goal was within the Antarctic continent, unreachable by ship. When its attainment was eventually announced about 70 years later, problems with the accuracy of its location still occurred: a team, including the Australian explorer and scientist Douglas Mawson, thought they had reached the Magnetic South Pole in early 1909, only to discover years later, after their figures had been analysed by experts, that technically they hadn’t. The Magnetic South Pole can now be found in the ocean off the Antarctic coast, around 1,400 km (900 miles) from its position in Ross’s time, and nearly 2,900 km (1,8
00 miles) from the Geographic South Pole.16 It is currently drifting northwest (towards Australia) at about 10–15 km (6–9 miles) per year – a sluggish rate compared to its northern cousin, which has been moving in a similar direction (from Canada towards Siberia) at up to 60 km (37 miles) per year.17
Magnetic South Pole movement based on magnetic field models, 1590–2010.
Ironically the Magnetic North Pole is technically a south pole of the Earth’s magnetic field, and vice versa. Historically, the north pole of a magnet was the end that pointed north; but, because opposite poles attract, it was a south magnetic pole in the Arctic pulling the compass needle’s north end. However, this has not always been the case: over geological timescales, the polarity of the Earth’s geomagnetic field can shift, so that 800,000 years ago the Magnetic South Pole would indeed have been a magnetic south pole. While the process of this ‘flip’ is occurring – it can take up to 10,000 years – the geomagnetic system is in a disordered state, and at times there may be more than one north and south magnetic pole. Many such reversals have occurred in Earth’s geological history.
There is yet another South Pole to be canvassed – a pole by name more than nature. A ‘pole of inaccessibility’ is the term applied to a place that is the most difficult of its kind to reach. In continents this is conventionally taken as the point furthest from the coast, on average; in oceans it is the furthest point from the surrounding lands. The South Pole of Inaccessibility (sometimes qualified as ‘Relative Inaccessibility’ or ‘Maximum Inaccessibility’) is thus the point in Antarctica that is on average furthest from the continent’s coast. Since locating the coastline has not itself always been straightforward, and depends on whether ice shelves are included, it is possible to find several different estimates of its location; 85°S, 65°E is commonly cited these days. The Geographic South Pole is not, as is sometimes assumed, in the centre of the continent – even roughly. It lies many hundreds of miles from the Pole of Inaccessibility, however the latter is estimated.
The ‘pole of cold’ is another term that uses ‘pole’ synonymously with ‘extreme’. It refers either to the point in a continent with the coldest mean annual temperature or the point with the lowest individual recorded temperature. Antarctica can boast the coldest pole of cold in both interpretations: the lowest recorded air temperature in the world –89.2°C (–128.6°F) occurred at the Russian base Vostok; mean temperatures are slightly colder at Dome A, which is also the region of highest altitude in the continent at just over 4 km (2.5 miles). Both are significantly colder than the lower Geographic South Pole.
Satellite image of Antarctica generated from NASA’s Visible Earth Blue Marble project.
Just one South Pole remains: Antarctica itself. Anyone picking up this book could be forgiven for assuming that its subject is the south polar region, broadly speaking – the whole Antarctic continent and its surrounding seas. ‘I write to enquire whether you will do me the favour – and honour – of joining my expedition to the South Pole’: so runs a letter from Mawson to a potential expedition member,18 but the Australian explorer had no intention of going to the Geographic Pole, and had in fact refused an invitation from Scott to do so. He planned to (and did) base his expedition on the coast of East Antarctica, barely within the Antarctic Circle, half a continent away from Scott’s destination. In his letter, however, Mawson uses ‘South Pole’ and ‘Antarctica’ interchangeably, as many people still do.19
Inasmuch as my subject of interest lies within the southernmost continent, this is a book about Antarctica. But my main focus is that strange point in Antarctica’s interior – a point that is symbolically the most remote of earthly locations and simultaneously a centre to which explorers, adventurers, scientists and now even tourists are inexorably drawn. Despite the evident absurdity of making an expensive and (for those who still choose to travel overland) arduous journey to an extremely inhospitable point on a comparatively featureless ice plateau, the lure remains. There is something remarkable in standing at (to borrow T. S. Eliot’s phrase) a ‘still point of the turning world’:
Except for the point, the still point,
There would be no dance, and there is only the dance.
I can only say, there we have been: but I cannot say where.20
2 Maps and Mythologies
Open any standard atlas and the first map of the world that you see will almost certainly place the equatorial region near its centre, the Arctic at the top and the Antarctic at the bottom. The equator itself is rarely in the exact middle of the map; more often it is someway down the bottom half of the page, so that the lion’s share of space is given to the northern hemisphere, and the Antarctic coast pokes out from the lower edge of the frame, if it is there at all. One researcher, flying with the Australian airline Qantas in the early twenty-first century, was taken aback to find that the map provided in the in-flight magazine, despite giving considerable detail about remote regions where the airline does not fly (such as Arctic islands), overlooked the entire continent to Australia’s south, although its aircraft are regularly chartered for flights over the region.1 In many common cartographical projections the Antarctic (and Arctic) are distorted more than other regions. In the Mercator projection the poles become horizontal lines, impossibly smeared out along the borders of the map. When it does appear, then, the ‘other Pole’ is often treated to the double indignity of being grossly attenuated and ‘at the bottom’.
The South Pole has not always been the underdog. In On the Heavens Aristotle refers to the invisible southern celestial pole as ‘the one on top’ (although in his Meteorologica it is the north that has this position).2 Chinese compasses were originally oriented to the south rather than the north.3 Early Arabic maps tended to be south-oriented, and influenced maps produced in Italy. Medieval mappaemundi, most of which are constrained to the known parts of the world and so do not include the space where Antarctica would be, normally have the East, the site of Jerusalem, at the top, although some, including one of the most famous, by Fra Mauro, are south-oriented.4
A 1931 pictorial map of the world using the Mercator projection.
As Western cartography began to burgeon alongside exploration and trade during the Renaissance, however, the main influence was Ptolemy’s Geographia, a treatise from the second century AD which had only recently been revived in Europe; and Ptolemy placed the north at the top of the map. Drawing on earlier assumptions that a large southern hemisphere landmass must exist to balance the known lands of the north symmetrically, he also posited an enormous continent that he termed Terra Incognita, joined to Africa and India and enclosing the Indian Ocean to the south. Another influential figure was the fifth-century AD Roman philosopher Macrobius, whose ‘zonal’ or ‘climatic’ world map was reproduced in numerous medieval manuscripts (sometimes with a south orientation). Following a theory that reached back many centuries to the Greek philosopher Parmenides, Macrobius divided the world into five climatic zones, with the far north and south both frigid, the equatorial region torrid and the two zones in-between temperate. Maps based on Macrobius’ ideas show a large, cold, southern continent separated from northern lands by an ocean.
From the fifteenth century to the eighteenth, representations of the south polar region on European maps are characterized by several contrasting traditions, sometimes incorporating and sometimes ignoring the accumulating but fragmentary information coming back from sea voyages into comparatively high southern latitudes. One line of cartographical speculation was that the far south was simply ocean; another that it was a sea of ice which covered the Pole, with a large island nearby. A third school of thought proposed a ring-shaped continent surrounding a polar sea, and a fourth – the most enduring – maintained a belief in Ptolemy’s Terra Incognita.5 On some maps, the southern continent was enormous in extent, extending up as far as New Guinea. An early example of the tradition is Oronce Finé’s world map of 1531, drawn using a double cordiform (heart-shaped) projection that foregrounds the polar region
s: its Terra Australis (this was the first use of the term on a map) is confidently described (in Latin) as ‘recently discovered but not yet fully known’.6 The continent reaches from the Pole up to Tierra del Fuego, which is the land ‘recently discovered’ (by Magellan), and is nine times larger than the Antarctica known today.7
This world map from Francesco Berlinghieri’s edition of Ptolemy’s Geographia (1482) shows a sprawling Terra Incognita and a landlocked Indian Ocean.
South Pole Page 2
