by Bill Bryson
Throughout the twentieth century, the Earth sciences have increasingly treated their subject in terms of cycles, whether the oscillations of the atmosphere or the circulation of the core. The past fifty years have seen acceptance of the Milankovitch cycles – subtle variations in the Earth’s orbit and attitude – as the causal framework for the ice ages, with ice sheets waxing and waning to their heavenly rhythms. They have seen Earth’s magnetic field revealed as a creature that rocks back and forth from North to South, the plaything of dynamic currents circulating in the planet’s core. Most fundamental of all, they have seen the uncovering of the great three-dimensional cycles of plate tectonics, in which the slow and mighty overturning convection of the mantle is coupled to the opening and closing of oceans, the merging and scattering of continents.
In the 1950s Victor Goldschmidt, frequently described as the father of modern geochemistry, put cycles at the centre of that discipline’s study of the Earth, defining it in terms of ‘the circulation of elements in nature’. Both geochemistry and biogeochemistry remain studies of cycles – in the latter case, quite intimate ones: the carbon dioxide given back to the plants with each animal breath, the nitrogen returned to the world in each drop of urine. The ‘Earth Systems Science’ that emerged in the 1980s and 1990s, often informed by Lovelock’s Gaia, assembled ideas from all these disciplines and subdisciplines into further cycles, cycles made not of matter, but of cause and effect: feedback loops that could stabilise the Earth system or force it into flip-flop oscillations.
Like the components of an astrolabe, the cycles of the Earth system seem to nestle within each other, arranged not by size – they are all, in the end, the size of the planet – but by intimacy and speed, reaching out from the food in our bellies and the wind on our faces to the vastest of vegetable empires and the yet slower, greater mineral realm. Our sweat, once evaporated, spends only days in the sky before falling back as rain. The carbon dioxide we breathe out may be in the air for decades before being eaten up by plants, or take refuge in the oceans for millennia before resurfacing. Other cycles are slower still. While nitrogen compounds can be pumped from sea to sky by microbes, once phosphorus makes its way from soil to the sea it has no easy way back to the atmosphere, and must wait millions of years before, incorporated into sediments, it is lifted up into new mountains to fertilise the soils again. The cycles interpenetrate in such ways all the time, passing through each other in a daunting clockwork of teeth and differentials, their nesting anything but neat, their gearing prone to glitches.
Such a vast machinery seems more daunting to the imagination than a blue marble in space. But while what is circulating, and how it circulates, can be hard and complex questions to fathom, the idea that the world is endlessly recycling itself is an easy perception to train oneself into. The growth of a plant, or the erosion of a gully, are easily seen. And to see a plant grow armed with the knowledge that it does so out of thin air – that is, after all, where the carbon that makes up most of its mass comes from – is to realise that something else must be restoring that nutritive goodness to the atmosphere. To see water cutting into highland rock and washing soil downstream is to realise that, if this is going to go on indefinitely, there must be some way of making new highlands to replace those endlessly whittled away. When Joseph Priestley and James Hutton first had these insights in the eighteenth century they were hard-won breakthroughs. But once known, they become compellingly obvious; it is hard to see how things could be otherwise in a world that endures.
This dynamic image of the Earth is a corollary of one of the most striking aspects of that timeless, static image of the Earth in space: its limits. The Earth is, in material terms, isolated. Very little arrives (those asteroid impacts are few and far between), and only a whisper of gas escapes. Everything else must be endlessly recycled: and so it is. The rain becomes the ocean and the ocean becomes the rain, the mountains are ground down to cover the sea-floors with silt, ancient silts rise up to make new mountains. Nothing stays the same, and yet the system, mostly, persists. Everything is in flux, but nothing is at risk.
And this flux illustrates perhaps the most useful sense of that unhappy phrase, the ‘balance of nature’. Nature was not designed to balance, any more than it was designed for anything else. It does not have preferred states with which people meddle at their peril, or that carry some sort of moral weight, or to which it wishes necessarily to be restored. It is precisely to the extent that the Earth is off balance that it works; its rolling cycles are like wheels on slopes. But if there is no static equilibrium, there is balance of another sort – a balance like that of a bank account, its debits and credits constrained always to match over time. For every output there must be an input. Any earthly process not looped back on itself in some way, anything that does not carry the seeds of its own recreation, will either be remarkably slow, or will have run its course long ago, or only just have started. Otherwise it will simply run out of credit.
The existence of the Earth’s great recycling can thus be explained by the fact that, in terms of material, it is a closed system. But to explain it this way is immediately to need something more; a source of energy that comes from beyond the system that it powers, and provides the slopes down which the wheels roll. There is work going on in those cycles – pumping, breathing, lifting, grinding – and work can only be done where there are flows of energy. The second law of thermodynamics, the bane of the perpetual-motion-machine designer, means that such flows of energy cannot, themselves, be recycled; the same energy cannot do the same work twice. If work is to be done continuously, fresh energy needs to be provided continuously, and old energy – waste heat – needs to be disposed of. A world closed in one way must be open in another. The Earth depends on there being a beyond.
The Earth’s circulating carbon atoms and continents and other constituents depend on three streams of energy from the beyond – and, in the case of the heat of the Earth’s interior, from the before as well. Almost all the energy that now comes from within the Earth was put there, in one form or another, at the time of its creation (a tiny amount is now added by the flexing of the planet under the tides of Moon and Sun, but it is the merest smidgen). One stream of energy stems simply from the immense store of heat generated when a planet’s worth of gas and dust fell in upon itself, the ingredients smashing into each other in ever larger pieces and at ever greater speeds as the process went on. The Earth thus started off with vast supplies of heat inside it, and a rocky planet, like any other rock, takes a long time to cool down. Stones in a campfire may still be hot the morning after; a stone the size of the Earth can hold heat for billions of years.
Then there is the heat generated since the Earth’s creation from energy stored up long before. The chemical elements on Earth that are heavier than helium were created in stars that burned out before the Sun and Earth were born, the vast pressures in their hearts squeezing hydrogen into carbon, silicon, oxygen, nitrogen and iron. When such stellar furnaces explode into supernovae, the energies unleashed become great enough to forge elements even heavier. In the case of elements such as uranium and thorium, those great energies will, in time, leak out. The radioactive elements gathered into the Earth at the time of its creation have steadily meted out the supernova energies stored within them. Thus energy from dying stars helps drive the great internal convection currents which move tectonic plates.
Both these streams of energy, though, are small compared to that which rains down from above. The most easily overlooked and perhaps most fundamental feature of the Apollo 17 picture of the Earth is its brilliant over-the-shoulder illumination. Yes, the Earth floats in pitch-black space – but it floats in sunlight, too. It floats in a torrent of the stuff. The upward flow of ancient heat to the Earth’s surface is measured in tens of milliwatts per square metre; the flow from the Sun above is measured in hundreds of watts per square metre. This is the energy that warms the surface and the sky above it, that drives the circulation of atmosphere and
ocean. This is the energy of cloud and rain, of sand dune and hurricane. This is the energy which powers the cycles of the biosphere. When plants fix carbon, when bacteria fix nitrogen, when plankton release sulphur from sea-water back into the sky, they do so, directly or indirectly, with solar energy. It is the energy of forest fire and Sunday lunch.
These solar-powered cycles of the biosphere are the ones in which humans are most intimately involved, both as beneficiaries and as rearrangers. Since the development of artificial fertilisers, the nitrogen cycle has come under human control to a remarkable extent, though not in a centralised way. The plough, the field, the roadworks and the building site have increased the rate of erosion far beyond its geological average; the rate at which water flows out of rivers depends on farmers and dam-makers.
And then there is the rate at which ancient sunlight stored in fossil form is used to drive the engines of industry and civilisation. The amount of energy actually liberated in the burning of these fossil fuels is tiny by planetary scales – ten terawatts or so a year, not that much more than the nugatory contribution made by the tides. But the side effects are huge. The carbon dioxide liberated in the burning renders the atmosphere less transparent to the flow of outgoing heat; with the flow thwarted in this way, the temperature at the surface goes up. The resultant warming is, in terms of energy flows, about one hundred times larger than the amount of energy released by the fossil fuels.
This great short-circuiting of the geological carbon cycle, though, reveals one of the strengths of seeing the Earth in terms of its turning dynamics. In the purely human realm, cyclic theories of history tend to engender a feeling of hopelessness – the cycle will roll on, regardless. But, perhaps surprisingly, a view of the Earth that focuses on its relentless cycles and the flows of energy that drive them can be empowering. It is a view of the planet in which we are already involved, for good or ill, and to which we can make changes for better or for worse. These are cycles we can use. The Earth seen as a bauble in space is what it is – just a sight, not an experience. The only injunction that is possible faced with that gorgeous globe is ‘sustain’. Sustain the gaze; sustain the object. The Earth as an encompassing nest of cycles is a world which we are always already involved with, a Land-art world in which intervention is of the essence. This way of seeing makes things at once more frightening – this is the lived environment of wind in the face and water in the tap at risk, not some idealised representation – and more tractable.
Recognising the openness of the Earth system and the flows of energy that power it offers the clearest way of seeing the solution to the current global environmental crisis. If the manner in which humans currently reap their energy from fossil fuels ties the flow of energy to the material flow of the carbon cycle in a deeply damaging way, we must simply find other flows to tap. Energy is flowing through the winds, in the currents of the oceans, in the rivers, in the growing of the grass. It flows out of the ground and down from the sky. Geothermal plants can speed the flow of heat from the depths; kites in the stratosphere can harvest the endlessly circulating jet streams; mirrors in the deserts can drive turbines with sunshine. There is energy of all sorts flowing through our world; it is not hard to imagine new ways in which that energy can do the work of humanity, new ways to align our needs and the planet’s behaviours. And if that capacity for work is harnessed, many other problems can be solved. The carbon cycle could be expanded, the biosphere’s capacity for drawing carbon dioxide from the air increased and the greenhouse effect thus diminished. Other waste can be recycled, too, and material resources thus renewed; with a great enough flow of energy from beyond, any closed system can sustain itself with recycling.
The Earth of cycles can hardly be the icon that Apollo’s Earth has become; it is more a hum than a sight. But it is a valuable way of thinking of the Earth from inside, of seeing the human and the inhuman as close, interdependent, even indistinguishable. It is an experience that can be taught and shared, and even felt. Stretching from iron core to encompassing cosmos, it has the depth and scale to provide a sublime thrill of its own. True, it offers no gestalt vision to the objective eye. But it can be animated, if you have a mind to. When next you see a picture of the blue marble in space, imagine its clouds coming to life, their whorls beginning to turn like turbine blades. And as you see the scope of the planet’s circulation in your mind’s eye, let your other mental senses in on the act, too; feel the raw heat of the Sun on the back of your neck as it powers the vision in front of you. Embed the portrait in a vision of process. Turn it into part of something – of a solar system, of an act of the imagination, of a future.
With the right imagination, the world of cycles and the world of the astronomer’s gaze can be made to mesh. As mentioned before, the seemingly isolated Earth does in fact have an environment, discovered by astronomy in the abstract, realised as relevant only long after the fact. This environment is the source of the flows of energy that drive the workings of the Earth; it can also be coupled to those workings more directly. The revolutions of the Earth and sky are loosely linked. Orbital cycles carefully calculated by astronomers with no earthly agenda turn out to drive the ice ages. Objects in space affect, and even collide with, the planet from which we watch them. For a long time the possibility of such impacts was deemed of no practical importance, but now it is accepted that they have had great geological significance, and that they merit a certain continued vigilance. As a result of this, 2008 saw the first case of an object on a collision course with the Earth being discovered at an observatory, monitored at the appointed time as a fiery meteor in the sky, and later gathered up in fragments from the ground to which it fell. Asteroid 2008 TC3 was in most ways a small and inconsequential object, but it cut through an important disciplinary distinction. The world of cycles in which we live is not limited to the ball of rock on which we sit; objects elsewhere matter too, and to some extent this must change the way we think about the sky.
And then there is the question of looking further off. Pull back from the Earth just as far as the Moon, and the blue marble loses its features, continents become hard to see, clouds swamping all other detail. From Mars you would need binoculars to even see it had a disc, from Jupiter you would be hard put to make it out with the naked eye. From six billion kilometres away, the greatest range at which the Earth has yet been photographed, Voyager 1’s powerful camera saw it as only the palest of blue dots. Yet space scientists now speak of seeing, and learning about, Earth-like planets around other stars.
No telescope currently conceivable could actually produce pictures of such planets as discs in space. But it is possible to look for their cycles, their rhythms. Already such planets are inferred from the way their orbits produce sympathetic wobbles in the movement of their parent’s stars, or the regular ways that they pass between those stars and earthly observers. When they become discernible in their own right, less astronomical signs of cycling will be looked for – hints of weather from changes in brightness caused by daily movements of cloud, traces of seasonality as colours shift over the year. Most vital of all, signs of the cycling biosphere will be sought out. As Lovelock pointed out in the late 1960s, biogeochemical cycling has pushed the Earth’s atmosphere far from chemical equilibrium. Such disequilibrium may yet, possibly even soon, be seen in the light of planets round other stars. Understanding the Earth’s endless recycling sets the stage for measuring the Earthliness of distant specks, and for reading life into a point of light that has no features that could ever be gazed upon.
The Earth is still a beautiful ball floating in space. The Apollo 17 camera did not lie. But by seeming to show everything, that portrait made it too easy to ignore the dynamism its stillness could not show. The Earth is not something put before us, or left behind us. It is around us and within us, turning on itself in every way it can as energy flows through it from the depths of the past and the fires of the Sun. It is not just a spaceship carrying a crew. It is a world, and now aware.
&nbs
p; 1 George Orwell, ‘As I please’, Tribune, 27 December 1946. In Sonia Orwell and Ian Angus (eds), Collected Essays, Journalism and Letters of George Orwell, vol. 4: In Front of Your Nose 1945–1950 (London, Secker and Warburg, 1968).
2James Lovelock, Gaia: A New Look at Life on Earth (Oxford, Oxford University Press, 1979).
3 Tim Ingold, ‘Globes and Spheres: The Topology of Environmentalism’ in Kay Milton (ed.), Environmentalism: The View from Anthropology (London, Routledge, 1993).
4 John Grande, ‘Real Living Art: A Conversation with David Nash’, Sculpture, 20:10 (December 2001).
18 MAGGIE GEE
BEYOND ENDING: LOOKING INTO THE VOID
Maggie Gee has written eleven novels, a short story collection and a memoir, My Animal Life. Her novels include The Burning Book, Light Years, Where Are the Snows, The Ice People, The White Family, The Flood, My Cleaner and most recently My Driver. She was chair of the Royal Society of Literature from 2004–2008 and is now a vice-president.
SCIENCE REVEALS NEW WORLDS, BUT MAY ALSO BRING NEWS OF THE END OF THE WORLD. THE IDEA HAS A CURIOUS APPEAL, FOR SCIENTISTS AND WRITERS ALIKE, AS MAGGIE GEE EXPLORES.
Entire nations are uninhabitable. Entire nations have been wiped out. And land cracks and peels in some areas of the globe. In others, deluges of flood water ravage the earth. Welcome to a world six degrees warmer. Welcome to our future. – From the jacket copy of Mark Lynas’ Six Degrees, 2007
I
Human beings fear endings, but also crave them. The forbidden thrill of the death-wish stalks many imagined apocalypses, literary, Christian, scientific and filmic; disaster movies do good box office because, in the safety of the present, we can look at the unimaginably terrifying future, and experience the excitement without being annihilated. But our current perils are not just imaginary. Martin Rees’ book, Our Final Century, suggests that we really are living in dangerous times. In addition to the usual risks to life on Earth, like asteroid impacts, volcanic eruptions and epidemics, twenty-first-century humans have to live with the incidental risks of new technologies – for example, ‘bioerror or bioterror’, rogue nanoreplicators, mishaps to nuclear power stations – and with the threat of rapidly rising global temperatures due to carbon emissions. So how do twentieth- and twenty-first-century writers and scientists address their sense of an ending?