Stephen Baxter: The offical web site.
The Works of Stephen Baxter
White Tetrahedron
Stephen Baxter: Creation Node (Book)
Creation Node

21 September 2023

Stephen Baxter: The Thousand Earths (Book)
The Thousand Earths

29 September 2022

Stephen Baxter: Galaxias (Book)

21 October 2021

Stephen Baxter: World Engines: Creator (Book)
World Engines: Creator

20 August 2020

Stephen Baxter: World Engines: Destroyer (Book)
World Engines: Destroyer

19 September 2019

Stephen Baxter: Xeelee: Redemption (Book)
Xeelee: Redemption

23 August 2018

Stephen Baxter: Raft: SF Masterworks Edition (Book)
Raft: SF Masterworks Edition

12 July 2018

Stephen Baxter: The Spacetime Pit Plus Two (Book)
The Spacetime Pit Plus Two

Infinity Plus
5 January 2018

Stephen Baxter: Xeelee: Vengence (Book)
Xeelee: Vengence

15 June 2017

Stephen Baxter: The Massacre of Mankind (Book)
The Massacre of Mankind

19 January 2017

Stephen Baxter: Obelisk (Book)

18 August 2016

Terry Pratchett & Stephen Baxter: The Long Cosmos (Book)
The Long Cosmos

30 June 2016

Stephen Baxter & Alastair Reynolds: The Medusa Chronicles (Book)
The Medusa Chronicles

19 May 2016

Stephen Baxter: Xeelee: Endurance
Xeelee: Endurance

Orion Fiction
17 September 2015

Terry Pratchett & Stephen Baxter: The Long Utopia
The Long Utopia

19 June 2015

Stephen Baxter: Ultima

27 November 2014

Terry Pratchett & Stephen Baxter: The Long Mars
The Long Mars

19 June 2014

Stephen Baxter: proxima

19 September 2013

Stephen Baxter: Universes

PS Publishing
29 March 2013

Stephen Baxter: The Long War
The Long War

20 June 2013

Stephen Baxter: The Long Earth
The Long Earth

21st June 2012

Stephen Baxter: Doctor Who : The Wheel of Ice
Doctor Who : The Wheel of Ice

BBC Books
16th August 2012

Stephen Baxter: The Science of Avatar
The Science of Avatar

19th April 2012

Stephen Baxter: Last and First Contact
Last and First Contacts

Newcon Press
26th April 2012

Stephen Baxter: Resplendent
Destiny's Children Book 4


Stephen Baxter: Transendent
Destiny's Children Book 3

September 2005

Stephen Baxter: Exultant
Destiny's Children Book 2

September 2004

Stephen Baxter: Coalescent
Destiny's Children Book 1

October 2003

Stephen Baxter: Weaver
Time's Tapestry Book 4

February 2008

Stephen Baxter: Navigator
Time's Tapestry Book 3

July 2007

Stephen Baxter: Conqueror
Time's Tapestry Book 2

February 2007

Stephen Baxter: Emperor
Time's Tapestry Book 1

July 2006

Stephen Baxter: Flood


Stephen Baxter: Ark


Stephen Baxter: Stone Spring
Stone Spring

June 2010

Stephen Baxter: Bronze Summer
Bronze Summer

September 2011

Stephen Baxter: Iron Winter
Iron Winter

16th August 2012

Stephen Baxter: Firstborn
A Time Odyssey Book 3

(with Arthur C Clarke)

Del Rey (US)
March 2008

Stephen Baxter: Sunstorm
A Time Odyssey Book 2

(with Arthur C Clarke)

Del Rey (US)
March 2005

Stephen Baxter: Time's Eye
Times Eye
A Time Odyssey Book 1

(with Arthur C Clarke)

Del Rey (US)
Feb 2004

Stephen Baxter: Phase Space
Phase Space
Manifold Book 4

HarperCollins (UK)
August 2002

Stephen Baxter: Origin
Manifold Book 3

HarperCollins (UK)
August 2001

Stephen Baxter: Space
Manifold Book 2

HarperCollins (UK)
August 2000

Stephen Baxter: Time
Manifold Book 1

HarperCollins (UK)
August 1999

Stephen Baxter: Behemoth
Mammoth - Omnibus

November 2004

Stephen Baxter: Icebones
Mammoth Book 3

March 2001

Stephen Baxter: Longtusk
Mammoth Book 2

January 2000

Stephen Baxter: Silverhair
Mammoth Book 1

January 1999

Stephen Baxter: Moonseed

NASA Trilogy Book 3

August 1998 (UK).

Stephen Baxter: Titan

NASA Trilogy Book 2

August 1997 (UK).

Stephen Baxter: Voyage

NASA Trilogy Book 1

November 1996 (UK).

Stephen Baxter: A Xeelee Omnibus
A Xeelee Omnibus
A Xeelee Sequence Book

January 2010

Stephen Baxter: Vacuum Diagrams
Vacuum Diagrams
The Xeelee Sequence Book 5

April 1997

Stephen Baxter: Ring
The Xeelee Sequence Book 4

July 1994

Stephen Baxter: Flux
The Xeelee Sequence Book 3

December 1993

Stephen Baxter: Timelike Infinity
Timelike Infinity
The Xeelee Sequence Book 2

December 1992

Stephen Baxter: Raft
The Xeelee Sequence Book 1

July 1991

Stephen Baxter: Webcrash
The Web Book 2

Orion Books
October 1998

Stephen Baxter: Gulliver
Gulliver Zone
The Web Book 1

Orion Books
October 1997

Stephen Baxter: The H Bomb Girl
The H Bomb Girl

Faber & Faber

Stephen Baxter: The Hunters of Pangaea
The Hunters of Pangaea

NESFA Press (US)
February 2004

Stephen Baxter: Evolution

November 2002

Stephen Baxter: The Light of Other Days
The Light of Other Days

(with Arthur C Clarke)

HarperCollins (UK)

Stephen Baxter: Traces

HarperCollins (UK)
April 1998

Stephen Baxter: The Time Ships
The Time Ships

HarperCollins (UK)
May 1995

Stephen Baxter: Anti-Ice

January 1993

Stephen Baxter: Revolutions in the Earth
Revolutions in the Earth
James Hutton and the True Age of the World

Weidenfield and Nicolson
June 2003

Stephen Baxter: Omegatropic

British Science Fiction Association
June 2001

Stephen Baxter: Deep Future
Deep Future

January 2001

Here you'll find pieces on my work and its background, my other projects, my wider life...

All material copyright © Stephen Baxter.

Musings on Medusa

The Medusa Chronicles, my new collaboration with Alastair Reynolds (Gollancz, 2016), came out of a chance suggestion by Al in the course of a nostalgic email exchange: why don’t we write a sequel to A Meeting with Medusa?

Sir Arthur C. Clarke’s much-loved novella was originally published in Playboy for December, 1971. It is a saga of the exploration of Jupiter’s cloud layers, with the intrepid Howard Falcon encountering aerial life forms dominated by the huge ‘medusae’. It was perhaps Clarke’s last significant work of short fiction, and has been reprinted many times since – perhaps most notably as a terrifically illustrated serial in the short-lived magazine Speed & Power (IPC, issues 5–13, 1974), a rendition which made a significant impact on the imagination of a young Reynolds.

But Clarke said (in Astounding Days, 1989) that his own fascination with Jupiter began much earlier, with the spectacular cover painting by Frank R. Paul of the very first SF magazine he ever saw, the November 1928 edition of Gernsback’s Amazing Stories, showing astronauts on a Jovian moon hanging before the planet itself. Clarke was not quite eleven years old when this was published.

All we can see of Jupiter telescopically are the upper cloud layers, as painted by Paul. With no more knowledge than that, much early sf treated Jupiter as merely an exotic, if larger, version of Earth. In the twentieth century however the advance of astronomy gave us a more realistic framework to explore. Jupiter, over three hundred times as massive as the Earth but with a much lower density, must be made of the same stuff as the sun, and must have roughly the same composition: hydrogen, helium, and other elements in traces. The upper clouds might offer temperate conditions, but as early as the 1930s there were predictions that deep within the planet the pressures would transform a liquid hydrogen ocean into a ‘metallic’ form, capable of conducting electricity and generating a powerful magnetic field.

Against this background, from the 1930s more grounded Jupiter fiction began to appear, thanks to the influence of editor John W. Campbell Jr., who insisted on scientific realism in the stories he published. In Isaac Asimov’s ‘Not Final!’ (1941) Jovians, made xenophobic by an ignorance of the universe beyond the cloud decks, regard humans as vermin. And because of the planet’s vast size and resources, ‘I tell you that the Jovians . . . are the natural rulers of the Solar System . . .’ For now, however, they lack the technological means to escape their world.

Clifford D. Simak’s ‘Desertion’ (1944) shows an attempt to cope with Jupiter’s hellish conditions by transforming humans into a form of Jovian life: ‘He had expected a hell of ammonia rain and stinking fumes and the deafening, thundering tumult of the storm . . . He had not expected the lashing downpour would be reduced to drifting purple mist that moved like fleeing shadows over a red and purple sward.’ Poul Anderson’s ‘Call Me Joe’ (1957) features a kind of tele-operation. Rather as in the movie Avatar (2009) a crippled human operator called Edward Anglesey is ‘psionically’ linked to Joe, a centaur-like artificial life-form, a ‘pseudojovian’, on Jupiter’s surface: ‘Imagine being strong!’ Ultimately Joe takes over, with the last of Anglesey’s consciousness taken into his own.

In the 1960s predictions of temperate, Earthlike conditions of temperature and pressure in Jupiter’s upper atmosphere, as well as the possibility of the presence of a wide variety of organic molecules, led to speculation about life in the Jovian cloud layers. It was into this version of Jupiter that Howard Falcon of A Meeting with Medusa descended, in a mixture of a bathyscaphe and hot air balloon. Later, a detailed study by Sagan and Salpeter (1976) led to a famous visual depiction in Sagan’s Cosmos TV series of cloud beasts not unlike Clarke’s.

But by 1971 Clarke had already been to Jupiter. Indeed the planet was a central location in the saga for which Clarke may be best remembered, 2001: A Space Odyssey (1968) and its sequels.

In 2001 itself, while in the movie version Jupiter was the destination for the Discovery spacecraft, in the novel Jupiter was used merely for a flyby and gravitational slingshot en route to Saturn. As the Discovery passed, however, two probes were dropped into Jupiter’s upper atmosphere. One probe fails but the other, in a prevision of Falcon’s adventures, penetrates high cloud to an area of clear air above a deeper layer of clouds; there are glimpses of structure – a cone-shaped ‘mountain’ surrounded by a halo of ‘beads’ – before the probe is crushed by the pressure, and Discovery sails on (p122).

Since Clarke’s pioneering voyages, more writers have ventured into Jupiter’s clouds. In If the Stars Are Gods by Benford and Eklund (1977), a thoughtful saga of ambiguous contacts with exotic alien life, we encounter medusa-like Jovians feeding on the planet’s radio energy. In Ben Bova’s Jupiter (2000) humans embedded in breathable fluid quickly pass through Falcon’s upper atmosphere, where they encounter ‘Clarke’s Medusas’, and descend into a planet-girdling ‘ocean’ layer of water some 5000 km thick. Perhaps the most remarkable fictional descent into Jupiter’s clouds, in Kim Stanley Robinson’s Galileo’s Dream (2009), was achieved by Galileo Galilei himself – ‘I primo al mondo! The first man to see Jupiter’s four moons, which had been circling it since the creation’ (chapter 1). In the year 3020, as a by-product of a complex conflict over how to deal with the discovery of Jovian life, Galileo is drawn through time into an extraordinary journey into a Jupiter full of life and mind: ‘The bands and the swirls have always been its thoughts . . .’

Jovian cloud intelligences have even troubled Doctor Who. In the audio drama The Jupiter Conjunction (2012), the Fifth Doctor encounters ‘Jovians,’ inhabitants of the planet’s atmosphere, ‘gas, dust and vapour held together by some navigating consciousness . . .’ He compares their rich culture to ‘an architecture made out of ideas’.

Jupiter’s moons, which are relatively Earthlike worlds, tend to attract more attention than the great planet itself. But Jupiter is enormous, in mass, area and volume far out-massing anybody in the solar system save the sun itself: it is like a pocket universe. And we know virtually nothing about it – which is one reason Al and I were drawn to our sequel project. Let’s hope we don’t have to wait much beyond the end of the current century to find out more, when Falcon’s Kon-Tiki is scheduled for its momentous meeting with Medusa.

Avatar: The Seven Wonders of the Solar System

We see very little of the solar system in the movie Avatar: just a few brief scenes on a desolate Earth. But to have reached the stars in Avatar’s future, humans must have reached, and probably exploited, the worlds of our solar system. So before we rush off to the stars, let’s stop and smell the interplanetary flowers.

OK, there’s no Pandora in the solar system. OK, there isn’t even a Barsoom. But we’ve sent unmanned spacecraft to inspect all the planets and their moons save distant Pluto, and have landed on several of them - and what we’ve found among the worlds of the solar system is wonderful enough, even if it’s not at all what we expected (though that in itself is a great news for a scientist). And if humans are going anywhere in space in your lifetime, and your children’s, it’s likely to be to one of these destinations. These worlds are ours; this is home.

So let’s take a brisk informal tour of the Seven Wonders of the Solar System, as chosen by me (you’re free to disagree with my selection), and in no particular order - save for the last, which is the closest we’re likely to get to Avatar’s Pandora for a good while.

Number One: The Peaks of Eternal Light

I’m immediately cheating slightly: not one wonder, but two. Our own moon may have no life, no air, precious little water. But it does host at least two wonders worth travelling a light-second or two to see.

The first, of course, is the Apollo landing sites - the first patches of ground on another world touched by human hands. Some day these will be visited by archaeologists, and then cordoned off as heritage sites, and then your great-grandchildren will have to pay to see them. For now the evidence that humans walked on the moon, the abandoned gear and footprints, is invisible from Earth even through the space telescopes. But (much to the chagrin of conspiracy theorists who believe they didn’t go there at all) the Apollo landing sites have been photographed from space by a recent unmanned NASA craft.

And my natural lunar wonder is far from the Apollo sites, which (for reasons of orbital mechanics and other mission design factors) were all on the moon’s nearside and not that far from the lunar equator.

At the moon’s north pole, at a crater called Peary, there are mountains where the sun never sets. This is believed to be the only site in the solar system where this is true. It comes about because the moon’s axis isn’t tilted relative to the plane of its (and Earth’s) orbit around the sun - unlike Earth’s tilt which is the cause of our seasons.

This would be a good site for colonisation as the temperature is reasonably uniform, compared to the rest of the moon which goes through wild temperature swings during the two-week lunar ‘days’ and two-week ‘nights’. Water ice may have gathered in the endless shadows at the foot of those peaks. Arthur C Clarke and I, in our collaborative novel Sunstorm (2005), once put a solar observatory there. And it’s a cracking tourist destination for adventurous travellers. Be the first to spread your beach towels on those sunlit slopes!

Number Two: Mars

No, it’s not Barsoom: no princesses, no tripod fighting machines. The real Mars is a small, strange world, very unlike the Earth - but, far from being the disappointment we once felt, it has a grandeur and appeal of its own.

On Mars there are volcanic mountains so tall they stick out of the atmosphere. On Mars, there are channels - not artificial canals, but a canyon system which stretches around half the planet - and smaller valleys that look as if they were carved by flowing water.

And maybe there’s life there after all. In 1996 NASA scientists presented a meteorite, proven to be from Mars, which appeared to have traces of life in it. Even if the results of the scientific studies of that particular bit of rock have proven inconclusive, a new dream of Mars was born, of a world that might be arid and cold now, but once harboured life of its own - and perhaps still does. The tale of this much-loved world is evidently not yet finished.

Number Three: Venus

Venus is no jungle world. There are no dinosaurs, and no soda-pop seas either. It’s so inhospitable, in fact, that the first spacecraft to attempt a landing, sent by the Soviets, was crushed like an eggshell in an ocean of atmosphere long before it reached the ground.

Venus is a world only a little smaller than Earth, but swathed in a great monstrous ocean of atmosphere: almost all of it carbon dioxide, a hot bright layer that utterly blankets the ground from our view, so thick that at its base it exerts a pressure equivalent to a depth of a kilometre under Earth’s oceans.

Imagine penetrating those clouds. Everywhere you look the world is murky red, both sky and land. This dense air, still, windless, is more like a deep ocean than our atmosphere. The sky above is like an overcast Earth sky, the light a sombre red, like a deep sunset. The sun itself is invisible save for an ill-defined glare low on the horizon.

This is a world of volcanism. You see continents separated by vast plains of flood basalts - frozen lakes of lava, like the seas of the Moon - and punctured by thousands of small volcanoes, shield-shaped, built up by repeated outpourings of lava. But there are giant shield structures, like Hawaiian volcanoes, that tower kilometres above the plains, covered in repeated lava flows.

The geologists believe that when Venus formed it was a sister of Earth, if not an identical twin. On Venus, closer to the sun, the air was dominated by carbon dioxide, and the oceans were hot - perhaps as hot as two hundred degrees - and the atmosphere humid, laden with clouds. Young Venus was a moist greenhouse, and life might have flourished there.

But Venus, fatally, was just a little too close to the sun, and the climate, over the longest of timescales, was unstable. Venus got hotter. There must have been a paucity of rain, a terrible drought. Finally the oceans themselves started to evaporate.

The ‘day’ on Venus lasts more than a hundred Earth days, a stately combination of Venus’s orbit around the sun and its long rotation time - a day longer than Venus’s year, in fact. If you were to wait around for Venusian night there would be no relief from the searing warmth, so effectively does the great blanket of air redistribute the heat. But, as your eyes fully adapt to the dark, you see that there is still light here, even though no starlight could penetrate the immense column of air above. The ground itself is so hot it is shining: wrinkles and ridges and volcanic cones loom eerily from the dark.

What’s so wonderful about such a hell-hole? For me the wonder is the human story. Despite the (literally) infernal conditions, human craft have made it here. In the 1960s, while the Americans sent humans to the moon, and gaudy, fragile spacecraft to Mars, the Soviets kept trying for Venus. They finally achieved a landing, with Venera 7 in 1970, a spacecraft as tough as Avatar’s AMP suits. A very Russian achievement.

Someday somebody will leave a plaque on the landing spot - for surely nothing is left of the craft itself.

Number Four: A World with a Roof

It is one of the general wonders of the age of planetary exploration that the solar system turns out to be full, if not of Earths, at least of abodes where some form of life is conceivable.

Jupiter’s second moon out, Europa, is close enough to its parent for its tides to have a significant effect. Jupiter, a ‘Jovian’ like Avatar’s Polyphemus, parent of Pandora (in fact Jupiter gave its name to that class of planets), is a big world, and exerts big tides. Europa was formed with a thick layer of water ice surrounding a rocky core. Whereas our moon has enough mass for its gravity to raise the level of the oceans by a few metres, Jupiter’s tides have injected enough heat energy to melt a deep layer of Europa’s water-ice mantle.

So Europa has a cracked icy crust that looks like nothing so much as ice floes on Earth’s frozen-over Arctic ocean. Beneath the ice layer is an ocean, tremendously deep, perhaps hundreds of kilometres - perhaps reaching all the way to the moon’s rocky core. And hydrothermal vents on that black-as-night sea bed could provide nutrients for some form of life.

The scientific jury is out on whether there actually is life on Europa, and probably will be until we send advanced probes out to see - perhaps even robots that will be able to melt through the surface ice and go swimming down for samples. But as a possible abode of life, a vast lode of liquid water unexpectedly sitting at the orbit of Jupiter is just what a xenobiologist like Avatar’s Dr Grace Augustine would have ordered (‘xeno’ means ‘alien’).

And while at Europa you might glance up to see the solar system’s perfect storm: Jupiter’s Great Red Spot, a storm that has been raging for centuries, so vast that two planets the size of Earth could fit inside its circling winds - and a blemish on the immense face of the planet that might make you pine for Polyphemus.

Number Five: Rings

The rings of Saturn: I know, what a cliché. But how could I ignore them?

Imagine floating in the upper clouds of Saturn, somewhere near the equator, perhaps in some kind of tourist-cruise airship, robust enough to survive the speed-of-sound winds in the ammonia-laden air. You can’t descend too far; even if you survived the descent into this gas giant’s thickening air you would find yourself immersed in a global ocean of liquid metallic hydrogen: not recommended.

But you’re not interested in what’s below you, but what’s above.

The rings soar above you, above the upper clouds, seventy-five thousand kilometres high. They look impossible - an artificial structure, like one of Pandora’s stone arches in Avatar, erected in some impossibly low gravity. And the shadow cast by the planet itself cuts off the rings with a dead straight line itself thousands of kilometres long. The sun itself, small and remote, is setting. But the ring shine gleams from the faces of your children as they try to count the crescent moons in the sky.

Worth a visit.

And that’s a thought that must have occurred to other visitors too. If we are ever to find traces of alien exploration of the solar system, we could do worse than check out the clichés, the obvious places - such as the site of the most spectacular rings in the system.

Number Six: Home

My penultimate wonder is closest to home of all: Earth, as seen from space by astronauts for the last half a century.

Our home world is a wall of blue light, as bright as a slice of tropical sky; it dazzles you, making the sky pitch black when you look away. If you look ahead of your orbiting craft you can see the planet’s curve, a blue and white arc with black space above it. But when you look straight down, the skin of the Earth fills your spacecraft window, scrolling steadily past like some colourful map. On the land you can easily make out cities - a grey, angular patchwork - and the lines of major roads. The orange-brown of deserts is vivid, but the jungles and temperate zones are harder to spot; their colour does not penetrate the atmosphere so well, and they show up as a grey-blue, with the barest hint of green. And on the oceans you can see the wakes of ship, feathering out like brush strokes on the sea’s calm surface. There is a sense of depth to the atmosphere - shadows under the clouds as they slide across the face of the seas. The clouds thicken towards the equator, and when you look ahead, tangential to the Earth’s surface, you can see them climbing up into the atmosphere.

What a view. And maybe a view within the reach of a few more of us, if the current plans for space tourism go ahead (and the price comes down). Such views, returned by the Apollo astronauts, have done a great deal to inform us about the fragility and smallness of the only place we know of where we can live unsupported. And Avatar is in part a fable about what might happen if we forget that.

Number Seven: Titan

The furthest any craft from Earth has landed, so far, is on Titan, sixth moon of the sixth planet Saturn, nearly ten times as far from the Earth as the sun. It was an astounding achievement.

And the world it found is the solar system’s own Pandora.

Titan, Saturn’s largest moon, was discovered by the Dutch astronomer Christianus Huygens in 1655. To him it was just a dot of light, glowing dull orange - but in 1944 Gerard Kuiper, another Dutch astronomer, discovered methane gas there. This was a moon with an atmosphere! Titan turned out to have has the most massive atmosphere of any rocky world after Venus. Bigger than our moon but only half the diameter of Earth, Titan is able to hold onto a fat layer of air because of its extreme cold.

Our first close-up views of Titan came in 1980 and 1981, when Voyagers 1 and 2 flew past Saturn. But Titan was just a ball of smog; we could see nothing of the surface. Then, in 2004, the Cassini spaceprobe arrived, a big beast about the size of a school bus with a fat pie-dish shape clinging to one side. This was the Huygens probe, named for the pioneering astronomer. Dormant for most of the interplanetary cruise, the lander was released at Christmas 2004, and in January 2005 plunged into the centre of Titan’s sunlit face.

What kind of world did Huygens find? In many ways it really is so like Avatar’s Pandora, this low-gravity moon of a giant planet - for it is remarkably Earthlike. There are mists and clouds, and slow-falling rain; there are branching river valleys that lead to oceans, crossed by waves hundreds of metres tall. One, called the Kraken Mare, is as big as the Caspian Sea. Huygens came down on what appeared to be a relic of a flash flood, a plain littered by worn pebbles.

But Titan is an Earth reimagined in different materials. On Titan water ice plays the role silicate rock does on Earth, and methane plays the part of liquid water. Those pebbles were ice, not rock. There could even be ‘cryovolcanoes’, water bubbling like lava; no volcanoes have been seen but there is evidence of lava flows in the past. The methane cycle isn’t quite like Earth’s water cycle, so the weather isn’t the same; evaporation is slow, but the air can hold a lot of vapour, so you get long periods of drought punctuated by intense rainstorms.

If you stood on Titan you would be a monster of molten lava! But, in that low gravity and thick air, you could strap on wings, flap your arms and fly like a banshee.

And, like Pandora, Titan is full of opportunities for life.

Out of those layers of clouds, complex organic molecules - the stuff of life itself - continually drift down to the surface below. These are created by electrical storms in the atmosphere, and the reaction of sunlight and Saturn’s magnetism with the upper air. These deposits could seed an Earthlike life: carbon-water life, maybe anaerobic (that is, oxygen-hating) methane-eating bugs, sluggishly building pillows and mounds in the cold brine, maybe based on a kind of DNA - maybe a relative of Earth life, blown here by the meteorite winds that might have transferred life from Mars to Earth and back.

But there could be other kinds of life. Maybe a more exotic sort of carbon-based life form, using ammonia as its solvent rather than water and a metabolism based on carbon-nitrogen bonds, could be found in the stuff bubbling out of the cryovolcanoes. This is the sort of life that might live in the oceans of ‘roof worlds’ like Europa. Most exotic of all could be a community of slime-like organisms that use silicon compounds as their basic building blocks, not carbon; they might live in the surface ethane lakes, so cold they favour the long but fragile silicon-silicon molecular chains on which this form of life depends. Such forms might find a home in the cryovolcanoes of Triton, the even colder moon of Neptune, where there are lakes of liquid nitrogen.

Nowadays we envisage many kinds of life, and many diverse habitats in the solar system. But Titan is extraordinary, for it may be a junction for life forms related to types from deep within the solar system’s warm heart, and from its chill edge. Huygens only glimpsed this; we must go again.

But Titan, like the other bodies of the solar system, might have a value beyond science.

Titan is a natural organic-synthesis machine, way off in the outer system. It could become a factory for future colonists, churning out fibres, food, any organic-chemistry product - even food, manufactured from carbon, hydrogen, oxygen, nitrogen. Further out in time, it may be possible to export Titan’s volatiles to inner planets lacking them; Titan nitrogen could be used to terraform Mars, to make it like the Earth.

And Titan, a vital resource pool on the fringe of interstellar space, may someday be a key refuelling dump for ships like the Venture Star, on their way to the stars.

The worlds of the solar system are more than just mines in the sky. There are already proposals to preserve their unique value. Radio astronomer Claudio Maccone of Turin advocates a ‘protected antipodal circle’ of radio silence covering the moon’s far side, the only place in the solar system permanently shadowed from Earth’s clamorous broadcasts and so ideal for radio astronomy.

Certainly I would hope that by the time we get to Titan we will treat anything alive there, whether our cousins or not, with more respect than Avatar’s RDA treats Pandora.

The Xeelee Sequence - Timeline

A complete (as of September 2015) timeline for the ‘Xeelee Sequence’ of novels and stories.

Singularity: Big Bang

ERA: Primordial

~13.7bya (billion years ago): Life born with universe.

~13.5bya: First stars. First contact between Xeelee and photino birds. Xeelee timeships begin modification of Xeelee evolutionary history.

~10bya: Construction of Bolder’s Ring begins. Birth of Sol.

~5bya: Assaults on Ring by photino birds begin. Life on Earth emerges.

~1bya: First infestation of Sol by photino birds.

~1 million years ago: Galaxy core explosion caused by Xeelee activity.

ERA: Earth

AD 476-2005: Events of Coalescent. Emergence of first human ‘hive’ in Rome.

AD 2047: Events of Transcendent (see also ~AD 500,000)

ERA: Expansion

AD 3000+: Opening up of Sol system. First Expansion of humanity to the stars begins.

AD 3621: Birth of Michael Poole.

AD 3672: ‘The Sun-People’ **.

AD 3685: ‘Return to Titan’ ***.

AD 3698: ‘The Logic Pool’ **.

AD 3717: Launch of GUTship Cauchy. Events of Timelike Infinity begin.

AD 3825: ‘Gossamer’ **.

AD 3829: Wormhole time-travel invasion by Occupation-Era Qax (Timelike Infinity)

AD 3948: ‘Cilia-of-Gold’ **.

AD 3951: ‘Lieserl’ **: Events of Ring begin (see also AD 5,000,000).

AD 3953: Launch of GUTship Great Northern.

AD4820: ‘Starfall’ ***: collapse of solar empire.

ERA: Squeem Occupation

AD 4874: Conquest of human planets by Squeem.

AD 4874: ‘Pilot’ **.

AD 4922: ‘The Xeelee Flower’ **.

AD 4925: Overthrow of Squeem. Second Expansion begins.

AD 5024: ‘More Than Time or Distance’ **.

AD 5066: ‘The Switch’ **.

AD 5071: ‘Remembrance’ ***.

ERA: Qax Occupation

AD 5088: Conquest of human planets by Qax.

AD 5274: Return to System of GUTship Cauchy. Launch of backward time-travel invasion by Qax. Establishment of Qax wormhole to future (~AD 5700) (Timelike Infinity).

AD 5274: ‘Endurance’ ***.

AD 5301: ‘Cadre Siblings’ *.

AD 5406: ‘Blue Shift’ **.

AD 5407: ‘Conurbation 2473’ *. Overthrow of Qax. Humans acquire Spline and starbreaker technology.

ERA: Resurgence

AD 5408: ‘Reality Dust’ *. Third Expansion begins under Coalition government.

AD 5420: ‘Mayflower II’ *. Launch of generation starship Mayflower II. (See also AD 24974.)

AD 5478: ‘All in a Blaze’ *

ERA: The War with the Ghosts

AD 5499: ‘Silver Ghost’ *: first contact with the Silver Ghosts.

AD 5611: ‘The Quagma Datum’ **.

AD 5653: ‘Planck Zero’ **.

AD 5664: ‘Soliton Star’ **.

AD 5802: ‘The Cold Sink’ *. The Ghost wars break out.

AD 5810: ‘The Seer and the Silverman’ ***.

AD 6454: ‘On the Orion Line’ *.

AD 7004: ‘Ghost Wars’ *. End of effective resistance by the Ghosts.

AD 7524: ‘The Ghost Pit’ *.

ERA: Assimilation

AD 10,000+: Humans dominant sub-Xeelee species. Rapid expansion and absorption of species and technologies. Launch of Xeelee timeships into deep past.

AD 10102: ‘Lakes of Light’ *

AD 10515: ‘The Gödel Sunflowers’ **.

AD 10537: ‘Breeding Ground’ *

AD 12478: ‘The Dreaming Mould’ *

AD 12659: ‘The Great Game’*. Initiation of hostilities with the Xeelee.

ERA: The War for the Galaxy

AD 20424: ‘The Chop Line’ *.

AD 21124: ‘Vacuum Diagrams’ **.

AD 22254: ‘In the Un-Black’*.

AD 23479: ‘Riding the Rock’ *.

AD 24973: Events of Exultant. The human conquest of the centre of the Galaxy.

ERA: The Shadow of Empire

AD 24974: ‘Mayflower II’ *. Retrieval of generation starship Mayflower II.

c.AD 25,000+: Collapse of central Coalition government. Conflict among successor states.

AD 27152: ‘Between Worlds’ *

c.AD 40,000+: The Bifurcation of Mankind.

ERA: The War to End Wars

c.AD 90,000+: Reunification.

c.AD 100,000+: Human assaults on Xeelee concentrations across the supercluster.

AD 104,858+: Events of Raft

AD 104,858: ‘Stowaway’ **.

AD 168,349: Launch of the Exaltation of the Integrality.

AD 171,257: ‘The Tyranny of Heaven’ **.

AD 193,474: ‘Hero’ **.

c.AD 193,700: Events of Flux

c.AD 200,000+: Establishment of Commonwealth by ‘undying’. Continued conflict with Xeelee.

c. AD 500,000: Events of Transcendent (see also AD 2047). The high-water mark of human destiny.

ERA: The Fall of Mankind

c.AD 500,000+: The retreat of mankind begins. Fragmentation of human unity. The Long Calm.

c.AD 700,000+: The Xeelee Scourge. Intervention of photino birds in stellar evolution becomes significant.

AD 978,225: ‘Gravity Dreams’ ***.

c.AD 1,000,000: ‘The Siege of Earth’ *. Final siege of Sol system by Xeelee. Defeat and imprisonment of mankind.

ERA: Flight

c.AD 1-4,000,000: Xeelee and photino birds’ transformation of baryonic universe.

c. AD 4,000,000+: Migration of Xeelee through Ring. Sol leaves Main Sequence.

c. AD 4,000,000: ‘Secret History’ **.

AD 4,101,214: ‘Shell’ **.

AD 4,101,266: ‘The Eighth Room’ **.

AD 4,101,284: ‘The Baryonic Lords’ **.

c.AD 4,900,000: Final destruction of Ring by photino birds begins.

ERA: Photino Victory

c.AD 5,000,000+: Last humans return to Sol in GUTship Great Northern, and travel to Ring: Events of Ring (see also AD 3953).

AD 10,000,000+: Virtual extinction of baryonic life. Most of the last humans survive on a time-shifted Earth.

ERA: Old Earth

AD 3.8 billion years: ‘PeriAndry’s Quest’ ***.

AD 4 billion years: ‘Climbing the Blue’ ***.

AD 4.5 billion years: ‘The Time Pit’ ***.

AD 4.8 billion years: ‘The Lowland Expedition’ ***.

AD 5 billion years: ‘Formidable Caress’ *** . Collision of Milky Way Galaxy with Andromeda.

Singularity: Timelike Infinity



Raft (1991), Timelike Infinity (1992), Flux (1993), Ring (1994), Coalescent (2003), Exultant (2004), Transcendent (2005).


* Collected in Resplendent (2006).

** Collected in Vacuum Diagrams (1997)

*** Collected in Xeelee: Endurance (2015)

HG Wells: No End to War

Stephen Baxter September 2008


HG Wells wrote of war between humans and of war between humans and non-humans. Yet the intellectual and emotional legacy of these works is contradictory.

In the last year I have become involved in SETI, the scientific Search for Extraterrestrial Intelligence, and have happened upon a remarkable aspect of Wells’s legacy. In The War of the Worlds (1898) Wells defined the modern notion of aliens, ‘intelligences greater than man’s and yet as mortal as his own,’ and immediately set them in conflict with mankind. After a century of war and of science fiction influenced by Wells, Wells’s Martians remain one fearful model of our expectation of alien life, to the extent that there is currently a fierce controversy within the SETI community about proposed attempts to signal to extraterrestrial civilisations. Some aliens must be warlike, the argument goes; to make our presence obvious would be to invite disaster.

But war is repugnant. Mr Britling Sees It Through (1916) is a fine account of the anguish as experienced by Wells aged fifty (my own age now) of the First World War, a conflict in which ‘our only strategy was to barter blood for blood’. The horror of the waste of youth impels Britling to argue that ‘there is no chance of bettering life until we have made an end of all that causes war’. In this Wells evidently reflected a public mood in Britain and Germany at the time.

However many in the SETI community believe that Britling’s anguished longing for an end to war is futile, for even if mankind could discover peace within itself, the universe as a whole must inevitably be plagued by Darwinian carnage. It is a measure of Wells’s capacity of imagination that his works illuminate both sides of this dismaying contradiction.

Will we ever be free of war?

In late 1914, the first year of the Great War, HG Wells published a collection of journalism whose title came to sum up what many hoped would ultimately be the result of that terrible conflict: The War That Will End War. (Actually, as is the way of such things, the precise origins of that famous phrase are disputed.) But while Wells wrote of war between humans, he also wrote of war between humans and non-humans. And the intellectual and emotional legacy of these works is contradictory. Though Wells came to long for an end to a war on this world, it may be that he believed that wars between worlds were inevitable.

After 1914 Wells’s views on the unfolding war changed greatly, and in the middle years of the war he recorded these adjustments with searing honesty in a novel called Mr Britling Sees It Through (1916; page numbers from the Odhams Press edition). I suspect this book isn’t well known to Wells’s sf readers. But in its time it was a commercial success, and sold to soldiers in the trenches on both sides of the wire. I can heartily recommend it.

Mr Britling is a middle-aged writer and commentator, around the same age as Wells (who was fifty in the month the book was published) with a similarly complicated personal life. So, given his name, Britling is clearly meant to represent both Wells and a wider Britishness. But Britling is a few years younger than Wells - and, crucially, he has a late teenage son, Hugh, who is therefore in danger of call-up. Wells’s own children were too young. Through Britling’s reaction to the war we glimpse the painful changes in Wells’s own thinking.

We meet Britling in the summer of 1914, a last season of complicated house parties and village fetes. Britling is frustrated by the complacency of the ruling classes around him: ‘We’re at the end of a series of secure generations in which none of the great things of life have changed materially. None of us ... really believe that life can change very fundamentally any more forever (pp38-9). In fact British soldiers hadn’t been engaged in a war on the continent for a century, and nor had Britain faced a serious threat of invasion.

But a brief cutaway to Sarajevo punctures that complacency. Passages which describe the looming approach of war illustrate one strand of Wells’s writing, his use of almost cinematic techniques. At a summer fete, ‘the small Britling boys were displaying their skill and calm upon the roundabout ostriches, and less than four hundred miles away with a front that reached from Nancy to Liege more than a million and a quarter of grey-clad men ... were pouring westward to take Paris ... All across the sunshine of this artless festival there appeared, as if it were writing showing through a picture, "France Invaded By Germany"’ (p124).

When war comes, Britling’s first reaction is ‘a phase of imaginative release .. Things that had seemed solid forever were visible in flux; things that had seemed stone were alive’ (p146). This reflects the Wells who wrote The War That Will End War, who seems to have hoped that the war might be a short sharp shock of a cleansing kind that would lead to a new order based on a world congress, a global court, and so on. Perhaps it would be like the cosmic close encounter of In the Days of the Comet (1906). But the incompetence, waste and growing savagery of the war soon dispels that dream.

The war becomes personal for Britling when an elderly relation is killed by a bomb from a Zeppelin, a juxtaposition of forces that is ‘like a page from some fantastic romance by Jules Verne’ (p211). Then son Hugh lies about his age, joins up and is sent to the front. Wells visited the front himself, and he includes a convincing series of letters from Hugh detailing the tommies’ life. Britling by now is revolted by the war: ‘The spirit and honour and drama had gone out of this war. Our only hope now was exhaustion. Our only strategy was to barter blood for blood - trusting that our tank would prove the deeper ... while into this tank stepped Hugh, young and smiling’ (p230). Hugh innocently admits, after seeing some action, how ‘I began to perceive that war is absolutely the best game in the world’ (p232). But Hugh is killed. ‘All over England now ... women and children went about in October sunshine in new black clothes’ (p271).

Britling writes and writes, an authentic thing for a writer to do, trying to come to terms with his son’s death and the horror of the war. He experiments with ideas of social Darwinism - maybe cruelty is necessary for a healthy species - and dreams again of world federations, and even turns to religion. Wells himself went through all these evolutions of thought. The book ends with a facsimile handwritten page of fragments as even Britling’s writing, his one solace, breaks down, and the name ‘Hugh’ is written over and over.

Wells was in a privileged position, having worked on propaganda for the government and having visited the battlefields. But it’s remarkable how clearly he / Britling saw the consequences of the war while in the midst of it: ‘This war ... is killing young men by the million, altering the proportions of the sexes for a generation, bringing women into business and offices and industries, destroying the accumulated wealth that had kept so many of them in refined idleness, flooding the world with strange doubts and novel ideas ...’ (p188). But where Wells / Britling had once almost welcomed the conflict as a way of shaking things up, in the end he rejects war itself vehemently: ‘Massacres of boys! That indeed is the essence of modern war. The killing off of the young. It is the destruction of human inheritance’ (p303). I’m now older that Wells was then, and I can testify how heartbreaking it is to visit war graves and see how young their occupants were, how much of their lives were left unfulfilled. Wells / Britling powerfully concludes, ‘No life is safe, no happiness is safe, there is no chance of bettering life until we have made an end to all that causes war’ (p285).

But if Wells came to long for an end to war as expressed in Britling - and maybe that’s possible among humans - in another strand of his writing Wells almost always showed contact between human and non-human, even between intelligent species, degenerating into conflict.

His short story In The Abyss (1896), about contact with sea-bed aliens, is an honourable exception, although it ends on an ominous note: ‘It is hardly probable that no further attempt will be made to verify his strange story of these hitherto unsuspected cities of the deep sea.’ But consider The First Men in the Moon (1901). This is a story of contact between two intelligent species who actually learn to communicate. But Cavor and Bedford quickly convince the Selenites that they are ‘strong dangerous animals’, and Bedford, lusting after the ‘gold knocking about like cast iron at home’ considers ‘coming back in a bigger sphere with guns’ (Chapter 15). Cavor, though, dreams of tapping Selenite wisdom, and the Selenites learn human speech. But the more the Grand Lunar learns of Earth the more horrified he is by man, who ‘lives on the mere surface of a world ... who cannot even unite to overcome the beasts that prey upon his kind, and yet who dares to invade another planet’ (Chapter 24). In the end Cavor foolishly convinces the Grand Lunar of humans’ ‘insatiable aggressions, their tireless futility of conflict’ (Chapter 25). And, presenting himself as the only way by which man can reach the Moon, Cavor gets himself killed.

Even in Wells’s ur-text of alien conflict, The War of the Worlds (1898), there is an attempt to communicate, on our side at least: ‘This was the Deputation. There had been a hasty consultation, and since the Martians were evidently, in spite of their repulsive forms, intelligent creatures, it had evidently been resolved to show them, by approaching them with signals, that we too were intelligent’ (Book 1, Chapter 5). Well, the white flag’s reply is a dose of the heat ray. The Martians aren’t here to talk but to take our world, and indeed our blood. To the Artilleryman, the War of the Worlds ‘isn’t a war ... any more than there’s war between men and ants’ (Book 2, Chapter 7). He’s right; this is something more fundamental than human war.

Speaking of ants, Wells portrayed conflicts between intelligent species in which there is no attempt to communicate at all. In The Empire of the Ants (1905) an Amazonian village is overwhelmed by a new sort of ant, and evidently an intelligent sort. When they move in the open the ants are in ‘spaced-out lines, oddly suggestive of the rushes of modern infantry advancing under fire’. But there is no attempt at communication. The ants simply overwhelm humans: ‘Their action has been a steady progressive settlement, involving the flight and slaughter of every human being in the new areas they invade.’ And on our side, ‘The Brazilian Government is well advised in offering a prize of five hundred pounds for some effectual method of extirpation’.

I believe the clearest expression of Wells’s thinking in this regard comes in his story The Grisly Folk’ (1921). The Neanderthal is our closest relative but seems monstrous: ‘The grisly thing ... was hunchbacked and very big and low, a grey hairy wolf-like monster.’ Once they have met, conflict between Neanderthals and humans is immediate and relentless - and one-sided: ‘For the Neandertalers it was the beginning of an incessant war that could end only in extermination ... Many and obstinate were the duels and battles these two sorts of men fought for this world in that bleak age of the windy steppes, thirty or forty thousand years ago. The two races were intolerable to each other.’ But why intolerable? Because: ‘They both wanted the caves and the banks by the rivers where the big flints were got. They fought over the dead mammoths that had been bogged in the marshes, and over the reindeer stags that had been killed in the rutting season.’ This is not human war. This conflict is Darwinian, between two species competing for the same ecological niche, and so it has a depth and intensity and bleakness of purpose approached only, perhaps, in the Nazis’ systematic assaults on the Jewish, Slavic and other races, whom they regarded, indeed, as belonging to a different species.

Wells had studied evolution under Huxley, Darwin’s follower, and understood this very well. ‘The Grisly Folk’ is like a dramatisation of Darwin’s own writing, for example of this extract from Chapter 3 of On the Origin of Species (1859): ‘As species of the same genus have usually, though by no means invariably, some similarity in habits and constitution, and always in structure, the struggle will generally be more severe between species of the same genus, when they come into competition with each other, than between species of distinct genera. We see this in the recent extension over parts of the United States of one species of swallow having caused the decrease of another species ...’ Today we might think of red and grey squirrels. ‘We can dimly see why the competition should be most severe between allied forms, which fill nearly the same place in the economy of nature; but probably in no one case could we precisely say why one species has been victorious over another in the great battle of life.’

Wells, the fifty-year-old human being appalled by the Great War, longed for peace between humans. But five years later he was still the Darwinian thinker who appeared to believe that peace was impossible between species, and that their competition must result in the extermination of one side or another, without hope of mediation by intelligence.

After a century of science fiction influenced by Wells, Wells’s Martians remain one fearful model of our expectation of alien life. Many in the SETI community believe that Britling’s anguished longing for an end to war is futile, for even if mankind could discover peace within itself, the universe as a whole must inevitably be plagued by Darwinian carnage. It is a measure of Wells’s capacity of imagination that his works illuminate both sides of this dismaying contradiction.

(Based on a talk to the HG Wells Society annual conference on ‘HG Wells: Wells and War’, Queen Mary University, London, 20th September 2008.)

Sir Arthur C Clarke 1917-2008 - A Tribute

Over the past decade I've been privileged to work with Sir Arthur C Clarke. Our first book was The Light of Other Days (2000), and we went on to write the three-book Time Odyssey series (2002-2008).

In the course of that work, as I revisited Clarke's oeuvre, I was struck by the way his fiction reflected aspects of his life. For instance he documented his Second World War radar research experience in his non-genre novel Glide Path (1963). Whiz-kid engineer Alan Bishop, born like Clarke in England's West Country, is called back to his father's funeral and finds he has grown up: 'He could never escape from [his childhood's] influence... But it would no longer dominate him... He had become entangled in powers and instrumentalities that would surely shape the future' (chapters 21, 30). Just as Bishop/Clarke left his rural childhood for a technocratic future, so mankind must one day leave the green cradle of Earth.

Clarke's fiction is what mattered most to me. Clarke became part of that wartime generation of sf authors who mapped our future in generally progressive and optimistic tones, through such classic books as The Sands of Mars and A Fall Of Moondust.

But Clarke's non-fiction was just as influential. Carl Sagan testified how Clarke's depictions of interplanetary flight inspired him into a career in space science. And thanks to his technical foresight scientists and engineers took Clarke seriously. Clarke's fame as the originator of the concept of geostationary communications satellites is well known. It's no surprise that the Apollo astronauts chose to give their capsules names like Odyssey.

Clarke's career reached its apotheosis in 1968, with the novel and movie 2001: A Space Odyssey. But, as if Kubrick had run an exercise in psychoanalysis, 2001 actually documents Clarke's own long inner odyssey. Clarke himself did not deny the metaphysical speculation in his work (though he was dismissive of fakery and bad science, and believed organised religion to be a blight). The universe is full of wonder, and no complete human being could fail to apprehend that fact. And through the nuts-and-bolts technologies of spacecraft and radio telescopes we reach out for such wonder. Many authors have struggled to express these great and contradictory perspectives. But none, surely, have succeeded so well as Arthur Clarke.

After 2001, Clarke was probably the best-known sf writer on Earth. He was only just over fifty, and had a long career ahead of him yet. His next novel, Rendezvous with Rama, was another terrific success. But in later years Clarke, afflicted by post-polio syndrome, did not always have the strength to fulfil his ideas alone. And that was how I came to work with him.

I first met Clarke in 1992, when my first novel Raft was nominated for the Clarke Award (for best sf novel published in Britain). Clarke was particularly taken by The Time Ships (1995), my sequel to Well's The Time Machine. After that first contact we worked on four books together, The Light of Other Days (2000) and the Time Odyssey series (2002-2008). It was a joy and a privilege for me to work with a man who had such a profound influence on my life, and on the age we live in.

Working with Clarke, I always thought that while he was fascinated by the new, there were traces of old obsessions in his work. In our collaboration Sunstorm (2005), a disorderly sun threatens Earth. The misbehaviour of the sun has featured in many of Clarke's works, beginning with 'Rescue Party' (1946), and including his novel Songs of Distant Earth (1986). I wondered if this theme was a faint echo of that West Country farm boy, dependent on the sun.

As I worked with him, I continued to be reminded of the Somerset farmer's boy who had got hooked on sf through a heady cocktail of Olaf Stapledon and the US pulps. In 3001, back-from-the-dead astronaut Frank Poole says (Chapter 14): 'Do you know what [futuristic super-spacecraft] Goliath reminds me of? ... When I was a boy, I came across a whole pile of old science-fiction magazines that my Uncle George had abandoned - "pulps", they were called ... As I grew older, I realised how ridiculous those spaceships were ... Well, those old artists had the last laugh ... Goliath looks more like their dreams than the flying fuel-tanks we used to launch from the Cape.'

And Clarke never stopped reflecting on his other prime root. In 2001 he sent me a portion of a letter to Stapledon from JBS Haldane, dated 1945: 'Your utopia is a very exciting one. Why, though, must the intelligent animals forget the brutality of the past? ... The final utopia must somehow redeem the past [my emphasis], or else be something less than utopia.' Clarke wrote, 'Dear Stephen - This phrase [emphasised] haunts me - does it give you any ideas?' Well, it did, and my novel Transcendent was the result.

Collaborating on our books, we worked by email and phone. He would call when it was convenient for him in Sri Lanka, sometimes at five in the morning UK time: 'This is Arthur, over and out!'

I'm going to miss such calls very much. Goodbye, Arthur. This is Stephen, over and out.

The Flooding of London

I'm not a Londoner; I was born and raised two hundred miles away. And yet, as for many Britons, much of my life has been dominated by the city. I commuted to work there for four years, and London is the centre of the UK publishing industry, as of so much else. Sometimes it feels as if London is too big for Britain, the capital of a world empire now vanished.

Just like New York and Tokyo, London has come in for its share of genre battering, from alien invasion in HG Wells's The War of the Worlds (1897) to desiccation in the rather fine 1961 movie The Day the Earth Caught Fire (dir. Val Guest). I suppose my own ambivalent relationship with London has come out in my fiction. With Sir Arthur C Clarke, I saved it from fire in Sunstorm (Gollancz, 2005), but in Flood (Gollancz, June 2008) I'm drowning it.

I have observed, in fact, a persistent tendency to submit the place to ordeals, not by fire, but by water.

A very literal depiction of the drowning of modern London is Richard Doyle's Flood (Century, 2002) (this in fact an update of an earlier pre-Barrier novel called Deluge (1977)). In this fat technothriller a North Sea storm surge overwhelms the Barrier and drowns the heart of London - the latter stages accompanied by a disastrous fire that starts among the downstream oil refineries. The research is meticulous, and it's all rather exciting, but setting the river on fire over-eggs the pudding. A poorly received movie of the book was released in 2007.

SAS action man Chris Ryan delivered a juvenile version of a similar scenario in Flash Flood (Red Fox, 2006), in which super-kid Ben Tracey fights off looters, on-the-run terrorists and a shark after a tanker crash disables the Barrier. It's fast-paced, gritty and surprisingly tough; people get killed.

This modern watery anxiety may be a result of the very real threat flooding has always posed to London, whose rivers have been constrained and overbuilt since Roman times. The Thames Barrier was built in response to catastrophic flooding in 1953. Since then climate-change predictions of sea level rises have invalidated some of the Barrier's design assumptions, and after decades of development some one and a quarter million people now live on the capital's flood plain.

But fictional depictions of the flooding of the capital go back a long way before 1953.

The ur-text of London latherings is surely Richard Jefferies' astonishing After London, or, Wild England (1885). The Earth is convulsed by the passage of an 'Unknown Orb': 'It became green everywhere in the first spring, after London ended' (Chapter I). Abandoned London becomes a noxious swamp that dams the Thames, and southern England is drowned by an immense inland sea called the Lake, around which a brutal medieval society huddles behind stockades. The most compelling passages describe a heart-of-darkness journey into the carcass of London itself, a lethal landscape where the beach is black, the air yellow and the sun blood red; 'all the rottenness of a thousand years and of many hundred millions of human beings is there festering under the stagnant water' (Chapter V). It is a relief to retreat to the Lake, which represents beauty, harmony and freedom.

The book has to be seen against the background of late-Victorian distrust of industrial civilisation, as expressed in works like Morris's News from Nowhere (1890). What was different about Jefferies was that as a farmer's son he was under no illusion that a post-apocalypse return to a medieval past would be in some way better than the present; he had lived through a dreadful agricultural depression in the 1870s. But at the same time he expresses an intense dislike of London itself. He may have blamed the city for the consumption that was killing him while he worked on After London, not yet forty; sf is always a projection of the author's own time, of his or her own concerns. And as a naturalist Jefferies is very precise on the recovery of nature in the absence of man; he opens with a description of the kind of grasses which colonise abandoned fields.

A profound response to Jefferies is Brian Aldiss's Greybeard (1964). Spaceborne nuclear tests have sterilised mankind, and as the last childless generations age, civilisation steadily breaks down. The Thames is naturally dammed at Goring, and an inland 'Sea of Barks' (Berkshire) is formed. But this is a symptom of nature reviving, and, amid an earthy story of a world of cantankerous old people, the book is studded with vivid pastoral descriptions which recall Jefferies, as well as a long perspective reminiscent of HG Wells. The fecundity of nature is itself a source of hope, with or without humanity: 'The ascendancy of man had only momentarily affected the copiousness of this stream [of life]' (Chapter 7).

Maggie Gee's more abstract The Flood (Saqi, 2004) is set in her alternate London of earlier books like The White Family, a city centred on Victory Square not Trafalgar, governed not by Blair but 'Bliss'. The science is ropy: the flood may have been caused by a planetary alignment, a concern more astrological than astronomical in our universe, or perhaps by the approach of a comet. But the book is rich on specific detail as people try to progress their ordinary lives of work and child-rearing, of ambition and love and folly, as the gathering waters flood out basements and block roads. As in Jefferies there is again a sense of judgement. Only the truly innocent are spared: in the end, a couple of kids are swept across from Gee's city into our London, emerging in the sunshine of Kew Gardens.

A flooded London is a favourite scenario of our modern satirists and utopians, or dystopians. Ben Elton's Blind Faith (2007) is a dystopian future extrapolated from some current trends, albeit with a rather thick pencil: post-Diana-like 'emotional fascism', the destruction of privacy, the noise, clamour and general mob hysteria of modern life, and, more bravely, the abandonment of reason and a flight to faith: the vaccination of children has become a crime, and religious leaders are in control. The narrative is based self-consciously on Orwell's 1984 (namechecked in the book), as the hero, Trafford, struggles to survive with his identity intact, has his daughter covertly vaccinated, and falls in love with a mysterious woman who finally betrays him. The book ends on a note of hope as Trafford is burned alive at the climax of a Live Aid-like Wembley concert, amid signs that his protestations for reason are taking root. The book is forceful but lacks grace, subtlety and plausibility; it feels like 1984 rewritten by a grumpy old man.

And the setting is a flooded London: '[Finchley] was not an easy place for Trafford to get to, as it involved crossing Lake London with his bicycle and disembarking at the Paddington jetty …' (Chapter 21). It's all our fault; it got this way because we melted the ice caps by burning our fossil fuels, and London itself is a kind of punishment, horribly crowded and overrun with the plagues that take the children.

Will Self's The Book of Dave: A Revelation of the Recent Past and the Distant Future (2006) is another archipelagian dystopia. In the Recent Past, Dave is a forty-something London cabbie, maddened by dodgy anti-depressants and his separation from his son. Eventually he has his formless anger committed to a metal book, and buries it in his ex-wife's garden. The Distant Future is separated from the past by a tremendous but unexplained flood that has reduced England to an archipelago called Ing. A hateful new culture has been constructed based entirely on Dave's dug-up and endlessly copied rantings (by comparison, Jefferies' lakeside dwellers preserved Sophocles). Much of the dialogue is in 'Mokni', a descendant of Cockney spiced with Dave's cabbie lingo rendered either in phonetics or in a kind of text-speak: 'Ware 2, guv?' And a new London is being constructed based on Dave's cabbie's 'Knowledge', a kind of verbal map of the city. Genre fans will surely be reminded of Walter M Miller's A Canticle for Liebowitz (1960), which shows to similar satirical purpose a post-fall society constructing a religion based on a fragment of a shopping list, and Russell Hoban's classic Riddley Walker (1980), a story of a post-apocalypse England told entirely in an evolved tongue. I'm not aware if Self has acknowledged Liebowitz as a source, but he penned an introduction to an edition of Walker.

As sf Dave isn't terribly convincing; it's hard to imagine our descendants being quite so dumb. But Dave is at heart a dense, earthy portrait of London itself, a city seen 'spreading to the far hills of the south in brick peak after tarmac trough, blood-orange under the dying sun' (Chapter 14).

What about the rest of the country?

If London drowns, it's commonly imagined that upland England might become something of an archipelago. In Deluge (1928), by UK writer S. Fowler Wright, 'the slightest tremor' (Prelude) on a global scale has inundated much of the planet. Subsequently the protagonists struggle to survive on the scattered islands that is all that remains of the Cotswolds.

Deluge is quite remarkable for a book written by a 46-year-old English accountant in 1920 (though not self-published until some years later). The detail is relentless and graphic, the violence brutal, even the threat of rape explicit enough, and the final polygamy shocking. In some ways this book foreshadows not so much the polite Wyndhamesque British catastrophes of later decades but more the American survivalist dramas like Niven and Pournelle's Lucifer's Hammer (1977). We get the vivid catastrophe, the early struggle to survive in which the characters shed their 'civilised' restraints, and the crude emergence of a lawful community under the command of a strong man. There is a strong flavour of social Darwinism, as 'the men most fitted to the new conditions should become the fathers of the next generation' (Book IV, II). Again Wright follows Jefferies in his contempt for the British civilisation of his times, which he regards as 'the most elaborate system of mutual slavery that the world has ever known' (Prelude). As in so many such books you get the sense Wright is longing for something to come and smash everything up. Deluge won critical acclaim, and in 1933 was made into a Hollywood movie - with the action reset to New York, and a more conventional love story tying everything up neatly.

Islands and archipelagos need not be dystopias. In Christopher Priest's A Dream of Wessex (1977) the eponymous dream is a virtual-reality-like shared 'projection' of a future two centuries ahead in which Wessex has been severed from the mainland by 'catastrophic earthquakes and land subsidence' (chapter 4) and, in a world shared out between Islam and Communism, is a sunny, tourist-rich haven for the dreamers. Ambiguity abounds; when the dreamers try to return we are unsure what is real and what isn't, and in the end the dreamers transfer themselves permanently into what was initially presented as a fantasy.

This book was written at the time of Priest's stories of the 'Dream Archipelago', which Priest says he conceived of as 'more an idea than an actual place' but 'a kind of fusion of the Channel Islands and Greece, with bits of Harrow-on-the-Hill and St Tropez thrown in for good measure' (in the introduction to his collection An Infinite Summer, 1979). Priest's islands are places far from the centre of affairs, decided between great nations on the continents; thus in 'Whores' (1978) the Archipelago is used as a vast brothel by troops from either side, and in 'The Watched' (1978) the island's future is to be decided at the conclusion of a centuries-long continental war. Priest visited the Archipelago again in The Affirmation (1981), in which a Londoner, through writing a fictional biography of himself, is transferred to the Archipelago, in this imagining tens of thousands of seductive 'islands of the mind' (Chapter 22). We are left unsure what is real, who is sane.

Such stories bring out other aspects of islands in our minds, the exotic, the alluring, the remote. Islands are microcosms of evolutionary and social experimentation, from Atlantis to Utopia through Moreau's island and Golding's Lord of the Flies, to the nameless setting of Lost. An England reduced to an archipelago is the familiar made strange, the powerful reduced to the peripheral.

And what of the wider world?

A global flood is an ur-myth of our culture, and remains alive today. The Biblical Noah's story was enjoyably and earthily retold in David Maine's The Preservationist (2004; in Britain as The Flood), in which you get a real sense of how it would be to share in a universe with an intervening god, and restaged by Hollywood in Evan Almighty (2007). The latter has its fun moments, but as (the for me uncomfortably near-homonymous) Evan Baxter is bullied by God (Morgan Freeman) into building an ark to escape a flood caused by a corrupt congressman's dodgy dam, there is a sense of moral confusion, and the religiosity feels very alien.

There have been a number of genre depictions of global floods. I grew up with stories of pesky aliens mucking about with the weather. In the pages of the Gerry Anderson 'newspaper of the future' TV Century 21 (issues 45-51, November 1965 to January 1966): 'World Weather Chaos! Ocean Levels Rising', screamed the headline on issue 46, as the polar ice melted and the flood waters rose to thirty feet around Big Ben. And in a Captain Scarlet tie-in novel by John Theydon (1967) Mysteronised weather control systems drench London in a tropical storm, catching Scarlet and Rhapsody Angel in Trafalgar Square.

John Wyndham's enjoyable The Kraken Wakes (1953; pages numbers from the 1955 Penguin edition) is a watery reprise of Wells's War of the Worlds. A 'meteor' shower delivers invaders not to the land but to the ocean's abyssal depths; these may be visitors from a 'high-pressure' world, such as Jupiter. Though there are faint hopes that we can coexist with the 'xenobaths', as our respective realms barely overlap, there is a bleak Darwinian perspective: 'Any intelligent form is its own absolute; and there cannot be two absolutes' (p180). Wyndham ratchets up the conflict step by step as we move through a phase of conventional warfare - A-bomb depth charges versus 'sea tanks' - to a terminal phase in which the polar ices are melted. London's relentless drowning is told in pitiless detail: 'One day we walked down to Trafalgar Square … On the far side, and down as much as we could see of Whitehall, the surface was as smooth as a canal' (p221). In the end the 'xenobaths' are defeated, and the fraction of mankind left on the hilltops faces a future on a transformed world.

Aliens had flooded the continents previously, in War with the Newts by Czech writer Karel Capek (1936). The 'newts' are actually a race of underwater humanoids, intelligent but lacking high technology, until unwisely equipped with it by man. The newts are exploited and discriminated against. But the newts are ferociously fast-breeding, and once released by man from the natural confinement of their island of origin, they begin to fight back. Capek is a forward echo of Wyndham: 'There will not be enough room on our planet for two trends, each trying to rule the whole world. One of them will have to yield' (Book Three Chapter Six).

Eventually, under 'the Great Salamander', an apparent parody of Hitler, they rise up and begin demolishing the continents in order to create more of the shallow littoral waters that are their ideal habitat: 'The mountains will be demolished last' (Book Three Chapter Eight). The human governments, locked in their own arms race, keep providing them with the tools and explosives they need to do this, so that mankind brings about its own downfall. This is a dark and complex satire on the contemporary arms race, colonialism, racism and fascism. At one point a German scientist argues that the newts are actually a superior Nordic race who therefore have the right to claim lebensraum. There are few continuing protagonists; we view the events from without, but the relentless progression of mankind's foolish involvement with the newts is compelling.

JG Ballard's The Drowned World (1962) is something of a riposte to Wyndham. Anomalous solar flares cause intense heating. As the tropical zones bake and refugees flee north, London sinks into a gummy lagoon: 'The dense groves of giant gymnosperms [crowded] over the roofs of the abandoned department stores' (Chapter One). And in the dense heat nature reverts to archaic forms in an 'avalanche backwards into the past' (Chapter Three). Humans, stranded on this Triassic Earth, also begin to regress, recovering deep archaic memories locked in the sub-brain; we remember the swamps.

At first some fight the advancing heat; a military operation evacuates survivors to Greenland, and later a deranged looting party manages to drain Leicester Square. But all this is futile. The Drowned World is a kind of inversion of a Wyndham-esque disaster story, a convulsion of the psyche as much as the physical world, a narrative in which only the insane try to save civilisation.

But for all the heat there is an emotional coldness. There is only one female character, and no children at all, no families; in this self-consciously psychological study, the normal, instinctive, indeed genetic motivations for survival struggles are set aside. As the heroine of Wright's Deluge notes, 'It should be the children first - always the children' (Book V, XXIII). In the Ballard, without children, there is only solipsistic isolation.

More recent global floods have been caused, not by aliens, but by us, through human-induced climate change.

In Blue Mars (1996), the climax of Kim Stanley Robinson's mighty Mars trilogy, volcanism melts significant chunks of the Antarctic ice sheets, and the world suffers a seven-metre sea level rise. The novel's key tension comes from the plight of battered, flooded-out old Earth, swollen with overpopulation and looking with illogical envy at the 'empty' plains of Mars. In a long passage the Martians visit the flooded Thames estuary, host to a strange Brueghel-like intertidal culture which lives off the submerged pickings of the past. 'Boxes, furniture, roofs, entire houses' come floating down the river: 'London, washing out to sea' (p219 of the 1996 Voyager paperback edition).

A global flood caused by greenhouse-gas ice cap melting was the inciting event in Steven Spielberg's AI: Artificial Intelligence (2001). Cities are drowned, populations uprooted and starved. Enclaves of the rich survive only through draconian limits on reproduction, and so robots are used as slaves, companions, and substitute children. The rejected robot boy David, in his quest to find the 'Blue Fairy' he thinks will make him a real boy, visits a beautifully shot flooded Manhattan where Liberty's torch protrudes above the waves, and yachts sail among the skyscrapers - including, hauntingly, the World Trade Center, not yet downed when the film was made, their presence turning the movie into a vision of an unrealisable future. David is trapped underwater in the flooded ruin of Coney Island, undying, praying for centuries to a wooden statue, before the remote technological descendants of his own kind restore him to a world empty of humans. It is eerie to see the unloved robot boy drifting among the rotting carcass of our own world.

Floods like Wyndham's and Spielberg's have a natural upper limit; the sea level rise must surely stop when all the polar ice has melted. But in the ultimate imagining the flooding just keeps on going, just as it did for Noah, until 'all the high hills, that were under the whole heaven, were covered' (Genesis 7:19). And that's precisely what Garrett P Serviss delivers in The Second Deluge (1912).

We are a century or so ahead of the then present, in a world where horses have been driven almost to extinction by 'the honking auto' (chapter 7). Wealthy scientist Cosmo Versal spots the approach of a watery space nebula, and predicts that the earth will be drowned to a depth of six miles. The devastation is vividly described: 'It was a terrible thing to see the drowning of London,' says King Richard IV (chapter 17). In his Ark Versal sails over drowned Eurasia, encounters a French submarine called the Jules Verne, and watches Everest's summit submerge. The relentless step-by-step advance of the flood is well worked out - you can follow its progress in an atlas. And if the language has dated the grandeur of the imagining has not. And in this novel from a time of American optimism there is a happy ending when the land uplifts, and the Ark falls, not on Ararat, but on Pike's Peak.

We like to sit cocooned in our seemingly changeless world, and thrill to tales of somebody else's deluge, biospheric porn. But there were many Noahs, from the Sumerian Ziosudra to the Akkadian Utnapishtin of the Gilgamesh saga. It may be that we are evoking some deep Ballardian race-memory of a Noachian past, or of the days post Ice Age when huge climatic disturbances really did plague the Earth.

After the nineteenth-century geological revolution most of the supposed evidence for the Flood was ascribed to the Ice Ages. But in recent times there have been suggestions that there really may have been enormous floods (see Noah's Flood by William Ryan and Walter Pitman, Simon and Schuster, 1998). For instance, when the ice caps receded twenty thousand years ago, the rising ocean broke through a natural dam in the Bosporus Strait to fill the present Black Sea in just a few years. The beaches receded at a rate of a mile per day.

What is remarkable about Noah's legendary response to such a disaster is that it was technological. In earlier times, Noah's rootless hunter-gatherer ancestors would simply have walked away from the flood, and within a generation forgotten it. But now, around the Black Sea, the people under threat were farmers. To save his livelihood Noah built something, just as we would today. And we remember him still, for he was like us.

If Britain Had Fallen

The fourth and last novel in my Time's Tapestry series (Weaver, Gollancz, February 2008) is an alternate history in which Hitler invades Britain.

Of course to say that this sort of thing has been done before is an understatement. The venerable Clute-Nicholls Encyclopaedia of Science Fiction (1993) has an entire entry dedicated to 'Hitler Wins', and non-fiction books like the What If? series (ed. Robert Cowley, 1999 onwards) contain many essays on how the Nazis could have run their war differently. Even Star Trek let the Nazis win once, in Harlan Ellison's original-series episode 'The City on the Edge of Forever' (1967).

I've published some Hitler-wins short fiction before myself, including 'Mittelwelt' (1994, collected in Traces (1998)), 'First to the Moon!' with Simon Bradshaw (2001, collected in The Hunters of Pangaea (2004)), and most recently 'The Pacific Mystery' (2006, in The Mammoth Book of Extreme Science Fiction ed. Mike Ashley). Here I was lured by the deadly gleam of technological what-ifs; my stories feature Nazi spaceships and rocket-planes and nuclear aircraft.

So, more than sixty years after the end of the war, is there anything left to say about victorious Nazis? As you might anticipate, my answer to that question is 'yes' - and in particular, how Hitler might have defeated Britain, and the consequences if he had.

Hitler's planning for 'Operation Sea Lion', the invasion of Britain, has been well documented, not least by Churchill himself in Their Finest Hour, the second volume of his monumental six-volume history of the war (1949), and by Peter Fleming in Invasion 1940 (1957).

Sea Lion was no mere paper exercise. Throughout the summer of 1940 Hitler had river barges and other craft assemble in the Channel ports, while the Wehrmacht practiced beach landings, and the Luftwaffe pounded the airfields and radar stations of southern Britain. 'It seemed certain the man was going to try,' Churchill wrote (in Their Finest Hour).

But the barges would have wallowed in the Channel surges, the British always had overwhelming naval superiority (see Derek Robinson's Invasion, 1940, 2005), and the RAF, with many stations far out of range of the Luftwaffe's Messerschmitts, could not have been defeated entirely. On the German side there was always inter-service controversy over the plans, and Hitler was already turning east to his planned assault on the Soviet Union. In the end the Luftwaffe switched tactics by beginning the 'blitz' on London on 7th September 1940, thus allowing the RAF to recover. The invasion was postponed to later in the year, then to 1941, before being abandoned altogether.

Could it have gone differently? Fleming speculates that the Germans might have achieved a successful invasion if they had attempted it earlier, with even a small force in early June 1940, when Britain was reeling after Dunkirk. Some of Hitler's generals argued for this at the time, following a general principle of pursuing the defeated.

My own turning point is Dunkirk. On 24th May 1940 Panzer General Heinz Guderian, only ten miles from the trapped and exhausted British Expeditionary Force at Dunkirk, was ordered to desist from a final assault. As a result the bulk of the BEF was able to evacuate. The reasons for this order remain obscure: perhaps to do with concerns that the defeat of France was yet to be completed, or Hitler's hope that Britain might yet make peace, or Goering's jealous desire that the final victory should go to the Luftwaffe.

Certainly Dunkirk was a significant morale boost for Britain. In the darkest hours of the collapse of France, Churchill, in his famous speech to Parliament on June 4th 1940, was able to use the 'miracle of deliverance' of over three hundred thousand men as a basis for his rousing declaration that Britain would fight on: 'We shall never surrender.' As for the Germans, Guderian himself (in his book Panzer Leader, 1952) said he believed the order to hold back was a mistake, and that 'only a capture of the BEF … could have created the conditions necessary for a successful German invasion of Britain'.

But what if Guderian had been unleashed at Dunkirk? Possible alternate outcomes of Dunkirk have been analysed by, for example, Andrew Roberts in his essay in Virtual History, ed. Niall Ferguson (1997). Weakened and demoralised, the British might have lacked the determination to destroy the French Navy in its Algerian ports on 3rd July 1940. In reality this was a strikingly belligerent action that changed the balance of naval power in the Channel in the months that followed. The German commanders, with an invasion a more realistic possibility, might have worked more coherently towards it. In particular if the Luftwaffe's resources had remained focussed on the goal of invasion the Germans might have achieved at least local air supremacy over Kent and Sussex.

And if the invaders had landed? What then?

Horrifying speculations about Nazi victories were in fact published even before Hitler had won anything outside the borders of Germany. Murray Constantine's Swastika Night (1937), for example, was a nightmare of a possible then-future in which Hitler is deified and women are kept as breeding animals. As for Britain, accounts of a successful Nazi invasion of Britain appeared even before the Second World War was over, for example the novel When the Bells Rang by Anthony Armstrong and Bruce Graeme (1943).

Even if the Germans had landed, their victory was not assured. Richard Cox's Operation Sea Lion (1974), based on a war game played out by veterans from both sides, post-predicted a German failure; the crucial issue was the Germans' lack of logistical preparation compared for instance to the Allies' planning for D-Day. A similar recent study is Martin Marix Evans' Invasion! Operation Sea Lion 1940 (2004). On the other hand Norman Longmate's If Britain Had Fallen (1972) is a careful account of a successful invasion.

A dismal portrait of a post-invasion occupied Britain, sketched by Longmate (1972), is given in Len Deighton's novel SS-GB (1978). The Battle of Britain went badly; Churchill surrendered in February 1941. In November of that year, in a dingy, rain-swept, occupied London, a British copper finds himself being led from a murder investigation into a conspiracy involving conflict between the German army and the SS, and a plot to smuggle the ailing King George abroad to America. A copper is a good choice of viewpoint. Under Nazi occupations the civilian authorities were expected to implement their rulers' directives, and the police were in a particularly ambiguous position; after all a crime was still a crime. Deighton is very good on the grubby detail of occupied London, the shabbiness, the rationing among the wreckage of a lost war, the constant fear, the reprisal executions and shipping-out of loved ones to forced labour camps - the petty humiliations of a subject people. And the geopolitical calculations of the Americans as to whether it's worth supporting the British are even more humiliating than the Nazis' arrogance.

Christopher Priest's justly lauded Clarke winner The Separation (2002) portrays a Britain defeated without invasion. Priest begins with a different turning point: an armistice between Britain and Germany in 1941. The argument is similar to that developed in the 1990s by revisionist historians like Alan Clark and John Charmley. Britain's victory in 1945 was Pyrrhic, they say; we could have got out of the war much more cheaply. In early 1941 the German attack on Britain, while ferocious, was stalemated. Hitler had muttered sporadically of his longing for peace with Britain, and Rudolf Hess, a senior Nazi, even flew to Britain, apparently without authorisation, to try to broker a peace deal. The terms might have been a cessation of hostilities between Britain and Germany, a German guarantee to leave Britain and the empire alone, and Britain to allow Germany a free hand in Europe and Russia. The idea is that Britain could stand back as Germany and Russia destroyed each other and emerge powerful and wealthy in a post-war world. The revisionists argue that the deal founded because of Churchill's lust for blood and defence of his own position. This is the Churchill unambiguously dramatised in Separation, whom the characters call a 'warmonger', 'that arch-manipulator of twentieth-century history', and so on. In the book Churchill is dragged to the signing table. The story is of twins, one a conscientious objector, the other an RAF pilot, whose lives diverge into alternate realities after this tipping point. It's a wonderful book.

But could such a peace deal really have offered 'a chance for stability and harmony'? I doubt if the British would have settled, having survived 1940 and the Blitz; they were taking the fight to the Germans, not least by mounting bombing raids on Germany itself. The British thought of themselves as a great power and expected to win wars, not lose them. Also there was genuine moral revulsion at the Nazis. The thought of a shameful peace was just not the national mood, I don't think, even if there was no end in sight.

And there is no guarantee the Nazis would have kept any pact they made - indeed their assault on Russia was in defiance of a Hitler-Stalin pact. Hitler's pronouncements about Britain were contradictory; he mused about racial affinities between the British and the Germans, but would also pronounce, such as in October 1939, that 'the German war aim … must consist of the final military defeat of the West'.

Even if the pact had stuck, would a world in which either Nazi Germany or Stalin's Russia 'won' all of western Europe really have been a better one than ours? Britain would have ended up a satellite of a grotesque continental polar power. I believe that Churchill, a historian himself who always took the long view, had it about right about the Nazis. As he told the Commons in 1938, that 'there can never be friendship between the British democracy and the Nazi Power, that Power which spurns Christian ethics … [which] uses, as we have seen with pitiless brutality the threat of murderous force'.

Surely a shabby peace deal in 1941 would have resulted in a world (even) worse than the one we inhabit. But this is an opinion; we'll never know. Perhaps Priest's greatest achievement is that he sets out such a troubling moral conundrum so clearly; of all the what-ifs this may be the one to linger in the conscience the longest.

If Britain had fallen or been neutered, what about the course of the rest of the war - and the fate of the rest of the world?

Hitler's eventual defeat might have been much less certain. Fleming speculates that without a western front the German assault on Russia could have been launched earlier and with more resources, and later without Britain as a launch platform the Allied invasion of Europe would have been much more problematical. On the other hand the US might still have supported Russia in its struggle against the Germans - an awful lot of the resources of the final victory in the east came from the US.

Possibly the most significant mainstream attempt to portray a Hitler-wins global future is Robert Harris's Fatherland (1992). This is set in Berlin in a different 1964 in which Hitler won all of Europe (though not Britain) by means of victory in Russia in 1943, following which he forced an unequal peace with Britain in 1944. At the heart of the Reich is a Berlin, transformed by Speer's mad monumental schemes, preparing to celebrate Fuhrertag, an ageing Hitler's birthday, while Britain's King Edward VIII sends congratulatory messages and the cynical American President Joseph Kennedy (JFK's father, and a defeatist US ambassador to London) negotiates détente. As in Deighton, Harris's viewpoint character is a Berlin cop, in fact an SS officer, who, starting from an investigation into a murder, uncovers a conspiracy among the top Nazis to implement what we know as the Final Solution - of course, covered up in this alternate reality.

The novel is heartfelt, but it feels a little unlikely as the SS man grows a conscience: 'What do you do if you devote your life to discovering criminals, and it gradually occurs to you that the real criminals are the people you work for?' But Fatherland does dramatise the grandiose, insane plans Hitler and his cronies had for Europe once they won the great game: the sterilising, the racial cleansings, the vast colonisation pushes east into lebensraum.

In Brad Linaweaver's Moon of Ice (1988) the Nazis won by getting to the atom bomb first; they even nuked the concentration camps. This novel is an effective dramatisation of the mad mysticism at the heart of the Nazi project, as developed by Himmler and his SS archaeological institute the Ahnenerbe. The Aryans were supposedly the product of a cosmogony in which successive falls of ice moons to the Earth would eventually result in the return of a race of world-building giants. The story, to do with a crackpot plot to cleanse the world of everybody but the blue-eyed and blond, is effectively told from the point of view of Goebbels' rebellious daughter - and from that of Goebbels himself, who comes across as sane amid the Nazi madness and surprisingly sympathetic, if cynical. As for the baroque insanity of the cosmogony, as the mad-scientist villain character says, 'They are innocents in search of an imaginary past … They think that state-of-the-art science is the discovery of the four elements: fire, earth, air and water.'

An even more compelling exploration of Nazi madness is Norman Spinrad's The Iron Dream (1972). In an alternate world, Hitler moved to the US to become a sf writer, while the Soviet Union conquered Europe. Spinrad gives us the whole of Hitler's last novel, called Lord of the Swastika. This is a kind of sword-and-sorcery wish-fulfilment version of Hitler's real-world career, in which Hitler's Aryan avatar, 'a tall, powerfully built true human in the prime of manhood', wields his phallic truncheon to lead his nation of the last true humans to racial victory in a post-apocalypse world of 'mutants and mongrels'. The novel-in-a-novel is hilariously funny, laying Hitler's chilling but oddly comical psychology bare, and yet never once fails to take itself seriously.

A final touch is an academic afterword in which it emerges that Swastika won the 1955 Hugo, and became cult reading. Spinrad isn't just lampooning Nazism what his cod academic commentator calls 'the considerable body of pathological literature published within the science-fiction field'. Dream is brilliant and bonkers; I wonder if it could be published today.

There are rather shameful factors in our morbid fascination with the Nazis, such as what the Encyclopaedia article calls their 'cheap aesthetic appeal'. I once saw a Nazi-era steam locomotive in a Berlin museum; with its shining black livery, even that loco looked glamorous.

But there is also a compelling drive to understand, I think, what it is that makes people do what the Nazis and their followers did. We stare at the Nazis rather as we gaze at serial killers. Is there a psychological profile of a dictator? It must involve a sense of grievance or entitlement, ruthless ambition, arrogance - and above all a lack of empathy. Napoleon once spoke of his fallen soldiers as 'small change'. (Churchill, on the other hand, for all he suffers accusations of inhumanity, would show visible distress when told of losses.)

It is this lack of empathy above all that Philip K Dick homes in on, in his Hugo-winner The Man in the High Castle (1962). Defeat follows the assassination of President Roosevelt, and much of mainland America is partitioned between the Nazis and Japanese. There are no grand conspiracies here; this is a book of small lives and small actions and humiliation, with defeated Americans, 'white barbarians', unconsciously adopting the mannerisms of their conquerors. But the characters are aware that theirs is the 'wrong' reality; our world is glimpsed, imperfectly, in the pages of an alternate-history novel contained within the novel we read.

Dick always majored on empathy. The androids of Do Androids Dream of Electric Sheep? (1968) crucially lack empathy, the one quality that enables them to be detected. Norman Spinrad once told me a story that fascinated Dick of a Nazi concentration camp officer who complained at being woken by the noise of crying children. So in The Man in the High Castle Dick wrote of the Nazis in terms of madness, specifically schizophrenia, and in terms of decay and disease and violations of nature: 'The madmen are in power … German totalitarian society resembles some faulty form of life, worse than natural thing.' It would be too easy to diagnose the Nazis as a bunch of glamorous zombies, like a race of Mysteronised Captain Blacks. Dick forces us to face the fact that the Nazis were human.

The twentieth century is over, and is becoming parcelled into history, a spitting package of blood and moon dust. Already the first histories are being written of the century as a whole, such as Niall Ferguson's The War of the World (2006). Perhaps it is this distancing that will give us the perspective to gain a proper understanding of the Nazi horror.

But in the meantime, though Hitler lost his war, he won another hot competition. In a century which starred Pol Pot and Stalin among many other horrors, Ferguson identifies Hitler's Nazis as the worst evil of all.

Living at the North Pole of Mars

First published in the BSFA's Matrix magazine, January 2007.

One of my many hats, in this case a space-cadet peaked cap, is that of a Fellow of the venerable British Interplanetary Society. From June 2004 I worked for over two years with the BIS on a design study for a manned base at the Martian north pole. This is in a long tradition of similar studies by the BIS, which produced a design for a lunar lander as early as 1939, and for an interstellar probe in 1978. It is a weighty study; project leader Charles Cockell is a professor of astrobiology at the Open University.

For definiteness we imagined a five (Earth) year stay, from 2037 to 2042. I worked on historical and science aspects, particularly how to extract and interpret a core from the Martian ice cap. It did me good, I think, to work in a team for a change, and to do something resembling real science. The results of our work have been published as Project Boreas: A Station for the Martian Geographic North Pole, ed. Charles S. Cockell (British Interplanetary Society, 2006) (and Arthur C Clarke and I are planning some scenes set at the pole of Mars in our next Time Odyssey collaboration (Firstborn).

What sort of place is the Martian north pole? Cold and dark: Mars has the same sort of axial tilt as Earth, so just as on Earth the north pole enjoys half a Martian year of perpetual daylight, and then half a year of darkness - that is, about a full Earth year of night.

As for the weather, Mars is a bit like high-altitude terrestrial deserts: when the sun goes down, it gets cold fast. At the pole, as soon as the sun disappears at the autumn equinox, a 'snow' of carbon dioxide ice nucleated on dust and water-ice crystals starts to fall. But Mars's atmosphere is mostly cee-oh-two: thus on Mars, in the winter, the air snows out. Ultimately you get a dry ice layer 1-2 metres thick, and throughout the winter there is a steady low-speed wind into the polar regions to replenish the lost air. In the spring the sun's heat sublimates away the carbon dioxide, leaving behind a residue of water ice with dust and other contaminants, thus adding a layer to a permanent water-ice cap.

The permanent cap has features unlike anything on Earth. From space it looks like a weather system, with the ice cut through by 'spiral canyons', thought to be formed by a combination of ice flow and wind effects. And through steady sublimation and deposition the canyons migrate with time. The polar cap is a self-organising system a thousand kilometres, a frozen storm which spirals with the centuries and breathes with the millennia.

In Project Boreas we explored the challenges of living at the Martian pole. Although Dan Dare (in a 1951 Eagle story) once holidayed at the Hotel Mars-Astoria, 'one of the glass-domed airtight winter-sports hotels at the North Pole of Mars', sadly we found it would be a sort of multiplication of the usual difficulties of life on another world, the confinement, the limited resources, with the unique challenges of polar exploration on Earth. You would face months of darkness stuck in a dome on a featureless white surface, an environment like a sensory deprivation tank.

So why would you go there? Perhaps for the resources. In the first realistic study of how to send humans to Mars, the Mars Project of 1953, Wernher von Braun proposed landing winged ships on one of the polar ice caps, chosen for their smoothness: the 125-tonne 'landing boats' needed runways. In the 1990s NASA scientist and sf writer Geoff Landis proposed a first landing at a Martian pole for ease of access to water in the surface ice; temperate-zone landings would have followed later, because there you would have to drill for your water.

And, aside from the sheer challenge, there's good science to be done. That's why NASA, in August 2007, launched its Phoenix lander to visit the polar cap. You can't understand the Martian climate without studying the poles, where fully one-third the atmosphere freezes out each winter. And then there is the prospect of extracting an ice core from the permanent cap, which might contain a climate record and much else besides: Chinese and American astronauts drilled in search of life at the Martian north pole in The Secret of Life by Paul McAuley (2001).

On Mars as on Earth, ice caps are built up year by year, each layer trapping a 'snapshot' of climate conditions. Terrestrial ice cores have yielded climatic records with an accuracy of a year reaching back some 100,000 years into the past. The principle is just the same on Mars. Some scientists have already sought a correlation between changes in Mars's axial tilting and ice layers visible to the Mars Global Surveyor orbiter.

Extracting ice cores on Mars is going to be a bit of a challenge, however. The Martian ice cap is three kilometres deep. Over 1989-1993 a programme sponsored by the US National Science Foundation drilled to a similar depth through the Greenland ice cap summit, in a five-year project involving 50 people, with heavy lifting provided by the US 109th Air National Guard. On Boreas we'll have just ten astronauts with plenty of other things to do, and the usual spaceflight restraints on mass and power.

In the end we concluded sadly that with this generation of technology we were restricted to much smaller gear - drill rigs you could disassemble and cart around on a rover trailer - and could only anticipate reaching depths of a few hundred metres. We'll be more like Lonnie Thompson, who since 1983 has been taking ice cores from tropical glaciers (see Mark Bowen's Thin Ice: Unlocking the Secrets of Climate in the World's Highest Mountains, 2005). Thompson operates at altitudes too high for heavy-lift support; he carries his gear and ice core sections on the backs of graduate students and other draft animals.

Anyway, on Mars, being restricted to a few hundred metres isn't the end of the world. Deeper strata are exposed in the walls of the spiral canyons, and you could sample them that way. And the ice layers on Mars are a lot thinner than on Earth. In Greenland, say, you get an annual snowfall tens of centimetres thick. On Mars the residual water-ice layer is less than a seventh of a millimetre, annually. So you can reach deep time in just a few metres of core.

How could you interpret a Martian ice core? There's a lot we don't know, such as how to date the layers absolutely, or how to read temperatures from features of the ice such as through isotope content. But there are some things we can anticipate. Global dust storms occur every few decades. A brown stripe a few centimetres down would be a trace of the brown-out Mariner 9 found when it arrived in orbit in 1971. Ten centimetres down would be relics of the radiation washed over the planet by the Crab supernova a thousand years ago. Every metre or so there would be a layer of micrometeorites; every ten or a hundred thousand years Mars is hit by an object massive enough to spread debris even to the poles. And a big metre-scale striping in the core would correspond to a nodding of Mars's polar tilt that occurs every hundred thousand years.

Our report is pretty comprehensive, I think, covering base design (inflatable modules on stilts, to keep out of the dry ice snow), life support, local resource usage, IT and comms aspects (you can't see synchronous satellites from the poles), science goals, psychology - and, most fascinating, exploration objectives, including jaunts down those spiral canyons. We were cautious in our technical projections, and there's something of a paradox here. The purpose of a study like this is to show that a Mars polar base is feasible with (more or less) present-day technology, but of course by 2037 technological advances may have rendered our assumptions invalid. In particular you could imagine smart robots capable of running their own science programmes making it unnecessary to send humans at all.

In the end, I suspect, people will go to the Martian poles for exploration and wonder. Project leader Charles Cockell is considering a Ranulph Feinnes-style unsupported assault on the Martian north pole: no domes, no robots, just one human being with spacesuit and sled. But that's another story.

How William the Conqueror might have lost at Hastings

First published in the BSFA's Matrix magazine, November 2006.

October 2006 was an anniversary - the 940th in fact - of one of the great turning points of British history, indeed world history, the Battle of Hastings.

I'm old enough to remember the last really significant anniversary, the 900th in 1966, when I collected the handsome commemorative postage stamps featuring the Bayeux Tapestry. And back in 1966 I glimpsed the 1000th, in the pages of the marvellous 1960s comic TV Century 21. This newspaper from precisely 100 years in the future told (from issue 87 onwards) how in 2066 supersub Stingray will take part in a naval carnival to celebrate the millennium of Hastings, viewed by the World President.

My novel Time's Tapestry 2: Conqueror is a what-if exploration of Hastings. Suppose William hadn't conquered? This seems an obvious turning-point springboard for alternate histories, a decisive battle whose outcome changed the course of all subsequent history. Not only that, the outcome of the battle itself seems very contingent (if that arrow had fallen just a bit to the left or right...). But surprisingly enough, according to the wonderful Uchronia website (, which aims to catalogue all alternate-history speculations, there have been only two previous what-if studies of Hastings, and both non-fictional at that - although Uchronia missed Doctor Who...

Hastings was the climax of a dispute over the succession to King Edward the Confessor, who died in January 1066. Edward was a descendant of Alfred the Great. The witan, the English ruling council, elected Earl Harold Godwin as Edward's successor.

But earlier in the eleventh century England's throne had been occupied by Cnut, a Danish monarch who had made England a southern province of a Baltic-Danish maritime empire. As a result the Norwegian king Harald Hardrada had his own claim to make to the throne. Harold Godwin himself, the witan's king-elect, was in fact half-English and half-Dane, embodying the polyglot nature of pre-Norman England after centuries of Viking incursions.

And then there was William 'the Bastard', Duke of Normandy, to whom Edward was related. William's claim to the throne was tenuous, but he claimed Harold Godwin had sworn an oath of allegiance to him. Whether this was just a pretext or not, William prepared the largest invasion of Britain since the Romans.

Meanwhile Harold had fallen out with his brother Tostig, who cast in his lot with Hardrada. While Harold was waiting in the south for the Normans, in September 1066 Northumbria was invaded by Hardrada and Tostig. Harold marched the length of England to defeat Hardrada at Stamford Bridge, outside York. Then he was forced to march south again and, under his Fighting-Man banner, faced William. Despite the exhaustion of the English army, the battle was long and close-fought...

There are lots of ways things might have gone differently, and not just on the field of Hastings. William's upbringing had been hazardous; he might not even have survived to see Hastings. Or, what if Harold hadn't fallen out with his brother? Perhaps he could have been spared the fight with Hardrada and saved his energies for William. At one point in the battle itself the Normans were forced back - but Harold didn't pursue them, sticking to the solidity of his shield wall. What if he had been just a little less cautious? And what if that famous arrow had missed Harold's eye?

Even after Hastings, the Normans' grip on England might have been loosened. The English fight-back is known to us mostly through the romantic legend spun out in Charles Kingsley's Hereward the Wake (1866). But it is becoming clear that the native resistance to William in this period was considerable, having some similarities to the resistance in Nazi-occupied France nine centuries later (see for instance Peter Rex's The English Resistance, Tempus, 2004).

The discontented and rebellious retreated to the wild places. Wearing green or brown for camouflage, they struck at the Normans guerrilla-style, melting away into the rough ground where the Normans' heavy mounted cavalry could not follow. They called themselves wildmen. The Normans called them silvatici, men of the woods. Perhaps they inspired stories of Robin Hood in his 'Lincoln Green', and a folk-memory of their exploits may linger even today in the 'Green Man' motif of pub signs and church carvings.

The wildmen were capable of harassing the Normans, but (like the French in the 1940s) didn't have the strength to drive William out without outside help. In the end, of course, William went on to crush the likes of Hereward, and English resistance to the Conquest was effectively ended.

Does it matter? Was the outcome of Hastings really so decisive?

Certainly, argues historian Cecelia Holland (see her essay in More What If, ed. Robert Cowley, Pan, 2002). Under Cnut England had been part of a northern community that stretched from Kiev in Russia through Scandinavia and even to Vinland, the Viking colonies in America (Newfoundland down to Maine). If Harold had won and England could have stayed 'northern', its more southern ports could have kept open the trading links to Vinland, which were otherwise lost through a global cooling at about this time. An Anglo-Scandinavian confederation might have spanned the globe from Asia in the east as far as America in the west, and a new empire of the north would have overshadowed the southern Latin world. Viking dragon ships could have sailed the Hudson and the Mississippi. There might even have been parliaments like Iceland's 'althings': democracy in North America centuries before 1776. But William won. England was drawn back into the realm of the Latin south, and the northern empire was still-born.

Uchronia lists Holland's study, but the only other reference there is a chapter in a book called 1066 by Robert Silverberg, writing under the pseudonym Franklin Hamilton (Dial Books, 1964). This is a historical study of the events of the year, but the closing chapter contains what-if speculations. If William had lost, Silverberg thought, a fragmented England, always prone to in-fighting among English earls, might have fallen under France's influence anyhow. Or if Harold had cemented his rule England might have been rather more isolationist. Perhaps North America would have been predominantly a French colony.

And what of Doctor Who?

In the serial 'The Time Meddler', written by Dennis Spooner (who incidentally also wrote for Stingray) and broadcast on the BBC in 1965, the Hartnell Doctor finds himself on a Northumbrian beach, just ahead of Hardrada's invasion. In a thrilling moment his companions find a wrist watch in the sand … Another of the Doctor's people is here disguised as a monk, with his own TARDIS, intending to alter the course of 1066 by blowing up the Viking fleet with an atomic cannon.

These aren't yet Time Lords - the term wouldn't be introduced until 1969 - but the Doctor's people have a folk wisdom about the dangers of meddling with time. The Monk's motives are actually benign, however, and his counterfactual plotting is reasonably plausible. Harold would have made a good king, and without the distraction of territorial wars in France England would have advanced quickly, with jet liners in the fourteenth century and television by Shakespeare's time. But the Doctor warns of the dark side, with medieval kings being unleashed on the cosmos. In the end the Doctor saves history and strands the Monk in 1066 (though you would think that even without technology the Monk's knowledge of the future could be just as perturbing for history).

In the real world, after the Conquest William studded the country with his brooding fortresses, and extirpated the old upper class. If you were English your language was suddenly an underground tongue, and you found your home sequestered as some foreign lord's hunting grounds. Once Northumbria (where I now live) had been the greatest English kingdom. Now it was the source of much resistance. William was crowned on Christmas Day 1066; he celebrated Christmas 1069 in the burning ruins of York, in the midst of a 'harrying' from which the north of England wouldn't recover for fifty years.

Cecelia Holland remarks, 'Hastings deserves its reputation as the greatest battle in English history, and a major turning point in the history of the world.' She's surely right. If it had gone otherwise in 1066, subsequent history would have been so different it's difficult to judge which outcome would have been 'best'. The Normans did build on the solid foundations of the English-Danish kingdom to make England strong. But perhaps we could have been spared their brutality.

By now the Norman invaders are thoroughly assimilated; most of us are probably half-Norman. Yet there is a lingering sympathy for Harold and his English followers. When I visited a Battle of Hastings re-enactment at Battle, Sussex in 2005, I found that the spot where Harold fell, still marked by a stone, had been strewn with flowers and Fighting-Man flags.

The origin of the Destiny's Children series.

First published in the BSFA's Focus magazine, November 2005.

Resplendent was (in the noble tradition of Douglas Adams) the fourth book in my 'Destiny's Children' trilogy.

This series, published in the UK by Gollancz and in the US by Del Rey, is about the possibilities of human evolution. The first novel Coalescent (2003) is set in the present day, with the hero George Poole uncovering a human 'hive' in the catacombs of Rome. Exultant (2004) is set 25,000 years in the future, when humanity is locked in a galactic war. Transcendent (2005) follows up both the previous books, as George Poole's nephew Michael deals with climate-change disasters in the near future, amid an intervention from a far future beyond the Galaxy war. Resplendent (2006) is a 'fix-up' of short fiction (up to novella length) set against the background of this future history.

Where did this series come from, and how did it end up in its final form?

The answer is complicated; there were many inputs. But one starting point is Australia, which I visited in 1999 for the Melbourne worldcon. I was very struck by my first one-to-one with a 'roo in a nature park north of Melbourne. Close to they seemed extraordinary, with those remarkable levered back legs. To my (non-biologist's) eye kangaroos were examples of alternative bio-engineering, like aliens from the imagination of Niven, Vinge or Jack Cohen.

Of course kangaroos and the rest of the native fauna evolved differently from 'us' because of Australia's long isolation from the other continents. Such experiences gave me a wonderful sense of deep time, and of the reality of evolution. (One outcome of this inspiration was to be my novel Evolution (2002).)

Another input was a visit to Japan in 1997 for a convention there. I'm lucky enough to be sold in many countries, and without wishing to stereotype, I've found that different national markets respond to different types of book. The French, for instance, liked the alternate-history politics of Voyage (1996). The Japanese, though, seemed to like the super-science of my earlier 'Xeelee' sequence, from Raft (1991) to Ring (1994), and the fix-up collection Vacuum Diagrams (1997). I always wondered if the Japanese felt they were already living in the near future compared to Europe and America. My Xeelee sequence, which began with my very first published fiction, 'The Xeelee Flower' (Interzone 1987), had been fruitful for me, but by the time I'd completed Vacuum Diagrams I'd come to feel enclosed by the whole thing, tied down by my own continuity. But the kindly enthusiasm of the Japanese fans made me think again.

In the Xeelee chronology humanity expands out from Earth into a universe chock-ful of alien life and cultures, in the manner of Niven's 'Known Space', perhaps. The story simplifies as we become dominant, save for one foe: the aloof and supremely powerful Xeelee. At last we fall back, and after a million years we are defeated, our last survivors imprisoned in a bubble universe.

The earlier material had told the story of the beginning and the end of this saga. But now I began to think about the 'middle bit'. How could mere humans actually fight an interstellar war? For one thing, every FTL starship is also a time machine, an awkward consequence of special relativity. I don't believe this has been handled adequately before. I drew on my evolutionary speculations too. Even with FTL technology, war fronts spanning thousands of light years would surely translate into engagements lasting thousands of years. The human species is only a hundred thousand years old; if it lasted long enough, surely the war itself would become an evolutionary pressure. Perhaps in such a war the ultimate form of humanity would be the child soldier.

So I started to try to figure out in more detail how humanity's rise and fall could come about, and how humanity might be shaped in response. After a couple of months I began to carve out specific ideas for short stories, the first being 'Cadre Siblings' (Interzone, 2000), the start of the sequence of stories that would result finally in Resplendent. For me nothing crystallises ideas so well as actually writing something down, and the short fiction let me feel my way into a complicated universe.

Meanwhile, however, I was gathering other ideas. I try to keep my mind open to a range of inputs, for you never know where an idea is going to come from or where it might lead you. In this case I attended a rather heavyweight conference on human evolution in London, at which one speculative paper described the Catholic Church as a hive(!). Well, one manifestation of a hive, as daughters give up their own chance of reproducing to sustain their mothers' babies, is skewed reproductive strategies, and there are certainly plenty of those in the Church … The notion struck me particularly as I was born a Liverpool Catholic, and though I'm now lapsed I remain fascinated by the Church and its implications.

Of course hive minds have been done before, from HG Wells's Selenites in The First Men in the Moon (1901) to the Borg of Star Trek. But I quickly learned that the sociobiologists' explanations of hives in nature have moved on a lot over the last few decades. And I read up on modern ideas of 'emergence', in which, like ants in their colonies, we humans too are all embedded in mass, mindless systems, from traffic jams to the economy, which arise out of our individual decisions and actions, but are out of control of any of us. These developments hadn't been covered (as far as I knew) in sf to that point, and I felt it was time to visit the hives once more. I began to consider a book describing the survival of an early-Christian hive from Roman times to the present day. This would have more of the feel of a horror novel, I thought, compared to the space-operatic glitter of my Xeelee war idea.

And then (with apologies for the name-dropping) out of the blue I was contacted by Sir Arthur C Clarke, with whom, in parallel to all this, I was developing ideas for our 'Time Odyssey' collaborative series. On 27 January 2001 Clarke sent me a portion of a letter from Olaf Stapledon to JBS Haldane (!), dated 1945:

'Your utopia is a very exciting one. Why, though, must the intelligent animals forget the brutality of the past? I want everything to be fully remembered, everything to be fully cognized … For me the final utopia is not simply the thing for which past misery is a necessary means, that when it is reached the past may be forgotten. The final utopia must somehow redeem the past [my emphasis], or else be something less than utopia. How it can do so I naturally don't know, but at least it must be aware of the past, so that the past can at least be redeemed in the utopia's awareness, as a valued part within the past-present-future (or eternal) whole.'

Clarke wrote, 'Dear Stephen - This phrase [emphasised] haunts me - does it give you any ideas?' It certainly did, as redemption was another echo of my Catholic past. (In fact Stapleton himself dramatised this idea to some extent in his Last and First Men.)

This was another piece that fit into my slowly developing thinking about my still-nebulous project. What could be the motivation of an arbitrarily advanced culture of highly evolved humans? If you have it all and can do anything, what could you possibly want? It seemed to me that Stapledon's notion of a striving for redemption gave me a starting point.

But is redemption achievable, no matter how advanced your technology? It would surely be morally vacuous for an advanced civilisation to 'wipe out' the past. Likewise producing copies of individuals who live 'perfect' versions of their lives (as in physicist Frank Tipler's Big Crunch heaven) is surely meaningless because the suffering of the originals is still 'out there' somewhere. In Christianity Christ 'is the atoning sacrifice for our sins, and not only for ours but also for the sins of the whole world' (1 John 2). But there has been a two-thousand-year debate about what exactly Christ's atonement meant, indeed what was the meaning of His death. (This old controversy was revived recently in the reaction to Mel Gibson's Passion of the Christ.)

In the middle of 2001 I began to pull all this together into a proposal for a series of books to be called 'Homo Superior'. The three books would be three possible outcomes of the human evolutionary future, but not set in a single universe. The first, now called Coalescent, set in the present and past, was about hive minds surviving from ancient Rome: our future as drones. The second, Exultant, was the Galaxy war set in my Xeelee universe: our future as child soldiers. And the third, Transcendent, was about a highly evolved but flawed mass mind of the far future trying to achieve redemption by meddling with the past - that is, our present. Why a series? The ideas behind these novels, while different from each other, were all expressions of a common root, an interest in the possibilities of evolution. I suspect series of novels are popular in sf precisely because they give you a framework wide enough to look at big ideas from many angles, and there can be few bigger ideas than human evolution.

I worked on this proposal during a signing tour of the UK for that year's published novel, Manifold: Origin, and in the middle of drafting the next year's novel, Evolution. This is the way it goes; as it generally takes a year from submission of a manuscript to publication, you always find yourself working on many projects at once, and ideas and themes from one project inevitably, it seems to me, overlap into the next.

Amid the mucking-about with contracts, publishers and agents that followed (I'm always happy to achieve a sale, of course) it emerged that the American marketeers didn't like 'Homo Superior' as a title, for they imagined mid-westerners would think it had something to do with homosexuality. (I'm not making this up.) We bounced around alternatives and 'Destiny's Children' was their choice, even though I felt it was a bit lame, and was worried I might get sued by Beyonce Knowles.

So I began working on the first of the novels, Coalescent, in 2002. There's no cut-off point at which inputs and new ideas stop flowing, and as I started to drill into this novel the deeper thinking and new research reshaped my ideas. I've always had a certain fascination with Rome and Roman Britain. Perhaps this was a naïve romanticism about the fall of a great civilisation in the past: the story of Rome is more complicated, of course. But the mythos of the fall is part of its legacy. So I began to work that in as an element in the drama. As I researched further I visited locations: there's no substitute for actually seeing a place if you can. So we visited Rome, and locations in Britain as well, such as Verulamium (St Alban's) and the London Wall, a fascinating walk.

My main rescoping, though, was a decision to set all three of my novels in a single timeline, that of the Xeelee universe, so that now Books 1 and 3 would be respectively a prequel and sequel to Book 2, Exultant. For one thing I wanted to contrast this new series with my Manifold books which had used a similar parallel-universe strategy. And I had decided a single timeline would give greater resonance: while George Poole investigates the fall of Rome, a cataclysm in the past, he finds hints of greater cataclysms in the far future, to be developed in Books 2 and 3.

With the second book, Exultant, I was more explicitly revisiting my Xeelee universe. Human memory seems to have a series of cut-offs, which I've discovered as my career has (thankfully) lengthened. I may forget odd details of a book from a couple of years ago, but it's still 'mine'. A book from more than six or seven years ago, however, while of course I'll remember working on it, doesn't even feel like mine any more. So my earlier Xeelee material had the feel of an external input - as if, oddly, I was collaborating with a younger version of myself. But this helped the project, as incidents from the ancient history of the chronology became transmuted into myth, or the substance of religions. Michael Poole, a heroic but somewhat deranged engineer who features in the early material, is a descendant of the George and Michael Poole of 'Destiny's Children'. Also I suspect some of my earlier stuff, produced as I was learning the craft, has a deep connection to my subconscious concerns, never a bad well to draw from.

More inputs came from thinking about the Second World War, which shaped the 1950s Britain in which I was born. I visited Bletchley Park. In the Churchill War Rooms in Whitehall I was struck by a wall map of the world studded all over by pin marks. That map showed that with 1940s technology they really had managed a war on a global scale; if that was possible maybe we could also rise to the 'challenge' of a galactic conflict. I have always responded to stories of heroism, and technological ingenuity under pressure. But personally I'm anti-war, I don't believe it's any way for an advanced civilisation to resolve its problems, and I'm greatly suspicious of our leaders' habit of using fear to control us. There are echoes of the Dambusters in Exultant, but Orwell is in there too. One speech I gave a military leader in a story in Resplendent came straight from Donald Rumsfeld.

When I came to Transcendent in 2004 I thought harder about the near future which was to be the arena for the far-future meddling. This section of the novel needed its own narrative, and I decided to tackle climate change, surely our greatest near-future threat, to be contrasted with galactic calamities in the further future. I'm depressed how much of the debate about climate change seems to veer from simple denial to a helpless listing of doomy possibilities. I wanted to be upbeat, to plot a way from now to an imagined 2047 in which we have managed a huge transition to a post-oil, low-carbon age.

These ideas were partly shaped by where I was living by now. We had moved from leafy but overcrowded Bucks to a rented house in a village called Ulgham in Northumberland, my wife's home county, where we were house-hunting for a permanent move. Ulgham is a classic relic of our petrol-obsessed economy. Once it was a self-contained agricultural community. Now there are no facilities but a pub, and everybody travels to church, school, shops. I saw that to survive the end of oil we are going to have to abandon the false economies of this endless travelling and live more locally: a revival of a village culture. But I'm not fantasising a return to the Neolithic; with modern communications we can bring work and school to us, rather than the other way around. My 2047 vision is still utopian, however, because it is predicated on wise leadership from the US...

Another ongoing input, incidentally, has always been ideas from the trunk: stories that didn't quite make it, but which nevertheless had elements worth revisiting. For example my novella 'Mayflower II', which won a BSFA award, drew on a never-published end-of-the-world story called 'Custodian' I drafted when I was nineteen, while another early story about undying babies called 'Planet of Immortals' was an input to my novella 'Reality Dust', and an end-of-the-sun story called 'Twilight' fed the closing novella of Resplendent. A story called 'The Ghost Pit' drew on a joky old piece called 'Save Me, Captain Culpepper!' published in the small press, and another piece called 'The Cold Sink' drew on ideas from a dodgy story called 'The Glittering Caverns' published only in Germany. A failed pitch for a TV drama called 'Virtuals', from 1997, was another input into Resplendent. And so on. One tip I'd certainly give budding writers is never to throw anything away; these ideas and characters are yours to reexplore.

Maybe the deepest input of all into this particular series was my childhood Catholicism. Authors are often asked what their influences are, the expected answers being a writer, a book, a movie, a TV show. But much more significant for each of us surely includes the type of landscape into which we're born, the point in history, the ethnic identity, the culture. And for me that culture was Catholicism. But if religion has shaped my sf, perhaps I'm not alone.

Adam Roberts' remarkable survey The History of Science Fiction (Palgrave, 2005) takes as its framing narrative the idea that science fiction arose (or rather was revived from 'fantastic voyage' traditions dating back to antiquity) during the Reformation, when Protestantism ripped itself alien-like out of the chest of a horrified Catholicism, and that since then the genre has been shaped by a dialectic between rational and 'miraculous' poles.

This makes sense to me. Stapledon's Star Maker is about a quest for a supercosmic god outside the universe; works of Clarke's like Childhood's End and 2001 are about transcendence, godhood arising from within us. Even in comic-book mythologies you find Jesus-figures all over the place, not least Superman, the ur-hero himself. In an early episode of Smallville Clark Kent was 'crucified' in a repulsive high-school-hazing stunt; the writers of that smart show demonstrated they understood the deeper roots of their character. Even Doctor Who, in the final Tom Baker story 'Logopolis', 'died' in the process of defeating the Master, only to be resurrected (as Peter Davison).

Perhaps this religious dialectic lies at the centre of the genre's meaning because, long before sf, religions taught us to frame questions about the universe. For example the Fermi Paradox has much in parallel with the much more ancient conundrum of silentum dei, the 'Silence of God'. Bertrand Russell was once asked how he would respond to God if he were called to account for his atheism: Russell said he would ask God why He should have made the evidence for His own existence so poor. Perhaps the universe imagined by SETI enthusiasts, dominated by superior but invisible consciousnesses, really isn't so different from the Christian universe. The premises of all our religions may be wrong. But thinking about God will have served a profound purpose if it has been a kind of vast practice run, a training programme that has lasted millennia, to prepare us to deal with the real gods out there.

I think there's surely much truth in Adam's reading, though perhaps not the whole truth; nothing as complicated as sf can be boiled down to a single storyline. It certainly works for me. The whole of the Xeelee sequence is about a war in heaven, with we humans caught in the middle. And arguably you could see the three 'Destiny's Children' novels as different searches for a vanished God.

While I was still working on the project, of course, the first books and stories began to appear. I was reassured that my struggle through this thicket of ideas had resulted in material that received good reviews and won a few awards, along with a few brickbats. Sometimes success is unexpected, however. I hadn't really anticipated the positive response to Coalescent, my first near-contemporary novel, and the most autobiographical, I suppose. I was pleased, but I realised now that the follow-up, the space-operatic Exultant, was going to be a jolt for the readers. But by then it was too late to change horses.

Though I'm working on a new series of stories (called 'Old Earth' and published by Analog) set in a still further Xeelee future, my Destiny's Children project is complete, and I'm working on new stuff. The process of developing ideas - my process anyhow at this stage of my career - seems messy and fractal. I'll focus on the needs of a single story or novel chapter which might take a day or two to draft, but which is set in the overlapping contexts of a novel, and of a series which spans several years' work, and indeed of my whole career, dating back to 'The Xeelee Flower' - and even before, as elements of my background such as my childhood Catholicism find expression. Messy and fractal, but endlessly fascinating, and fun.

The Unconquered Sun

Based on material first published in Matrix, BSFA, September 2005.

In my second Time Odyssey collaboration with Sir Arthur C Clarke (Sunstorm, 2005), a disorderly sun threatens Earth. The misbehaviour of the sun has featured in many of Clarke's works, beginning with 'Rescue Party' (1946), and including his novel Songs of Distant Earth (1986) in which mankind has a thousand-year warning and scatters to the stars. In Sunstorm we're doing the idea justice, we hope.

The first sf depictions of solar disasters concerned the running down of the sun's power. The best guesses of the nineteenth-century physicists up to Lord Kelvin were that the sun was powered by gravitational contraction, which would last only a few million years. An expiring Kelvin-esque sun is memorably mentioned in a catalogue of possible ends of the world in Camille Flammarion's thoroughly astonishing Omega: The Last Days of the World (1893). The dying sun is also glimpsed by HG Well's Time Traveller in The Time Machine (1895), in a passage which seems heavily influenced by Omega. Conversely in Olaf Stapledon's still-stunning Last and First Men (1931) the Eighth Men are driven to migrate to Neptune by a flaring sun destabilised by a collision with an interstellar cloud.

In the early twentieth century it was realised that nuclear fusion, the sun's true power source, should enable it to shine for thousands of millions of years, and concern about the longevity of the sun was replaced by speculation about what might happen if it misbehaves. I first came across such ideas in the pages of the marvellous 1960s comic TV Century 21, when the Thunderbirds race to subdue an unruly sun with immense bombs.

Usually, though, there's nothing to do but flee. In JT McIntosh's One in Three Hundred (1954) a brightening sun ruins Earth but brings Mars alive. So a fleet of life-ships is hastily assembled, and the inexperienced 'lieutenants' who will pilot them are ordered to select the 'one in three hundred' who will be spared the fire. The book, by a Scottish writer now mostly forgotten, is realistic for its time and enjoyable; the central section, as little ships retreat Dunkirk-like across the gulf of space, is particularly affecting. But at heart the story is all about power: the life-or-death arbitrariness wielded by the lieutenants, the power accrued by a tinpot gang lord in the chaotic colony on Mars. This jars with modern sensibilities, but born in 1925 McIntosh grew up through wartime, and the discipline has a military feel to it.

The exercise of power seems to be a common theme in solar-powered sf. In Richard Lupoff's Sun's End (1984) a treacherous Sol is heating up, slowly enough to be all but unnoticed by the mass of the population. The protagonist is Daniel Kitajima, a blue-collar orbital construction worker in a Heinleinian 2009, who suffers an accident and is revived, Steve Austen-like, as a cyborg 80 years later. Kitajima's episodic adventures take him to cargo cults on Mercury and Titan, and to the moons of a previously unnoticed giant planet. A complicated mix of Japanese culture and space-operatic pastiche, this is an odd, disjointed book, overfull of ideas and ultimately unsatisfying, but with some intriguing facets. And it is another book about power, in this case wielded by Kitajima as he submits himself to a cyborg destiny, and Earth's billions, 'pathetic grubs that squirmed on a planet somewhere' (chapter 16) are left to fry.

Norman Spinrad's The Solarians (1966) is an exception, for here the usual power relationship is reversed, when humanity actually causes an instability in the sun. We are losing a war of attrition with the relentlessly logical Dulgaari. But the Dulgaari fleet is duped into entering the solar system, 'Fortress Sol' - where it is vaporised by an artificial Nova Sol, 'like a swarm of moths caught in a flamethrower' (chapter 12). This is a commercial effort by a pre-Bug Jack Barron Spinrad, but the book is fast-paced, enjoyable and quite deep, and the scenes of the destruction of an evacuated Earth are affecting.

Such works reflect ancient perceptions. Political power has always flowed from the sun. Significant solar cults tended to arise in organised, heavily centralised states - the Egyptians, the Aztecs - the sun serving as an obvious metaphor and source of authority for the one ruler on Earth. One of the last great pagan gods was Sol Invictus, the Unconquered Sun; his cult flourished in the late Roman empire just before Christianity became the state religion (and assimilated Sol's feast day as Christmas Day). Similarly in our modern sf fables the sun's superhuman power is co-opted by the Competent Men who deal with their fellow strugglers harshly but fairly. Even in the comics, the source of Superman's powers is sunlight - a signifier of the depth of that particular modern myth.

Perhaps we moderns are too blasé about the sun. Certainly our understanding of the sun exceeds that of our ancestors manifold, but we are just as dependent on its power.

The sun's variability affects our climate. For over seventy years, from around 1640 to 1710, very few sunspots were observed on the sun's face - and the Earth was plunged into what the climatologists call the 'Little Ice Age', when London children ice-skated on the Thames. Today our dependence on high technology makes us vulnerable to even mild solar tantrums. A flare once knocked out communications on Air Force One; on 24th April 1984 President Reagan, over the mid-Pacific, was left incommunicado for two hours. The most powerful solar flare ever recorded occurred quite recently, on 4th November 2003, enough to saturate X-ray detectors on several satellites; we were saved from more significant damage only by a chance alignment of celestial magnetic fields.

Maybe we should count ourselves lucky. The astronomers have observed 'super-flares' on stars superficially similar to the sun. As far as we know our sun has never misbehaved as badly as that.

But in the long term we face more serious problems. Since its birth the sun has been increasing its luminosity, slowly but surely. Up to now Earth's feedback processes have kept the planet's temperature stable, but in a billion years or so the regulators will be pushed to their design limits - and later still, when the sun ends its 'main sequence' lifetime and balloons into a red giant, even International Rescue may not be able to save us.

The origin of the Xeelee universe

First published in Wondrous Beginnings, ed Steven Silver, Tekno Books / Daw Books, Jan 2003.

The Xeelee Flower was first published in 1987.

By then I'd been writing stories for around 15 years, without success in placing anything for publication; I'd even tried out a novel. I'd tried to study the craft - notably, in those days, Larry Niven. I was a great fan of stories like The Hole Man, which was written in such a lucid style that studying it helped me figure out how such pieces work.

The core of Xeelee Flower was the central jeopardy situation: I had an image of an astronaut, stranded in orbit around a sun about to go nova, sheltering behind an energy-soaking 'umbrella'. To develop the idea I did some technical research, to figure out just how much each square metre of the umbrella would have to absorb.

But I also figured out the background: Who was this guy? How had he got stranded there? Where did the 'umbrella' come from? I came up with the notion of powerful off-stage aliens called the Xeelee (I can't remember where I got the name), whose purloined artefact, the Xeelee Flower itself, would save my hero's life. Accompanying this was the vague idea of a Galaxy full of minor species, including ourselves, living in the shadow of the Xeelee.

All this was very playful; I wanted the tone to be light and fast-paced, and writing was just a hobby for me in those days. I worked on the story in the early summer of 1986. I remember sitting up late to watch soccer matches in that year's World Cup; when the action was dull I would progress the story a little more.

I actually had the story completed before I found Interzone, its eventual market. I was lucky in a sense that the magazine had an upcoming new writers' issue, with a slot just big enough for Flower. But I'd been pushing on a lot of closed doors for a long time; one of them was eventually going to open for me.

The Xeelee, of course, continue to be very important for me. In my next story I posited humans in a four-dimensional cage, put there by more powerful off-stage aliens. Eventually I realised that if I made the aliens the Xeelee, I had the beginning and the end of a future history, which grew, organically, from that point. I suspect for much of my career I'll be referring back to elements of this story.

Where Do I get My Ideas From? - The Roots of Manifold

Based on material first published in Matrix, BSFA, July 2001.

August 2001 saw the publication of the third novel of my Manifold series, Origin. Phase Space, a collection of related stories, appeared the following year, but this brought to an end a project which had engaged me, on and off, for fourteen years (!).

The seeds of Manifold go all the way back to an unpublished story I drafted in 1987, just about the time I was starting to sell professionally. I was never happy with the story and put it aside. But it contained two elements I liked: an off-stage race of relatively low-tech aliens who used teleport links to beam themselves around the Galaxy; and a quixotic mission to a 'burster', a periodically exploding neutron star ('Burster' became my working title for the piece).

I returned to the story at a loose moment in 1995. I realised that the low-tech-aliens angle was a big idea that could be expanded to a new series, and that I had a number of other unfinished and unpublished tales which could then be fit together to make a new and open-ended saga. So I began to sell a series of stories set in what I called the 'Saddle Point' universe to the American magazine SF Age. These tales were based on the old material and wholly new stuff. 'Burster' itself finished up (heavily re-written) as a story called 'Fusion Summer'.

But after a couple of years of such story-spinning I began to ask myself new questions. How come nobody had advanced beyond lightspeed-restricted teleport gates - why no warp drive? What was keeping them low-tech? I realised that I was touching on the venerable Fermi Paradox: if the aliens exist, how come we don't see them? One possible answer is that it's a dangerous universe out there: maybe Something Heavy regularly slams us all back down to pond life, so nobody gets the chance to advance. That scenario, and the existing stories, would eventually become the second novel of the Manifold sequence, Space.

But I'd meanwhile become interested in other answers to the Fermi question. What if we are simply alone? The thought of mankind growing old alone in a dying universe is pretty desolating. I had prepared an outline for an end-of-time novel along those lines back in 1993; unhappy with its lack of context I put it aside. But now I saw that if I could link it with the Space material, using the same characters in a Moorcockian multiverse, I could start to explore Fermi in an interesting way. And another ancient idea helped me get started: a Brannon Braga-type Star Trek outline I once scribbled down concerning a destiny-changing time paradox ... Thus I had the bare bones of the first Manifold novel Time.

As for the last novel, I wanted to explore 'spooky solutions' to Fermi: what if They are out there, but hiding? Eventually I hit on something suitably paranoid, and yet which would tie together all three books, and Origin was born.

In the course of the books, as usually happens for me, spin-off ideas and sidebars became pieces in their own right; these included my stories 'People Came From Earth' and 'The Gravity Mine'.

So there it is: much reworking of ideas, a general deepening and broadening of thought, and probably a nightmare for bibliographers.

Creative writing isn't a particularly linear process. Over a lengthy career, I suspect writers are drawn back to certain key ideas and themes - obsessions if you like - which they work over and over. The whole thing is kind of bushy, with roots in older material and ideas, and an exfoliation of new stuff. Manifold is unusual in that I've been able to trace the whole process right back to where it started, with that dodgy story in 1987.

Other Romes

Based on material first published in Matrix, BSFA, July 2001.

My novel Emperor (2006) features Roman Britain. Maybe my interest in the period stems from growing up during the Cold War, when nuclear war and the collapse of civilisation seemed about to happen to us.

Britain was left with one of the most remarkable monuments of antiquity: Hadrian's Wall. But I want to suggest that without the Wall the western Empire might have survived … and Latin would have been spoken with a Scottish accent.

Did Rome have to fall? Of course in the genre this speculation has a long tradition, dating back to L Sprague de Camp's Lest Darkness Fall (1941), in which a time traveller tries to fend off the Dark Ages. See Robert Schmunk's remarkable Uchronia website (*) for more examples.

More recent is Robert Silverberg's fascinating Roma Eterna (Gollancz, 2003), in which the turning point is Moses's failure to lead the Jews out of Egypt. Christ is never born - and it never happens that 'the basic structure of Roman society is weakened by superstition, until the Empire … is toppled by the barbarians who forever lurk at its borders' (p4). Silverberg's scenario resonates with an essay by historian Carlos Eire (in More What If?, ed. Robert Cowley, Putnam's, 2001), who imagines Pilate sparing Jesus thanks to his wife's bad dream. A new kind of Judaism, with Jesus a prophet, not a Messiah, becomes the state religion, and helps the Empire endure.

The historians identify many apparent turning points. For example (see the essay by Lewis Lapham in What If?, ed. Robert Cowley, Putnam's, 1999), during Augustus's reign, the legions pushed beyond the Rhine. The Germans were ferocious but primitive: the Romans should have won. But in AD 9 Augustus put his forces in the hands of one Publius Quinctilius Varus, a palace functionary who had married into the imperial family. Varus was betrayed by a Germanic called Arminius, or Hermann. Three Roman legions were lured into a trap in the forest. Augustus never really recovered, and from that day the Rhine became the Empire's 'natural' northern border.

But the defeat needn't have happened. Perhaps the legions could have reached the Baltic - even the Vistula - even Moscow, civilising as they went. Later, without barbarian pressure from the north, the western Empire might have endured. And Hermann would never have become a mythic hero, to inspire, among others, Hitler.

Here's another possibility (see Barry Strauss's essay in What If?). Three hundred years after Augustus, the Visigoths, fleeing the Huns, asked for leave to cross the Danube and settle inside the Empire. Emperor Valens, needing troops to fight the Persians, agreed. But local officials fleeced the Visigoths, and they rebelled - and Valens responded weakly - and, at Adrianople, barbarians killed an emperor. There was no way back; within fifty years the Visigoths would sack Rome itself. But again it was all down to individual weaknesses. If only Valens had been a slightly better general, or a wiser administrator …

Perhaps our focus on Roman counterfactuality is a parochial prejudice. In AD 100, Rome was just one of four immense Old World empires; perhaps the Han, Kushan or Parthian realms could have won out. But Rome did have one unique political invention: like Star Trek's Borg, it assimilated the conquered, turning them into citizens. A tolerant, polytheistic religion helped. In Silverberg, though, this flexibility is seen as an eventual weakness; the Empire, morally vacuous, simply endures.

And if Rome had survived, a route through the centuries can be espied. A united Empire might have fought off Islam where Byzantium, its eastern rump, failed. Rome's armies would have handled the Mongols better than its medieval successors. In the Americas they surely wouldn't have practiced genocide, but assimilated, in the Roman way - but diseases would still have passed from Old World to New. In Europe there would have been no feudalism, no chivalry - no parliaments - and no England. Might this been a 'better' outcome?

But is this wishful thinking - was Rome's fall actually inevitable? I've argued myself against 'great men' theories; on long timescales the likes of Valens and Varus are irrelevant, and geography and economics exert profound influences.

This is where we come back to Hadrian's Wall. After Augustus, many emperors, including Hadrian, tried to establish 'natural boundaries' for the Empire. But those 'boundaries' were porous; in the fifth century the Rhine froze over, and the Vandals and others just walked into Gaul.

Worse - and here's my own theory - the 'boundaries' halted Rome's military expansion, which had always created most of its wealth. Not only that, the barbarians left unmolested beyond those boundaries grew stronger. In Scotland, the Picts became a formidable foe; it would have been better for Hadrian to have cleaned out the glens.

So there was no net wealth creation, and yet the army was getting larger to fend off the increased barbarian threat. It couldn't be sustained … But maybe even here there are counterfactual possibilities. Perhaps with a bit more time a more mature economy would have emerged, based on exploration, trade, even industrialisation, rather than endless military expansion.

When Rome did fall, the cost was particularly heavy in Britain. On the continent the victorious barbarians tried to keep up the former political structures, though with themselves on top. In Britain we got the Saxons, who would, for instance, throw building stone down wells, thus killing the towns forever. Here, it was more than just a fall; it was an erasing. It really must have been like living through a nuclear war: no wonder it resonates.

But I suspect I'm expressing a controversial view here. Many historians argue that our western freedoms were rooted in the post-Roman chaos. But the waste was dreadful, especially in Britain. It's an oddity that most counterfactual hypotheses predict worlds that are worse than our own (see the Encyclopaedia of Science Fiction (Orbit 1993)). But in this case I find it hard to believe it; surely somewhere in the tree of possibilities there was a better route to the present.

And anyhow the collapse of Roman Britain surely needn't have happened. In the early fifth century adventurous generals burned up Britain's last resources trying for the imperial purple. What if they had been a little more farseeing?

Here's my own contribution to the counterfactual catalogue. Even after the fifth century calamities, the emperors might have won Britain back, as remained their official policy. Britain, protected by the ocean, wasn't just some border outpost; for centuries it was a key source of wheat and metal for the armies in Gaul and Germany. So Britain, a rich safe province supporting a reserve of troops, might have stabilised the western Empire. And what if Hadrian had pushed on rather than build the Wall? A Roman Scotland would have been an especially formidable fortress …

By stabilising Roman Britain, and so stabilising western Europe, could Scotland have saved Rome? And would it have been a good thing if it had? The debate may last longer than Rome itself. Ave, atque vale, and och aye!


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