Emma!

He pounded on, the moist sand cold under every footstep. As his blood pumped he felt the structure of his thoughts dissolve, his obsessive night-time round of planning and worrying and agonizing over I-should-have-said and I-should-have done, all of it washing away. The main reason to exercise, he thought: it stops your brain working, lets your body remind you you’re still an animal.

It was the only respite he got from being himself.

He’d meant to run a couple of miles before doubling back. But when he reached his turn-back point he spotted something on the beach, maybe a mile further south: blocky, silhouetted, very large, returning crumpled orange highlights to the approaching sun. A beached whale? The Tide had played hell with migration patterns. No, too angular for that. A wreck, then?

On impulse he continued on down the beach.

The washed-up object was the size of a small house, twenty-five or thirty feet high. It was heavily eroded, its walls sculpted by wind and water into pits and pillars. When Malenfant stood at its foot the sea breeze that washed over it was distinctly colder.

He ran his hand over its surface. Under stringy seaweed he found a grey, pitted surface, cold and slick under his palm. Ice, of course. The dawn light was still dim, but he could make out the cold clean blue-white shine of the harder ice beneath. He wondered how long the berg would sit here before it melted into the sand.

It was here because of the Tide.

The first few days had been the worst, when Earth’s oceans, subject to a sudden discontinuous shock, had sloshed like water in a bathtub. Millions of square miles of coastal lowland had been scoured. In some places, pushed by currents or channelled by sea bottoms, the oceans had spawned waves several hundred feet high, walls of water that had crushed everything in their paths.

After that, with twenty times the mass of Luna, the Red Moon raised daily tides twenty times as high as before — roughly anyhow; the new Moon’s spin complicated the complex gravitational dance of the worlds.

The coastlines of the world had been drastically reshaped. The English Channel was being widened as the soft white chalk of the lands that bordered it, including Dover’s white cliffs, was worn away. Even rocky coastlines like Maine were being eroded. The lowest tides on the planet used to be in the Gulf of Mexico, the Mediterranean, and elsewhere: now those tides of two feet or less had become forty feet, and around the shores of the Mediterranean many communities, with roots dating back to the dawn of civilization, had been smashed and worn away in a matter of weeks. Meanwhile the tides had forced their way into the mouths of many of the world’s rivers, making powerful bores a hundred feet high, and vast floodplains filled and drained with each ebb and flow, drowning some of the planet’s most fertile land in salt water.

People had fled inland, a secondary tide of misery, away from the devastated coasts. Already there had been too many deaths even to count, from flooding and tsunamis and “quakes — and there were surely many more to come, as the displaced populations succumbed to disease, and flooded-out farmers failed to return a crop, and as the wars broke out over remaining stocks.

Meanwhile, as the polar seas flexed, titanic rafts of ice broke away from the shelves of Antarctica and the glaciers of Alaska and Greenland. The larger bergs broke up in the tempestuous seas, but many of them survived to the Equator, filling the oceans, already all but impassable, with an additional hazard. And so bergs like this one were now common sights at all latitudes on the seaboards of the Atlantic and Pacific. In some places they were actually being mined to make up for the disrupted local supplies of clean fresh water. Always a silver lining, Malenfant thought sourly.

He stripped off his sweaty track suit and ran naked into the surf. Deeply mixed by the Tide with the waters of the deep ocean, the sea was icy cold and very salty, stinging when it splashed his eyes and the scar tissue on his healing arm. He took care not to go far out of his depth; he could feel a strong undercurrent as the sea drew back.

He swam a few strokes and then lay on his back, studying the sky, buoyant in the salty water.

The Red Moon was fat and swollen in the sky above him. Though it had (somehow) inserted itself into the same orbit as the old, vanished Moon, it was more than twice Luna’s diameter, as large in area as five old Moons put together — and a lot more than five times as bright, because of its reflective cloud and water.

And this morning, the Red Moon was blue. The hemisphere facing him showed a vast, island-strewn ocean, blue-black and cloud-littered, with the shining white of ice caps at the northern and southern extremes. The Red Moon’s north pole was tilted towards Earth by ten degrees or so, and Malenfant could see a huge high pressure system sitting over the pole, a creamy swirl of cloud. But dark bands streaked around the equator, clouds of soot and smoke.

Malenfant, for all his personal animosity, admitted that the new Moon was hauntingly lovely. It even looked like a world: obviously three-dimensional, with that shading of atmosphere at the sunlit limb, and sun casting a big fat highlight on its wrinkled ocean skin, as if it were some immense bowling ball. Poor Luna had been so dust-choked that its scattered light had made it look no more spherical than a painted dinner plate.

Malenfant, understandably obsessive, had kept up with the evolving science of the Red Moon.

The new Moon turned on its axis relative to Earth — unlike departed, lamented Luna — with a “day” of about thirty hours, so that Earthbound watchers were treated to views of both sides. The other hemisphere was dominated by the worldlet’s main landmass: a supercontment, some called it, a roughly circular island-continent with a centre red as baked clay, and fringed by grey-green smears that might be forests. The Red Moon was hemispherically asymmetric, then: like Mars and Luna, unlike Earth and Venus.

That great continent was pitted by huge, heavily eroded impact craters: to Malenfant they were an oddly pleasing reminder of true, vanished Luna. And the centre of the supercontinent was marked by a single vast volcano that thrust much of the way out of the atmosphere. Its immense, shallow flanks, as seen in the telescope, were marked at successively higher altitudes by (apparent) rings of vegetation types, what appeared to be glaciers, and then by bare rock, giving it to terrestrial observers something of the look of a shooting target. (And so the commentators had called it Bullseye.)

The Red Moon’s mightiest river rose on the flanks of the Bullseye. Perhaps that great magma upwelling had lifted and broken ancient aquifers. Or perhaps air uplifted by the great mountain was squeezed dry of its water by altitude. Anyhow the river snaked languidly across a thousand miles to the eastern coast, where it cut through a mountain chain there to reach the sea at a broad delta.

There were mountains on both east and west coasts of the supercontment. They were presumably volcanoes. Those on the east coast appeared to be dormant; they were heavily eroded, and they seemed to cast a rain shadow over the desiccated interior of the continent. There was, however, a comparatively lush belt of vegetation between the mountains and the coast. The commentators had called it the Beltway. The greenery pushed its way into the interior of the continent in a narrow strip along the valley of that great river, which was a Nile for this small world.

But the mountains on the west coast were definitely not dormant. Presumably prompted by rock tides induced by Earth’s gravity field, they had been observed to begin erupting a few days after the Red Moon’s arrival in orbit around Earth.