Now Nicolaus sat back, locked his fingers behind his head, and blew out his cheeks. “So we’re looking at the mother of all solar storms.”

“You could put it that way,” Siobhan said dryly.

“But we survived June 9, and everybody said that was the worst storm in recorded history. What can we expect this time? To lose the satellites, the ozone layer …”

Siobhan said, “We’re talking about an energy injection many orders of magnitude greater than June 9.”

Miriam held her hands up. “Professor McGorran, I was a lawyer in the days when I had a real job. I’m afraid such phrases mean little to me.”

Siobhan allowed herself a smile. “I apologize. Prime Minister—”

“Oh, call me Miriam. I have a feeling we’re going to be working together rather closely.”

“Miriam, then. I do understand. Astronomer Royal I may be, but this isn’t my specialty. I’m struggling with it too.” Siobhan brought up a summary slide, a table of numbers that filled the big wall softscreen. “Let me go through the bottom line again. In April 2042, just four and a half years from now, we anticipate a major solar event. There will be an equatorial brightening of the sun, essentially, an outflux of energy that will bathe the orbital plane of Earth, and the other planets. We anticipate that Earth will intercept some ten to power twenty-four joules of energy. That’s a central figure; we have a ninety-nine percent confidence limit of an order of magnitude up or down.”

There was that term again. “Order of magnitude?”

“A power of ten.”

Nicolaus rubbed his face. “I hate to admit my ignorance. I know a joule is a measure of energy, but I have no idea how large it is. And all those exponents—I understand that ten to power twenty-four means, umm, a trillion trillion, but—”

Siobhan said patiently, “The detonation of a one-megaton nuclear weapon releases around ten to power fifteen joules—that’s a thousand trillion. The world’s nuclear arsenal at its Cold War peak was around ten thousand megatons; we’re probably down to some ten percent of that today.”

Nicolaus was doing arithmetic in his head. “So your injection of ten to power twenty-four joules from the sun—”

“It amounts to a billion megatons, pouring over Earth. Or a hundred thousand times the energy that would have been released in a worst-case nuclear conflagration.” She said the words coolly, meeting their eyes. She was trying to make them understand, step by step, Miriam saw; she was trying to make them believe.

Nicolaus said grimly, “Why did nobody alert us to this before? Why did it take you to dig this out? What’s going on up there on the Moon?”

But it wasn’t the Moon that was the problem, it seemed; it was the muddled head of the young scientist who had figured all this out.

“Eugene Mangles,” Miriam said.

“Yes,” Siobhan said. “He’s brilliant, but not quite connected to the rest of us. We need him. But we have to dig the bad news out of his head.”

Nicolaus snapped, “And what else isn’t he telling us?”

Miriam held up a hand. “Siobhan—just give me a headline. How bad will this be?”

“The modeling is still uncertain,” Siobhan said. “But that much energy—it would strip away the atmosphere altogether.” She shrugged. “The oceans will boil, vaporize. The Earth itself will survive: the rocky planet. Life in the deep rocks, kilometers down, might live through it. Extremophile bacteria, heat lovers.”

“But not us,” Nicolaus said.

“Not us. And nothing of the surface biosphere, on the land, in the air, or the seas.” In the silence that followed, Siobhan said, “I’m sorry. This is a terrible thing to have brought home from the Moon. I don’t know any way to soften this.”

They fell silent again, trying to digest what she had said.

Nicolaus brought Miriam a cup of tea on a monogrammed saucer. It was Earl Grey, the way she preferred it. The old myth that the British were addicted to their watery, milky cuppas was at least half a century out of date, but Miriam, a Prime Minister of Europe and with a French father, always took great pains not to offend the sensibilities of anybody on this still residually Euro-skeptic island. So she took her Earl Grey hot and without milk, out of sight of the cameras.

In this silent pause for thought, with her teacup cradled in her hands, Miriam was drawn to the window, and the city.

The silver stripe of the Thames cut through London’s geography, as it always had. To the east the City, still second only to Moscow as a Eurasian financial center, was a clutter of skyscrapers. The City occupied much of what had once been Roman London, and in her time as a student here Miriam had once walked the line of the wall of that primal settlement, a trail that ran a few kilometers from the Tower to Blackfriars Bridge. When the Romans had gone the Saxons had developed a new town to the west of the old walls, the area now known as the West End. With the great expansion of the cities that had followed the Industrial Revolution, those complicated knots of multilayered history had been drowned by new suburban development, until London was the heart of a vast conurbation that today reached out as far as Brighton in the south and Milton Keynes to the north.

The basic geography of London hadn’t changed much since the 1950s, perhaps. But a witness from that receding age would have been astonished by the glimmering width of the Thames, and the massive flanks of the new flood barriers that could be dimly glimpsed past the shoulders of buildings. The Thames had been tamed over the centuries, pushed into a deepening, narrowing channel, its tributaries bricked over, its floodplain built on. Until the turn of the century, London had got away with it. But the world’s climate shifts had brought an inexorable rise in sea levels, and humans had been forced to retreat before the Thames’s determined retaking of its ancient territories.

The reality of climate change and its effects were undeniable, and a day-to-day political reality for Miriam. Remarkably the argument about the cause of it all still continued. But that decades-old debate was moot now, as attention had gradually switched to the need to fix things. There was a will to act, Miriam thought, a gladdening and growing realization that things had gone too far, that something must be done.

But it was surprisingly hard to focus that energy. Long-term demographic changes had led to an aging of the population in the West: more than half of all Western Europeans and Americans were now over sixty-five, mostly unproductive, and conservative with it. Meanwhile the interconnectedness of the world had culminated with the great UNESCO program to equip every twelve-year-old on the globe with a phone of her own. The result was a detachment from traditional political structures among the young and middle-aged, who, educated and interconnected, often showed more loyalty to others like them around the world than to the nations of which they were nominally citizens.

If you looked at the world as a whole, this was probably the most truly democratic, educated, and enlightened age in history. The growth of a literate, interconnected elite certainly made major wars a lot less likely in the future. But it did make it hard to get anything done—especially when tough choices had to be made.

And it seemed that tough choices faced Miriam now.

At fifty-three, Miriam Grec was in her second year as Prime Minister of the Eurasian Union. She was the senior political figure across a swath of the Old World that stretched from the Atlantic coast of Ireland to the Pacific coast of Russia, and from Scandinavia in the north to Israel in the south. It was an empire no Caesar or Khan could have contemplated—but Miriam was no emperor. Enmeshed in the complicated federal politics of the young Union, buffeted by tensions between the great power blocs that dominated the world of the mid-twenty-first century, and having to cope with more primitive forces of religion, ethnicity, and residual nationalism, she sometimes felt as if she were trapped in a spiderweb.