"Dear God!" gasped Alice, one hand going to her mouth.

The others were too horrified by what they were seeing to even speak. The image of the moon being displayed on the common room's wall mounted television screen was being sent back by one of the Lagrange probes, sent out to explore the collection of tiny rocks orbiting the sun sixty degrees ahead of and behind the Earth in its orbit. It showed the hemisphere of the moon opposite the cloud's impact site which, from this vantage point, was gibbous. Two thirds full. The centre of the moon's face was still seas and craters, the moon as they'd always known it, but the window of visibility was rapidly shrinking as volcanic clouds closed in on all sides, the gas and dust rushing to fill the vacuum. Soon, within the hour, the circular hole in the clouds would close and the moon would have an atmosphere again for the first time in millions of years.

"If it had hit the Earth..." said Eddie, numb with shock. First the mass dampener in Martinique, then the alien spaceship, now this... One thing after another, with not enough time to process each shock before the next one hit. He felt that he'd fallen down a rabbit hole and was tumbling faster and faster down into the darkness, totally out of control. Animal panic threatened to sweep him away, making him want to run and hide, find some dark little hole where he could pretend that the outside world was still comfortable and familiar, the world he'd lived in all his life. He held onto himself like a drowning man clutching hold of a life belt.

"If it had hit the Earth, it would all be over by now," said Ben. "We'd all be dead. Everyone would be dead. As it is, we've still got it all ahead of us."

The others nodded. They were all scientists, they all knew what was going to happen. The damning facts were being displayed on Stuart's tablet, set up on the table where they could all see the figures and statistics that had been released by the home office.

"The moon's been knocked into a new orbit," said James. "How long until we know what the new perigee will be?"

"There's no telling how much of the cloud hit the moon," said Stuart. "We'll have to wait until they make some observations. We could set some limits, though. Calculate the moon's orbit if the entire mass of the cloud hit it, if only ten percent hit it, and so on." He pulled his phone from his pocket, selected the calculator app.

"If this had happened to the aliens, they could have just pushed the moon back onto its proper orbit," said Frank. "If a mass dampener the size of a walnut could shrink the mass of a thousand ton spaceship down to almost nothing, a dampener big enough for the moon might be around the size of a small city. Probably well within their abilities."

"If we'd had more time, we could have done it ourselves," said James miserably. "Four and a half billion years the moon's been circling the Earth, and then this happens just a hundred years before we had the technology, the industrial might, to correct it. We've probably lost our chance now. Civilisation will be hit hard. Mankind will be thrown back to a simpler lifestyle. We can say goodbye to the stars, probably forever. Anyone else think the timing's a bit suspicious?"

"You think this was done by hostile aliens?" said Ben, the ghost of a smile on his lips. "Why not just send the cloud to hit the Earth? Wipe us out and have done with it?"

"Maybe they don't want us dead. Maybe they're just afraid of the progress we've made. Or maybe they meant to hit the Earth and missed."

"Missed?" said Ben incredulously. "We can aim a probe at a tiny lump of ice twenty billion klicks away with an accuracy of a couple of kilometres. They have the ability to do that..." He pointed at the television. "...and they missed?"

"A cloud's not the same as a space probe. A probe's a single object, you can make course corrections. How do you give a cloud a course correction? Then there's the composition of the cloud particles. Some kind of exotic material so dense that a teaspoon of it weighs a thousand tons. We've been trying to think of a natural explanation and failing. We've got no idea at all what it could be made of. Maybe it's artificial."

"And maybe we just don't know enough about the Universe yet to know what it's capable of. Let's give the fanciful speculation a rest, okay?"

"A mass dampener wouldn't be any good anyway," said Alice. "I assume you're thinking of shrinking the moon's mass, then putting a rocket engine on it and pushing it, right?"

"Yeah, something like that."

"As soon as you removed the moon's mass, its internal pressure would push it apart. The moon would literally explode."

The others stared at her as they realised she was right. "Well, perhaps we could turn the device on and off every couple of seconds," suggested James. "It'll take a good bit longer then two seconds for the moon to fly apart, right? You reduce the moon's mass for two seconds, or whatever the safe length of time turns out to be, and fire the rocket engine during those two seconds. An ion drive can turn on and off Instantly, so that wouldn't be a problem. Then you turn off the rocket engine and the mass dampener for a few minutes, long enough for the moon's gravity to pull it together again. We push the moon a little bit at a time, not all in one go."

"There's another problem," said Alice, though. "The rocket engine would be within the mass dampener's area of effect. The exhaust would also be massless. It wouldn't be able to push anything." The others nodded dismally.

"You could put the mass dampener on the moon's forward hemisphere," mused Jessica thoughtfully, "with its area of effect precisely calculated so that it just barely encompasses the whole of the moon. Then you put the rocket engine on the trailing hemisphere, raised up on a scaffold so that it's just outside the area of effect."

"The moon's forward hemisphere is soon going to be an ocean of magma," pointed out Ben.

"So you build a platform that floats on magma. How much heat can a shuttle's heat shield take? If you made a boat made from a shuttle's heat resistant tiles..."

"Even if the platform survived, it would still conduct the heat. Heat shields protect shuttles by evaporating and carrying heat away. Your platform couldn't do that. Even if the platform itself could survive the heat, the mass dampener would melt."

"So we put the mass dampener above the moon's surface. The moon's going to have an atmosphere soon. We could build a balloon to carry the mass dampener up in the clouds, safely above the moon's surface."

"There's probably going to be fierce turbulence. The balloon would bob up and down. Your rocket engine on the other side of the moon will occasionally be engulfed by the mass dampener's area of effect."

"Maybe that wouldn't matter, so long as it was outside the area of effect for long enough."

"The mass dampener would still need to be the size of a city, remember? You'd need one hell of a balloon! And besides, our prototype dampener can only reduce mass by about fifty percent. Maybe in a hundred years we'll have something practical..."

"In a hundred years we'll be back to living in straw huts and herding goats," said James, looking over Stuart's shoulder at the results his calculator had come with. Karen also leaned closer to look and her face went white. "Our descendants will look back on a golden age when we flew through the sky and talked to machines."

Eddie found himself following the conversation as the shock began to wear off and he became aware of the world again. "How much energy would your city sized mass dampener need?" he asked. "You needed a car's fuel cell for your prototype."

"The original alien dampeners only needed a tiny amount of power," said Frank. "The power lines leading to them were tiny threads of superconductor just a few atoms wide. You wouldn't have been able to power a wristwatch with the power you could feed through them!"

"So, what would happen if you fed more power into them?"

"They'd burn out, I expect."

"Would they? You said most of the energy went elsewhere. You fed enough energy into your prototype that it should have melted, but it only became rather warm. What happens if you feed more energy into your prototype? I assume you tried it."

"The area of effect grew larger, but the mass inside was still reduced by the same amount."

"How big were you able to get the area of effect?"

The others stared at each other as they realised what he was suggesting. "We never pushed it to the limit," said Ben. "We were afraid of burning it out. It was our prototype, we didn't want to damage it."

"But you could build another prototype if you had to," said Eddie.

"Oh yes! Easily, now that we know how."

"Then I think the time's come to push it to the limit," said Eddie. "Let's put as much power as we can into it and see what happens."

Ben laughed. "The philosophy of the mad scientist," he said.

"If the world's going to be saved, it's the mad scientists who'll do it. I think we can assume that whatever happens to your reverse engineered prototype will also happen to the original alien mass dampeners. I'm going to hook that prototype up to the mains. Who's with me?"

The others stared at each other again. "Hell, let's do it!" said James. "What have we got to lose?"

He and Eddie rose from their seats and led the way towards the door. The others started to follow him, but the scenes still being displayed on the television had an almost hypnotic attraction that it was hard to tear their attention from. "Come on!" said James impatiently. "What's happening up there is so big it'll take hours to happen. The compression quakes are over. Soon, there'll be nothing to look at except a layer of impenetrable clouds."

"He's right," said Ben. "Let's go." He followed the first two men out of the room, and this time the others followed.

☆☆☆

It took over an hour for Samantha to get her frightened neighbours out of the house, and she plugged the freezer in again with relief. She was feeling rather proud of herself that she'd managed to avoid letting them know the full nightmare of what was to come and had managed to reassure them without actually lying. A week from now, of course, they would discover the awful truth for themselves, but she'd cross that bridge when she came to it.

She was thinking about putting Lily to bed for the night when the doorbell rang again. "There are some gentlemen hat the door, M'lady," the house computer told her. "Nobody we know, I'm afraid."

Samantha cursed. More neighbours! How many times was she going to have to go through this? She wasn't going to let them into the house this time, though. She'd cossetted them enough, and she needed time with her daughter. Let them talk to her first group of guests, they could pass on what she'd told them already. She went to the door therefore, composing in her mind the words she'd use to send them on their way.

The two men on her doorstep weren't neighbours, though. They were serious looking men in black suits, and there was a large, black car parked out in the street. "Samantha Kumiko?" one of them asked.

"Yes? What do you want?"

"You are the Samantha Kumiko who is an astronomer and an expert on the moon?"

"Yes, that's right."

"My name is Henry Bayliss and this is Andrew MacNally. We work for the government. We've been ordered to escort you to a meeting of the COBR committee to discuss the current situation with the moon. Will you come with us, please?"

"Wait, wait! What? The COBR committee? You mean in Downing Street? With the Prime Minister?" This can't be real, she thought. There must be some mistake! But then she reflected again on what was about to happen, the effect the moon's new orbit would have on the world, and she realised that of course it was real. Despite popular opinion, government ministers weren't fools. They knew that what was happening was huge, and they wanted to know what to expect, what they would have to plan for. And, all modesty aside, she knew that she was the world's greatest expert on the moon. She should have expected this.

"I'll need to arrange a babysitter for my daughter. That might take some time, I'm afraid..."

"Bring her with you. Someone will look after her while you're in the meeting."

Samantha felt a little hand slip into hers and looked down to see Lily standing beside her, looking nervously up into her face. "She's tired, it's her bedtime. And I don't want to leave her among strangers right now. She's frightened, she needs me to be with her."

"Don't worry, Miss, she'll be fine. We often have people bringing their kids with them. She'll probably have a great time, and she'll have one hell of a story to tell when she's older."

"I'm afraid we have to insist, Miss," said the other man. "Can't keep the Prime Minister waiting."

Samantha saw that he was serious. They would probably carry her off by force if she refused. Best to make the best of it, then. "Very well," she said. "I just have to turn some things off and lock up. I won't be a minute." She took Lily back inside and the two men followed her, perhaps thinking she might try to escape out the back door. They watched her intently as she brought the telescope inside and locked the door, but then they saw the television, still showing the pictures being sent back by the space telescope. "Bloody Hell!" the first one said, and Samantha saw that he was genuinely shocked.

The image was in shades of grey, as the telescope used wavelengths of light able to penetrate the clouds that now completely covered the moon. The magma geyser had doubled in size and had been joined by a number of others, standing in a small cluster in the middle of a lake of molten rock that filled the image. Its size was made evident by the slowness with which fiery globs of rock were thrown upwards, darkening as they cooled, and then the lazy, viscous splashes they made as they fell back to the surface. Part of the slowness was due to the moon's low gravity, of course, but it was still clear that what they were seeing was a seismic event on a colossal scale.

As if that wasn't dramatic enough, the roiling clouds above the geysers were lit with continuous lightning discharges, each one many times larger than anything that had been seen on Earth in human history. After countless aeons of slumber, the moon was now alive with apocalyptic activity on a scale to stun even the most jaded, cynical or philosophical man. Samantha didn't doubt that the two government men had seen their share of violence and had probably thought they were beyond being awed by any purely natural spectacle, but now they were staring at the television screen like children, their eyes staring as they struggled to process what they were seeing.

"Thank God that's all happening a quarter of a million miles away," said the first man, tearing his attention away with an effort. "That can't hurt us down here, can it?"

"Then why's the PM want to see her?" asked the other. "The emergency committee! COBR only meets when something big's going down." He turned to Samantha. "What's it mean?" he demanded. "What's it mean for us?"

Samantha turned off the television and unplugged it. "I'll tell you in the car," she said. "I'm finished here. Let's go."

☆☆☆

By the time they arrived at the airport, fifteen minutes later, the two men were looking genuinely scared. "We live down by the coast," the first one said. "We've been thinking of moving inland for a long time, because of the rising sea levels. You say we've only got about a week before... Before what you said?"

"Six to ten days before it's at its worst, depending on how much the moon's orbit's been changed. It'll probably be bad enough a day or two before and after that."

The man began to curse, stopped himself when he remembered there was a six year old girl in the car with them. "My sister lives in Swindon, we might go move in with her. Will that be high enough, do you think?"

"Can't say yet. We don't know how badly the moon's orbit's been affected yet, but Swindon will almost certainly be better than Bristol."

"Are you going to move?" asked the second man. "You know better than anyone what's coming..."

"The highland areas are going to be crowded with refugees. Millions of people living in tent cities. I live at the top of a hill, thirty metres above sea level. If the tides are high enough to get us here, it probably won't matter where in the world we move to." Both men nodded soberly.

There was a helicopter waiting for them at the airport. The two men drove the car straight onto the runway, then got out and held the door open for her while Samantha and Lily got out. The helicopter had its engine running. The wind from its spinning rotors tugged at their clothing and the noise from its engine meant that they had to shout to be heard. "That's your ride to London!" the first man shouted. "It'll take you to London City airport, where another car will meet you and take you to Downing Street."

"Thank you," said Samantha. "And good luck."

"You too." The man then got back in the car, which turned and drove away.

There was a man standing beside the helicopter. Samantha took Lily's hand and walked over to him. He indicated the open door and Samantha helped Lily to climb in. Then she followed after her. The man then climbed into the cockpit.

There was another man inside the cabin, waiting for them. He closed the door to shut out most of the noise. "Welcome aboard, Mrs Kumiko. Thank you for coming."

"I got the impression I didn't have much of a choice." She sat in one of the sumptuous, padded seats, next to Lily, and helped her put her seatbelt on. The helicopter's passenger cabin was luxurious, with wood effect panelling on the bulkheads and a white carpet under their feet. There was even a drinks cabinet, she saw, although their host made no move towards it.

"I'm sorry about that," he said, "but this is a matter of national security. If we'd had more time we'd have been more civilised about it. As it is, I can only apologise and ask for your understanding."

"That's okay. The fact is, I probably know better than you do just how urgent the situation is and I'm actually rather relieved that the government's taking it seriously."

The man looked out the window, up into the sky. The moon was just disappearing behind some clouds, but he got enough of a look to see that the familiar seas and highlands had entirely disappeared. The moon was now a featureless disk of grey. It looked like a dull, silvery ball bearing hanging in the sky. "Looks so harmless," he said. Then he gave a guilty start. "Oh! Do forgive my bad manners. My name is Manners. Captain Miles Manners."

"Pleased to meet you, Captain." The helicopter's engine grew louder as the pilot told the autopilot to lift off, and then the passengers felt a gentle lurch as the aircraft climbed into the sky.

It was Lily's first time in a helicopter, and she stared out the window as the ground receded beneath them, oblivious to all else. Samantha, though, was more concerned with the current emergency and pulled her phone from a pocket. "Do you mind?" she asked, looking up at the Captain.

"Not at all. Please." He gestured at the phone and Samantha smiled gratefully as she called Neil Arndale.

"Neil!" she said when he answered. "What have we got?"

"We're getting the first results from the Lagrange probes," her supervisor replied, and there was a note to his voice that Samantha had never heard before. She thought it might have been fear. "We're watching the moon's motion against the background stars. We still need to confirm it, but I think we've got its new velocity pretty much nailed down." There was a pause before he spoke again, as if he was about to pronounce a death sentence. "Point six two kilometres per second."

Samantha felt her face go pale. She'd pretty much known beforehand. The mass of the Scatter Cloud, the speed it had been moving... She'd been able to do the calculations in her head, but there'd been the hope that she might have been wrong. Maybe the main bulk of the cloud had missed the moon, or perhaps the individual cloud particles had been so small and dense that they'd passed right through the moon without imparting their full momentum to it. Just a dream, but she'd been clutching at any hope, no matter how vain. Now, though, those hopes were dashed, and everything she'd dreaded had become as inevitable as tomorrow's sunrise.

"That's about two thirds what it was," she said, surprising herself with how calm her voice sounded. She glanced over at Lily, still staring out the window.

"Yeah."

"How could the moon survive something like that?"

"The cloud applied itself evenly to the whole face of the moon, and the force was applied deep below the surface. A very effective way to carry out a course change."

"I'm afraid I'm not really in the mood to appreciate it."

"Yeah. We're getting ready to evacuate the university. We're way too close to the coast here. Don't bother coming back. I'll send you a mail when we've got a new home sorted out, if we get a new home. The authorities are likely to have other priorities in the weeks to come."

"Yeah. Astronomy may be a luxury humanity just won't be able to afford for a generation or two. We are going to come through this, aren't we? Mankind, I mean."

"Of course we are! Humans are adaptable creatures. It's going to be hard, I don't need to tell you that. The transition period will be tough, casualties will be massive, but eventually the survivors will adapt to the new reality. A century from now, people will be watching movies about this on their tellies from the comfort of their living rooms, just like we watch movies about the second world war today."

"I hope so. Good luck, Neil! Take care, you and your family."

"And you, Sam! Hope to see you soon." Neil cut the connection and the screen went dark.

"What was he talking about?" asked Captain Manners. Samantha looked across at him, and saw that he'd been greatly disturbed by the conversation. "Massive casualties? What did he mean?"

Samantha sighed, and for the second time within the space of half an hour she explained in full graphic detail what was about to happen while the helicopter flew across the dark, night time English countryside.