Timescape

Markham saluted with the stout. After this silent toast he said, “Oh yes, Renfrew. What Wheeler and Feynmann didn’t notice was that if you send a message back which has nothing to do with shutting off the transmitter, there’s no problem. Say I want to place a bet on a horse race. I’ve resolved that I’ll send the results of the race back in time to a friend. I do. In the past, my friend places a bet and makes money. That doesn’t change the outcome of the race. Afterward, my friend gives me some of the winnings. His handing over the money won’t stop me from sending the information—in fact, I can easily arrange it so I only get the money after I’ve sent the message.”

“No paradox.”

“Right. So you can change the past, but only if you don’t try to make a paradox. If you try, the experiment hangs up in that stuck-in-between state.”

Peterson frowned. “But what’s it like? I mean, what does the world seem like if you can change it round?”

Markham said lightly, “Nobody knows. Nobody’s ever tried it before.”

“There were no tachyon transmitters until now.”

“And no reason to try to reach the past, either.”

“Let me get this straight. How’s Renfrew going to avoid creating a paradox? If he gives them a lot of information, they’ll solve the problem and there’ll be no reason for him to send the message.”

“That’s the trick. Avoid the paradox, or you’ll get a stuck switch. So Renfrew will send a piece of the vital information—enough to get research started, but not enough to solve the problem utterly.”

“But what’ll it be like for us? The world will change round us?”

Markham chewed at his lower lip. “I think so. We’ll be in a different state. The problem will be reduced, the oceans not so badly off.”

“But what is this state? I mean, us sitting here? We know the oceans are in trouble.”

“Do we? How do we know this isn’t the result of the experiment we’re about to do? That is, if Renfrew hadn’t existed and thought of this idea, maybe we’d be worse off. The problem with causal loops is that our notion of time doesn’t accept them. But think of that stuck switch again.”

Peterson shook his head as though to clear it. “It’s hard to think about.”

“Like tying time in knots,” Markham conceded. “What I’ve given you is an interpretation of the mathematics. We know tachyons are real; what we don’t know is what they imply.”

Petersen looked around at the Whim, now mostly deserted. “Strange, to think of this as being an outcome of what we haven’t done yet. All looped together, like a hooked rug.” He blinked, thinking of the past, when he had eaten here. “That coal stove—how long have they had that?”

“Years, I suppose. Seems like a sort of trademark. Keeps the place warm in winter, and it’s cheaper than gas or electricity Besides, they can cook at any time of day, not just the power hours. And it gives the customers something to watch while they’re waiting for their orders.”

“Yes, coal’s the long-term fuel for old England,” Peterson murmured, apparently more to himself than Markham. “Bulky though.”

“When were you a student here?”

“In the ’70s. I haven’t been back very often.”

“Have things changed much?”

Peterson smiled reminiscently. “I dare say my rooms haven’t changed much. Picturesque view of the river and all my clothes get moldy from the damp…” He shook off his mood. “I’ll have to be getting back to London soon.”

They elbowed through the students to the door and out into the street. The June sunshine was dazzling after the pub’s dark interior. They stood for a moment, blinking, on the narrow sidewalk. Pedestrians stepped off into the street to walk past them and cyclists swerved around the pedestrians with a trilling of bells. They turned left and strolled back towards King’s Parade. On the corner opposite the church, they paused to look in the windows of Bowes & Bowes bookstore.

“Do you mind if I go in for a minute?” Peterson asked. “There’s something I want to look for.”

“Sure. I’ll come in, too. I’m a bookstore freak; never pass one by.”

Bowes & Bowes was almost as crowded as the Whim had been earlier, but the voices here were subdued. They edged cautiously between the knots of students in black gowns and pyramids of book’s on display. Peterson pointed out one on a less conspicuous table towards the back of the store.

“Have you seen this?” he asked, picking up a copy and handing it to Markham.

“Holdren’s book? No, I haven’t read it yet, though I talked to him about it. Is it good?” Markham looked at the title, stamped in red on a black cover—The Geography of Calamity: Geopolitics of Human Dieback by John Holdren. In the bottom right corner was a small reproduction of a medieval engraving of a grinning skeleton with a scythe. He thumbed through it, paused, began to read. “Look at this,” he said, holding the book out to Peterson. Peterson ran his eyes over the chart and nodded.

Markham whistled softly. “Is it accurate?”

“Oh, yes. Underestimated, if anything.”

Peterson moved towards the back of the store. A girl was perched on a high stool adding a column of figures into an auto-accountant. Her fair hair hung forward, hiding her face. Peterson studied her covertly while leafing through some of the books in front of him. Nice legs. Fashionably dressed in some frilly peasant style he disliked. A blue Liberty scarf artfully arranged at her neck. Slim now, but not for many more years, probably. She looked about nineteen. As though aware of his gaze, she looked up straight at him. He continued to stare at her. Yes, nineteen and very pretty and very aware of it, too. She slid from her stool and, clutching papers defensively to her chest, came over to him.

“May I help you?”

“I don’t know,” he said with a slight smile. “Maybe. I’ll let you know if you can.”

She took this as a flirtatious overture and responded with a routine which probably, he reflected, was a knock-out with the local boys. She turned away from him and looked back over her shoulder, saying huskily, “Let me know then.” She gave him a long look from under her lashes, then grinned cheekily and flaunted her ways towards the front of the store. He was amused. At first, he had really thought that she intended her coquettish routine seriously, which would have been ludicrous if she hadn’t been so pretty Her grin showed that she was playacting. Peterson felt suddenly in very good spirits and almost immediately noticed the book he had been looking for.

He picked it up and went to look for Markham. The girl was with two others, her back to him. Her companions were laughing and staring. They obviously told her he was watching them, because she turned to look at him. She really was exceptionally pretty. He made a sudden decision. Markham was browsing through the science fiction selection.

“I have a couple of errands,” Peterson said. “Why don’t you go on ahead and tell Renfrew I’ll be there in half an hour?”

“Okay, fine,” Markham said. Peterson watched him as he strode out the door, moving athletically, and disappeared into the alley behind the building known as Schools.

Peterson looked for the girl again. She was serving someone else, a student. He watched as she went through another routine, leaning forward more than was necessary to write a receipt, quite enough to enable the student to look down the front of her blouse. Then she straightened up and looked quite offhand as she gave him his book in a white paper bag. The student went out, with a disconcerted look on his face. Peterson caught her eye and lifted the book in his hand. She slammed the cash register shut and came over to him.

“Yes?” she asked. “Have you made up your mind?”

“I think so. I’ll take this book. And maybe you could help me with something else. You live in Cambridge, do you?”

“Yes. You don’t?”

“No, I’m from London. I’m on the Council.” He despised himself immediately. Like shooting a rabbit with a cannon. No artistry at all. Anyway, he had all her attention now, so he might as well take advantage of it. “I