Rotating Cylinders and the Possibility of Global Causality Violation
This story has a catchy title. I stole it from a mathematics paper by Frank J. Tipler.
"Three hundred years we've been at war," said Quifting, "and I have the means to end it. I can destroy the Hallane Regency." He seemed very pleased with himself, and not at all awed at being in the presence of the emperor of seventy worlds.
The aforementioned emperor said, "That's a neat trick. If you can't pull it off, you can guess what penalties I might impose. None of my generals would dare such a brag."
"Their tools are not mine." Quifting shifted in a valuable antique massage chair. He was small and round and completely hairless: the style of the nonaristocratic professional. He should have been overawed, and frightened. "I'm a mathematician. Would you agree that a time machine would be a useful weapon of war?"
"I would," said the emperor. "Or I'd take a faster-than-light starship, if you're offering miracles."
"I'm offering miracles," said Quifting, "but to the enemy."
The emperor wondered if Quifting was mad. Mad or not, he was hardly dangerous. The emperor was halfway around the planet from him, on the night side. His side of the meeting room was only a holographic projection, though Quifting wouldn't know that.
Half a dozen clerks and couriers had allowed this man to reach the emperor's ersatz presence. Why? Possibly Quifting had useful suggestions, but not necessarily. Sometimes they let an entertaining madman through, lest the emperor grow bored.
"It's a very old idea," Quifting said earnestly. "I've traced it back three thousand years, to the era when spaceflight itself was only a dream. I can demonstrate that a massive rotating cylinder, infinite in length, can be circled by closed timelike paths. It sees reasonable that a long but finite--"
"Wait. I must have missed something."
"Take a massive cylinder," Quifting said patiently, "and put a rapid spin on it. I can plot a course for a spacecraft that will bring it around the cylinder and back to its starting point in space and time."
"Ah. A functioning time machine, then. Done with relativity, I expect. But must the cylinder be infinitely long?"
"I wouldn't think so. A long but finite cylinder ought to show the same behavior, except near the endpoints."
"And when you say you can demonstrate this..."
"To another mathematician. Otherwise I would not have been allowed to meet Your Splendor. In addition, there are historical reasons to think that the cylinder need not be infinite."
Now the emperor was jolted. "Historical? Really?"
"That's surprising, isn't it? But it's easy to design a time machine, given the Terching Effect. You know about the Terching Effect?"
"It's what makes a warship's hull so rigid," confirmed the emperor.
"Yes. The cylinder must be very strong to take the rotation without flying apart. Of course it would be enormously expensive to build. But others have tried it. The Six Worlds Alliance started one during the Free Trade period."
"Really?"
"We have the records. Archeology had them fifty years ago, but they had no idea what the construct was intended to do. Idiots." Quifting's scowl was brief. "Never mind. A thousand years later, during the One Race Wars, the Mao Buddhists started to build such a time machine out in Sol's cometary halo. Again, behind the Coal Sack is a long, massive cylinder, a quasi-Terching-Effect shell enclosing a neutronium core. We think an alien race called the Kchipreesee built it. The ends are flared, possibly to compensate for edge effects, and there are fusion rocket motors in orbit around it, ready for attachment to spin it up to speed."
"Did nobody ever finish one of these, ah, time machines?"
Ouifting pounced on the word. "Nobody!" and he leaned forward, grinning savagely at the emperor. No, he was not awed. A mathematician rules his empire absolutely, and it is more predictable, easier to manipulate, than any universe an emperor would dare believe in. "The Six Worlds Alliance fell apart before their project was barely started. The Mao Buddhist attempt-- well, you know what happened to Sol system during the One Race Wars. As for the Kchipreesee, I'm told that many generations of space travel killed them off through biorhythm upset."
"That's ridiculous."
"It may be, but they are certainly extinct, and they certainly left their artifact half-finished."
"I don't understand," the emperor admitted. He was tall, muscular, built like a middleweight boxer. Health was the mark of aristocracy in this age. "You seem to be saying that building a time machine is simple but expensive, that it would handle any number of ships. It would, wouldn't it?"
"Oh, yes."
"And send them back in time to exterminate one's enemies' ancestors. Others have tried it. But in practice, the project is always interrupted or abandoned."
"Exactly."
"Why?"
"Do you believe in cause and effect?"
"Of course. I... suppose that means I don't believe in time travel, doesn't it?"
"A working time machine would destroy the cause and effect relationship of the universe. It seems the universe resists such meddling. No time machine had ever been put into working condition. If the Hallane Regency tries it something will stop them. The Coal Sack is in Hallane space. They need only attach motors to the Kchipreesee device and spin it up."
"Bringing bad luck down upon their foolish heads. Hubris. The pride that challenges the gods. I like it. Yes. Let me see..." The emperor generally left war to his generals, but he took a high interest in espionage. He tapped at a pocket computer and said, "Get me Director Chilbreez."
To Quifting he said, "The director doesn't always arrest enemy spies. Sometimes he just watches 'em. I'll have him pick one and give him a lucky break. Let him stumble on a vital secret, as it were."
"You'd have to back it up--"
"Ah, but we're already trying to recapture Coal Sack space. We'll step up the attacks a little. We should be able to convince the Hallanes that we're trying to take away their time machine. Even if you're completely wrong-- which I suspect is true-- we'll have them wasting some of their industrial capacity. Maybe start some factional disputes, too. Pro- and anti-time-machine. Hah!" The emperor's smile suddenly left him. "Suppose they actually build a time machine?"
"They won't."
"But a time machine is possible? The mathematics works?"
"But that's the point, Your Splendor. The universe itself resists such things." Quifting smiled confidently. "Don't you believe in cause and effect?"
"Yes."
Violet-white light blazed through the windows behind the mathematician making of him a sharp-edged black shadow. Quifting ran forward and smashed into the holograph wall. His eyes were shut tight, his clothes were afire. "What is it?" he screamed. "What's happening?"
"I imagine the sun has gone nova," said the emperor.
The wall went black.
A dulcet voice spoke. "Director Chilbreez on the line."
"Never mind." There was no point now in telling the director how to get an enemy to build a time machine. The universe protected its cause-and-effect basis with humorless ferocity. Director Chilbreez was doomed; and perhaps Quifting had ended the war after all. The emperor went to the window. A churning aurora blazed bright as day, and grew brighter still.