"So, why are you telling me?"
"Because you speak Latin and ancient Greek. Because of the limitations of relativity, this one last chance commences on Rhodes in the first century."
"How could that help?" It was unbelievable that anything on Rhodes in the first century could affect the outcome of an event in the twenty-fifth century.
"By getting alien help. This new time-line goes through an alien civilization that we know was exterminated," Professor Grenfell explained.
"You mean. ?"
"I mean that a newly generated timeline shows that if this Roman accepts an opportunity to be abducted in a space vehicle, and if he can get to this planet Ulse, and if once there he does certain things, he may return and with one other he could solve this problem for us," Dr Chu said.
"And why do we think this Roman could solve a problem that an advanced civilization couldn't?" Athene asked. "It just isn't possible."
"No, just highly improbable," Chu shrugged.
"In fact," Professor Grenfell added with a wry smile, "following the paradox, a future timeline for that civilization has formed with a similar intensity as this Roman's alternative timeline, which is consistent with this Roman's arrival altering the future of this alien civilization."
"But in reality, this Roman didn't do any of this, did he?" Athene asked.
"No, he didn't, seemingly because sufficient cause could not be put in place until the paradox occurred. So you, Pallas Athene, have to play Goddess again."
"Why do you think I can make the difference?"
"First, that a new timeline appears means that it commenced with something that only happened because the paradox happened, which means someone has to put that cause in place. We hope you can do that."
"So what do you want me to do?"
"Several things have to happen," Professor Grenfell explained. "To get to this alien civilization, the Roman has to board a space ship. As it happens, an alien zoo-specimen collector was nearby. I have enticed that ship to land at a place where our Roman could be abducted. ."
"How did you manage that?" Athene asked.
"I played on his greed," Grenfell smiled. "There is to be a major battle near where we hope to get our Roman abducted. I have persuaded this collector to visit the site and record the battle. He could make far more from the rights to that recording than he could ever make selling specimens, so the alien will land and put up recording equipment."
"That's cunning," Athene said.
"So that gets us an alien space ship on the site. You must persuade the Roman to be abducted."
"Even if he gets abducted," Athene replied dubiously, "what good does that do?"
"According to Ulsian law, the abduction of a person whose work could alter the path of his civilization is a major crime, in which case both the perpetrator and the victim have to be taken to Ulse. So, the key to getting him there is to turn him into somebody who otherwise could have altered the future of Earth."
"And that something is?"
"Science is our best bet," Dr Chu said, "because our subject almost made a discovery. You have to persuade him to do so."
"That sounds simple," she said sarcastically.
"Yes, and there's more. This Roman was highly original as a military strategist, and that must not change."
"The science gets him noticed by the aliens," Grenfell explained, "but once he gets there he has to do something to change the aliens' future. That will not be science."
"It won't be military either," Black muttered. "They'll have got past swords."
"Yes, they got past swords," Grenfell shook his head in despair, "but it could be like the so-called butterfly effect. Maybe he inspired someone to do something different. These aliens had a record of continuous losses until they were wiped out. Maybe. ."
"We don't know what he did, or, with the other way of looking at it, is yet to do, because the alternative timeline's too weak to visualize," Dr Chu interrupted, "but we get more than one go at this. If I'm correct and the science is critical, because probabilities of different steps are multiplied together, fixing that will strengthen the overall signal, then we can see what we have to do next. As an aside, we know this works because diverting that space ship has already improved the signal strength of this alternative timeline. We know we can improve our chances."
"What do we think happened to this Roman?" Athene asked.
"During the invasion of Britain he and some close family members were killed by Celts," Dr Chu explained, "and until then, as much as possible must remain unchanged so we don't simply replace one paradox with another. Some of Vespasian's men caught up with the Celts and killed all of them, so we're in luck: since everybody in this incident dies, our altering what happened by taking the Roman and any others off-world won't create another paradox. Since we get more than one go, we try for one big change at a time, so two guesses don't cancel out each other."
"So what do I do specifically?"
"This new time-line commences at a temple to. . like to guess?"
"How would I know?" she frowned.
"To you!"
"What?"
"The Roman falls asleep between two large stone objects and underneath a statue in a disused temple to Pallas Athene," Chu smiled, "which I thought might appeal to you. Do what you can just before he wakes, then if the overall probability of resolving the paradox improves, the intensity of the line increases and we get more detail. Then you can have another go, a little earlier. You get about six attempts. After that, well. ."
"What do I know about this Roman?"
"Fortunately, quite a bit, because he featured strongly in a thesis about why Roman science did not advance. Four students spent quite a lot of time viewing him, and we have their recordings. I'll download the notes into your notebook, if you wish."
"So you want me to give him a quick physics lesson?"
"No! I am afraid he must make the discovery himself. You must inspire him."
"I don't want to be unduly negative," Athene said, "but I just don't believe you can turn a Roman soldier into a leading physicist. ."
"We know it's not easy," Chu nodded, "but it's our only chance to undo this disaster. According to the thesis, he was toying with the heliocentric theory, and had a debate with his teacher. He lost that debate when his teacher provided physical proof that the Earth could not travel around the sun and he gave up; his attitude could be summarized as Aristotle was obviously right, and in any case, who cares? So you must inspire him to greater things and also give him information that will get him through a couple of crises."
"There's another reason he must prove his heliocentric theory," Grenfell added. "We're asking a Roman to board an alien space ship and comprehend what's going on. When told, he must accept there are other planets going around other stars."
"We're asking him to do what Galileo did from roughly the same starting point," Chu added. "He nearly did it, so it's possible, if he can undo Aristotle's errors."
"But he didn't do it," Athene pointed out.
"The hardest part of making a discovery," Dr Chu smiled, "is convincing yourself that you can, that it's possible."