Athene's Prophecy (Gaius Claudius Scaevola Trilogy) by Ian Miller Page B

generate storms in the middle," Timothy nodded. Now was the time to be mildly encouraging. Possibly this was a lucky guess, and it was a pity he had to fix on that heretic, but on the other hand here was something quite unusual: a Roman sufficiently interested in Greek science to actually read it. There was also a practical reason: there was no point in pushing this young man into violence. "But there's more. Rain may wash away the side of a hill but nothing builds it up. Everything is gradually changing, and can never go back to the beginning. Even life is changing."
    "It is?"
    "It is. Think! Give me an example."
    "I didn't even know it was," Gaius grumbled. "How can I be expected to . . ."
    "An enemy army appears on your left flank and you didn't even know it was there," Timothy said harshly. "What do you do? Bleat?"
    "That's not . . ." Gaius suddenly paused, then grinned. "Yes, I can think of a change. Sheep. Wild sheep do not have wool, but rather they have hair!"
    "Strictly speaking," Timothy said, "that's not quite true, but it's an example. Find out what you can about sheep. Don't tell me, just work it out for yourself. Sooner or later you will have to use that knowledge, but I'm not going to tell you when. Now, the most important contribution from Anaximander was contraries. Go, read up what you can about contraries. I want you to think generally, but also concentrate on locomotion." Gaius nodded, and as he left the room, Timothy mumbled to himself, "That should give him something to do for a while."
    * * *
    Gaius also had occasional sessions with the Greek Geminus, who was also somewhat intrigued by a Roman who wished to be a soldier and who seemed interested in Aristarchus. At first, Geminus announced that he would only teach if Gaius successfully showed aptitude and interest, and immediately began discussing what a hypothesis, a postulate, and a theorem were, then what a line was, a surface, and so on. Then he gave Gaius some observational data on planetary motion and asked him to formulate an explanation in terms of Aristarchus' hypothesis. Gaius began to find his days were filling.
    It took more than a week looking at pages and pages of data before he was ready to make calculations, then he used a surprising amount of papyrus to record the calculations he made on wax tablets, and with string and markings on a large floor, but eventually he was able to return to Geminus and inform him that he had something: the paths of the planets were consistent with the Aristarchus model, and the reason they turned around and went backwards was because the Earth was travelling inside their orbits, and passed them. He showed Geminus how he had worked out how the data showed how long each planet took to go around the sun, and from their observed paths, he made an estimate of their distances relative to the Earth-Sun distance.
    "The distance estimates are a bit rough," Gaius admitted. "I took observations from the retrograde motion, predicted the background of the planet from that point on the Earth's orbit, and selected data from where it actually was later. I know how long each planet takes to return to the same position, but I am not sure that the observed angles are very good, because that wasn't why they were measured. The distances are very large, so maybe they're wrong."
    "Very good," Geminus nodded, after he checked what Gaius had done. "If you believe Aristarchus, your geometry seems to be correct, even if the data are wrong. Anything else?"
    "Yes," Gaius nodded, "at least I think so. If we look at how far Mars is, and how much it dims, then consider how bright Jupiter and Saturn are, they must be huge if they shine by reflected light. And one last thing: if the stars are suns, as many suspect, then they must be very far away, and not only that, because they have different brightness, they can't all be the same distance. Putting them all on one sphere would be wrong."
    If nothing else, this pleased Geminus, for he had