"Because the planets are on epicycles that move on the spheres."
"And not the slightest sign of spheres or of anything driving these epicycles. It's easier to think of them all going around the sun with the inner ones going faster, in which case the backwards motion is easily explained." Gaius waited for Timothy to ask him to prove it, in which case he could show the workings he had had to do for Geminus, but Timothy did not do so.
"Easier does not mean more correct," Timothy warned. "We'll deal with that heresy later."
"You Greeks have a way," Gaius nodded. "I understand that Anaxagoras was accused of denying the Gods, and condemned to death for saying these things about the stars."
"But saved by Pericles."
"Then exiled," Gaius laughed. "You are taking a risk."
"You'd have to let me go to exile me," Timothy countered.
"I supposed that leaves condemning to death!"
"I suppose," came the sour response. "Anyway, according to Anaxagoras the moon was as large as the Peloponnese, and the sun, perforce, much much larger."
"Much, much larger," Gaius agreed in a soothing sarcastic tone.
"It was Democritus and Parmenides who worked out that the Earth was circular," Timothy persisted. "As you have noted, ships hulls go out of sight first, the masts last."
"And the lunar eclipse will be the Earth's shadow," Gaius offered, "from which Aristarchus deduced the Moon was half as big as the Earth."
"Correct," Timothy nodded. "We've already discussed the heresy of Aristarchus, but we must discuss what we think happens. Each of the planets is set on a heavenly sphere. ."
"Which rotates around the Earth every day, meaning the distant objects must really travel extraordinarily fast."
"Not necessarily," Timothy wagged his finger. "There is another option. Heraclides of Pontus, who was a pupil of the great Aristotle, argued that the Earth rotates on its axis like a spinning ball, which makes everything else looks as if it is going around the Earth. Unfortunately, he then spoiled it by arguing that Venus goes around the sun."
"Of course," Gaius challenged, "if you believe the great Aristarchus," and he laced on the sarcasm here, "and the planets go around the sun, Venus has to too. And if Venus is closer to the sun than we are, that explains why it is the morning star or the evening star, in regular periods."
"Yes, heresies are often quite good at explaining things," Timothy said. "Unfortunately Heraclides was not a very good pupil because Aristotle had already proven that the Earth cannot rotate."
"If you say so," Gaius remarked nonchalantly. However, he watched a slight twitch around Timothy's eyes. Yes, Timothy thought that this was an important point. He must have a response to it when they had their debate. He smiled inwardly, as he saw Timothy was tempted to reply, but also tempted to keep his argument for later. He had to say something, so he decided to be facetious. "And I suppose the Milky Way is some sort of smudge on one of your crystalline spheres?"
"Democritus had a simple answer to that," Timothy said. "He suggested that the Milky Way was a collection of very distant stars. Would you care to comment?"
"It seems to me," Gaius said, after a while, "that since the great Aristotle said the stars were on a heavenly disc, it would be sensible if they were all the same distance."
"It might be sensible, but it doesn't have to be," Timothy pointed out. "Aristotle was fairly firmly convinced that the stars are at different distances."
"Which requires an enormous number of spheres," Gaius countered, "that all have to move in a constant pattern."
"I shall concede that that is difficult, but it's not impossible," Timothy said.
"Yet the question arises," Gaius said softly, "that all these different stars have to be on different spheres that have to travel at very high speeds that also depend on the latitude with respect to the Earth. Thus the Pole Star hardly moves, and is on a really small path, while a star over the equator has a huge distance to travel, and all the stars have to maintain the same pattern."
"I agree that that is odd," Timothy said, "and that is also a strong point in favour of Aristarchus."
"There are just too many coincidences," Gaius shrugged. "The heliocentric theory is so much simpler."
"I am glad you think so. So you see that now we have two models, hence we should be able to decide which applies based on logic."
"We should?" a puzzled Gaius asked.
"We can," Timothy said emphatically. "Something for you to contemplate. The key lies in the physics you have already learned. If Aristarchus was correct, something else should happen which, fortunately for me, it does not. Think about why something goes around in circles and see if you can work out the underlying physics."
Chapter 15
When Gaius walked into the room, he was surprised to see the room being almost entirely taken up by a huge table that was entirely covered by a model map. The west side was blue and flat, and presumably the sea. In the centre of the coast, towards the west, was what appeared to represent a large port city. There was a peninsula which rose up a few inches from the sea, and which overlooked a bay. On the bay a number of tiny model ships appeared to float, and a close examination of the peninsula showed tiny stone walls; the peninsula had clearly been heavily fortified. A walled city could be seen on the other side of the bay, complete with tiny buildings, a small stone temple, and outside the wall what appeared to be tiny farms. There were forested hills scattered about with roads through them, there was a river, there were two large green valleys with villages in them inland, then further inland, the forest cover lightened to give lightly treed grass-land, or at least that was how he interpreted the model. Then below the board was a box containing model soldiers, model horses, in either red or blue, and a cup with dice.
"So, how do you like what some of your money's gone on?" Timothy asked.
"The workmanship's quite extraordinary," Gaius gasped. "What's it for?"
"It's a country upon which you may play war games," Timothy smiled. "We shall assume you are a Roman Legate, with one legion, and you Romans have just conquered this area. You and your troops reside safely in this fort," he continued, then looked at Gaius and asked, "You prefer red or blue?"
"I'll be red," Gaius shrugged. "Does it matter?"
"No," Timothy said, and picked all the red symbols from the box and placed them in the fort. "These," he said, showing Gaius ten large model soldiers, "are ten cohorts of infantry, each with six centuries. I know there are usually nine, but the first is double-sized, and you can be strictly accurate and use two models to fix the first. Any cohort can be split into centuries, and we have little soldiers to represent them, although," he added, "we know Romans can't count, and there are seldom a hundred men in a century."
"We can count. It's just that we can't afford the full complement. Fortunately eighty Romans are easily capable of dealing with more than a hundred Greeks!"
"I had a feeling that was coming," Timothy said, clearly pleased with himself. "You just won me a small bet."
"Pleased to oblige."
"Now," Timothy continued, "these two horses represent two cavalry units, we have five models representing five hundred auxiliaries, and here we have a few scouts and spies. You will deploy these according to certain rules. There is a corresponding board in the other room for your opponent and each board will show its own resources, and what is known about the others. I shall act as an intermediary, conveying the moves in one room to the other. This board here represents not what is going on, but what you are told is going on, and the two are seldom the same. Now, if one of your spies is captured, I'll throw dice to decide whether he talks, although you may never know what the outcome is. Your spy might then return and tell you lies. Now, if you look carefully at each of your spies, they each have a special mark. That gives their character, whether they are brave, whether they will try to fool captors, whether they are less trustworthy, and some special features known only to me to help decide the outcome following a dice throw.