Aristarchus then argued that the Moon travelled around the Earth once a month, and both travelled around the sun, taking a year to make the journey. The sun was considerably further away than the Moon. To measure the relative distances, he waited until half-moon, at which time the angle Sun-Moon-Earth must be a right angle. By measuring the angle between the moon and the sun, he could get the ratio. The angle was 87 degrees, so from Pythagoras' theorem, the sun was twenty times further away from the Earth than the moon.
Gaius was at first stunned, then he snorted. The angle 87 degrees was so close to a right angle that the Greek must have got it all wrong, then suddenly he stopped to think. If it were 89 degrees, say, it would be much further away. Even if he were correct, that meant it had to be so much larger than the moon. It looked to be the same size as the moon in a solar eclipse, or so they said, but if it was twenty times further away, it had to be twenty times larger!
There seemed to be something wrong with all that. They were obviously the same distance away since they both went around the Earth in roughly the same time, but. . No! The argument was the Earth was spinning, and the Moon went around the Earth in a month. That was just so confusing! Except, deep down, it had a certain logic to it. Then again, if the reason why there was a half phase was because the sunlight struck the Moon side on, which is what Aristarchus said, then the Moon would be a sphere too, just like the Earth. With a start, he wondered whether it was in any way like the Earth.
And if the Moon was as big as the Earth, then the sun had to be immense! And if. . But this was a waste of time. Too many ifs and buts, and anyway, who cared? Rome was built on stones and the sword.
Chapter 4
Gaius was almost late for the family meeting with the Princeps. He had dressed formally in his toga and was about to proceed towards the meeting when he received a formally written note, under an impressive looking seaclass="underline" "Dress in tunic, not toga. Ti. Clavd. Drv." So he had to dress again. His family was staring around, clearly agitated and clearly looking for him, when he entered. He was so conscious of the welts on his legs, and the expression on his father's face showed that they were rather obvious.
But this was of little concern to Gaius. He looked up at the rostrum to see three people staring at him with three quite different expressions. On the right sat the stutterer, who gave him a nod and a wink of encouragement, and who seemed to be remarkably pleased with himself. On the left was Gaius Caesar, who had the sour look of someone forced to be somewhere where only bad could come to him, and who was anything but pleased at the prospect of what was to come. But on the largest and central chair, underneath the great eagle, was the old man from the library. Only Tiberius would sit in that chair! Now he knew why Gaius Caesar had been afraid; he had called Tiberius a snivelling idiot, in his hearing. But this man looked nothing like the image on the coins. He looked old and weary! Then suddenly the true importance of his position struck him. He had had the rather dubious pleasure of discussing Tiberius' German campaign with Tiberius himself. He almost froze but the words of Libo came back to him. Act like a soldier, show no fear. Gaius quickly made a formal bow, and stepped towards his family.
"So," Tiberius said in a droll voice, "this annoying stub of the Claudian gens has finally assembled." His eyes scanned across them, and muttered, "What a miserable looking lot!"
Gaius remembered the advice Libo had given him. No, he was not going to look miserable. He stood, his head held high.
"And you, I suppose," Tiberius stared at the Grammaticus, "are the one who got Little Boots all riled up?" The Grammaticus was studying the floor, Gaius noted. "And I presume you're also responsible for that boy's legs?" Silence. "Well?" Tiberius snarled in a quiet voice.
"I, I, er. ."
"Presumably through some noble activity such as using the practice swords?" Tiberius added in a tone as if he could not care less.
"Er, yes, Princeps," the Grammaticus finally muttered.
"I thought as much," Tiberius remarked. "You!" he said, now pointing towards Gaius, "You read about the campaign?"
"Yes, Princeps."
"So, pretend you're the commander. You get to the river, what do you do?"
"Set up camp and fortify," Gaius replied quickly.
"Then?"
"I would cut down forest around the camp, and within the fortifications, build rafts," Gaius said simply.
"You would float downstream?" Tiberius asked, in some surprise. "You would do that rather than come over the Alps?"
"Yes, although of course there may be factors I have not considered."
"And why not the Alps?"
"The paths narrow," Gaius said. "That was known at the time. Too much risk of ambush. With rafts, the river would carry us at a speed the Germans could never match."
"You realize I took the Alps?" Tiberius asked.
"Yes Princeps."
"So you think I was wrong?"
"No, Princeps."
"No? How come?"
"We know your method worked," Gaius remarked, "whereas we have no idea what would come from a river-borne escape. If it works, it can't be wrong."
"But you still say, the river?"
"When the decision has to be made, I wouldn't know whether the alpine route would work either," Gaius said. Murmurs arose from some of those present in the background. A boy questioning Tiberius? Gaius' father was appalled.
"There was a lot of discussion at the time," Tiberius noted dryly, his gaze passing over those in the background and immediately silencing them. "The issue was by no means clear-cut." He nodded, and turned his gaze back to the boy. "So, at least we've established you're no sycophant. Are you a liar?"
"No, Princeps!" Gaius replied quietly but firmly.
"Someone is," Tiberius snorted. "You claim you've had sword training by this man Libo?"
"Yes, Princeps."
"Then show me. Centurion!" Tiberius pointed to one of the Praetorian guards, who stepped forward, carrying two of the lead-weighted wooden practice swords and two shields. He handed a sword and shield to the boy, then stepped back. After Gaius had secured the shield, Tiberius nodded. Suddenly the Centurion swung his arm back, to smash the sword down on Gaius' head. In an instant, Gaius stepped forward, raised the shield, and thrust, throwing everything his shoulders and hips could give. The Centurion's blow sent his shield falling backwards as the point of his sword struck the leather armour, and the centurion swore. Gaius flinched, waiting for retribution.
"Well?" Tiberius asked.
"That would kill," the Centurion nodded.
"Then, young Claudius, no need to flinch," Tiberius snorted. "A Praetorian gains no credibility by refusing to die in practice. Indeed," he added coldly, "we might do it for real, to show him that he can't. Well, don't just stand there! Get on with it!"
Gaius stepped back and readjusted his shield. The Centurion advanced, swung out wide, and struck. In a flash, Gaius thrust his shield to block the blow, and thrust again with everything he had, the point catching the Centurion under the rib cage, doubling him up. The Centurion stepped back, then suddenly Gaius realized what was happening. The Centurion was going through a practice sequence similar to what Libo had shown. He knew what was coming next. Then he saw the Centurion's eyes; a slight show of cunning. As he advanced, Gaius started what he was expected to do, namely thrust straight forward with the shield, but then just as impact should have occurred, he pulled back, and as the Centurion pushed on nothing and slightly lost balance in going forward too far, Gaius slammed the shield across and thrust again, the point going slightly upwards and into the ribs.