"What do you mean 'eliminate'?"
"Eratosthenes eliminated the theory that earth was totally flat, excepting montains. Egypt is as flat ground as you get in the world, but between Assuan and Alexandria there is clearly something bulging, so that up is not the same direction in both places. He proved it."
"Well if the sun at noon when it is high shines straight down in Assuan and slightly northwards in Alexandria, that means the direction of sunbeams is perpendicular in one place and not in another. And if their direction is really the same, up must be slightly north of the sun in Alexandria, but not in Assuan. Assuming it is midsummer, of course."
"If the sunbeams are really coming exactly the same direction, but how do we know that?"
"Back then it was an assumption, it has been validated since. Remember how we used to do surveying out on that hike?"
"You survey distance to moon by taking angles from two places on earth at same time. With modern watches that is no problem. Then you know the moon might shine on different places with different angles. Now, if you measure the angle of sunlight on the moon, which is what you do by measuring the phases, you can survey distance to sun. Since it shines on the moon at a slightly different angle than on earth. Very slightly. Actually that may have been how Eratosthenes knew sun was too far away to shine different angles on Alexandria and Assuan."
"But I thought people thought the earth was flat up to the time of Columbus?"
"If you mean people like Spanish and Nordic sailors, sure, some of them or even most of them might have believed that. If you mean scientists, no they did not."
"So Columbus proved nothing that wasn't already known?"
"Columbus and Vasco da Gama proved that the non-flatness of earth amounts to a complete globe. Noone had seriously suggested it might be a half-globe - at least pa knew noone who had - but Columbus and Vasco da Gama gave proof it was not.
"They also disproved - along with James Cook - Saint Augustine's theory that there are no people on the opposite side of the earth."
"How so? I mean they discovered Red and Honest Injuns and Aboriginees with their didgeridoos and boomerangs, but why was Saint Augustine sure there were none?"
"He was maybe the one Church Father back in those times to care about the question, but his take depends on the fact he had never been in the Atlantic. You know the Gulf Stream?"
"Sure, it keeps us warm in winter and starts from the Gulf of Mexico."
"That's it. And where is water floating the other way, back to the Gulf Stream?"
"Wasn't that the stream from the Azores, the one that Columbus used?"
"Exactly. Now, he knew of neither of these streams, so he thought it must be either physically possible to sail and sail back like that, to get West and back East to where you came from or physically impossible to get West across the Ocean at all."
"He didn't count on parting from Azores and getting back to Ireland? Surely scientists have been taught to make no such blunders?"
"He was from the Mediterranean, not the Atlantic. Great if you want good food and people talking nice, but less great for some scientific observations. Do you think Galileo was a real scientist?"
"He was, like St Augustine, from the Mediterranean. One of his judges, can't recall which process, was from Portugal. He knew, from observation, that Galileo was wrong on tides."
"But the modern theory of tides is a heliocentric theory, right?"
"If you like, but it is not Galileo's. It was in fact very recently that Sir George Darwin (grandson of 'Mr-Man-Descends-From-Apes' Charles Darwin himself) who founded the modern theory of tides."
"Anyway: as Galileo was wrong about tides, St Augustine did not count on parting from Azores and getting back to Ireland?"
"No. In this case, the lacuna ..." she stopped. "Can I have some more tea please?"
When she got it, and her throat was less parched, she continued:
"In his case the lacuna in his enumeration of possibilities was discovered through making the voyages. But he also gave a real alternative, something to disprove, which was not disproven until then. I mean the non-existance of antipodes, of people walking with feet against ours."
"Which was exchanged for the very clear existance of Injuns, Maoris, Aboriginees, and so on. - So you mean, one cannot eliminate a possibility by just ignoring it?"
"Exactly: no one cannot do so properly."
"Not even by discovering the opposite?"
"How can you discover the opposite of a non-real possibility and not eliminate it?"
"Getting back to Ramandu and so, if people thought that Mars was a god because there are not just the movements around us along with the rest of the sky but also retrograde motions and getting through the zodiak, and now we know it is because Mars and Earth turn around the Sun at a different pace, and when Earth goes faster on same side as Mars, it looks like Mars is going backwards."
"How is that a discovery that Mars is neither a god nor any other type of guy?"
"Well, if we now know it is because of gravitation and momentum."
"Well, we would know it is because of that, if we had properly eliminated the theory that Mars is being moved around by some guy."
"But we have seen Mars in telescopes, it is a ball with channels on it, not a guy with a face."
"Even if not, why must all and every kind of people or beings with a conscience have a face?"
"Well, without eyes it would be blind, without mouth and ears it wouldn't communicate with others of its kind..."
"First of all, it might not need either of it to guide Mars, as the rock we see. It might be feeling its way around some gravitational field around the Sun. Of course, Mars as seen by us need not be the actual guy either."
"But who could be strong enough to push all of planet Mars around its orbit, we know how big it is and how heavy, right?"
"It is assumed we know how heavy it is, because if Mars is moved only by mechanic causes, if these are its previous momentum being calculable from speed and mass, and its gravaitation towards the Sun, where the calculation is from distance and from both Sun's mass and its own, then by knowing distance and orbit we can calculate its mass."
"You mean, how heavy it is?"
"But the distance, the orbit, the speed are all known and the calculations have been made."
"They have been made by scientists who assumed they knew the precisely two only reasons for its movements, both of which involve masses."
"But scientists aren't supposed to assume, are they? They are supposed to know and prove before they talk as if they knew, right?"
"And how often do you think people failed to do what they were supposed to? I mean the driver of the locomotive in that train was very much doing nearly what he was supposed to. If he had also slowed down a bit earlier, your family and friends like Jill and Polly and Professor Kirke would still be alive."
"OK, that was a slip of his mind."
"Well, as said, scientists have for centuries not been paying attention to the possibility that the movements of stars and planets may be a form of conscious art. That also may be a slip of mind, though in this case it has lasted centuries."
"So you say you believe Lucy is right?"
"I may come to believe that about stars later on, right now I am only trying to not eliminate the possibility prematurely."