Velut Luna
Sibilla Cumana
Amica 28
'Instead of standing here reading this nonsense written by actors pretending to be philosophers, come on, let's go to the library, we have to solve a problem that’s close to my heart, and your story - a few days ago I was again faced with an important thing to consider, I mean the fact that, as you tell me, at times the sun remains above the horizon for many days, and at others it never rises at all.'
'Yes Eulalia, excuse me for reading that nonsense, but you know I'm curious, I never dreamed I was doing something wrong.'
'You haven’t done anything wrong, I did not say you had, but curiosity should be addressed to important matters, not nonsense. I appreciate your curious mind, this shows your intelligence. Now light a lamp and pull the curtains over so that no light does comes in from outside.'
'But why do we have to be in the dark and lighting the lamp when it's sunny outside?'
'We need it for our experiment, the lamp – put it in the middle of the round table – it represents the Sun, and this ball of clay is the Earth. As you can see, this ball is pierced with a hole like a bead for a necklace. Now, make a triangle with this piece of copper wire, the its sides no more than a finger long. The part that exceeds the length of the perimeter we’ll bend upwards. On the ball we’ll draw certain signs, points, one here, right in the middle of the distance between the holes, another halfway between that point and the hole, a third between those two points, and one more here, almost touching the hole.'
'What are those points?'
'The world is a sphere, as was shown by Eratosthenes, who calculated its radius. The mid-point is a very far south from the city of Thebes in Egypt; Pompeii is the second, the third is the town of Sirene near Thebes, where the great temple stands, and the last one we marked is the place where I think you lived.'
'But why did you mark these places and not anywhere else?'
'There's a reason: when the sun is furthest above the horizon here in the city of Sirene, south of Thebes, it is directly overhead, and so Eratosthenes was able to see the sun reflected in the bottom of a deep well, and the shadow of an object hanging on a rope down at the bottom of it, while in Alexandria his assistants measured the depth at which the shadow of an object fell at a specific distance from the top, and from this he was able to calculate the radius of the world. In Pompeii, the sun does not rise above a certain altitude, and that determined the point closest to the sundial obelisk that we had built outside here. Our marks on this little ball would be big as the island of Sicily, but for our experiment we don’t need great precision.'
'What do we want it to show us?'
'For now we do not want to prove anything, we just want to understand some very important things. Experiments are used to prepare for reasoning, defining hypotheses. Then you have to prove that one hypothesis is true and discard the others, and when we’ve done that we can speak of a theory.'
'It all seems very complicated.'
'Aristarchus of Samos said that the Sun was the center of the universe and the Earth and the planets revolve around it, while almost all other philosophers do not accept this statement but believe that the Earth is stationary and everything revolves around it, but too many things remain unexplained. Now we, in our experiment, will simulate the idea of Aristarchus, and we will evaluate whether it provides good answers to the many questions that arise from the apparent movement of the sun, the planets and the stars. '
'And all this with a ball of clay and a lamp on the round table in the library? And what does this experiment have to do with the fact that the sun doesn’t set or doesn’t rise?'
'You've just got to help me, don’t pretend you can explain anything. You just know to make prophecies as a Sibyl, I think you could make a good living here in Pompeii, you’d soon become as rich as Lucius! Or rather, if Lucius put you in a booth and you did prophecies, since you're his slave, he’d earn more from you than he makes from all of his brothels full of prostitutes!'
'Instead of standing here reading this nonsense written by actors pretending to be philosophers, come on, let's go to the library, we have to solve a problem that’s close to my heart, and your story - a few days ago I was again faced with an important thing to consider, I mean the fact that, as you tell me, at times the sun remains above the horizon for many days, and at others it never rises at all.'
'Yes Eulalia, excuse me for reading that nonsense, but you know I'm curious, I never dreamed I was doing something wrong.'
'You haven’t done anything wrong, I did not say you had, but curiosity should be addressed to important matters, not nonsense. I appreciate your curious mind, this shows your intelligence. Now light a lamp and pull the curtains over so that no light does comes in from outside.'
'But why do we have to be in the dark and lighting the lamp when it's sunny outside?'
'We need it for our experiment, the lamp – put it in the middle of the round table – it represents the Sun, and this ball of clay is the Earth. As you can see, this ball is pierced with a hole like a bead for a necklace. Now, make a triangle with this piece of copper wire, the its sides no more than a finger long. The part that exceeds the length of the perimeter we’ll bend upwards. On the ball we’ll draw certain signs, points, one here, right in the middle of the distance between the holes, another halfway between that point and the hole, a third between those two points, and one more here, almost touching the hole.'
'What are those points?'
'The world is a sphere, as was shown by Eratosthenes, who calculated its radius. The mid-point is a very far south from the city of Thebes in Egypt; Pompeii is the second, the third is the town of Sirene near Thebes, where the great temple stands, and the last one we marked is the place where I think you lived.'
'But why did you mark these places and not anywhere else?'
'There's a reason: when the sun is furthest above the horizon here in the city of Sirene, south of Thebes, it is directly overhead, and so Eratosthenes was able to see the sun reflected in the bottom of a deep well, and the shadow of an object hanging on a rope down at the bottom of it, while in Alexandria his assistants measured the depth at which the shadow of an object fell at a specific distance from the top, and from this he was able to calculate the radius of the world. In Pompeii, the sun does not rise above a certain altitude, and that determined the point closest to the sundial obelisk that we had built outside here. Our marks on this little ball would be big as the island of Sicily, but for our experiment we don’t need great precision.'
'What do we want it to show us?'
'For now we do not want to prove anything, we just want to understand some very important things. Experiments are used to prepare for reasoning, defining hypotheses. Then you have to prove that one hypothesis is true and discard the others, and when we’ve done that we can speak of a theory.'
'It all seems very complicated.'
'Aristarchus of Samos said that the Sun was the center of the universe and the Earth and the planets revolve around it, while almost all other philosophers do not accept this statement but believe that the Earth is stationary and everything revolves around it, but too many things remain unexplained. Now we, in our experiment, will simulate the idea of Aristarchus, and we will evaluate whether it provides good answers to the many questions that arise from the apparent movement of the sun, the planets and the stars. '
'And all this with a ball of clay and a lamp on the round table in the library? And what does this experiment have to do with the fact that the sun doesn’t set or doesn’t rise?'
'You've just got to help me, don’t pretend you can explain anything. You just know to make prophecies as a Sibyl, I think you could make a good living here in Pompeii, you’d soon become as rich as Lucius! Or rather, if Lucius put you in a booth and you did prophecies, since you're his slave, he’d earn more from you than he makes from all of his brothels full of prostitutes!'
