The goose quill her father used lay to the left and beside it were clean parchment sheets. Luna took up the quill and rolled it in her fingers, testing its weight. The feather swivelled. She unrolled a precious parchment. The sheet was roughly finished, unlike the calfskin vellum of the books her father cherished, but she did not mind. She moved the pot of ink closer and positioned the blotting rag beside it and sat back, stilled by the weight of what she was about to do. Then, just as once before when she’d sat for the painter, an overwhelming sense of clarity came across her and she breathed through the rise and fall of her chest and felt the current of blood through her veins as her mind centred on her task.

She smoothed out the page and whispered a prayer. Closing her eyes, she thought about the power of words and the art of writing; her scholarship was indeed a precious gift. She drew the curve of a y slowly down the page. Her hand was unsteady at first. How she would have loved to watch Isotta Nogarola write. She imagined the silence of her concentration as she put to parchment her arguments in those beautiful words, like choosing a very large head of raw wool and condensing it to thread. Luna wrote slowly and carefully.

You, who wish to study great and wonderful things, who wonder about the movement of the stars, must read the theory of Archimedes, the Greek mathematician of great renown. Knowing the ideas in his work, The Sand Reckoner, will open the door to all of astronomy. We must follow in the footsteps of the master mathematicians and hold fast to their observations, bequeathed to us like an inheritance.

Archimedes set out to determine an upper bound for the number of grains of sand that fit into the Universe. In order to do this, he had to estimate the size of the Universe and for this he used the hypotheses of the Pythagorean, Aristarchus of Samos.

Aristarchus of Samos proffered an alternate Sun-centred model of the Universe, namely that the fixed stars and the Sun remain unmoved and that the Earth revolves about the Sun on the circumference of a circle, the Sun lying in the middle of the orbit.