Friar Bartolomeo was pleased to see Luna when she knocked on the door of his cell in the monastery. They walked in silence to the library and Luna felt a familiar sense of anticipation and wonder brewing inside her. She was his young student once again. She took his hand as she used to do.

‘Thank you,’ she said.

‘Who am I to refuse entry to the house of our Lord?’

‘The Lord is thy keeper, the Lord is thy shade,’ she recited.

‘Psalm 120; your father’s favourite.’

Luna held her stick firmly as they entered the library. She nodded to a young novice who passed them carrying books.

‘The crypt is too full so we must now divide our collection by those we will move into the other catacombs,’ Friar Bartolomeo explained as they walked down one of the long aisles of shelves. ‘Some of your father’s collection will be moved too. Come, I will show you to a table where you can read whichever texts you choose from those still on the shelves. You will find the volume I know you are most keen to read, the Epitome of Ptolemy’s Almagest, on the table where some of your father’s collection is stacked. It is at the end of the aisle. I must leave you now to attend to church matters, but I shall not be gone long.’

Luna nodded. ‘Thank you.’

She heard the door close behind him as she took in the high ceiling and expanse of shelves that spread in either direction from the small table where he’d seated her. Luna laid out the copy of the Sacrobosco she’d brought and then the Archimedes. She opened The Sand Reckoner first. She decided Archimedes was either a man of unflinching faith or grandest self-belief to undertake such a task as to calculate the number of grains of sand required to fill the universe. Yet he’d done it, and part of the process was estimating the biggest potential size of the universe. She read on with amazement at the enormity of his undertaking. The detailed account of how he’d gone about it was complicated beyond belief and she reviewed the mathematical calculations slowly to try and understand them. He’d used the theory of Aristarchus of Samos, the Pythagorean, in his methodology and this caught Luna’s attention because she didn’t recognise anything of basic astronomy in it. Here was a totally preposterous notion of the universe that said the fixed stars and the Sun remained unmoved and that the Earth revolved around the Sun!