‘One of my father’s that he planned on leaving to the preacher’s bonfire, so I saved it. I brought it with me today thinking I might find something of interest within its covers.’ She tried to sound nonchalant though her voice quivered as she spoke. Why had she brought a book of blasphemy to a monastery? She hoped the friar would move on to consider the Sacrobosco and pushed it towards him but he’d already taken up The Sand Reckoner and opened it.

‘I know this book,’ he said. ‘I’m surprised to see it in your hands. I did not realise you would go back to the early astronomers and mathematicians; your education in the subject will take years if this is your approach.’

Luna shook her head. ‘I was drawn to this book because of Papa. It felt different to the others in his collection, more personal to him, so I thought to keep it. I am sorry if it was wrong.’

‘I did not say it was wrong; all reading is knowledge. Archimedes was a brilliant mathematician, but constrained by his times.’

‘What do you mean?’

‘You must remember, back then, learned men were ignorant of much we now understand; even the very great amongst us make mistakes. Archimedes used a theory of the Pythagorean Aristarchus’s making, but nothing survives in Aristarchus’s own hand, so we cannot be sure of the veracity of what is written in The Sand Reckoner.’

‘Yes.’ Luna knew this. She hesitated. ‘Still, he suggests something I find hard to even voice, for it sounds so wrong, but it is intriguing and I trust you will not judge me, so I will raise it with you.’

He crossed his arms in a familiar manner and nodded. ‘Continue,’ he murmured. Then he pressed his hands to his chin. Luna recognised this contemplative stance and it eased her nerves enough to keep speaking.

‘That the Earth revolves around the Sun. What do you make of this?’

The friar laughed in such a way that Luna found herself laughing too, else she be counted a fool.

‘This book was written a long time ago,’ he said simply.

‘Indeed, and yet the same author, in the same book, also used the Pythagorean’s concept to calculate the width of the universe using the diameter of the orbit of the Earth around the Sun. That was the basis of working out how many grains of sand would fill the universe, and we don’t dispute Archimedes on this, do we?’

‘Dear Lord, you’ve been sat here too long with only books for company. Do you fall and tumble about as you walk?’

Luna frowned at this and the friar coughed with embarrassment. ‘I beg your forgiveness, Luna, for my unfortunate analogy, but common sense tells us that if the Earth was spinning right now, then surely we would feel it.’ He shrugged, but Luna found this frustrating.