‘No – it’s necessary for that, but not sufficient. If I end up disproving Lila’s theory, then I won’t have much hope of working out the shape of anything. All my calculations linking energy to curvature depend on Lila being right.’

Azelio was confused. ‘Why couldn’t you adapt your work to Vittorio’s theory?’

Agata said, ‘If the results agree with Vittorio’s theory then I’ll have no choice but to accept that as a fact – but I’d have no idea how to integrate it into modern physics. Lila’s theory makes gravity consistent with the notion that everything should work the same way when we rotate our picture of it in four-space. If gravity doesn’t respect that, it would be the most shocking discovery since Yalda came down from Mount Peerless.’

‘Then you should hope for that shock,’ Azelio joked. ‘You’d be as famous as Yalda.’

‘And I’d have to throw out half a lifetime’s work and start again.’

‘Isn’t that the price of every scientific revolution?’

‘Lila’s theory is the revolution!’ Agata countered. ‘It’s just been a quieter one than Yalda’s or Carla’s, because it’s been so hard to test. What the revolution will throw out isn’t my work, it’s Vittorio’s – and he didn’t live long enough to know or care that his beautiful ideas weren’t perfect.’

‘I won’t believe that space is curved until I’ve seen it with my own eyes,’ Azelio avowed. He wasn’t usually so invested in any of Agata’s purely theoretical claims, but he seemed to have found this impending empirical affront to his intuition too much to accept without protest.

Agata gestured at the screen. ‘You’ll see something, soon enough.’

‘No, all that will show us is that the light is bent. Which Vittorio’s theory predicts as well.’

Agata buzzed at his stubbornness. ‘Bent by a different amount – and for some colours, in the opposite direction!’

Azelio said, ‘Honestly, don’t you think you’re trying to conclude too much from such slender evidence? Even if the bending is exactly what you predicted, couldn’t there be another explanation for it? Maybe the requirement for gravity to fit in with rotational physics implies certain angles of deflection for the light. But that could come from a tiny modification to Vittorio’s force law, couldn’t it? We’ve always known that gravity bends the paths of moving objects. Why not just refine that notion – instead of leaping to the conclusion that it’s actually bending space?’

Agata didn’t know how to answer him. From the point of view of everyday experience, it probably did sound grandiose to make so much of such a small effect.

She thought for a while. ‘I’ll tell you why I’m going to believe that space is curved, unless I find overwhelming evidence to the contrary.’