‘That’s Florian Horst,’ whispered the curly-headed student. ‘He served in the Army, so I guess the Herr Professor considers him trustworthy.’

‘Oh. I’m Gavriela Wolf.’

‘And my name is Lucas Krause. I’m honoured to meet you, Fräulein.’

Seated, he gave a small bow as they shook hands. Meanwhile the burly man, Horst, was hefting the big wire basket - to him it appeared feather-light - then putting it down and nodding to Professor Möller.

The Van de Graaff groaned and growled as it ran. The metal sphere on top was large, and Gavriela wondered what kind of potential it might reach. Ten thousand volts, a hundred thousand? It was possible to reach five million volts.

With Horst’s assistance, Professor Möller climbed atop the wax slab and steadied himself. Then he nodded, and Horst stepped back.

As the professor’s fingertips touched the metal sphere of the Van de Graaff, everyone - first-years included - raised a great cheer and applauded. Around his head, his long hair drifted upward and spread out in a nimbus, each individual hair repelling the others, for they were similarly charged, as was the whole of Professor Möller’s body. And without the insulation of the wax slab, the potential would connect to earth, causing a fatal current to flow.

‘You may be wondering,’ he said, ‘just how I feel today. Well, I’m—’

Two-thirds of the students roared: ‘—feeling very positive!’

Everyone cheered.

Then Horst was carrying out his true task, raising the cylindrical wire basket, standing on the small wax block, and helping to lower the basket around Professor Möller, encasing him. As he did so, the hairs on the professor’s head drooped, no longer repelling each other, for the free electrons in the wire basket drifted under the electrical force, until all charges were balanced, cancelling out.

Around Gavriela, the applause reached a crescendo, but she could only sit there, blinking with tears. You could read in a book that there could be no electrostatic field inside a conductor, but this was what made it real, brought understanding to life, in a way that demonstrated the courage as well as the perspicacity of science.

She was stunned and honoured to be here in this moment. And it was so different from the stilted atmosphere of the German schools she had attended.

Horst helped Professor Möller to remove the wastebasket Faraday cage - the professor’s hair once more spreading out, forming fine radii - and then to shut down the demonstration, the Van de Graaff generator whining, its drive belt shuddering, as it came to a halt.

Then the professor supplied a surprising addendum. Pointing to the blackboard that showed Coulomb’s equation for electrostatic forces - like gravity, an inverse square law - he held position like an actor on the brink of soliloquy.

‘This is such a simple equation, is it not? You might think of it as a consequence of geometry, since a sphere’s surface area grows with the square of its radius. If we spread a constant amount of stuff across a growing area, its concentration must be diluted by the same factor.’

Then he pointed to a sextet of equations, all partial differentials - the operator symbol looked like Old Norse - relating electric and magnetic fields.

‘And for electrodynamics, we will expect to master Maxwell’s equations, as our older students doubtless have engraved on their memories.’

A few rueful smiles and chuckles came from the rear of the lecture theatre.

‘But you will be pleased to learn, however necessary such mastery might be, there is no such thing as a magnetic field.’

To Gavriela, who had played with magnets aged six and been fascinated ever since, this was news.

‘Or rather,’ continued Professor Möller, ‘we can show that Herr Doktor Einstein’s theory can replicate all magnetic effects as a relativistic correction to Coulomb potential on moving charges. By changing our viewpoint, we can see that it is all electricity, not a mixture of two forces, and that the unitary force is subject to the alterations of spacetime geometry that you may have heard of.’

And the man who had changed everyone’s worldview had been right here, alternating between wondrous daydreams and furious, intent studying of his physics books, always on a quest, heading for the truth that lay beneath the surface of illusion.

‘Let me add that it is perfectly fine for you all to look puzzled. If you have seen distraught expressions upon my colleagues’ faces or my own in recent days, it is because we have been struggling to understand another second-order equation, one derived by Herr Professor Schrödinger, and we do not yet know how to change viewpoint in order to accommodate it.

‘We seek to assimilate what is known, yet the frontiers of science are at the unknown, and that is where we must work, like archaeologists chipping away stone, revealing the knowledge beneath. Good day, ladies and gentlemen.’

There might have been applause, beyond the surf-like waves of sound inside her head; and there might have been movement at the edge of her vision, as the professor and other students left; but she was inside herself, almost paralysed by the combined wonders of what she had seen and the images shining in her mind, blossoming from the professor’s words.

Such a wonderful time to be alive in!

In the evening, she walked the steep, cobbled, twisting alleys of the Altstadt, the old town, enjoying the cool rain that fell. Her room at Frau Pflügers’ house was comfortable enough, and in future she would surely spend most of her time studying there, but for tonight she wanted to explore. Then she found herself descending to open ground leading down to the river, while to her right rose one of the many old churches. No one else appeared to be here.

‘—you shithead!’

The vehement coarseness was unexpected, and so was what happened next: a swirling group of young men, spilling out from behind a stone wall, grappling and striking each other, grunting with effort and hatred. Then the mêlée split into two groups who glared, and finally backed off, with focused stares and wiping of faces, ready for the trouble to begin again.

Gavriela was trembling, too scared to make herself conspicuous by moving. But the young men were retreating now, each group in a different direction, and soon they had disappeared along separate alleys, and were gone.

Had one group worn yarmulkes: black skullcaps clipped to their hair?

But it was the strange twisting of the blackness in shadowed alleyways that—

Optical illusion.

Vision was a physical phenomenon, optical and electrical within the brain. Stress might deform one’s ability to perceive geometry.

Because I was scared.

Surely this was not the peaceful Zürich she had heard about? But now it was quiet, so perhaps trouble visited seldom, and the reputation for law-abiding calm was deserved. This was a cultured city.

So she walked toward the bright lights of Bahnhofstrasse, thinking that among the elegant shops everything would be peaceful. But as she passed a café, three young women, around her own age but expensively dressed, came out onto the cobblestones, laughing.

‘—dance the Charleston as well as Peter, darlings.’

‘Is that the horizontal Charleston you’re referring to?’

‘Elke, sweetheart. What are you implying?’

‘Only that—Oh, hello.’

‘Er,’ said Gavriela. ‘Good evening.’

‘Are you on your own, dear?’

‘Well, I was . . . Um. Yes.’

‘So why don’t you join us for a coffee, or perhaps a cheerful Glühwein?’

Conscious of her purse’s few coins and notes, Gavriela shook her head.

‘I’m sorry, and it’s very kind of you, but I don’t think I can.’

‘Not even if Petra here does the paying? And I’m Inge, and this is Elke.’