Meanwhile, Richard continued,
"And some objects are so massive that they don't just bend space—they punch straight through it. You can pass through them and travel from one part of space to another. Wizards make use of this wormhole effect all the time for travelling. They have specially enchanted objects called Portkeys."
Grosvenor folded the sheet of paper and pushed his fountain pen straight through it.
"Like that!"
"So Muggles know such a thing is possible?" Hermione asked, dumbfounded. Once again, Richard had made her look at magic from an entirely new perspective.
"Yes!" Grosvenor nodded. "At least in theory. Mathematics and physics have already worked it all out. Scientists call portals wormholes. They're the very place where topology meets astronomy. The really interesting question is: what shape does the universe have far away from wormholes and black holes—that is, in the region where we happen to live right now?"
"And what shape is it?" Hermione asked.
"Imagine our world filled with a grid, like the squares in an exercise book. It doesn't have to be flat—it can curve positively or negatively. That's the very non-Euclidean geometry I mentioned at the beginning."
"All right." Hermione's eyes shone with excitement; she was genuinely fascinated by the structure of the universe. "I'm imagining a page from an exercise book, bent in lots of different places."
"The universe could have any shape at all," Richard continued. "But how can we know for certain?"
"How?"
"There is a way. To find out, you have to look into the most distant reaches of the universe. Three hundred and eighty thousand years after the Big Bang, the universe became transparent to light, and photons scattered in every direction."
Hermione was beginning to lose the thread of the explanation. But caught up in his enthusiasm, Richie failed to notice. Remembering the physics lectures from his previous life, he continued eagerly,
"Through a telescope, we can obtain a sort of light snapshot of the universe. That lets us measure its density. If, using the equation E = mc², we convert all the energy into mass, we get this: if the density is greater than five and a half hydrogen atoms per cubic metre, then the mass of matter will curve space around itself and the universe will close into a sphere. If the density is lower than that, space will be curved like a saddle. But if the density is exactly equal to the critical value, then our universe is flat... and rather boring."
Richie looked up and saw Granger staring into the distance with glazed, unfocused eyes.
"Oi, Hermione." Grosvenor gave her shoulder a gentle shake. "Are you all right?"
"Huh? What?" Granger started, looked around in confusion, then focused on Richard again. "I... I'm fine."
"Did you understand any of that?"
"Yeees..." Hermione replied uncertainly. "Our universe is... oval-shaped?"
"Flat, Hermione! The density of the universe is almost exactly five and a half hydrogen atoms per cubic metre. It's as though someone fine-tuned the universe specifically for us. And not just our universe—the entire multiverse."
"How does that work?" Hermione asked, looking utterly bewildered.
"Our world isn't the only one. Take house-elves and goblins, for example—they're visitors from parallel worlds."
"Right..." Granger murmured, not even attempting to argue.
"Hermione, that's not where the strange part ends. It gets even more complicated from here, so brace yourself. There's only a little bit left."
Hermione closed her eyes and let out a deep sigh. After taking a moment to recover, she said,
"I'm ready. Go on."
"Even if the universe is flat, that doesn't mean it can't loop back on itself like a sheet of paper rolled into a tube, or even close into a torus. Our world could be the same—just in one extra dimension."
"Er..." Hermione said weakly. "I'm completely lost now," she admitted sadly.
"Sorry." Richard gave her an apologetic smile. "I forgot quantum astrophysics might be a bit much for you just yet. I can try explaining it more simply."
"Richie, if you would..."
"The multiverse is like the bubbles in a bubble bath—countless bubbles packed tightly together. Only in the case of reality itself, the foam is made from one and the same bubble. So if we could somehow look beyond the edge of the visible universe, we'd see our own world again—only turned inside out. Makes your head hurt, doesn't it?"
Judging by Hermione's glazed expression once more, her new picture of the universe really had made her brain seize up.
"Er... Richie, it's certainly interesting, but what does any of this have to do with magic and Transfiguration?"
"MAGIC CAN DO ANYTHING!" Grosvenor whispered loudly, his eyes blazing with excitement. "Hermione, magic is the universe's master key. It's like having the system administrator's password to a computer server. If you know how, you can twist the laws of the universe however you like. You could create an archway only one centimetre wide that would take centuries to walk through. Or the opposite—an archway that lets you step in at one end of the universe and emerge a billion light-years away, or even in a parallel universe. With a sufficiently powerful artificial intelligence, you could use the principles of topology to calculate the perfect Transfiguration, turning a stone into a starship—or a starship into a stone. The transformation would last an order of magnitude longer than a conventional one, perhaps even forever. That's a far cry from turning a matchstick into a needle!"
Suddenly, Madam Pince appeared beside their table.
"Shhh!" she hissed sternly, pressing her forefinger to her lips. "This is a library. Keep your voices down!"
"Yes, Madam Pince," Hermione Granger replied at once. "We're sorry. It won't happen again."
Before leaving, the librarian peered at the students over the tops of her spectacles as though they were dangerous criminals she'd just caught dismembering a kitten for some dark ritual.
Richie felt as though he'd had a bucket of ice water dumped over his head. He'd just come up with a truly brilliant idea, realised the sheer grandeur of magic, and glimpsed the key to the universe hidden within it—and then all he got was keep your voices down... Mundane reality had barged back in far too abruptly, bringing everything back down to earth.
(End of Chapter)
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