Finally, I succeeded in diverting his attention from the black hole on the screen, but there was a far-gone look in his eyes that I found eerily disconcerting. A chill went down my spine.
"As I said, two entangled quantum particles have states that are linked. The particles have the same origin, and no matter how distant if you affect the state of one, it's spin, color, strange, et cetera, then the other changes in response, instantaneously. That's 'spooky action-at-a-distance.' Faster than light travel."
I didn't say anything, didn't wish to interrupt him, but glanced at the monitor, at the spectacular emptiness and the doomed star. I felt cold suddenly as if there were a wind picking up. In my mind's eye, I envisioned the corridors of the TARDIS, disembodied perspective floating down them. They were seemingly endless. I could see the paneling, feel the textures, and then…around a curve the contours seemed to change, the paneling different, blacker, hoses and wires emerging from the walls, not exactly Timelord technology…
"Heisenberg's principle. You've heard of it, I suppose?"
I nodded. "That's the uncertainty principle, right?"
"Very good. Do you understand its implications?"
"Yes," I said with some confidence.
"Then explain it to me." He had returned to the console again and began setting coordinates.
"Well," I began, "from what I can recall, according to quantum mechanics particles no longer act like particles when you get down to the subatomic level. They act like waves. It's the wave-particle duality. That was one of the genius ideas of the early architects of quantum mechanics. The paradox of the atomic world can be resolved by saying that sometimes a particle acts like a particle, and sometimes it acts like a wave."
"I'm impressed," he said, not looking up at me. "Go on."
"So as a consequence of this uncertainty when we observe matter at the subatomic level, the particles that make it up act more like waves. That means that the actual position of a particle may be spread out over a given area. In other words, you can't know both the particle's location and its velocity simultaneously."
"Technically, it's momentum, ρ."
"We're under attack by Angels. Why are you quizzing me on this right now?"
"Just keep talking," he said.
"Alright. You can't know the location and momentum of a subatomic particle simultaneously, and neither can you know the energy and time simultaneously. Precise measurement of either position or energy results in uncertainty in the measurement in the momentum or time, respectively."
"And that's not just a limitation on instruments," he added. "It's not merely the idea that scientists cannot observe a physical system without affecting it; the uncertainty is a physical limitation on our ability to observe the universe at its fundamental levels, a law firmly governed by Planck's constant."
I had forgotten that aspect of it. "Yes, I guess you're right." He always had to be right.
"Normally this effect is limited to the quantum world," he began. "Subatomic particles can have a fuzzy location if we know their momentum—velocity, speed—but that does not happen in the classical world, even though, hypothetically speaking, everything—you, me, that galaxy out there—can also function as a wave and a particle. We also have some degree of uncertainty associated with us as humanoids, though it is vanishingly small.
"So that's why you brought me here. For a lesson in quantum mechanics?"
"You think that I've summoned you here just to listen," he said, "but you're wrong. You've got another thing coming, and I'm sorry. I'm so sorry to have to tell you this."
I felt the hair stand up on the back of my neck.
"There's something I never mentioned before because I didn't want to scare my companions. Remember I said the Angels immediately turn to stone when observed and this is called quantum-lock? That is because they are quantum creatures," he said. "When you see them, when they are observed, we know their position but we cannot know their momentum, their movements. Similarly, we know their energetic state—cold stone—but we can't pin them down precisely in time. That's the quantum-lock. They are in-between creatures that live in the no-man's land between the classical, mechanical world and the world of subatomic particles. They are evidence of quantum behavior bleeding into the world of the everyday.
"This is how they 'kill' you: they send you back in time, feeding off you time-energy, that is, making your lifespan more uncertain, they thereby absorb energy and reconstitute their own form. They literally suck the certainty out of you! Do you understand? It's not that they send you back in time exactly. You still exist in your original time. It's just that they consume your energy, thereby obfuscating the probability wave of your time dimension. Suddenly, you're more likely to exist in another epoch, and the longer you've been dead the bigger the…snack.
"Angels are by nature quantum creatures," he continued, "but this also means that they exist at the boundary between moments in time. They are creatures of discontinuity—they emerge from the spaces between moments in time that cannot be observed. That's their real origin. That means they cannot only send you back in time, but also into oblivion, into the discontinuity between the measurements of time itself.
"And I'm so sorry to have to tell you this, but the Angels have the phone box…again! And if we don't stop them, they will swallow the universe into a discontinuity."
"By discontinuity do you mean the time crack on Alfava Metraxis?"
"No. A discontinuity in time is different. It is…sheer nothingness, pure Void. You can imagine spaces in between two points, correct?"
"I suppose so," I said.
"And as you telescope down there is always a smaller distance between two points. Well, can you imagine the same thing but in time on a clock face, always a smaller time interval. But there is a limit on this measurement-and that's called the Planck length. That's our universal limit on the measurement of space-time, where quantum effects take over and everything gets…all foamy."
"That's the Void," I said.
"That's where the Angels come from. And with the TARDIS, that is the fate of the universe—to fall into the cracks in the fabric of space and time itself. So now we're going there," and he pointed to a point on the blackness on the screen."
"To the Angels' home world?"
"An Angel hive on a dead planet orbiting the largest black hole in the universe..."