"Hmmm," said Lloyd. "But what about particles that we can't shield against? What about neutrinos?"

Theo frowned. "For them, it shouldn't make any difference if we're facing the sun or not." Only one out of every two hundred million neutrinos passing through the Earth actually hits anything; the rest just come on through the other side.

Lloyd pursed his lips, thinking. "Still, maybe the neutrino count was particularly high the day we did it the first time." Something tickled his mind; something Gaston Beranger had said, when he was enumerating all the other things that had been happening at 17h00 on April 21. "Beranger told me the Sudbury Neutrino Observatory picked up a burst just before we ran our experiment."

"I know someone at SNO," said Theo. "Wendy Small. We were in grad school togethe r." Opened in 1998, the Sudbury Neutrino Observatory, located beneath two kilometers of Precambrian rock, was the world's most sensitive neutrino detector.

Lloyd gestured at the phone. Theo walked over to it. "Do you know the area code?"

"For Sudbury? It's probably 705; that's the one for most of northern Ontario."

Theo dialed a number, spoke to an operator, hung up, then dialed again. "Hello," he said, in English. "Wendy Small, please." A pause. "Wendy, it's Theo Procopides. What? Oh, funny. Funny woman." Theo covered the mouthpiece and said to Lloyd, "She said, 'I thought you were dead.' " Lloyd made a show of suppressing a grin. "Wendy, I'm calling from CERN, and I've got someone else with me: Lloyd Simcoe. You mind if I put you on the speaker phone?"

"The Lloyd Simcoe?" said Wendy's voice, from the speaker. "Pleased to meet you."

"Hello," said Lloyd, weakly.

"Look," said Theo, "as you doubtless know, we tried to reproduce the time-displacement phenomenon yesterday, and it didn't work."

"So I noticed," said Wendy. "You know, in my original vision, I was watching TV — except it was three-dimensional. It was the climax of some detective show. I've been dying to find out who did it."

Me, too, thought Theo, but what he said was, "Sorry we weren't able to help."

"I understand," said Lloyd, "that the Sudbury Neutrino Observatory picked up an influx of neutrinos just before we did our original experiment on April 21. Were those neutrinos due to sunspots?"

"No, the sun was quiet that day; what we detected was an extrasolar burst."

"Extrasolar? You mean from outside the solar system?"

"That's right."

"What was the source?"

"You remember Supernova 1987A?" asked Wendy.

Theo shook his head.

Lloyd, grinning, said, "That was the sound of Theo shaking his head."

"I could hear the rattling," said Wendy. "Well, look: in 1987, the biggest supernova in three hundred and eighty-three years was detected. A type-B3 blue supergiant star called Sanduleak—69 202 blew up in the Large Magellanic Cloud."

"The Large Magellanic Cloud!" said Lloyd. "That's a hell of a long way away."

"A hundred and sixty-six thousand light-years, to be precise," said Wendy's voice. "Meaning, of course, that Sanduleak really blew up back in the Pleistocene, but we didn't see the explosion until twenty-two years ago. But neutrinos travel unimpeded almost forever. And, during the explosion in 1987, we detected a burst of neutrinos that lasted about ten seconds."

"Okay," said Lloyd.

"And," continued Wendy, "Sanduleak was a very strange star; you normally expect a red supergiant, not a blue one, to go supernova. Regardless, though, after exploding as a supernova, what normally happens is that the remnants of the star collapse either into a neutron star or a black hole. Well, if Sanduleak had collapsed into a black hole, we never should have detected the neutrinos; they shouldn't have been able to escape. But at twenty solar masses, Sanduleak was, we thought, too small to form a black hole, at least according to the then-accepted theory."

"Uh-huh," said Lloyd.

"Well," said Wendy, "back in 1993, Hans Bethe and Gerry Brown came up with a theory involving kaon condensates that would allow a smaller-massed star to collapse into a black hole; kaons don't obey Pauli's exclusion principle." The exclusion principle said that two particles of a given type could not simultaneously occupy the same energy state.

"For a star to collapse into a neutron star," continued Wendy, "all the electrons must combine with protons to form neutrons, but since electrons do adhere to the exclusion principle, as you try to push them together they instead just keep occupying higher and higher energy levels, providing resistance to the continued collapse — that's part of the reason why you need to start with a sufficiently massive star to make a black hole. But if the electrons were converted to kaons, they could all occupy the lowest energy level, putting up much less resistance, and making the collapse of a smaller star into a black hole theoretically possible. Well, Gerry and Hans said, look, suppose that's what happened at Sanduleak — suppose its electrons became kaons. Then it could have collapsed into a black hole. And how long would it take for the conversion of electrons into kaons? They mapped it out at ten seconds — meaning that neutrinos could escape for the first ten seconds of the supernova event but, after that, they'd be swallowed up by the newly formed black hole. And, of course, ten seconds is how long the neutrino burst lasted back in 1987."

"Fascinating," said Lloyd. "But what's this got to do with the burst that happened when we were running our experiment the first time?"

"Well, the object that forms out of a kaon condensate isn't really a black hole," said Wendy's voice. "Rather, it's an inherently unstable parasingularity. We call them 'brown holes' now, after Gerry Brown. It in fact should rebound at some point, with the kaons spontaneously reconverting to electrons. When that happens, the Pauli exclusion principle should kick in, causing a massive pressure against degeneracy, forcing the whole thing to almost instantaneously expand again. At that point, neutrinos should again be able to escape — at least until the process reverses, and the electrons turn back into kaons again. Sanduleak was due to rebound at some point, and, as it happens, fifty-three seconds before your original time-displacement event, our neutrino detector registered a burst coming from Sanduleak; of course, the detector — or its recording equipment — stopped working as soon as the time-displacement began, so I don't know how long the second burst lasted, but in theory it should have lasted longer than the first — maybe as long as two or three minutes." Her voice grew wistful. "In fact, I originally thought that the Sanduleak rebound burst was what caused the time displacement in the first place. I was all ready to book a ticket to Stockholm when you guys stepped forward and said it was your collider that did it."

"Well, maybe it was the burst," said Lloyd. "Maybe that's why we weren't able to replicate the effect."

"No, no," said Wendy, "it wasn't the rebound burst, at least not on its own; remember, the burst began fifty-three seconds before the time displacement, and the displacement coincided precisely with the start of the your collisions. Still, maybe the coincidence of the burst continuing to impact the Earth at the same time you were doing your experiment caused whatever bizarre conditions created the time displacement. And without such a burst when you tried to replicate your experiment, nothing happened."

"So," said Lloyd, "we basically created conditions here on Earth that hadn't existed since a fraction of a second after the Big Bang, and simultaneously we were hit by a whack of neutrinos spewing out of a rebounding brown hole."

"That's about the size of it," said Wendy's voice. "As you can imagine, the chances of that ever happening are incredibly remote — which is probably just as well."