Page 18 of Under Story

“There are three types of neutrinos,” the man explains. “All are left-handed—you can think of them as spinning to the left—and though particle physics predicts that they should have right-handed partners, as other elementary particles do, such partners have never been discovered. The reason for this asymmetry remains a mystery.”

“I thought you said this was going to be interesting,” Louis whines. Nita swats him before putting her hand back in the pocket of Sam’s sweatshirt.

“Most neutrino detectors are built deep inside the earth to drown out the noise of other particles: in mines, in tunnels, and—as at IceCube—in ice.” The woman nods at the IceCube scientists, who stiffly return the gesture. “ANITA is different: an instrument, suspended by a balloon, that flies over the Southern Ocean. Our detector was designed to search for ultra-high-energy neutrinos. It measures the Askaryan effect, radio pulses emitted when these particles collide with ice.”

She looks at her partner, who nods a fraction of an inch, as if to encourage her to continue.

“Until now, neutrinos have only been detected flying toward the planet, from outer space. But two of our flights detected upward energy showers with angles so steep that we’ve concluded they came from one of two sources,” she says. “The first possibility is that they originated from the earth itself—that they flew out of the planet, toward the sky.”

Uneasy chatter fills the galley. A man sitting near the IceCube table calls, “And you say these were high-energy neutrinos?”

“That’s right. Low-energy neutrinos pass through the planet all the time, but the Standard Model tells us that high-energy particles shouldn’t be able to travel more than a few hundred miles through solid matter.”

“I’d like to see how they determined those angles,” someone says, from deep within the recesses of a fur-lined parka.

“IceCube has never reported upgoing showers,” declares someone else.

“Exactly,” says the male physicist, stepping forward. “IceCube is situated thousands of meters belowground. The fact that they haven’t had a similar detection suggests our second hypothesis is more accurate: that the particles came from somewhere near the surface of the earth—somewhere like the anomaly.”

The conversation in the galley swells. Laurel catches fragments:

“There’s absolutely no way…”

“Would upend the Standard Model…”

“How do you explain the color?” asks a dogged-looking woman in the front row. “Neutrinos don’t interact with light.”

“No,” says the man, “but they do interact with atmospheric gases. The pink color could come from the excitement of oxygen molecules, the blue-green from oxygen and nitrogen.”

“What does this mean?” asks somebody else.

“We aren’t sure yet,” the female physicist says. “We’ve scheduled additional flights; we’re combing through a decade’s worth of data. What we know so far is that these signals can’t have come from any of the three neutrinos in the Standard Model.”

A black slide appears on the projector screen: A fourth neutrino? At the sight of it, one of the IceCube scientists shakes his head, but others remain fixed, their bodies canted toward the speaker.

“We’re considering the possibility of a new neutrino,” she continues. “Based on its trajectory—the fact that it travels in the opposite direction of the neutrinos we know—this fourth neutrino would have inverted properties.”

For a moment, there is silence. The woman seems even more unnerved by this than by the commotion that preceded it, and she pauses to collect herself.

“It would be right-handed, for example. And if this is the case—if it spins not to the left, but to the right—then it would also have an inverted arrow of time.”

“Well, that explains everything,” says Louis. But a vast contagious rumble is moving through the galley. Some of the remaining attendees are chattering in small groups; others have already begun to queue in front of the presenters.

“Did you hear what they said about the arrow of time?” asks Nita. “What does that mean?”

Charlie shrugs. “Beats me.”

But Laurel can feel her heartbeat in her ears. She has the sense that she is meant to be here, right now, rooted to the spot.

“Well, time moves forward, doesn’t it?” says Louis, yawning. “So if you reverse the arrow…”

“We go backward,” Laurel says.

4

Infinite Degrees of Freedom

Laurel sat in a dim auditorium in Science Hall. It was the second day of her junior year, a perfect seventy-five degrees. A professor who had earned less respect might have seen her audience diminish, but not Gloria Albert.