The Verdict

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“It’s my sister. She joined the cult three months ago.”

Wendy was behind the wheel of an old blue Ford pickup. Those words, spoken from the passenger seat by her colleague Camila, caused her to inhale sharply.

“I’m so sorry” was all she managed before falling silent.

Wendy wracked her brain to recall the details. The cult called itself “The Jury.” Some farmer claimed to have been contacted by aliens. His ideology was rooted in pacifism. Beyond that, Wendy remembered just one thing more: For a year now, The Jury had been foretelling a judgement day—a day that had finally arrived.

“It’s alright. I know what they’re up to. I can get her back.” Camila’s words cut into Wendy’s uneasy reflection. Before she could speak, her companion continued. “You remember the artifact, right?”

Wendy nodded as the details slowly came back. The old farmer claimed that the aliens had left a tremendous artifact on his property. He had given it some peculiar name…

“They call it The Ballot. It’s okay if you don’t remember” Said Camila. Wendy smiled wryly. This was hardly the first time that Camila had seen right through her.

“They claim they were appointed as the jury in a trial of humanity, and that aliens left them this device as a way to cast their ballot. Today was our deadline to prove our commitment to peace.”

Images from newspaper clippings resurfaced in Wendy’s mind. The artifact was a giant, silvery sculpture that resembled a hollow square balancing on one of its corners. The pictures brought words back to her lips.

“They’re going to pull some lever to trigger the message.”

Camila nodded. “Wendy, did you ever learn about something called an Elitzur–Vaidman bomb tester?”

Wendy shook her head.

“I wrote a paper on it in college,” Camila continued. “It’s this thought experiment in quantum physics. It shows that, with some probability, you can measure something without ever interacting with it. A ‘counterfactual event,’ they call it. Something that could have happened, that doesn’t happen, but still affects the outcome.”

Wendy furrowed her brow. “That sounds impossible.”

Camila shrugged. “It all comes from the fact that you can think of a quantum particle as simultaneously taking every path available to it. If you make one of those options unavailable, it can affect the result of the experiment, even if you never observe the particle to take that path.”

“What does this have to do with the cult?”

A grudging smile crept across Camila’s face. “The Ballot is built exactly like one of these devices. There’s a black box in one corner that looks inert, but they claim it’s alien technology that will generate photons. If humanity has acquitted itself, the photons will bounce off a mirror at the base and strike a detector in the other corner. If we haven’t, then The Jurists pull a lever that blocks the path of the photons.”

“So they rigged it to look like alien technology.”

Camila shook her head. “That’s the brilliance of it. That could be exposed. If they allowed anyone to examine the device, they could see it was nothing beyond human ability. So they had to build a device that looks like it couldn’t possibly operate. Its operation would be a miracle that would prove the cultists were telling the truth.”

“But when it doesn’t operate, they’ll be exposed”

Camila shook her head again. “When it doesn’t operate, they’ll explain that it was an interaction-free measurement. And no scientist will be able to conclusively prove otherwise. Think about it: What’s the problem with most doomsday cults? The appointed day of judgement arrives and nothing happens. But this time… they’ve found a way to make sure that `nothing happens` is scientifically consistent with their having sent a message to an alien civilization.”
* * *

The women arrived late to the Verdict ceremony, held in what was otherwise a nondescript acre of grazing land. But there was no difficulty finding a place to stand in the sparse crowd. They stepped from the pickup just in time to see an old man gesturing grandly by the giant, diamond-shaped artifact. Above him, a digital timer was counting down a few remaining seconds.

“On that day” the man intoned solemnly, “We were asked to adjudicate one question. Can humanity renounce its violent ways and save itself? On this day, we are asked to cast our ballot, and there are only two possibilities: yes or no.”

The old man’s eyes looked beseechingly at the small crowd. “We implored you to change. But the appointed hour has come, and we The Jury have reached a verdict.”

He pulled a large lever on the side of the device, which caused a thick back plate to slide across the lower half.

The countdown timer reached zero. Nothing happened.

* * *

“It’s just a matter of time now,” Wendy said reassuringly. Her hand rested on the wheel as they navigated the route home in the fading light of the day. “Everyone could see that nothing happened. It will just be a matter of time before their faith breaks. She’ll come back to you.”

For a long moment, Camila was silent, staring out the window at the sky. When she spoke, there was a cautious edge to her voice.

“Why didn’t they use it?”

“The artifact? They did use it. The lever…”

Camila shook her head. “The excuse. They went to great lengths to construct a genuine-looking quantum device that could explain the inevitable letdown. But no-one said anything. Perhaps that was the real counterfactual event. The thing that could have happened, but whose absence still affects the outcome.”

In the long pause that followed, Wendy’s hand gripped the steering wheel just a little tighter, and Camila kept her gaze skyward, where the first stars were beginning to appear.

“SOMEONE built a device capable of interaction-free measurement,” said Camila. “But whoever it was doesn’t seem to have told the cultists.”

About the Author: 
Colin West is a physicist at UC Santa Cruz