Paul Melko - The Walls of the Universe

John calibrated it with the cesium sample, then set the device under the detector. He started it and waited.

It took a while, but a peak began to grow. He let it sit for an hour, nervous that someone would disturb him. To occupy his mind, he started filing at a new flipper; he’d made a dozen styles for the pinball machine, and to swap them the player could simply lift off the old flipper and replace it with a new one with the same mounting.

The spectrometer beeped. John examined the screen; there was a single sharp peak. He printed the spectrum, and used a ruler to figure the center of the peak. He guessed it was about 510 keV. Just one peak meant just one isotope inside, usually.

He opened the nuclear physics book and started working through the list of elements and their gamma ray energies.

He worked his way through the list eliminating anything with a half-life less than a year and anything with a gamma ray not within 50keV of 510. He ended up with Kr-85, which had a half-life of 10.3 years and a gamma ray of 540 keV.

He wondered if he had calibrated the device wrong.

John started over, and calibrated this time with a Cobalt 60 isotope, which had two distinct peaks at 1330 and 1170 keV. Again he put the device under the detector. Again he saw the same peak, and he calculated it to be at 510 keV.

Frustrated, he put the two spectra in his backpack and walked home. Could it be that the device contained an isotope that no one here had discovered?

The next day he wandered over to the spectrometer when someone was using it.

“Excuse me, can you help me with something?”

“Sure,” the guy said in a Slavic accent.

John showed the spectrum to him, and asked, “What isotope makes a peak at 510 keV?”

The student looked at the spectrum and said, “None. You have annihilation peak here.”

“Annihilation peak?”

“Sure. Gammas interact by three mechanisms…”

“Photoelectric effect, Compton scattering, and pair production. Of course!” John laughed as he realized what he was seeing.

“I’m Alex Cheminov, by the way,” the student said. “You know your stuff. We could make a decent nuclear physicist out of you easily enough.”

“John Wilson,” John said, shaking hands. “I may have a few more questions. Do you mind?”

“Not at all.”

John realized that the peak at 510 keV, really 511 keV, was from the gammas produced when a positron hit an electron and disappeared in a burst of radiation: two equal energy gammas at 511 keV. He was seeing the tail end of the pair production interaction of gamma rays in matter.

It only happened when the gammas were highly energetic, the spontaneous breakdown of a gamma ray into an electron and positron, antimatter, as it neared a nucleus. The positron would then bounce around, slowing down until it found another electron to interact with and generate the annihilation gammas. And that was what he was seeing.

John stopped. But the annihilation radiation was the tail end of a reaction. It was seen in addition to other methods of interaction. He should have been seeing at least one higher energy peak. But he wasn’t.

Unless the positron wasn’t being created by pair production. Unless there was another source of the positrons. Unless there was antimatter inside the device, powering it.

He laughed. It made sense. To move between universes required a lot of energy. And what better form was there of compact energy than antimatter? The device was powered by antimatter. It was a sound hypothesis.

One more mystery of the device fell before the sword of science.

“Science!” he cried, and as he was in the lab, not a single person looked up in surprise.

John watched Casey smile, and his heart jolted. They were standing on the edge of a chasm in Old Shady Park. Water had etched a fifteen-meter jag into the bedrock, already scraped clean of topsoil by glaciers. Autumn leaves tumbled around them. Browns, reds, oranges, and yellows covered the ground.

Casey wore no makeup. Her hair was pulled back into a ponytail. She was the most beautiful woman he had ever seen, and he hated himself for coming to desire her so. He was leaving this universe one day and would never come back.

“Let’s go down,” she said. She caught his look. “What’s wrong? You look… pensive.”

“I’m okay.”

There was a stair that led them to the bottom of the gorge. The iron rail was wet, and the damp pulled the heat from John’s hand. The steps were carved into the rock but patched with cement in places. Still they were mossy, and the footing was slick.

Casey slipped, exhaled sharply, and grabbed John’s arm. She tensed, then relaxed into him.

“Thanks,” she said.

“Sure.”

The park was empty this early in the morning on a weekday. She had skipped her abnormal psychology lecture, and he had no classes on Wednesday morning. She had told him they needed to spend some quality time together.

Something rustled in the leaves on the other side of the rail. A chipmunk raised its head to look at them, then scampered away.

“Look!” Casey cried, before it disappeared into a hole somewhere.

From below, the U-shaped falls seemed to close in on them. The sprinkle of water splashed in a small basin of rust-colored rock. John looked up into the falling water, past the trees, and into the cloudy sky. The moisture tickled his nose.

“I feel claustrophobic,” Casey said.

Her voice echoed around the carved-out cavern behind the falls. John leaped across the weakly flowing stream. Graffiti was scrawled across the rocks behind the falls. A pile of beer cans were tossed in the dry grotto. It was clearly a hangout for local kids.

Casey hopped across the stream and joined him, hanging on to his arm.

She looked at the garbage and said, “People are so stupid. Look at this.”

“Yeah.”

John walked around the cavern. The floor had been rubbed clean and smooth over the years. During heavy rains, the place would fill up.

“Listen, John.”

He turned. Casey was standing back a couple meters, hands in her pockets. He nodded.

“I’m really sorry for, you know, reading your diary,” she said. “I shouldn’t have done that. It was really rude.”

John shrugged. He didn’t want to talk about it and had hoped that she had forgotten all about it.

“I mean it,” she pushed. “I am sorry.”

John nodded.

“Don’t you accept my apology?” she said.

“Yeah, yeah, I do.”

John was worried she’d keep at him, but she seemed satisfied with his reply.

“So, are you ready to meet my parents again?”

“Huh?”

“For Thanksgiving. You’re coming for dinner.”

The holiday was only a few weeks away.

“Casey, I don’t think-”

“John, you have to. They want to meet you again, especially since they never liked Jack so much.”

John sighed.

“No, I won’t be able to go,” John said firmly.

“Where else will you be going? You don’t have family.”

“The Rayburns will have me.”

“You’re not even related!”

John’s face flushed, but instead of yelling back, he said quietly, “I don’t want to go to your parents’ house. I don’t want to spend Thanksgiving with you and them.”

Casey’s retort died in her mouth. “You don’t-?”

“No. I’m busy with pinball stuff.”

“Pinball stuff?”

“Yeah.”

“You have got to be kidding! You’d rather spend time with your friends on that stupid game than with me?”

“I thought you were a part of it?”

She rolled her eyes.

“If I wasn’t I’d never see you. It’s either the pinball machine or whatever you have locked in that box.”

“Hey!” John cried. He hadn’t realized she knew about the box.