The Thinnest Thing in the Junk Drawer

The box said FRAGILE and also, in smaller letters, MoS2 / hBN samples do not stack.

"Do not stack," Soren read out loud. "Someone underlined it twice."

Maya was already lifting the lid. Inside were rows of little glass slides, each holding a smear of something. Some looked like nothing at all. One had a shine to it, gray going to purple. There was a card taped inside the lid, curling at the corners.

"Read the card," Maya said.

"This one glows," Soren read. "Question mark. Then a name. Then, only when it's alone."

"Only when what's alone."

"It doesn't say."

Maya held a slide up to the shop window. The afternoon light came through it and did nothing special. "This is supposed to glow?"

"The card says one of them does."

"They all look dead."

Soren's aunt called from the back that they could keep any junk that wasn't wired to anything. This was not wired to anything. Soren pulled his notebook out of his jacket and set it on the counter, open, a pencil across it.

"Okay," he said. "Only when it's alone. Alone from what?"

"From the others?" Maya spread the slides out across the counter so none of them touched. She waited. "Nope. Still dead."

"Maybe alone means something else."

Maya picked one slide back up, the gray-purple one, and turned it. She frowned at the edge of the smear, where it thinned out to almost nothing. "Soren. Look at the middle versus the edge."

He looked. The middle of the smear was thick and dull, like pencil lead. The edge, where somebody had dragged it thin, was faintly, stubbornly bright. A little seam of light along the rim.

"The edge is doing something," he said.

"The thin part is doing something. The thick part is dead." Maya tilted it back and forth. The bright seam stayed at the edge. "Whatever it is, it likes being thin."

Soren wrote thin = alive, thick = dead, then stopped, because that wasn't right either. "It's the same stuff, though. Same smear. Same material. It can't be alive in one spot and dead an inch over."

"But it is."

"Same material can't have two different personalities."

"Says who," Maya said.

Soren looked at the card again. Only when it's alone. He looked at the thick middle, where the material was piled on top of itself, layer on layer on layer. He looked at the thin edge, dragged down to almost nothing.

"Alone," he said slowly. "What if alone means one layer. One layer of atoms. By itself." "In the middle it's stacked," she said. "Layers sitting on layers. That's the dead part."

"And at the edge somebody smeared it so thin it's down to a single sheet." Soren's pencil hovered. "And the single sheet glows and the stack doesn't."

"That's the same word," Maya said. "Do not stack. On the box. It's not about breaking. It's an instruction. If you stack them you turn them off."

They both looked at the box lid. Do not stack. Two atoms of the same thing, one on top of the other, and the light goes out.

"That's insane," Soren said, and he meant it as a compliment. "That's not how anything works. Gold is gold whether you have a nugget or a flake. Water is water in a drop or an ocean."

"This isn't," Maya said. "This one changes when you get down to nothing. One layer, it's one thing. Two layers, it's a different thing. Same atoms."

"So the property isn't in the atoms." Soren said it and then had to sit with it. "It's in the thinness. The being-one-layer is the property."

Maya was pulling the other slides toward her now, one at a time, hunting for edges. "Then every one of these is hiding something at the rim." She held up a clear one that had looked like empty glass. Tilted it. At the very edge, where it thinned to a single sheet, it was doing something to the light, a slick of color that wasn't paint.

"That one wasn't nothing," Soren said. "We were looking at the thick part and calling it nothing."

"The whole box looked like junk." Maya laughed, a little stunned. "It looked like smears of gray junk because we were looking at the stacks. The junk was the off switch. The real thing is a single atom thick and we kept looking past it."

Soren wrote one layer is a different substance than two layers of the same thing. Then he stopped writing and just looked at the row of slides, each one with its bright rebellious edge.

"There are dozens of these," he said. "The card names four. But the box says dozens."

"Dozens of materials," Maya said, "that only turn into themselves when they're alone. And nobody would ever know unless they got them down to one layer and looked at the edge."

"It's a whole set," Soren said. "Like the periodic table. Except the periodic table is about which atoms. This is about how thin."

Maya stopped. "That's a second table."

"What?"

"There's the table of what things are made of. And there's a whole other table nobody drew yet, of what things become when they're one layer thick." She was talking fast now. "Same atoms, brand new square on a table that doesn't exist yet. The properties don't live in the stack. They live in the flatness. You have to squash it down to a single sheet before the material tells you the truth about itself."

Soren looked at his aunt's shop, the shelves of thick dead things, radios and toasters and cables. Then at the counter, where a smear of gray was glowing along one thin edge because there was nothing sitting on top of it.

"Do not stack," he read, one more time, off the lid.

Maya slid the last clear slide to the window and turned it until the edge caught the light. A thread of color ran along the rim, one atom wide, shining because it was alone.