The orchard was closing, and the man who owned it had given them a bruised half-bushel for free if they promised to carry it. So Maya and Soren sat on the tailgate of his truck cutting apples into a bucket for cider, and the cut faces of the apples were turning brown while they watched.
"That one's faster," Maya said. She pointed with her knife. "The one you cut is faster than mine."
"They're the same apple."
"They're not. Yours is going brown at the edges already. Mine's still white in the middle."
Soren held his slice up. She was right. His had a brown rim like a coastline. Hers looked freshly cut, and he had cut hers first.
"You squeezed lemon on yours," he said.
"I did not."
"Somebody did. There's a lemon half in the bucket."
Maya looked. There was. She had cut it earlier for the man's wife, who wanted it in her water. A little of the juice had run down onto the pile.
"So the lemon stops the brown," Maya said. "Why would a lemon stop the brown."
Soren cut a fresh slice, clean, and laid it on the tailgate. Then he cut another and touched it to the lemon half and laid that one beside it. They watched.
"How long," Maya asked.
"Give it a minute."
The clean slice pinked, then browned, along the whole face. The lemon slice stayed white as a tooth.
"Okay," Maya said. "The apple isn't just sitting there. Something in it is doing something. Fast. And the lemon shuts it off."
"The brown is a reaction," Soren said. "Apple plus air. Oxygen."
"Then the clean one and the lemon one both have air on them. Same air. So it's not the air that's different."
Soren sat with that. "It's something in the apple that makes the air matter. A helper. And the lemon breaks the helper."
Maya picked up a whole uncut apple and turned it over. The skin was perfect, gold and red. "This one's had air on it its whole life. Weeks. Months. Why isn't the whole apple brown inside already?"
"Because it's not cut."
"So the helper is locked up inside the cells until you cut it. And the second you cut it, it meets the air, and" she snapped her fingers, "that fast. Not weeks. Seconds."
Soren had the notebook out. He drew two circles, a whole apple and a cut one, and wrote a number of seconds under the cut one and left the whole one blank.
"Here's what's bugging me," he said. "Apple plus oxygen. If you just left the chemicals in a jar, apple stuff and oxygen, no helper, how long would that take on its own?"
"To go brown?"
"To do the reaction. The actual reaction. Without the helper."
Maya chewed her lip. "Slow. Really slow."
"How slow, though. Guess."
"A year."
"Guess bigger."
"A hundred years. I don't know, Soren, I can't guess a number I can't picture."
"That's the thing," he said, and he was talking faster now. "Some of these helpers, the ones inside living things, they speed reactions up by so much that the number stops being a normal number. There are ones where the reaction without the helper would take longer than the Earth has been alive. Billions of years. And the helper does it in less time than it takes you to blink."
Maya stopped with her knife in the air. "Say that again."
"A reaction that would take longer than the planet has existed. And a helper in the cell does it in a thousandth of a second."
"That's not speeding up. That's" she couldn't find it. "That's cheating."
"It's not cheating. The helper doesn't get used up. It does the apple, then it does the next apple, then the next, millions of times, and it never runs out and it never gets tired."
Maya looked down at the browning slice like it had insulted her. "So this little brown coastline on your apple. This is one of the slow ones being made fast."
"This is one of the slow ones being made fast."
She was quiet. She picked up the lemon slice, the white one, and turned it in the last of the light. "And the helper is picky. It won't just grab anything. The lemon has a thing in it that jams that one exact helper and nothing else. Like the lemon knows the shape of it."
"They're all like that," Soren said. "Every helper does one job. One shape. It's got a slot, and only its own piece fits the slot, and it ignores everything else in the whole cell. There are thousands of different ones in you right now, each one doing its one reaction, all at the same time, and they don't get mixed up."
"In me right now."
"In you right now. Every cell. Reactions that should take a billion years, finishing before you can feel them start. That's what alive is. That's the whole trick. Slow chemistry, sped up so hard it looks like nothing's happening."
Maya put the two apple slices side by side on the tailgate again, the brown one and the white one, the fast one and the stopped one. She looked at them for a long time.
"Everybody thinks the interesting thing is the apple going brown," she said. "But the interesting thing is the slice that isn't. Because the not-brown one is where you can see how slow it actually wants to be. The real speed of it. Without the helper it would just sit there being white for a hundred million years."
"Yeah," Soren said.
"I like the slow one better," she said. "The slow one is the truth. The helper is the magic trick on top."
The man came back with a jug and asked if the cider apples were ready. Maya handed him the bucket without looking up.
She kept the two slices. She held them out flat on her palm the whole ride home in the dark, the brown one and the white one, checking them under each streetlight to see if the white one had finally, quietly, decided to begin.
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A science-verified short story for curious kids · Curiosity Land