Free Johnny and the Bomb by Terry Pratchett

suddenly and—”
    “And what?” said Kirsty.
    “—and…er…bang, good night, Europe,” said Yo-less. “You can’t argue with nuclear physics, sorry.”
    “My arms wouldn’t end up sticking out of a wall?” said Wobbler, who hadn’t quite caught up.
    “No,” said Yo-less.
    “Not a wall near here, anyway,” said Bigmac, grinning.
    “Don’t wind him up,” said Yo-less severely. “This is serious. It could happen to any of us. We dropped when we landed, right? Does that mean that if we suddenly go back now, we’ll be sticking out of the floor of the mall, causing an instant atomic explosion?”
    “They make enough fuss when you drop a Coke can,” said Johnny.
    “Where’s Wobbler gone?” said Kirsty.
    Wobbler was a disappearing shape, heading for the allotments. He shouted something.
    “What’d he say?” she said.
    “He said, ‘I’m off home!’” said Johnny.
    “Yeah, but…” said Bigmac, “where he’s running now…if we’re where the mall is…will be…then over there’s the shopping center. That field he’s running across.” He squinted. “That’s where Curry’s is going to be.”
    “How will we know we’re about to go back?” said Yo-less.
    “There’s a sort of flicker for a moment,” said Johnny. “Then…zap. Er…what’ll happen if he comes out where there’s a fridge or something? Is that as bad as a concrete wall?”
    “I don’t know much about fridge atoms,” said Yo-less. “They might not be as bad as concrete atoms. But I shouldn’t think anyone around here would need new wallpaper ever again.”
    “Wow! An atomic Wobbler!” said Bigmac.
    “Let’s get the cart and go after him,” said Johnny.
    “We don’t need it. Leave it here,” said Kirsty.
    “No. It’s Mrs. Tachyon’s.”
     
     
     
    “There’s just one thing I don’t understand,” said Yo-less as they hauled the cart across the field.
    “There’s millions of things I don’t understand,” said Johnny.
    “What? What? What are you going on about now?”
    “Televisions. Algebra. How skinless sausages hold together. Chinese,” said Johnny. “I don’t understand any of them.”
    “The cart’s got no works,” said Yo-less. “There’s no time machinery.”
    “Maybe the time is in the bags,” said Johnny.
    “Oh, right! Bags of time? You can’t just shove time in a bag!”
    “Maybe Mrs. Tachyon didn’t know that. She’s always picking up odds and ends of stuff.”
    “You can’t pick up time, actually. Time’s what you pick things up in,” said Kirsty.
    “My granny saves string,” said Bigmac, in the manner of someone who wants to make a contribution.
    “Really? Well, you can’t pick up the odd half hour and knot it onto another ten minutes you’ve got spare, in case you haven’t noticed,” said Kirsty. “Honestly, don’t they teach you any physics at your school? Fridge atoms was bad enough! What on earth’s a fridge atom?”
    “The smallest possible particle of fridge,” said Yo-less.
    Perhaps you could save time, Johnny thought rebelliously. You could waste it, it could run through your fingers, and you could put a stitch in it. Of course, perhaps that was only a manner of speaking and it all depended on how you looked at it, but Mrs. Tachyon looked at things in a corkscrew kind of way.
    He remembered touching a bag. Had time leaked out? Something had hissed through his fingers.
    “You can’t have the smallest possible particle of fridge! It’d just be iron atoms and so on!” said Kirsty.
    “A fridge molecule, then. One atom of everything you need to make a fridge,” said Yo-less.
    “You couldn’t ha—well, all right, you could have one atom of everything you need to make a fridge but that wouldn’t make it a fridge molecule because—” She rolled her eyes. “What am I saying? You’ve got me thinking like that now!”
    The rest of the universe said that time wasn’t an object, it was just Nature’s way of preventing everything from happening