Time Crystals

I couldn’t find any actual pictures of time crystals, so here are some coupled pendulums.

A short story, based on a cool bit of recent news.

****

“Now, onto time crystals. They sound like something out of Doctor Who, but what are they really?”

Professor Priya Varsani picked up a lattice model pinched from the undergraduate labs and held it up in front of the camera.

“Well,” she said, watching herself on the monitor, “a normal crystal is a material with a pattern that repeats across space. So in this model of a salt crystal, you see it goes from blue – that’s the sodium – to yellow – chloride – and then blue, and then yellow, and this pattern can repeat forever. In a time crystal, you also have atoms, or ions, linked together, and you set them up so they’re always moving. Do it just right, and you can make them tick like a clock, always returning to the same position and then repeating the pattern over and over. That’s why it’s called a time crystal. The pattern doesn’t repeat in space but in time.”

“That’s good,” Tina the producer said. “You said ‘repeating’ too much, but I think we can cut a bit out and it will sound fine. Alright Simon, next question.”

“So, you say these time crystals keep going forever. Well, doesn’t that violate the laws of physics? I mean, that sounds like perpetual motion to me! Do we have to rewrite the textbooks?”

“Well, it doesn’t really violate the laws of physics. You kickstart it and it keeps going, because there’s nothing to stop it moving – a little bit like the planets orbiting a star, or an electron orbiting an atom. But it doesn’t create new energy, and it won’t exactly last forever. Eventually something will stop it. Maybe the Earth will get so hot it melts, or maybe the universe will expand so much it tears it apart. So it doesn’t really break any of the laws of thermodynamics. It just puts them on hold for a bit.”

Simon held up a hand to the camera. “Hold on, the university press kit here specifically says… hang on, ‘This revolutionary discovery totally reshapes our understanding of the laws of physics’. Could you say something like that? Something to keep the viewers interested, you know?”

Amanda, the university press officer, nodded. “Spice it up a bit, Priya. Come on, this is exciting work! Don’t downplay it. ‘Perpetuum mobile of the fourth kind’, remember?”

Simon dropped his fingers, a sign to start recording again.

“So, you mentioned that these time crystals keep going forever. That sounds like perpetual motion, and I thought the laws of physics said that was impossible. Do we have to rewrite the text books?”

“Well, this discovery – revolutionary discovery, ah, reshapes our understanding of the laws of physics. There are three types of perpetual machines that the laws of physics say are impossible: you can’t have a machine which produces free energy, you can’t have one that perfectly converts one form of energy into another, and you can’t have one that stores energy forever. But this is a fourth kind of perpetual motion machine, which doesn’t do those things. So it will keep going for a long time, but it will have to stop one day. Maybe the Earth will get eaten by the sun, or something, and then the time crystal will stop. It doesn’t break the laws of physics, it just puts them on hold a bit.”

Simon glanced very quickly at his notes, and then grinned and turned to Priya. “What applications do time crystals have? I mean, will we all have time crystals in our homes soon?”

“Er, the appli- the application is…”

“Hang on,” Tina said. “Can we try that again? You mumbled a bit, Prof.”

“Sorry. Sure.”

Simon smiled. “So, what applications do time crystals have? Will we all have one in our homes soon?”

“Well, you won’t have one in your home, but companies like Google and big government agencies like NASA or the NSA will all want them. You see, you can use time crystals to store information like on, er, a memory stick and you could use that to build a quantum computer, which would be able to crack codes and solve problems that would take a normal computer hundreds of years.”

“Hold on, hold on.” In bounded Amanda, leaping across to ruin the shot. “You can’t mention the NSA like that. It might give people the wrong impression. We don’t want people thinking time crystals are evil or that we’re working for the NSA or anything. And you can’t name Google either. ‘Search engines, NASA, the Met Office,’ those are the ones you’re cleared to say. Absolutely do not say anything about using time crystals to break codes!”

“It’s not the time crystals, it’s the quantum computers that…” Professor Varsani glanced at the gaping black eye of the camera, and the faint image of her face was smeared in rings around the edge of the lens. She was going to be on TV. And she’d heard horror stories from other scientists about what the media did to their precious research.

They could make it sound like you were some ivory tower idiot, deliberately wasting taxpayers money studying the bloody obvious. Or they could make you out to be an officious busybody trying to push a politically-correct agenda while banning the few remaining simple pleasures of life. They could even portray you as an amoral monster out to play God, a twenty-first century Oppenheimer.

“No, you’re right. I’ll do that again.”

“Let’s take it from the top, shall we?” Tina said.

“Oh, Priya, one more thing,” Amanda added. “Could you not use the word ‘space’? It confuses the public. They’ll be thinking of, you know, space. Stars and planets and whatever.”

“What, er, what can I say instead?”

“I don’t know, you’re the scientist. Maybe something like ‘It repeats as you go along’?”

Priya chewed her lip and glanced back at the blackboard propped up at the back of the room. Goodness knows where they found that – the whole department had been upgraded to whiteboards and PowerPoint projectors about a decade ago. The equations on the board had been picked at random out of the sheaf of papers the university bundled in with its press pack.

V1 = − κ1 dφ/dx + ½λ1 (dφ/dx)2

Where on Earth had they dug that up from? Priya couldn’t even remember writing that. Something to do with the potential energy of a crystal, she supposed. Yes, the Langrangian. Why had they picked that? It wasn’t even really to do with time crystals. She turned back to Tina.

“’It repeats through the structure’? Does that sound all right?”

“Yeah, that works. Want to give it another go?”

Professor Varsani took a deep breath and nodded. Tina counted down on her fingers.

“Now, onto time crystals. They sound like something out of Doctor Who, but what are they really?”

Professor Priya Varsani picked up a lattice model pinched from the undergraduate labs and held it up in front of the camera.

“Well,” she said, watching herself on the monitor, “a normal crystal is a material with a pattern that repeats across space. So in this model of a salt crystal, you see it goes from blue – that’s the sodium – to yellow – chloride – and then blue, and then yellow, and this pattern can repeat forever. In a time crystal, you also have atoms, or ions, linked together, and you set them up so they’re always moving. Do it just right, and you can make them tick like a clock, always returning to the same position and then repeating the pattern over and over. That’s why it’s called a time crystal. The pattern doesn’t repeat in space but in time.”

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