# Space-time crystals **URL:** \ **Category:** Factual Questions\ **Created:** [June 22, 2018, 12:23am UTC](https://boards.straightdope.com/t/space-time-crystals/816546 "2018-06-22T00:23:46Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![EastUmpqua](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eastumpqua/32/6025_2.png) [@EastUmpqua](https://boards.straightdope.com/u/EastUmpqua)\ **Post date:** [June 22, 2018, 12:23am UTC](https://boards.straightdope.com/t/space-time-crystals/816546/1 "2018-06-22T00:23:46Z")
If you plucked a hypothetical frictionless guitar string, would that be a space-time crystal? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 22, 2018, 1:33am UTC](https://boards.straightdope.com/t/space-time-crystals/816546/2 "2018-06-22T01:33:21Z")
Dude, step away from the keyboard until you’re sober again. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [June 22, 2018, 2:06am UTC](https://boards.straightdope.com/t/space-time-crystals/816546/3 "2018-06-22T02:06:02Z")
I think he’s talking about this [Time crystal - Wikipedia](https://en.wikipedia.org/wiki/Time_crystal) "A time crystal or space-time crystal is a structure that repeats in time, as well as in space. Normal three-dimensional crystals have a repeating pattern in space, but remain unchanged as time passes. Time crystals repeat themselves in time as well, leading the crystal to change from moment to moment. A time crystal never reaches thermal equilibrium, as it is a type of non-equilibrium matter — a form of matter proposed in 2012, and first observed in 2017. " “The idea of a time crystal was first described by Nobel laureate and MIT professor Frank Wilczek in 2012. Later work developed a more precise definition for time crystals. It was proven that they cannot exist in equilibrium.[1] Then, in 2014 Krzysztof Sacha at Jagiellonian University in Krakow predicted the behaviour of discrete time crystals in a periodically-driven many-body system.[2] In 2016, Norman Yao et al. at the University of California, Berkeley proposed a different way to create time crystals in spin systems. From there, Christopher Monroe and Mikhail Lukin independently confirmed this in their labs. Both experiments were published in Nature in 2017.” ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 22, 2018, 1:00pm UTC](https://boards.straightdope.com/t/space-time-crystals/816546/4 "2018-06-22T13:00:21Z")
Huh, that actually makes some sense, then. Thank you, **Andy L**. The first issue that I can see is that a non-dissipative guitar string won’t behave the way you’d expect when plucked. We’re used to a guitar string forming a nice sinusoidal pattern when plucked. But really, a pluck will excite a large number of modes (infinite, actually, though most of them will be very low amplitude), each with its own frequency, resulting in a very complicated waveform. In real life, the higher-frequency modes dissipate more quickly, resulting in the total waveform quickly being dominated by the fundamental, which is why we think of the form as being clean. Now, that in itself would still be periodic, since all of the higher modes have frequencies which are integer multiples of the fundamental frequency. But that actually only holds to the extent that the displacement is small compared to the length of the string, and that’s never going to be completely true, either. So even without dissipation, you’ll still get some energy transfer between the modes, and so it won’t exactly repeat at all. ---
**Author:** ![Darren\_Garrison](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darren_garrison/32/92_2.png) [@Darren\_Garrison](https://boards.straightdope.com/u/Darren_Garrison)\ **Post date:** [June 22, 2018, 1:36pm UTC](https://boards.straightdope.com/t/space-time-crystals/816546/5 "2018-06-22T13:36:04Z")
Other issues are that a guitar string is not a crystal and a vibrating guitar string isn’t rearranging the crystal lattice that it isn’t. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [June 22, 2018, 2:39pm UTC](https://boards.straightdope.com/t/space-time-crystals/816546/6 "2018-06-22T14:39:47Z")
Oh, and I also owe an apology to **EastUmpqua** , for assuming that his question was chemically-induced, when it turns out it was actually sane. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [June 22, 2018, 3:42pm UTC](https://boards.straightdope.com/t/space-time-crystals/816546/7 "2018-06-22T15:42:56Z")
> [@Chronos](#): > > Oh, and I also owe an apology to **EastUmpqua** , for assuming that his question was chemically-induced, when it turns out it was actually sane. There should be a term for that-maybe “reality whoosh”? ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [June 24, 2018, 6:11pm UTC](https://boards.straightdope.com/t/space-time-crystals/816546/8 "2018-06-24T18:11:25Z")
> [@Chronos](#): > > Huh, that actually makes some sense, then. Thank you, **Andy L**. > > The first issue that I can see is that a non-dissipative guitar string won’t behave the way you’d expect when plucked. We’re used to a guitar string forming a nice sinusoidal pattern when plucked. But really, a pluck will excite a large number of modes (infinite, actually, though most of them will be very low amplitude), each with its own frequency, resulting in a very complicated waveform. In real life, the higher-frequency modes dissipate more quickly, resulting in the total waveform quickly being dominated by the fundamental, which is why we think of the form as being clean. > > Now, that in itself would still be periodic, since all of the higher modes have frequencies which are integer multiples of the fundamental frequency. But that actually only holds to the extent that the displacement is small compared to the length of the string, and that’s never going to be completely true, either. So even without dissipation, you’ll still get some energy transfer between the modes, and so it won’t exactly repeat at all. No problem. Thanks for the insight about non-dissipation and transfer of energy between modes. ---
**Author:** ![Leo\_Bloom](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leo_bloom/32/10377_2.png) [@Leo\_Bloom](https://boards.straightdope.com/u/Leo_Bloom)\ **Post date:** [June 24, 2018, 7:12pm UTC](https://boards.straightdope.com/t/space-time-crystals/816546/9 "2018-06-24T19:12:18Z")
> [@Chronos](#): > > Huh, that actually makes some sense, then. Thank you, **Andy L**.[snip, real answer]… Nothing for OP? ETA: Wow, A guy who works 9-5 in really weird reality that nobody gets _himself_ is reality-whooshed. A lesson for us all.