
The Exquisite Precision of Time Crystals - laurex
https://www.scientificamerican.com/article/the-exquisite-precision-of-time-crystals/
======
samirillian
I like that his idea arose when he was going to teach a course on symmetry in
physics. Nice reminder that teaching is absolutely useful to a person whose
job it is to think.

------
blattimwind
Timing crystals are also exquisitely precise. For example, top-of-the-line
ovenized crystals achieve uncertainties of around 1 part per _billion_. This
seems somewhat surreal for an effect that is based on mechanical resonance.

~~~
antisemiotic
Time crystals mentioned in TFA are an entirelly different thing from crystal
oscillators.

~~~
jfengel
Can you help me understand that? The concept of "temporal symmetry breaking"
sounds exactly like oscillators.

Is it that it's a quantum-scale effect, creating a truly identical system at
each cycle, as opposed to the approximate classical-scale system of a
conventional oscillator?

~~~
GistNoesis
If I understand the article correctly, it is a less strong constraint on the
signal than being periodic, like an oscillator would be. The signal is only
periodic for specific value of time, in between those value of time the signal
is not periodic.

To give a music analogy, the constraint is like always play the same chord on
the first beat of each measure. In between you are free to play whatever
chords you like.

How does a physical system can acquire such property? I have no idea that's
the mystery a physicist will have to explain.

~~~
rfhjt
Can it be just a sum of periodic signals? For example if one signal has a
period of 7 and another of 11, the period of their sum is 7x11.

~~~
GistNoesis
No, that's something different, there is a definite state that is visited at a
regular interval.

I get your idea of using various periods : If instead of a sum of periodic
signals, you do something completely nonphysical like a product cos(x) _cos(x
/3)_cos(x/5) _cos(x /7)_any_f(x) you can observe indeed that the zero
crossings come back periodically. (Edit: something kind of an amplitude
modulation may not be so nonphysical after all)

------
benj111
'Time Crystals' sounds very retro Sci fi.

I'm sure Dr Who has fought a rubber masked alien or 2 over Time Crystals.

~~~
krapp
There was an entire season arc where the Fourth Doctor collected the pieces of
the Key to Time, which were "crystals" that assembled into a little plastic
cube...

~~~
benj111
Isn't that the plot to Through the Dragons Eye[1]? Although that came 15 years
later, it could just be ripping off a combination of The Chronicles of Narnia,
and The Dark Crystal though.

[1]
[https://m.youtube.com/watch?v=v9MXx9xej10](https://m.youtube.com/watch?v=v9MXx9xej10)
(I remember the special effects being a lot better)

Bonus points for guessing how old I am from those references.

~~~
krapp
Yeah, "collect all the pieces of the macguffin[0]" is a really common plot
device, especially in anime and obviously RPGs. It's a really simple way to
show "progress" without needing to bother with character development or power
scaling. Bonus points if each piece of the thing has a unique power that turns
out to be the cause of the conflict of the week.

[0][https://tvtropes.org/pmwiki/pmwiki.php/Main/DismantledMacGuf...](https://tvtropes.org/pmwiki/pmwiki.php/Main/DismantledMacGuffin)

------
mensetmanusman
[https://blog.mathspace.co/stones-and-
apples/](https://blog.mathspace.co/stones-and-apples/)

This is a useful description of space time.

