Hacker News Reader

Comment by dguest | Hacker News Reader

Why do we need atomic clocks in everyday devices?

Most everyday devices use quartz resonators, which, with some temperature stabilization, will gain or loose around 25 seconds a year [1]. As others have mentioned the clocks can be synced to other time sources (easily multiple times a day) such that this drift is always far less than a second. This is good enough for most everyday purposes.

You mention in another reply that some companies are installing atomic clocks on servers. As I understand it this is mainly to deal with synchronization across distributed databases. Since most everyday devices aren't actually maintaining these databases they probably make due fine with quartz resonators.

[1]: https://en.wikipedia.org/wiki/Quartz_clock#Accuracy

View on HN

There is certainly no need to have an atomic clock in each everyday device.

However, when you own one atomic clock, which you can use to calibrate all quartz resonators and many other kinds of devices used for measurement, then that is one less dependency of the outside world.

Some people like to be as independent as possible.

As long as you don't have your own atomic clock, you are dependent of Internet or other communication means and of access to institutions that do have atomic clocks, to synchronize and calibrate your devices.

In the specific case of timekeeping though what is the point?

For everything that probably 99.9999% of people do that just involves their at-home devices with no outside communications they don't need time more accurate and stable than a quartz resonator. Heck, most people could get by fine at home if all their clocks dropped the seconds display only showing hours and minutes, provided that they also had a stopwatch for when they need to time intervals smaller than a minute.

You generally only need something better when you are coordinating things that do involve communicating with the outside world in which case you can sync with outside clocks.

GPS satellites broadcast time signals; you don’t need Internet access to receive them.

But if you don’t want to be dependent even on GPS, you can apparently buy a small atomic clock for $1500, well within reach of many tech enthusiasts: https://physicsworld.com/a/atomic-clock-is-smallest-on-the-m...

You can buy SDR based GPS receiver (using atomic clocks on satellites) for very cheap. For ~1500 you can buy a 1x PCIe atomic clock and then run a sNTP server to update everything.

Well it’s for other things than just telling you what time it is.

You could have a GPS that is far more precise. Or a altimeter that detects height changes based on gravitational time-dilation.

There are tons of things you can build on top of precision timing.

The use cases may have nothing to do with time, like in the altimeter case.

Giving your GPS the ability to calculate gravitational time dilation would be cool.

According to Wikipedia [1] gravitational redshift is about 1e-16 per meter. Someone else posted a clock costing around $2k with a precision of around 1e-11 [2], so, the current commercial clock is giving us the elevation with a precision of around 100km.

To get per-meter resolution we'd need 1e-16 precision, which is on par with the more "standard" clocks in research laboratories and better than the clocks we put on GPS satellites by a few orders of magnitude. Unfortunately that just puts us on par with an existing GPS.

On the other hand, the bleeding-edge optical-lattice based atomic clocks described in this article give us altimeters with mm resolution. So we might actually be reaching the point where atomic clocks would be useful in "everyday devices". All it takes is for someone to shrink a tabletop experiment down to the size of a bar of soap, and to make it work without all the climate control, electromagnetic shielding, and vibration damping that come standard in a state-of-the-art atomic physics lab.

[1]: https://en.wikipedia.org/wiki/Gravitational_redshift

[2]: https://www.sparkfun.com/products/14830

Reply on news.ycombinator.com