Some years back there was talk of an atomic clock that came in a very small package (matchbox / cigarette pack size?). Iirc, saw a price indication of $1500 somewhere.
Something like that still around, and/or available? Any updated designs?
Personally I have no need for ultra-accurate timekeeping. But hey... an atomic clock is way cooler than a Nixie clock or oven-controlled Xtal oscillator. And no... huge 2nd hand atomic clock found on eBay etc doesn't cut it. Too big /heavy / power-hungry.
philipkglass · 1h ago
You're thinking of the Chip Scale Atomic Clock, first demonstrated by NIST in 2003 and commercialized in 2011:
Any idea what one of those would cost? (and where to buy them?)
infogulch · 1h ago
Cesium-based atomic clocks ("fountain clocks") like these use the natural resonance frequency of electron orbital energy states under a microwave laser which can be counted to measure time. Since there is a natural background noise of microwaves and many frequencies which can interact with orbitals it's important to isolate the atoms from outside sources of electromagnetic radiation and heat in order to maintain accuracy.
Earlier this year there was a big leap in so-called "nuclear clocks" which uses the resonant frequency of energy states of a nucleus itself as opposed to electron orbitals around it. Besides the "more frequency = more better" factor that has always driven clock accuracy -- thorium-229 nuclei excites in ultraviolet wavelengths -- nuclear clocks are better isolated than electron orbital-based clocks because the frequency band where they interact is impossibly narrow. In fact, the reason why it was only recently demonstrated is due to the difficulty of producing the frequency at a high enough precision to interact reliably. This could lead to more accurate and more compact and cheaper clocks.
I recall reading that our ability to measure time accurately exceeds that of any other quantity. According to the NIST, the newest Optical Lattice clocks would drift by less than 1 second if they were started 13 billion years ago at the big bang. What else can we measure down past 1 part per 10e18?
ipdashc · 19m ago
> our ability to measure time accurately exceeds that of any other quantity
Curiously, there's also a contender for the worst, which I think at present is the gravitational constant.
teraflop · 2h ago
Yup. And an interesting detail is that we know the product G·M_e (where G is the gravitational constant, and M_e is the mass of the earth) to much higher precision than we know either of its factors. And the same goes for the sun and most of the other planets.
This is because the motion of celestial bodies and spacecraft is dominated by gravitational forces which depend only on G·M, and that motion can be measured extremely accurately with e.g. Doppler radar.
What are 'limits' on how accurate enough clocks 'should' be?
Presumably there's diminishing returns, but as the article says we're at one part in 2.2e-16, are there practical application of going further?
0_____0 · 4h ago
With radio astronomy, where you're measuring phase of incoming radiation, I think "more is more" applies. Would be interesting to hear from someone who actually has experience in that domain though (not me!)
move-on-by · 4h ago
How many atomic clocks are in operation in Colorado now? It would be nice if they could be spread around a bit. I suppose there are logistical issues that keep them centralized?
fanf2 · 58m ago
As well as NIST there is Schriever spave force base https://en.m.wikipedia.org/wiki/Schriever_Space_Force_Base which is the ground operations centre for GPS. They have the USNO alternate master clock, which maintains a copy of the USNO time scale based on caesium beam and rubidium fountain clocks.
algorithmsRcool · 3h ago
The Naval Observatory in Washington DC has quite a few also
CamperBob2 · 1h ago
Commercial atomic clocks of various types aren't that rare. Every cell site has a rubidium standard and/or GPS timing, many data centers probably have a cesium standard, and radio astronomers use H-masers for interferometry.
Everybody with a GPS-disciplined oscillator has access to time and frequency from the Naval Observatory at the sub-100 ns level, optionally augmented to +/- 1 ns with reasonably affordable gear like https://www.sparkfun.com/sparkpnt-gnss-disciplined-oscillato... .
A fountain clock is on a whole different level than any of these. The same researchers who build fountains also work on even better optical lattice clocks, none of which you can buy from Sparkfun. These are research tools that don't have a market, at least not yet.
The SI second definition will likely move from Cs-133 at 9 GHz to Sr-87 at 400 THz before too long ( https://www.nist.gov/si-redefinition/second-future ), but that probably won't shake up the existing market too much.
Something like that still around, and/or available? Any updated designs?
Personally I have no need for ultra-accurate timekeeping. But hey... an atomic clock is way cooler than a Nixie clock or oven-controlled Xtal oscillator. And no... huge 2nd hand atomic clock found on eBay etc doesn't cut it. Too big /heavy / power-hungry.
https://www.nist.gov/noac/technology/time-and-frequency/chip...
https://spectrum.ieee.org/chipscale-atomic-clock
Microchip launched their latest version earlier this year:
https://www.electronicspecifier.com/products/frequency-contr...
[1] https://www.microchip.com/en-us/products/clock-and-timing/co...
[2] https://www.teledyne-si.com/en-us/Products-and-Services_/Pag...
Earlier this year there was a big leap in so-called "nuclear clocks" which uses the resonant frequency of energy states of a nucleus itself as opposed to electron orbitals around it. Besides the "more frequency = more better" factor that has always driven clock accuracy -- thorium-229 nuclei excites in ultraviolet wavelengths -- nuclear clocks are better isolated than electron orbital-based clocks because the frequency band where they interact is impossibly narrow. In fact, the reason why it was only recently demonstrated is due to the difficulty of producing the frequency at a high enough precision to interact reliably. This could lead to more accurate and more compact and cheaper clocks.
Discussion 4 months ago: https://news.ycombinator.com/item?id=42362215 | Major Leap for Nuclear Clock Paves Way for Ultraprecise Timekeeping (nist.gov)
TIL. I guess maybe that explains why the second is used as the base of the SI (https://en.wikipedia.org/wiki/2019_revision_of_the_SI) post-2019, if my understanding of it is correct?
This is because the motion of celestial bodies and spacecraft is dominated by gravitational forces which depend only on G·M, and that motion can be measured extremely accurately with e.g. Doppler radar.
https://www.nist.gov/news-events/news/1999/12/nist-f1-cesium...
https://www.iflscience.com/this-incredible-islamic-fountain-...
Presumably there's diminishing returns, but as the article says we're at one part in 2.2e-16, are there practical application of going further?
Everybody with a GPS-disciplined oscillator has access to time and frequency from the Naval Observatory at the sub-100 ns level, optionally augmented to +/- 1 ns with reasonably affordable gear like https://www.sparkfun.com/sparkpnt-gnss-disciplined-oscillato... .
A fountain clock is on a whole different level than any of these. The same researchers who build fountains also work on even better optical lattice clocks, none of which you can buy from Sparkfun. These are research tools that don't have a market, at least not yet.
The SI second definition will likely move from Cs-133 at 9 GHz to Sr-87 at 400 THz before too long ( https://www.nist.gov/si-redefinition/second-future ), but that probably won't shake up the existing market too much.