4 ms·
Atomic Clocks
- LeoPanthera 2mo agoFun fact, two (very expensive) wristwatches have actual atomic timekeeping in them, instead of just receiving a radio time signal: the Bathys Hawaii Cesium 133, and a few different shaped from Hoptroff London. All released 2013-2015. Not sure what happened then for there to be suddenly two.
- hackingonempty 2mo agoSymmetricom (now owned by Microchip) released the first Chip Scale Atomic Clocks in 2011. It probably took some time for them to become available to watch designers and for them to be integrated into watch designs. https://www.nist.gov/noac/success-story-chip-scale-atomic-clock https://www.nist.gov/noac/success-story-chip-scale-atomic-cl... I'm guessing the watches sold poorly and the chip packages are still large compared to a watch movement, so no new designs.
- geerlingguy 2mo agoSadly, no major miniaturization breakthroughs since. And those CSACs still eat up a lot of power (as do good OCXOs), making them rough for battery powered wearables.
- quailfarmer 2mo agoMEMS! You should get in touch with the folks at SiTime.
- _joel 2mo agoSurely a good opportunity to tout your recent wristware Jeff? :D
- hackingonempty 2mo agoCSACs are small and efficient enough to put in a 1U box and that is all that is required by the markets that the manufacturers are chasing.
- tialaramex 2mo agoYeah, likewise the Breitling Emergency is big because it's an actual working 406 MHz Personal Locator Beacon. In principle that's all you need to have a rescue team come get you if you, I dunno, crashed your plane on a desert island or you broke your leg while hiking in Siberia, or whatever. Of course if you're the sort of person who wears a wristwatch which costs as much as a car you probably aren't doing anything like that, but you could be and maybe you're an elite solo who "travels light" and so you couldn't pack a conventional much cheaper PLB. I can't imagine Breitling sells very many of these, they're huge heavy watches, if you're The Rock they probably look fine on your arm but the average tough guy can't justify owning a watch this expensive and if you're the 5'4" female CEO of a famous company you can afford the Emergency but it looks ridiculous and feels like you're carring a boulder on your wrist. Like Concorde, sometimes we prove something was possible but it turns out it was unavoidably too expensive and annoying for it to make much sense in the market. [Edit: Fix spelling of Concorde]
- sakree 2mo agoyou would be surprised how large and passionate the watch community is. In the world of watches that breitling is big, but not really that big. It is quite a popular watch, and not that expensive : https://www.chrono24.com/breitling/emergency--mod21.htm?dosearch=true&query=Breitling+emergency https://www.chrono24.com/breitling/emergency--mod21.htm?dose...
- tialaramex 2mo agoNotice that for the actual purpose of rescue only what they're calling "Gen2" actually works. The earlier devices which make up most of the linked examples are pretty, and would doubtless make interesting jewellery for a man at a society dinner or in the boardroom, but they do almost nothing if you're alone somewhere and need rescuing today. Once upon a time, decades ago, a "beacon" is just a primitive radio transmitter which when activated produces a clearly man-made signal (it sounds like a siren basically if you're listening to it). This works pretty good if people nearby know to look for it. Then COSPAS SARSAT is a "peaceful use" satellite technology, put some satellites up above the Earth, they relay the chosen emergency frequencies and now a human operator can "hear" that beacon from hundreds of miles away. So that's all the original Emergency does. Rescue this way was sometimes a long-shot, but you did not have better options. But obviously now we can do a lot better, so eventually COSPAS SARSAT deprecated and then eventually eliminated that relay technology in favour of 406 MHz digital beacons. So now it can tell which beacon has been triggered, and you can add stuff like contact details to a database for the rescuers. This way when they get a beacon they can see the signal is Steve Smith, solo mountaineer, here's a contact number for Steve's mum, so before we commit a mountain rescue team to 18 hours of work we can verify whether Steve is currently up a mountain [maybe in urgent need of rescue] or whether he lost that beacon last month and is at home now watching Netflix. Your point is well taken - I just wanted to be absolutely clear for anybody who might get one of these that the original Emergency is now basically just pretty and only a modern "Gen2" Emergency "works" for its stated purpose.
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- r3trohack3r 2mo ago> Today’s best atomic clocks are billions of times more accurate and precise than any other type of clock. If they had been running since the Big Bang, 13.8 billion years ago, they would have lost or gained less than a second. Absolutely incredible, but then confused by the next assertion that is made without context: > New kinds of clocks may soon open up capabilities that previous generations could only dream about. What is possible by pushing past that incredibly narrow margin of 1s in 13b years? What dreamy capabilities do we get that we don’t enjoy today? Edit: I’d assumed they were talking about new approaches to making these clocks more accurate, but I wonder if they’re referring to power and form factors? I.E. an atomic clock the size of a grain of rice: https://www.nist.gov/noac/success-story-chip-scale-atomic-clock https://www.nist.gov/noac/success-story-chip-scale-atomic-cl...
- isolli 2mo agoWhat are these atomic clocks measured against?
- gucci-on-fleek 2mo agoI think that they typically use lots of other atomic clocks [0]. [0]: https://en.wikipedia.org/wiki/International_Atomic_Time https://en.wikipedia.org/wiki/International_Atomic_Time
- rcxdude 2mo agoGenerally, other atomic clocks. The fact they they tick consistently compared to each other is the main thing (though at these scales, you need to account for time dilation!).
- ahazred8ta 2mo agoClocks at NIST Boulder in Colorado run faster than NIST Gaithersburg in Maryland by about 1.55 microseconds per year because of the 1500 meter altitude difference. It's about 1 nanosecond per year per meter. They both have to use a fudge factor to adjust down to sea level.
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- Schlagbohrer 2mo agoNIST is a great example of a true Public Good. Also, has anyone else ever used their Randomness Beacon? I once used it to settle an argument in a book club over which book to read next. It's basically a very fancy and high tech coin flip. https://csrc.nist.gov/projects/interoperable-randomness-beacons https://csrc.nist.gov/projects/interoperable-randomness-beac...
- inigyou 2mo agoAs long as we forget that little thing called Dual_EC_DRBG, right?
- Intermernet 2mo agoAdmittedly, that was probably the NSA getting their grubby hands into NIST. A good thing being almost permanently tarnished by a bad thing.
- inigyou 2mo ago"RT is good except when the Kremlin gets its hands on it"
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- tomcam 2mo agoLong before most of you were born there was a special number you could call to get the time here in the USA. It would give you a localized time every 10 seconds. It was considered an authoritative value, but I knew that normal analog clocks drifted a fair amount, and I was fascinated by the Time voice. There was also a special number to dial that was called Information. When I was about 12, I suddenly thought that’s amazing, you can just call and get information. What I didn’t know at the time was that it only applied to phone numbers. One day, I called Information and asked them how accurate the time number was and what mechanism was used to deliver it. Incredibly, they connected my preadolescent self to a public relations person at AT&T. That person somehow took me seriously and hooked me up with another party. And that person told me about the cesium atomic clock used to keep track of the time. Later, I would call Information to find out the acreage occupied by the Los Angeles Zoo, and it was then that they brusquely explained to me that the number was not for general knowledge.
- OuterVale 2mo agoHere in Australia we had a number that gave you the time called 'George the talking clock'. https://1194online.com https://1194online.com
- aftbit 2mo agoThis has been reimplemented as a tribute by a modern phone phreak named Shaun Ewing, who also created Lenny. https://se.au/notes/george-the-talking-clock-lives-on/ https://se.au/notes/george-the-talking-clock-lives-on/ Number Region 02 8403 1194 Sydney/Melbourne/Canberra 08 7078 7794 Adelaide 07 3667 9594 Brisbane 08 7918 0808 Darwin 08 6244 3294 Perth
- OuterVale 2mo agoThanks for sharing this with me!
- chickensong 2mo agoIn Northern California the number corresponded to POP-CORN, so if you wanted to know the time you called popcorn, and got a lovely lady's voice: "At the tone, the time will be...". The POP prefix was a shortcut to the phone company.
- Schlagbohrer 2mo agoNot many people know NIST offers a cookbook for perfectly calibrated food https://www.nist.gov/pml/owm/metric-si/metric-kitchen/metric-kitchen-recipe-gallery/metric-kitchen-chocolate-chip-cookies https://www.nist.gov/pml/owm/metric-si/metric-kitchen/metric...
- inigyou 2mo agoAlso known as an ordinary recipe everywhere else. Well, recipes do often use measurements like teaspoons and cups, but they have straightforward metric equivalents - a teaspoon being 5mL and a cup 250mL.
- aftbit 2mo agoYou should really measure mass rather than volume.
- NetMageSCW 2mo agoThat depends on the state of what you are measuring. For some ingredients mass and volume will always be equivalent.
- firasd 2mo agoWhat, Exactly, Is a Clock? To understand atomic time, we must first understand something about clocks. A clock is, at its core, a marriage of two components: a mechanism that oscillates, or ticks with a steady beat, and a device that counts those beats and displays the time Yeah but more deeply time is a property of the universe that the clock including atomic clocks are tracking. Kant said it is 'schema' i.e. without understanding time we wouldn't even understand causality so it is the purest possible a-priori concept that doesn't rely on sensory input to learn about This is why I like using my Alphadec system that splits the year into 26 chunks from A-Z <https://github.com/firasd/alphadec https://github.com/firasd/alphadec> as my working dir; eg. right now the current Alphadec is '2026_P5M7_200286' so my working dir is Documents/work/2026_P. That way there is a folder system automatically imposed on various .js or .py stuff without having to pre-create a taxonomy since 'time is schema'--I can estimate "that ffmpeg project was in Spring so it must be around 2026_F.."
- benterris 2mo agoNot sure I get what is better about this than simply using the month, like Documents/work/202606 (which also sorts nicely and does not need a conversion in my head to know what time of the year that must be)
- firasd 2mo agoYup as far as the folder taxonomy thing ISO YYYYMM works fine too Alphadec is just a timezone free UTC encoding that works down the millisecond so I also use it for snapshots eg myscript.py.backup.2026_P5G6_328054_Aug06.txt So then when I'm doing multiple revisions I don't have to worry about which revision of 20260806's day it was etc. Unix time in ms would work too but Alphadec is a little bit nicer to me than saying myscript.py.backup.1786086462604.txt
- terminalbraid 2mo ago> Yeah but more deeply time is a property of the universe that the clock including atomic clocks are tracking. I'll quote Einstein who said "time is what the clock says".
- atypeoferror 2mo agoI recently bought my first not-super-cheap watch, and found out that all around the world there radio stations which broadcast the atomic clock time that a lot of clocks/watches listen to. After setting the time zone (I guess this also changes the frequency that it listens on) it starts to sync itself using that signal. It is also solar-charging - so this basically means that I never have to touch it. Although it's an analog watch, because of this sync, it correctly handles DST, the date window (including leap year) - basically I never have to touch it again until it breaks . All without bluetooth or internet connection - pretty cool I think. Casio Oceanus t200 for anyone that cares.
- ncruces 2mo agoThat “all around the world” leaves significant gaps: https://hagensieker.com/2019/11/17/multiband-6-what-is-it/ https://hagensieker.com/2019/11/17/multiband-6-what-is-it/ I had a weather station with an external antenna that could never sync, even during the night, even placed outside in the "best" side of the house on my neck of the EU. A solar powered, low battery wristwatch that's never outside in the middle of the night will fare much worse. It's interesting old school tech that works fine in the places where it does work. For elsewhere, I guess synching through a phone is more practical. So far it works fine. I just hope it doesn't get deprecated (I do, unfortunately, have a feeling the Casio app will break before the radios stop transmitting).
- dingaling 2mo agoSyncing directly from a 4G signal would be a lot more practical than VLF or HF time signals, but I haven't found a wall clock that does so.
- ncruces 2mo agoOn the one hand, yes. On the other, my country has just shut down 3G and 2G only stays because it's still used by emergency services. How long will 4G last? Longer than bluetooth and the Casio app? It'd be nice if something like this could be maintained long term. The US, UK and Germany signals have been working since the ~1960s.
- svennidal 2mo agoIt's still relative. I think... If you could have a atomic wristwatch and you travel around the world with it, you will have a very precise time for you, but you'll end up out of sync with almost every other atomic clock. If you sync two atomic clocks and put one at the surface of the arctic ocean and another one on top of Mount Nevado in Peru, and leave them there for one million years, the clock in Peru will be 1.88 years ahead of the clock in the arctic. That is a difference of 0.44 nanoseconds per day. Don't quote me on that though.. I'm not a physicist.
- spot13 2mo agoTime is not a constant
- hnihm78ttk 2mo ago[dead]
- rammy1234 2mo agoI wish we had books for kids at school that explains in this fashion. Even a beginner can grasp the idea behind it and dive deeper if interested. Loved it.
- alnwlsn 2mo agoIf you want to see how an actual application of this works, I've yet to see a description better than in CuriousMarc's HP 5061A series: https://www.youtube.com/watch?v=eOti3kKWX-c https://www.youtube.com/watch?v=eOti3kKWX-c
- Crunchified 2mo agoIf I had an atomic clock, it'd probably be blinking 12:00.