7 ms·

I did a deep dive on this once: Coordinated Universal Time (UTC) is coordinated among ... who? The answer (at least when I looked into it): University of Paris,

I did a deep dive on this once: Coordinated Universal Time (UTC) is coordinated among ... who? The answer (at least when I looked into it): University of Paris, NIST, and the US Naval Observatory. The other two are constantly comparing state of the art atomic clocks. USNO is the only member looking outward.

Animats 3y ago
Those are the time people. There's also the Earth Rotation Service.[1] They track what the planet is doing. The Earth Orientation Center, in Frankfurt, Germany, tracks where the poles are pointed and the rotation speed. These are the people behind leap seconds. It all comes down to 3 numbers.[2] [1] https://www.iers.org/ https://www.iers.org/ [2] https://www.iers.org/IERS/EN/DataProducts/tools/eop_of_today/eop_of_today_tool.html https://www.iers.org/IERS/EN/DataProducts/tools/eop_of_today...
- ReactiveJelly 3y ago
  > These are the people behind leap seconds. So they are my enemies
  - FridgeSeal 3y ago
    I’m sorry, we can only accept them as “enemies” if you have a suitably Machiavellian plan to defeat them. 12 points and a snazzy PowerPoint presentation in the nearest secret volcano lair if you please.
  - techdragon 3y ago
    You have been lied to… your true enemies are the ones that continue to build monotonic systems on top of non monotonic time scales… Join us in the Temps Atomic International! TAI is the one true timescale. Computers should be using TAI and converting to UTC when humans want to see a local human time. My sincere belief is this was a bigger mistake than null, bigger than all the Y2K “we stored the year as 2 digits” stuff… The fact that from the BIOS/system Firmware up “we” decided to use a fuzzy time scale that changes on an unpredictable but just infrequent enough almost everyone can ignore it even exists except for when it changes and they remember it exists… genuinely a poor choice that I suspect is in large part due to a lot of people not knowing about TAI
    - RetroTechie 3y ago
      > (..) but just infrequent enough almost everyone can ignore it ... If it's only a problem for the experts, then it isn't really a problem, right? The experts can decide for themselves how hard they work on solving self-invented problems.
      - t8sr 3y ago
        Huh? Ok, so what do you propose: should time keeping diverge from the day-night cycle, or should we have leap seconds? There is no third option - the Earth just doesn’t turn the way you want it to. It becomes your problem in a hurry once you encounter a 61-second minute and your stuff all breaks.
        techdragon 3y ago
        Not really disagreeing just expanding on the conversation… I’m pretty happy with computers storing time as a “weird number that we add another number to to get the human time”… because we are already usually storing it as second/millisecond/etc offset from an arbitrary fixed point in history… we’re talking about going from “current integer (prefix)seconds value -> (some math involving leap year formulas and fiddly stuff not just x/365/24/etc) -> human display value” adding one single subtraction step to the some math part that that already has a bunch of other fast assembly arithmetic calculations involved in it. As for divergence. We have two kinds of timekeeping. “Calendrical timekeeping” which will always get fixed to be close enough to the solar year that no one has a problem with it, and “Chronological timekeeping” which is basically the science of keeping a track of how many seconds have passed between arbitrary moments in time. All Calendrical timekeeping have for decades now been built on top of TAI and the science of Chronological timekeeping where metrologists have kept fastidious watch over atomic clocks and matched the beating of their resonating frequencies to the astronomical record keeping to allow ever more precise astronomy and the byproduct of this effort have been precise records of how long in scientifically precise seconds each day has been, and from these records we know we have to occasionally “add” a second if we want the “human time” to stay within 1 second of the astronomical time. Consequently we can simply decide we are happy with more or less drift. One second is small enough we can kinda just deal with it, but imagine having a leap minute every hundred years? Coordinate that mess, or how about a leap hour once a millennium? It’s trivial for people we don’t really time anything as humans faster than a second, so if we skip one it’s pretty much ok… it’s categorically on an issue for computers… which should never have used UTC and should have always used TAI because TAI doesn’t skip a second and so the fix would be “a fixed lookup table or a single if branch based on the date and the number of integers to add when doing the integer representation to human representation mathematics before updating the clock on your screen.
  - fanf2 3y ago
    Most of the people responsible for implementing leap seconds want to get rid of them too. The international bureaucratic wheels are grinding slowly towards abolition: should be more successful this time than the previous attempt ~15-20 years ago.
- jdougan 3y ago
  The International Earth Rotation Service is possibly my favorite name for an international bureaucracy. It give me visions of a Giant Control Lever extending deep into the Earth, with the labels Faster and Slower.
  - twic 3y ago
    People say money makes the world go round. False. The International Earth Rotation Service makes the world go round.
  - Avshalom 3y ago
    You can actually slow down or speed up the planet's rotation with a big switch. |_ open switch, slower __ closed switch faster You can also do it yourself by standing up or laying down
    - oh_sigh 3y ago
      I wonder how big the switch would need to be to be able to transmit info via the rotational speed as hest we can measure it.
    - gshubert17 3y ago
      What happened to the rotation rate around the beginning of 2019, to cause the big change in the slope of the UT1-UTC line (https://crf.usno.navy.mil/ut1-utc https://crf.usno.navy.mil/ut1-utc)? After adding 5 leap seconds in 11 years, no leap seconds have been added or subtracted since the end of 2016.
      - techdragon 3y ago
        Its probably not the only component... but a fun fact is that the Earth's rotation is affected by the average equatorial ocean temperatures, (anyone seen the ocean temperature charts this year... something something ships and sulfur dioxide accidental geoengineering that we stopped doing) warm ocean water displaces slightly more volumetrically and thus by way of its lower density, affects the spinning mass balance of the Earth like a ice skater curling in their fingers rather than their whole arms while spinning like a top, the effect is there... just so very subtle.
- fanf2 3y ago
  The IERS web site says the EOC is at the Paris Observatory, but much of the data (such as Bulletin A) comes from the Rapid Service/Prediction Centre at the USNO.
- throw0101b 3y ago
  Someone submitted a 'story' for the IERS that's getting some votes: * https://news.ycombinator.com/item?id=37777116 https://news.ycombinator.com/item?id=37777116
Gooblebrai 3y ago
What other two?
beerandt 3y ago
While the Navy's time keeping mission is fascinating on its own (and itself was(is) a prerequisite for navigational abilities) the understated 'read-between-the-lines' reason the Navy looks "outward" is because that's how it points the nukes.
robviren 3y ago
I love stuff like this so much. You take something as seemingly complex as time or weight and it ends up boiling down to like a handful of people diligently crunching numbers or a hunk of exactly 1 KG of platinum sitting in the basement of some French lab. Dispelling the "magic" behind these things utterly fascinates me.
fanf2 3y ago
That isn’t quite right. UTC was originally (early 1960s) coordinated between the British and Americans. This was related to their existing collaborations in time and navigation. The definition of the atomic second was established in 1955-1958 by a collaboration between NPL (London) who had the first good atomic clock, and the USNO who were good at the astronometric work to establish the ephemeris second. The USNO and the Greenwich observatory also prepared the Astronomical Almanac together. Later on, as other countries wanted to use the same atomic timescale, the BIH (bureau international de l’heure, based at the Paris observatory) took over. More recently, the BIH was split. The part responsible for atomic time moved to the BIPM (bureau international des poids et mesures, in Sévres just outside Paris) who are responsible for the definition of the second, so it makes sense for them to be responsible for its realisation as well. They maintain atomic time based on contributions from many atomic clocks in many time labs around the world. The astronomy parts of the BIH became the IERS (international earth rotation service), still based at the Paris Observatory. However, a significant part of their practical scientific work is carried out by the USNO. For instance IERS Bulletin A is sent out each week by the USNO. Earth orientation is needed for the GPS as well as for leap seconds.

Animats 3y ago

Those are the time people. There's also the Earth Rotation Service.[1] They track what the planet is doing. The Earth Orientation Center, in Frankfurt, Germany, tracks where the poles are pointed and the rotation speed. These are the people behind leap seconds. It all comes down to 3 numbers.[2] [1] https://www.iers.org/ https://www.iers.org/ [2] https://www.iers.org/IERS/EN/DataProducts/tools/eop_of_today/eop_of_today_tool.html https://www.iers.org/IERS/EN/DataProducts/tools/eop_of_today...

ReactiveJelly 3y ago
> These are the people behind leap seconds. So they are my enemies
- FridgeSeal 3y ago
  I’m sorry, we can only accept them as “enemies” if you have a suitably Machiavellian plan to defeat them. 12 points and a snazzy PowerPoint presentation in the nearest secret volcano lair if you please.
- techdragon 3y ago
  You have been lied to… your true enemies are the ones that continue to build monotonic systems on top of non monotonic time scales… Join us in the Temps Atomic International! TAI is the one true timescale. Computers should be using TAI and converting to UTC when humans want to see a local human time. My sincere belief is this was a bigger mistake than null, bigger than all the Y2K “we stored the year as 2 digits” stuff… The fact that from the BIOS/system Firmware up “we” decided to use a fuzzy time scale that changes on an unpredictable but just infrequent enough almost everyone can ignore it even exists except for when it changes and they remember it exists… genuinely a poor choice that I suspect is in large part due to a lot of people not knowing about TAI
  - RetroTechie 3y ago
    > (..) but just infrequent enough almost everyone can ignore it ... If it's only a problem for the experts, then it isn't really a problem, right? The experts can decide for themselves how hard they work on solving self-invented problems.
    - t8sr 3y ago
      Huh? Ok, so what do you propose: should time keeping diverge from the day-night cycle, or should we have leap seconds? There is no third option - the Earth just doesn’t turn the way you want it to. It becomes your problem in a hurry once you encounter a 61-second minute and your stuff all breaks.
      - techdragon 3y ago
        Not really disagreeing just expanding on the conversation… I’m pretty happy with computers storing time as a “weird number that we add another number to to get the human time”… because we are already usually storing it as second/millisecond/etc offset from an arbitrary fixed point in history… we’re talking about going from “current integer (prefix)seconds value -> (some math involving leap year formulas and fiddly stuff not just x/365/24/etc) -> human display value” adding one single subtraction step to the some math part that that already has a bunch of other fast assembly arithmetic calculations involved in it. As for divergence. We have two kinds of timekeeping. “Calendrical timekeeping” which will always get fixed to be close enough to the solar year that no one has a problem with it, and “Chronological timekeeping” which is basically the science of keeping a track of how many seconds have passed between arbitrary moments in time. All Calendrical timekeeping have for decades now been built on top of TAI and the science of Chronological timekeeping where metrologists have kept fastidious watch over atomic clocks and matched the beating of their resonating frequencies to the astronomical record keeping to allow ever more precise astronomy and the byproduct of this effort have been precise records of how long in scientifically precise seconds each day has been, and from these records we know we have to occasionally “add” a second if we want the “human time” to stay within 1 second of the astronomical time. Consequently we can simply decide we are happy with more or less drift. One second is small enough we can kinda just deal with it, but imagine having a leap minute every hundred years? Coordinate that mess, or how about a leap hour once a millennium? It’s trivial for people we don’t really time anything as humans faster than a second, so if we skip one it’s pretty much ok… it’s categorically on an issue for computers… which should never have used UTC and should have always used TAI because TAI doesn’t skip a second and so the fix would be “a fixed lookup table or a single if branch based on the date and the number of integers to add when doing the integer representation to human representation mathematics before updating the clock on your screen.
- fanf2 3y ago
  Most of the people responsible for implementing leap seconds want to get rid of them too. The international bureaucratic wheels are grinding slowly towards abolition: should be more successful this time than the previous attempt ~15-20 years ago.
jdougan 3y ago
The International Earth Rotation Service is possibly my favorite name for an international bureaucracy. It give me visions of a Giant Control Lever extending deep into the Earth, with the labels Faster and Slower.
- twic 3y ago
  People say money makes the world go round. False. The International Earth Rotation Service makes the world go round.
- Avshalom 3y ago
  You can actually slow down or speed up the planet's rotation with a big switch. |_ open switch, slower __ closed switch faster You can also do it yourself by standing up or laying down
  - oh_sigh 3y ago
    I wonder how big the switch would need to be to be able to transmit info via the rotational speed as hest we can measure it.
  - gshubert17 3y ago
    What happened to the rotation rate around the beginning of 2019, to cause the big change in the slope of the UT1-UTC line (https://crf.usno.navy.mil/ut1-utc https://crf.usno.navy.mil/ut1-utc)? After adding 5 leap seconds in 11 years, no leap seconds have been added or subtracted since the end of 2016.
    - techdragon 3y ago
      Its probably not the only component... but a fun fact is that the Earth's rotation is affected by the average equatorial ocean temperatures, (anyone seen the ocean temperature charts this year... something something ships and sulfur dioxide accidental geoengineering that we stopped doing) warm ocean water displaces slightly more volumetrically and thus by way of its lower density, affects the spinning mass balance of the Earth like a ice skater curling in their fingers rather than their whole arms while spinning like a top, the effect is there... just so very subtle.
fanf2 3y ago
The IERS web site says the EOC is at the Paris Observatory, but much of the data (such as Bulletin A) comes from the Rapid Service/Prediction Centre at the USNO.
throw0101b 3y ago
Someone submitted a 'story' for the IERS that's getting some votes: * https://news.ycombinator.com/item?id=37777116 https://news.ycombinator.com/item?id=37777116

Gooblebrai 3y ago

What other two?

beerandt 3y ago

While the Navy's time keeping mission is fascinating on its own (and itself was(is) a prerequisite for navigational abilities) the understated 'read-between-the-lines' reason the Navy looks "outward" is because that's how it points the nukes.

robviren 3y ago

I love stuff like this so much. You take something as seemingly complex as time or weight and it ends up boiling down to like a handful of people diligently crunching numbers or a hunk of exactly 1 KG of platinum sitting in the basement of some French lab. Dispelling the "magic" behind these things utterly fascinates me.

fanf2 3y ago

That isn’t quite right. UTC was originally (early 1960s) coordinated between the British and Americans. This was related to their existing collaborations in time and navigation. The definition of the atomic second was established in 1955-1958 by a collaboration between NPL (London) who had the first good atomic clock, and the USNO who were good at the astronometric work to establish the ephemeris second. The USNO and the Greenwich observatory also prepared the Astronomical Almanac together. Later on, as other countries wanted to use the same atomic timescale, the BIH (bureau international de l’heure, based at the Paris observatory) took over. More recently, the BIH was split. The part responsible for atomic time moved to the BIPM (bureau international des poids et mesures, in Sévres just outside Paris) who are responsible for the definition of the second, so it makes sense for them to be responsible for its realisation as well. They maintain atomic time based on contributions from many atomic clocks in many time labs around the world. The astronomy parts of the BIH became the IERS (international earth rotation service), still based at the Paris Observatory. However, a significant part of their practical scientific work is carried out by the USNO. For instance IERS Bulletin A is sent out each week by the USNO. Earth orientation is needed for the GPS as well as for leap seconds.