6 ms·

In short, yes, the weather, geology, and signicantly, human movement of water via aquifer draining and dam building, as well as glaicial and ice melts, all cont

In short, yes, the weather, geology, and signicantly, human movement of water via aquifer draining and dam building, as well as glaicial and ice melts, all contribute to unpredictable changes in the earths rotational period, as well as the axis of rotation. The models for this are IIRC trigonometric polynomials of fairly low order, so even if we could model the unpredictability perfectly, truncation error would limit our ability to distribute the model at super high accuracy. The existing models are built in to, eg, satellites, so you can't just make them arbitrarily complex. Fun fact: leap seconds will stop being a thing soonish. I think they phase out in 2035, with a delay because Russia needed time to update glonass satellites. (Note: on mobile, this is from memory, details need checking ;))

thewebguyd 3mo ago
> as well as the axis of rotation A frightening fact, the 2011 magnitude 9.0 Tohoku Earthquake shifted the position of the Earth's figure axis about 17 centimeters, making days about 1.8 microseconds shorter.
tialaramex 3mo ago
2035 is the agreed drop dead date. Everybody agreed that "Leap seconds" are a sufficiently bad idea that they should be replaced by 2035. Nobody has agreed how to fix it, and "Just turn them off" isn't technically legal. However, "What if there were Leap hours instead?" is technically legal and of course those hours would happen in the very distant future (likely after our civilisation is gone) so it's functionally identical to "Just turn them off" but without legal problems. Now, I'm English, and England loves this sort of hack. You may have heard that controversial UK politician Nigel Farage "resigned" as a Westminster MP recently and that's not technically true because you can't resign, historically people hated that job and so you can't resign and we never changed that, but what you can do, and everybody does, is get assigned an "Office of profit" in which legally the King is paying you, an MP can't work for the King so you can't be an MP any more. The "Offices of profit" in question aren't real jobs† and don't pay real money, like this "Leap Hour" they'd be a legal fiction. So everybody says you "resigned" but in fact you legally can't do that... † I mean, historically they were real jobs that made sense which is why the King paid somebody to do them, but England is very, very old so they haven't made sense for centuries and serve only as a legal fiction today.
- jeffrallen 3mo ago
  Farage is such an ass, the King should make him feed donkeys or something.
  - tialaramex 3mo ago
    "Vote Count Binface and Bin the Cunt" :D There's a long tradition in the UK of having electoral candidates who don't expect to win but run because it's free publicity in a high profile race. "Count Binface" is a comedian who dresses up as a space alien whose outfit resembles well, having a Bin for a face. The serious political parties told Nigel to fuck off, if he wants to step down and then immediately contest the same seat they wouldn't run against him in this farce, but Binface isn't a serious politician so he is running in that by-election. Nigel wanted to be able to do this whole thing about how the establishment is rotten and he (Wealthy public schoolboy who keeps lying to people and doesn't bother going to Parliament even though he was elected to do so) is a true man of the people and can put things right. It got him this far in life. But with the other candidate on your ballot being a space alien it's obvious which of these options is really "the establishment" and it's not the guy whose policies include "Building at least one house†" and who says he comes from a different planet... † British political parties often insist they will build lots of housing because that's popular with voters. But, in practice they don't tend to really deliver because the various groups lobby not to actually build. So "at least one house" is a joke about this phenomenon, while conveniently also being technically possible, Binface could just build a house, that's a thing you can do.
    - f4c39012 3mo ago
      I think it's more than publicity. Anyone can stand as a candidate, and anyone can vote for them. Money and connections and establishment and everything else don't matter, all candidates are equal on that stage. It's both weird and to be admired.
      - duskwuff 3mo ago
        And a bit of "if Farage really wants the seat, he can fight for it". There's something unsporting about letting him win unopposed.
lloeki 3mo ago
> Russia needed time to update glassnoss satellites GLONASS maybe? or really glasnost era satellites?
- _alternator_ 3mo ago
  Glonass is correct. On mobile, thanks for the correction.
Xenoamorphous 3mo ago
A butterfly flaps its wings in Tokyo and we lose a leap second.
N19PEDL2 3mo ago
> because Russia needed time to update glonass satellites. Why is this? As leap seconds don’t occur on a regular frequency, I assume they are not hardcoded on the software or hardware on board, but the control centre uploads them on the satellites enough in advance once they have been scheduled. So why can’t the control centre just stop sending those updates?
- _alternator_ 3mo ago
  My understanding the problem is that GLONASS is aware of leap seconds at all. It sends messages in UTC, which has this leap second funny business. GPS uses a special "GPS time" (sometimes abbreviated UT) that doesn't have a leap second. For further confusion, the leap second ensures that UTC is never more than 0.9 seconds off of mean solar time, aka UT1. This type of assumption that was made early in a massive software and hardware project that's now been ossified for ~50 years is going to be hard to change.
jvanderbot 3mo ago
I prefer ephemeris time
Dylan16807 3mo ago
> The models for this are IIRC trigonometric polynomials of fairly low order, so even if we could model the unpredictability perfectly, truncation error would limit our ability to distribute the model at super high accuracy. The existing models are built in to, eg, satellites, so you can't just make them arbitrarily complex. What are the satellites doing with the models? They're not deciding leap seconds on their own, I hope. So I don't see why the leap second decision would be locked to low accuracy. Also I would expect doubling the precision to give you a 3-4x slowdown on the math or adding orders to have less effect, and the amount of available computation spent on those models to be like a tenth of a percent at most, so the extra cycles wouldn't be an issue. What am I missing here? To me it seems like unpredictability is the only real issue.
bloppe 3mo ago
Phasing out leap seconds is such a crack pot idea. Read the resolution [1]. The conclusion hinges entirely on accepting the immutability of these 2 premises: recalling that the CGPM at its 26th meeting (2018) - stated that UTC is the only recommended time scale for international reference and the basis of civil time in most countries, - recommended all relevant unions and organizations to work together to develop a common understanding on the realization and dissemination of reference time scales with a view to considering the present limitation on the maximum magnitude of UT1 - UTC to meet the needs of the current and future user communities, I accept all the other premises from the resolution, but then the obvious conclusion should be to just recommend TAI instead of UTC for any application that could be disrupted by leap seconds, instead of butchering UTC and turning it into just a worse version of TAI. [1]: https://www.bipm.org/en/cgpm-2022/resolution-4 https://www.bipm.org/en/cgpm-2022/resolution-4

thewebguyd 3mo ago

> as well as the axis of rotation A frightening fact, the 2011 magnitude 9.0 Tohoku Earthquake shifted the position of the Earth's figure axis about 17 centimeters, making days about 1.8 microseconds shorter.

tialaramex 3mo ago

2035 is the agreed drop dead date. Everybody agreed that "Leap seconds" are a sufficiently bad idea that they should be replaced by 2035. Nobody has agreed how to fix it, and "Just turn them off" isn't technically legal. However, "What if there were Leap hours instead?" is technically legal and of course those hours would happen in the very distant future (likely after our civilisation is gone) so it's functionally identical to "Just turn them off" but without legal problems. Now, I'm English, and England loves this sort of hack. You may have heard that controversial UK politician Nigel Farage "resigned" as a Westminster MP recently and that's not technically true because you can't resign, historically people hated that job and so you can't resign and we never changed that, but what you can do, and everybody does, is get assigned an "Office of profit" in which legally the King is paying you, an MP can't work for the King so you can't be an MP any more. The "Offices of profit" in question aren't real jobs† and don't pay real money, like this "Leap Hour" they'd be a legal fiction. So everybody says you "resigned" but in fact you legally can't do that... † I mean, historically they were real jobs that made sense which is why the King paid somebody to do them, but England is very, very old so they haven't made sense for centuries and serve only as a legal fiction today.

jeffrallen 3mo ago
Farage is such an ass, the King should make him feed donkeys or something.
- tialaramex 3mo ago
  "Vote Count Binface and Bin the Cunt" :D There's a long tradition in the UK of having electoral candidates who don't expect to win but run because it's free publicity in a high profile race. "Count Binface" is a comedian who dresses up as a space alien whose outfit resembles well, having a Bin for a face. The serious political parties told Nigel to fuck off, if he wants to step down and then immediately contest the same seat they wouldn't run against him in this farce, but Binface isn't a serious politician so he is running in that by-election. Nigel wanted to be able to do this whole thing about how the establishment is rotten and he (Wealthy public schoolboy who keeps lying to people and doesn't bother going to Parliament even though he was elected to do so) is a true man of the people and can put things right. It got him this far in life. But with the other candidate on your ballot being a space alien it's obvious which of these options is really "the establishment" and it's not the guy whose policies include "Building at least one house†" and who says he comes from a different planet... † British political parties often insist they will build lots of housing because that's popular with voters. But, in practice they don't tend to really deliver because the various groups lobby not to actually build. So "at least one house" is a joke about this phenomenon, while conveniently also being technically possible, Binface could just build a house, that's a thing you can do.
  - f4c39012 3mo ago
    I think it's more than publicity. Anyone can stand as a candidate, and anyone can vote for them. Money and connections and establishment and everything else don't matter, all candidates are equal on that stage. It's both weird and to be admired.
    - duskwuff 3mo ago
      And a bit of "if Farage really wants the seat, he can fight for it". There's something unsporting about letting him win unopposed.

lloeki 3mo ago

> Russia needed time to update glassnoss satellites GLONASS maybe? or really glasnost era satellites?

_alternator_ 3mo ago
Glonass is correct. On mobile, thanks for the correction.

Xenoamorphous 3mo ago

A butterfly flaps its wings in Tokyo and we lose a leap second.

N19PEDL2 3mo ago

> because Russia needed time to update glonass satellites. Why is this? As leap seconds don’t occur on a regular frequency, I assume they are not hardcoded on the software or hardware on board, but the control centre uploads them on the satellites enough in advance once they have been scheduled. So why can’t the control centre just stop sending those updates?

_alternator_ 3mo ago
My understanding the problem is that GLONASS is aware of leap seconds at all. It sends messages in UTC, which has this leap second funny business. GPS uses a special "GPS time" (sometimes abbreviated UT) that doesn't have a leap second. For further confusion, the leap second ensures that UTC is never more than 0.9 seconds off of mean solar time, aka UT1. This type of assumption that was made early in a massive software and hardware project that's now been ossified for ~50 years is going to be hard to change.

jvanderbot 3mo ago

I prefer ephemeris time

Dylan16807 3mo ago

> The models for this are IIRC trigonometric polynomials of fairly low order, so even if we could model the unpredictability perfectly, truncation error would limit our ability to distribute the model at super high accuracy. The existing models are built in to, eg, satellites, so you can't just make them arbitrarily complex. What are the satellites doing with the models? They're not deciding leap seconds on their own, I hope. So I don't see why the leap second decision would be locked to low accuracy. Also I would expect doubling the precision to give you a 3-4x slowdown on the math or adding orders to have less effect, and the amount of available computation spent on those models to be like a tenth of a percent at most, so the extra cycles wouldn't be an issue. What am I missing here? To me it seems like unpredictability is the only real issue.

bloppe 3mo ago

Phasing out leap seconds is such a crack pot idea. Read the resolution [1]. The conclusion hinges entirely on accepting the immutability of these 2 premises: recalling that the CGPM at its 26th meeting (2018) - stated that UTC is the only recommended time scale for international reference and the basis of civil time in most countries, - recommended all relevant unions and organizations to work together to develop a common understanding on the realization and dissemination of reference time scales with a view to considering the present limitation on the maximum magnitude of UT1 - UTC to meet the needs of the current and future user communities, I accept all the other premises from the resolution, but then the obvious conclusion should be to just recommend TAI instead of UTC for any application that could be disrupted by leap seconds, instead of butchering UTC and turning it into just a worse version of TAI. [1]: https://www.bipm.org/en/cgpm-2022/resolution-4 https://www.bipm.org/en/cgpm-2022/resolution-4