4 ms·

Nations Convene to Decide the Fate of a Second

28 points by NaOH 15y ago

deleted 15y ago
[deleted]
jaylevitt 15y ago
The author sounds knowledgeable, but the reference to Y2K as an overreaction makes me think he hasn't a clue. Kenneth, boychik... how much effort do you think it took to make sure Y2K didn't become a memorable problem?
- deleted 15y ago
  [deleted]
- silon3 15y ago
  We'll have to reset everything at Y10K anyway.
marshray 15y ago
Astronomical observations at small resolutions of time already have to compensate for so many variables that the current leap second system does not help them any. Seriously, look at the formulae and data collected by these guys http://www.iers.org/ http://www.iers.org/ and then say "astronomers need leap seconds to point their telescopes". More likely, somewhere some budget for astronomers will be reduced by the move to a terrestrial source of time.
luser001 15y ago
Hmm, the proposal to do away with the leap second seems yet another instance of humanity's practice of taking decisions that are expedient in the short term but will create problems in the long term (sun rises at noon in a few thousand years?!) Every computer in the past several years I've installed (Windows, Mac, Linux) has had NTP enabled. Almost every cell phone ships with "set time from network" enabled. Wristwatches sales are way down => few people set their watches manually. Keep the leap second! :)
- deleted 15y ago
  [deleted]
- 3pt14159 15y ago
  Nope. Let's get rid of this horrible date-time system we have. I can't wait for gataca or the singularity to take away these crazy time and productivity wasters.
- sskates 15y ago
  I think not being able to guarantee that there always 7200 seconds between 11:00pm and 1:00am the next day could be a worse problem than having the sun rise at noon in a few thousand years.
  - crististm 15y ago
    why is this different from leap years?
    - dodedo 15y ago
      Leap years are defined by a known algorithm: If the year is evenly divisible by 4, then it's a leap year, unless it's divisible by 100, unless it's divisible by 400. This defines all future leap years. Because of this, we /do/ know how much time will be between two particular dates. Leap years can be calculated in advance as they represent a well-known, fixed skew between the gregorian calendar and the actual calendar. Contrast this with leap seconds, which represent a variable skew and cannot be predicted by algorithm. Leap seconds are determined by measurement of the solar cycle and are merely announced at 6 month intervals. Because of this we cannot use solar time with seconds-granularity more than 6 months into the future, and a table of past leap-seconds is needed to accurately calculate time in the past. Worth noting: POSIX time functions do none of this for you. There is another system of time, TAI, which is used for scientific measurements which rely on seconds-granularity at arbitrary intervals. TAI is skewed from solar time and will eventually not match the 24 hour solar cycle.
- Dylan16807 15y ago
  It seems to me that leap minutes would perform no worse and cause a lot less pain from rarity.
dodedo 15y ago
"But Britain, along with Canada and China, would like to keep the current keeping system, arguing that, in the 40 years that leap seconds have been gracefully inserted in our midst — most recently in 2008 — there have been no problems to speak of, and the worriers have greatly exaggerated the potential for havoc. Remember Y2K?" No problems? He must not be aware of the 2008 adjtimex() bug in the linux kernel: https://lkml.org/lkml/2009/1/2/389 https://lkml.org/lkml/2009/1/2/389 This bug brought down nearly 100k systems for my employer at midnight UTC, worldwide, in unison. It was not a fun evening.
wl 15y ago
I'm wondering why people are trying to get the leap second removed from UTC. If people have situations where leap seconds are problematic, why not just switch to TAI which already doesn't have leap seconds?
- bdonlan 15y ago
  It's because too many things are defined in terms of UTC; if you start saying, "Okay, let's start using TAI from now on.", now you have the complexity of trying to remember whether you're supposed to use TAI or UTC for this particular protocol and/or data format, so in practice people will stick with UTC there. On the other hand, removing leap seconds from UTC is trivial - they're inserted manually anyway, so you just stop doing it.
d0mine 15y ago
Epoch time vs. time of day http://www.ucolick.org/~sla/leapsecs/epochtime.html http://www.ucolick.org/~sla/leapsecs/epochtime.html
learc83 15y ago
Why can't we just add a leap minute every century, or a leap ten minutes every millennium?
Someone 15y ago
'required' (if only for the sentence starting with "As a time-nut, a small and crazy fraternity") reading: http://queue.acm.org/detail.cfm?id=1967009 http://queue.acm.org/detail.cfm?id=1967009
pygy_ 15y ago
Why don't we recalibrate the atomic clocks, that are systematically running late? I assume that the variations in the Earth's rotations are not predictable, and that it is this impossible to do it exactly, but they could be conservatively slowed down in order to increase the delay between leap seconds.
- ars 15y ago
  The earth is slowing down. No matter how you calibrate the clocks, you'll constantly have to change it. At some point the second was accurate to the earth. And in any case the second is very precisely defined based on physical objects (specifically how long it takes an atom of cesium to oscillate a specific number of times). Changing it would ripple through all sorts of things, for example the length of objects would change (or more accurately the number we use to measure the length of an object would be different). The number used to represent the length of an object is based on how far light travels in a certain amount of time. Change that time, you change how far the light traveled, which would then give a new definition for how long a meter is.
  - pygy_ 15y ago
    Then define two types of seconds. * The reference second, used for the metric system definitions and science in general. * The real-life second, based on the rotation of the earth. If you want to keep a Cesium reference for every day time, you can define the second as either 9,192,631,770 or 9,192,631,771 oscillations in a given proportion. X short seconds followed by Y long seconds, with the X/Y ratio decreasing daily. When X becomes 0, increment both numbers and start over.
    - ars 15y ago
      Are you trolling? Joking? A: How exactly do you propose changing the speed of millions of clocks worldwide to match your new second? B: Given that the entire difference is one second every year or so, I guess they could just adjust by one second every once in a while. i.e. you are back where you started.

28 points by NaOH 15y ago

deleted 15y ago

[deleted]

The author sounds knowledgeable, but the reference to Y2K as an overreaction makes me think he hasn't a clue. Kenneth, boychik... how much effort do you think it took to make sure Y2K didn't become a memorable problem?

deleted 15y ago
[deleted]
silon3 15y ago
We'll have to reset everything at Y10K anyway.

marshray 15y ago

Astronomical observations at small resolutions of time already have to compensate for so many variables that the current leap second system does not help them any. Seriously, look at the formulae and data collected by these guys http://www.iers.org/ http://www.iers.org/ and then say "astronomers need leap seconds to point their telescopes". More likely, somewhere some budget for astronomers will be reduced by the move to a terrestrial source of time.

luser001 15y ago

Hmm, the proposal to do away with the leap second seems yet another instance of humanity's practice of taking decisions that are expedient in the short term but will create problems in the long term (sun rises at noon in a few thousand years?!) Every computer in the past several years I've installed (Windows, Mac, Linux) has had NTP enabled. Almost every cell phone ships with "set time from network" enabled. Wristwatches sales are way down => few people set their watches manually. Keep the leap second! :)

deleted 15y ago
[deleted]
3pt14159 15y ago
Nope. Let's get rid of this horrible date-time system we have. I can't wait for gataca or the singularity to take away these crazy time and productivity wasters.
sskates 15y ago
I think not being able to guarantee that there always 7200 seconds between 11:00pm and 1:00am the next day could be a worse problem than having the sun rise at noon in a few thousand years.
- crististm 15y ago
  why is this different from leap years?
  - dodedo 15y ago
    Leap years are defined by a known algorithm: If the year is evenly divisible by 4, then it's a leap year, unless it's divisible by 100, unless it's divisible by 400. This defines all future leap years. Because of this, we /do/ know how much time will be between two particular dates. Leap years can be calculated in advance as they represent a well-known, fixed skew between the gregorian calendar and the actual calendar. Contrast this with leap seconds, which represent a variable skew and cannot be predicted by algorithm. Leap seconds are determined by measurement of the solar cycle and are merely announced at 6 month intervals. Because of this we cannot use solar time with seconds-granularity more than 6 months into the future, and a table of past leap-seconds is needed to accurately calculate time in the past. Worth noting: POSIX time functions do none of this for you. There is another system of time, TAI, which is used for scientific measurements which rely on seconds-granularity at arbitrary intervals. TAI is skewed from solar time and will eventually not match the 24 hour solar cycle.
Dylan16807 15y ago
It seems to me that leap minutes would perform no worse and cause a lot less pain from rarity.

dodedo 15y ago

"But Britain, along with Canada and China, would like to keep the current keeping system, arguing that, in the 40 years that leap seconds have been gracefully inserted in our midst — most recently in 2008 — there have been no problems to speak of, and the worriers have greatly exaggerated the potential for havoc. Remember Y2K?" No problems? He must not be aware of the 2008 adjtimex() bug in the linux kernel: https://lkml.org/lkml/2009/1/2/389 https://lkml.org/lkml/2009/1/2/389 This bug brought down nearly 100k systems for my employer at midnight UTC, worldwide, in unison. It was not a fun evening.

wl 15y ago

I'm wondering why people are trying to get the leap second removed from UTC. If people have situations where leap seconds are problematic, why not just switch to TAI which already doesn't have leap seconds?

bdonlan 15y ago
It's because too many things are defined in terms of UTC; if you start saying, "Okay, let's start using TAI from now on.", now you have the complexity of trying to remember whether you're supposed to use TAI or UTC for this particular protocol and/or data format, so in practice people will stick with UTC there. On the other hand, removing leap seconds from UTC is trivial - they're inserted manually anyway, so you just stop doing it.

d0mine 15y ago

Epoch time vs. time of day http://www.ucolick.org/~sla/leapsecs/epochtime.html http://www.ucolick.org/~sla/leapsecs/epochtime.html

learc83 15y ago

Why can't we just add a leap minute every century, or a leap ten minutes every millennium?

Someone 15y ago

'required' (if only for the sentence starting with "As a time-nut, a small and crazy fraternity") reading: http://queue.acm.org/detail.cfm?id=1967009 http://queue.acm.org/detail.cfm?id=1967009

pygy_ 15y ago

Why don't we recalibrate the atomic clocks, that are systematically running late? I assume that the variations in the Earth's rotations are not predictable, and that it is this impossible to do it exactly, but they could be conservatively slowed down in order to increase the delay between leap seconds.

ars 15y ago
The earth is slowing down. No matter how you calibrate the clocks, you'll constantly have to change it. At some point the second was accurate to the earth. And in any case the second is very precisely defined based on physical objects (specifically how long it takes an atom of cesium to oscillate a specific number of times). Changing it would ripple through all sorts of things, for example the length of objects would change (or more accurately the number we use to measure the length of an object would be different). The number used to represent the length of an object is based on how far light travels in a certain amount of time. Change that time, you change how far the light traveled, which would then give a new definition for how long a meter is.
- pygy_ 15y ago
  Then define two types of seconds. * The reference second, used for the metric system definitions and science in general. * The real-life second, based on the rotation of the earth. If you want to keep a Cesium reference for every day time, you can define the second as either 9,192,631,770 or 9,192,631,771 oscillations in a given proportion. X short seconds followed by Y long seconds, with the X/Y ratio decreasing daily. When X becomes 0, increment both numbers and start over.
  - ars 15y ago
    Are you trolling? Joking? A: How exactly do you propose changing the speed of millions of clocks worldwide to match your new second? B: Given that the entire difference is one second every year or so, I guess they could just adjust by one second every once in a while. i.e. you are back where you started.