Follow Slashdot stories on Twitter

 


Forgot your password?
Close
typodupeerror
×
News

The Future of Time: UTC and the Leap Second 235

Posted by CmdrTaco from the good-bye-gold-standard dept.
rlseaman writes "UTC ("Coordinated Universal Time") is very close to being redefined to no longer track Earth rotation. Clocks everywhere — on your wall, wrist, phone or computer — would stop keeping Solar time. 'American Scientist' says: 'Before atomic timekeeping, clocks were set to the skies. But starting in 1972, radio signals began broadcasting atomic seconds and leap seconds have occasionally been added to that stream of atomic seconds to keep the signals synchronized with the actual rotation of Earth. Such adjustments were considered necessary because Earth's rotation is less regular than atomic timekeeping. In January 2012, a United Nations-affiliated organization could permanently break this link by redefining Coordinated Universal Time.'"
This discussion has been archived. No new comments can be posted.

The Future of Time: UTC and the Leap Second More

The Future of Time: UTC and the Leap Second

Comments Filter:

  • Copypasta (Score:2, Insightful)

    by Gothmolly ( 148874 )

    Taco, all you did is quote the article summary. I can spin up an RSS reader to do that.

  • PDF version (Score:5, Informative)

    by KenAndCorey ( 581410 ) on Tuesday June 28, 2011 @12:26PM (#36598840)
    Here's the full PDF version [arxiv.org].

  • Metric Time (Score:2, Interesting)

    by Normal Dan ( 1053064 )
    As long as we're redoing time I say we convert it to the metric system. This was hard to do before because we kept trying to keep time in line with the rotation/orbit of the earth. But if all that's going out the window, let's just divide everything up into units of 10 and be done with it.

    • 10 is an arbitrary base and works poorly for time. Earth time works very well in Base-12, which is what we have now.

      If you want to think of the children, the Egyptians and Babylonians taught their children to count on the knuckles of their four non-thumb fingers. The 10-finger-number system is just an unfortunate thing that came along with arabic numerals, which are very useful.

      I saw we adopt something from the UNICODE set to mean eleven and twelve. Say, they're not 1-teen and 2-teen, are they?

      • 10 is an arbitrary base and works poorly for time. Earth time works very well in Base-12, which is what we have now.

        Why would it work more poorly for time than for distance or anything else?

        Although one thing I do find amusing about the whole metric vs. traditional units is that one of the primary arguments for moving to metric units is that it makes conversion between units easier. The only problem is that about the only units that I convert between on a regular basis is ... time, which is not handled in

        • The ease of conversion is more when converting compound units. A newton is a kg m/second^2. A Joule is a Newton applied over a meter = kg m^2/second^2. A Watt is a Joule used every second = kg m^2/second^3.

          American units have the pound, which is a slug foot /second^2. Except no one uses the slug, so it has to be pound-force = pound mass * 32.2 ft/second ^2. Energy? Sometimes they use foot-pound which is easy enough, but other areas we use kilowatt-hour, or BTU (defined from the heat capacity of water). Powe

          • The ease of conversion is more when converting compound units. A newton is a kg m/second^2. A Joule is a Newton applied over a meter = kg m^2/second^2. A Watt is a Joule used every second = kg m^2/second^3

            Oh, I understand the principle. The thing is that I haven't had any reason to do those types of unit conversions since I got out of school, and I'm willing to bet that goes for almost everyone else. Those who do (scientists and engineers, mostly), ought to be using metric in their work, no argument there

            • Hate to tell you, but metric is the 'customary' system pretty much everywhere but the USA and Libya.

      • I'm one of the biggest advocates for the base 12 (or 16) number system, but if we have to keep with base 10 for now, then it would obviously make sense to have time as base 10 also to keep things standard.

      • I agree, 10 doesn't work so well, but 1 works great for time if you consider one rotation of Earth. At .500000 Greenwich would be through one half rotation. If you told someone to meet up in 2 and a half days you know how many time units it is already... (hint: 2.5)

        I actually wrote a JavaScript clock for my desktop that uses UTC time converted to decimal for Earth rotations.

        I will disagree that 12 is a reasonable number though. Sixteen I can see, but twelve does not evenly halve out to a round number. 1

        • Re: (Score:2)

          by Phleg ( 523632 )
          Being a power of two is not of as much use as is being an even multiple of 2, 3, 4, and 6, giving you many possible factors to divide evenly by.

          • But what's the point of dividing a day into three or six parts? I can see 2 and 4 (half and quarter day) but I don't know many people who think in third or sixth of days.

      • "We know that the human race is not sufficiently advanced because they have not yet converted to a base-6 system of enumeration."

      • Now that you mention it, I've always considered base-2 or 16 to be rather useful for dealing with computers. As long as we're rearranging things, let's pick a base and put everything in it. I say 16. We can learn to count on our non-thumb knuckles and toes. We'll be a race of super geniuses, etc.

    • Re:Metric Time (Score:5, Informative)

      by gstrickler ( 920733 ) on Tuesday June 28, 2011 @01:42PM (#36600598)

      The metric system is originally based upon an earth derived measurement called the meter. 1m ~ 1/10,000 the distance from the equator to the poles, 1g = the weight of 1cc of pure water at STP, etc. That all the measurements are base 10 is not what makes it "metric", it's that they're derived from the (originally) earth centric meter. Our time system is also derived from earth centric measurements, called day and year.

      Base 10 time would be a huge adjustment for society. While using a 100,000 "MetSec" day and a 100 "MetSec" "MetMin" would produce units fairly close to the existing second and minute measurements, a "MetHour" would be much longer or much shorter than an hour, either 14.4 minutes (100 MetHours/day), or 2.4 hours (10 MetHours/day). And that doesn't do anything to address the leap second issue, nor does it alter the ~ 365.25 MSD year.

      The bottom line is that as long as we maintain the concept of a day and year and all the associated stuff (seasons, equinoxes, solstices, etc.), all of which are critical to agriculture and survival, there has been no system of time keeping proposed that is significantly better than what we have. The universe is not going to arbitrarily adapt it's cycles to make it easy for our minds and computers to keep track of time.

      And that's without considering relativistic time dilation. While most people never have to worry about time dilation effects, the atomic clocks that create UT1 and GPS satellites have to compensate for relativistic differences caused by differences in local gravity and speed, both of which are affected by altitude.

      Perhaps Douglas Adams said it best, "Time is an illusion, lunchtime doubly so."

  • <Kirk Voice> Stardate.....65500...My...solar TIME, clock...seems to be...malFUNCTIONing...perhaps Coordinated....UniversalTime...is finally...UPON us. <\Kirk Voice>

  • Relativistic Reference Frames? (Score:4, Interesting)

    by bill_mcgonigle ( 4333 ) * on Tuesday June 28, 2011 @12:31PM (#36598940) Homepage Journal

    In 2012, a new definition of time that is only relative to the Earth's reference frame falls short.

  • Even if we don't manage to exterminate ourselves in the interim we won't be getting off this rock in any meaningful way for several more generations on even the most optimistic forecasts. What is the point of divorcing UTC from humanity's relationship to our day to day on earth?

    • Re: (Score:2)

      by tom17 ( 659054 )

      So what we need to do is leave it as is for now and when we start real space travel, we can have Space Time.

      Space Time, a fusion between the concepts of space and time, brought forward into one four dimensional continuum. Yeah man. I love that shit right there.

  • While we're at it (Score:5, Insightful)

    by vegge ( 184413 ) on Tuesday June 28, 2011 @12:35PM (#36599006)
    ... could we also get rid of Daylight Savings Time?

    • Re: (Score:2)

      by Pope ( 17780 )
      No thanks. PS. it's Daylight Saving Time, there's no "s".

    • Of course not. Studies utilizing questionable methodologies say it saves energy.

      Besides, not having to run in circles every time Congress decides to twiddle the dates would put people out of work and that's the last thing we need in this economy.

      • Re: (Score:3)

        by epine ( 68316 )

        Besides, not having to run in circles every time Congress decides to twiddle the dates would put people out of work and that's the last thing we need in this economy.

        Congratulations, you've just won a contract valued at 4 weeks of "running in circles" paying $100 per hour next time Congress twiddles the dates. This will spare you having to take out a second mortgage for the expanded deck and hot tub. Hope your spouse is the patient type and accepts that you'll be in good coin any day now for the big splur

    • Re: (Score:2)

      by antdude ( 79039 )

      No, leave the daylight savings time. Get rid of the standard one. I like the extra daylight in the evening hours. ;)

  • How long is year anyway? (Score:4, Informative)

    by scorp1us ( 235526 ) on Tuesday June 28, 2011 @12:38PM (#36599042) Journal

    We say 365 days.
    We observe 365.25.
    The tropical year (equinoxes+solstices) is closer to 365 solar days, 5 hours 49 minutes 19 seconds
    The sidereal year is 1.0000385 tropical years (365.256363004 ) (20m24.5128s longer than tropical year)

    So may times...

    • Re: (Score:2)

      by blair1q ( 305137 )

      A year is a year long.

      Your numerical estimates of it are conveniences for your daily use, but, as you can see, can only be reconciled to the year by defining context and accounting for variability.

      If UTC stops adjusting for variability, then we'll just go back to using GMT as our human-readable clock standard timebase.

  • Aw, jeezus (Score:3)

    by jra ( 5600 ) on Tuesday June 28, 2011 @12:39PM (#36599064)

    This has been *progressing*?

    This is possibly the stupidest idea in history. Their stated goal: taking complexity out of time handling code -- *cannot happen*: it will *still* have to account for all the years we did this.

    And it will break *lots* of stuff.

    • Re: (Score:2)

      by spitzak ( 4019 )

      It will have to account for all the years this was done, but there will be no unpredictable changes in the future. The difference between atomic time and current time will be a constant from now on. This is a lot easier, because you can write a self-contained program to do 100% of the conversion right now, rather than having to write a program that can update the conversion from an outside source.

  • You have no idea how much code I'll have to look through to make sure that it doesn't assume |UTC-UT1| < 1.

    • Re: (Score:2)

      by blair1q ( 305137 )

      i would guess all of it does, because we've always assumed UTC=UTC=UTC=UTC.

      luckily, the fix could be very simple.

      you just point your time server for those systems at a master time server that is still giving out UTC, instead of at whatever standards' organization's time server that's been changed over to the new standard.

      i suspect you'll be able to find (or construct) such UTC servers indefinitely.

      the math will then be done at one place, and everywhere else can just go on as their original specifications, u

      • Re: (Score:2)

        by SETIGuy ( 33768 ) *
        When you are trying to time light arrival time from astronomical objects to the microsecond, or if want to know where something is in the sky to arcsecond (or better) accuracy, what time it is, where the earth is, and how its oriented become very important questions. Depending upon where you live, your house might be moving at a quarter mile a second (relative to the center of the earth). The less well I know the time or the orientation of the earth, the larger the asteroid I need to use to ensure that I

  • Oh... (Score:2)

    by jra ( 5600 )

    and TFA is apparently only available to Sigma Xi members. Great work there, Slashdot editor.

  • Wall clocks (Score:5, Insightful)

    by bugs2squash ( 1132591 ) on Tuesday June 28, 2011 @12:53PM (#36599366)
    will simply ignore UTC and continue to show the time based on the earth's rotation. All this means is that UTC loses any small shred of relevance that it once may have had to the common man. So go ahead, redefine UTC and we can all just go back to using GMT for our reports, syslog messages, traps etc. that all have far more to do with the time as experienced by users than the time as experienced by a cesium atom. I expect that soon after the decision is made someone will start gmt.pool.ntp.org and utc.pool.ntp.org and we'll have a choice.
    • Wall clocks don't know anything about the earth's rotation. They're typically driven by the mains frequency, which is in the process of being disconnected form 60 Hz in the USA. And GMT is no solution - it didn't handle the earth's rotation rate change very gracefully. Do you want the version that changed the definition of a second based on the last few years' observed day lengths?
      • In general, people will want clocks that pretty much point to noon at the sun's zenith where they live, where it gets dark at around the wall-clock time they remember as being bed time and where the alarm goes off just slightly before the time of day that they wish it would. These are all synced to the Earth's motion and anyway...
        • Powerline frequency stability isn't what it once was, and being allowed to drift more recently, especially outside of Texas (I don't know why Texas...)
        • Wall clocks (and by extensio

        • In general, people will want clocks that pretty much point to the minute at which the next television show will appear. They should therefore synced instead to the broadcast signal time. Keeping your DVR and wall clock in sync with the broadcasting stations reduces the possibility of DVR drift, where you miss the first or last few seconds of a show, or reality drift where you turn the tv on a few seconds late.

        • Re: (Score:2)

          by Arlet ( 29997 )

          In general, people will want clocks that pretty much point to noon at the sun's zenith where they live

          But it doesn't have to be at the nearest second. Where I live, the sun reached zenith at 1:43pm today. Even if we stop counting the leap seconds, it will take long before that number reaches 2pm. At that time, we can start considering adding a leap hour, or something similar.

    • Re: (Score:2)

      by blair1q ( 305137 )

      I will ignore both and continue to claim "my watch is a little fast" when showing up my customary 160+-5 seconds late for meetings.

  • What would be the point of UTC, then? (Score:4, Informative)

    by inglorion_on_the_net ( 1965514 ) on Tuesday June 28, 2011 @01:04PM (#36599646) Homepage

    If UTC would be redefined to no longer be adjusted to Earth's rotation, then what would be the point of having UTC at all? We already have a time scale that counts seconds without adjusting to Earth's rotation: TAI [wikipedia.org]

    • Re: (Score:2)

      by radtea ( 464814 )

      If UTC would be redefined to no longer be adjusted to Earth's rotation, then what would be the point of having UTC at all? We already have a time scale that counts seconds without adjusting to Earth's rotation: TAI [wikipedia.org]

      Yeah, this really makes no sense. We will always have the need for a time that will tell us when the Sun will rise and whatnot, and that time will always need leap seconds or something like them.

      A better solution might be to redefine UTC to be independent of any notion of "seconds" as a datum. Give each UTC year a TAI start-second (floating point, of course) as a datum and be done with it, rather than counting UTC seconds from a one datum, TAI seconds from another datum, and adding an adjustment between t

    • Re: (Score:2)

      by blair1q ( 305137 )

      It would be a good timebase for when we're not on Earth. I.e., it would become "universal".

      So, while I think changing what UTC means is pretty dumb, now, I think that if we had /. back when they decided to make the first adjustment to it to keep to the Earth's clock that I would have thought that changing what UTC meant then was really fucking dumb. Since I think now that's what I think having done it then was.

      So here's my solution: Leave UTC alone, don't make anyone have to change anything they've based

  • three pictures to explain it, and a solution (Score:2, Informative)

    by Anonymous Coward

    The situation can be explained in three pictures [ucolick.org].

    Using already-deployed code, here is one way to solve the problems [ucolick.org].

  • The old system will end and all new one will start up at the same time with big changes.

  • and my clock that syncs to NIST's WWVb transmitter? i seen no mention of it in the PDF

  • itsabouttime (Score:3)

    by miruku ( 642921 ) on Tuesday June 28, 2011 @01:54PM (#36600840) Homepage

    Oh groan, best use of that tag on /. so far.

  • I know that we can keep time much more accurate using atomic time.
    My questions is, why on earth would we want to? I mean that literally. We live on earth. The earths travel rotation around the sun and the rotation the earth does each day is what is relevant to our lives.
    We plant our crops according to the seasons. We wake up because the sun shines. Why should our system of time directly reflect the way we live our lives?

    • Re: (Score:2)

      by blair1q ( 305137 )

      The best use of atomic timebases is the same as the best use of clocks used to be: navigation.

      We started out needing accurate clocks so we could tell from the angles of celestial bodies and the horizon where we were on the planet relative to home, to within a few hundred meters.

      Now we need accurate atomic timebases to measure the frequencies of radio waves from satellites to triangulate between them so we can tell where we are on the planet even if we're at home, to within a few meters.

  • If you want to read it for yourself: http://arxiv.org/pdf/1106.3141v1 [arxiv.org]

    Quoting the last line: "Will deliberations at the ITU-R Radiocommunication Assembly in January 2012 resolve or cloud these issues?"

    This is a committee to review the standard. Nothing is going to change without proposals. Those come long AFTER the review. Then there's the discussion process. Eventually it may make it to being a standard. Then people have time to implement it.

    Cheers,

    Ehud

    • Re: (Score:2)

      by blair1q ( 305137 )

      Why do we need them?

      They should submit the standard to us and we'll figure out whether anything needs to be done.

Slashdot Top Deals

Math is like love -- a simple idea but it can get complicated. -- R. Drabek

Close