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Playing With Atomic Clocks At Home 167

Posted by kdawson from the as-i-was-walking-down-the-street-one-day dept.
Wired is running a profile of the Time Nuts, a small group of people who buy surplus precision time equipment — cesium clocks for example — on eBay and keep really accurate time, because they can. The article quotes Tom Van Baak, who has outfitted a time lab superior to those of many small countries: "If you have one clock... you are peaceful and have no worries. If you have two clocks... you start asking, 'What time is it, really?'"
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Playing With Atomic Clocks At Home More

Playing With Atomic Clocks At Home

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  • Clearly.... (Score:5, Funny)

    by Smidge204 ( 605297 ) on Tuesday December 11, 2007 @08:02AM (#21654265) Journal
    ...Some people have too much time on their hands.

    =Smidge=

    • Re:Clearly.... (Score:5, Funny)

      by Kranfer ( 620510 ) on Tuesday December 11, 2007 @08:18AM (#21654403) Homepage Journal
      This is no time to argue about time, we don't have the time!

    • Re: (Score:2, Funny)

      by Foundryman ( 306698 )
      and "it's ticking away with my sanity...."

    • Please read the article (Score:5, Funny)

      by fishdan ( 569872 ) on Tuesday December 11, 2007 @08:52AM (#21654731) Homepage Journal

      Your missing out if you only skimmed the article. Make sure you find this gem:

      When the family returned to the suburbs two days later, the cesium clocks were off by the precise amount relativity predicted. He and his family had lived just a little more life than the neighbors.

      An amazing PROOF that time is actually affected by gravity. We still know so little (ahem) relatively about time in physics, that seeing evidence of it being manipulated in this manner is awesome. will there be giant contained gravity wells in ambulances to slow time while patients are rushed to the hospital? Will I be slowing down time so I can get First Post AND spell check? The possibilities are endless!

      • Re: (Score:2, Funny)

        by Anonymous Coward
        >>Will I be slowing down time so I can get First Post AND spell check?

        I'll give you benefit of the doubt that you put that line in AND then deliberately misspelt the first word in your post. So assuming that -- bravo! You rarely see that sort of self-aware irony.

        You're totally right though about the relativity stuff. Amazing

      • Re:Please read the article (Score:4, Informative)

        by brunes69 ( 86786 ) <slashdot@nOSpam.keirstead.org> on Tuesday December 11, 2007 @09:20AM (#21655023)
        You do know that they proved this like 60 years ago right, when the first Atomic clocks were produced.... In addition there is an atomic clock on the shuttle. The time difference between it and it's perfectly synchronized counterpart on earth is very visible.

        • Re:Please read the article (Score:4, Insightful)

          by sg3000 ( 87992 ) * <(sg_public) (at) (mac.com)> on Tuesday December 11, 2007 @10:45AM (#21656099)
          > You do know that they proved this like 60 years ago right

          Yeah, but what made it cool was that the experiment could be repeated by a regular guy with surplus stuff from Ebay.

          "If you have one clock ... you are peaceful and have no worries," says Van Baak... "If you have two clocks ... you start asking, 'What time is it, really?'"

          Well, maybe not a regular guy, but you get the idea.

      • The real reason (Score:5, Funny)

        by jgoemat ( 565882 ) on Tuesday December 11, 2007 @09:50AM (#21655345)
        Isn't it obvious? It wasn't relativity, the family lived an extra 22 milliseconds because they drove up a mountain and were closer to God. That's the only logical solution, I can't see this "gravity" you speak of. Every time someone has a problem with time physicists think they can solve it just by throwing a few nanoseconds at it. Ridiculous...

        • Re:The real reason (Score:5, Informative)

          by timeOday ( 582209 ) on Tuesday December 11, 2007 @10:31AM (#21655897)

          Isn't it obvious? It wasn't relativity, the family lived an extra 22 milliseconds because they drove up a mountain
          After noticing your comment I read the whole article just because 22 ms sounded like an impossibly large relativistic effect for a car. It was actually 22 nanoseconds. You're off by a factor of a million.

      • Re:Please read the article (Score:4, Funny)

        by ari_j ( 90255 ) on Tuesday December 11, 2007 @10:24AM (#21655779)
        Yes, anyone with a cesium clock at home lives just a little more life than his neighbors.

    • Re: (Score:3, Insightful)

      by sm62704 ( 957197 )
      Funny yet insightful! How to mod, how to mod.

      Some people are way too anal. Jees, my ten dollar alarm clock is accurate enough for me, as are the cheap wall clocks, none of which ever differ by more than a minute.

      I have to set my clocks twice a year anyway. I don't have time to worry about what time it is.

      Next on slashdot: Obsessive Compulsive Disorder: Hallmark of the nerd? [wikipedia.org]

      -mcgrew [slashdot.org]

      -

    • Re: (Score:2)

      by dpilot ( 134227 )
      Years ago, my wife got me an indoor/outdoor thermometer that also included a radio-synced clock that works with WWV. Between that and NTP on my computers, time is kept close enough.

      Besides, the only time that *really* matters down to the minute is when you're trying to record a TV show, and *they* aren't that accurate.

      So it just doesn't matter.

      Makes me think of the line by the disillusioned engineer in Tracy Kidder's "Soul of a New Machine," "I'm going to a commune in Vermont where I don't have to deal wi

      • Re: (Score:2, Interesting)

        by Anonymous Coward
        > Besides, the only time that *really* matters down to the minute
        > is when you're trying to record a TV show

        Just because you have limited imagination..

        For example, when correlating long-baseline interferometer data
        from amateur radio astronomers there is ABSOLUTELY a requirement
        to have sub-millisecond accuracy.

        And that's just one example from recent experience.
      • I always wondered why every major city didnt have a time radio station and everything from watches to computers used it.
        Makes a lot of sense to do it that way.
        • They already do; many TV stations (mostly PBS stations, although I don't know if they've kept it up) transmitted a timecode signal in their vertical blanking interval. With a properly-designed receiver, you could pick it up and get decently-accurate time out of it. At the very least it was enough to set your VCR, which was basically its purpose.

          Unfortunately most of the VCR manufacturers never implemented it.
    • Despite the amount of confusing clocks you might have, a benevolent dictator of time becomes handy: Temps Atomique International (french) abbreviated: TAI. For us mere mortals who use time for civil needs, another timescale is dissiminated, Coordinated Universal Time (UTC). UTC is derived from TAI, but synchronized using leap seconds to UT1, which is based on actual rotations of the earth with respect to the mean sun.

      International Atomic Time (TAI, from the French name ) is a high-precision atomic time st

  • hm. (Score:3, Funny)

    by toQDuj ( 806112 ) on Tuesday December 11, 2007 @08:03AM (#21654271) Homepage Journal
    I like to be REALLY just on time for my meetings...

  • Comment removed (Score:5, Funny)

    by account_deleted ( 4530225 ) on Tuesday December 11, 2007 @08:03AM (#21654273)
    Comment removed based on user account deletion
  • I'd be too scared what his answer would be if I asked Tom Van Baak what time it is.

  • Stop. (Score:5, Funny)

    by RandoX ( 828285 ) on Tuesday December 11, 2007 @08:10AM (#21654323)
    Hammer time.

  • Am I the only one... (Score:3, Funny)

    by Anonymous Coward on Tuesday December 11, 2007 @08:13AM (#21654355)
    ...who can have two or more clocks and not constantly ask myself "what time is it?... really?"
  • Keeping accurate clocks synchronized is great and all..that is until accidental light-speed travel makes the whole thing pointless.
  • an article came up about atomic clocks and perfect time and I said...

    Does anybody really know what time it is?
    Does anybody really care?
    If so I can't imagine why
    We've all got enough time to troll....

    My apologies to Chicago.

  • Q-physics (Score:4, Funny)

    by mach1980 ( 1114097 ) on Tuesday December 11, 2007 @08:23AM (#21654451)
    If you really, really know what time it is. You will find yourself quite lost. Darn that Heisenberg!
    • Actually, you'll find yourself with quite indeterminate energy. Somewhere between college senior and Richard Simmons. Those are the two recognized physical limits on human energy states.
  • ... to my watch I do have time to respond.

    However, according to my computer I don't.

    Interestingly, my boss concurs with my computer.

  • See Time Fly (Score:3, Funny)

    by Dareth ( 47614 ) on Tuesday December 11, 2007 @08:36AM (#21654569)
    I always said it was fun to throw a clock out a high window so you could see time fly!

    One must much more careful with these new atomic clocks. After time flies, they explode and destroy whole cities!

  • First post (Score:5, Funny)

    by carpe_noctem ( 457178 ) on Tuesday December 11, 2007 @08:40AM (#21654607) Homepage Journal
    This is really the first post; your clocks just don't agree with mine.
  • Radio controlled clocks are sometimes called atomic clocks because their underlying time resides in a Colorado atomic clock.
    These clocks give accuracy within a second as does the ntpd daemon on Unix computers.
    The world seems in balance when you set 3 radio controlled clocks in front of your computer,
    then watch all four with the same hour, the same minute, count the same seconds.
    You shouldn't tell your clock the time -- your clock should tell you the time,
    which radio controlled clocks and computers running n

    • On the subject of german radio clocks: A well-meaning, elderly german friend or relative of my mother once sent her a radio clock as a christmas present. Since you have to be within about 2000km of Frankfurt/Main to receive the signal, and since it would not run without at least a first boot-up signal, this was not a very practical present, seeing that my mom lives in South Africa. I think she sent it back to someone else the following xmas.

      I wouldn't mind a clock though that picks up its signal from the G

      • You can buy a cheapo GPS module from Garmin or somebody and then plug into the serial port of your computer. With NTP, presto! Instant GPS time reference anywhere in the world.

        • Re: (Score:2)

          by tylernt ( 581794 )
          True, and that's fine for accuracy within a few seconds. The NMEA data is always streaming through the RS232 lagged a little behind reality though, and there is a fair amount of jitter unless your GPS receiver can skip all the other NMEA sentences and only send the time (i.e., in the time it took to send positional data through the port, the timestamp now coming through is a few hundred milliseconds "old"). To get stratum 0 quality time from GPS, you need a slightly more expensive unit with PPS (Pulse Per S
    • What is with radio controlled clocks? They seem worthless to me. I have an Oregon Scientific one sitting on my desk here that has never seen a time signal. Not here at my desk at the very south tip of the SF Bay, not at my old house 5 miles away, not sitting outside in the driveway or by the window. I've had it in the Seattle area as well, and it has never received a signal there, either.

      Is this whole thing a joke, or do these clocks actually work for some people? I had another one several years ago th
      • Yep, I've had several and they've all worked fine. Never lived on the West Coast, though. But I had a Radioshack alarm clock, with an external antenna, that seemed perfectly happy even in central Maine. Maybe the internal antennas on the clocks you're buying aren't very good? Or perhaps there's something generating interference on 660kHz (I think that's the frequency it uses) in your area.

      • Re: (Score:2)

        by wumingzi ( 67100 )
        Is this whole thing a joke, or do these clocks actually work for some people? I had another one several years ago that also did not work.

        I have an Oregon Scientific clock which has traveled with me from the South Bay to Seattle to Vancouver, BC and now back to Seattle. It works great and has done its part to keep me on time. As long as you are inside WWVB's footprint [nist.gov] and aren't doing wrong things which will mess with longwave propagation (i.e. living in a house which is running unshielded electric motors
      • I have two and they work fine for me both in my old house in Mountain View an my new house in Contra Costa.

        They are not totally immune to interference, if all your lights are on dimmers, or they sit right on top of your PC with an open case. But I get a "lock" about 4 out of 5 days.

      • Re: (Score:2)

        by Belial6 ( 794905 )
        I have had one that didn't work at all, one that worked all the time, and one that was intermittent. With the intermittent one, I actually read the manual, and found that it only tries to sync twice a day, so if you can't get a signal during the couple of minutes that it tries each day, the clock has to wait until the next cycle. Why they built it this way, I don't know, and I doubt that they all work this way, but it took about 3 days for it to get it's first signal.
        • Why they built it this way, I don't know,

          It's cos running the radio recever uses lots of battery power compared to running the clock alone.
          If the clock has its own quartz crystal for local timekeeping, then a 'lock' and resync to the radio time signal twice a day is *more* than enough for a very accurate household clock....

          • Re: (Score:2)

            by Belial6 ( 794905 )
            I new that the clock kept way better accuracy than necessary. I did not realize that the receiver would take enough power to matter. Thanks for the info.

      • Re: (Score:2)

        by Temkin ( 112574 )

        I've owned a Oregon Scientific WWVB clock since the late 90's. Used it both in the SF bay area, and central Texas. Worked fine in both places. It did provide some portable amusement once... It was my one and only visible Y2K bug. It fixed itself the next day. Weird...

        They can be interfered with. They don't like dimmers, touch lamps, and some CFL bulbs.

        • They can be interfered with. They don't like dimmers, touch lamps, and some CFL bulbs.

          The signal that it syncs with is basically an AM radio signal, so anything that that will mess around with AM radio reception will affect the clock. Also, you'll get a better signal at night too. I got one of those clocks, and it wasn't able to sync the day when I put the batteries in, but the next morning it was all synced up.

      • Re: (Score:2)

        by tgd ( 2822 )
        I don't know about the desk clocks, but I have a watch that picks up the signal and it rarely has any problems getting resynced.

  • What's the fascination with uber-accuracy at home? Hell, I'm perfectly content with "about" accurate stuff. Kinda reminds me of weather forecasts. I remember when the weather forecast was "High in the upper 60's". If it was 46 or 70, no one complained. Now, it's "High today is 72" and people bitch when it reaches a sweltering 73.

    For many services and uses, highly-accurate clocks have their place, but for every-day home use?

    • Re: (Score:2)

      by jbarr ( 2233 )

      If it was 46 or 70, no one complained.

      Oops, that should have been "66", not "46".

    • Re: (Score:3, Insightful)

      by Alioth ( 221270 )
      It's a hobby. Some people like to ride, say, horses for a hobby. Not terribly useful now everyone has cars. What's the use? The use is that someone enjoys doing it. Like the horse rider, the time keeping hobbyist enjoys tinkering with highly accurate time pieces.

      If you have to question why people have hobbies you don't find interesting, you're amazingly lacking in imagination.

      • Re: (Score:2)

        by Magada ( 741361 )
        Maybe he meant practical uses? Like, say, crypto? Say there's a universally accessible source of noise (such as background microwave radiation) which both Bob and Alice sample and digitize at a given rate starting from an "offset" in time known only to the both of them. They now have an arbitrarily long one-time pad at their disposal!

      • Re: (Score:2)

        by jbarr ( 2233 )
        Ok, I'll grant you the hobby aspect of it--that certainly cannot be denied. Were it not for dedicated hobbyists, many innovations and inventions would never have seen the light of day. It just seems to me that so many things are becoming so tuned to such fine-grained timings, and people are becoming more and more dependent upon these things that they miss the larger picture, and become helpless when something in such a fine-tuned system goes awry.

    • Re:I don't get it. (Score:4, Informative)

      by ChrisA90278 ( 905188 ) on Tuesday December 11, 2007 @01:24PM (#21659271)
      What's the fascination with uber-accuracy at home?

      They are calling these "clocks" only because that is what the typical reader understands. A better term is "frequency standard". There are many uses for a stable frequency, the most common one is running a microwave transmitter. This is the major source of the surplus devices too, from cell towers. As the phone companies modernize equipment these "clocks" find their way to eBay and then into people's houses.

  • The true obssessive (Score:3, Funny)

    by elrous0 ( 869638 ) * on Tuesday December 11, 2007 @09:10AM (#21654905)
    I would bet money that at least one of these guys adjusts for the speed of light between his eyes and the average viewing distance to his clock.

    I would also venture to guess that he has no girlfriend.

    • Re: (Score:3, Funny)

      by vadim_t ( 324782 )
      Well, at least the one mentioned in the article reproduced already.

      Maybe this is what geeks should do. Pretend to be normal people for a few months, get married, have children, and THEN fill the house with strange hardware.
      • The next generation of geeks comes! The first guy from Washington took atomic clocks on his family camping trip and showed his children direct evidence of Einsteins Theory of Relativity. If I were growing up and my father showed me this, not to mention other cool time/electronics like this guy has, you can guarantee that I'd be hooked. Not that I'm already hooked by other things, but you get my point.
    • What is this about geeks not having girlfriends? I've had plenty of girlfriends... boyfriends too for that matter, and I'm about as geeky as it gets (For my desktop background I made an in my opinion artistic SVG diagram of U-235 and U-238 fission cross-sections plotted against incident neutron energy, I think that qualifies...)

      So I'd say that joke is thoroughly debunked, unless you somehow come claim boyfriend - girlfriend interaction causes destructive interference... Hmm, thinking about it, that is prob

  • Half way solution: GPS (Score:5, Informative)

    by FridayBob ( 619244 ) on Tuesday December 11, 2007 @09:37AM (#21655205)
    NTPD isn't good enough for me -- bad weather on the Internet has caused my server to loose synchronization one too many times, which can be mighty irritating when comparing your log files with those of other systems. On the other hand, acquiring an atomic clock seems a bit over the top to me. So, I figured a good compromise solution would be to connect a GPS receiver to my serial port and synchronize NTPD to that. I've ordered a Garmin GPS 18 OEM LVC [garmin.com] that I will receive later this month (hopefully). According to these instructions [qnan.org] it's not that difficult to set up, while the result is microsecond precision on Linux 2.6 and nanosecond precision on BSD -- good enough for me. All you need to do is to make sure that your GPS device has a reasonable view of the sky.

    • Re: (Score:2)

      by renoX ( 11677 )
      >which can be mighty irritating when comparing your log files with those of other systems

      Are those other system on the same LAN?
      If yes, synchronise one server (two for redondancy) and use it as the time reference for all your systems..

      • Are those other system on the same LAN?
        Nope; in that case this wouldn't be an issue. I was referring to remote systems.
    • NTPD is not good enough? How far off does your system drift after being disconnected from a server? Typically not more than seconds per day. Have you ever lost an Internet connection for more then a day. Even so all your servers would still remain sync'd to each other. I hope you do not have all of your local machines going over the Internet to get time. Set up three or four local machines to be level 3 and then the others sync to those.

      • NTPD is not good enough? ...

        Usually there's no problem, but a handful of of times in the last six years there has been, and it's the frequency of these errors that I hope to reduce. Of course, I could just be headed for a different set of problems, but we'll see about that when we get there.

        How far off does your system drift after being disconnected from a server? ...

        I can't say for certain, but it is my understanding is that NTPD stops syncing when the time difference becomes greater than five seco

    • Re: (Score:2)

      by nthomas ( 10354 )
      NTPD isn't good enough for me -- bad weather on the Internet has caused my server to loose synchronization one too many times,

      Your NTP setup is misconfigured if this is the case.

      The NTP daemon has many algorithms built in to measure jitter (how "off" a clock is from what NTP thinks is the realtime) and factors in network delay as well. (Run ntpq -p [udel.edu] to see a list of time servers that your NTP client is accessing and their associated jitter/delay/offset values.)

      NTP's primary job is to poll

      • Re: (Score:2)

        by Temkin ( 112574 )


        Furthermore, he should be able to "fudge" the stratum of one of his servers to a slightly higher priority so that his entire organization drifts as a whole, rather than each machine independently.

      • Your NTP setup is misconfigured if this is the case.

        I don't know about that. I thought my /etc/ntp.conf was okay:

        driftfile /var/lib/ntp/ntp.drift
        statsdir /var/log/ntpstats/
        statistics loopstats peerstats clockstats
        filegen loopstats file loopstats type day enable
        filegen peerstats file peerstats type day enable
        filegen clockstats file clockstats type day enable
        server ntp.xs4all.nl
        server ntp2.xs4all.nl
        server ntp2-3.xs4all.nl
        server ntp2-4.xs4all.nl
        server ntp2.theinternetone.net
        server ntp2d.mcc.ac.uk
        server n

  • Sure, he's got all those fancy clocks in his "Time Lab", but they only go forward!

    - RG>
    • Sure, he's got all those fancy clocks in his "Time Lab", but they only go forward!

      He just needs a flux capacitor and a supply of terrorist-grade plutonium.
  • Does anybody really care? If so I can't imagine why, We've all got time enough to cry . . . . (For all the oldsters out there)

  • No no no, the saying is... (Score:5, Informative)

    by Relic of the Future ( 118669 ) <{gro.skaerflatigid} {ta} {selad}> on Tuesday December 11, 2007 @10:11AM (#21655595)
    They got the saying all wrong. It goes "A man who wears one watch always knows what time it is; a man who wears two watches is never sure."

  • "If you have one clock... you are peaceful and have no worries. If you have two clocks... you start asking, 'What time is it, really?'"
    If you have an entire garage of clocks, you can scare the shit out of your teenage neighbor when they all strike 8:00 AM.

    For extra fun, tell him that they are all twenty minutes slow, making him late for school.
    • If you fill your garage with clocks, where will you park the DeLorean? /Get back, Marty //guitar riff goes here
  • I found a great alternative to ntpd: I just use my $20 Casio digital watch to set time on all my servers once in a while. Why cares about time anyway? Is it December yet?

  • How to set? (Score:3, Interesting)

    by russotto ( 537200 ) on Tuesday December 11, 2007 @11:12AM (#21656641) Journal
    OK, as much fun as it would be to have my own stratum-1 NTP server, how do you (read: some ordinary joe, not a university researcher) synchronize these things to TAI in the first place?

    • Re: (Score:2)

      by msauve ( 701917 )
      The easiest, and most common method, is to lock to GPS. GPS time [navy.mil], like TAI, is not adjusted for leap seconds like UTC. GPS time is 19 seconds behind TAI.

      But note, NTP isn't based on TAI, but on UTC, so a leap second table is required to maintain accurate time. That's the simple explanation. NTP/UTC/leap seconds is more complex in reality. [udel.edu]
      • I'm not really worried about the whole-second offsets, they're relatively straightforward. I'm just thinking that as precise as my (wholly hypothetical) atomic clock is, it can't be truly accurate unless I can somehow synchronize it precisely with some equally precise standard. Is GPS (or any reasonable GPS receiver I might lay my hands on) precise enough to synchronize an atomic clock to within that clock's own inherent precision?

        • TAI itself isn't known until after the fact, since it is an average of multiple national time standards. Even those standards aren't synchronized to within their inherent precision. Different clocks which contribute to TAI can differ from each other [navy.mil] in the microsecond range.

          Timing GPS receivers can sync to well under that. NIST has some information on tracability. [nist.gov]

          The short answer is that your question was in regard to NTP, and a time server locked to GPS time is considered to be Stratum 1.
  • ...lunch-time doubly so.'

    Ford Prefect. Which is very apt, because today is Mos Def's birthday.

  • He wanted his children to see that relativity is proportional.

    'nuff said.

  • Whew, there's IS an "L" in that word.... was worrying... for a second, or two... tick tock, tick tok...
  • I have a clock that I know is absolutely accurate twice a day. Snag is, if I don't put a new battery in it I don't actually know even approximately what the time is!
  • Some guy playing with clocks making sure everyone else gets a correct time via ntp.

    Some people playing with code making sure everyone has access to good quality free software. I can't code worth sh.., but have been a very grateful (bug reports) and happy Debian user for almost ten years now.

    Just great :-)

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