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Playing With Atomic Clocks At Home

kdawson posted more than 6 years ago | from the as-i-was-walking-down-the-street-one-day dept.

Hardware Hacking 167

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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167 comments

Clearly.... (5, Funny)

Smidge204 (605297) | more than 6 years ago | (#21654265)

...Some people have too much time on their hands.

=Smidge=

Re:Clearly.... (4, Funny)

Kranfer (620510) | more than 6 years ago | (#21654403)

This is no time to argue about time, we don't have the time!

Re:Clearly.... (0)

Anonymous Coward | more than 6 years ago | (#21655721)

"Cannot run out of time. There is infinite time. You are finite. Zathras is finite. This... is wrong tool."

-- Zathras, Babylon 5.

First Communist Party Post: OBVIOUSLY (-1, Troll)

Anonymous Coward | more than 6 years ago | (#21655791)


I'ts time to incarcerate this War Criminal [whitehouse.org] .

Thanks for your support.

Re:Clearly.... (1)

haystor (102186) | more than 6 years ago | (#21656249)

Life is very short and there's not time for fussing and fighting my friend.

Re:Clearly.... (2, Funny)

Foundryman (306698) | more than 6 years ago | (#21654413)

and "it's ticking away with my sanity...."

Please read the article (5, Funny)

fishdan (569872) | more than 6 years ago | (#21654731)

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:Please read the article (1)

Domstersch (737775) | more than 6 years ago | (#21654759)

Uh, gravity? I think you mean velocity.

Re:Please read the article (0)

Anonymous Coward | more than 6 years ago | (#21654957)

No, he means gravity. Learn your relativity, and RTFA.

Re:Please read the article (0)

Anonymous Coward | more than 6 years ago | (#21656657)

Learn your special relativity, not just general. OK? Thanks.

Re:Please read the article (1)

Atti K. (1169503) | more than 6 years ago | (#21655013)

Uh, yes, gravity [wikipedia.org] .

Re:Please read the article (1)

Domstersch (737775) | more than 6 years ago | (#21656547)

OK, looks like I underestimated the effect of gravitational dilation (general relativity, if you like) versus ordinary old velocity dilation (special relativity). Gravitational dilation would certainly play a part. Although, I'm not convinced most of the 22 nanoseconds was due to it.

In the famous clocks-in-jetplanes example, velocity accounted for about 10% of the dilation. But in this case we have 3 hours at 30m/s, versus 48 hours at 4000m. Anyone want to take a guess at the relative (heh) effects of each?

Re:Please read the article (0)

Anonymous Coward | more than 6 years ago | (#21656263)

I think he was talking about YOU when he said please read the article

Re:Please read the article (2, Funny)

Anonymous Coward | more than 6 years ago | (#21654767)

>>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 (3, Informative)

brunes69 (86786) | more than 6 years ago | (#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 (3, Insightful)

sg3000 (87992) | more than 6 years ago | (#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 (4, Funny)

jgoemat (565882) | more than 6 years ago | (#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 (4, Informative)

timeOday (582209) | more than 6 years ago | (#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 (3, Funny)

ari_j (90255) | more than 6 years ago | (#21655779)

Yes, anyone with a cesium clock at home lives just a little more life than his neighbors.

Re:Please read the article (1)

Foundryman (306698) | more than 6 years ago | (#21656059)

No, no, no...it's not enough to have a cesium clock at home. You have to take it on vacations and family outings in order to live a little more than your neighbors!

Re:Clearly.... (3, Insightful)

sm62704 (957197) | more than 6 years ago | (#21654835)

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:Clearly.... (1)

dpilot (134227) | more than 6 years ago | (#21655041)

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 with any unit of time shorter than a season."

Re:Clearly.... (2, Interesting)

Anonymous Coward | more than 6 years ago | (#21655549)

> 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.

Re:Clearly.... (1)

cheater512 (783349) | more than 6 years ago | (#21656723)

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.

Keeping track of time (2, Informative)

Device666 (901563) | more than 6 years ago | (#21656319)

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 standard that tracks proper time on Earth's geoid. It is the principal realisation of Terrestrial Time. As of 2007 TAI is exactly 33 seconds ahead of UTC: 10 seconds' initial difference at the start of 1972, plus 23 leap seconds in UTC since 1972. TAI in this form was synchronised with Universal Time at the beginning of 1958, and the two have drifted apart ever since.

Accurate time is very important for computer systems/networks. The best way to keep track of time is to install a local timeserver which synchronizes against a reliable public timeserver like pool.ntp.org. The local time server can be used to synchronize other computers you might have.

hm. (2, Funny)

toQDuj (806112) | more than 6 years ago | (#21654271)

I like to be REALLY just on time for my meetings...

Re:hm. (1)

phillips321 (955784) | more than 6 years ago | (#21654479)

it's cool to be late!

Re:hm. (1)

jimmydevice (699057) | more than 6 years ago | (#21654699)

until you get fired

As Linus might say (4, Funny)

CRCulver (715279) | more than 6 years ago | (#21654273)

Real men just run ntpd and let the whole world keep time for them.

NTP pool (1)

tepples (727027) | more than 6 years ago | (#21654359)

Real men just run ntpd and let the whole world keep time for them.
Except in democratic America, John Ackerman runs ntpd and keeps time for whole world [ntp.org] . (Bottom of page 1.)

Re:NTP pool (1)

morgan_greywolf (835522) | more than 6 years ago | (#21654637)

Okay, I just can't figure out what the heck you're talking about. At the bottom of page 1, see:

Vendor information available

The new information for vendors page is up! Please let me know if your operating system/appliance/software vendor is using the NTP Pool but isn't using a vendor zone.
I follow the link for vendor information and see nothing about this John Ackerman.

Re:NTP pool (1)

tepples (727027) | more than 6 years ago | (#21655217)

At the bottom of page 1, see:

Vendor information available
I apologize for not clarifying that I meant page 1 of The Article [wired.com] , which states the following:

John Ackerman, an attorney with a technology company, offers super-accurate time over the internet to anyone who wants it, courtesy of four of the most accurate NTP (network time protocol) servers in the world.

Re:As Linus might say (1)

Bucc5062 (856482) | more than 6 years ago | (#21654371)

Real men just run ntpd and let the whole world keep time for them

Real geeks just run ntpd and let the whole world keep time for them....better!

Real men... (3, Funny)

ZeroExistenZ (721849) | more than 6 years ago | (#21654429)

Real men just run ntpd and let the whole world keep time for them.

Anyone can make the world keep time for them. Only real men can make the sun keep it for them.

I'd be scared (1)

DeeQ (1194763) | more than 6 years ago | (#21654307)

I'd be too scared what his answer would be if I asked Tom Van Baak what time it is.

Re:I'd be scared (1)

Daimanta (1140543) | more than 6 years ago | (#21654631)

That's easy. Ask what time it is. Wait for long explanation.

Result: It's one hour later!

Stop. (5, Funny)

RandoX (828285) | more than 6 years ago | (#21654323)

Hammer time.

Re:Stop. (1, Funny)

Junior J. Junior III (192702) | more than 6 years ago | (#21654655)

Please don't hurt him.

Re:Stop. (1)

StarfishOne (756076) | more than 6 years ago | (#21654913)

Pstt! We're not in the 90's anymore! Don't you know your XKCD classics? ;P

http://xkcd.com/210/ [xkcd.com]

for the official US time.... (1)

cynicsreport (1125235) | more than 6 years ago | (#21654347)

use www.time.gov [time.gov]

Re:for the official US time.... (1)

nicklikesfire (720684) | more than 6 years ago | (#21654805)

Do you ever have time to post on the WIFS boards?

Am I the only one... (3, Funny)

Anonymous Coward | more than 6 years ago | (#21654355)

...who can have two or more clocks and not constantly ask myself "what time is it?... really?"

Re:Am I the only one... (0)

Anonymous Coward | more than 6 years ago | (#21654917)

Oh man, you're seriously missing out on some crazy femtosecond fun!! (If nanoseconds are more your thing, a few of the guys a coming around for a dual-television-synchronicity party later on.. feel free drop to drop in.)

really worthwhile? (1)

digitalderbs (718388) | more than 6 years ago | (#21654383)

Keeping accurate clocks synchronized is great and all..that is until accidental light-speed travel makes the whole thing pointless.

As I was reading slashdot dupes one day... (1)

DigitalReverend (901909) | more than 6 years ago | (#21654411)

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.

Re:As I was reading slashdot dupes one day... (1)

sjaguar (763407) | more than 6 years ago | (#21654551)

Yeah, the time is either 25 or 6 to 4.

Q-physics (5, Funny)

mach1980 (1114097) | more than 6 years ago | (#21654451)

If you really, really know what time it is. You will find yourself quite lost. Darn that Heisenberg!

Re:Q-physics (1)

gardyloo (512791) | more than 6 years ago | (#21655415)

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.

According... (1)

boris_the_hacker (125310) | more than 6 years ago | (#21654467)

... to my watch I do have time to respond.

However, according to my computer I don't.

Interestingly, my boss concurs with my computer.

Einstein says (1)

pinguwin (807635) | more than 6 years ago | (#21654473)

Maybe they drive the clock around the block for a while trying to see if they relativistic time effects like Hafele and Keating http://www.teslaphysics.com/Chapters/Chapter030-H-K.htm [teslaphysics.com]

Summary of article: Synchronize two atomic clocks and fly one clock around world in jet and see if it differs from a clock at "rest" on the ground.

They did see if they could alter the clocks by gravity, motion is another way.

How long... (1)

Tongsy (1188257) | more than 6 years ago | (#21654565)

until they are thrown in prison for being terrorists because they have these clocks and are accused of trying to make dirty bombs from them?

See Time Fly (2, Funny)

Dareth (47614) | more than 6 years ago | (#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!

Re:See Time Fly (1)

Yetihehe (971185) | more than 6 years ago | (#21654681)

"You must be carefull only of those civilizations whose clocks count to zero."

Re:See Time Fly (0)

Anonymous Coward | more than 6 years ago | (#21655531)

And like a practiced golfer, the time aficiando will shout: "TIME OUT!"

First post (5, Funny)

carpe_noctem (457178) | more than 6 years ago | (#21654607)

This is really the first post; your clocks just don't agree with mine.

Re:First post (1)

riffzifnab (449869) | more than 6 years ago | (#21655465)

You want a fight? Don't make me clock you.

what time is it really ? (1, Funny)

Anonymous Coward | more than 6 years ago | (#21654635)

>>>> If you have two clocks... you start asking, 'What time is it, really?'"

Time to buy a 3rd clock? :)

Radio Controlled clocks would do (2, Funny)

Jameson Burt (33679) | more than 6 years ago | (#21654707)

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 ntp do tell.

Frustrated by clocks throughout my home with different times,
advanced by my wife to advance me, one clock advanced by 3 hours;
I got 7 radio controlled clocks which she cannot set because they set themselves.
Additionally, they give the day of week (Wednesday) and the date (December 11).

I first saw a radio controlled clock in 1992 while in Germany -- a $200 clock made by Jungans.
Several internet companies which mainly sell weather equipment also sell radio controlled clocks.
I purchased 7 of these made by Lacrosse, which can have a big LCD and can cost as little as $10 (US).

Re:Radio Controlled clocks would do (0)

Anonymous Coward | more than 6 years ago | (#21655049)

Additionally, they give the day of week (Wednesday) and the date (December 11)

Might wanna check dem clocks.

Are you a bot ? (0)

Anonymous Coward | more than 6 years ago | (#21655053)

/me Looks at TFA then looks at Jameson Burts post full of quotes

Dude, are you a bot ?
You sure have a weird posting history of "poetic" quotes from the articles.

Re:Radio Controlled clocks would do (0)

Anonymous Coward | more than 6 years ago | (#21655055)

I have a radio controlled solar powered watch. It's awesome.

Re:Radio Controlled clocks would do (1)

FudRucker (866063) | more than 6 years ago | (#21655065)

umm, this is Tuesday December 11, 2007

HappyTrails:)

Re:Radio Controlled clocks would do (2, Funny)

RockedMan40 (1130729) | more than 6 years ago | (#21655571)

His wife must have /.'ed him already........

Re:Radio Controlled clocks would do (1)

codeButcher (223668) | more than 6 years ago | (#21655159)

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 GPS satellites. Or Galileo, once it becomes operational, but probably not both, since which one is correct? ;-)

Re:Radio Controlled clocks would do (1)

the_other_chewey (1119125) | more than 6 years ago | (#21655413)

On the subject of german radio clocks: [...] you have to be within about 2000km of Frankfurt/Main to receive the signal

It's a bit off Frankfurt actually, in Mainflingen, here's google maps' aerial view [google.de] of the facility.

The signal that's broadcast from there is generated in Braunschweig by the PTB (the german counterpart to the NIST, sort of) using a couple of different technolgy caesium clocks. (wikipedia about the system [wikipedia.org] ).

Its range is very impressive, and even intercontinental reception can happen when all conditions (weather etc.) are just right, synchronisations as far as in Canada, the US and the Sahara have been reported. That's very rare though.

I don't get it. (1)

jbarr (2233) | more than 6 years ago | (#21654883)

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:I don't get it. (1)

jbarr (2233) | more than 6 years ago | (#21654903)

If it was 46 or 70, no one complained.

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

Re:I don't get it. (2, Insightful)

Alioth (221270) | more than 6 years ago | (#21654919)

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:I don't get it. (1)

Magada (741361) | more than 6 years ago | (#21655539)

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:I don't get it. (0)

Anonymous Coward | more than 6 years ago | (#21655935)

You wouldn't say that if you rode the bus and lived someplace where it got cold.

The bus company here uses the time from WWVB; it's the time posted in their offices, the time their drivers are required to keep while on-route, and the time displayed by the radio-controlled clock on many of their busses. If I also keep that time, and live near a time point on the route, I can avoid several minutes of standing outside in the weather without fear of missing the bus. I could probably stand a few seconds of drift, but I need accuracy well within a minute for this system to be reliable.

Other synchronization events come to mind as well -- I'd like my DVR to begin and end recording when the show actually starts and stops, but my DVR can't actually tell one show from another, so I use the published schedule of shows instead, which again requires that both my clock and the one at some distant location I don't control (i.e. the TV broadcaster) are keeping the same time. This system is even less forgiving for drift, anything more than about a second could get annoying very quickly.

I'm sure I could come up with other uses for second-or-better accurate time in your home, which you can't get from a battery-powered quartz clock. Not to mention some people just like playing with clocks, much like woodworking or futzing with computers.

The true obssessive (2, Funny)

elrous0 (869638) | more than 6 years ago | (#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:The true obssessive (2, Funny)

vadim_t (324782) | more than 6 years ago | (#21656337)

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.

In the news (1)

nerdyalien (1182659) | more than 6 years ago | (#21654933)

Today, major swiss watch manufacturers declared they will be out of business in another decade as the atomic clocks will become the mainstream user friendly wrist watches.... ohh wait... aren't we too late to issue this news.. hold on..

got a shorwave reciever? (1)

FudRucker (866063) | more than 6 years ago | (#21655019)

you can hear NIST's WWV transmitters on 2.5, 5, 10, 15 & 20 megahertz AM (amplitude modulation), i set the clocks with my shortwave radio...

Confucius says..... (1)

deep_creek (1001191) | more than 6 years ago | (#21655113)

Confucius says.....

"man with one watch always know exactly what time it is....man with two watches never quite sure."

Half way solution: GPS (4, Informative)

FridayBob (619244) | more than 6 years ago | (#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:Half way solution: GPS (0)

Anonymous Coward | more than 6 years ago | (#21655547)

Replace 'reasonable view' with 'is outside, on the roof, in the countryside'.

The receiver on those GPS18's sucks.. outside my house even my N95 can see 3 satellites and the average TomTom has a perfect lock.. the GPS18 refuses to lock at all.

Re:Half way solution: GPS (1)

elysium-os (998821) | more than 6 years ago | (#21655585)

Okay first of all I am **NOT** some time freak but...

The latency on the USB bus is so bad that you get a better time using NTPD, even when using a server on the other side of the world!

But it does have a better nerd factor so good luck!

Marcel

Re:Half way solution: GPS (1)

wed128 (722152) | more than 6 years ago | (#21655813)

not to mention NMEA 0183 is specced to 4800 baud rs232!

Re:Half way solution: GPS (1)

FridayBob (619244) | more than 6 years ago | (#21656235)

The latency on the USB bus is so bad...
Who said anything about a USB version? I've ordered the LVS version and mean to attach it to the serial port using some simple electronics and a small power supply. The only thing I might want to use the USB bus for is as an alternative power source, as the linked article suggests.

Re:Half way solution: GPS (0)

Anonymous Coward | more than 6 years ago | (#21656559)

Either way isn't very good. Unless you buy a better receiver (we use TrueTime) the latency of the NMEA messages will be unpredictable. As the article linked you explains, you need to use the PPS signal to get better than 100 ms accuracy. The PPS is just a clock signal (square wave).

Re:Half way solution: GPS (2, Informative)

russotto (537200) | more than 6 years ago | (#21656699)

With a GPS time source you get the time value (in ASCII) through a serial port, but the synchronization is done through a pulse per second interrupt. So the latency on the serial bus doesn't matter as long as it is significantly less than one second.

Re:Half way solution: GPS (1)

SevenHands (984677) | more than 6 years ago | (#21656183)

Unfortuntaely some of us still live in our parents' basement thus barring us from ever seeing the light of day, much less a clear view of the sky.

Re:Half way solution: GPS (1)

dino2gnt (1072530) | more than 6 years ago | (#21656327)

That's why you should run a local ntpd server and sync your machines to it instead of having all your nodes sync to some external ntp source. Sync the master, and let your client machines sync to it.

Re:Half way solution: GPS (1, Informative)

Anonymous Coward | more than 6 years ago | (#21656711)

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.

How many upstream servers do you sync to? "Bad internet weather" shouldn't desync your NTP server given enough peers to talk to. My local NTP server syncs up to five remote servers spread over three continents, and the only event that my NTP server process noticed was my DSL modem melting down.

My long-term NTP traffic rate is maybe 1 packet every 5 minutes, so it takes a hella big network disruption to make NTP take notice.

I've ordered a Garmin GPS 18 OEM LVC that I will receive later this month (hopefully). According to these instructions 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.

... and that you have a way of using the GPS18's PPS output to set your clock, because the *ONLY* way you are going to get sub-second accuracy out of your setup is to set your clock as soon as possible after the PPS output goes active. The GPS isn't going to give you any other help, since its NMEA stream only provides time accuracy to one second (or 0.1 second if you get the GPS18 version that gives you five PPS transitions per second). The PPS output is the only authoritative source as to when that second occurs.

Joke's on him (2, Funny)

RealGrouchy (943109) | more than 6 years ago | (#21655223)

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

- RG>

mod 0p (-1, Flamebait)

Anonymous Coward | more than 6 years ago | (#21655241)

Satan's Dick and [goat.cx]

Does anybody really know what time it is? (1)

LazloToth (623604) | more than 6 years ago | (#21655255)

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)

If you have one clock... (1)

Le Marteau (206396) | more than 6 years ago | (#21655275)

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?'"

What kind of blather is that? Did he read that from a fortune cookie or something? I could almost hear the sound of a gong somewhere.

If you have one clock, you can't be sure what time it is. If you have two clocks, and they are both within a minute of each other, you can be fairly sure what time it is.

No no no, the saying is... (5, Informative)

Relic of the Future (118669) | more than 6 years ago | (#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... (2, Funny)

CSMatt (1175471) | more than 6 years ago | (#21655629)

"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.

Re:If you have one clock... (1)

El_Smack (267329) | more than 6 years ago | (#21655797)

If you fill your garage with clocks, where will you park the DeLorean? /Get back, Marty //guitar riff goes here

Relieving (1)

jockeys (753885) | more than 6 years ago | (#21655711)

to know I'm not the only one who obsesses about this sort of thing. Makes me feel fairly normal for being upset when my watch gains a second every other week and I worry about not being on time.

Does anybody really know what time it is? (0)

Anonymous Coward | more than 6 years ago | (#21655753)

Does anybody really care?

Keeping time (1)

Venik (915777) | more than 6 years ago | (#21656139)

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?

A cheaper alternative (1)

Hanners1979 (959741) | more than 6 years ago | (#21656473)

Just buy a clock and don't put any batteries in it - It's guaranteed to be 100% accurate two times a day.

How to set? (2, Interesting)

russotto (537200) | more than 6 years ago | (#21656641)

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?

'Time is an illusion... (2, Interesting)

jackpot777 (1159971) | more than 6 years ago | (#21656679)

...lunch-time doubly so.'

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