Reminds me of a highly accurate clock used in broadcasting. This clock sends out a time signal around the building to various clocks on walls and equipment, e.g. 'VT machines' (or whatever is used now).
I had the pleasure of adjusting this clock for GMT/BST twice a year. The great thing about this clock was that it did not actually tell the time itself. One would have to walk out of the machine room and through a couple of corridors, up a flight of stairs and into a gallery to actually see the alleged time with one's own eyes. All it had was a MODEM socket hidden in the back of a 19U rack, with the wires in U.S. configuration rather than what we have in the U.K.
So, to change the time you could 'conveniently' solder up a lead that would actually connect to the box, telnet in, remembering to get the password right, then set the time zone using the obscure command procedure provided.
This would be a simple enough task, however, there would be two of these clocks and they would talk to each other. So changing the time on one would not be good enough, the other would correct it or set it ahead/back by another hour. For added convenience the other 'master' clock would be in an entirely different part of the building and need to stay 'on' the whole time.
When it comes to extreme horology, I think that the most stupendously over-the-top accurate timepieces should not actually be able to tell the time with something as cheap and tacky as a display. If the time does have to be displayed then it should be in UNIX epoch time as that is the most convenient for all concerned.
Are there any experts on the subject that can tell how accurate these documentaries are? I find it fascinating, but am always sceptical about the simplifications they might use.
If the time does have to be displayed then it should be
in UNIX epoch time as that is the most convenient for all
concerned.
Unix time isn't monotonic: leap seconds are added by double-spending: 915148800.00 occurred twice. This means it's ambiguous, that unix timestamp refers to two different points in time, one second apart.
I am actually very pleased to have learned that snippet of useful information!
FYI when I wrote my comment I had just added an attribute to a product catalog that uses [very large number] - [product creation date in epoch format] so that I could have a latest added as the sort order without having to go through the bother of having DESC on my SQL query.
I assure you that only on HN could you find someone that is delighted to know about how 'unix time is not monotonic'... - thanks!
Quote: "So, yes, not only do we live in a time when atomic clocks are altimeters, but when relativity is child's play. It was the best extra 22 nanoseconds I've ever spent with the kids."
So, if you have a room that's got a dimension larger than 6 meters, and a fast oscilloscope, you can have a situation in which it is both easy and impossible?
I get in trouble regularly with my wife because I've been trained my whole life to think in a particular way, and that's not how other humans are wired:
if (a) {
b;
}
if (c) {
d;
}
versus
if (a) {
b;
}
else if (c) {
d;
}
She has mostly learned to put up with me by now, but the difference (how programmers think) still comes out sometimes.
Edited to explain: programmers don't think exactly like other humans.
Of course, in programming in the first case, "b" and "d" both happen when "a" and "c" are both true in many languages, unless "b" is something like "return e"
But, anyway, I was mostly joking -- its not like your meaning was at all unclear.
For a little bit of context, leapsecond.com is the website of Tom Van Baak, one of the "Time Nuts", people striving (sometimes: obsessed with) to maintain precise clocks and oscillators, mostly for the fun of it.
Here's a recent talk of him, at the ARRL and TAPR Digital Communications Conference, 2013.
Thanks for posting those! I came across the leapsecond site years ago and enjoyed it but haven't been back in a while. If I wasn't already so over-hobbied I'd probably be a time nut. My father is a ham radio operator and always set the clocks in the house from the WWV broadcasts, thus establishing in me at a young age an appreciation of accurate clocks.
Also you can get fairly cheap rubidium clocks from ebay that tend to output around 10MHz for fairly cheap. They would be less accurate that the one he's sporting however.
Re the radio synchronized watches, it's annoying that most of them listen to things like WWV, which is geographically limited.
The Seiko Astron is probably the best alternative, since GPS sync works over the whole planet. Unfortunately, expensive. (http://www.seiko-astron.com/)
There are a lot of digital GPS watches (Garmin, Suunto, etc.), but some of them (for some reason) don't sync the displayed watch time to GPS time.
Watches actually listen to WWVB, not WWV. (WWV is on HF, WWVB is on LF.)
On a good propagation day, you can probably hear WWV around the world. If it wasn't for other countries broadcasting their time stations on the same frequency, that is.
Ultimately, LF time synchronization is a good idea. It doesn't depend on additional ionospheric information to get an accurate time transfer, since signals do not travel through the ionosphere. HF signals take different routes at different times of day, and GPS time transfer requires an accurate site survey and accurate ionospheric delay constants.
Btw. I happen to know the guy who directed the ad. I just don't understand why Japanese watchmakers don't market their GPS watches more heavily and in a much lower price range. I feel that there is a huge market gap for well made $300-700 watches with GPS synched time. There's cheap quartz that aren't synched, there's the expensive Seikos and Citizen watches ($1000-$3000), there's mechanical Swiss watches you have to set up yourself ($500 to whatever you want to pay) and there's mechanical watches with perpetual calendar (start at $10k or so). As a result, Swiss watchmakers get most of world's earnings. Others just try to either emulate the Swiss or cheap Japanese quartzes from the past.
Since that post is quite old, I was surprised that this wasn't a reference to Bathy's recent efforts to make a wristwatch out of a chip scale atomic clock that is much closer to actual wristwatch scale (though still very large).
There is now a 17cm3 atomic clock chip on the market for about $2300, well under the price of a high-end watch. I'm surprised nobody's made a wristwatch with that.
Perhaps I should've said "wristwatch formfactor", you're right, battery performance would not approach cheap digital watch, not by a long shot. But at at 120mW, you'd be able to get a few hours out of it with a CR2032 cell, which is better than useless. Garmin made GPS wrist units that up until recently have done no better than this, although admittedly, there's probably more utility in having a GPS on your wrist than an atomic clock.
Your could write "HOURS AND HOURS OF BATTERY LIFE!!" on the packaging.
Because a >>$2300 wristwatch is a piece of jewelry, not a way to tell accurate-to-the-second time. Typically, it will have an intricate mechanical movement and be almost as accurate as a $5 quartz-driven electronic watch from the gift shop.
Absolutely. See Slyde watches: https://www.slyde.ch/
$5k+ for a watch with an LCD screen you can update via software. I appreciate they use high materials in the construction, but the profit margin on these must be huge.
Well, I think all watches are made of atoms and hence ATOMIC. I think most just don't intentionally include an atom of cesium, ask it to resonate, and then measure the frequency. ;)
This story is tacked up on the wall inside the clock room at the Arecibo Radio Observatory. The "Keeper of the Clocks" here eagerly awaits a true atomic watch based off the CSAC SA.45s chip that @daniel-cussen mentioned.
How go the repairs there? I loved visiting the observatory and museum hall on my first few trips to PR.
Did they manage to keep all or most of it open to the public or is it now purely a science installation?
Edit: Ah, I found a link to the visitor's center ( http://www.naic.edu/outreach/describe_fset.htm ). Happy to see it is still serving the public and looking forward to taking my kids there next trip down.
I had the pleasure of adjusting this clock for GMT/BST twice a year. The great thing about this clock was that it did not actually tell the time itself. One would have to walk out of the machine room and through a couple of corridors, up a flight of stairs and into a gallery to actually see the alleged time with one's own eyes. All it had was a MODEM socket hidden in the back of a 19U rack, with the wires in U.S. configuration rather than what we have in the U.K.
So, to change the time you could 'conveniently' solder up a lead that would actually connect to the box, telnet in, remembering to get the password right, then set the time zone using the obscure command procedure provided.
This would be a simple enough task, however, there would be two of these clocks and they would talk to each other. So changing the time on one would not be good enough, the other would correct it or set it ahead/back by another hour. For added convenience the other 'master' clock would be in an entirely different part of the building and need to stay 'on' the whole time.
When it comes to extreme horology, I think that the most stupendously over-the-top accurate timepieces should not actually be able to tell the time with something as cheap and tacky as a display. If the time does have to be displayed then it should be in UNIX epoch time as that is the most convenient for all concerned.