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Atomic Clocks

nist.gov

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Re: Atomic Clocks

#31

Post by tialaramex »

sakree wrote: post #29
tialaramex wrote: post #25

Earlier quoted context omitted.

Yeah, likewise the Breitling Emergency is big because it's an actual working 406 MHz Personal Locator Beacon. In principle that's all you need to have a rescue team come get you if you, I dunno, crashed your plane on a desert island or you broke your leg while hiking in Siberia, or whatever. Of course if you're the sort of person who wears a wristwatch which costs as much as a car you probably aren't doing anything l…

you would be surprised how large and passionate the watch community is. In the world of watches that breitling is big, but not really that big. It is quite a popular watch, and not that expensive : https://www.chrono24.com/breitling/emergency--mod21.htm?dose...

Notice that for the actual purpose of rescue only what they're calling "Gen2" actually works. The earlier devices which make up most of the linked examples are pretty, and would doubtless make interesting jewellery for a man at a society dinner or in the boardroom, but they do almost nothing if you're alone somewhere and need rescuing today.

Once upon a time, decades ago, a "beacon" is just a primitive radio transmitter which when activated produces a clearly man-made signal (it sounds like a siren basically if you're listening to it). This works pretty good if people nearby know to look for it. Then COSPAS SARSAT is a "peaceful use" satellite technology, put some satellites up above the Earth, they relay the chosen emergency frequencies and now a human operator can "hear" that beacon from hundreds of miles away. So that's all the original Emergency does. Rescue this way was sometimes a long-shot, but you did not have better options.

But obviously now we can do a lot better, so eventually COSPAS SARSAT deprecated and then eventually eliminated that relay technology in favour of 406 MHz digital beacons. So now it can tell which beacon has been triggered, and you can add stuff like contact details to a database for the rescuers. This way when they get a beacon they can see the signal is Steve Smith, solo mountaineer, here's a contact number for Steve's mum, so before we commit a mountain rescue team to 18 hours of work we can verify whether Steve is currently up a mountain [maybe in urgent need of rescue] or whether he lost that beacon last month and is at home now watching Netflix.

Your point is well taken - I just wanted to be absolutely clear for anybody who might get one of these that the original Emergency is now basically just pretty and only a modern "Gen2" Emergency "works" for its stated purpose.

Re: Atomic Clocks

#32

Post by nofunsir »

tomcam wrote: post #15

Long before most of you were born there was a special number you could call to get the time here in the USA. It would give you a localized time every 10 seconds. It was considered an authoritative value, but I knew that normal analog clocks drifted a fair amount, and I was fascinated by the Time voice. There was also a special number to dial that was called Information. When I was about 12, I suddenly thought that’s…

Listen to "What Time Is It?" by Ken Nordine. It's a treat.

Re: Atomic Clocks

#33

Post by rcxdude »

isolli wrote: post #7
r3trohack3r wrote: post #4

> Today’s best atomic clocks are billions of times more accurate and precise than any other type of clock. If they had been running since the Big Bang, 13.8 billion years ago, they would have lost or gained less than a second. Absolutely incredible, but then confused by the next assertion that is made without context: > New kinds of clocks may soon open up capabilities that previous generations could only dream about…

What are these atomic clocks measured against?

Generally, other atomic clocks. The fact they they tick consistently compared to each other is the main thing (though at these scales, you need to account for time dilation!).

Re: Atomic Clocks

#34

Post by atypeoferror »

I recently bought my first not-super-cheap watch, and found out that all around the world there radio stations which broadcast the atomic clock time that a lot of clocks/watches listen to.

After setting the time zone (I guess this also changes the frequency that it listens on) it starts to sync itself using that signal. It is also solar-charging - so this basically means that I never have to touch it. Although it's an analog watch, because of this sync, it correctly handles DST, the date window (including leap year) - basically I never have to touch it again until it breaks . All without bluetooth or internet connection - pretty cool I think.

Casio Oceanus t200 for anyone that cares.

Re: Atomic Clocks

#35

Post by inigyou »

globular-toast wrote: post #23
tomcam wrote: post #15

Long before most of you were born there was a special number you could call to get the time here in the USA. It would give you a localized time every 10 seconds. It was considered an authoritative value, but I knew that normal analog clocks drifted a fair amount, and I was fascinated by the Time voice. There was also a special number to dial that was called Information. When I was about 12, I suddenly thought that’s…

That's brilliant. Sometimes talking to real humans is great. It reminds me of two things. When I was a child I was given a postage stamp and wrote a letter to "Wallace and Gromit Ltd" and posted it. Remarkably, I got a reply from Aardman Animations with a card signed by Nick Park himself. Someone at Royal Mail obviously understood and looked up the real address of the studio. Later as a teen I noticed the clock on ou…

When I was about 10 I wrote a letter to Microsoft and they sent me back a package of Visual Studio (real licensed edition that didn't display a dialog box every time you ran a compiled program!) and, on two CDs and in HTML Help format, MSDN Library.

Re: Atomic Clocks

#36

Post by inigyou »

NitpickLawyer wrote: post #11
mullingitover wrote: post #8

Earlier quoted context omitted.

Pretty sure you can rig something far better than radar if you have the ability to detect extremely tiny gravitational waves via an array of hyper-accurate clocks.

> detect extremely tiny gravitational waves via an array of hyper-accurate clocks. I wonder how tiny is feasible. Would it get to a level of accuracy where you could detect neutrinos? We know they have some (v tiny) mass, so it should in theory be detectable that way?

Moving objects don't emit gravitational waves though. They have to be orbiting.

Re: Atomic Clocks

#37

Post by inigyou »

Schlagbohrer wrote: post #16

Not many people know NIST offers a cookbook for perfectly calibrated food https://www.nist.gov/pml/owm/metric-si/metric-kitchen/metric...

Also known as an ordinary recipe everywhere else.

Well, recipes do often use measurements like teaspoons and cups, but they have straightforward metric equivalents - a teaspoon being 5mL and a cup 250mL.

Re: Atomic Clocks

#38

Post by inigyou »

Schlagbohrer wrote: post #13

NIST is a great example of a true Public Good. Also, has anyone else ever used their Randomness Beacon? I once used it to settle an argument in a book club over which book to read next. It's basically a very fancy and high tech coin flip. https://csrc.nist.gov/projects/interoperable-randomness-beac...

As long as we forget that little thing called Dual_EC_DRBG, right?

Re: Atomic Clocks

#39

Post by actionfromafar »

inigyou wrote: post #36
NitpickLawyer wrote: post #11

Earlier quoted context omitted.

> detect extremely tiny gravitational waves via an array of hyper-accurate clocks. I wonder how tiny is feasible. Would it get to a level of accuracy where you could detect neutrinos? We know they have some (v tiny) mass, so it should in theory be detectable that way?

Moving objects don't emit gravitational waves though. They have to be orbiting.

1. Isn't everything orbiting something?

2. If a black hole passed us by, no gravitional wave?

Re: Atomic Clocks

#40

Post by fipar »

tomcam wrote: post #15

Long before most of you were born there was a special number you could call to get the time here in the USA. It would give you a localized time every 10 seconds. It was considered an authoritative value, but I knew that normal analog clocks drifted a fair amount, and I was fascinated by the Time voice. There was also a special number to dial that was called Information. When I was about 12, I suddenly thought that’s…

We had a similar time service in Uruguay and, whenever we had an important appointment (e.g., a medical one) we’d call the number to make sure our clocks and watches were on time.

It was a female voice that said something that could be translated to “the signal will mark it is ,” and, the funny thing is, between the way it had been recorded and the fact that signal (señal) and lady (señora) can sound very similar in Spanish when over the phone and followed by a vowel (“indicará” for will mark in this case), a lot of us thought it said “the lady will mark” and, as a little kid, I thought there was an old time-keeping lady on whom we all depended to be in sync. Miss NTP I guess!

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