A Portable Nuclear Clock

[GordMay]

Nuclear-based Solid-State Optical Clock [1]
Physicists have demonstrated all the ingredients of a nuclear clock [1] - a device that keeps time, by measuring tiny energy shifts, inside a thorium nucleus, with a laser device, called a frequency comb.

The researchers measured the frequency of light, that causes nuclei of the rare isotope thorium-229, to shift to a higher energy state [the ‘tick’ of the nuclear clock], with an accuracy that is 100,000 times greater than the previous best effort. They did this by synchronising the energy transition, with the tick, of the world’s most accurate clock [2].

Although the set-up isn’t, technically, a clock, because it hasn’t been used to measure time, such impressive results make the development of a nuclear clock seem possible.
The nuclear clock’s biggest potential advantage, over the atomic clock, is the combination of precision and stability. Particles in the nucleus are less sensitive than electrons to disturbances, such as electromagnetic fields — meaning, that a nuclear clock could be portable and robust. It becomes insensitive, in a way that is kind of unthinkable, in terms of how our clocks work today.

But more work must be done, before nuclear clocks can outperform optical atomic ones [which are currently accurate to 19 decimal places]. Researchers will explore whether keeping thorium-229 embedded in a crystal will make for the most accurate timekeeper, or whether trapping individual atoms will yield better results.

[1] “Frequency ratio of the 229mTh nuclear isomeric transition and the 87Sr atomic clock” ~ by Chuankun Zhang et al
➥ https://www.nature.com/articles/s415...xMrYopaGX-Q%3D

[2] Most accurate clock in history made by ‘quieting’ atoms
Strontium-based timepiece gains or loses only one second every 40 billion years. An optical atomic clock measures the energy transitions of strontium atoms, rather than the caesium atoms, used in the clocks that are the world’s official time-keepers.
➥ https://www.nature.com/articles/d41586-024-02199-7

[Hartleyg]

I'm thinking this falls into "News you WISH you could use", Gord


Hartley
S/V Atsa

[Jammer]

I dug around a while ago and there are some rubidium time sources out there that you can buy that are crazy accurate. They are unfortunately not packaged for the marine market, not low power, not 12v, etc.

I previously had a conventional oven-controlled time source in my lab that was accurate within about a second a year but that required a constant 25 watts or so.

The HAQ watch I wear every day is accurate to within about 1 second per month if worn continuously. I reset it twice a year at daylight savings time changeovers and when changing time zones during travel. More than accurate enough for any navigational purpose, including determination of longitude by celestial navigation. Batteries last over two years. I use it for scuba diving too.

[Starbuck]

John Harrison got there first. lol

[SeanPatrick]

Originally Posted by Jammer

The HAQ watch I wear every day is accurate to within about 1 second per month if worn continuously.

That is impressive! May I ask what model it is?

[Bowdrie]

A simple overview of a few HAQ watches.
https://wornandwound.com/guide-to-hi...z-haq-watches/
Some watches can receive time signals from WWV and other stations around the world and will update every day.
I've a Chelsea Quartz Chronometer with a true 24-hour movement, (the movement says, West Germany,) that gains ~15 seconds per year, (better to run a little fast,) that gives you time to listen to the time ticks and change the battery without needing to reset the hands, (i change it every Jan. 1st,) and it stays on GMT.
Some watches can be regulated if you're willing to have a pro with a machine spend some time with them.
Some internet sources claim my old Seiko 7548 divers watch can be regulated to less that 1/2 second per month, but I just keep track of the rate.

[Hartleyg]

The best way to get a time & frequency standard these days is to use a GPSDO. With one of those, you are within parts in 10^10 (.003 seconds/year). And you could have one aboard if you needed it!


https://www.amazon.com/10MHZ-Output-.../dp/B0BBM2WN3T


The best thing about these is there is no long-term drift to worry about.



Hartley
S/V Atsa

[Dockhead]

Originally Posted by Hartleyg

The best way to get a time & frequency standard these days is to use a GPSDO. With one of those, you are within parts in 10^10 (.003 seconds/year). And you could have one aboard if you needed it!

https://www.amazon.com/10MHZ-Output-.../dp/B0BBM2WN3T

The best thing about these is there is no long-term drift to worry about.

Hartley
S/V Atsa

You get the same result by looking at the time on your boat network, which also comes from GPS, so is also "GPSDO".


For someone who wants very precise time for celestial navigation in case the GPS system is disrupted or jammed, there are HAQ watches and clocks, which can be as accurate as 5 seconds a year. Only problem with THOSE is that they are electronic, so might be disrupted by an EMP.


So if you want navigation after the nuclear holocaust, you will need a mechanical chronometer, I guess.

[Jammer]

Originally Posted by SeanPatrick

That is impressive! May I ask what model it is?

It's a Certina DS Action Precidrive. I've had it for about five years. I'm not sure whether they're still available. Certina watches are made by the Swatch Group and are (or were at the time) not sold in the USA, at least not through "authorized" dealers, reportedly to avoid undercutting the pricing of more luxurious Swatch Group brands.

[Jammer]

I think the history of time and longitude is fascinating in many ways.

1767 was the year a marine chronometer was first used for navigation at sea. By 1825 these instruments were routinely fitted on English naval vessels. They were individually hand made up until the introduction of the mass-produced Hamilton Model 21 in 1942. Generally these instruments had (with rating) accuracy within one second per week.

But the lever escapement pocket watch was widely available by the 1820s and were used as deck watches. The railroad standard was that they had to be adjusted to within 30 seconds a week in 5 positions (face up, face down, crown up, crown to 3:00, crown to 9:00) without the benefit of rating, which was fairly easy to achieve. Actual accuracy was typically better and especially if careful about winding the watch at the same time each day and keeping it in a consistent orientation and using rating you could expect to get within 10 seconds a week. I know, I have one from 1891 and have experimented with it. On a typical voyage this is more accurate than shooting lunars, which were never accurate within less than about a minute. And indeed there were many voyages in the late 1800s where an ordinary pocket watch was the only source of time (and longitude). True marine chronometers were too expensive for many boats to afford.

By 1905 there was radio distribution of time so it didn't matter much any more. Traditions change slowly and marine chronometers were manufactured up through the end of the second world war.

A time error of 4 seconds is equal to one minute of longitude, or a nautical mile at the equator.

Mechanical wristwatches have never been as accurate as mechanical pocket watches due both to their small size and the tendency people have of moving their arms around. The standard for that now is roughly 5 seconds a day and you'll struggle to get that in most cases even with the premium brands.

[Dockhead]

Fantastic post; thanks for that.

My best sailing friend studied astrophysics as an undergrad and is crazy about celestial nav. When we were crossing the Atlantic together two years ago he did noon sights every day and all kinds of star and moon sights, and gave a class to the crew, which I sadly didn't have time to participate in.

He uses GPS time, however, which is cheating a bit, and I think maybe about getting a proper chronometer for him for Christmas. I just can't decide whether it needs to be fully mechanical or not.

[Jammer]

One alternative to consider is a Hamilton Model 22 Deck Watch. It has the external features of a marine chronometer -- larger than an ordinary pocket watch, external indication of winding state, locking set lever so the time can't be changed accidentally, some have gimballed boxes -- but doesn't have the mechanical complexity of a true chronometer.


They were used by the U.S. Navy during World War II as a backup source of time to the chronometer on larger ships and as the sole source of time on smaller ones, as there were simply not enough skilled workers to manufacture and maintain marine chronometers in sufficient quantity for the war effort. Accuracy is somewhat better than the pocket watches of the day but not as good as marine chronometers, think in terms of a second a day or so. They're less delicate and much cheaper to maintain as a result.


Joshua Slocum famously used his tin clock rather than his marine chronometer because he could not afford to have it serviced. The few places that specialize in service of marine chronometers today have a basic charge of over $600 -- that assuming that there's nothing actually wrong and all that's called for is cleaning and adjustment.

[Dockhead]

Originally Posted by Jammer

. . . The few places that specialize in service of marine chronometers today have a basic charge of over $600 -- that assuming that there's nothing actually wrong and all that's called for is cleaning and adjustment.

Yikes!


So maybe if the goal is to have the time no matter what, a HAQ watch or clock, stored in a Faraday cage would be more practical?


Interesting, would a Faraday cage protect against an EMP event?

[Wotname]

Originally Posted by Dockhead

........ and I think maybe about getting a proper chronometer for him for Christmas. I just can't decide whether it needs to be fully mechanical or not.

Well, a certified quartz chronometer will be significantly more accurate than a mechanical chronometer. Some autonomous quartz watches will be better than 30 seconds a year.

A standard mechanical chronometer daily rate is -4 sec to +6 sec / day.

I'm not sure exactly what you mean by a 'proper chronometer' as there are 4 types of chronometer recognised by COSC although only type 1 has an international standard (ISO 3159). The others are certified to in house COSC standards.

Type 1: Mechanical wristwatches
Type II: Pocket watches (Lépine or Savonette)
Type III: Fixed time devices (carriage clocks, desk clocks, etc.).
Type IV: Wrist watches with quartz oscillator

If your friend values accurate time keeping above anything else, quartz is the only option however if he values precision mechanical engineering then it is hard to pass by a mechanical watch.

The Master Chronometer standard of 0 to +5 sec / day was developed by Omega and METAS (Federal Institute of Metrology) with testing around anti-magnetic capabilities (to 15,000 Gauss).

Rolex has a Superlative Chronometer standard and while they don't publish the details of the standard and testing methods, they state an accuracy of between -2 and +2 seconds per day for a period of 5 years.

https://www.cosc.swiss/en
https://www.watchaffinity.co.uk/blog...ds%20per%20day.

FWIW, my EDC is Omega Seamaster Master Chronometer which when tested for the initial Master Chronometer certification had an average daily precision of +3.1 sec / day - this test is carried out over four days. The watch is placed in six different positions and two alternating temperature zones. It is also exposed to a magnetic field of 15,000 gauss. Chronometric precision is recorded each day. At the end of the four days, the results are used to calculate a daily average. The deviation precision between 100% and 33% of the power reserve was +1.9 sec / day.

Fast forward 4 years of every day wearing and I only check it at the end of Feb, April, June, September and November. I don't recall it being ever more than 20 or 30 seconds fast and never slow. I suppose I could rate it if I wanted to use it for celestial nav.

[Wotname]

Originally Posted by Jammer

... The few places that specialize in service of marine chronometers today have a basic charge of over $600 -- that assuming that there's nothing actually wrong and all that's called for is cleaning and adjustment.

Hmm...that seems high. Pre covid, my local Omega trained and authorised watchmaker was charging less than $150 (US) to service (clean, lubricate, adjust) for a Co-axial master chronometer movement. As I will need a service within a year or so, I'll call him next week to check his current fees. I might be in for a shock!