[time-nuts] Re: Where do people get the time?

[Adrian Godwin]

Thanks for that, an enjoyable lecture !

Does anyone know more about the question at  1:05:50 - a difference between
GMT and 'London time' used by airlines ? The questioner seemed sure it
wasn't daylight savings, but I live only half a degree east of the meridian
and am not aware of any other timezone.


On Sun, Jan 2, 2022 at 4:51 AM Tom Van Baak <tvb at leapsecond.com> wrote:

> Hal Murray wrote:
>  > where do you get the time?
>
> The new years celebrations last night remind me of another source of
> time: time balls.
>
> Although a bit of nostalgia these days or even a joke, time balls were
> clever, precise, and a critical part of naval infrastructure in the 19th
> century, lasting well into the 20th century, and still operational daily
> in Greenwich (not right now due to refurbishment). It falls into the
> category of "time dissemination"; you know, WWV, GPS, UTC, NTP, and all.
>
> The sound of church bells gave approximate time, partly because their
> use case didn't require high precision and partly because sound travels
> only one foot per millisecond. Related: starter pistols at track events;
> clapperboards on movie sets; timing thunderstorms with lightning.
>
> But light, as you know, travels literally a million times faster, one
> foot per nanosecond. Thus the optics of a time ball solved the latency
> problem of setting chronometers onboard ships in the bay. Fun fact: The
> Beagle (of Charles Darwin fame) carried 25 chronometers. This is every
> time nuts justification for having so many clocks at home. ;-)
>
> ----
>
> If you want a fun timely project I'm waiting for a time nut to make a
> GPS controlled desktop Arduino time ball. With clever design it could
> re-arm itself and mark the precise time as often as once a minute
> instead of once an hour or once a day.
>
> Alternatively, if you allow the ball to free-fall 16 feet it takes
> exactly one second. With clever design and multiple balls you could make
> a continuous 1BPS (one ball per second) clock where each ground hit
> exactly triggers the next ball release. This would get you front page on
> hackaday. Lots of time nut fun looking at jitter and drift, at
> temperature and pressure effects. And of course the ADEV would be
> priceless. Seriously, some mechanical clocks teach you more about the
> art of clock measurement and data analysis than a boring atomic
> frequency standard or GPSDO.
>
> Welcome to 2022, and may we all have a better time this year.
>
> /tvb
>
> Time ball rabbit hole:
>
> https://en.wikipedia.org/wiki/List_of_chronometers_on_HMS_Beagle
> https://en.wikipedia.org/wiki/Ship%27s_chronometer_from_HMS_Beagle
>
> https://en.wikipedia.org/wiki/Time_ball
>
> https://www.bbc.com/news/uk-england-humber-58559814
> "Time balls: The rise and fall of a timekeeping icon"
>
>
> https://www.nytimes.com/2004/12/30/opinion/a-brief-history-of-time-balls.html
> "A Brief History of Time Balls"
>
>
> https://nmmc.co.uk/wp-content/uploads/2016/04/120330_The_Falmouth_Timeball.pdf
> "The Falmouth Time Ball", by Ronald S Hawkins  [ superb historical &
> technical details ]
>
>
> https://hs-ny.org/schedule/2019/5/6/the-ups-and-downs-of-the-greenwich-time-ball-an-overview-of-its-history-mechanics-and-upkeep
> https://youtu.be/ubvmCWet6iU
>
> https://journals.sagepub.com/doi/abs/10.1177/002182868101200301
> "The First Time Balls"
> Journal for the History of Astronomy
>
> https://adsabs.harvard.edu/full/1970JBAA...80..208H
> "The Story of Greenwich Time"
>
>
> https://www.bbc.com/travel/article/20191212-the-invention-that-inspired-a-new-york-tradition
> "The invention that inspired a New York tradition"
>
>
> https://www.xyht.com/gnsslocation-tech/the-clocks-at-the-center-of-the-universe/
> "The Clock(s) at the Center of the Universe"
>
> ----
>
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