moving optical clocks to test Einstein's general relativity
Updating the TVB mountaintop experiments with optical clocks on the continental divide here in Colorado...
This raises an interesting question - will this be sensitive enough to
detect tidal changes in gravity? Indeed, are caesium clocks able to do
this? We know of at least two pendulum clocks that could - the Shortt Free
Pendulum and the Fedchenko.
-----Original Message-----
From: Eric Scace via time-nuts time-nuts@lists.febo.com
Sent: Tuesday, November 7, 2023 2:57 AM
To: Time Nuts email list time-nuts@lists.febo.com
Cc: Eric Scace eric@scace.org
Subject: [time-nuts] moving optical clocks to test Einstein's general
relativity
Updating the TVB mountaintop experiments with optical clocks on the
continental divide here in Colorado...
<https://www.colorado.edu/ecee/2023/11/01/researchers-test-einsteins-predict
ions-general-relativity-atop-rocky-mountains>
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Cesium, not very good. Optical, sure.
The tidal wave shift of 3 dm requires the optical clocks, but it also
needs comparison with optical clock significantly different longitudal
or latitudal positions. The optical links of today is useful at their
10^-18 to 10^-19 floor. There is enough links in Europe between optical
clocks to maybe see this. They are about to connect INRIM to the French
grid, which leads up to SYRTE, shoots of to NPL and PTB. It will be
interesting to see if they see the 12h:is component in their data. I
will ask.
Cheers,
Magnus
On 2023-11-09 16:12, john.haine--- via time-nuts wrote:
This raises an interesting question - will this be sensitive enough to
detect tidal changes in gravity? Indeed, are caesium clocks able to do
this? We know of at least two pendulum clocks that could - the Shortt Free
Pendulum and the Fedchenko.
-----Original Message-----
From: Eric Scace via time-nuts time-nuts@lists.febo.com
Sent: Tuesday, November 7, 2023 2:57 AM
To: Time Nuts email list time-nuts@lists.febo.com
Cc: Eric Scace eric@scace.org
Subject: [time-nuts] moving optical clocks to test Einstein's general
relativity
Updating the TVB mountaintop experiments with optical clocks on the
continental divide here in Colorado...
<https://www.colorado.edu/ecee/2023/11/01/researchers-test-einsteins-predict
ions-general-relativity-atop-rocky-mountains>
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Eric,
Thanks for posting that link. Andrew Ludlow of NIST presented last week
at the SCPNT conference. The video / slides aren't up yet. Note their
mountain-valley experiments are direct comparison of optical clocks via
lasers which makes it possible to measure the effects of relativity on
clocks in real time. A related NIST experiment was done between two
Hawaiian islands a few years ago.
Without direct laser, copper, fiber, or RF links I had to drive my
clocks up a mountain, stay a day or two, and then return for the
comparison with clocks left down below. That round-trip method works
because 5071A are portable. Currently optical clocks are stationary or
"transportable", but not portable. By transportable I mean one can build
an optical clock as a self-contained instrument rack so that it can be
moved and set up at different locations. By portable I mean you can move
it while still running with no loss of lock. That allows one to "carry
the time" instead of just having a frequency standard.
John,
The magnitude of gravitational effects on earth are about 1e-13/km, or
1e-16/m, or 1e-19/mm. Solid earth tides are somewhere around 20 to 50 cm
so with optical clocks getting into -18 and -19 levels of precision this
starts to be a real effect. I'm pretty sure the experimenters simply use
a tide-free geoid model like EGM2008 to make it go away. Note if the
clocks are in a similar geographical area earth tides are common mode
and so you won't see them. For maximum effect you would want them 90
degrees latitude apart (10 000 km at the equator).
/tvb
On 11/6/2023 6:57 PM, Eric Scace via time-nuts wrote:
Updating the TVB mountaintop experiments with optical clocks on the continental divide here in Colorado...
On 11/9/2023 7:12 AM, john.haine--- via time-nuts wrote:
This raises an interesting question - will this be sensitive enough to
detect tidal changes in gravity? Indeed, are caesium clocks able to do
this? We know of at least two pendulum clocks that could - the Shortt Free
Pendulum and the Fedchenko.
On Thu, 9 Nov 2023 13:39:10 -0800
Tom Van Baak via time-nuts time-nuts@lists.febo.com wrote:
The magnitude of gravitational effects on earth are about 1e-13/km, or
1e-16/m, or 1e-19/mm. Solid earth tides are somewhere around 20 to 50 cm
so with optical clocks getting into -18 and -19 levels of precision this
starts to be a real effect. I'm pretty sure the experimenters simply use
a tide-free geoid model like EGM2008 to make it go away. Note if the
clocks are in a similar geographical area earth tides are common mode
and so you won't see them. For maximum effect you would want them 90
degrees latitude apart (10 000 km at the equator).
To add to this:
Current optical clock comparisons in Europe are done at the 1e-18 level.
I.e. where a height difference of 1cm is already significant. At these
comparisons not only solid earth tides show up, but also the gravitational
pull of sun and moon, as well as any change in the groundwater level of
more than 10-20cm. As optical clocks are inching towards 1e-19 stability
and higher uptimes where comparisons at this level become possible, it is
very likely that those contributing to TAI will, at some point, install
gravimeters next to the clocks to constantly account for the shift in
frequencies. Currently, our comparison capabilities are just not good enough
to justify this, but it will come. Probably in the near future even.
Attila Kinali
--
Science is made up of so many things that appear obvious
after they are explained. -- Pardot Kynes
Is a gravimeter with 1 uGal stability able to support the performance
of optical clocks? Maybe we must first relate the performance of
gravimeters with the performance of optical clocks.
Gravity measurements below 10e−9 g... https://arxiv.org/pdf/1809.04908.pdf
The PTB has made a transportable optical clock that fits in a truck:
https://www.ptb.de/cms/fileadmin/internet/presse_aktuelles/Presseinfos/2017/D1694_015_komprimierter.jpg
Geodesy and metrology with a transportable optical clock
https://arxiv.org/ftp/arxiv/papers/1705/1705.04089.pdf
On Mon, Nov 13, 2023 at 4:36 AM Attila Kinali via time-nuts
time-nuts@lists.febo.com wrote:
On Thu, 9 Nov 2023 13:39:10 -0800
Tom Van Baak via time-nuts time-nuts@lists.febo.com wrote:
The magnitude of gravitational effects on earth are about 1e-13/km, or
1e-16/m, or 1e-19/mm. Solid earth tides are somewhere around 20 to 50 cm
so with optical clocks getting into -18 and -19 levels of precision this
starts to be a real effect. I'm pretty sure the experimenters simply use
a tide-free geoid model like EGM2008 to make it go away. Note if the
clocks are in a similar geographical area earth tides are common mode
and so you won't see them. For maximum effect you would want them 90
degrees latitude apart (10 000 km at the equator).
To add to this:
Current optical clock comparisons in Europe are done at the 1e-18 level.
I.e. where a height difference of 1cm is already significant. At these
comparisons not only solid earth tides show up, but also the gravitational
pull of sun and moon, as well as any change in the groundwater level of
more than 10-20cm. As optical clocks are inching towards 1e-19 stability
and higher uptimes where comparisons at this level become possible, it is
very likely that those contributing to TAI will, at some point, install
gravimeters next to the clocks to constantly account for the shift in
frequencies. Currently, our comparison capabilities are just not good enough
to justify this, but it will come. Probably in the near future even.
Attila Kinali
--
Science is made up of so many things that appear obvious
after they are explained. -- Pardot Kynes
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
According to the Wikipedia, at earth surface, the gradient would be about 3.1 microgal per centimeter.
From: Azelio Boriani via time-nuts time-nuts@lists.febo.com
Sent: Monday, November 13, 2023 4:25:14 AM
To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com
Cc: Azelio Boriani azelio.boriani@gmail.com
Subject: [time-nuts] Re: moving optical clocks to test Einstein's general relativity
Is a gravimeter with 1 uGal stability able to support the performance
of optical clocks? Maybe we must first relate the performance of
gravimeters with the performance of optical clocks.
Gravity measurements below 10e−9 g... https://arxiv.org/pdf/1809.04908.pdf
The PTB has made a transportable optical clock that fits in a truck:
https://www.ptb.de/cms/fileadmin/internet/presse_aktuelles/Presseinfos/2017/D1694_015_komprimierter.jpg
Geodesy and metrology with a transportable optical clock
https://arxiv.org/ftp/arxiv/papers/1705/1705.04089.pdf
On Mon, Nov 13, 2023 at 4:36 AM Attila Kinali via time-nuts
time-nuts@lists.febo.com wrote:
On Thu, 9 Nov 2023 13:39:10 -0800
Tom Van Baak via time-nuts time-nuts@lists.febo.com wrote:
The magnitude of gravitational effects on earth are about 1e-13/km, or
1e-16/m, or 1e-19/mm. Solid earth tides are somewhere around 20 to 50 cm
so with optical clocks getting into -18 and -19 levels of precision this
starts to be a real effect. I'm pretty sure the experimenters simply use
a tide-free geoid model like EGM2008 to make it go away. Note if the
clocks are in a similar geographical area earth tides are common mode
and so you won't see them. For maximum effect you would want them 90
degrees latitude apart (10 000 km at the equator).
To add to this:
Current optical clock comparisons in Europe are done at the 1e-18 level.
I.e. where a height difference of 1cm is already significant. At these
comparisons not only solid earth tides show up, but also the gravitational
pull of sun and moon, as well as any change in the groundwater level of
more than 10-20cm. As optical clocks are inching towards 1e-19 stability
and higher uptimes where comparisons at this level become possible, it is
very likely that those contributing to TAI will, at some point, install
gravimeters next to the clocks to constantly account for the shift in
frequencies. Currently, our comparison capabilities are just not good enough
to justify this, but it will come. Probably in the near future even.
Attila Kinali
--
Science is made up of so many things that appear obvious
after they are explained. -- Pardot Kynes
time-nuts mailing list -- time-nuts@lists.febo.com
To unsubscribe send an email to time-nuts-leave@lists.febo.com
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Fascinating that the most accurate pendulum clock, the Fedchenko, was in effect a gravimeter so moon and sun gravitational effects were the ultimate limit on its stability. So will our ability to measure gravity be the ultimate limit on optical clock stability, unless we can put them in free fall?
-----Original Message-----
From: Azelio Boriani via time-nuts time-nuts@lists.febo.com
Sent: Monday, November 13, 2023 10:25 AM
To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com
Cc: Azelio Boriani azelio.boriani@gmail.com
Subject: [time-nuts] Re: moving optical clocks to test Einstein's general relativity
Is a gravimeter with 1 uGal stability able to support the performance of optical clocks? Maybe we must first relate the performance of gravimeters with the performance of optical clocks.
Gravity measurements below 10e−9 g... https://arxiv.org/pdf/1809.04908.pdf
The PTB has made a transportable optical clock that fits in a truck:
https://www.ptb.de/cms/fileadmin/internet/presse_aktuelles/Presseinfos/2017/D1694_015_komprimierter.jpg
Geodesy and metrology with a transportable optical clock https://arxiv.org/ftp/arxiv/papers/1705/1705.04089.pdf
On Mon, Nov 13, 2023 at 4:36 AM Attila Kinali via time-nuts time-nuts@lists.febo.com wrote:
On Thu, 9 Nov 2023 13:39:10 -0800
Tom Van Baak via time-nuts time-nuts@lists.febo.com wrote:
The magnitude of gravitational effects on earth are about 1e-13/km,
or 1e-16/m, or 1e-19/mm. Solid earth tides are somewhere around 20
to 50 cm so with optical clocks getting into -18 and -19 levels of
precision this starts to be a real effect. I'm pretty sure the
experimenters simply use a tide-free geoid model like EGM2008 to
make it go away. Note if the clocks are in a similar geographical
area earth tides are common mode and so you won't see them. For
maximum effect you would want them 90 degrees latitude apart (10 000 km at the equator).
To add to this:
Current optical clock comparisons in Europe are done at the 1e-18 level.
I.e. where a height difference of 1cm is already significant. At these
comparisons not only solid earth tides show up, but also the
gravitational pull of sun and moon, as well as any change in the
groundwater level of more than 10-20cm. As optical clocks are inching
towards 1e-19 stability and higher uptimes where comparisons at this
level become possible, it is very likely that those contributing to
TAI will, at some point, install gravimeters next to the clocks to
constantly account for the shift in frequencies. Currently, our
comparison capabilities are just not good enough to justify this, but it will come. Probably in the near future even.
Attila Kinali
--
Science is made up of so many things that appear obvious after they
are explained. -- Pardot Kynes
time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send
an email to time-nuts-leave@lists.febo.com
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Hi
It looks like few dm of height change is plenty to compensate for the typical changes in gravity. We already put clocks in fancy enclosures to compensate for temperature (and possibly humidity). Maybe we simply add an adjustable height table to that enclosure. Servo it using a fancy G meter to keep gravity a constant …..
Bob
On Nov 13, 2023, at 9:24 AM, john.haine--- via time-nuts time-nuts@lists.febo.com wrote:
Fascinating that the most accurate pendulum clock, the Fedchenko, was in effect a gravimeter so moon and sun gravitational effects were the ultimate limit on its stability. So will our ability to measure gravity be the ultimate limit on optical clock stability, unless we can put them in free fall?
-----Original Message-----
From: Azelio Boriani via time-nuts time-nuts@lists.febo.com
Sent: Monday, November 13, 2023 10:25 AM
To: Discussion of precise time and frequency measurement time-nuts@lists.febo.com
Cc: Azelio Boriani azelio.boriani@gmail.com
Subject: [time-nuts] Re: moving optical clocks to test Einstein's general relativity
Is a gravimeter with 1 uGal stability able to support the performance of optical clocks? Maybe we must first relate the performance of gravimeters with the performance of optical clocks.
Gravity measurements below 10e−9 g... https://arxiv.org/pdf/1809.04908.pdf
The PTB has made a transportable optical clock that fits in a truck:
https://www.ptb.de/cms/fileadmin/internet/presse_aktuelles/Presseinfos/2017/D1694_015_komprimierter.jpg
Geodesy and metrology with a transportable optical clock https://arxiv.org/ftp/arxiv/papers/1705/1705.04089.pdf
On Mon, Nov 13, 2023 at 4:36 AM Attila Kinali via time-nuts time-nuts@lists.febo.com wrote:
On Thu, 9 Nov 2023 13:39:10 -0800
Tom Van Baak via time-nuts time-nuts@lists.febo.com wrote:
The magnitude of gravitational effects on earth are about 1e-13/km,
or 1e-16/m, or 1e-19/mm. Solid earth tides are somewhere around 20
to 50 cm so with optical clocks getting into -18 and -19 levels of
precision this starts to be a real effect. I'm pretty sure the
experimenters simply use a tide-free geoid model like EGM2008 to
make it go away. Note if the clocks are in a similar geographical
area earth tides are common mode and so you won't see them. For
maximum effect you would want them 90 degrees latitude apart (10 000 km at the equator).
To add to this:
Current optical clock comparisons in Europe are done at the 1e-18 level.
I.e. where a height difference of 1cm is already significant. At these
comparisons not only solid earth tides show up, but also the
gravitational pull of sun and moon, as well as any change in the
groundwater level of more than 10-20cm. As optical clocks are inching
towards 1e-19 stability and higher uptimes where comparisons at this
level become possible, it is very likely that those contributing to
TAI will, at some point, install gravimeters next to the clocks to
constantly account for the shift in frequencies. Currently, our
comparison capabilities are just not good enough to justify this, but it will come. Probably in the near future even.
Attila Kinali
--
Science is made up of so many things that appear obvious after they
are explained. -- Pardot Kynes
time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe send
an email to time-nuts-leave@lists.febo.com
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Hi
I have just got my PRS10 Rubidium standard up and running, with GPS
disciplining and feel that it needs a dedicated Monitor and control
unit. A big thanks to Stanford Research Systems who have been most helpful.
I'm not sure how many are out there in use by Time Nuts
So , questions
1 Has anyone designed and built one already?
2 If not, how many would be interested in such a device if I have some
made. (probably a single PCB and a matching display bezel)
3 What features would users like?
On the latter question, I am thinking along the lines of using an
Arduino with 2 serial ports, basic 2x16 display as a starting point
One serial port would capture and display basic info from the GPS engine
The second would poll the PRS10 for lock and PPS status info and display
that alongside the GPS info
I should also be able to incorporate a routine for changing the PPS
output position to compensate for GPS engine cable lengths etc to make
for accurate timing
I could incorporate 10 MHz buffered distribution and 5MHz / 1MHz outputs
on the board
I would also incorporate simple visual monitoring LEDs fro GPS lock,
Rubidium Lock and Rubidium PPS discipline status going green after an
uptime of good PPS exceeding a number of integration time cycles
I have built and programmed units for other projects and while
development takes time, I can do this if there is demand.
see http://dc2light.co.uk/122GHz.html as an example
Contact me, on or off list if you are interested or can otherwise help
with ideas.
Mark gm4ism@yahoo.co.uk