Visiting Greenwich
I am in London England at the moment, playing tourist with the rest of my
family. I want one day to be a visit to the National Maritime Museum at
Greenwich, which includes the Royal Observatory Greenwich. I am
particularly interested in seeing Harrison's H1 through H4, plus other
high-precision mechanical timekeepers (pendulum clocks, etc).
I know they are at the NMM - their web site shows some of them. But where
are they located on the site? The NMM has a large main building down near
the Thames, while the Royal Observatory and related buildings are on the
top of a hill further inland in Greenwich Park. Are the chronometers and
other precision timekeepers on display somewhere in the Royal Observatory,
or down in the main NMM building? I've spent an hour or two browsing web
sites without finding this particular bit of information.
I figure there must be list members who have visited the NMM, and know
where the precision timekeepers are actually displayed.
Thanks,
Dave
When I was there (10+ years ago) the timekeeping stuff was at the observatory, which is just a few minutes walk up from the NMM. Both sites are fascinating and well worth spending some time.
I took a tour boat to get to Greenwich from central London -- it's the end of the line and if you work the times right you can get on another one for the return trip. The boat ride was also well worth it.
Have fun!
John
On Jul 4, 2016, at 6:31 PM, Dave Martindale dave.martindale@gmail.com wrote:
I am in London England at the moment, playing tourist with the rest of my
family. I want one day to be a visit to the National Maritime Museum at
Greenwich, which includes the Royal Observatory Greenwich. I am
particularly interested in seeing Harrison's H1 through H4, plus other
high-precision mechanical timekeepers (pendulum clocks, etc).
I know they are at the NMM - their web site shows some of them. But where
are they located on the site? The NMM has a large main building down near
the Thames, while the Royal Observatory and related buildings are on the
top of a hill further inland in Greenwich Park. Are the chronometers and
other precision timekeepers on display somewhere in the Royal Observatory,
or down in the main NMM building? I've spent an hour or two browsing web
sites without finding this particular bit of information.
I figure there must be list members who have visited the NMM, and know
where the precision timekeepers are actually displayed.
Thanks,
Dave
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and follow the instructions there.
Dave, it's been a few years since I was there but the Harrison clocks
are not in the main part of the museum but in the Observatory which is a
bit to the South and East if I remember right. Both are well worth a
look, but the Harrisons are magic of course.
Dan
On 7/4/16 3:31 PM, Dave Martindale wrote:
I am in London England at the moment, playing tourist with the rest of my
family. I want one day to be a visit to the National Maritime Museum at
Greenwich, which includes the Royal Observatory Greenwich. I am
particularly interested in seeing Harrison's H1 through H4, plus other
high-precision mechanical timekeepers (pendulum clocks, etc).
I know they are at the NMM - their web site shows some of them. But where
are they located on the site? The NMM has a large main building down near
the Thames, while the Royal Observatory and related buildings are on the
top of a hill further inland in Greenwich Park. Are the chronometers and
other precision timekeepers on display somewhere in the Royal Observatory,
or down in the main NMM building? I've spent an hour or two browsing web
sites without finding this particular bit of information.
I figure there must be list members who have visited the NMM, and know
where the precision timekeepers are actually displayed.
Royal Observatory...
http://www.rmg.co.uk/see-do/we-recommend/attractions/john-harrisons-marine-timekeepers
http://www.rmg.co.uk/sites/default/files/rmg_map_2015_-_rog.pdf
One must, of course, take a picture with one foot in each hemisphere.
(Unless, you would follow the French, in which case, the Paris meridian
is the only true meridian, and then you'd have one meter in each
hemisphere...<grin>)
Do visit the main maritime museum down by the river. But the Harrison clocks are at the observatory, where the ball drops, about a 10 minute walk up the hill. Map here:
http://leapsecond.com/pages/meridian/
Besides H1-H4 see if you can get a peek at Clock B:
http://leapsecond.com/pend/clockb/
/tvb
----- Original Message -----
From: "Dave Martindale" dave.martindale@gmail.com
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Monday, July 04, 2016 3:31 PM
Subject: [time-nuts] Visiting Greenwich
I am in London England at the moment, playing tourist with the rest of my
family. I want one day to be a visit to the National Maritime Museum at
Greenwich, which includes the Royal Observatory Greenwich. I am
particularly interested in seeing Harrison's H1 through H4, plus other
high-precision mechanical timekeepers (pendulum clocks, etc).
I know they are at the NMM - their web site shows some of them. But where
are they located on the site? The NMM has a large main building down near
the Thames, while the Royal Observatory and related buildings are on the
top of a hill further inland in Greenwich Park. Are the chronometers and
other precision timekeepers on display somewhere in the Royal Observatory,
or down in the main NMM building? I've spent an hour or two browsing web
sites without finding this particular bit of information.
I figure there must be list members who have visited the NMM, and know
where the precision timekeepers are actually displayed.
Thanks,
Dave
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi Dave,
Yes, as many mentioned all the clocks are up the hill at the Observatory, and very much worth the trip. As you mention you are with your family, I would like to add that yes I did cajole my family to the NMM and the Observatory, but also to Bletchley Park (just a short train ride outside London) and Bletchley Park was easily the most memorable. There are wonderful volunteer guides, and many interesting devices that you can get up close to. Bletchley was more like visiting a working lab than a museum. I think every time nut would enjoy Bletchley quite a bit.
https://www.bletchleypark.org.uk/ https://www.bletchleypark.org.uk/
Cheers,
Bob
On Jul 4, 2016, at 6:31 PM, Dave Martindale dave.martindale@gmail.com wrote:
I am in London England at the moment, playing tourist with the rest of my
family. I want one day to be a visit to the National Maritime Museum at
Greenwich, which includes the Royal Observatory Greenwich. I am
particularly interested in seeing Harrison's H1 through H4, plus other
high-precision mechanical timekeepers (pendulum clocks, etc).
I know they are at the NMM - their web site shows some of them. But where
are they located on the site? The NMM has a large main building down near
the Thames, while the Royal Observatory and related buildings are on the
top of a hill further inland in Greenwich Park. Are the chronometers and
other precision timekeepers on display somewhere in the Royal Observatory,
or down in the main NMM building? I've spent an hour or two browsing web
sites without finding this particular bit of information.
I figure there must be list members who have visited the NMM, and know
where the precision timekeepers are actually displayed.
Thanks,
Dave
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Wouldn't that be "un pied dans chaque hemisphere" in France?
I visited the Greenwich observatory a number of years ago, but it was after
5 PM and all of the exhibits were closed for the day. So we only saw the
repeater clock and the meridian line. One interesting fact: A GPS
receiver will not agree with the line set into the concrete about where
zero degrees of longitude is located. The GPS prime meridian is somewhere
nearby, within the park, but not at the marked line.
An explanation for this (that I found at the time) is that the line in the
ground at the observatory is defined as zero longitude in whatever geodetic
ellipsoid and datum the British were using at the time. The GPS zero
longitude line is at zero in WGS84. Apparently WGS84 is defined to agree
with the older British datum in longitude at the equator, but the two
ellipsoids use different models of the earth's axis and so the two
zero-longitude meridians do not agree at Greenwich's latitude of ~50 N.
Google found this more recent article:
http://www.thegreenwichmeridian.org/tgm/articles.php?article=7 that has
more interesting (and more detailed) information about the difference in
the prime meridian definitions.
Dave
On Tuesday, 5 July 2016, jimlux jimlux@earthlink.net wrote:
One must, of course, take a picture with one foot in each hemisphere.
(Unless, you would follow the French, in which case, the Paris meridian is
the only true meridian, and then you'd have one meter in each
hemisphere...<grin>
Hi Dave,
Last year a more up to-date and highly-technical version of the meridian mystery was published:
"Why the Greenwich meridian moved"
http://link.springer.com/article/10.1007/s00190-015-0844-y
See especially figure 3. The PDF is here:
http://link.springer.com/content/pdf/10.1007%2Fs00190-015-0844-y.pdf
When I was in Greenwich last year I made these plots to show the old/tourist meridian (red x) and the true meridian (green x):
http://leapsecond.com/pages/meridian/map-100.gif
http://leapsecond.com/pages/meridian/map-101.gif
I also brought a laptop and 3 GPS receivers with me and collected 3 x 20 minutes of NMEA data while sitting on the old/tourist line. Sure enough, the mean error approached 102 meters:
http://leapsecond.com/pages/meridian/simul-5.gif
/tvb
----- Original Message -----
From: "Dave Martindale" dave.martindale@gmail.com
To: "Discussion of precise time and frequency measurement" time-nuts@febo.com
Sent: Monday, July 04, 2016 8:14 PM
Subject: Re: [time-nuts] Visiting Greenwich
Wouldn't that be "un pied dans chaque hemisphere" in France?
I visited the Greenwich observatory a number of years ago, but it was after
5 PM and all of the exhibits were closed for the day. So we only saw the
repeater clock and the meridian line. One interesting fact: A GPS
receiver will not agree with the line set into the concrete about where
zero degrees of longitude is located. The GPS prime meridian is somewhere
nearby, within the park, but not at the marked line.
An explanation for this (that I found at the time) is that the line in the
ground at the observatory is defined as zero longitude in whatever geodetic
ellipsoid and datum the British were using at the time. The GPS zero
longitude line is at zero in WGS84. Apparently WGS84 is defined to agree
with the older British datum in longitude at the equator, but the two
ellipsoids use different models of the earth's axis and so the two
zero-longitude meridians do not agree at Greenwich's latitude of ~50 N.
Google found this more recent article:
http://www.thegreenwichmeridian.org/tgm/articles.php?article=7 that has
more interesting (and more detailed) information about the difference in
the prime meridian definitions.
Dave
On Tuesday, 5 July 2016, jimlux jimlux@earthlink.net wrote:
One must, of course, take a picture with one foot in each hemisphere.
(Unless, you would follow the French, in which case, the Paris meridian is
the only true meridian, and then you'd have one meter in each
hemisphere...<grin>
Hi Dave,
The Harrisons are indeed at the observatory; also look for a regulator
pendulum clock in the octagon room. I'm not quite sure whether it was
running when I was there some years back.
Could it hurt to petition the observatory's powers-that-be for a little hut
or something at the ITRF meridian? :-)
If you do get to Bletchley Park, give the National Museum of Computing a
look-see as well (it's just a short walk). I believe both facilities have
benefited from recent infusions of money and support, which is great.
Cheers,
Peter
On Mon, 4 Jul 2016 19:01:45 -0700
Bob bob@marinelli.org wrote:
but also to Bletchley Park (just a short train ride outside London) and
Bletchley Park was easily the most memorable. There are wonderful volunteer
guides, and many interesting devices that you can get up close to.
Bletchley was more like visiting a working lab than a museum. I think every
time nut would enjoy Bletchley quite a bit.
https://www.bletchleypark.org.uk/ https://www.bletchleypark.org.uk/
I wouldn't call it a "short train ride outside London", but then,
I'm used to Swiss distances :-)
If you go to the Bletchley Park, also visit The National Museum of Computing
which is at the back of Bletchley Park ( http://www.tnmoc.org ). It's
a volunteer operated museum with lots of old computers. They also have
a working Colossus and a WITCH on display. If you talk to one of the
staff, he might show you the box with all the old crystals they have
collected and don't know what to do with :-)
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.