On 2020-08-24, Jakob Bohm <jb-use...@wisemo.com.invalid> wrote: > On 2020-08-24 16:07, William Unruh wrote: >> On 2020-08-24, Jakob Bohm <jb-use...@wisemo.com.invalid> wrote: >>> On 2020-08-24 12:51, Beth Connell wrote: >>>> Hi, >>>> I'm struggling to find any information on where the free NTP servers are >>>> geographically based. In particular, I'm wondering where Facebook, Google, >>>> Microsoft, etc are based within the UK. Just for curiousity, I'm wondering >>>> how this affects any interference to my location. >>>> >>>> Thanks >>>> >>> >>> All NTP time is GMT (now named UTC, after HM government dropped the >>> ball). The only geographic factor is the "ping time" to the time >>> server, the servers that are the most distant (longest ping) are the >>> GPS and Galileo satellites, that are hundreds or thousands of km from >>> the receiver, and use their own (non-NTP) protocols to correct for the >>> delay. >> >> It was renamed because UTC has nothing to do with Greenwich. For >> historical reasons, the time at Greenwich is the same as UTC. >> (Note that the prime meridian now runs through a garbage can in a park >> just south of the Thames rive in London and not along the line marked >> on the ground in Greenwich. No idea why you believe the govt dropped the >> ball. Because the location of Greenwich moves (plate techtonics) it >> would introduce inaccuracies into the definition of time if it were tied >> to Greenwich. Also, you cannot ping the sattelites. > > I used "ping time" as the popular name of the round trip time (as > actually measured by NTP implementations), and thus as a somewhat > vague reference to the equivalant satellite-to-ground time delay. > > As for the reference to HM Government, there was a rumor, many years > ago, that the budgets cuts caused the relevant time management job to > revert to the IERS in Paris, thus loosing Britain the honor of having > the time standard refer to the British victory at the Meridian > conference.
Is Britain really so bereft of self confidence and feelings of self worth that they have to hang onto symbols of their past (over 100 year old) glories? Time is universal, owned by the world. > > If the Greenwich observatory had still been in full operation, the > scientists running it would probably have applied the necessary > corrections for the ground shifting under their instruments, You simply cannot have a standard which drifts around. You need it to be fixed, eg to the stars. > rather than having the hole place demolished in favor of a symbolic > line on the ground. They would also probably have become the time > setting command center for the Galileo satellites that replaced their > daily dropping of an actual ball to signal exact meridian noon to > ships setting their navigation chronometers. Again, that daily dropping went outi (as a useful device) almost a hundred years ago, once radio was invented. (In Canada CBC still broadcasts "At the beginning of the long dash, the time is exactly 10 oclock Pacific Daylight time"-- I, just 37 min ago, heard it. I assume BBC has the equivalent.) That was a lot more accurate than the one second at best reaction time to the ball dropping. And even GPS with the 10m fuzzing was over a million times more accurate. And its lattitude is probably a million times more accurate than chronometric lattitude. Is there anyone on a ship these days that still knows how to use a sextant? > > > >>> >>> Another problem is if the NTP server is one of those that deliberately >>> return slightly wrong time before and after each leap second to "smooth >>> out" the leap, some of the companies you mention reportedly do that. I agree that that "solution" is pretty horrible. >>> >>> >>> Enjoy >>> >>> Jakob > > > Enjoy > > Jakob _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
