sla29970

8 ms·

1.
by sla29970 5y ago
During the discussions leading to the inception of the SI second the bigwig standards folks nixed the consideration of relativity, basically paraphrased as "If you physicists do not stop arguing about relativity we will never redefine
2.
by sla29970 5y ago
Strange is what they said just after the CCIR incepted leap seconds at the SI subcommittee in charge of the subject: "The CCIR may have overstepped its remit in defining the UTC" and "The process that led to UTC may have been
3.
by sla29970 5y ago
Have a look at the rate of earth rotation over the past 250 years where it is unclear that there is long term acceleration or deceleration. https://www.ucolick.org/~sla/leapsecs/dutc.html
4.
by sla29970 5y ago
It is possible 8 weeks in advance to predict the difference between UTC and UT1 and keep it less than 0.9 seconds. Nothing more is required by international agreement.
5.
by sla29970 5y ago
Lack of agreement; "smearing" is completely normal for answering "What time is it?", and completely wrong for applications requiring precise time.
6.
by sla29970 5y ago
In that case UTC is the wrong answer to the question "What timescale will produce robust results for this application?" As soon as leap seconds were recommended by the CCIR in 1970 radionavigation system administrators announced t
7.
by sla29970 5y ago
Look at the past 250 years where there is not really any clear indication of deceleration https://www.ucolick.org/~sla/leapsecs/dutc.html
8.
by sla29970 5y ago
Calculating time deltas between events is fundamental for GPS navigation, tracking an incoming missile, coordinating the action of robotic systems, synchronization of telecommunications, ...
9.
by sla29970 5y ago
"ignoring leap seconds" is equivalent to "using a time scale that does not conform to UTC". Time scales other than UTC have 86400 seconds in a day. UTC is the exception.
10.
by sla29970 5y ago
"My system clock is wrong, what action shall I take to correct it?" Common answers to that question are "step" or "smear". The notion that the clock could be wrong is not addressed in the design of most system
11.
by sla29970 5y ago
At the inception of leap seconds it was unclear how well they could be predicted, but the agreement required 8 weeks of notice as a minimum. Since the inception of leap seconds the rotation of the earth has accelerated, not slowed.
12.
by sla29970 5y ago
POSIX requires that we ignore leap seconds. POSIX had no alternatives to this choice because the information needed to do time right was not, and still is not, readily available via an authoritative and robust mechanism. No international re
13.
by sla29970 6y ago
A detailed look at the negotiations that led to leap seconds shows that they were not for maritime celestial navigation. During the process several different times the celestial navigation folks set a limit on how far radio broadcast time s
14.
by sla29970 8y ago
In 1950 astronomers pointed out that there would have to be two kinds of time, one to agree with calendar days and one to be as uniform as possible. Arguments over subsequent decades inexplicably decided that there could only be one kind of
15.
by sla29970 8y ago
Yes, roughly quadratic increase of LOD over the long term, but over short term more like a random walk. Right now the earth's crust is rotating faster than it did a century ago because things have speeded up. For a view over 2 millen
16.
by sla29970 10y ago
Remember February 30 1712? https://en.wikipedia.org/wiki/February_30#Swedish_calendar
17.
by sla29970 11y ago
The ITU has 4 methods for dealing with leap seconds, and method D is to change nothing. See the lack of consensus for any change in last week's presentations at http://www.itu.int/en/ITU-R/conferences/w
18.
by sla29970 11y ago
Dan Bernstein proposed it and Bradley White wrote the code in the time zone package used by Unix-like systems. The point of "right+gps" is that all of the pieces needed to implement such a scheme are already deployed and tested a
19.
by sla29970 14y ago
Some delegates to the ITU-R process have argued in the above fashion. Other delegates have come representing countries which want UTC to remain as a valid count of days in the calendar (for 86400 SI seconds is not the same as one rotation
20.
by sla29970 14y ago
There have been many defintions of UTC http://www.ucolick.org/~sla/leapsecs/timescales.html#UTC which do not agree. When an API does not match what the providers supply, which definition qualifies as "official"?
21.
by sla29970 14y ago
Read between the lines of http://www.bipm.org/cc/CCTF/Allowed/18/CCTF_09-27_note_on_UT... about what systems of time distribution already exist and which of those are approved for use by national and international agencies.
22.
by sla29970 14y ago
Getting a TAI timestamp is impossible because the BIPM (the authority that defines TAI) does not want TAI used for such purposes. Without approval from the authority nobody will undertake to construct the technology to provide TAI to an op