John, sir:
>To me this seems totally irrelevant. There is no long term value in >defining
>the year to be anything in particular. It is an imprecise >measurement, good
>enough for everyday use. I do not intend to push things 'beyond recognition'
>BUT science believe and insists on PRECISION. In day-to-day use we ignore a
>lot! By pointing that Mean Year value can get stabilised at 365.2421875 days
>(for Year 2007) or any Era start is the moot point.
Regards,Brij Bhushan Vij (MJD 2454361)/630+D-260 G (Monday, 2007 September 17
H 21:11(decimal) ISTAa Nau Bhadra Kritvo Yantu Vishwatah -Rg Veda Jan:31;
Feb:29; Mar:31; Apr:30; May:31; Jun:30 Jul:30; Aug:31; Sep:30; Oct:31; Nov:30;
Dec:30 (365th day of Year is World Day) HOME PAGE:
http://www.brijvij.com/******As per Kali V-GRhymeCalendaar*****"Koi bhi
cheshtha vayarth nahin hoti, purshaarth karne mein hai"Contact # 011-9818775933
(M)001(201)962-3708(when in US)> Date: Sun, 16 Sep 2007 13:03:54 -0400> From:
[EMAIL PROTECTED]> Subject: [USMA:39436] Re: On re-defining YEAR RE: Re: Year>
To: [email protected]> > To me this seems totally irrelevant. There is no long
term value in > defining the year to be anything in particular. It is an
imprecise > measurement, good enough for everyday use. If people aren't even >
concerned about the difference between a US gallon and a UK gallon, they > are
surely not going to worry about a few seconds in their ages.> > Granted, by
accurately defining a year it may be possible to accurately > define a light
year. But a light year is only useful in measurements at > astronomical scales
and we do not have the technology to determine such > distances to anything
approaching 6 or more significant digits of > accuracy. Two significant digits
is about as good as we can get, and > also quite sufficient.> > Furthermore, a
year is only relevant to terrestrial measurements. While > it is true right now
that we all happen to live in terrestrial > environments, it is also likely
that we shall establish settlements > elsewhere in the future. What concern
will Mars colonists have with the > Earth year being 365.242189669781 days?
Bear in mind that those days > are Earth days which do not correspond to the
slightly longer Mars days > anyway.> > Similarly, redefining the unit of length
in terms of the distance > subtended at the surface of the Earth by a certain
angle is irrelevant > to extraterrestrial locales, even though it may be useful
here for the > several centuries. Indeed, that was the method used to define
the metre > in the first place but that definition was abandoned a long time
ago.> > With all due respect, this topic is just noise and has no bearing on
our > group goal of promoting the adoption and use if SI.> > > > Brij Bhushan
Vij wrote:> > John and all:> >> > *REVISING** Average Mean Atomic Year Value
(Y_2007 ):* > >> > According to <_http://en.wikipedia.org/wiki/Tropical_year_>:
The > > current values for Year and their annual change in the time of return >
> to the cardinal ecliptic points are: (1) vernal equinox: 365.24237404 > > +
0.00000010338×a days; (2) northern solstice: 365.24162603 + > > 0.00000000650×a
days; (3) autumn equinox: 365.24201767 − > > 0.00000023150×a days; and (4)
southern solstice: 365.24274049 − > > 0.00000012446×a days, where a is number
of years after Y_2000 . I > > consider the YEAR length can be fixed at the
Average Mean Atomic Year > > i.e. [365.24237404 + 365.24162603 + 365.24201767 +
365.24274049] / 4 > > =365.2421895575 days. Astronomers, however, have fixed
the Year value, > > Y_2000 = 365.242189669781 days. This during the past
century, Y_1900 > > was 365d 5h 48m 45s.9747 i.e. 365.24219878125 > > days”. >
>> > In my works http://www.brijvij.com/, I have aimed to get Mean Year > >
value at: (365+31/128) = 365.2421875 days, using div.4/skip 128^th > > years
(for Leap Days count); or (7*128) =896-years/159 LWks to give > > Mean Year =
(365+159/896) = 365.2421875 days =7*(52+1/6+29/2688). I > > now propose to fix,
Y _2007 = 365.2421875 atomic-days and align with > > Y_2000 = 365.242189669781
days, thus *ratio 365.242189669781/ > > 365.2421875
=1.000000005940663686338260144168*. This also, mean that > > ‘New Atomic Day
=86400.00051327334 25 atomic second’; each atomic > > second of 794243389646333
cycles of Cs-133 at hyperfine levels.> > Accordingly, decimal second
(sd)=1/240000th of atomic day =3309347457 > > periods of radiations of Cs-133
at defined hyperfine levels.> > Regards,> > Brij Bhushan Vij> >> > (MJD
2454360)/630+D-259 G (Sunday, 2007 September 16 H 19:09 (decimal) IST> > Aa Nau
Bhadra Kritvo Yantu Vishwatah -Rg Veda> > Jan:31; Feb:29; Mar:31; Apr:30;
May:31; Jun:30> > Jul:30; Aug:31; Sep:30; Oct:31; Nov:30; Dec:30> > (365th day
of Year is World Day)> > HOME PAGE: http://www.brijvij.com/> > ******As per
Kali V-GRhymeCalendaar*****> > "Koi bhi cheshtha vayarth nahin hoti, purshaarth
karne mein hai"> > Contact # 011-9818775933 (M)> > 001(201)962-3708(when in
US)> >> > > From: [EMAIL PROTECTED]> > > To: [email protected]> > > Subject:
[USMA:39433] Re: Year> > > Date: Sun, 16 Sep 2007 03:13:17 -0700> > >> > >
Also, http://en.wikipedia.org/wiki/Annum defines the unit "annum", > > symbol>
> > "a", with metric multiples kiloannum, megaannum, gigaannum, etc. It > >
states> > > that the symbol "yr" is deprecated.> > > --> > > John Hynes> > >
San Francisco> > > www.decimaltime.org> > > 2007 Sept. 16.425 UT> > >> > >
----- Original Message -----> > > From: "John Hynes" <[EMAIL PROTECTED]>> > >
To: "U.S. Metric Association" <[email protected]>> > > Sent: Sunday, September
16, 2007 2:54 AM> > > Subject: [USMA:39432] Year> > >> > >> > > > Going back to
the discussion on the "year" unit, I found an > > interesting> > > > document
called "The Unified Code for Units of Measure" at> > > >
http://aurora.rg.iupui.edu/UCUM/ucum.html#section-introduction> > > >> > > >
"Table 5: Other units from ISO 1000, ISO 2955, and some from ANSI > > X3.50.">
> > > includes:> > > >> > > > name | kind of quantity | print | c/s | c/i | M |
definition value |> > > > definition unit> > > > tropical year | time | at |
a_t | ANN_T | no | 365.24219 | do> > > > mean Julian year | time | aj | a_j |
ANN_J | no | 365.25 | do> > > > mean Gregorian year | time | ag | a_g | ANN_G |
no | 365.2425 | do> > > > year | time | a | a | ANN | no | 1 | a_j> > > >> > >
> "print" symbols include non-ASCII characters, such as subscripts, > > while>
> > > c/s and c/i are ASCII variants. M means "metric", which these > >
definitely> > > > are not. I think that someone here mentioned the symbol "a"
used with> > > > subscripts, so perhaps they were referring to a common source.
The> > > > following section is pertinent:> > > > ----------------> > > > ANSI
X3.50 had two different series of symbols for the units of > > time, the> > > >
ones from ISO 2955 as adopted by The Unified Code for Units of > > Measure and>
> > > the symbols "yr" "mo" "wk" "hr" and "sec" while "do" and "min" were> > >
> defined twice. The Unified Code for Units of Measure does not > > define
these> > > > synonyms of ISO 2955 symbols, but does adopt those units from ANSI
> > X3.50> > > > that are not part of ISO 2955, namely "mo" and "wk" Month and
week > > are> > > > useful units mainly in business or clinical medicine.> > >
>> > > > The semantics of the units of time is difficult to capture. The> > > >
difficulties start with the day: There is the sidereal and the > > solar day> >
> > that depend on the earth's rotation. The earth's rotation is variable> > >
> during one day and is continually slowing down in the long run. > > The
usual> > > > subdivisions of the day in 24 hours of 60 minutes and 60 seconds>
> > > originated in Babylonia. The earth's rotation was too inexact to > >
measure> > > > time, which is why the 11th CGPM (1954) defined the second based
on a> > > > standarized historical tropical year (see below) which was later >
> (13th> > > > CGPM 1967-1968) replaced by frequency measurement. Thus the
second > > came to> > > > be the base unit of time and the day is now 864000 s
exactly with the> > > > Universal Coordinated Time (UTC) adding leap seconds
every now and > > then.> > > >> > > > For the year we have to distinguish the
"tropical" (solar, > > sidereal) year> > > > from the calendar year. And both
are difficult. The tropical year > > is the> > > > year defined by time the
earth travels around the sun. This is > > difficult> > > > to measure and
varies over time. Around 1900 it was 365.242196 do,> > > > currently it is
365.242190 do and around 2100 it will be > > 365.242184 d. In> > > > addition
these durations are averages. The actual length of each > > year may> > > >
vary by several minutes due to the gravitational influence of other> > > >
planets. Thus there is quite a high uncertainty already in the fourth> > > >
decimal digit.> > > >> > > > The calendar year is also difficult because there
is the Julian > > calendar> > > > (Sosigenes of Alexandria and Julius Caesar,
45 BC) with a slightly > > too> > > > long year of 365.25 do that causes the
calendar to be one day > > ahead of the> > > > tropical year in 128 years. The
Gregorian calendar (Christopher > > Clavius> > > > 1537-1612 and Pope Gregory
XIII 1545-1563) leaves out three leap > > years in> > > > 400 years (let n be
the year number, the leap year is dropped if n > > mod 100> > > > = 0 but not n
mod 400 = 0.) The Gregorian mean year is thus > > 365.2425 do.> > > > This leap
year arithmetic seems to be too much even for > > astronomers, which> > > > is
why the light year ends up being defined based on the Julian > > year [NIST> >
> > Sp. Pub. 811, 1995 Edition]. For this reason The Unified Code for > > Units
of> > > > Measure defines Tropical, Julian and Gregorian year by means of> > >
> subscripts, but assigns the default year symbol to the Julian year.> > > >> >
> > The week is 7 days, this is a biblic truth we can count on (it is > >
actually> > > > quite plausible that the week of seven days originated in > >
Babylonia and> > > > entered Jewish tradition during the Babylonian exile.)> >
> >> > > > The difficultiy continues with the month. The lunar (so called > >
"synodal"> > > > month is variable. Around 1900 it was 29.5305886 do currently
it is> > > > 29.5305889 do and in 2100 it will be 29.5305891 do, which we > >
fixate in the> > > > 5th decimal digit with a considerable uncertainty. The
calendar > > month is> > > > difficult because of the uneven distribution of
days in a month > > over the> > > > year, and because of the two different
calendar years. But we will > > usually> > > > use the mean calendar month,
which is the Julian calendar year > > divided by> > > > 12.> > > >> > > > As a
conclusion, great care has to be taken when the "customary > > units" of> > > >
time are used to measure time. The SI has fixated the second which > > should>
> > > be used whenever accuracy is required. For business purposes the > >
Julian> > > > calendar is sufficient especially since the notion of the
Work-Day > > (vs.> > > > Holiday) is more important than the imprecision over
128 years. > > [Sources:> > > > "Calendar" Britannica> > > > > >
Online.http://www.eb.com:180/cgi-bin/g?DocF=macro/5000/98/toc.html. Claus> > >
> Tondering, Frequently asked questions about calendars. Part 1. 1998.> > > >
http://www.pip.dknet.dk/~c-t/calendar.faq1.txt]> > > >> > > >
-----------------> > > >> > > > --> > > > John Hynes> > > > San Francisco> > >
> www.decimaltime.org> > > > 2007 Sept. 16.410 UT> > > >> > > >> > > >> > > >>
> > >> > >> >> >> >
------------------------------------------------------------------------> >
Kick back and relax with hot games and cool activities at the > > Messenger
Café. Play now! > >
<http://www.cafemessenger.com?ocid=TXT_TAGLM_SeptWLtagline>> >
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