[LEAPSECS] "why time is difficult"

Zefram zefram at fysh.org
Wed Jan 4 07:04:17 EST 2012

Tony Finch wrote:

>Is a paper or slides available online?


There is no paper corresponding to the talk. I don't generally publish
slides, because they're rather uninformative on their own: I use them
lightly, as visual aids, rather than as the basis of a talk. However, I'm
attaching a version of the slides to this message, to compensate for the
video not having a clear image. (We in the Perl world are not great at
producing videos of talks.) These slides (the only version I can get to
right now) are from the earlier performance, at YAPC::Europe, and so show
older editions of the IERS bulletins, but otherwise have the same content.

-zefram
-------------- next part --------------
=== (title)






why time is difficult





Zefram <zefram at fysh.org>

http://search.cpan.org/~zefram/

http://www.fysh.org/~zefram/






=== (definitions of the second)



18xx the fraction 1/86_400 of the mean solar day.



1960 the fraction 1/31_556_925.9747 of the tropical year for
1900 January 0 at 12 hours ephemeris time.



1967 the duration of 9_192_631_770 periods of the radiation
corresponding to the transition between the two hyperfine
levels of the ground state of the caesium-133 atom.



1997 This definition refers to a caesium atom at rest at a
temperature of 0 K.



=== (early UTC summary)
leaps / TAIs
UTCs/TAIs Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1961 1.000000015 . . . . . . -.05 . . . . .
1962 1.000000013 . . . . . . . . . . . .
1963 . . . . . . . . . . +.1 . .
1964 1.000000015 . . +.1 . . . . +.1 . . . +.1
1965 . . +.1 . . . +.1 . +.1 . . . .
1966 1.000000030 . . . . . . . . . . . .
1967 . . . . . . . . . . . . .
1968 . . -.1 . . . . . . . . . .
1969 . . . . . . . . . . . . .
1970 . . . . . . . . . . . . .
1971 . . . . . . . . . . . . +.107758
1972 1.000000000 . . . . . +1 . . . . . +1
1973 . . . . . . . . . . . . +1
1974 . . . . . . . . . . . . +1
1975 . . . . . . . . . . . . +1
1976 . . . . . . . . . . . . +1
1977 . . . . . . . . . . . . +1
1978 . . . . . . . . . . . . +1
1979 . . . . . . . . . . . . +1
1980 . . . . . . . . . . . . .
=== (early leaps detail)

date leap/TAIs leap/UTCs

1961-07-31 -0.05 -0.049999999250000011~
1963-10-31 +0.1 +0.099999998700000017~
1964-03-31 +0.1 +0.099999998500000022~
1964-08-31 +0.1 +0.099999998500000022~
1964-12-31 +0.1 +0.099999998500000022~
1965-02-28 +0.1 +0.099999998500000022~
1965-06-30 +0.1 +0.099999998500000022~
1965-08-31 +0.1 +0.099999998500000022~
1968-01-31 -0.1 -0.099999997000000090~
1971-12-31 +0.107758 +0.107757996767260097~
1972-06-30 +1.0 +1.0
1972-12-31 +1.0 +1.0
1973-12-31 +1.0 +1.0
1974-12-31 +1.0 +1.0
1975-12-31 +1.0 +1.0
1976-12-31 +1.0 +1.0
1977-12-31 +1.0 +1.0
1978-12-31 +1.0 +1.0
1979-12-31 +1.0 +1.0

=== (measured Earth orientation parameters)


**********************************************************************
* *
* I E R S B U L L E T I N - A *
* *
* Rapid Service/Prediction of Earth Orientation *
**********************************************************************
11 August 2011 Vol. XXIV No. 032


IERS Rapid Service
MJD x error y error UT1-UTC error
" " " " s s
11 8 5 55778 0.11460 .00009 0.44326 .00009 -0.293613 0.000016
11 8 6 55779 0.11727 .00009 0.44283 .00009 -0.294026 0.000016
11 8 7 55780 0.11935 .00009 0.44242 .00009 -0.294177 0.000018
11 8 8 55781 0.12120 .00009 0.44188 .00009 -0.294131 0.000015
11 8 9 55782 0.12329 .00009 0.44119 .00009 -0.293988 0.000015
11 8 10 55783 0.12560 .00009 0.44058 .00009 -0.293829 0.000012
11 8 11 55784 0.12786 .00009 0.44012 .00009 -0.293695 0.000055


=== (predicted Earth orientation parameters)
PREDICTIONS:
MJD x(arcsec) y(arcsec) UT1-UTC(sec)
2011 8 12 55785 0.1299 0.4396 -0.29361
2011 8 13 55786 0.1318 0.4392 -0.29359
2011 8 14 55787 0.1335 0.4387 -0.29366
2011 8 15 55788 0.1352 0.4381 -0.29379
2011 8 16 55789 0.1367 0.4374 -0.29396
2011 8 17 55790 0.1382 0.4367 -0.29411
2011 8 18 55791 0.1397 0.4359 -0.29420
2011 8 19 55792 0.1411 0.4351 -0.29418
2011 8 20 55793 0.1426 0.4343 -0.29408
2011 8 21 55794 0.1439 0.4335 -0.29390
...
2012 8 1 56140 0.0873 0.3550 -0.55596
2012 8 2 56141 0.0876 0.3549 -0.55589
2012 8 3 56142 0.0878 0.3549 -0.55599
2012 8 4 56143 0.0881 0.3548 -0.55621
2012 8 5 56144 0.0883 0.3547 -0.55647
2012 8 6 56145 0.0885 0.3546 -0.55672
2012 8 7 56146 0.0887 0.3546 -0.55686
2012 8 8 56147 0.0889 0.3545 -0.55688
2012 8 9 56148 0.0891 0.3544 -0.55677
2012 8 10 56149 0.0893 0.3543 -0.55655
=== (IERS Bulletin C)

INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS)
SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE

Paris, 8 July 2011
Bulletin C 42

To authorities responsible
for the measurement and
distribution of time

INFORMATION ON UTC - TAI

NO positive leap second will be introduced at the end of December 2011.
The difference between Coordinated Universal Time UTC and the
International Atomic Time TAI is :

from 2009 January 1, 0h UTC, until further notice : UTC-TAI = -34 s

Daniel GAMBIS
Director
Earth Orientation Center of IERS
Observatoire de Paris, France
=== (relationships between modern time scales)

,-----------------. ,---------------. ,---------------------.
| coordinate time | | sidereal time | | apparent solar time |
| TCG | | ERA |--->| |
`-----------------' `---------------' `---------------------'
| | .
v v .
,-------------------. ,-----------------. .
| local proper time | ___| mean solar time | . . . .
| TT | | | UT1 |
`-------------------' | `-----------------'
| | |
v | v
,--------------------. | ,--------------------------.

| atomic realisation |___ |___| smoothed mean solar time |

| TAI | | | | UT1R UT2 UT2R |

`--------------------' | | `--------------------------'
| |
v v
,--------------. ,-----------------------.
| coordination | | smoothed coordination |
| UTC |--->| UTC-SLS |
`--------------' `-----------------------'
=== (links)








http://www.ucolick.org/~sla/leapsecs/timescales.html

http://leapsecond.com



Time::UTC
Time::UTC_SLS







===

More information about the LEAPSECS mailing list