Re: Twins paradox debunked and broken down

Michael Moroney wrote:


Wrong. The opposite is true. Every so often they'll add a "leap second"
to a day, usually on 31 DEC just before midnight UTC. This is because the
length of a given day (1 Earth rotation) isn't exactly the same as every other day, and the errors accumulate. Atomic clocks are more accurate than the Earth itself is as a clock.

When this happens, you'll see the display on a properly synchronized clock
go in the sequence:
...
23:59:57
23:59:58
23:59:59
23:59:60
00:00:00
00:00:01
...

I don't know if a "leap second" is scheduled for this year, but if so, and
you can't find anything better to do on New Years Eve, you can watch an
atomic clock do this. I believe any PC running NTP will do this. Remember it happens at midnight UTC so you can do this and still go to
your New Years Eve party, unless you're in Europe in the timezone with
offset +0.

INTERNATIONAL EARTH ROTATION AND REFERENCE SYSTEMS SERVICE (IERS)

SERVICE INTERNATIONAL DE LA ROTATION TERRESTRE ET DES SYSTEMES DE REFERENCE

SERVICE DE LA ROTATION TERRESTRE
OBSERVATOIRE DE PARIS
61, Av. de l'Observatoire 75014 PARIS (France)
Tel. : 33 (0) 1 40 51 22 26
FAX : 33 (0) 1 40 51 22 91
e-mail : services.iers@xxxxxxxx
http://hpiers.obspm.fr/eop-pc

Paris, 4 July 2008

Bulletin C 36

To authorities responsible
for the measurement and
distribution of time


UTC TIME STEP
on the 1st of January 2009


A positive leap second will be introduced at the end of December 2008.
The sequence of dates of the UTC second markers will be:

2008 December 31, 23h 59m 59s
2008 December 31, 23h 59m 60s
2009 January 1, 0h 0m 0s

The difference between UTC and the International Atomic Time TAI is:

from 2006 January 1, 0h UTC, to 2009 January 1 0h UTC : UTC-TAI = - 33s
from 2009 January 1, 0h UTC, until further notice : UTC-TAI = - 34s

Leap seconds can be introduced in UTC at the end of the months of December
or June, depending on the evolution of UT1-TAI. Bulletin C is mailed every
six months, either to announce a time step in UTC or to confirm that there
will be no time step at the next possible date.



Daniel GAMBIS
Head
Earth Orientation Center of IERS
Observatoire de Paris, France

.

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