Quote:
Originally Posted by Tropo-Bob
Gary,
Thank you for your comprehensive and thoughtful answer.
I appreciate you taking the time to reply.
|
Thanks Bob & Dean,
One of the other subtle phenomena I forget to mention was the Earth's rotational speed.
There is a body known as the International Earth Rotation and Reference
Service (IERS) that keeps tabs on the Earth's irregular rotational speed.
See
http://www.iers.org/IERS/EN/Home/home_node.html
Now and then they advise on the insertion of an additional leap second
during the year. Though leap seconds could in theory both be added
or subtracted, in practice since we adopted atomic UTC time keeping in
1972, 26 have been inserted at various times. So the Earth's rotation
has been slowing in recent years. The most recent leap second
that was added took place in June 2015. There were 61 seconds in that
particular minute.
The idea of the leap second is to try and keep atomic time, UTC, within
0.9 of a second of mean solar time, what is designated as UT1.
In some sectors of human endeavour, the leap second has become a bit
of a nuisance. Consider computer networks or air traffic control systems
as a couple of examples.
Hence there has been debate in recent years as to whether to get rid of
them or not.
There was a session of the World Radiocommunication Conference held
last November in Geneva where they decided to put off
the decision about eliminating leaps second or not
until the next conference in 2023.
See
http://spectrum.ieee.org/tech-talk/t...ad-as-it-seems
If the leap second gets dumped, then over time the instant of January
1 will drift further with respect the Earth's angular position to the Sun
and the background stars.