Leap Second At The End of 2005

Ruff_ilb writes "Because of the discrepency between an ephemeris second (the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time) and the second of atomic time (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 cesium 133 atom), we're left with more than leap years. In order to ensure that the the atomic time and civil stay coordinated, "Civil time is occasionally adjusted by one second increments to ensure that the difference between a uniform time scale defined by atomic clocks does not differ from the Earth's rotational time by more than 0.9 seconds."" And Happy New Years everyone ;)

Comments

time.gov

[srblackbird]

I watched the time at Time.gov: 23:59:56 (UTC) =>23:59:57=>23:59:58=>23:59:59=>23:59:60!=>00:00:0 0
It was Amazing! This was the first time for me... *remebers where I was at that moment

It's not the 'ephemeris second' that's the problem

[Jonathan McDowell]

Original poster is slightly wrong - it's not the length of the 1900 ephemeris second,
it's the fact that the Earth, like all of us, is getting older and slowing down, so that
the 2005 "Earth rotation" second (i.e. 1/86400 of one spin of the Earth) is longer than
the 1900 equivalent and longer than the atomic time (SI) second. Instead of changing
the length of the second, it is currently deemed less painful to keep using the old
length and stick in an extra second every now and again.

Since this depends on the slop of the Earth's interior, it's not a fully regular and predictable thing - we might even have to remove a second one year.