[LEAPSECS] fb/meta join the leap second haters

[Tom Van Baak]

If you go back I'm sure you'll see it mentioned in the LEAPSECS archive. 
When you play with 1962+ data there's a clear ~20 year cycle [1] and, 
more importantly, LOD ends up a bit lower each cycle. So the general 
pattern looks like 20 year arcs back-to-back on top of a gradual trend 
of ELOD going from 2 or 3 ms to 1 or 0 ms the past 60 years.

These arcs are why there's a leap second lull or drought every ~20 years 
and that's why this time around there is even talk about a negative leap 
second. Even if we just barely escape a negative leap second this cycle, 
the trend says we will get one for sure before the end of the next ~20 
year cycle.

This has nothing to do with "tidal braking" which is extremely 
long-term, as in astronomical timescales. Over decades or perhaps 
centuries the not-fully-understood cycles internal to the dynamic earth 
have greater impact.

/tvb

[1] Demetrios has mentioned its the 6939 day Metonic cycle: 
https://en.wikipedia.org/wiki/Metonic_cycle

On 7/26/2022 4:33 PM, Poul-Henning Kamp wrote:
> So looking at the IERS LOD plot going all the way back it seems to
> me that we have been missing the big signal for about five decades:
>
> 	https://datacenter.iers.org/singlePlot.php?plotname=EOPC04_14_62-NOW_IAU2000A-LOD&id=224
>
> How did we not notice that earlier ?
>