[LEAPSECS] earth speeding up

[Joseph Gwinn]

On Tue, 15 Apr 2014 06:31:21 -0700, Tom Van Baak wrote:

> I know it's a risk making trend lines, but those of us who work with 

> clocks, oscillators and frequency standards find it irresistible to 

> peek ahead sometimes and guess what's coming. This applies to my 

> favorite clock, the earth.

> 

> See attached inverse length of day plots (that is, frequency error 

> rather than excess LOD, or period error). This started with Stable32 

> (the standard tool we all use for time & frequency metrology) but I 

> reformatted them with Excel to make them clearer.

> 

> This plot is for 1 July 1972 to the present. Those of you who follow 

> DUT1 like the stock market recognize the characteristic periodicity, 

> bumps, and trends. Note especially the stable period starting 1999, 

> with many days of the year longer than 86400 seconds, and 

> consequently no leap second for 7 years (roughly MJD 51000 to 54000).

> 

> Any betting person would say the plot shows an upward trend over the 

> past 40 years. A simple linear fit suggests the earth will be back to 

> an honest 86400 second day within a few years, around MJD ~59000 

> (year ~2020).

> 

> The URL for the plot is:

> http://leapsecond.com/pages/lod/earth-lod-10.gif

> 

> See also the zoomed version, where the predicted zero-crossing is clearer:

> http://leapsecond.com/pages/lod/earth-lod-11.gif

> 

> The raw DUT1 and LOD data comes from IERS. It's a work in progress; 

> other plots are under http://leapsecond.com/pages/lod/ as I pursue 

> this.

> 

> I realize this is just for fun, and the serious geology, astronomy, 

> and climate professionals on the list will raise valid concerns. But 

> there's no doubt that since the 1970's the earth is generally 

> speeding back up. If this trend continues, within a decade, we will 

> have another long stretch of no leap seconds and this time it will be 

> followed by our first negative leap second.


This first negative leap second may end civilization - essentially no 
leap-second handling code is really ready for a step backwards.  Yes, I 
know the standard says it can go both ways.  But who reads such boring 
documents anyway?

Joe Gwinn