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 _______________________________________________ LEAPSECS mailing list [email protected] http://six.pairlist.net/mailman/listinfo/leapsecs
