[EMAIL PROTECTED] (Darren Dunham) writes: >Unruh <[EMAIL PROTECTED]> wrote: >>>> While it may be slowing on average, it is noise and it could well speed up >>>> as well. >> >>>Noise implies that the changes are both positive and negative, in >> They are >>>which case a leap second won't be needed. If it is systematic, >> They would still be needed. Just because your computer's drift rate is both >> positive and negative does not mean that compensation is not needed. >> They do not necessarily average out on the time scale of years. >> >> There is a net drift to longer days. but superposed on that is a noise >> which even over the time scale ofyears makes a difference. An earthquake in >> Java rearranges the moment of inertia of the earth and changes the rotation >> rate of the earth, and it can be positive or negative. >> >>>i.e. the changes are more in one direction than another, a leap second >>>will be needed. >> >> It is needed even if it equal in both directions over a long time.
>It is needed if the noise is equal in both directions *and* if the >average is somewhere near zero. >Besides the noise, there is a strong forward bias as well. The second >is based on earth rotation in 1900. The past century has allowed for >the average rate to slow significantly since then. >So a negative leap will only be needed if the noise is strong enough to >wipe out the entire bias. The recent speedup has only been strong >enough to delay the positive second additions, not reverse them. Yes. And? All you would need is twice the recent speedup and you would get a decriment. It may not happen, but then again it may. ><http://en.wikipedia.org/wiki/Image:Leapsecond.ut1-utc.svg> ><http://maia.usno.navy.mil/lplot1.gif> (Excess Length of Day plot). _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions