Tom Van Baak scripsit:
In fact, leap seconds are simply due to the earth
being slow. How it got to be slow and whether
it is slowing are another issue.
Let me see if I have this right:
1) We have leap seconds because the Earth rotates more slowly
than once every 86,400 SI seconds.
2) Leap
Hi Tom,Careful not to confuse rate with acceleration andpropagate a common misconception that leapseconds are due to an acceleration/decelerationeffect (as in "leap seconds are due to the earthslowing down").In fact, leap seconds are simply due to the earthbeing slow. How it got to be "slow" and
John Cowan wrote:
1) We have leap seconds because the Earth rotates more slowly
than once every 86,400 SI seconds.
2) Leap seconds will become more frequent in the future because
the Earth is decelerating.
3) Leap seconds occur irregularly because the Earth's deceleration
is not constant and
John Cowan accepts the blame:
1) We have leap seconds because the SI second is shorter
than 1/86,400 of a mean solar day.
Post in haste, repent at leisure (I've been going with too little
sleep lately, for reasons unknown...) I actually do know that
the earth rotates in less than 1 mean
Rob Seaman scripsit:
Blame for what? I'm left wondering. Are we now fretting about
the distinction between sidereal and solar time again?
I accidentally specified sidereal rather than mean solar days by
using the wording the Earth rotates.
A leap hour is just 3600 embargoed leap seconds.
John Cowan wrote:
I accidentally specified sidereal rather than mean solar days by
using the wording the Earth rotates.
Rotate is as perfectly good a word to use relative to our nearby star
as to the distant ones :-) The solar system is chock full of nifty
synodic
periodicities and
In fact, leap seconds are simply due to the earth
being slow. How it got to be slow and whether
it is slowing are another issue.
Let me see if I have this right:
1) We have leap seconds because the Earth rotates more slowly
than once every 86,400 SI seconds.
Yes. (and I know what you
Rob Seaman scripsit:
Third result - even in the absence of lunar braking, leap jumps
(or equivalent clock adjustments) would remain necessary.
Why is that?
If the SI second were properly tuned to the mean solar day, and the
secular slowing were eliminated, there would be no need to mess about
If the SI second were properly tuned to the mean solar day, and the
secular slowing were eliminated, there would be no need to mess about with
the civil time scale, because the random accelerations and decelerations
would cancel out in the long run. Of course, we'd have to tolerate larger
Brian Garrett wrote: the mini-lectures did imply that leap seconds compensate for secular deceleration of the earth rather than seasonally accumulated differences between UTC and UT1. To the extent that I understand the point you are aiming for, this statement conflates two issues: 1) that
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