On Jan 11, 2012, at 9:53 AM, Rob Seaman wrote:
> Warner Losh wrote:
>
>> Tom Van Baak wrote:
>>
>>> Although on average LOD is more than 86400 s by a few milliseconds, in the
>>> past fifty years about 3% of the days have been shorter than 86400 s. In
>>> the past decade alone the figure is 14% (the earth has sped up quite a bit
>>> the past decade). You can imagine then that some days must be rather close
>>> to no error.
>>>
>>> Five days were within 1 microsecond and the record goes to November 29,
>>> 2004 which was just 200 nanoseconds shy of a perfect 86400 second day.
>>
>> How much better would be if we'd adapted a mean solar second of 1900 instead
>> of 1820 which we wound up with?
>
> See Steve's plot:
>
> http://ucolick.org/~sla/leapsecs/lod.pdf
>
> or the top plot of http://ucolick.org/~sla/leapsecs/amsci.html, zoomed to
> recent decades.
>
> The Earth would be deemed fast by about 4 ms / days (five millionths of a
> percent if I've got the decimal right).
>
> What is "better" or "perfect" here is a matter of debate.
I'm asking for either of the plots, rescaled with a second based on the average
second of 1900 rather than on the average second of 1820ish that newcomb's
second (which is what the SI second wound up being based on) wound up being
based on...
Another way of asking the question is 'what would the rate of leap seconds (or
slope of TAI - UT or TT-UT)' if the definition of a second gave is an average
LOD - 86400s of more like 1ms or 100us. And would we have had to have negative
leap seconds...
Warner
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