[LEAPSECS] Reliability

[Tony Finch]

On Fri, 2 Jan 2009, Rob Seaman wrote:

>

> So yes, I think the angular momentum of the Earth is more real than the

> observations that might be compiled to generate an estimate for its value.


But the value is an estimate, so if you plug numbers into a model based on
this estimate you are only going to get an estimate to apparent solar
time. In fact, since the model has to include a value for the earth's
unpredictably variable moment of inertia, the result of using the model is
going to be less accurate than the estimate you started with.

(Um, do we actually know the earth's angular momentum and moment of
inertia to any useful accuracy? I would have thought models would be based
directly on angular velocity since that can be measured more precisely.)

I think it's wrong to say that a directly measurable value (such as
apparent solar time) is less real when measured than when derived from a
model!

Perhaps the word you are looking for is "fundamental".

Tony.
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