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From: Markus Kuhn <Markus.Kuhn_at_cl.cam.ac.uk>

Date: Fri, 25 Feb 2005 12:41:43 +0000

John Cowan wrote on 2005-02-24 20:07 UTC:

*> Rob Seaman scripsit:
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*>
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*> > Not silly - and not secular. Astronomers (at least) use the term
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*> > "secular" to imply monotonic - and therefore cumulative - effects.
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*>
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*> Ah, I didn't grasp that point, and was merely using it to mean "not
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*> periodic".
*

The way I understood the word "secular" to be used in astronomy, it it

can be defined formally as:

Given two time-varying functions g(t) and f(t), with g(T_0) = f(T_0) for

some time T_0, we say that g(t) features a "secular deviation" from

f(t), if for any b > 0, there is a time T > T_0 such that

for all t >= T the inequality || g(t) - f(t) || > b holds, where

|| x - y || is a suitably chosen distance measure.

In other words, a secular deviation grows beyond any constant bound.

TAI(t) and UT1(t) feature a secular deviation.

[Outside astronomy, there is of course the far more widely used

political meaning "non-religious" for the same term, as in "Irak's

secular government versus Iran's Islamic government".]

Markus

Date: Fri, 25 Feb 2005 12:41:43 +0000

John Cowan wrote on 2005-02-24 20:07 UTC:

The way I understood the word "secular" to be used in astronomy, it it

can be defined formally as:

Given two time-varying functions g(t) and f(t), with g(T_0) = f(T_0) for

some time T_0, we say that g(t) features a "secular deviation" from

f(t), if for any b > 0, there is a time T > T_0 such that

for all t >= T the inequality || g(t) - f(t) || > b holds, where

|| x - y || is a suitably chosen distance measure.

In other words, a secular deviation grows beyond any constant bound.

TAI(t) and UT1(t) feature a secular deviation.

[Outside astronomy, there is of course the far more widely used

political meaning "non-religious" for the same term, as in "Irak's

secular government versus Iran's Islamic government".]

Markus

-- Markus Kuhn, Computer Lab, Univ of Cambridge, GB http://www.cl.cam.ac.uk/~mgk25/ | __oo_O..O_oo__Received on Fri Feb 25 2005 - 04:41:59 PST

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