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Date: Tue, 14 Jul 1998 15:52:22 +0200
From: "fer j. de vries" <[EMAIL PROTECTED]>
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To: Arthur Carlson <[EMAIL PROTECTED]>
Subject: Change of EoT
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Arthur Carlson wrote:
>
> "Sonderegger" <[EMAIL PROTECTED]> writes:
>
> > I think in the northern hemisphere summer is always in July, because the
> > beginning of spring is here always when then sun crosses declination of 0
> > degree from south to north (= crossing the ecliptic). The places of the
> > stars on then sky will change in this 13000 years.
>
> Right. The question is not whether summer will be in July, but
> whether July will be in summer. That only depends on how you choose
> your calendar system. The Gregorian calendar reform was an effort to
> keep July in the summer. The precession is a physical process, which
> does not depend on our calendars. What it does is change the
> constellations that are visible at night in July. Since we don't use
> the stars for sundials, it won't make any difference. What will
> matter is the Equation of Time, as mentioned by Luke Coletti. I think
> the processes which change the eccentricity and obliquity of the
> Earth's orbit work on a much slower time scale than the precession of
> the equinoxes, so that we can still use the same Equation of Time
> 13,000 years from now. Does anybody know for sure about this?
>
> Art Carlson
The EoT changes every year. Not dramatically in one man's lifetime, but
in a period of let's say 5000 years the EoT curve will be different.
For example in -3000 the (absolute value) of the november max is much
smaller than the februari max.
Look at some graphs in Astronomical Algorithms by Jean Meeus.
Fer de Vries.
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