[LEAPSECS] Mean ... Orbits

[Tony Finch]

On Wed, 2 Feb 2011, Steve Allen wrote:

>

> It is mean because until the 17th century there was no concept that

> any chronometer could be more stable than the diurnal passage of the

> stars overhead.


Much later than that! After all that's what the longitude prize was all
about.

Unless you are referring to the equation of time, but that was known to
Ptolemy, although it wasn't thought to be important until pendulum clocks
became common in the 17th C.


> It is mean because the combination of Mean Solar Time and the

> Gregorian Calendar produce the conventional phenomenon of the

> Analemma,


The calendar has nothing to do with the analemma. It is simply what you
get from observing the position of the sun in the sky at the same mean
solar time on successive days. How you label the days is irrelevant.
In order to see the analemma you need to know the equation of time.

Tony.
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