From: Philippe Verdy <verdy_p_at_wanadoo.fr>

Date: Tue, 5 Jan 2016 17:26:52 +0100

Date: Tue, 5 Jan 2016 17:26:52 +0100

And given the context of use on the document, where it is a measurement of

time in seconds (it is a mean daily time drift, if you don't read German),

some variants of T/Tau is certainly a best option. The other variables in

the additive formula were also related to time and where also based on "t",

so the formula used various variants of the T/Tau letter.

Intuitively when reading the formula and description I undoubtly pronounced

it "tau" (there was no other occurence of the tau letter in the formula,

but the fact it used a bold capital may be related to the fact that the

mean daily time drift in this formula is nearly constant, with very tiny

variations that the formula wants to take into account in a differential.

Traditionally, consitnats or near constants are using bold capital letters,

and it was made to contrast it with the true time "t" which is obviously

not constant (|dt / dTau| is largely above 1, most of the time except in

very few short periods of time in the year, but the formula is not

interested in finding/predicting those events but to estimate how the

geocentric time evolves over long periods thru years in order to compute

calendars).

The discovery of the cursive variant of pi is interesting but largely too

far graphically : it is is single curved stroke like a turned "J", but here

the "7" shaped letter clearly uses two strokes, like Tau) and semantically

(pi would be related to an angle measurement, not to time, even if the

formula is related to the pseudo-elliptic revolution of Earth around Sun,

it would not be coherent with the additive differential formula cumulating

with time "t".

In summary for me it's just a bold capital Greek letter Tau (in

cursive/itialic style, like "t", because it is a true variable and not a

symbol like the differential operator). The printer however chose to use a

decorative variant of the bold digit 7 to represent it, because it had it

in its collections of metal fonts (e.g. for titling on cover pages, where

titles/headings are customarily using decorative such bold font styles).

May be if you read the rest of the text including the presentation, you

will discover it more completely or even spelled explicitly in sentences.

But we have no audio records to confirm it: the reader has to interpret it

but it is easier to read and understand if you just identify it as "Tau"

rather than "T" or worse as "7".

2016-01-04 19:41 GMT+01:00 Michael Everson <everson_at_evertype.com>:

*> On 4 Jan 2016, at 16:54, Asmus Freytag (t) <asmus-inc_at_ix.netcom.com>
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*> wrote:
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*> >
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*> > On 1/4/2016 7:49 AM, Michael Everson wrote:
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*> >> Excellent!
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*> >> Looks like a candidate character for encoding. I’m sure I have some
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*> examples of good font designs for the old character in one of my books.
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*> >
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*> > Admitting that a Greek letter inherently makes more sense than an "et"
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*> as a variable name, I would still need to understand why "pi" would make a
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*> sensible mnemonic choice for the variable in Gauss' treatise, before being
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*> confident that we've made the correct identification. The more so, as
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*> the use of non-cursive pi for "perihelion" in the same work is clearly
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*> mnemonic.
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*>
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*> Certainly it does look more like a very common variant of “tau” than “pi”
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*>
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*> Michael Everson * http://www.evertype.com/
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*>
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*>
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*>
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Received on Tue Jan 05 2016 - 10:29:21 CST

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