[Avodah] Molad Alert: Friday night

[Micha Berger]

On Wed, Mar 09, 2011 at 04:58:58PM -0500, Zev Sero wrote:
> I don't understand the basis for this.  What has the precession of the
> equinoxes got to do with the molad, which only concerns the Sun-Earth-
> Moon system?

The molad is only accurate to the nearest cheileq. Add to that what
I wrote about before (although exaggerating the size of the effect)
about the changing length of the month and of the days we use to
measure them.

(Synodic months as measured on atomic clocks are getting longer, because
tides draw energy out of the system. Days are also getting longer, and
they're one of the units of measure in the molad -- people don't just
translate it all to chalaqim. So, overall, the amount beyond the 29 whole
days that makes up the thing a molad estimates is shrinking.)

The molad is too long by 0.6 sec, which added over enough months comes
to a signficant error. And lemaaseh, today the molad does accurately
give you the lunar conjunction for Kandahar, Afghanistan.

Similarly, if you work the same math backwards to Rabbi Hillel II's day,
or chasimas hasha"s, the general era in which our algorithm was finalized
(except for one dechiyah about which machloqes arose), we find that
then the molad would have been accurate for something closer to midway
between Nile and Euphrates -- Alexandria and Nehardaa -- than Y-m.

(Search for "Afghanistan molad". There are people who explained it far
better than I just did.)

>> But as far as I can tell, it was never actually for Y-m. It was for the
>> center of the Jewish world in the final days of the Sanhedrin.

> The Rambam says it's for Yerushalayim and the areas within six or seven
> days' travel around it, from where eidim might come...

WADR to the Rambam, I don't see how that fits the math. I can't speak
further without knowing long distance travel speeds in the amoraic period.
We can compute when the lunation actually was back then. And it wasn't
over Y-m.

So, I'm not sure you should be figuring out the time based on literal
Y-m solar. Perhaps you should use that midpoint, or if you think the
error should be translated into geographic slippage rather than time
slippage, Kandahar.

>> The Shaar haKollel's (and my father's or early-grade rebbe's) explanation
>> implies that the qehillah should know what the time of the molad means
>> in terms they think in.

> I don't see how it implies that at all.  According to this explanation
> the announcement that the molad is imminent (or has already occurred)
> takes the place of the eidim's announcement that they'd seen the moon.
> What has the exact time of the molad, or the scale in which it's
> expressed, got to do with that? ...

I figured that eidus is to al-pi-re'iyah as exact time is to computed
calendar. In both cases, one is demanding knowledge that the month is
being done appropriately before proceding.

Speaking about that dechiyah I mentioned earlier, on Wed, Mar 09, 2011
at 21:54:08 +0200 Eli Turkel wrote:
> There is a debate among rishonim about the validity of the calendar of
> Hillel II.

> Did they declare in advance the kiddush of every month or do the Jews of
> EY do the kiddush today as representatives of the entire nation. RYBS
> postulates that announcing the time of the molad and our prayers are
> the re-enactment of the kiddush hachodesh by bet din in each synagogue

After meeting up here, RYGB and RYZ collaborated on a paper on the
subject of R' Saadia Gaon's calendar controversy for JO a"h. One of the
more central points of the controversy was whether the Gaon had authority
as the globally accepted gadol hador, or whether R' Aharon ben Meir had
priority as he led the qehillah within EY. That sounds like it could be
what RET is talking about.

(The central issue seems to be: The molad for Tishrei being at noon or
later forces a dechiyah. Is that noon as a fixed number (RSG), or is it
subject to slippage based on where the easternmost community is (RAbM)?)

The original paper is at
<http://www.aishdas.org/avodah/vol05/v05n038.shtml#08>. Further discussion
is at
<http://www.aishdas.org/avodah/getindex.cgi?section=C#CALENDAR%20CONTROVERSY%20ARTICLE>
(or <http://bit.ly/f5QSFn>) and a few following related subject headers.

Here is one mythbuster excerpt before I go:
    Nevertheless, it is not clear what, precisely, Hillel II fixed. It
    was not the final version of the calendar we use today and it did not
    ensure that there were no future debates over various details of the
    calendar. [2] There are several problems (other than the one that
    will preoccupy us here) that preclude the possibility that Hillel
    II firmly set in place the precisely fixed calendar we use today. [3]

    Eventually, one of the last Ge'onim, Rabbi Nachshon Gaon, formalized
    a 247 year (thirteen nineteen-year cycles) cycle. A perpetual luach
    based on that cycle (Iggul d'Rabbi Nachshon Gaon) is reproduced in
    the Tur Orach Chaim, at the end of siman 428. All modern luchos,
    such as the ubiquitous Ezras Torah luach and others, are based on
    that table. But that only occurred in the 11th century CE.

    [2] The fixed calendar is not mentioned in the Mishna or Gemara. Rabbi
        Hai Gaon is our earliest source for the mesorah that Hillel
        II fixed a calendar cycle. There are many places in Shas that
        indicate the absence of a completely fixed calendar - for example,
        Abaye's discussion in Ta'anis 29b of the halachos of a Tisha
        b'Av that falls on a Friday.

    [3] It is possible that Hillel II only established the rule that the
        seven out of nineteen years be leap years. Thus, for several
        more centuries there was some variability regarding which years
        should be the leap years. One argument in favor of this relates
        to the four "dechiyos" - rules for postponing Rosh Hashana
        that exist within the calendar rules. As we shall see, only
        two of the four are mentioned in the Talmud. Tosafos, Arachin
        9a d.h. Mai, clarifies that the other two dechiyos were later
        developments. A wealth of material concerning the luach comprises
        the entire thirteenth volume of Rabbi Menachem M. Kasher's Torah
        Sheleima. See the discussion of this and other proofs in Torah
        Sheleima there pp. 166-167 and 176-179.
... [much skipped, they switch to summarizing work by Engineer R' Yaakov
Lewinger of Bar Ilan] ...
	It is, reasonable to assume that those who set our calendar cycle in
        place began counting these nineteen-year cycles from a year
        in which the Spring equinox coincided closely with the molad
        of Nissan. ...

	Counting backwards, 359 CE, which is 4119 by our calendar,
	falls in the 217th lunar month of a cycle. In the first year of
	this cycle, 4105, both the actual spring equinox and the molad
	of Nissan fell on 29 Adar, March 20, 345, with only about a
	six-hour difference....

If we use this reasonable guess, the basics of our calendar were put into
place during the 5th generation of amora'im, before Ravina and R' Ashi.
And in fact, Rabbi Hillel II was nasi 320-365 CE.

-Micha

-- 
Micha Berger             "'When Adar enters, we increase our joy'
micha at aishdas.org         'Joy is nothing but Torah.'
http://www.aishdas.org    'And whoever does more, he is praiseworthy.'"
Fax: (270) 514-1507                     - Rav Dovid Lifshitz zt"l