[Avodah] Zmanim for Ta'aniyos

[Micha Berger]

On Wed, 19 Aug 1998 11:24:13pm CDT, RYGB wrote (yes, I'm reviving a 14 yr
old thread):
> There are prominent Shuls and Rabbonim that announce the onset of a
> ta'anis d'rabbanan as 72 minutes before sunrise (alos ha'shachar).

> There are prominent Shuls and Rabbonim that announce the end of a
> ta'anis d'rabbanan as 50 minutes after sunset (tzeis ha'kochavim).

> The former seems too great a kulla, the latter too great a chumra.

> The 72 minutes is a difficult statement by the Rambam, elsewhere he says
> 90 minutes. The other Rishonim all say 90 min. (this based on the shiur of
> a mil, that most Rishonim hold to be 22.5 min. Even those, like the
> Terumas HaDeshen that say 18 min. are probably referring to Magen Avraham
> minutes, which are = to the period between alos and tzeis divided by 720).
> Regardless, even like the Rambam, the 72 min. is equinox day (16.1d
> beneath the horizon - 90 min. = 19.8d) and must, logically, be adjusted
> for time of year - for summer ta'aniyos, a significant difference
> l'chumra.

> The 50 minutes is really difficult to explain. The main opinions in the
> determination of tzeis are the Gra, who uses sea-level calculations
> (4.81d) and Ba'al HaTanya, who uses mountaintop calculations (5.95d).
> Prof. Levi's astronomical analysis of realtime tzeis is closet to the
> Ba'al HaTanya - almost precisely, in fact. That is also, obviously,
> seasonable adjustable, but never more than about 35 min., tops (in N.
> America). There is, of course, Rabbeinu Tam, who uses  4 mil - either 72
> or 90, the same measure as alos ha'shachar.

> The 50 minutes is really the Ba'al HaTanya with some tacked on time in
> order to rounf off + fulfill Tosefes Shabbos. That is reasonable because
> of the chumra of Shabbos + the mitzva of Tosefes Shabbos. It is not
> clear to me why anyone need be machmir for a  ta'anis d'rabbanan.

FWIW, I think the usual Rabbeinu Tam vs the Gra formulation is misleading.
The Gra is restoring the position of R' Sherira and R' Hai Gaon. And
implied that in their day, it was accepted practice. The position
usually attributed to just Rabbeinu Tam is also that of the Rambam,
Ritva, and Rashba.

R' Saadia Gaon, as quoted by Ibn Ezra on Shemos 12:6, talks about nearly
80 min. But while R Adam Zur and I recently discussed this at length (see
comment chain at
<http://rechovot.blogspot.com/2012/01/wanted-experimental-yeshiva.html>),
I can't understand what R' Saadia means. He is talking about the latest
time to shecht the qorban Pesach. But I thought shechitah and zeriqas
hadam must always be before sheqiah. So, my first guess was that 80 min
were the end of the day, until sheqi'ah, nothing to do with tzeis. But, as
RAZ pointed out, I missed the words:
    And here we have two aravim:
    The first is the areivas hashemesh, and that is the time it comes under
    the earth;
    and the second is the coming of its light which is seen in the cloudes.
    And there is between them close to 1-1/3 hours.

The IE also talks about this on Berieshis 1:18:
    And know that the time that the sun darkens is erev until an
    hour and a third that you see something like light in the clouds
    and similarly the boqer is light before sunrise.

He doesn't use the word tzeis either time, only erev. I don't know what
this shitah refers to. Plag to sheqiah? Sheqiah to tzeis? Or is his two
aravim the same as R' Tam's notion of two sheqios, and R' Saadia and the
IE hold tzeis is 80 min + another 3/4 mil?! I think the latter best
fits the words and my shechitah problem, but makes for an absurdly late
tzeis.

On Thu, 20 Aug 1998  2:22:03pm +0300, R Shragai Botinick replied to RYGB:
: Doesn't Rav Moshe Feinstein in Igrot Moshe (I believe vol. 4 orach
: chaim) claim that Rabbeinu Tam in America(N.Y.) is around 50 minutes -
: and a mil is around 13 minutes.

And then the next Sun, 23 Aug 1998 13:12:15 +0300, RSB added:
: [RMF] says in Orach Chaim Vol. 4 siman 62 explicitly numerous times that
: 50 minutes fulfills mekar hadin the shita of Rabbeinu Tam (just bnei torah
: should be machmir till 72). That in the U.S. after 50 minutes it is the
: equivalent darkness as it was in Europe after 72+ minutes. (and based
: on the Gra every place has a diff. zman). He therefore says that the
: first 9+ minutes is bein hashmashot of the gaonim, the next 31+ minutes
: is definitely night for the Gaonim and definitely day for Rabbeinu Tam,
: the next 9+ minutes is bein hashmashot of Rabbeinu Tam.

: (therfore the U.S. mil is about 12.5 minutes)

: For a tannit drabbanan he says 50 minutes is enough.

More points from that discussion with RAZ...

R' Yechiel Michel Tukachinsky, in a booklet titled "Bein haShemashos",
said that in practice in EY it takes about 22 min after sunset before
the stars could be seen. R' Yehudah Levi, "Zemanei haYom", says that a
trained eye of average natural acuity can see them in 15 min. The Gra
explicitly says his mil is 22-1/2 min, so RYL's number is in the right
range. BTW, among the Gra's arguments is that Rabbeinu Tam's shitah is
far from the experimental data.

To me, this [shift from most geonim to the rishonim] argues that in EY
and Bavel (same latitudes), the two opinions must be describing something
similar, and it's only after we left Bavel that the two models diverge. I
don't have it worked out how that's possible. It would involve the range
of values for the mil (18 - 22.5 min) and the machloqes about whether
the time is a fixed number of minutes, or the number of degrees the sun
would be below the horizon on the equinox in EY after those minutes.

The Geonim, who lived in a similar latitude to EY, held the way the Gra
later championed. We have written teshuvos from R' Sherira and R' Hai
Gaon, writing in Pumbedisa -- which today is called Falluja, Iraq. To
compare, Y-m is at 31 deg 47' N, Falluja is at 33 deg 21' N. Whereas R'
Tam's hometown of Troyes, France is at 48 deg 19' N and the Gra's Vilna,
54 deg 40' N.

I find it hard to believe that the geonim and the Jewish people when the
majority lived in the Middle East didn't have a plausible definition of
tzeis, when the definition was given WRT a nearby area (EY).

Second, the Gra was no stranger to math and science, even if he
couldn't have done the experiment himself. He raises the astronomical
implausibility of R' Tam's et al's opinion as one of his reasons for
recommending reversion to the position of the geonim. If he were silent,
it would be one thing; but it would seem R' Tam's shitah doesn't fit
the spherical trig.

Last on this plausibility discussion, I went to Wikipedia and the
secular definitions of twilight (looking now only at the evening half
of the discussion) <http://en.wikipedia.org/wiki/Twilight>

Secular culture has 3 twilights:

Civil twilight: when the sun is at until 6deg below the horizon. (Or
the reverse, at sunrise.) This is when the brightest stars and Venus --
ayelet hashachar -- are visible.

Nautical twilight: 6-12 deg below the horizon. Before which, you can't
see enough well-known stars to navigate.

Astronomical twilight: 12-18 deg below. After which, it's dark enough
for good astronomy, even diffuse things like nebula and galaxies could
be seen. (Well, not when you're as close to NYC as I live...)

R' Moshe's 50 min comes to 12.5 deg. The frequently used 8.75 deg for
Shabbos (3 small stars) also fits the expectations of the secular world --
for suitable definitions of "small".

In Y-m, civil twilight is 24-28 min, nautical twilight is 52-62min, and
astronomical twilight is 81-100min. Meaning, 72 min in EY is not quite
zero stars, but real close. Not when you see 3 small stars, unless by
this you mean diffuse things like nebula or galaxies, rather than points
of light.

Whereas the Gra holds 3/4 of a mil, 13-1/2 - 16-7/8 min. Well shy of
civil twilight, when one can only see Venus and three bright stars.

It really looks like RMTukachinsky and RYLevi's experimental data, 22
min for most people 15 min for experts (respectively), fits the range
for when astronomers would assume 3 medium stars could be seen.

It also looks like the Orchos Chaim's take on R' Tam, that he was saying
when 3 stars on the western (most lit) horizon could be seen, would also
fit the data. (Also the Minchas Cohen's -- that R' Tam was saying that by
72 minutes you can be sure it is after the actual tzeis even in Troyes.)

But pashut peshat in R' Tam still does not fit the data.

Tir'u baTov!
-Micha

-- 
Micha Berger             Life isn't about finding yourself
micha at aishdas.org        Life is about creating yourself.
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