Volume 55 Number 95
                    Produced: Tue Dec  4  6:28:43 EST 2007

Subjects Discussed In This Issue: 

         [Michael Frankel]


From: Michael Frankel <michaeljfrankel@...>
Date: Mon, 3 Dec 2007 18:01:24 -0500
Subject: Z'manim

There are a variety of opinions on absolutely everything associated with
Alos Hashshachar starting with just what is it anyway, how is it
calculated, sho'os z'maniyos or not,etc.  in fact, it is a far more
confusing halakhic state that that attending what you might think would
be its physically symmetric complement in the evening transition from
daylight to darkness.  some of the responses to date in this forum,
while informative, also contain information i believe to be incorrect.
so let me have a pass at sorting through the issues, at least as they
appear to me.  this is kind of a companion/complemetary piece to a
previous note i once posted on evening z'manim (MJ, Vol 53:#57).

1.  What is Alos Hashshachar (AH) anyway?
By consensus, it's the very first lightening (reddening) of the night
sky in the east = "hey'ir mizroch".  This - the first "spot" of
reddening - is (perhaps) to be distinguished from a closely related
condition - "hay'ir kol mizroch" where the entire eastern sky has
achieved some reddening and occurs (a few minutes) later.  however not
all acharonim make such distinction between "hay'ir" and "hay'ir kol"
and equate AH with the latter. This interpretation of AH is implicit in
the direct translation; AH = "lifting of the darkness".  It emphatically
has nothing to do with the "rise" of the "morning star" which may (or
may not. it's a machloqes - surprise) be identified with the phrase
"ayeles hashshachar".  rashi however is confusing because, while he too
equates AH with hay'ir mizroh per the consensus, in other contexts
( e.g. B. M'nochos 68a) he equates AH with Honetz (sunrise).

2.  Sho'os Z'maniyos or Not?
Basically - yes.  I am uncertain where Dr. Gewirtz who, i think,
asserted the contrary is citing from (DG: "alot does not vary with shaot
zemaniot - that commonly held opinion is asserted by multiple poskim
going back almost 400 years"), but it seems clear to me that alos must
be calculated with z'maniyos "hours" according to all (possible
exception of the rosh) classic sources and almost all modern
sources. (we'll get to the how in just a moment). thus the rambam
explicitly states "v'dah, ki kol sh'os hannizkoros b'khol hammishnoh,
haim hashsho'os hazz'maniyos" (Peirush Hammishnayos, B.  B'rokhos
1:2. (of course, alos doesn' vary with z'maniyos in the sense that the
rambam (and other) shiurim are a fixed number of "hours".  but the
length of that "hour" varies from day to day, and thus so does AH.
perhaps that's what DG meant in which case i wouldn't disagree) The
rambam is also brought l'halokhoh by the Remoh (O"H 233).  while it is
true that a number of acharonim do suggest theoretically that these
hours should be fixed -and perhaps this is the source of Dr. Gewirtz's
assertion. these include R. Y. Emden, the p'nei yehoshua, the miskinos
yaacov and couple of others-, however in practice, even most of these
defer to the rambam and remoh's ruling in the matter.  typical is the
mishkinos yaacov who, after summarizing his argument for "fixed" hours,
nevertheless concludes with "v'choliloh lonu l'horos kain neged
harambam".  This consensus for sho'os z'maniyos is reviewed and
summarized by R. Moshe Feinstein in Igros Moshe, O"H (2), s'20, who also
rules very emphatically for z'maniyos.  So it's z'maniyos by a large

3.  How do we compute Alos Hashshachar?
To execute this calcualtion, two choices must first be fixed from a
smorgasbord of options.  One parameter that needs fixing is the legnth
of the sh'oh z'manis to be used for the dayte in question - which in
turn depends on a choice of between different options available to
calculate it.  the second choice which must be fixed is that of the
preferred shitoh which decrees just how many sho'os z'maniyos must be
counted - starting backwards from sunrise - until Alos Hashshachar.  We
consider these decisions in reverse order:

a) what is the number of sho'os z'maniyos between AH and Honetz (or
The g'moroh is p'sochim 93b-94a declares the time beteween AH and Honetz
to be either 4 or 5 mil.  this translates into a few different shitos
(actually a lot more , given the universe of different estimates of the
mil, but we only list the more prevalent ones).  1) 1.2 "hours" (i.e. 72
minutes, at 4 mil x 18 min/mil) which is the shiur given by the rambam
in the previously cited source in peirush hammishnayos.  this
corresponds 9at the equinoxes) to a depression of the sun below the
horizon of 16.1 deg.  2) 1.5 "hours" (90 minutes = 4 mil x 22.5 min/mil)
corresponding to a solar depression of 19.6 deg, 3) 2 full "hours" (120
minutes = 5 mil x 24 min/mil) corresponding to a solar depression of
almost 26 deg.  4) R. David Tzvi Hoffman, the poseiq for Germany prior
to WWI, rules that AH is taken when the sun reaches -18 deg depression,
which would translate to about an 86 minute shiur.

b) How long is a Sh'oh Z'manis?

Poorly worded, since it varies from day to day. real question
is how to calculate it each day. answer to that is there are
two main shitos; that of the Gaonim and that of T'rumas
Haddeshen (an early - 15th cent. - acharon). 

(i) Gaonic Shitoh: (also subscribed by, inter alia, the Gra, L'vush,
R. Shlomo Zalman Auerbach.  also by the Shulchon Aruch, at last
according to Minchas Cohen).  take the time from honetz till sh'qi'oh (
i.e. sunrise - sunset) on each day and divide by 12.

(ii) T'rumas Haddeshen: (also rashi, tosofos, rashboh, bach, mogein
avrohom. also the Shulchon Aruch, according to mishnoh b'ruroh).  Take
time from AH until tzais hakkokhovim, and divide by 12.  i.e. a larger

You can see the opportunity here for wildly proliferating shitos
depending on your choice to fix AH per previous paragraph, coupled to
choice of different shitos in tzais hakkokhovim as well - the latter
which i won't take an excursion to review here (some are detailed in my
previous note of MJ 53:57).  according to r. chaim bainish - whose work
on z'manim i have used to compile the list of shitos who line up with
either gaonim or t'rumas haddeshen that i cited above - the minhog in
Lita and Russia followed the gaonim while elsewhere, including eretz
yisroel, it followed t'rumas haddeshen.

4.   What is earliest time to perform mitsvos hayyom?
t'filin, q'rias sh'ma, and tzitzis - all involve a "seeing" (u'r'eesem
osom).  thus they all techically require a shiur of "me sheyyaqir".
i.e. light enough to recognize something . either a) between blue and
white, or b) your friend's face at 4 amos (different shiurim - perhaps.
in practice not).  this "me sheyaqqir" is some stage after AH, with very
little published guidance by poskim on just what that shiur might be.
r. bainish cites three minhogim prevalent in different locations in
eretz yisroel; variously 60 minutes, 52 minutes, and 45 minutes before
honetz. but it would seem just as reasonable, especially for b'nei chutz
lo'oretz with no fixed minhog hammoqom, to determine the number
experimentally for themselves.  that said - i.e. that the shiur is at
"me sheyyaqir" - we nevertheless have two other times cited for these
mitzvos which also work, better or worse.  working better than "me
sheyaqqir" is the shulchon aruch's advice to nevertheless time it so you
consumate your mitzvoh with sunrise - as do the the vosikin.  this is
termed a mitsvoh min hammuvchor.  on the other end of desirability is
the permission of all the pos'qim to begin your mitsvoh with AH, if it's
a sh'as hadd'choq - some emergency or very pressing situation.

5.  A note on the asymmetry between the periods AH-Sunrise, and Sunset -
Tzais Hakkokhovim.
of course there a big fat glaring halakhic asymmetry between the periods
AH-Honetz and Sh'qioh-Tzais.  to wit - no one ever bothered to identify
a bain hashsh'moshos period for the former.  but i have also seen it
asserted that there is at least a physical symmetry between the two
(i..e that they should take the same amount of time to achieve the same
amount of darkness-light transition) this is clearly not true - at least
in principle.  this for at least two reasons, one of them fairly
trivial.  the first, trivial reason, is thsat there is a delta in time
between the two events in a single day.  crudely speaking there is a 12
hour differential and the earth is about 1/729th further along its
orbital path, or possibly 1/364th between its maximum and minum
day-night transition period (i know it's not linear but i'm only trying
to get a feel for the magnitudes).  looking up the US navy tables for
the latitude of silver spring, i see the difference between max and min
trasition period is about a half hour (i took night to be equal to
astronomical twilight, at 18 deg solar depression, also R. DZHoffman's
shitoh).  so a 12 hour delay translates into about a five second
intrinsic difference.  not a lot to be sure, but enough to establish
tohe principle of asymmetry.  a more significant reason lies in the role
of the atmosphere.  the degree of refraction of sunlight when below the
horizon depends on the thermodynamic state of the atmosphere.  published
tables are never really "true" since they must assume some averaged
atmosphere, whereas random variations may contribute up to afew minutes
variation in actuual, observed refraction.  riding on top of the random
variation in this case is a systematic variation.  i.e. in the morning,
th eatmosphere is colder, denser, and lower.  i have no data in hand to
estimate this effect - nor have i seen it remarked in published works -
but simple comnsideration of the physics involved convinces me it must
be a real effect and might well amoun to a couple of mutes variation
between the morning and evening transiiton periods.  I assume such
considerations are folded into the navy tables, but in any event, it is
clear that the morning and evening transition times cannot be the same.

6.  Burn thise Luchos; a modest halakhic suggestion 
Basically a luach publisher can do whatever he wants.  in Israel where
z'manim calculated by R.Y.M. Tokachinsky were popular, i wonder how many
were disturbed in the 1920s when he suddenly switched qall his tzais
calculations from on ebased on the appearance of three stars to one
based on a fully dark sky.  so a general complaint i have about luchos
is that no one ever really knows their provenance.  there are so many
different shitos related to z'manim that are possible - we have
recounted only a few of the possible variations here - that it is
practically impossible to tell what some essentially anonymous luach is
based on - and perhaps we wouldn't much like that shitoh if we knew.
here q"q silver spring MD, the Chabad calendar and luach are
particularly popular.  Not because anyone has the slightest idea of how
any of the z'manim were arrived at, but because of the nice artwork and
it's just the right size for posting in the kitchen and scrawling notes
in the individual day-boxes.  there was a general communal wailing and
gnashing of teeth a few years back when the chabadistas in charge of
distribution were late getting their calendars out to the local
communities and after rosh hashshonoh we had nowhere to write our
kitchen notes.  please don't rat us out to david berger.  anyway -
herewith my suggestion.  let's burn the various published luchos and go
back to eyeballing th eskies the way we used to do when i was a kid -at
least for tzais. (no way was i getting up in time to eyeball AH, and -
ok, ok - so keep a luach locked away in a closet somewhere as backup for
cloudy days).  This automatically corrects all concerns and justified
confusion over which is the correct shitoh for calculating AH, and also
corrects for real-time atmospheric conditions which no luach of whatever
shitoh can ever hope to do.  besides it's more fun.

Mechy Frankel                                          


End of Volume 55 Issue 95