[Avodah] Where is the Molad announced for?

[Micha Berger]

On Tue, Dec 22, 2020 at 06:45:49PM -0500, Prof. Levine wrote:
> At 05:08 PM 12/22/2020, Micha Berger wrote:
>> Except it isn't solar time for Yerushalayim.

>  From https://oukosher.org/halacha-yomis/how-is-the-molad-calculated/

>> In addition, it is worth noting that the molad is announced in 
>> accordance with Jerusalem time.
...

I already explained why I think it cannot be, as it would have been
23 minutes off in the last days of the Sanhedrin if they meant J-m
local time.

I don't know what else to add. I just think people assume Y-m time,
because it just seems obvious.

Then we get to the Rambam, who we cannot just dismiss like that...


On Tue, Dec 22, 2020 at 06:50:22PM -0500, Zev Sero via Avodah wrote:
> The point of difficulty I have with your explanation is that it rests on an
> assumption that the interval in our tradition was completely precise when it
> was enacted. It seems to me that it was always rounded to the nearest
> chelek; if there happened to be a time when it was precise, that's nice, but
> it's not necessarily the time it was enacted....

It's more than that... The time it was most accurate "just happened" to
be the same generation that established our calendar. (Minus one dechiyah
window that didn't get resolved until R Saadia Gaon.)

To me, that just cries "siyata diShmaya".

But the minimum for the error margin for the time of the molad on Y-m
ih"q local time is not zero. It is on month number 44,609, Tammuz 3607,
154 BCE, 10 years after Chanukah. You get to earlier months than that,
and the the molad as a multiple of days becomes too short again. That
minimum is 15min 27 sec (and I neglected to write the chalaqim) off. That
would be a meridian a little over 4deg East of Y-m.

Again, I have made numerous math errors here in the past. I am only confident
this time because any Google hit of someone else who did the work got
similar results. (Or at least, once I googled and fixed my errors, we have
the same results. <grin>)

At least with my assumptions, we get very close to the middle of the
yishuv in the days when VeSein Tal uMatar was set to either EY's climate
or Bavel's. I am not sure what we gain by being only 1/3 of the way
to Bavel.

> I do think the plain implication in the Rambam is that it was *intended* to
> be Y'm time, and therefore was set a few centuries earlier than you suppose,
> or else the rate of change has itself changed and we can't know now
> precisely when it was accurate.

We can know the curve exactly, unless you want to say nishtaneh hateva
and orbital mechanics worked differently back then.

I looked for "Yerushalayim" and "Yerushalaim" (without a second yud) in
Hil Qidush haChodesh on Bar Ilan. I found the latter in a few places about
yom tov sheini shel goliyus, and then this one, which is I assume your
maqor.

See 11:17.
<https://www.sefaria.org/Mishneh_Torah%2C_Sanctification_of_the_New_Month.11.17>
The Rambam talks about basing his calculations
    on the city of Y-m and the other places that surround it, during the
    6 or 7 days in which we always see the moon and come and testify in
    court. And this area is off about 33 degrees (from 35 to 29) north
    of the equator that encircles the world. And it is also off about
    24 degrees (until 27 to 21) west of the median line of civilization.

We don't know where the 0 deg meridian, "mei'emtza hayishuv" was in the
Rambam's maps. But, since more people testified in court from Bavel than
from Egypt or points west, it's not impossible that he didn't nmean
an area CENTERED on Y-m as much as one centered on the middle of the
population that would come to testify there.

It's weak, I know. But the alternative is leaving the Rambam at odds with
Kepler. And I don't think we have to.

Tzarikh od iyun.

Tir'u baTov!
-Micha

-- 
Micha Berger                 Life isn't about finding yourself.
http://www.aishdas.org/asp   Life is about creating yourself.
Author: Widen Your Tent               - George Bernard Shaw
- https://amzn.to/2JRxnDF