[Avodah] Rosh Chodesh Adar

[Micha Berger]

The time announced isn't the mold emtza'i. It's the molad emtza'i for
1600 years ago.

There is an interesting chizuq emunah here. The molad was too short when
first published by Ptolemy in the Amalgest, and certainly far less in the
days of the Babylonians that Ptolmey cites as a source. It was accurate
within milliseconds when Rav Hillel standardized the calendar (depending
on the exact date it happened). Which does make the most sense if the
RBSO gave Moshe Rabbeinu the molad in parashas Bo, and the Babylonians
measured it knowing from us what answer they were supposed to get.

Last time around we discussed the difficulty of measuring the molad to
the nearest cheileq in a world without standardized clocks. The molad
amiti varies to -12 hr to + 16 hr around the molad emtza'i. You need
to average over centuries, and have no way of knowing how many chalaqim
went by. After those centuries, you would get the molad emtza'i at some
point in the middle of the interval. And then they get an error that
just happened to exactly match the molad centuries later, when we'll
need it when the Sanhedrin disbanded?

Divine involvement seems the most plausible explanation.

You can learn much more about the astronomy of the molad at
<http://www.sym454.org/hebrew/molad.htm>. (Not a frum source; he proposes
a new molad to switch to.) He also resolves many of the questions raised
last time around to my satisfaction, FWIW.

Because of the above error, it is non-trivial to know where the
intended meridian was. Most Jewish sites, including the OU, assumes
it's Jerusalem Mean Time. Someone on mail-jewish convinced me a while
back that it was at Alexandria, the western edge of Jewish settlement,
the first to see the molad. But working back to Rav Hillel's day, Dr
Bromberg gets to 23 mean solar minutes east of Yerushalaim (5-3/4 deg),
somewhere in eastern Jordan. And so he concludes the time announced
was midway between EY and Bavel, the settlement at that time.

Or the mean between the Nile and the Euphrates -- Nachal Mitzrayim and
Nehar Peras?

Last, it seems our grandparents or greatgrandparents announced the time on
a different clock. Under the Ottomans, many in Israel followed a system
common in Moslem countries of resetting the clock to 6pm at sunset,
and most announcements used that.

Tir'u baTov!
-mi

-- 
Micha Berger             "The most prevalent illness of our generation is
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