[Avodah] Announcing the Molad

[Zev Sero via Avodah]

On 05/18/2015 12:41 PM, Micha Berger wrote:
> What am I missing?

That what we announce is *not* anything to do with the actual moon, which
the eidim in RG's time would have claimed to have seen, but the notional
averaged moon on which *our* calendar is based.   The *real* molad, i.e.
conjunction of moon and sun, does vary, because the real moon does not
orbit the earth in a perfect circle; the notional molad on which we base
our calendar, and which we announce every month (except, ironically, the
one month when it actually matters), is perfectly regular.   And "molad"
does seem to mean the conjunction, not the moment when the first sliver
is visible, because the gemara in RH seems to say that the first possible
sighting of the new moon is six hours *after* the molad.

So we do know exactly what we are announcing: the number on which the
calendar is based.  Given this Shabbos's announcement, one can easily
calculate that next Rosh Hashana will be on a Monday, exactly as it
should be.

-- 
Zev Sero               I have a right to stand on my own defence, if you
zev at sero.name          intend to commit felony...if a robber meets me in
                        the street and commands me to surrender my purse,
                        I have a right to kill him without asking questions
                                               -- John Adams