(a) RASHI explains that the sun sets at a different point on the western
horizon each day, depending on the season. It sets further south on the
western horizon in the winter, and further north in the summer (see Graphic
#1). However, Rashi says, at the time of the new moon, the moon *always*
appears at the "south-west corner." (Rashi implies that it appears there
slightly *before* the moment at which the sun sets.) Therefore, on the
shortest day of winter (the winter solstice), when the sun sets farthest
south along the western horizon, since the moon reaches the south-westerly
point at which the sun will set slightly before the sun does (i.e. before
sunset), it is seen slightly to the north of the sun (that is, *ahead* of
the sun in its circuit of the earth -- see Rashi on the Mishnah regarding
north and south of the sun ). Likewise, when the sun sets in the *northern*
side of the western horizon (in the summer) the moon still appears close to
the southern corner, and thus it will be seen further south than the sun
("behind" the sun).
How is this possible? The moon always follows approximately the same path as
the sun and stars when circling the earth, and therefore the new moon, which
is right behind the sun, always sets in approximately the same place that
the sun sets! When the sun sets to the north-west, so does the moon. How can
Rashi write that the place where the moon sets does not change depending on
the season? As the place of the sunset changes, the place of the moonset
also changes! In addition, how can the new moon ever be seen "ahead" of the
sun! By definition, the Molad is the point at which the moon passes the sun
from west to east, and after the Molad it *must* be more to the east of (or
"behind") the sun. (See TOSFOS 20b DH Chatzos, who asks a similar question
on Rashi.)
Perhaps Rashi had some other intention (see below, b).
(b) RABEINU CHANANEL offers a different approach to the Sugya, which can be
easily understood with the help of the following introductory remark.
As Rashi explained, the point at which the sun sets continuously changes
through the seasons. The path in which the sun (as well as the moon and
planets) is seen to travel is called the ecliptic. It is only on this path
that the sun is seen to be circling the earth once a day (and in which
eclipses occur; hence the name "ecliptic"), and it is along this path that
the 12 constellations referred to as the "Mazalos" (zodiacal constellations)
lie. Each month, another of the 12 Mazalos poses as the backdrop for the
sun, since the sun slowly "slides back" along its path almost one degree per
day. (That is, from the perspective of any given point on earth, the sun
along with the stars and the planets draw a full circle around the earth
once per day. This is due to the 24-hour rotation of the earth. Relative to
the stars of the zodiac, the sun slides back almost one degree every day.
This is due to the 365 day revolution of the earth around the sun.) In this
manner the sun travels through the entire zodiac, a full 360 degrees,
through the course of the solar year (365 days). With this in mind, it is
evident that the point which is one degree behind the sun on the ecliptic
will meet the horizon in the place where the sun will meet the horizon the
following day.
The new moon is first seen when it is 9 to 15 degrees "behind" (eastward of)
the sun (Rambam, Hilchos Kidush ha'Chodesh 17:3 -- see what we wrote in
Insights to 20:3:c:2 to reconcile this with Rashi, who writes that it can be
seen but six hours -- 3 degrees -- after the Molad). The moon travels on
approximately the same path as the sun (the ecliptic). If so, when it is 9
to 15 degrees behind the sun, it will set at the point on the horizon where
the sun will set in another 9 to 15 days. Therefore, from Tekufas Teves to
Tekufas Tamuz (from the winter solstice to the summer solstice), the moon
will be setting further north of the sun, since the sun is setting
progressively more north each day. The opposite will occur in the opposite
season; from Tekufas Tamuz to Tekufas Teves (from the summer solstice to the
winter solstice); the moon will set further south of the sun. That is what
the Gemara means when it says that in the summertime, the moon sets to the
south of the sun, and in the wintertime, the moon sets to the north of the
sun. (This is true until the last four days before the solstice, since 9
days from then the sun will begin to return to the opposite side of the
western horizon, and so will the new moon which trails the sun by 9
degrees.)
This is a novel interpretation of the word "summertime" ("Yemos ha'Chamah"),
a term which normally refers to the period from Tekufas Nisan to Tekufas
Tishrei (the beginning of summer until the beginning of winter, i.e. from
the spring equinox to the autumn equinox), and not from Tekufas Tamuz to
Tekufas Teves (from the middle of summer until the middle of winter, i.e.
from summer solstice to winter solstice). However, Rabeinu Chananel cites a
Yerushalmi which supports this interpretation, clearly stating that the moon
is to the north of the sun between Tekufas Teves and Tekufas Tamuz.
Some suggest that this is what Rashi means as well when he describes the sun
as moving from the north to the south. Rashi writes that the moon is always
in the south-west when it is new. He means that it is in the *western* part
of the sky (about to set), and it is always *south* of the sun before it
sets (i.e. behind the sun, because the sun and moon always set over the
western horizon while traveling at an angle from south to north [in the
northern hemisphere], and the new moon by definition must follow behind the
sun -- see also Insights to 20:3:b:2).
Why does Rashi write that "most" of the summer months the new moon is
setting to the south? The moon sets to the south of the sun *all* of the
summer months!
The first answer is that at the end of the "summer" season, within about
four days of the winter solstice, the moon sets where the sun will be
setting five days *after* the solstice, which is in the other direction
(north of where the sun is setting now, and not south), as we explained
above. The second answer is that the moon has another movement that is
independent of the sun, because it does not orbit in *exactly* the same path
as the sun (the ecliptic). The path of the moon is inclined at about 5
degrees to the path of the ecliptic. Whether the moon travels to the north
of (above) or south of (below) the ecliptic varies over an 18 year cycle
known as the "Saros cycle." (The Rambam discusses this at length in Hilchos
Kidush ha'Chodesh, ch. 16.) Thus, on rare occasions the moon's 5 degree
incline south of the ecliptic at the time of the new moon will offset its 9
to 15 degrees distance from the sun which causes it to set north of the
point of sunset from Teves to Tamuz. Because of its southern inclination, it
can end up setting slightly to the south of the point of sunset and not to
the north (and vice versa from Tamuz to Teves).
(This is not a completely satisfactory answer for Rashi, though, for a
number of reasons. (1) Rashi appears to translate "Yemos ha'Chamah" as the
period from Tekufas Nisan to Tekufas Tishrei, and "Yemos ha'Geshamim" as the
period from Tekufas Tishrei to Tekufas Nisan, unlike Rabeinu Chananel. (2)
According this explanation, the Beraisa's phrase "south of the sun" has an
entirely different meaning from the identical phrase in the Mishnah as Rashi
explained the Mishnah. Rabeinu Chananel, in contrast, seems to have
understood the Mishnah's phrase in a manner consistent with his explanation
of the Beraisa -- see also Bartenura and Perush ha'Mishnah of the Rambam.)
(c) The PERUSH HA'RAMBAM on Maseches Rosh Hashanah explains the Gemara in a
simple manner. As Rashi explained, the sun sets exactly at the midpoint of
the western horizon in Tekufas Tishrei (the autumn equinox), and it sets
south of the midpoint of the horizon from Tekufas Tishrei until Tekufas
Nisan (the spring equinox). From Tekufas Nisan until Tekufas Tishrei, it
sets to the north of the midpoint of the western horizon. At the time that
the sun sets to the northern part of the horizon, the new moon -- which is
only a few degrees behind the sun -- also sets along the northern half of
the horizon. When the Beraisa says that it sets to the north in the
wintertime, it means that both the *sun and the moon* set along the northern
half of the horizon from Tekufas Nisan to Tekufas Tishrei (not like the
Yerushalmi). The Beraisa is talking about both the sun and the moon, and it
is referring to the north or south of the western horizon and not to the
moon's position relative to the sun.