ANSWERS TO REVIEW QUESTIONS
prepared by Rabbi Eliezer Chrysler
Kollel Iyun Hadaf, Jerusalem
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Eruvin 56
ERUVIN 56  was generously dedicated by an anonymous donor in Los Angeles.

Questions
1)
(a) One squares a round town in the directions of the world (i.e. so that
the north side of the town faces due north, the east side, due east etc.
(b) Taurus is the sign by which it is possible to gauge due north, and
Scorpio due south.
(c) When Rebbi Yossi refers to ...
 ... 'Mehalchasan'  he means the Mazal's course by day.
 ... 'Mesavevasan'  he means its course by night.
(d) According to Rebbi Yossi, one gauges ...
1. ... the north side of the town  by drawing a line from the point where
the sun rises in midsummer (on the north east) to where it sets (on the
northwest).
2. ... the south side  by drawing the line from the point from where the
sun rises in midwinter (on the south east) to where it sets (on the south
west).
3. ... the east side  by noting where the sun rises and sets in Tekufas
Nisan (the spring equinox) and Tishri (the autumn equinox), because then it
rises and sets exactly in the middle of the east and west sides
respectively.
2)
(a) A full solar year lasts three hundred and sixty five and a quarter days.
(b) The luminaries were placed in the sky  at the beginning of the first
Tuesday night following the creation of the world, at the beginning of Nisan
(it is not clear on which date).
(c) In the following year ...
1. ... Tekufas Nisan will have fallen one a quarter days after that, at
midnight of the first Wednesday at the beginning of Nisan.
2. And the year after that, it will fall at sunrise of Friday morning at the
beginning of Nisan.
3)
(a) Tekufas Tamuz (the summer solstice) will always fall either at one and a
half hours or at seven and a half hours, either after sunrise or after
sunset.
(b) Tekufas Teves (the winter solstice) will fall either at four and a half
or at ten and a half hours after sunrise or sunset.
4)
(a) When the Gemara says 'Ein Tekufah Mosheches me'Chaverta Ela Chatzi
Sha'ah'  it refers to the difference in time between the rising of the
Mazal from one Tekufah to the next. This works out in the following manner:
There are seven Mazalos (constellations)  Kochav, Levanah, Shabsi, Tzedek,
Ma'adim, Chamah, Nogah, each of which dominates from the time it appears
until the next Mazal appears exactly one hour later. Each Tekufah lasts
ninety one days plus seven and a half hours. Now since the ninety one days
are divisible by seven, and so are the seven hours, it transpires that if
Kochav (for example) ruled at the beginning of Tekufas Nisan, then Tekufas
Tamuz would arrive when Kochav was half way through her 'reign', and it will
be Levanah who will rule at the beginning of Tekufas Tishri and so on. Each
Tekufah will find the Mazal half an hour in advance of where it was at the
previous Tekufah.
(b) When the Tekufah of ...
1. ... Nisan falls in the Mazal of Tzedek  then it causes the trees to
become broken.
2. ... Teves falls in the Mazal of Tzedek  it causes seeds to dry up.
(c) This speaks when Tzedek dominates at the time of the Molad (the birth of
the new moon).
56b56b
Questions
5)
(a) When the Beraisa says that, after one has squared the town, one squares
it again  it means that, by a town of two thousand Amos, after one has
squared the circle (to form a square of two thousand Amos by two thousand
Amos), one measures the Techum by forming four squares of two thousand Amos
square (one on each side of the square of the town), completing the large
square by filling in the four corners.
(b) One gains by each corner ...
1. ... of the town  four hundred Amos (the length of the diagonal that the
square is in excess  of the circle).
2. ... of the Techum another four hundred Amos.
6)
(a) One thousand Amos surrounding the Levi'im's town  had to remain Migrash
(an unused plot of land which served to beautify the town).
(b) The outer thousand Amos  was designated for fields and vineyards (for
the Levi'im's use).
(c) 'Meshucha'a' means  the landmeasurer.
(d) According to Bar Ada, who establishes the Beraisa (which gives the
Migrash as a quarter of the area surrounding the Levi'im's cities) by a town
of two thousand Amos by two thousand Amos, we can divide the entire two
thousand by two thousand Amos area surrounding the town into two times
sixteen blocks (one for the area adjacent to the town, the other to fill in
the corners), each block a thousand by a thousand Amos. Of these blocks,
twelve will surround the town to serve as the Migrash, leaving twenty two
for fields and vineyards.  But twelve out of thirtytwo is more than a
*third*, asks the Gemara, so how can the Beraisa refer to the Migrash as a
*quarter*?
7)
(a) The Gemara raises the fraction from *more* than a third Migrash to
*exactly* a third  by adding the four blocks of a thousand by a thousand
Amos of the town itself to the field and vineyard section of the entire
area, making it twelve out of thirtysix blocks (exactly one third).
(b) We arrive at the stated quarter  by establishing the case by a circular
town, in which case the Migrash too, will be circular (instead of the square
town which we discussed until now). Since a circle is a quarter less that
the square that surrounds it, we will have reduced the sixteen blocks of a
thousand by a thousand Amos (which previously took up the town together with
the Migrash), to twelve  three quarters (nine) of which are ascribed to the
Migrash. Nine out of thirtysix (i.e. the unchanged square of two thousand
Amos square that surrounds the town) is a quarter.
(c) According to Abaye too, we are speaking about a round town  and the six
blocks of a thousand Amos which comprise the Migrash, make up one quarter of
the twenty four blocks of the total area surrounding the town. The advantage
of Abaye's explanation is  that it is not necessary, according to him, to
include the town in the reckoning.
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