I wonder if you could help explain parts of 3 Tosfos on 23b-24a as part of the interesting astronomical sugyos.
(a) 23b Tos DH Lo, the last four lines "V'im..."
(b) 23b Tos DH Oy, "V'Kashya..." - what is the kashya?
(c) 24a Tos DH Toni, what is the Kashya and what is the Teretz?
Thanks in advance and Kol Tuv
Meir Eliezer Bergman
Manchester UK
(a) Tosfos on 23b DH Lo says that all of a walled city is considered like one area of four Amos with regards to Techum. Tosfos , however, go on to say that we find elsewhere that even outside the city walls is considered like one area of four Amos. Tosfos second instance of this, is that the Mishnah in Eruvin (60a) says, that if someone put an Eruv in the area outside the city, but within the houses in its peripheral area (situated within seventy and a bit Amos of the city), he has achieved nothing. This is because even without his Eruv, the whole area was considered like four Amos, even though the peripheral area is certainly outside any walls the city may have.
(b) Tosfos on 23b DH Oh. Tosfos understood that the Gemara means to ask if the name Beis Yazek was given before the Takanah of Raban Gamliel, and was an expression of discomfort due to the feelings of captivity, which emanated from being confined to a small area, or after the Takanah in which case it would not refer to discomfort at all. The Gemara brings a proof from the fact that festive meals were provided that there was no feeling of discomfort, indicating that the name was given after the Takanah. Tosfos asks that this is not a proof, since even before the Takanah the Beis Din had to provide festive meals for those in the room. See Aruch la'Ner, Teshuvos Maharashdam (CM) and Avraham Yagel for alternative explanations)
(c) Tosfos on 24a DH Aval asks that Rebbi Yochanan said on 23b that the dark side of the moon never faces the sun. However, the new moon is seen in the west and in the evening (Rashi 23b on the Mishnah) and its dark side faces south-east (Maharshah 24a) so that when the moon is "Lifnei ha'Chamah", in front of the sun, which in the evening is setting towards the north-west, the moon is north of the sun and its dark side, which faces south east will be towards the sun.
Tosfos answers that the sun and moon have different orbits, in a way that the moon is enough lower than the sun that even when the moon is north if the sun its dark side does not appear to face the sun. Tosfos informs us that this is simple to those who are well versed in this science, form which we may conclude that for others it is far from simple. The Chachmas Manoach (Hagahos at the back of the Shas from a contemporary of the Maharshal) discusses some of the problems with this Tosfos.
Dov Freedman