Needing a GPS to Build a Sukkah

It seems possible that there are opinions that would maintain that the maximum allowable wall height of one's Sukkah will vary based on latitude. The opinion, about to be mentioned, is not the one that is used for halachic purposes, but it is still pretty fascinating to see that some Amoraim might maintain that the 20 amos height that most people are familiar with from the first Mishna in Sukkah may be only for Sukkos located in Eretz Yisrael and could be less for those elsewhere, like here in Baltimore. This should not be disturbing considering how Mishnayos often talk from the perspective of those living in Eretz Yisrael and are not always meant to be applied exactly to locations found elsewhere. (See Tosefos Gittin 2a)

As stated above the first Mishna in Sukkah mentions that the maximum height of a Sukkah is 20 amos. There is a three way debate mentioned in the Gemara as to what is the reason for this maximum. Rebbi Zeirah is of the opinion that a schach-type roof elevated higher than 20 amos does not provide ample shade and is thus considered to be functioning improperly and the Sukkah is rendered invalid. The Gemara mentions that according to this opinion this maximum height is only for small Sukkos (i.e. 4 amos x 4 amos), but in a larger Sukkah the schach would be big enough to cast enough of a shadow below in order to be considered valid. (See Sukkah 2a-2b)

The Ritva points out that we are obviously talking about the shade that would be created by the schach at midday since in the earlier morning and later afternoon the sun is much lower on the horizon and the schach does not really provide much shade. He also mentions that we are obviously talking about a time around the beginning of autumn (when Sukkos falls) since in the beginning of summer a shadow would be cast even by higher schach since the sun is much higher in the sky. (Ritva Sukkah 2a, also see Tosefos Sukkah 22a)

That being the case it would seem that just like Rebbi Zeirah only saw the Mishna's application to small Sukkos, he would also assume it was only referring to locations in Eretz Yisrael (the author of the Mishna and Rebbi Zeirah's location). At the beginning of autumn at midday, the sun appears directly overhead for people on the equator. For every degree of latitude north of the Equator the sun appears one degree lower and toward the southern horizon. Thus, in Eretz Yisrael, located at approximately 32 degrees north, the sun will appear to be 58 degrees high toward the south. Since the entire halacha is a function of the shade cast which is a function of the sun, locations south of Eretz Yisrael will be able to have taller walls and those to the north will have a lower maximum height. In Baltimore, located at approximately 39 degrees north, the sun will only reach 51 degrees high and will, thus, not cast as dark a shadow on a 20 amos tall roof since the light is coming from less steep an angle.

As stated above, Rebbi Zeirah's opinion is not the one taken for halachic purposes, Rava's is, but it is still pretty interesting to see how global positioning could make a halachic difference.