Q&A: A Question in Tractate Sukkah
A Question in Tractate Sukkah
Question
Hello,
A question about the straightforward meaning of the Talmudic text, with a possible tilt toward physics—I’ll allow myself, given the circumstances, to ask and trouble you.
In Sukkah 2b, the Gemara says that Rav Hanan’s statement does not fit any of the Amoraic positions mentioned on page 2a (because of awareness, shade, and impermanence). At first glance, that statement seems very similar to the one above it (Rav Huna), and it does fit the view that the issue is shade, except that there is a "dispute about the reality" regarding the extent/meaning of the shade that is created. In the commentators I saw, there is no discussion of this, and it seems obvious to them that shade has no significance here.
A. I’d be happy to get the plain meaning, because the explanations I have don’t satisfy me.
B. Physically speaking, is there any logic at all to the claim that at our latitude, six handbreadths by six handbreadths at a height of about twenty cubits realistically do not create shade? Either in general or inside the sukkah? (As opposed to four cubits.) (My knowledge of math and physics doesn’t let me set up the calculation…)
Thank you very much
Answer
I don’t really understand the difficulty. It’s clear to me that the difference between the two statements is only quantitative. Four by four cubits creates shade below even at a height of about twenty cubits, and therefore fits Rabbi Zeira; but six by six handbreadths does not create shade below, and therefore Rav Hanan fits no one. That is clearly the Gemara’s physical assumption. I think that if you want to check this against reality, that has nothing to do with the relation between the two statements. You can ask separately about each one whether it stands the test of reality (I’m not sure).
But it seems to me that even an empirical check is not what you are describing. An actual real-world check is difficult, since light does not travel in a sharp geometric line. It disperses all the way to the ground, and if you look at the ground (though this depends on the dispute between Rashi and Tosafot whether in the law of “its sunlight is greater than its shade” the measurement is made on the ground or above), you will not see a square of light or of shade. Therefore, in my opinion, this cannot really be checked physically (this is not geometric optics). We are dealing with an estimate given by the Sages, assessed in terms of general plausibility. Is there enough light on the ground from four by four cubits, or from six by six handbreadths, taking into account its dispersion on the way down? In other words, how dark is the gray on the ground? The degree of darkness determines whether this counts as shade or not.
The same applies to “its sunlight is greater than its shade” (according to the views that measure this below): clearly, on the ground you do not see illuminated and shaded patches corresponding to the gaps in the roofing, as one might have understood from the Gemara. On the ground, what you actually see is gray, so this is a general average measurement of how gray it is (between black and fully lit), and that is what determines it.
[As an aside, I also don’t know whether it is right to ask this specifically about the latitude of the Land of Israel. Why should that specifically be decisive? After all, these are Babylonian Amoraim. I seem to recall that the commentators discuss this, but I don’t remember now who or where.]
Bottom line: as with many determinations of the Sages, it seems to me that here too we are not dealing with something fixed and measurable, but with a general estimate meant to establish Jewish law in a sharp and workable way.
I know that many commentators do treat this as geometric optics, but in my opinion that is not plausible.