Question in Tractate Sukkah

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asked 9 years ago

Peace,

A question in simple Gemara, with a possible inclination towards physics, I allow myself, given the circumstances, to ask and bother.

In Sukkah 2: The Gemara states that Rav Hanan’s words do not fit into any of the Amoraic methods stated on page 1 (because of knowledge, shadow, and ara’yot). Ostensibly, this mimra is very similar to the mimra above (Rab Huna) and fits the Med because of shadow, but there is a ‘dispute in reality’ regarding the breadth/meaning of the shadow created. The commentators I have seen do not relate and it is clear to them that there is no meaning here for shadow.
A. I would be happy to simplify, the explanations I have do not satisfy my mind.
B. Physically, is there any logic in the claim that at our latitude, six cubits by six cubits at a height of about an ama, realistically do not create a shadow? At all or inside the sukkah? (Unlike the cubit meter) (My knowledge of mathematics and physics does not allow me to construct the exercise…)

Thank you very much.

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מיכי Staff answered 9 years ago

I don’t quite understand the difficulty. It’s clear to me that the difference between the mimars is only quantitative. Da’d Amot creates a shadow below even at a height of about 2 ama and therefore is suitable for Rabbi Zira, but va’u Tefahim does not create a shadow below and therefore Rav Hanan is not a kaman. This is clearly the physical assumption of the Gemara. I think that if you want to test this against reality, it has nothing to do with the relationship between the two mimars. You can ask about each one separately whether it meets the test of reality (I’m not sure). But it seems to me that even a realistic test is not what you describe. After all, a realistic test in practice is difficult, since the light does not advance in a sharp geometric line. It spreads out to the ground, and if you look at the ground (although Rashi and Toss disagree on whether in the law of Hamata Rabbah Mitzilata one measures on the ground or above) you will not see a square of light or shadow. Therefore, in my opinion, it is impossible to test this physically (this is not geometric optics). This is an assessment given by the Sages that is examined in terms of general probability. Is there enough light on the ground, according to the method of calculation or the method of calculation, considering its dispersion on the way down. In other words, how dark is the gray on the ground? The degree of darkness determines whether it is considered that there is a shadow or not. The same is true for Hamata Rabbah Mitzilatha (for the methods that measure this below), it is clear that on the ground you do not see lighted and shaded sections according to the holes in the thatch, as one might have understood from the Gemara. On the ground you will actually see gray, so this is an average and general measurement of how gray it is (between black and light) and that is what determines. [In a side note, I also don’t know if it’s correct to ask this specifically about the latitude of Israel. Why does that matter? After all, we are talking about the Amoraim of Babylon. I remember that the commentators deal with this, and I don’t remember now who and where.] Ultimately, like many statements by the sages, it seems to me that here too we are not talking about something fixed and measurable, but rather about a general assessment that came to determine the law in a clear and applicable way. I know that many commentators do refer to this as geometric optics but I think that is unlikely.

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