Q&A: Rabbeinu Tam’s Method
Rabbeinu Tam’s Method
Question
I am stringent about ending the Sabbath according to Rabbeinu Tam. When I recently learned the passage, I noticed something interesting. Essentially, Rabbeinu Tam’s entire method is based on an astronomical error: that the earth is flat and has a certain “thickness,” and from the first sunset (our sunset) the sun disappears from our sight, and it takes it another hour to pass through the “thickness” of the earth, and all of that is still considered daytime.
Of course, according to accepted science today, it is clear that the earth has no such thickness, and that the sun disappears as a result of the earth turning in another direction.
In light of the passage, does the Rabbi think there is still reason to be stringent like Rabbeinu Tam even though the foundation is incorrect, since many medieval authorities (Rishonim), and also the Shulchan Aruch, followed Rabbeinu Tam? Or once it is not true, then even if Elijah the Prophet were to tell us to be stringent, we would not listen to him?
Maybe there are other explanations for this approach that have not been disproved, and then the difficulty disappears. Has the Rabbi written about this topic at all? And what is his view?
Thank you very much
Answer
I haven’t gone into this topic. It is clear that if you are convinced that his calculation is based on an error, then there is no point in being stringent like him. Just note that even if one assumes the earth is flat and has thickness, that does not necessarily mean the calculation is mistaken. It is a model, and it still describes the sun’s passage from one side to the other. It does not matter whether that side is straight or curved.
With Heaven’s help, 19 Kislev 5785
Linon — hello,
The rationale in Rabbeinu Tam’s method is the parallel (mentioned in Pesachim 93) between the interval of “the walking time of four mil” between dawn and sunrise, and the time between sunset and the appearance of the stars. The reason is that, because of the earth’s rotation on its axis, the rays of the sun illuminate the earth long before the sun itself is visible, and for a long time after it is covered.
See the words of Tosafot Rid, cited in Rabbi Elchanan Sabato’s article, “A Conceptual Reversal in Rabbeinu Tam’s Method Regarding the Time of the Appearance of the Stars,” p. 151 and onward (on the Asif website).
Best regards, Fishel