Rashi makes the cheshbon of calculating how the tekufah falls out in the beginning of the night on Wednesday, and this cheshbon is based on the cheshbon of Shmuel, that a solar year is 365 1/4 days.
This cheshbon of 28 years is calculated from Brias HaOlam. My question is, given that Tekufas Shmuel is known to be inaccurate, as discussed by the various meforshim, and even the calendar we use is based on the shorter Tekufas Rav Ada, wouldn't it have been obvious that in the times of Shmuel the cheshbon of 28 year cycles would be not correct, figuring that it was already about 4000 years since Brias HaOlam?
Avi Kappel, Brooklyn, New York
Dear Avi,
The question is why do we rely on Shmuel's "mistaken" calculation for Birchas haChamah and also for saying v'Ten Tal u'Matar 60 days after Shmuel's Tekufah.
First, we must realize that Shmuel did not make a mistake. Rav Moshe Feinstein in Igros Moshe, Orach Chaim 4:17 precedes his explanation with the following introduction: (free translation)
"to call following Shmuel's calculation for Tal u'Matar a mistake means you think you're bigger than all the Rabbis who are also following this "mistake" which is great haughtiness... Anything Klal Yisrael does is definitely Halachicly correct and even to have an unanswered question means nothing... But here there's no question..."
He goes on to explain that Shmuel's easier calculation is also accepted according to Halachah.
The Chazon Ish,(Orach Chaim 138:4) also speaks at length on the subject and compares it to using 3 for pi and 1.4 for a right triangle. He explains that this calculation is also part of Hash-m's Torah and is exactly His Will.
See also the Appendix at the end of the Art Scroll Schottenstein edition of Berachos which discusses this subject. The basic answer given is that Shmuel used an easy form of calculation for individuals who cannot be expected to calculate difficult fractions to know when to start saying Tal u'Matar and Birchas haChamah. However, calculations left to the Sanhedrin were kept exact like Rav Ada (i.e. decisions on years and the yearly calendar).
All the best,
Reuven Weiner