Thank you for all your responses to my questions, which I very much appreciate.
Daf 12 brings up something which I've had difficulty understanding for a long time. In Hallacha today, what is the margin of error for a time measurement? (the daf addresses what it was then). For instance, is the time Shabbat comes in accurate to the second? Can it be made accurate to the millisecond? (for instance for some computer system which one wants to make work until exactly Shabbat).
(I have the same question about places the Gemara says "exactly [some measurement]" when it is not time). Is distance accurate to the millimeter? To the micrometer? How about quantity?)
Daniel Moskovich, Kyoto, Japan
(a) The Gemara is discussing the error we can expect from someone trying to tell the time according to the sun's position in the sky. Obviously nowadays we would allow much less room for error since people generally tell the time with the use of clocks and watches meaning that they can be expected to give more accurate estimations of the time.
As far as Shabbos is concerned there are two points to consider. We know Shabbos begins at sunset which is accepted to be at the time that the sun has completely disappeared from our view. We can estimate this time very accurately but since it depends on our observation of the suns disappearance, and this may vary due to atmospheric conditions, it is not possible to rely on these estimations up to the last millisecond.
Secondly there is a Mitzvah to add on to Shabbos (le'Hosif Min ha'Chol Al ha'Kodesh) so even if one could rely on the time of sunset to the millisecond one would have to stop work before sunset.
(b) Generally speaking, times and measurements given by Chazal are exact as explained in Gemara Rosh Hashanah 13b. Therefore, if someone's Lulav was a fraction less than four Tefachim it would be Pasul. However there are cases where the Chachamim accepted that the Torah did not expect us to measure exactly. This is bacause the Torah was given to man and its instructions were intended to be kept within the realms of mans capabiltities at the time it was given (see Sha'ar ha'Tziyon on Mishnah Berurah 372:18). Some suggest that this is a Halochoh le'Moshe mi'Sinai (ibid.).
Rav Moshe Feinstein in Igros Moshe (YD 2:146) explains that the Torah did not expect us to examine the Shechitah knife with a microscope or to check our food with a microscope for bugs. The laws of the Torah rather depend on what a person can see. He brings a Gemara in Bechoros (17b) that the when the Torah commands us to make vessels in the Mishkan to specified sizes it is sufficient if we do so to the best of our ability even if this will not be exact. This rule is known as Lo Nitnah Torah l'Malachei ha'Shares, and Iy Efshar le'Tzamtzem.
(c) Where the Torah tells us to have an exact measure we can rely on our best estimation as explained. However where the Torah tells us a minimum measure we must be sure to have at least that measure specified.
(d) The above holds true for quantity as well. See Tosfos Menachos 10b.
Dov Freedman
(a) What you heard about fruits not changing is indeed recording in the Teshuvos ha'Ge'onim.
(b) Regarding the different sizes of fruits from different trees, the Mishnah in Kelim 17:6-8 explains that the Halachah l'Moshe mi'Sinai that taught us these measurements included whether the measurement should be taken from a large, small, or medium fruit.
(c) The Talmid of the Noda bi'Yehudah was Rav Eliezer Flekles, the Teshuvah me'Ahavah. For more about his comment, and about the Noda 'bi'Yehudah's explanation in general, see our Insights to Pesachim 109:1 (included in our recent hardcover collection of Insights to Pesachim).
Be well,
Mordecai Kornfeld
Kvod HaRav,
Thank you always for your insightful and enlightening answers which greatly enrich my studying.
(a) How does this apply to cases where we ask for something to be "exactly" the same as something else? For instance in dinei nezikin, when something is found between two rashuyot, and if it is mostly in one or mostly in the other we have one psak, and another psak if it's "just in the middle". Today, it's ein ladavar sof- somebody can always come and measure with some fancy laser measuring device and prove that the object was 0.000001 percent more in his rashut (for example). Would then the Hallacha governing "exactly between" situations be rendered irrelevant to practical Hallacha? Or is there some minimal error below which we say "it is exactly in-between the rashuyos" or cities or whatever the sugya is discussing?
(b) Another example which bothers me a lot is that I have heard that when the baal habayis makes kiddush and I am a guest, it is best to recite the kiddush belachash together with him. But if I am a tiny bit off, I run into trouble. Would it be enough for me to try to stay together with him to the best of my abilities? Or would the risk of being infinitesmally off-time (in the best case) make this method invalid?
With thanks,
Daniel Moskovich
(a) As explained, times and measurements given by Chazal are exact. Similarly, where a Rov (majority) is necessary, a simple majority will suffice. The Poskim (Tur and Shulchan Aruch YD 21:1 Radvaz Vol. 1:12) rule that even a majority that can be identified only by measuring is sufficient. They say that even a majority of a Kol Shehu is considered a Rov. The Rem"a in Darchei Moshe (ibid.) cites the last Ramban in Parshas Shemini as a source. We may infer that any measurable majority is accepted as a legitimate majority.
As for measuring equals, see OC 648:11 where two opinions are quoted as to whether we can rely on the accuracy of our measuring to ascertain that measured items are in fact equal. This depends on the Machlokes in Bechoros 17b with regards to Efsher le'Tzamzem b'Yedei Odom. The Ravad is of the opinion, that we cannot rely on measurement to ascertain that two things are equal, and therefore even if they seem to be equal, we must take into account the possibility that one may be slightly larger than the other. Whether the Rava"d would be of this opinion in the modern era is difficult to know, but it is possible that he would argue that even if we view two things as equal someone with superior capabilities may prove us wrong.
The Mishnah in Bava Basra 23b says that where the fledgling is equidistant from two seperately owned dovecots the halacha is Yachloku. According to the Rava"d this is because we cannot decide to which one it is closer. According to those who hold Efsher le'Tzamzem this is because the Halachah of something that is exactly in the middle is Yachloku. If one person could show us that the fledgeling is nearer his dovecot even by the smallest of measurements this would suffice for him to be Zocheh.
However,if we require two things to be equal so that they should be similar to one another, we do not require them to be exactly equal. See Drisha YD 309.
(b) Mishnah Berurah 193:5 says this is the correct thing to do (although it is not the prevalent custom). Rebbi Akiva Eiger (vol.1:7) says that the one who says it quietly is considered to be making his own Kidush and is not Yotzei with the Kidush of the Ba'al haBayis. If so it would not matter if he said the words quicker or slower than the one making Kidush. Furthermore as long as a person concentrates on what he hears he would not invalidate the Kidush by being out of synchronization with the Mekadesh.
Dov Freedman