Reference of Measurements in Halacha
Revision as of 14:05, 6 February 2012 by YitzchakSultan
- According to Ashkenazim, all sizes are measured in volume and not weight. However, according to Sephardim the actual halacha is that measures are in volume but the minhag is to follow the measures in weight. 
- There’s a dispute in the rishonim whether the Kezayit (olive size) is a half or third of a KeBeytzah (egg size), and the halacha follows the opinion that a Kezayit is half a KeBeytzah. 
- According to Rav Chaim Noeh, the Kezayit for Deoritta measures (eating Matzah) and Bracha Achrona is 25.6 cc (in volume). Nonetheless because food stuck in between one's teeth doesn't count towards a Kezayit eaten one should make sure to have 28.8 cc. Regarding a Kezayit for derabbanan measures (eating maror) the Kezayit is 17.3 cc.  The Chazon Ish’s opinion is that the Kezayit is 33.3 grams (1.3 oz). 
- The minhag of the world and many other authorities is to follow Rav Chaim Noeh’s opinion. 
- If one ate between a third and a half a KeBaytzah one should not make a Bracha achrona because of safek Brachot. Therefore, one should have less than a third and not make a Bracha achrona or more than a half and make a Bracha achrona. 
- On מצות Deoritta such as eating Matzah one must be strict to hold a Kezayit is a half a Kebaytzah. However, regarding מצות Derabbanan it’s preferable to hold that a Kezayit is a half a kebaytzah, however, one may rely on the opinion that a Kezayit is a third a kebaytzah. 
Kedi Achilat Pras
- See Kedi Achilat Pras (the time in which a Kezayit is considered eaten together)
- According to Rav Chaim Noeh, the KeBaytzah is 55cc and according to the Chazon Ish is 100cc. 
Amah, Tefach, Etzbah
- According to Rav Moshe Feinstein, the Amah is 21.25 inches (53.98 centimeters), the Tefach is 3.54 inches (9.00 centimeters), and the Etzbah is 0.89 inches (2.25 centimeters). 
- According to Rav Chaim Noeh, the Amah is 18.90 inches (48 centimeters), the Tefach is 3.15 inches (8 centimeters), and the Etzbah is 0.79 inches (2 centimeters) 
- According to the Chazon Ish, the Amah is 24 inches (60.96 centimeters), the Tefach is 4 inches (10.16 centimeters), and the Etzbah is 1 inch (2.54 centimeters). 
- A Reviyit is a Kebaytzah and a half.  Therefore, according to Rav Chaim Noeh, the Reviyit is 86 grams (3 oz) and according to the Chazon Ish the Reviyit is 150 grams (5.3 oz). 
Kedi Shtiyat Reviyit
- See Kedi Shtiyat Reviyit (the time in which a Reviyit is considered drunk together)
- A prutah is 1/40 of a gram of silver (which is about a few cents). However, the prutah with regards to the mitzvah of returning a lost object is discussed here. 
- There is a wide range of opinions precisely when Misheyakir occurs in Jerusalem on a perfect day, when there is exactly 12 daylight hours and every seasonal hour consists of 60 minutes. The three opinions include: 35 minutes before sunrise, 60 minutes before sunrise, and 66 minutes before sunrise.
- The various opinions would then have to be extrapolated according to the region of the world and time of year. Thus, according to the commonly accepted opinion that Meshiyakir is between 50 and 60 minutes before sunrise in Jerusalem - In New York, depending on the time of the year, it could be anywhere from 56-73 minutes before sunrise.
- Many rishonim hold that Olot HaShachar is 72 minutes before sunrise on a perfect day in Jerusalem which is equivalent to when the sun is 16 degrees below the horizon for everywhere in the world, however, others hold that Olot HaShachar is 90 minutes on a perfect day which is 19.78 degrees below the horizon. 
- Mishna Brurah 456:3, Vezot HaBracha (pg 6)
- Yalkut Yosef (Klalei Brachot pg 195-202) discusses this at length
- S”A 486 rules like Tosfot and not the Rambam that the Kezayit is half a Kebaytzah and not a third.
- Shiurei Torah (by Rav Chaim Noeh, Siman 3 Seif 13 pg 191)
- Vezot HaBracha (pg 6)
- Vezot HaBracha (pg 6, Birur 1, pg 221) in name of Rav Elyashiv and Rav Shlomo Zalman that one may follow Rav Chaim Noeh’s opinion and there’s no need to be strict for the Chazon Ish’s opinion. Vezot HaBracha also mentions that such is the minhag of the world.
- Mishna Brurah 486:1
- Mishna Brurah 486:1
- Vezot HaBracha pg 6
- Sh”t Igrot Moshe O”C 1:136. writes that the Amah is 21.25 inches and one can be strict to hold that it is 23 inches.
- Shiurei Torah (by Rav Chaim Noeh, Siman 3 Seif 25 pg 249)
- Shiurin shel Torah (pg 3) by the Steipler quoting the Chazon Ish but admitting that these are approximate measures because of the need to publicize the measures but not an accurate calculation.
- Mishna Brurah 486:1
- Vezot HaBracha (pg 6)
- S”A CM 88:1 says a prutah is a half of a pearl of barley. Shiurei Torah (Rav Chaim Noeh pg 177) and Shiurei HaMitzvot (Chazon Ish pg 65) say a prutah is 1/40 of a gram of silver (which currently is about 2.3 cents). Halachos of Chanuka (Rabbi Shimon Eider, pg 38) quotes Rav Moshe Feinstein saying that a prutah is 2 or 3 cents and not just one penny. See Halachos of Other People’s Money (Rabbi Bodner pg 150) who quotes Rav Moshe regarding a prutah for the mitzvah of returning a lost object.
- Rav Moshe Feinstein in Le-Torah ve-Hora'ah Vol. 3:7
- Rav Tukaczinsky in Eretz Yisrael 1:4
- Rav Ovadya Yoseh in Yechaveh Daat 2:8
- There are two factors at work here: First, the processes of daybreak and nightfall occur faster at places near the equator than places further away from the equator. Second, the speed of these processes are also affected by the seasons.
- A common solution would be to use seasonal minutes. In order to calculate a seasonal hour, one would need to add up all the daytime minutes and then divide by 12 to get the number of minutes that are in each seasonal hour. For instance, if there were 11 hours of daylight, each seasonal hour would consist of 55 minutes. To further complicate matters, there are two ways of counting the daytime minutes: The Magen Avraham counts from dawn until nightfall with the emergence of 3 stars, whereas the Gra counts from sunrise to sunset.
- Another means for calculation, which has only recently been implemented, is to compare the level of brightness by using the relative position of the sun. For instance, it has been determined that 60 minutes before sunrise on a perfect day in Jerusalem the sun is 12.9 degrees below the horizon. Therefore, if one wanted to find the equivalent time anywhere in the world during any season, he would simply determine at what time the sun will be 12.9 degrees below the horizon in that locale on that day and that would be the extrapolated Meshiyakir.
- MyZmanim.com. These figures are determined using MyZmanim’s earliest published position of 11.5 degrees below the horizon. Unfortunately, MyZmanim.com only offers calculations based upon 10.2 degrees, 11 degrees, and 11.5 degrees but not 12.9 degrees. It is unfortunate because 12.9 degrees correlates to Rav Tukaczinsky’s 60 minutes before sunrise which, although is a very lenient position is also well collaborated and accepted.
- Sefer Zmanim KeHilchatam (Rabbi Berstein, pg 347) writes that 72 minutes on a perfect day in Jerusalem is equal to when the sun is 16 degrees below the horizon and 90 minutes is equal to 19.78 degrees below the horizon. He personally rules that one should be strict for both of these opinions for Deoritta halachas and those derabbanan halachas where safek is lechumra. He tries to prove that this is the opinion of the Mishna Brurah (92:3, Biur Halacha 163:1 D"H Berachok). However, he totally rejects the opinion that Olot HaShachar is 120 minutes before sunrise.