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Time, Space, and Size
by Rabbi Berel Wein

In halacha, measurements of time, space and size are essential ingredients of proper observance of mitzvot and ritual obligations. There are set time limits for the recitation of prayers and for the entry and exit of the Sabbath and holy days, there are minimum sizes for the required halachic consumption of certain foods and drinks and there are space (height, width, etc.) measurements that apply to laws of the Sabbath and of a succah, to name just two examples. In a world that did not as yet include accurate time measuring devices, micrometers, the use of calculus or computers, the standards for such measurements of time, space and size were somewhat vague. The Talmud deals with all such problems by offering the size of an olive, an egg, a date, a mouthful (both cheeks full), a barley seed, as the standard for measuring size regarding food and drink, as well as matters of ritual purity. These standards also served as the basis for calculating volume, such as the amount of pure natural water required for a mikva - the ritual purification pool. Space and size were also calculated by using the length or breadth of a finger or arm. The common factor in all of these talmudic measurements was that no tools were required to arrive at the correct result. Everyone had a finger and an arm, a barley seed, a date, an egg or an olive. Time was measured by the length of the day from sunrise to sunset or, in the alternative rabbinic opinion, from dawn until the appearance of three medium sized stars in the evening. Though all of these methods of measurement remained somewhat inexact, in everyday application they were, nevertheless, practical and universal and allowed all Jews to fulfill their halachic duties with a degree of certainty and confidence.

The Mishna and Talmud already mentioned certain measuring units that were common in their times. Hin, saah. kav, were such measuring units, though their exact sizes and dimensions were not clear to later generations. With the advent of more exact technology in the Middle Ages, the measuring units in halacha took on greater accuracy and definition. The clock of fourteenth century Europe was a vast improvement over the water clocks and sand hourglasses of the earlier Middle East. Times of prayer and the length of the Sabbath and holy days now became regulated by watches and time measuring machines and not by sighting stars and daybreak. Measurements of size, distance and volume were translated into units of ounces, grams, feet and meters. Though these new measuring units were meant to insure greater accuracy and uniformity in observance of ritual, their presence oftentimes led to rabbinic disputes and varying opinions on what the correct ritual practice should be. The most famous of these issues occurred in the eighteenth century when the great scholar and rabbi of Prague, Rabbi Yechezkel Halevi Landau (known by the name of his great work of scholarship Noda B'Yehuda), declared that based on his calculations the egg of talmudic times must have been twice the size of eighteenth century eggs. Thus, in effect, he doubled the size and volume requirements for the observance of many mitzvot, such as eating matzo on the Seder night of Pesach. Though other rabbinic scholars originally contested his opinion, it soon gained wide acceptance throughout the Jewish world and remains influential even today.

As measuring tools of space, size and time became more exact; the halacha relied on these new tools to determine its requirements for ritual observance. Two of the leading scholars of twentieth century Jewry, Rabbi Chayim Na'eh and Rabbi Avraham Yeshayahu Karelitz (Chazon Ish), formulated rigorous and exact standards for size, space, volume and time as far as halachic requirements for ritual performance of mitzvot is concerned. The standards of Rabbi Karelitz are pretty much universally accepted today, though the opinions of Rabbi Na'eh - which are more lenient - are always taken into consideration as well, especially in extenuating circumstances. More than a decade ago, the opinions of Rabbi Landau and of Rabbi Karelitz were challenged in a lively discussion in an Israeli Torah journal by a professor of physics at Bar Ilan University. This provoked a lively, almost heated, debate on the pages of that journal and served to cast further light on the topic. As technology continues to advance and provide us with even more exact means of measurement of size, space, time and volume, the halacha will undoubtedly take these means into account in establishing the necessary requirements for exact observance of mitzvot.

Reprinted with permission from Rabbi



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