Most recently, in January of 2003, after repeated postponements, Colonel Ilan Ramon, the first Israeli astronaut, joined a crew of NASA astronauts aboard the space shuttle Columbia on a mission that ended in tragedy sixteen days later on February 1st. Kosher food of a type that can be reconstituted in space was prepared for the Jewish astronaut by a company in Illinois. He also consulted a rabbi identified with the Lubavitch movement serving in the vicinity of Cape Canaveral with regard to the proper method of determining when to observe Shabbat. Colonel Ramon indicated to one reporter that he was not strictly Sabbath observant and would also find it impossible fully to observe Shabbat during his mission in space, but that he nevertheless felt that in participating in the space program he was "representing all Jews and all Israelis" and therefore should endeavor to conduct himself accordingly.²

The first rabbinic authority to address the question of time at the polar regions was the eighteenth-century scholar R. Jacob Emden whose opinion gained wide currency due to its citation in Sha'arei Teshuvah, Oraḥ Hayyim 344:1. R. Jacob Emden is quoted in that source as ruling that "those traveling below the polar region where the day is prolonged into a month or two months and [in some places] six months should count six days of our twenty-four equal hours," i.e., the advent of Shabbat should be deemed to occur after six periods of twenty-four clock hours have elapsed. In context, the implication of Sha'arei Teshuvah's citation of R. Jacob Emden's view is certainly that the seventh cycle of twenty-four hours is to be regarded as Shabbat in every respect. However, a careful examination of R. Jacob Emden's comments in his Mor u-Kezi'ah 334 in their entirety reveals a certain ambiguity in Rabbi Emden's position. Mor u-Kezi'ah comments:

But Mor u-Kezi'ah says something astoundingly different. He rules that the week commences with the arrival of the traveler who then counts six days before sanctifying the seventh. Apparently, every traveler begins calculating his own weekly cycle upon arrival regardless of which day of the week it might be elsewhere on the globe.³ The resultant situation is certainly anomalous: Not only do two travelers observe Shabbat on two different days but neither of them observe Shabbat on the day of the week on which it is observed by Jews elsewhere in the world!⁴

It seems to this writer that Mor u-Kezi'ah regarded the establishment of halakhic time, and hence of the Sabbath, in the places under discussion to be a matter of unresolvable doubt. To be sure, as clearly enunciated by R. David ibn Zimra, Teshuvot ha-Radvaz, I, no. 76,⁸ determination of the onset and conclusion of Shabbat is determined locally. Leviticus 23:3 mandates that the Sabbath be observed "in all your habitations." That phrase is understood by Radvaz⁹ as signifying that the onset and conclusion of Shabbat is to be determined in accordance with sunset at each particular "habitation."¹⁰
Shabbat is designed as a "sign between Me and between you" (Exodus 31:13) and accordingly, is to be observed during the period representing the culmination of six days of labor in each person's locale. The Sabbath day, which includes a period of darkness and a period of daylight, is roughly twenty-four hours in length in all places other than in the extreme northern and southern regions. As a result, the Sabbath is observed on the same day of the week in all parts of the globe. Accordingly, Mor u-Kezi'ah assumes that in locales in which that cannot be the case there is no discernible method for determining the days of the week. Hence, determination of the advent of Shabbat remains either a matter of irresolvable doubt or, alternatively, there is no concept of halakhic time in such places. Therefore, Mor u-Kezi'ah rules that a person finding himself in such a place faces a problem that is no different from that confronting a person lost in the desert or confused with regard to a sequence of days and must conduct himself in an identical manner. That is precisely the import of Mor u-Kezi'ah's concluding phrase "in the manner indicated earlier with regard to one who travels in the desert," i.e., he may perform no forbidden act on any day of the week and must recite kiddush and havdalah on the seventh day of every seven-day cycle subsequent to his arrival.

Perhaps the most widely cited source with regard to Sabbath observance at the North Pole is a note authored by the nineteenth-century authority R. Israel Lipschutz and published in his classic commentary on the Mishnah, Tiferet Yisra'el, as an addendum to his commentary on the first chapter of Berakhot. Tiferet Yisra'el carefully distinguishes between places such as his own city of Danzig, as well as Copenhagen and Stockholm, in which there is always at least a brief period of dusk, and places further north in which "there is no night at all but only daylight during the months of June and July." He also expresses concern with regard to people who sail close to the North Pole in order to catch "whalefish" because in that locale there are a number of months during the summer in which there is only daylight. Tiferet Yisra'el does not cite Mor u-Kezi'ah but adopts a position that is remarkably similar to that of R. Jacob Emden in one salient aspect. As did his predecessor, Tiferet Yisra'el rules that each twenty-four hour period constitutes a day. In support of that conclusion he draws upon the fact that the sun can be observed as completing a full circle above the horizon each twenty-four hour period. However, his position is fundamentally different from that of Mor u-Kezi'ah in that Tiferet Yisra'el maintains that the day is determined objectively rather than individually by each traveler. Thus throughout the year Shabbat occurs at the North Pole the same day as it does on the rest of the globe and is objectively determined by the "revolutions" of the sun in the sky. In the polar regions the sun is observed as moving in a circular pattern and completes a full circuit in the overhead sky every twenty-four hours. Each of those twenty-four hour circuits, maintains Tiferet Yisra'el, represents a single day.¹² However, Tiferet Yisra'el fails to identify a phenomenon that might serve to demarcate successive days during the polar night when the sun is entirely concealed.¹³

The anonymous interlocutor is further quoted as rejecting his own proposed thesis because the Palestinian Talmud, Kelayim 9:13 and Ketubot 12:3, reports that a similar phenomenon occurred on the Friday on which the funeral of R. Judah the Prince took place. However, the Palestinian Talmud reports that on that occasion the participants in the funeral considered themselves to have desecrated the Sabbath. The latter statement, he argues, establishes that the demarcation of successive days does not necessarily depend upon the declension of the sun below the horizon.²⁶

The reason why such a thesis does not merit consideration is not immediately evident, particularly if there is no intrinsic reason why a day must be approximately twenty-four hours in duration.²⁷ The only reason that suggests itself to this writer is that, although the beginning and end of a day and intermediate divisions of the day certainly depend upon local sundown and sunrise, the identity of any given day is the same throughout the globe with the minor exception presented by the necessary adjustment for the dateline. The dateline phenomenon is not an exception to the basic principle because that phenomenon is the logical result of the movement of the sun as perceived in all places throughout the globe except for the polar areas. The notion that in one locale it may be Shabbat while in another it may be some time on Friday and in another locale it may be some time on Sunday is readily understood. But a thesis that will posit that Shabbat can occur in some geographic area on a day that is, for example, Wednesday elsewhere is incompatible with the very nature of a calendrical system.

Thus, since a day is defined as the period between sunset and the following sunset, allowing for variation in its beginning and end, the day of the week is the same throughout the globe. Since sunset and sunrise do not occur in approximately twenty-four hour sequences in the polar areas, any particular polar day could not be identified as the same day of the week recognized in other locales. Accordingly, there is no "day" at the North Pole and hence there are no festivals. Since there is no day to be divided into hours, there is no obligation with regard to reciting the Shema or any of the time-bound prayers.²⁹

Teshuvot Ri mi-Gash, no. 45, observes that Tiberias and Sepphoris are really in close proximity to one another but that Tiberias is in a valley and Sepphoris is located at the top of a mountain. For that reason there was a significant discrepancy in the time of sunset in those two cities. The higher one's elevation the more one can see of the curvature of the earth with the result that a person at the top of a mountain will not see the declining sun disappear from sight until sometime after the sun is observed to have set below the horizon by a person standing at the base of the mountain. The Gemara's statement indicates that Shabbat begins later in Sepphoris than it does in Tiberias because sunset—and hence time—is determined at ground level. Ground level is not uniform; rather it depends upon the topography of the area and hence may be represented by the bed of the valley or the top of the mountain.⁴¹
Accordingly, the beginning and the end of the day at the mountain top is different from the beginning and the end of the day in the valley.⁴²

Despite the weight of opinion to the contrary, R. Menachem Kasher, Torah Shelemah, I, Bereishit 1:430, expresses doubt with regard to this matter. Without citing sources, he suggests that Shabbat observance requires the observance of a period of a full twenty-four hours. He further argues that on Yom Kippur a fast of a full twenty-four hours is required by virtue of the fact that Scripture requires that on Yom Kippur "you shall afflict yourselves" and proceeds to prescribe the observance of Yom Kippur "from evening to evening" (Leviticus 23:32).⁶⁶. That position is reiterated by Rabbi Kasher in his Kav ha-Ta'arikh ha-Yisra'eli, chapter 58. In chapter 73 of the same work Rabbi Kasher reiterates that view with a slight variation: he questions whether performance of a forbidden act of labor under such circumstances involves a capital transgression or if it is only a negation of the positive obligation to rest on the seventh day. Elsewhere in Kav ha-Ta'arikh ha-Yisra'eli, chapters 39 and 53, Rabbi Kasher argues that there is a "personal" Shabbat at the end of every seven day cycle that is independent of solar phenomena.⁶⁷See also R. Menachem Kasher, “Shabbat Bereshit ve-Shabbat Sinai,” pp. 400–401 and p. 410. In chapter 53 he argues that observance of that "personal" Sabbath is mandated solely by the positive commandment regarding rest on the seventh day but not by the negative prohibitions entailing capital punishment.⁶⁸