Jews in Space, and Other Modern Halakhic Issues Class 1: Space Travel! - Teacher Edition

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.²See the London Jewish Chronicle, May 24, 2002, p. 10 and Jewish Week, July 12, 2002, p. 3. See also JTA Daily News Bulletin, July 15, 2002, p. 2.

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 Radvaz⁹A similar interpretation of that verse was earlier advanced by Seforno in his commentary ad locum. See also the interpretation of Exodus 31:16 advanced by the Zohar, Genesis 56a. The verse “And the children of Israel observed the Sabbath to make the Sabbath for their generations (le-dorotam)” is rendered by the Zohar as “to make the Sabbath for their dwellings (le-dirotam).” as signifying that the onset and conclusion of Shabbat is to be determined in accordance with sunset at each particular "habitation."¹⁰
Cf., however, Teshuvot Sho’el u-Meshiv, Mahadura Revi’a’ah, who candidly acknowledges that, in observing Shabbat according to local time “in all their habitations,” Jews do not observe Shabbat during the same time period in which the Creator ceased from the work of creation. Moreover, he regards that concept to be reflected in the otherwise problematic words of the musaf prayer: “a people who sanctify the seventh day (am mekaddeshei shevi‘i).” Jews sanctify the month and hence the festivals which are calendar dependent. Shabbat, however, is predetermined and does not require sanctification of the new moon by the Bet Din. Nevertheless, explains Sho’el u-Meshiv, since Jews must observe Shabbat “in all their habitations” at different times they are indeed a “people who sanctify the seventh day.” 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.¹²R. Kalman Kahana, Ha-Ish ve-Ḥazono (Tel Aviv, 5724), p. 100, quotes an unpublished section of the manuscript of Ḥazon Ish’s “Kuntres Yod-Ḥet Sha’ot” in which Ḥazon Ish similarly declares that, in the polar regions, the sun’s completion of a twenty-four hour circuit represents a full day and the seventh circuit is the Sabbath day. A similar opinion is also espoused by R. Yechiel Michal Tucatzinsky, Bein ha-Shemashot, p. 55, who cites that view as earlier expressed by R. Jehoseph Schwartz, Teshuvot Divrei Yosef (Jerusalem, 5621), no. 8. [See also Teshuvot Even Yekarah, no. 11, who also addresses the problem of the biblical reference to “days” prior to the creation of the sun and comments that the biblical “day” is to be defined as the length of time required for the earth to make a complete revolution on the axis, i.e., twenty-four hours.] However, neither Rabbi Tucatzinsky nor Ḥazon Ish offer a clue with regard to the point in the sky which, when traversed by the sun, marks the beginning and the end of Shabbat. See infra, note 13. R. David Spira, Teshuvot Bnei Ẓion, III, Kuntres Midat ha-Yom, sec. 21, states that, during the polar winter, days are demarcated by the circuit of the stars in the overhead sky. Teshuvot Divrei Yaẓiv, Oraḥ Ḥayyim, no. 108, sec. 11, suggests that the day’s beginning and end should be regarded as congruent with the beginning and end of the day in the Land of Israel. Cf., infra, note 15.
R. Yechiel Michal Gold, Me’asef le-Khol ha-Maḥanot, Oraḥ Ḥayyim 18:25, finds what he terms “clear evidence” for the underlying assumption that the “day” may be defined in terms of the revolution of celestial bodies rather than by the appearance of the sun in the comments of Rabbenu Baḥya, Genesis 1:13. Rabbenu Baḥya questions the cogency of the verse that declares “and it was evening, and it was morning” with reference to the first three days of creation, i.e., before the creation of the sun. Rabbenu Baḥya explains that the reference is not to “the light” but to “the sphere in which it revolves for, with regard to every portion of the sky, when it ascends that is its morning and when it sinks [below the horizon] that is its evening.” See also Ramban, Commentary on the Bible, Genesis 1:5. However, although Rabbenu Baḥya’s comments may provide support for the notion that demarcation of successive days may be determined on the basis of the rising and setting of celestial bodies other than the sun, those comments have no bearing upon the question of whether completion of a 360 degree rotation in the overhead sky has a similar import. See, however, R. Eliezer Ashkenazi, Ma‘asei ha-Shem (Venice, 5343), Genesis 1:5, who asserts that the first day of creation was determined by circuitous movement of the heavens whose return to the point of creation marked the completion of a day. Ma‘asei ha-Shem expressly applies that concept to the polar area in declaring, “There is no doubt that even one [for whom] the pole is above his head is obligated to observe Shabbat on the seventh circuit even though there was no darkness there at all.” 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.¹³In a note appended to Mo‘adim u-Zemanim, II, no. 155, R. Moshe Sternbuch opines that “the day changes at precisely the moment that the sun reaches its most distant point and begins to draw closer.” The “most distant point” to which Mo‘adim u-Zemanim refers is presumably the point most distant in the sky from the point at which the sun makes its first appearance at the beginning of the polar spring. Mo‘adim u-Zemanim declares that “night” in such areas is no more than a split second in duration. See also Teshuvot ve-Hanhagot, I, no. 315. See as well Me’assef le-Khol ha-Mahanot, Oraḥ Ḥayyim 18:25, s.v. ve-hineh mah she-katav mori, who also states that the Sabbath must be observed only for the amount of time that it takes the sun to complete a single circuit.
It may be noted that at the North Pole the sun neither rises nor declines in the course of its daily circuit. Rather, the sun is observed as circling the horizon once each day in a constant orbit that is a bit higher over the horizon each day until it reaches a height of approximately 23.5° at the time of the summer solstice. However, as one proceeds some distance south of the Pole, the sun, although it does not descend below the horizon during that period, may nevertheless be observed during the course of its daily circuitous movement above the horizon. In those areas—and only in those areas—it might be contended that day and night begin and end when the sun is at its lowest point above the horizon. See R. Eliyahu Baruch Kepetsch, Koveẓ Bet Aharon ve-Yisra’el, Tishri-Ḥeshvan, 5757, p. 150 and cf., R. David Heber, “When Does One Pray When There Is No Day?” Kashrus Kurrents, Autumn, 2002, pp. 17f.
Adopting a somewhat different position, R. Jehoseph Schwartz, Teshuvot Divrei Yosef (Jerusalem, 5622), no. 8 and idem, Divrei Yosef, Tevu’ot Shemesh (Jerusalem, 5603), Derekh Mevo ha-Shemesh, p. 61b, states that the point in the sky occupied by the sun at its first appearance in the polar region in the spring represents the beginning of each “day” and the point at which the sun is last seen before it sets in the fall represents the beginning of each “night.” Accordingly, “day” and “night” commence when the sun reaches those points in the sky during the course of each twenty-four hour circuit. Divrei Yosef, p. 62a, asserts that during the winter months a similar determination is made on the basis of the position of the “two stars of the Little Bear, [which are in the] vicinity of the star of the Pole (the North Star),” i.e., the position of their first sighting in the fall marks the beginning of the “night,” and “day” begins when those stars have moved 180 degrees across the sky.
Divrei Yosef’s description of the astronomical phenomena during the polar winter is both imprecise and inadequate as a basis for resolution of the problem. Pherkad, a third magnitude star, and Kochab, a second magnitude star, are known as the “Guardians of the Pole” because they circle Polaris (the North Star). All three stars are part of Ursa Minor (the Little Bear). The first two stars of Ursa Minor to become visible are Kochab and Polaris (the North Star). Both are second magnitude stars. However, the first celestial bodies to become visible are the planets Venus and Jupiter. Those planets do not become clearly visible until close to the end of civil twilight, i.e., when the sun drops six degrees below the horizon. At the North Pole civil twilight does not end until October 8. The first star to become visible north of the celestial equator is the zero magnitude star Arcturus in the constellation Bootes and is followed closely by the slightly smaller star Vega in Lyra and then by Capella in Auriga. However, even the largest star is not visible to the naked eye until the sun has declined approximately nine degrees below the horizon. At the North Pole, the sun disappears a little after the time of the autumn equinox but does not reach a declension of nine degrees until October 16, a little more than three weeks later. During that intervening period neither the sun nor any star is visible. The same is true during the period immediately prior to the spring equinox when the sun is not visible but is less than nine degrees below the horizon. Thus, for more than six weeks each year neither the sun nor any star is visible. During those periods, days cannot be demarcated by means of the circular rotation of stars in the overhead sky. Even if Venus and Jupiter are used for this purpose, there are four weeks in the year during the polar twilight in which those planets are not visible. I am indebted to Mr. Joe Rao of the Hayden Planetarium for making this information available to me.

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.²⁶Cf., however, the discussion of the import of the narrative recorded in the Palestinian Talmud infra, note 27, as well as notes 32-33 and accompanying text.

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.²⁷The Gemara, Shabbat 118b, speaks of commencing observance of Shabbat at an early hour in Tiberias and concluding its observance at a later hour in Sepphoris, i.e., observing Shabbat for longer than a twenty-four hour period. The principle that both the beginning and end of Shabbat is determined by local criteria would yield the result that a person traveling from Sepphoris to Tiberias would observe Shabbat for less than twenty-four hours.
R. Chaim Avraham Gatinyo, Tirat Kesef (Salonica, 5496), p. 5b, endeavors to demonstrate that Shabbat must be observed for a minimum period of twenty-four hours on the basis of the narrative recorded by the Palestinian Talmud, Kelayim 9:3 and Ketubot 12:3. R. Judah the Prince died on a Friday. The sun did not set that evening until much later than its usual time and hence observance of the Shabbat did not begin until that late hour. That miraculous phenomenon occurred in order that every participant in the funeral, including those who had traveled from other cities, might have sufficient time to return home and “prepare a barrel of water and kindle the lamp” before the advent of the Sabbath. Shortly after the sun finally set, the crowing of the rooster was heard. Experiencing daybreak so quickly after nightfall, people realized that they would not be observing a full twenty-four hour period as Shabbat. The populace feared “lest they had desecrated the Sabbath” during the period of time that the sun’s movement was arrested. Thereupon, a heavenly voice proclaimed that all those who had participated in the funeral of R. Judah were assured a portion in the world to come. Excluded from that promise was one individual, a laundryman who had not participated in the funeral. Shitah Mekubbeẓet, Ketubot 103b, cites a certain Rabbenu Kalonymus who explains that the populace had actually transgressed Shabbat prohibitions because the Shabbat had indeed begun at its proper time but people inadvertently failed to commence observance of the Shabbat in a timely manner because the sun was still high in the sky. Nevertheless, they were forgiven because of their participation in R. Judah’s funeral. The laundryman also failed to begin his observance of the Sabbath at the proper time for the same reason but because he was remiss in not participating in the funeral he was not forgiven. The laundryman was forgiven only subsequently when, out of great anguish, he hurled himself from a roof and died.
Rav Pe‘alim, II, Sod Yesharim, no. 4, disputes Tirat Kesef’s understanding of this narrative. Rav Pe‘alim asserts that there is no evidence that the Shabbat that occurred on the morrow of R. Judah’s death was less than twenty-four hours in duration. At first, people were confused, contends Rav Pe‘alim, because of the premature crowing of the rooster. The rooster’s circadian clock, he asserts, was attuned to a twenty-four hour cycle. Moreover, contends Rav Pe‘alim, there is no indication that the populace acted in an inappropriate manner (indeed, the heavenly voice may be construed as having endorsed their behavior) but only that they were afraid lest they had acted incorrectly. [Rabbi Tucatzinsky, Bein ha-Shemashot, p. 55, suggests that the populace acted correctly because the sun had not set. However, people were confused because they feared that the sun had indeed set and the illumination they perceived emanated from a supernatural source. Cf., infra, note 34.] Furthermore, argues Rav Pe‘alim, the Sabbath is to be observed on the seventh day “in all your habitations” (Leviticus 23:3), i.e., the occurrence of Shabbat is determined both at the beginning and end of the day by the setting of the sun in the locale in which a person finds himself, regardless of the length of the intervening day. R. Ephraim Zalman Margolies, Teshuvot Bet Efrayim, Yoreh De‘ah, no. 76, similarly disagrees with Rabbenu Kalonymus in asserting that Shabbat is determined solely by the setting of the sun.
Rav Pe‘alim further remarks that, having properly ushered in the Sabbath at sunset, it would be ludicrous to observe Shabbat for a portion of the following day in order to achieve a complement of a full twenty-four hours. See also R. Elijah Isaac Shemesh, Yedei Eliyahu (Jerusalem, 5790), no. 44. Thus, Rav Pe‘alim declares that a person who is able to travel long distances on Shabbat by employing a Divine Name or in some other miraculous manner may cease his observance of Shabbat immediately at nightfall in his new locale even though he has observed Shabbat for much less than twenty-four hours. That is also the position of a host of other authorities including R. Yechiel Michal Tucatzinsky, Bein ha-Shemashot, p. 55; Teshuvot Minḥat Elazar, IV, no. 42; Teshuvot Bnei Ẓion, III, Kuntres Midat ha-Yom, secs. 23-24; R. Alter Saul Pfeffer, Teshuvot Avnei Zikaron, II, no. 87, sec. 2; and R. Ben-Zion Abba Sha’ul, Or leẒion, I, Oraḥ Ḥayyim, no. 14. Cf., however, infra, note 60, as well as notes 65-66 and accompanying text. 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.

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.⁴²Cf., however R. Aryeh Leib Lipman, Or ha-Yom (Vilna, 5661), sec. 44, who cites sources indicating that sunrise is determined by the first appearance of the sun as observed from the top of any proximate mountain rather than by its visibility at ground level. Thus, Or ha-Yom’s position is that there is a possibility that sunset is determined for an entire area on the basis of the disappearance of the sun below the horizon when observed from the top of the highest mountain or structure within visual distance. This was also the view of R. Joshua Leib Diskin as recorded by R. Hiya David Spitzer in the latter’s Nivreshet le-Neẓ ha-Ḥammah be-Ẓion (Jerusalem, 5658), I, p. 59b. In the introduction to his Nivreshet le-Neẓ ha-Ḥammah be-Ẓion, Rabbi Spitzer records his efforts to determine the time of sunrise for the city of Jerusalem on the basis of the sun’s appearance at the top of the Mount of Olives. Or ha-Yom then expresses doubt with regard to whether that principle is applicable only to determination of sunrise, which has halakhic significance primarily in the determination of the time of arousal from sleep (sha‘at kimah) for purposes of recitation of the Shema, or if it applies as well to determination of sunset which has calendrical significance. A distinction of that nature is developed at some length by R. Aaron Fried in his commentary on the Mishnah, Ḥalat Aharon (Munkàcz, 5653), Berakhot 1:1, sec. 3. Cf., Teshuvot Minḥat Elazar, I, no. 69. In sec. 55, Or ha-Yom asserts that, if the time of sunset for the entire area is determined from the vantage point of the mountain top, only mountains within visual distance of a person standing at ground level need be considered. See also Nivreshet le-Neẓ ha-Ḥammah, pp. 5a and 58b-59b. Or ha-Yom further asserts that, although the height of a tower planted in the ground may similarly be taken into account, sunset is in no way contingent upon visibility of the sun to a bird flying in the sky. Assuredly, Or ha-Yom would likewise ignore the sun’s visibility as observed from an airplane.
R. Moshe Sternbuch, Mo‘adim u-Zemanim, II, no. 155, cites the comment of Rashi, Shabbat 118b, that speaks of the sun being “covered” or hidden in Tiberias because of its location in a valley and notes the implication that the inhabitants of Tiberias commenced observance of Shabbat earlier than was actually necessary. Accordingly, he advances a position similar to that of Or ha-Yom in asserting that, in a locale in which there is a mountain of medium height in relatively close proximity, sunset for the entire area is determined by observation at the top of the mountain. Cf., however, supra, note 41. See also the comments of R. Shneur Zalman of Liady in the section of his Siddur titled Seder Hakhnasat Shabbat, reprinted in Shulḥan Arukh ha-Rav (Brooklyn, 5724), II, 414, which lend themselves to a similar interpretation. At the same time, Rabbi Sternbuch cites and dismisses the suggestion of Or ha-Yom to the effect that, if there is a skyscraper in the city, sunset may perhaps be determined by observation at the top of the building.
Assuming that sunset is determined at ground level, it nevertheless seems logical to conclude that, if there are mountains on the west which hide the sun before it sinks below the horizon, that phenomenon would be ignored since, were the mountains not hiding the sun, the sun would be visible at ground level. Indeed, if one were to circle the mountain, the sun would remain clearly visible at ground level on all sides of the mountain. Nevertheless, Rabbi Sternbuch, loc. cit., cites R. Joshua Leib Diskin, as recorded in Nivreshet le-Neẓ ha-Ḥammah, as maintaining that sunset is determined by the disappearance of the sun even if such disappearance is due to the interposition of a mountain. Actually, Nivreshet le-Neẓ ha-Ḥammah, p. 59b, reports that Rabbi Diskin declined to rule with regard to the question of sunset as it affects observance of Shabbat. Curiously and inexplicably, Rabbi Sternbuch declares that R. Joshua Leib Diskin’s view should be heeded if the mountain to the west is only of moderate height but at the same time asserts that sunset in the entire area is determined by observation at the top of a mountain of moderate height located to the east. That position reflects an inconsistency since, if sunset is determined by observation at the top of the mountain, there should be no difference between situations in which the mountain is located in the east and situations in which the mountain is located in the west. A mountain on the west hides the sun only from someone standing at the base of the mountain; the sun is not at all hidden when observed from the peak of the mountain located in the west.

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).⁶⁶That argument is certainly not compelling. A person may receive nutrients intravenously even though he will not suffer the “affliction” of the fast. See this writer’s Contemporary Halakhic Problems, III (New York, 1989), 129–140. See also Ḥavalim be-Ne‘imim, IV, no. 3, who comments, “Is it then forbidden to sleep on Yom Kippur even though [when sleeping] one experiences no afflictions?” Ḥavalim be-Ne‘imim dismisses the notion that one must observe Shabbat and Yom Kippur for a full twenty-four hour period as entirely without basis. See also supra, note 27. 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.⁶⁸Cf., R. Menachem Kasher, Teshuvot Divrei Menaḥem (Jerusalem, 5737), I, no. 3. In Teshuvot Divrei Menaḥem, Rabbi Kasher advances an apparently contradictory position in suggesting that it is forbidden to cross the dateline in a manner that curtails Sabbath observance because the traveler thereby actively abrogates a positive commandment by removing himself from its ambit. That statement is surely in contradiction to his parallel assertion that the traveler remains bound by Sabbath obligations. Cf. also, supra, note 51.