For it is not in Heaven…or is it?: On the Halakhot and Hashkafot of Space Travel


On the twentieth of July 1969, after four days of travel, two men set foot on the moon for the first time in history. Hundreds of millions heard Commander Neil Armstrong’s famous words “…one small step for a man, one giant leap for mankind” as he traversed the final frontier.[i] The Apollo 11 landing inspired wonder and awe; it represented a landmark in the advancement of science and the development of human ingenuity. However, there was a minority for which the lunar landing instilled doubt and confusion.[ii] What did this advancement mean for God-fearing Jews? The new terrain that became available to man came along with a new set of questions in Jewish observance; with so many commandments associated with time and how the Earth revolves around the sun, how can Torah be kept in such an environment? If not living on the surface of the earth, is a Jew even obligated in Torah and mitsvot? What is the nature of time and of the practice of Torah and mitsvot? The advent of the lunar landing brought challenging questions like these to the fore, and over the years, several scholars have provided insights into this perplexing situation.

The first time space travel for a Jew became a practical issue in halakhah was in 2003, when the Jewish Israeli astronaut Ilan Ramon asked Rabbi Tzvi Konikov of Chabad of Cape Canaveral how he should keep Shabbat on his space mission.[iii] The main concerns in question were whether one must be on earth in order to be obligated in mitsvot and if not, when should one keep the mitsvot associated with the measurement of time?

Rabbi Menachem Mendel Kasher, in his book that addresses the theological and legal implications involved when the moon was first being explored, Man on the Moon,[iv] asserts that the obligation in Torah and mitsvot in general is considered a hovat gavra; it is an obligation that rests on every Jew, despite his or her location, be it the moon, the polar regions, or the depths of the ocean. Rabbi Kasher continues that so long as a person is alive, there is no time in which a person is absolved from Torah and mitsvot or in which he may transgress a prohibition.[v]

There are several opinions regarding the issue of how to approach mitsvot associated with time, including Shabbat, festivals, regular times of prayer, and so forth. Rav Levi Yitzchak Halperin, in response to Rabbi Konikov’s question on Ramon’s behalf, discusses three options as how to measure time in a space vessel. The first is that one day is counted each time the shuttle orbits the globe. This is explained by the verse in Genesis 1:5, “It was evening and it was morning, one day,” meaning that one full day is counted by a period of nighttime and then a period of daytime. This, however, is impractical, because if a shuttle orbits the Earth once every ninety-minute period, one twenty-four-hour period would include sixteen “days,” an obligation of thirty-two recitations of Shema, forty-eight prayers, and two Shabbatot, observed for an hour and a half each.[vi] Rav Halperin then offers a second proposal: a space traveler should act in accordance with the time zone over which he is traveling. This also includes several impracticalities, for in one moment, the traveler could be observing Shabbat, but moments later, Shabbat would be over in a different region; or one moment he could be reciting Shema, but within a few moments, the individual may find himself in a time-zone in which there is no longer such an obligation. Rav Halperin considers a final, third proposal in that the space traveler would establish his own measurement of days, based on the twenty-four-hour period that the individual experiences on the space shuttle, regardless of the events happening on planet Earth. The first twelve hours that the astronaut experiences would be night, then the next twelve would be day, and the rules and prohibitions regarding time would be observed accordingly. This approach is flawed in that it does not follow all the biblical requisites of the measurement of time. The concept of time in relation to mitsvot is first mentioned in Genesis 1:14-19, in which God creates the luminaries to generate light and to distinguish between day and night, seasons, and years. Rashi explains that the mention of seasons indicates that the phases of the moon, as viewed from Earth, will allow the Jewish people to distinguish when to celebrate festivals. The mention of days describes the need for the moon in one half of the day and the sun in the other, and that years refers to 365 days each marked by the rising and setting of the sun and moon. Rav Halperin concludes that mitsvot that are related to time must be done according to halakhic counting which is measured based on the paths of the earth, sun, and moon and the relationship between them. A human being on a space shuttle operates on a time that is independent of this system of rules built on nature or the order of creation. Therefore, one travelling in space would not be obligated in the mitsvot that are dependent upon time, because these mitsvot only apply to those living in a place that follows the natural laws of creation, not a completely different time system.[vii]

To understand this topic more in depth, the situation of a Jew travelling in space can be likened to that of a Jew residing in a polar region, where the sun may not rise or set for several months at a time. This situation is similar to space travel because of the question of how to measure time. Both Rav Yaakov Emden and Tiferet Yisrael compare such a situation to the one in the Gemara in Shabbat 69b in which a person is lost in the desert without any knowledge of which day of the week it is. There the Gemara discusses when the lost individual should keep Shabbat. The Gemara deliberates whether one would start counting six days from when the individual was lost and rest on the seventh, like the way Hashem created the universe and then rested; keep Shabbat on the first day and then count six days until the next, like the first man, Adam, who was created shortly before the first Shabbat; or treat every day as if it was Shabbat, except for the allowance of the usually-prohibited activities one needs to do in order to preserve life.

In regard to residing in polar regions, Rav Yaakov Emden follows the first sequence listed in the aforementioned Gemara in which, upon arrival, one would count six days and then keep Shabbat. Tiferet Yisrael is of the opinion that one would continue counting the days of the week as he or she did when in a more conventional area and observe Shabbat times in accordance to where he or she originated. If doubt regarding the specific beginning and ending times of Shabbat causes transgression, such transgressions would be rabbinic, because the situation is similar to that of one lost in the desert. Tiferet Yisrael continues—even though in polar regions there is no clear sunrise and sunset, unlike one travelling in space, one is still able to observe the rotation of the sky and mark a clear difference between two days.[viii]

Despite the amount of research that was involved in the details of how a Jew can travel in space and the polar regions, the question remains as to whether a Jew should travel in such places. Zekher Simcha expounds on that topic based on a comment of the Gemara, Berakhot 31a:

What is meant by the verse ‘Through a land that no man had passed through and where no man dwelt’ (Jeremiah 2:6)? Since no one passed through, how could anyone dwell? It is to teach you that any land which Adam decreed should be inhabited is inhabited and any land which Adam decreed should not be inhabited is not inhabited.

Zekher Simcha considers this a statement that carries halakhic ramifications: “Adam decreed that only areas in which mitsvot might be observed should be inhabited; he decreed that areas in which mitsvot are not fully binding should remain desolate and uninhabited.”[ix] This highlights an important hashkafic point: A Jew should actively seek opportunities to fulfill mitsvot, but that is simply not possible in outer space, where time-bound mitsvot are irrelevant. Though it may not be an actual transgression to remove oneself from the ability to perform mitsvot, doing so is not within the spirit of the Jewish practice. Furthermore, Deuteronomy 11:21 reads that God commanded mitsvot “so that your days will be prolonged upon the land which the Lord your God gave you.” This does not mean long life, but long “days.” It is possible for a man to live a prolonged life even if his “days” are not; though one may conceivably live on the moon to an advanced age, for a Jew, that is not an ideal existence, nor is it the blessing that God seeks to give. God’s blessing is “that your days be prolonged”; to be enjoyed and filled with time-bound mitsvot, for which the concept of a regular halakhic day is a prerequisite.[x]

Ilan Ramon embodied what it meant to express the spirit of Jewish practice. Though he indicated to one reporter that he did not regularly observe Shabbat and, in the end, he was not able to fully observe Shabbat once he was aboard the shuttle, he still recognized that by being involved in such a monumental space program, he was representing all Jews in the public eye and was motivated to act accordingly. Though space travel invariably made it more difficult to observe mitsvot, he nevertheless publicized the importance of observing Shabbat by consulting rabbinic authority on the matter and by going out of his way to include Jewish practice as much as possible. A Jew may not necessarily be well versed and consistent in the practice of Judaism, but can still have an innate aversion to unnecessary public desecration. With the eyes of the world on him, Ramon was immortalized as a Kiddush Hashem, one who publicly glorifies God, not because he shirked off the time related responsibilities that that are incumbent upon the Jewish nation, but because of his attachment to them.[xi] Though the new avenue of exploration that is outer space is available to humanity and the future holds unlimited possibilities within it, the Jewish nation must tread this area with caution. Jews may be an astronauts and explorers, but we are first and foremost Jews, and we are meant to actively seek out opportunities to do what is right, from the depths of the ocean to the heights of the heavens.

Judy Leserman is a first year student at Stern College for Women, after having spent two years at Darchei Binah Seminary.

Chaya Apfel is a second year student studying Psychology at Stern College for Women.


[i] Dunbar, Brian. “July 20, 1969: One Giant Leap For Mankind,” NASA, 14 July 2014 available at

[ii] Kasher, Menachem Mendel. “Introduction to Man on the Moon” (Hebrew), available at

[iii] “Shabbat in Outer Space Astronaut Ilan Ramon’s Question: ‘When Should I Observe Shabbat on the Columbia?’”, available at

[iv] “Menachem Mendel Kasher” Wikipedia, available at:

[v] “Shabbat in Outer Space Astronaut Ilan Ramon’s Question: ‘When Should I Observe Shabbat on the Columbia?’”

[vi] ibid.

[vii] ibid.

[viii] ibid.

[ix] Bleich, J. David, “Mitsvot in the Polar Regions and in Earth Orbit,” in Bleich J. David,  Contemporary Halakhic Problems. Vol. 5 (Southfield: Targum, 2005), 75-128.

[x] ibid.

[xi] ibid.