Charlotte woke up at 5:45am SMT (Standard Martian Time). She put on her kippah, and her tallit. She carefully opened her siddur, her prayerbook, entitled Sha’arei HaShamayyim, “The Gates of the Heavens.” She was ready by 6:00am SMT (Standard Martian Time) to daven Shacharit, conduct morning prayers. As a Martian rabbi, she will spend the day preparing her d’var Torah, her sermon, to deliver that evening for Shabbat services at Kehillat Beth Shalom Ma’dim, “Congregation House of Peace of Mars.”

This potential scenario is what drove me to write my thesis, entitled “Eyes on the Horizon: Theological and Halakhic Challenges for the First Jewish Settlers on the Moon, Mars, and Beyond.” As I sat in class at Hebrew Union College – Jewish Institute of Religion, I was struck with a question: How would future Jews, living off-planet, live Jewishly? I wondered because, except for a Jew who briefly appears in the show “Firefly,” Jews are rarely depicted in any futuristic scenario.

Working with Rabbi Mark Washofsky, Ph. D., I am envisioning a time when humanity may find a new home off-planet. Currently, Elon Musk plans to build a million-person colony on Mars , and NASA and Russia are teaming up for a permanent Lunar base . This futuristic scenario is not actually as far off as some may think; after all, Space X’s Falcon Heavy just put a Tesla into space. I believe all streams of Judaism need to begin the conversation to allow Judaism to flourish off-planet.

Many rabbis throughout millennia yearned to understand the true nature of the cosmos, utilizing the best known natural philosophy of their age. For example, the rabbis surmise in the Talmud that the cosmos is made up of eighteen thousand worlds . Later, Rabbi Yehudah ben Barzillai of Barcelona (c. 11th Century CE) believed the universe was comprised of 1018 worlds, or a billion billion worlds . Rabbi Barzillai’s logic approximates NASA’s most recent calculation that the universe may contain two trillion galaxies . Rabbi Hasdai Crescas Cf. Rabbi Hasdai Crescas, Or HaShem, ed. Rabbi S. Fisher, Itri Edition (Jerusalem, 1990), 64-67 and 83–84 (c. 14th Century) even postulated that the universe is infinitely large and there are infinite universes, prefiguring echoing the modern multiverse theory.

Our more recent discoveries open new questions about what counts as the realm of humans, and what counts as the realm of God. Is there a theological issue crossing from humanity’s realm into the divine realm? I believe that any celestial body to which humans can venture must not be considered the realm of God. God must lie beyond that.

The laws handed down throughout Judaism’s history by rabbis, instructing Jews how to live Jewishly according to the Bible, are referred to as halakha. What challenges will emerge in halakhically creating Jewish time and an off-planet Jewish calendar? The Terran Hebrew calendar has always depended on the visible celestial objects in the sky, resulting in the Lunar calendar. What would happen when there are no such celestial objects? And can halakhah itself can exist off-planet? There seems to be a halakhic consensus that the Earth is central to halakhic time and space. One could even say there is a halakhic bubble around the Earth. Once one crosses the threshold, into the heavens, one is possibly beyond the realm of halakhah. This is because most halakhah is dependent on the 24-hour day and Terran seasons.

So here is one challenging scenario: Let’s say halakhah suggests Lunar or Martian Jews were to follow the time at the Terran spot from which they departed. Their time on the Moon or on Mars would almost certainly not match up with Terran time . If on Mars, for instance, Martian society decides to make its day 24 hours and 39 minutes, to match a Martian “sol”, and Martian Jews were compelled to follow Terran time, their Jewish schedules would slowly slip throughout the day. Eventually, Jews would be davening Shacharit in the middle of the night. On top of that, seasons on Mars do not match Terran seasons, which may become irrelevant to Martian societies anyway. With Jewish holidays such as Passover, Shavuot and Sukkot tied down to agricultural seasons, halakhic authorities would need to adapt the Jewish calendar to off-planet settlement.

Or here’s another issue: in the Talmud , a question arises as to what a Jew must do if they are lost in the desert and do not know when Shabbat will be. The halakhic answer is that they must count six periods of 24 hours, then mark the seventh as Shabbat. That day will be their Shabbat; however, they must treat every other day as if it might be Shabbat, since they would not know the true Shabbat. The lost traveler cannot do work of any kind that would desecrate Shabbat, except for work to preserve their life and to help get back to society. According to this halakhah, Exo-Jews would constantly live as the lost traveler. They would each need to calculate their own Shabbat and they would be forbidden from ever doing work which might desecrate Shabbat. Obviously, this potential scenario is impractical and needs to be halakhically resolved.

All of these challenges — and many others — should be handled sooner rather than later, and I hope all Jews from all streams of Judaism will be part of the conversation. I fear if the conversation about living Jewishly among the stars waits until it is absolutely necessary, it will be dominated only by Jews for which halakhah is absolutely necessary. Exo-Judaism could revitalize the Jewish people by offering an opportunity for interdenominational dialogue and collaboration. If we do so, then Judaism would live beyond even humanity’s time on Earth and thrive as we become a multi-planet species.

Read Adam’s full thesis here.