This is not meant to be a "Purim Torah" question.

The concept of Rosh Hodesh is based on the orbit of the moon around Earth. But, with the proposal of sending people to live permanently on Mars, I assume that it won't be long before they have people live permanently on the moon.

So, if someone did live permanently on the moon. Things are relative. From that person's viewpoint, Earth looks like the moon's "moon". So, it would like Earth has a "molad". Would you have to observe Rosh Hodesh at the same time and in the same manner as if you would living on Earth?

Similarly, I guess you would call it "Kiddush Ha'Aretz" (or "Adamah?") - would you have to recite that each month?


1 Answer 1


One consideration raised by R. M. Kasher is whether one s obligated in commandments on the moon or in outer space at all given the Torah expression “all the days which you are alive on this earth” (Deut. 12:1) in the context of mitzvos. Apparently he concluded that one is obligated see here (which cites this from JD Bleich, “Contemporary Halachic Problems”, vol.1.) and here (which cites this from the 5730 issue of No'am)

Rabbi Benzion Firrer, however does hold that one is exempt from all commandments while in space (cited there and here citing the 5730 issue of No'am).

In regards to kiddush Levana in particular Rav Kasher writes that one loses performing the mitzvah of Kiddush Levana on the moon. quoted here from "Man on the Moon" by Ha-Rav Menachem Kasher (pp. 51-55). This is also the view of R. M. Schneerson quoted here (citing Rozen, Yitzchak Yehuda, 1999, "The Torah in The Space Age" Proceedings of the Associations of Orthodox Jewish Scientists, 2:175-179)

In regards to time bound mitzvos in general Rabbi Menahem Kasher ruled that “The situation on the moon [or Mars] is equivalent to the north and south poles; therefore posit a 24-hour day, with alternating periods of 12 hours day and 12 hours night regardless of the presence or absence of light from the sun”. quoted here.

  • I'm not downvoting, because you are only citing a second hand source, but p51-55 are just his discussion of keeping Mitzvot/Shabbat in general. I don't see any reference to Kiddush Levana there.
    – Double AA
    Commented Feb 19, 2015 at 15:45
  • @DoubleAA If you find the correct pages then please edit it in.
    – mevaqesh
    Commented Feb 19, 2015 at 15:47
  • Thanks. You also addressed the general question about living on other planets, though many of them have their own moons. I may raise this as another question, actually.
    – DanF
    Commented Feb 19, 2015 at 15:57

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