This M.Y. answer says that there are differing views as to whether someone is exempt from mitzvoth while in space.

If we were to follow the opinion that one is obligated, should a person on Jupiter be saying Kiddush Levana for each of its 62 known moons ? What if more than one moon is visible?

Or, is Kiddush Levana only done regarding Earth's moon? Does it need to be visible to the naked eye, or what if one on Jupiter viewed Earth's moon in a telescope or it just appears as a "star"?

My question would apply to any planet that had multiple moons.

  • Similar: judaism.stackexchange.com/q/55267
    – msh210
    Commented Dec 1, 2015 at 23:18
  • Many rabbis believe it's not permitted to leave earth because of the hundreds of complications regarding mitzvot and the verse in the Torah that says "Fill the land and conquer it." Not being able to do Kiddush Levana would be just one of many problems. See these two answers: judaism.stackexchange.com/a/65015/11052
    – Gabriel12
    Commented Dec 1, 2015 at 23:58
  • @Gabe12 How is not doing Kiddush Levana a problem? If you aren't obligated because you didn't see the (Earth's) moon, then you're not missing anything. No problem.
    – Double AA
    Commented Dec 2, 2015 at 0:02
  • @DoubleAA You are right, I didn't choose the right words. What I mean is that many mitzvot just can't be performed outside earth. I believe you wouldn't do Kaddish Levana.
    – Gabriel12
    Commented Dec 2, 2015 at 0:05
  • @Gabe12 Right, but why is that a problem? If there is no Mitzva, then I didn't not do something.
    – Double AA
    Commented Dec 2, 2015 at 0:15

2 Answers 2


It says in the Shulchan Aruch:

ברכת הלבנה וזמנה ובו ד סעיפים: הרואה לבנה בחדושה מברך אשר במאמרו ברא שחקים וברוח פיו כל צבאם חוק וזמן נתן להם שלא ישנו את תפקידם וכו': הגה ואין לקדש החדש אלא בלילה בעת שהלבנה זורחת ונהנין מאורה (אגור): rough translation: "One who sees the moon in its renewed state makes the blessing, "who has, with his word, created skies and with the breath of his mouth all of their hosts, a decree and a time he gave in them that they shouldn't change their cycles...". (note: and one should only sanctify the moon at night at a time that the moon shines and its radiance is visible"

It's a clear law that one has to see the moon in its renewed state, the moons of another planet are not "the moon", the moon and the sun are called in Bereishes "the two great luminaries" , they are totally different than other stars and moons in every way.. but besides for that, the mitzvah of Birchas Halvanah doesn't apply to other moons, jus ttake a look at Halachapedia note 1:

Why did Chazal choose to make this Bracha on the moon specifically? Aruch HaShulchan 426:2 explains that since the moon is the closest to Earth we are able to recognize Hashem’s control over nature easily. Also, the moon is compared to Bnei Yisrael; just as the moon doesn’t have any of its own light, so too Bnei Yisrael are only sustained through Hashem and his Torah; just as the moon gets smaller and bigger, so too Bnei Yisrael are always renewed.

As seen through Rambam hilchos Kiddush HaChodesh, the "molad" is calculated is based on the sighting of the new moon, which only exists on Earth, and which kiddush halvanah is based on.

There are many other proofs I can bring, but I think this get s the general idea across. Mitvos don't apply in space to things in space, meaning even if you;'re obligated in mitzvos like davening 3 times a day in space, but that's just following your own time you left from etc.... The moons of Jupiter and not at all the same as our moon. There's nothing anywhere in the Torah about making Kiddush "Halvanah" on something other than "the moon" itself. If anyone can find something suggesting otherwise, I'd be happy to see it :)


also just to be totally clear, just look in the yehi ratzon of kiddush levana:

"Let it be your will.. to fill the deprecation in THE moon, so that there shouldn't be in it any detraction, and the light of the moon will be like the light of the sun, like the light of the seven days of the Beginning, like it was BEFORE it's subtraction / lessening (Meeut), like it says, "And Elokim made the TWO great luminaries", and fulfill in us the verse that says, "and you should search Hashem, your G-d, and David their King, Amen",

and King David is compared to THE moon in many places, I can quote those too, because the moon and king David is malchus of Atzilus, specifically OUR moon refers to malchus of Atzilus, not any other moon the universe.

  • The entire basis of this question seems to be that only our moon is called “the moon.” You have yet to back that up. Certainly our moon is “a moon,” but to the exclusion of all others? Maybe we make Kiddush Levanah on the moon closest to Earth because we’re on Earth, but were we on a different planet we’d make it on its moon.
    – DonielF
    Commented Mar 24, 2019 at 14:57
  • 1
    @DonielF The word "levanah" -white -- refers to only this one moon, because it says in Bereishis "He created the two great lumaries" -- the sun and the moon. The moon is different than all other moons, its one of the two great luminaries -- just like the sun is greater than all other stars, the whole idea of kiddush levanah is to fill the void of the moon "pigeeas halvanah" Which was made only to our moon Commented Mar 25, 2019 at 23:16
  • Two great luminaries from our perspective on Earth. Pretty much every moon have a פגיעה, waxing and waning.
    – DonielF
    Commented Mar 25, 2019 at 23:18
  • @DonielF No its specifically the two great luminaries in the entire universe the pgia of our moon is different than all others, OUR moon, and OUR sun is different than all other sun and stars, that's why the torah mentiones them seperately than all other stars, the "pgia" of other stars is just waxing and waning, but our moon was origianlly the same size an dbirghtness of the sun, it was shrunken down and currently accepts its light from he sun, but during kiddush levana we are praying that he should make the moon the same as the sun in size and brightness in moshiach times, look at the text Commented Mar 25, 2019 at 23:28
  • 1
    I think this is a great answer and should be accepted. I think you've made a really good case.
    – Rabbi Kaii
    Commented Dec 5, 2022 at 10:43

"שהם עתידים להתחדש כמותה". Presumably we are not "עתידים להתחדש" like the moons of Jupiter.

The basis of kiddush le'vanah would seem to be haviu alai kaparah al shemiateti es ha'yareach, there is no proof that the moons of Jupiter were ever a different size or that if they were this would require a kaparah.

Furthermore the inyan of kiddush le'vanah seems to be shemirah from our enemies in our diminished state, keshem she'ani roked.. We do not have any oyvim on Jupiter as far as I know.

  • Several requests - you have transliterated many terms, which, even with my good Hebrew and memory, I have some trouble deciphering some items - moreso a problem for many of our other readers. You'd do better tarnslating as much as possible into English. Secondly - please list some sources to support where you are getting these ideas. As it stands, these sound like your own interpretation. SInce you don't cite any sources, I am skeptical accepting some of these ideas as support. You also don't answer my question, in any way which is do we or do we not?
    – DanF
    Commented Dec 2, 2015 at 2:24
  • "there is no proof that the moons of Jupiter were ever a different size". We also have no direct proof that our moon was a different size. The concept is based on Midrash. Not that it invalidates the theory, but, in terms of tying a mitzvah (which you seem to be doing, here - another question, I have) to a Midrash - I don't know if that wouldbe valid, here.
    – DanF
    Commented Dec 2, 2015 at 2:27
  • @DanF Yes w edo actually it says so in the Torah, thats the best proof you can have, its in Rashi and even an explciit verse and undisputed by all commentaries Commented Mar 26, 2019 at 1:54

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