Einstein's equation E=mc2, predicted that the sun will burn out of fuel (hydrogen) which it converts to helium and produces light and heat energy.

Considering the event is supposed to occur after billions of year and supposing humans exist until the time when the sun burns out, how will the Sabbath be calculated as it is to be followed till end of time according to Sh'mot 31:16.

  • Welcome to MiYodeya and thanks for this first question. Great to have you learn with us!
    – mbloch
    Commented Feb 19, 2022 at 16:40
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    That event would indeed be the end of time as far as terrestrial life is concerned.
    – Damila
    Commented Feb 19, 2022 at 21:02
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    This isn't really a good question because human life would die out even before the sun went out and the earth would also be consumed if the sun were to die
    – ezra
    Commented Feb 20, 2022 at 1:17
  • Perhaps the Mishnah in Hagigah 2:1 applies: כל המסתכל בארבעה דברים, ראוי לו כאילו לא בא לעולם, מה למעלה, מה למטה, מה לפנים, ומה לאחור Commented Mar 22, 2022 at 14:07

2 Answers 2


There is discussion about that, but a consensus is unlikely to emerge before the matter acquires some urgency -- that is, when we will all be forced into space.

-Rabbi Ben Tzion Firrer [5730 issue of Noam]: argues that mitzvot are only applicable on earth, because the Torah says:

These are the statutes and judgments, which you shall take care to do, in the land [ba-aretz], which the Lord, God of your Fathers, gives you to possess all the days that you live upon the earth [ha-adamah]. [Deuteronomy 12:1]

But note that the Torah does not say: Don't do mitzvot outside the Land of Israel or the Earth. But Rabbi Menahem Kasher [5730 issue of Noam] argues that mitzvot are incumbent in every environment. (The latter is likely to prevail, in my opinion.)

-When going far from the earth, use the clock on the wall of the spaceship, synchronized at liftoff with the time and place from which you left the earth, and follow the Jewish calendar for that place after that. This makes particular sense because observance can’t ever be truly simultaneous with the place of origin, because of the relativistic twin effect: One twin stays on earth and the other travels in space, and when the traveler comes back he is younger than his twin, and he has actually experienced less time.

-When on a planet in space, one might have to pro-rate the length of the day or the year. Rabbi Azriel Rosenfeld says: On Mars, a “day” is 24 hours and 39 minutes in earth time and a “year” is 687 days in earth time, so one must modify observance of the calendar accordingly.

  • Clocks are a modern(at least to Mosaic times) invention to keep track of time, but the talmud says you should observe the sunsets and sunrises, so would it be a better thing to use timing or follow another star
    – user28218
    Commented Feb 20, 2022 at 2:41

As Jews, we believe this world is only supposed to last for 6,000 years. Which is part of the understanding that the universe was created with the intention to reach an intended purpose. (See Derech Hashem) So this question would only exist in theory.


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