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I know there is some discussion in space/planets..

How would you keep shabbos in space?

The Rabbi I asked this shabbat pretty much said the same thing; and you go by Jerusalem time when in doubt.

However, afterwards I was thinking about the laws of relativity and space-time. So based on our current understanding of relativity.. time and space are not always "static".

Example being the faster you move in space the slower time goes.

http://en.wikipedia.org/wiki/Time_dilation

So if we start cruising off to other planets are very high speeds, time would "move slower".. and 25 earth-hours will not equal 25 hours in your spacecraft or whatever it may be.

So how long does shabbat last in space at "warp" speed?

Maybe I watch too much sci-fi.. thanks in advance.

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2 Answers 2

There are a number of opinions regarding the observance of Shabbos in the Arctic circle where the sun may not rise/set for 6 months. Each opinion may have ramifications for space travel where there is neither sunrise nor sunset, as well as the issue you raise based on the relativity of time. There does not seem to be a halachik consensus on these matters. The following discussion is based on the Star-K discussion of this topic.

  1. The Tiferes Yisroel writes that you use the times for Shabbos based on where you came from. Similarly, a space traveler would follow his liftoff point irrespective of his own time frame.

  2. Other opinions regarding Arctic region don't easily translate to a space traveler:

    a. Minchas Elazar who maintains that Shabbos in the Arctic circle will last for six months until the next sunset.

    b. Ben Ish Chai maintains that after 24 hours when sun is above or below horizon, 6:00am and 6:00pm are sunrise and sunset, respectively.

    c. Moadim U’Zmanim who maintains that sunrise is when the sun is at its lowest point in the visible sky.

The Star-K writes that in outer space the problem is still open but two possible opinions are:

  1. keep Shabbos anytime it is Shabbos anywhere on Earth.

  2. Rely on the Tiferes Yisroel above.

Partial quote from Star-K

Outer Space

It is clear from the above that the calculation of davening times and when Shabbos begins and ends would be complicated for Jewish astronauts in outer space. Therefore, a rav should be consulted. Ideally, one should not travel to outer space. If one must go, an astronaut would follow the opinion of the Tiferes Yisroel for davening, and according to some opinions keeps Shabbos anytime it is Shabbos anywhere on Earth. 50 If this is too difficult, one could rely on the Tiferes Yisroel for Shabbos. If one orbits the earth and stays above the area that is between 45oN and 45oS, one would daven each tefilla once per day (despite the continuous sunrise and sunset). One would keep Shabbos when it is Shabbos directly below the rocket on earth. Depending on the season and location, Shabbos could be as early as 2:00 a.m. Friday Universal Time and as late as Sunday 12:30 p.m. Universal Time. V’tzarich iyun.

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As a practical matter, travel to other planets in the solar system would not be fast enough to cause a problem. Also, the fact that within the solar system, we can still keep track, means that one could know exactly when Shabbos would be. For example, C-ship: The Dilation of Time says

The following table illustrates how insignificant the effect of time dilation are for velocities as great as half the speed of light, ...

There are also halchos of "shayara bamidbar" (caravans in the desert) and ships at sea that were isolated and had to keep track within their own "community". Similarly, a nuclear submarine under radio silence would have to keep track and use the base time on the ship.

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