Shabbat (and other times) on Mars

[cellio]

I was recently asked about this, and I don't know what the current thinking is.

The question of when an astronaut observes Shabbat (while in space) is well-understood. [1] But what happens when we colonize other planets and your hometown is on Mars? Do you count six Mars-days and observe the seventh as Shabbat? How long is a month (and how do you decide which moon)? Is it still desirable to stay in sync with Earthly seasons, or will that go out the window? If you follow the sun as locally experienced, what happens when that causes hardship? (Does the lunar colony observe one ~29-day Shabbat every seven months?) There must be commentary on this by now from sources other than Wandering Stars, but I don't know what the popular opinion is.

[1] I know of three opinions for the astronaut in space: follow your hometown, follow the city from which you launched (your port of departure, like for ships), or follow Jerusalem. All of these involve a ~25-hour Shabbat every seven days, like on Earth, even though your orbit might cause you to see a 90-minute day. But the astronaut is, by definition, just visiting.

Comments

[goljerp]

I hate replying to myself, but re-reading your post, I realized that I totally ignored your point about weeks. That is a good point; if Shabbat is every 7 days, but a week on erehwon is 8 days, Shabbat would float... and that would be odd, indeed.

(maybe they would use 10 day weeks - the Metric calendar - that Garrison Keillor used to talk about: Oneday, Twoday, Tuesday, Wednesday, Mensday, Ladiesday, Thursday, Friday, Saturday, and Sunday. )

[geekosaur]

Er, weeks don't correspond to any natural time division; they're purely a man-made (or HaShem-made, depending on viewpoint) invention. Not even to lunar months (which are 29+ days, not 28). And the ancient Jews were more or less the only culture that kept anything like a week, much less Shabbat. (Babylonian kings occasionally declared "shappatu", but not on a regular schedule.)

IIRC the Rabbis of the Talmud understood this and specifically treated the week as an artificial time division instituted by HaShem specifically for Jews.

[zevabe.livejournal.com]

There is nothing that makes a week except Bereishit. A day is one rotation of your planet. A year is one revolution of your planet around its star. And a month is from one phase of the moon to the next iteration of that phase (which may be Earth-centric since other moons don't have to revolve and rotate at the same speed)*. But a week is, as far as I understand, not defined by a physical phenomenon but by human invention/convention. So seven days on mars is a week, just like 12 doughnuts on Mars is still a dozen. Also, aren't Martian days about as long as Earth days, so that isn't a big conversion over?

* Could someone explain to me what would happen in terms of phases of the moon(s) from the perspective of an observer standing on Mars? Would it look like phases of the moon here but just over some other period of time?

[geekosaur]

Actually, the phase of the moon has nothing to do with the moon's day vs. its orbital period; it's solely related to its angle relative to the Sun as seen from the Earth, so depends only on how long it takes the moon to orbit the Earth.

As seen from Mars, phases would behave rather differently, because they would be restricted by the Sun-Earth-Mars angles as well as the Sun-Moon-Earth angles. Also, the moon would usually be invisible: either behind the Earth, or in front of it and drowned out except when Earth and Mars are fairly close to each other (but then it would be a dark spot against a mostly dark spot, instead of a light spot against a very light spot).

[zevabe.livejournal.com]

I think I was insufficiently clear. If I stood on Mars, what would the phases of the moons of Mars look like? How long would a full cycle (new moon to new moon) take?

[geekosaur]

Wikipedia knows all....