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what if: a fast moon
2020-09-08 13:47Phobos, the lower moon of Mars, has an orbital period under 8 hours, so from the surface it looks much like a artificial satellite of Earth: over the course of a night it rises in the west, sails across the sky, and sets in the east. In fact it does so twice. Nothing in Earth's natural sky is so quick and regular, and I find myself wondering how astronomy and astrology might have been different if we'd had a Phobos. Not very productive wondering, but still. I suppose it might have been a nocturnal timepiece.
The fact that it really obviously moves west to east seems like it might have had some effect, compared to everything else rising in the east. (The Moon moves eastward over the course of the month[1], but that may be less obvious.)
The other moon, Deimos, has a 30 hour period, slower than Mars's day, so it rises in the east. But it should move quite visibly against the stars, and it takes a couple days to set for a Martian observer.
Wondering about all this reminded me of my old wondering whether the local presence of monkeys, an obvious link between humans and animals, had an effect on Eastern religions.
[1] Over the course of a night the moon moves east to west, like the sun and stars. But night to night, the moon at dusk starts over the western horizon as a waxing crescent, moves overhead as a waxing half, and appears over the eastern horizon as a full moon.
The fact that it really obviously moves west to east seems like it might have had some effect, compared to everything else rising in the east. (The Moon moves eastward over the course of the month[1], but that may be less obvious.)
The other moon, Deimos, has a 30 hour period, slower than Mars's day, so it rises in the east. But it should move quite visibly against the stars, and it takes a couple days to set for a Martian observer.
Wondering about all this reminded me of my old wondering whether the local presence of monkeys, an obvious link between humans and animals, had an effect on Eastern religions.
[1] Over the course of a night the moon moves east to west, like the sun and stars. But night to night, the moon at dusk starts over the western horizon as a waxing crescent, moves overhead as a waxing half, and appears over the eastern horizon as a full moon.
