Would the sun rise in the west or in the east on the moon?

smellycat6464

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According to the google, both the moon and Earth rotate anticlockwise of their axes.

The sun rises in the east on Earth, so I would expect the same on the moon, right, since they spin in the same direction?

Thanks, and happy writing.
 

mirandashell

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Erm.... doesn't it depend on where the Moon is in relation to the Earth?

I say 'erm' cos that makes sense to me but I'm probably wrong.
 

smellycat6464

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Trust me, my mind is 'erming' as well! I tell myself, "well, the sun always rises in the east here (unless that statement is wrong, which means I regret never taking Earth Science in high school or college)."

Then again, things would get reversed between someone on Earth facing the moon and someone on the moon facing Earth? But would one experience sunset and the other sunrise, or the same phenomenon but with reversed cardinal directions.

*rips hair out!*
 

amergina

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Here's an interesting tidbit:

http://www.physlink.com/Education/AskExperts/ae616.cfm

It's 29.5 days from sunrise to sunrise, so 14.75 days between sunrise and sunset.

Doesn't solve the "rise in the east or no?" question, but it explains a bit of how that looks!

(ETA: fixed info, because I am a doofus)
 
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mirandashell

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The thing is though.... Earth has a magnetic field so North is North no matter which way you're facing. But the Moon doesn't. So is reasonable to say the Sun rises in the East when you're on the Moon?
 

Mr Flibble

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Here's a titbit I learned in the SFF forum...

Ready?


Where the sun rises is defined as the east. Even if it is not relational to our east (ie at right angles to the poles). Same with setting/the west. The "east" is where the sun rises, the "west" is where it sets.

Now, how true that is I am not sure though I do recall links (I do not recall where they were to, sorry. I'll try to dig up the relevant thread).

Might be worth a gander?
 

amergina

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The Moon *does* have a magnetic field, but you're right, it's not dipolar since it lacks a spinning, molten core to act as a dynamo. So there is no magnetic north or south pole on the Moon.

However, the Moon does have an axis on which it rotates*, and so has geographical poles, despite its lack of magnetic ones

(Earth has a rotational axis too, of course. The Earth's geographic north and south poles are located in a slightly different place than our magnetic north and south poles. They're separate things.)

We humans like to map stuff, so we've chosen to map one rotational pole as north and one as south. The north one is the one that points in the same direction as our north pole. (Which is defined as the pole you'd see if you were looking down upon the Earth and Moon from Polaris.)

*The Moon is tidally locked to Earth, so one side always faces us, but it still rotates on its axis as it revolves around the Earth.

(http://en.wikipedia.org/wiki/Near_side_of_the_Moon shows sunlight moving from east to west across the lunar surface)
 

Locke

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The sun rises in the east on Earth, so I would expect the same on the moon, right, since they spin in the same direction?

To add some science lingo to your query: the moon is tidally locked to the Earth; this is why the same side of the moon is constantly facing us.
 

benbenberi

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What Mr. Flibble said: the sun always rises in the east, no matter where you are. East is defined as the direction where the sun rises, on the moon, Mars, Pluto, or wherever. It's determined locally, independent of earth's rotation.
 

morngnstar

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Here's a titbit I learned in the SFF forum...

Ready?


Where the sun rises is defined as the east. Even if it is not relational to our east (ie at right angles to the poles). Same with setting/the west. The "east" is where the sun rises, the "west" is where it sets.

Now, how true that is I am not sure though I do recall links (I do not recall where they were to, sorry. I'll try to dig up the relevant thread).

Might be worth a gander?

This time of year, the sun rises in the southeast. Does that mean southeast is now east and east is now northeast? And on Uranus the sun would rise nearly due north or south part of the year. I guess you mean whichever direction is closer to sunrise out of the two that are perpendicular to north.
 

Brightdreamer

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Here's a titbit I learned in the SFF forum...

Ready?


Where the sun rises is defined as the east. Even if it is not relational to our east (ie at right angles to the poles). Same with setting/the west. The "east" is where the sun rises, the "west" is where it sets.

Now, how true that is I am not sure though I do recall links (I do not recall where they were to, sorry. I'll try to dig up the relevant thread).

Might be worth a gander?

I keep thinking there was a sci-fi novel Many Years Ago where one planet had its sun rise in the west; it was a rather gawdawful backwater colony that had had too much trouble just establishing itself to bother with the west/east thing, so everything wound up backwards. (I may be remembering this wrong...)
 

smellycat6464

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Oodles of thanks to everyone who posted! So much more than my original question has been clarified. Hooray to all of you lunar experts ;D
 

Layla Lawlor

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Here's a titbit I learned in the SFF forum...

Ready?


Where the sun rises is defined as the east. Even if it is not relational to our east (ie at right angles to the poles). Same with setting/the west. The "east" is where the sun rises, the "west" is where it sets.

Oh wow, weighing in as another SF writer, this is so OBVIOUS when you think about it, but I had never thought about it in that light before! *scribbles mental notes busily* Thank you so much to you and benbenberi for pointing this out. :D
 

King Neptune

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And if the direction of rotation were opposite the direction of the orbit would that still be East?
 

King Neptune

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Yes. Direction of orbit doesn't enter into the question.

I wasn't clear. What if the rotation on its axis were opposite? I can easily imagine a rogue planet being captured and having an orbit and rotation on its axis that would be opposite to everything else in the system.
 

morngnstar

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I wasn't clear. What if the rotation on its axis were opposite? I can easily imagine a rogue planet being captured and having an orbit and rotation on its axis that would be opposite to everything else in the system.

No need to imagine. Venus does this. Although when I went to Wikipedia to check my facts, they say the sun rises in the west on Venus. Maybe there is not consensus. If you say by definition that the sun rises in the east, then that just means that north points the opposite way on Venus compared to Earth.
 

King Neptune

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No need to imagine. Venus does this. Although when I went to Wikipedia to check my facts, they say the sun rises in the west on Venus. Maybe there is not consensus. If you say by definition that the sun rises in the east, then that just means that north points the opposite way on Venus compared to Earth.

Yes, that's what I was thinking.
 

Kevin Nelson

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On Venus, there's yet another complication. Not only does it rotate "backwards," but it rotates very slowly--its sidereal day is actually longer than its year. So the motion of the Sun in the sky will be mostly controlled by the planet's revolution around the Sun, rather than by the planet's rotation. (Maybe it's a good thing you can't see the Sun for all the clouds....)

Even worse, you could imagine the following sort of scenario. Take a planet that revolves around its sun in 100 (terrestrial) days. It rotates in the same sense that it revolves, in 200 days. The motion of the sun in the sky will be determined by its revolution. So if east is defined as the direction in which the sun rises, and north is defined as ninety degrees to the left of east, then you wind up with a very strange situation. As viewed by an external observer above the north pole, the planet would rotate clockwise.
 

blacbird

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If you say by definition that the sun rises in the east, then that just means that north points the opposite way on Venus compared to Earth.

Not exactly. The situation on Venus is unique; its rotational period is very slow, and longer than its revolution in orbit around the sun. But it actually does rotate in the same direction as its orbital revolution. Because the rotation is slower, however, it means that sunrise there will be in the "west", as defined by use mere Earthloids. It also won't happen very often.

The moon, being tidally locked to the Earth, rotates in the same direction Earth does, but only every 28 days or so. Watch the phases of the moon over a month, and you'll clearly see this.

caw
 

morngnstar

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No, Venus actually rotates backward and rotates slowly. If it didn't rotate at all, its motion around the sun would make the sun rise in the west. If it rotated backwards without going around the sun, the sun would also rise in the west. Both factors work together.

The phases of the moon don't have anything to do with the rotation of the moon. It would have the same phases if it were not rotating, or rotating faster, or backwards. The only way you can tell the moon is rotating is that it looks like it's not. The "man in the moon" is always facing us, only different parts get shadowed. Since the moon is going around the Earth, ironically it has to rotate to keep the same face to us, as if it's hiding its backside.
 
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blacbird

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On the issue of the rotation of Venus, I just found this interesting data table:

http://www.windows2universe.org/our_solar_system/planets_table.html

Note that, for Venus, they cite the rotational period as -243 Earth days, meaning that it rotates "backwards" relative to the direction of its orbit. However, most strangely, they cite the inclination of rotational axis as 177 degrees, meaning that they regard it essentially as being upside-down relative to the rotation/inclination relationships of most other planets (Uranus being an exception; it essentially lies sideways).

I have no idea why this table regards Venus as being upside-down, but the key point, really, is that its rotation takes longer than its orbital year.

caw
 
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