Science Forums 2

[Turtle]

Originally Posted by modest

Damn Turtle, I think you've given me a brain hemorrhage.

I think... perhaps... just maybe... you've got your up and down backwards. Or, perhaps the astronomical community has their galactic coordinate system backwards. Or, perhaps I'm turned around... something has gotten turned around

Ok, starting over...

I don't think the galaxy rotates counterclockwise as viewed from the north galactic pole. I think it rotates clockwise as viewed from north. I don't think it follows the right hand rule (at least, not in the galactic coordinate system). A paper, such as this:

The Sun's Distance Above the Galactic Plane

which uses the galactic coordinate system would seem to be saying that we are above the ecliptic as is defined by that coordinate system. And I'm pretty sure, that according to that system, viewing the galaxy from the north galactic pole would show clockwise rotation.


-source


The above pic would have the galaxy rotating clockwise as viewed from the north. A positive latitude (above the galactic plane) would then be above the disc (as viewed from the side) where the disc is rotating left.

I have a suspicion of why the GCS doesn't follow the normal right hand rule. If it did then earth's north pole would point to the south side of the galaxy. In order to have earth's north and the galaxy's north roughly the same direction, the left hand rule is used. But, that's just a suspicion—I don't know if that's the reason. Nevertheless, as the pic above shows it, the galaxy does rotate clockwise as viewed from the north. It rotates in the direction of 90 deg. longitude.

Yes / no / maybe???

~modest

I'm afraid I still have not achieved my 'Ahah!' moment on this. I'm particularly vexed that none of these sources say outright the direction of rotation. It's a simple question and by damn I want a simple answer. Your answer appears simple, but then you resort to suspicion which at the least tells me that the references so far don't make it clear to even you. Can we keep looking for an unambiguous source? If ya see a turtle on a fence-post, you know it didn't get there by itself.