[sp332]

I don't think a ring of galaxies is going to look very different from anyplace within the solar system. Anyway I think moralestapia's point is that the circle might not be centered on us, so the redshift of the galaxies would not be the same. We could still determine that a circle exists by plotting the galaxies in 3D.

[moralestapia]

No, I mean, a 2D circle could appear as a line from a certain perspective in 3D space.

Spin up your mental model of a circle in 3D space, look at it from a vector perpendicular from its diameter, rotate it 90 degrees in any other axis but the one you're looking at it; on that 2D projection, it will be a line.

[glenstein]

>No, I mean, a 2D circle could appear as a line from a certain perspective in 3D space.

Right, and as a matter of fact that's exactly what we DO see with the Milky Way galaxy. It can be conceived of as a circular disc, more or less, but in our sky we see it from the side, as a streak or a band rather than a disc.