I'm not exactly clear on the oft-used gravity example of a bowling ball sagging in the middle of a rubber sheet as an analog of the warping of space-time (i.e., a gravitational well). That example has an implied direction built into to it given that objects might fall into a well, but they wouldn't fall UP a well. What gives?

Relatedly, do astronomers have a preferred direction for viewing the solar eliptical plane and is it something more than a preference or is based on some other larger galactic association (such as the direction of gravitational wells)?

Thank you for a reply.

If a small ball rolls into that well a little off center and is going fast enough, it will climb back out.
The orientation of that well in the rubber sheet is merely a graphical representation of the magnitude of the spherically symmetrical spacetime warp around a massive object as a function of distance from the center. It is not indicative of any preferred direction in real space. I look upon it as a clunky analogy aimed at making some concepts of 4-dimensional spacetime visualizable. It causes conceptual booby traps if taken too literally.

If I am off base here the real experts may fire when ready.

I agree with you. The sheet-ball analogy is not good. We should find another one.

Just imagine the ball bending the space in all directions, thats a 3D version and it eliminates these problems.

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You shouldn't be "exactly clear" on that analogy, it's actually of quite limited value and should not be taken too seriously. It certainly doesn't encapsulate all the relevant issues, and personally I see it as something of a swindle. But there can be a thin line between "analogy" and "swindle".

It's the "ecliptic" plane, and we tend to see it from the northern hemisphere, for entirely personal reasons that has nothing to do with gravity.

The problem with the rubber sheet theory is that it is 2-dimentional, and it assumes that space is a flat sheet, which it is not.

It just makes it easier for people to understand, and that is why it is used.

Why do you do this... ?

This subject is already being discussed in another thread. Go look at that...

The universe is not a single plain rubber sheet distorted by gravity forces.

That is only a over simplification of the understanding of space time distortion...

As for why it's viewed from this or that angle... ? It is pretty.

Our place in the vast expanse that is depicted from any point of view is only a attempt to understand or convey a understanding of that.

The expanding balloon or the distorted rubber sheet are not as it is but only tools for understanding.

Playing with bowling balls on a trampoline is astro physics... maybe, maybe not.
But it will help you understand the mechanics of gravity.

Are you referring to the fact that diagrams of the solar system often have the ecliptic plane coincident with the paper (or screen) and the viewer is presumed to viewing from the north side? If so, that is simply an arbitrary standard. The galactic plane is inclined 60° to the ecliptic and really has nothing to do with this matter.

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Curt Renz - "Centaur"
For monthly astronomical calendar visit:
www.CurtRenz.com/astronomical

I think the bowling ball / rubber sheet metaphor is confused because it involves real gravity, pulling the bowling ball towards the ground. So you naturally suppose that the point of it is that particles are pulled into the dip around the bowling ball by gravity. But I think that whoever invented that model may have intended to consider particles that are only deflected by the distortion of the sheet - for instance ants trying to walk in a straight line across the sheet would walk a bent course. (We'll overlook that ants are usually following the scent trail of the ant in front.)

I don't understand the second question. Are you asking about the coordinate system used on the celestial sphere, or which parts of the sky are most observed? I think it's assumed that the stars are stationary when you're mapping objects in the solar system - and since most bodies in the solar system lie close to the ecliptic plane, i.e. the solar system is nearly two-dimensional, people studying solar system objects are mostly looking at the Zodiac for background.

I think that this galaxy isn't a good basis for a coordinate system because distance of this or that star from here is difficult to measure accurately, and because it's rather messy - stars orbiting the centre at different rates, and odd bits hanging on around the edge. And a space-warping black hole at the galaxy's centre isn't going to make cartography any easier either...