I am not an academic in anyway, just someone interested in the story that is our universe. So my apologies if this isn't a well thought out inquiry.
I've been struggling with a concept for some time (which is probably rudimentary) that I can't even frame into the right words to know where to begin a Google search, so thought I'd try this platform.
I'm trying to wrap my mind around the fabric of space. I can understand the effect of a mass like our Sun and its gravitational influence on the fabric of space, and how the planets fall into indents orbiting that mass. But my questions is, are all the masses in the universe on top of that "fabric"? Essentially, I'm asking if the fabric of space is all encompassing in the universe, is it at all points North, East, South, West, above, below, in between, or just a horizontal plain that all masses reside upon? I know that space-time twists in relation to a mass, is space-time manipulated the same way above the Earth and Sun as it is below?
Not sure if I'm framing this question correctly, but any insight you can provide would be beneficial.
Best Answer
The rubber sheet analogy, and all pictures that go with it have mislead many people (including me) and so now I must request that you completely and utterly banish that thought from your head. No sheet.
Instead, imagine it as a series of grids, like sheets of graph paper, spaced such that they are parallel to each other, going in each direction for infinity. And now, imagine another set, perpendicular to the first. If this is a bit hard to imagine (which it is, this is very abstract) you might try imagining the Cartesian coordinate system in 3 dimensions and putting in the gridlines. Now, we put in objects. Before we continue, remember, this extends infinitely in ALL directions - up, down, left, right, forward, backward (or whatever passes for these directions).
Set an object, let's say a planet like Earth, into these grids. Make the grids "come toward" the Earth, so that the Earth is sort of "sucking in" the grid around it, and pulling other nearby objects enmeshed in the grid towards it. This is a three dimensional universe. But there are four dimensions...there is also time. We cannot picture four dimensions, except mathematically, as Countto10 said, so merely keep this in mind instead of trying to add this to your mental image.
So, to more explicitly answer your question, spacetime is all around - there is nothing outside of spacetime, and there is merely the objects within it. These bend and twist spacetime, therefore affecting other objects.
Hope this helps; I'd be glad to clarify further if necessary.