Okay so spacetime curves and light follows that curve. So how are Globular Clusters “above” our plane? And then is there anything DIRECTLY below the Globular Cluster? How does that work unless it’s 4D but the 4th D is time and time follows “causality?” and doesn’t go up? Help my brain hurts a little
In: Physics
So, I think where you might be getting confused is the classic: “imagine spacetime is a big rubber sheet” demonstration. [Something like this](https://i.stack.imgur.com/pYYeY.gif). When you place an object with mass onto the sheet, it creates a divot in the fabric that holds other objects on the sheet trapped in its “gravity well”.
This demonstration is good, but it (along with every other analogy) is not perfect. It’s a simplified version of reality, because it demonstrates objects sitting on a 2-dimensional surface. When you place an object with mass onto the 2D rubber sheet, it curves* into a third dimension.* In other words, the rubber sheet has *length* and *width*, and then the curvature has *height*.
However, space, obviously, is 3-dimensional. The actual “fabric” of space isn’t a flat sheet, but a 3D one, with length, width, *and* height. You can travel up, down, left and right (and anywhere in-between) in space. That’s why you can have stars “above” and “below” each other, like you were saying.
So, where the 2D rubber sheet expands into a 3rd dimension when it is stretched by some mass, an object in our 3D universe stretches the “fabric” into a 4th *spatial* dimension. This higher spatial dimension is often called “the bulk”.
Since our human brains are incapable of imagining what a 4th spatial dimension would look like, we simplify things by collapsing our 3D world into a 2D one (i.e. a flat rubber sheet) so that the 4th dimension becomes the easier-to-comprehend 3rd dimension.
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