Having an idle moment or two, a bit of speculation:
One way to look at the universe is to imagine the axes of a simple x, y graph. If there is anything beyond the universe, then it acts as a y axis to our x axis. Basically, it doesn’t matter what happens to the y axis, as it has no effect on the x axis, which retains all its points as they always were.
The image is of a six dimensional graph that, plus the independent timescale sliders, gives 8 dimensions. The cube ABC is free to move anywhere within XYZ, which are other dimensions. As time in the XYZ cube does not affect time in the ABC cube and both types of time are operating, it is possible that ABC moves relatively in any direction, instantly and at random. (Or, maybe, it is XYZ that is moving, or maybe both.)
If you imagine
(i) ABC is our universe and the red dot is single point within our universe with co-ordinates A’, B’, C’, T2’
(ii) The red dot can only be described by A,B,C, & T2 as those are the only dimensions it has, otherwise it would like trying to describe a rhinoceros in terms of lampposts, flowers and oceans.
(i) It does not matter and we cannot know where we are within the greater cube XYZ as, like the x,y axis example above, none of it does, or can, affect us.
(ii) Only an object that has all the X,Y,Z and T1 coordinates can exist in Universe XYZ
(iii) Only an object from Universe XYZ that has all the X,Y,Z and T1 coordinates and
all our coordinates can exist in both universes.
(iv) Only an object from Universe XYZ that has all the X,Y,Z and T1 coordinates and
all our coordinates can affect us.
(v) If it had our coordinates, it would be detectable.
(vi) If it lacks any of our coordinates then it is undetectable and thus, by definition, cannot interact with anything in our universe. (If it could interact, then we could detect it.)Does this mean that we are inside a greater universe?
We don’t know, we could be the greatest universe and all else is inside us, or some mixture of the two but the same would still apply.What would happen if a moving object had coordinates, X,Y,Z, & T1, and A,B,C, & T2?
An observer in Universe XYZ would see the object travel from one place to another even if Universe ABC were in the way. He would not see universe ABC
An observer in Universe ABC would see the object in Universe ABC but it would not cross the boundary; the boundary would always be well ahead of it. The boundary of our universe, for us, is probably the sum of the points from which nothing in our universe is visible; likewise from our perspective, the end of the universe is the farthest we can see (c.13Billion LY).Would observers in both universes see the same object?
No; it is impossible, the dimensions are different, they are different things – see the rhinoceros above. Would they perceive it as the same thing?
We will never know.What of String/M-theory that postulates other dimensions here in our universe?
They cannot be physically shown to exist – they can only exist as a concept; a conclusion of probabilities reached from observing our dimensions. This is the major problem with the theory – there can be no direct observations.What if there is another universe, PQR, next to XYZ?
It would not have any effect on either, nor would any of its objects.