Some Elaboration on the Fifth and Sixth Dimensions
We have no ability to know what the universe really is, because of several reasons: First of all, we are very small, so we only see a tiny fraction of the whole picture. Secondly, the tern “really is” is meaningless – since we are a part of the universe, we can't step “outside”, look at it from several angles and describe what we see. We do, however, have the ability to analyze what we see, make conclusions and create models of the universe. This has been the essence of scientific, philosophical and religious thought throughout human history.
The 3D axis system is a fine way of representing the physical world, and describing it in mathematical terms. If we lived in a 2D universe, the third axis would have been meaningless to us – so we would be convinced that we're living on a plane – even if we lived on a sphere. (In fact, we DO live on a sphere, but since it's so much bigger than us, we think of it as a plane. The 2D axis systems used in maps of the world, do not really represent how the world “really looks like”) Even if our plane would be completely distorted, we would still consider it “flat”, since differences in height are beyond our grasp (the term “height” itself would be meaningless)
Similarly, we can't prove that time is a straight line. More than that – if we accept the assumption that the 5th dimension holds all kinds of additional possibilities to what “really happened”, we can assume that we actually move in a curved or broken line. Every choice we make can be regarded as a “turn in time”. But since we can only experience one moment at a time, our subjective impression tells us that time is a straight line.
And very much in the same way, we can't prove that all the events that did NOT happen are neatly alligned, side by side, on a single plane. Still, we can define any of the events that CAN happen, using five coordinates.
But some events can't happen. In the example above, I could add another option: “I noticed I was late, so I ran faster than the speed of light to the bus station” of course, this is not an option in our universe. We need another coordinate, so we can access events that can happen under alternative physical laws (for example, the 6th axis might represent different speeds of light)
Again, if we could “step outside” and see how the universe “really looks like”, we would see that everything that “could” happen doesn't pile up neatly in rows and columns, but creates some distorted continuum. But for us, what “really happened” is a line and what “could have happened” is a plane. Any option that is not on the plane of “what could have happened” is imaginary: It exists in a different 5D-plane.