From this thread
I am willing to accept that there is nothing outside of the balloon, as near as you folks can tell anyway.However, I would very much like to know where the four dimensions of space-time are supposed to exist.
In the analogy, we have the advantage of observing the balloon from outside the balloon, even though within the bounds of the analogy there is no outside the balloon from which to observe. We don't have that advantage in reality, though. We can't leave spacetime and observe it from outside. Nevertheless, we have to grapple with the apparent fact that the universe is centerless, and one way to deal with it is to discard the idea of spacetime extending infinitely in all directions and consider the idea that it loops back on itself somehow (analogously, the way 2D-space loops back on itself on the surface of the balloon).
Let's take a look at where this conclusion of centerlessness comes from:
1. We observe objects in space moving away from us and one another, and so it appears that the universe is expanding.
2. We observe objects moving away from us at a uniform rate, and so it appears initially that we're smack dab at the center of the universe, which is pretty surprising.
3. What's even more surprising, though, is that the distant objects are moving away from each other at the same uniform rate, which doesn't make any sense in a model with an outward expansion originating at a specific center. Picture the balloon again, and imagine all the dots on the balloon moving away from each other at the same rate that they're moving away from the center of the space inside the balloon. It doesn't work. Draw the vectors if you don't believe me.
So centerlessness is a conclusion based on observation. "Curved" spacetime is a hypothesis put forth to deal with it.
You see, if we merely existed in a hologram, there in effect would be nothing defined outside of it, although it would appear to expand outward, within the parameters of the hologram that is. While for the same reason, there would be nothing defined in its center, simply because the center is defined within the hologram. And, since the hologram doesn't really occupy time and space, but rather provides the illusion of time and space, there's no need for it occupy anything other than a single point ... which, in effect doesn't exist in that sense either. Hence we have the notion of everything exanding away from everything else, simply because it all originates precisely at the same point ... and yet, doesn't expand into anything.Yes, but a two-dimensional plane in and of itself does not contain anything. However, if what you're saying is that everything exists within this two-dimensional plane, then it suggests that we are living in some sort of illusion and, that in fact somebody has pulled the wool over our eyes. Which, of course has been my contention all along. But then again, it might make more sense if we said everything existed relative to the observer. Isn't this in fact something that Einstein said? Which of course makes even more sense when I say we are not to discount the observer. Not within the parameters of time and space anyway.![]()