Think of the universe as a firework. There is the big bang, then the universe expands, and then it eventually fades away. What we know as space-time is really just the shell of the sphere that is formed by the expanding firework. Now imagine two fireworks going off at about the same time. In your mind think of them as intersecting each other. The intersection would form an intersection circle (more or less). This means that everything along that circle would be the same between the two universes. If you had three or more universes that intersected each other, then it would form an intersection point. This is what is. Imagine the grand finale of a fireworks show with everything going off at once. This is what is. What we observe is like a snapshot photo of this event. It appears to be chaos, but there actually is a structure to it, and you can map it out.
What this means is that each point in space-time is actually an intersection point. In fact you can think of yourself as an intersection point, but the point actually extends all the way down to the sub atomic level. Imagine you are an intersection point. I am a different intersection point. From my point of view there is only one of me and multiple of you. From your point of view there is only one of you and multiple of me. As we move apart in space-time (i.e. in distance and time) my observed intersection point will remain constant while yours will appear to diverge (from my point of view). The multiple you will become more and more dissimilar. As we move to the present and if you are standing next to me, then the multiple you will converge. This is an important concept in my mind.
I have often thought that if you take the intersection point all the way down to the sub atomic level, then the particle will enter a quantum state. What you are really seeing is the particle state jumping between alternate universes. When the particle is observed, then you are seeing its state in only one of the universes. If we could use this knowledge to calculate the curvature of a universe, we could extrapolate this to calculate the size of this universe.
We don’t really notice any differences in our everyday experience because our brains are tuned to operate at the scale of the intersection point that we exist in, but it is interesting to try to be aware that we actually exist simultaneously in multiple universes, and that our actions take place in all the universes that intersect us. I have always thought that we can use this awareness to choose our actions such that we can maximize the beneficial effect in all the universes that intersect us.