According to what we have found in the last few hundred hears, there's always a bigger structure than we were able to imagine before, and a smaller one. First we thought the Earth was the center of the world, then the Sun; afterwards we found out about galaxies, galaxy clusters, and finally super-clusters.
In the micro-world, we thought at first that nothing could be smaller than an atom (atom = Greek word for individable), then we found the subatomic particles like proton, neutron, electron, now we have dicovered the world of quarks. We even found anti-particles!
If there's a system behind all this, the discovery of even bigger structures (or even smaller ones) will go on and on and on. So I think that there is a multitude of universes, embedded in even bigger structures etc. Perhaps our whole universe is just a single quark in a super-universe... I don't think we stand a chance to discover all of them, not even in millions of years.
PS: This is the ideal thread for my signature... 😎
