The Universe or Cosmos

http://hubpages.com/hub/universe_wallpapers

One definition of the Universe or Cosmos is "everything that was, is, and will be". With that definition, there can be no other Universes, except in your imagination. However, we cannot exclude the possibility that the Universe of that definition is divided into separate parts that are not connected at all or that are only connected occasionally or through narrow passages, and then you could call each one of the separate parts a Universe.
A practical definition of the Universe is "everything that we can see or measure". The Universe of that definition is sometimes referred to as the Visible Universe. We cannot see infinitely far, not even in principle, because the Universe has only a finite age and because information cannot travel faster than at the speed of light. Because the Universe is about 14 thousand million years old, we have not yet received any light or information from places that are so far away that it takes light more than 14 thousand million years to get here.
It is likely that the Universe continues beyond the boundaries of the Visible Universe, but we can't yet know anything about those as yet invisible parts. It follows from the current ideas about the formation of the Universe that space for vast distances beyond the current edges of the Visible Universe probably looks quite similar to the parts that we can already see. It is not known if the Universe including the parts that we cannot yet see is finite in size.
The Universe is like a big bank of fog. The part of it that we can see is roughly a sphere centered on us. We can't see beyond a certain distance (let's call that boundary our "edge of vision"), but expect that there is vastly more Universe beyond that distance, and that conditions there are quite similar to what they are here. Unlike for a bank of fog, we can't even hear or use radar or infrared rays to figure out what is going on beyond the part of the Universe that we can see.

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