What is the Universe?

I love my daily "Facts From Space" calendar I keep in my office. Every day provides a new space based fact. Occasionally, as you saw from a post on this blog last week, the facts are a bit misleading or don't fully dig into the truth. But for the most part they are very good. Last month, the following space fact came up.

An interesting question and right now one we don't have to worry about too much, but could be a bigger question in the future as technology improves and we learn more about the cosmos. The calendar fact, however, ignores what is a more likely solution. Just change the definition of 'universe'. There's certainly precedent for this. Astronomers changed the definition of 'planet' in 2006 to account for the new discovery of several Pluto-like objects. The former planet Pluto no longer qualified as a planet under the new planet criteria and was moved to the newly created category of 'dwarf planet'. 

As we learn more about the Universe and potentially other universes, maybe we change the definition of universe. Maybe there's a universe and then there are dwarf universes? Not sure how that would work, but the point is definitions change with new data. The definition of 'planet' is a perfect example. Science continues to fill in the gaps and answer questions, and as a result, old definitions are no longer appropriate.