>> Sunday, December 13, 2009
Jeff King asked: If space has no ending, how is it believed that our universe is the only one in existence?
Who says there is? I don't and don't believe there is (depending on how one defines "universe") only one or that the term "ending" or "limits" means anything with regards to it. The universe is effectively the extent of existence that we see and believe exists. We don't know what, if any, boundaries there are to it.
There are several ways of tackling this question, which would actually demand multiple posts, not the least of which is the extent and meaning of "infinity." If you want that, ask about infinity and I'll go through it in its own post. There's also the whole concept of multiverses and that also deserves it's own post.
Today, I'm going to talk about what we know, what we surmise about the "universe." Merriam-Webster's first definition of "universe" is: the whole body of things and phenomena observed or postulated. That's an important distinction. The universe is everything we can detect/see/etc. and everything we can surmise exists.
What does that mean? Well, first, it means that what we think of as the universe is based on the parts of the universe we can see or detect and then, added to that, what we surmise exists. That means that we are (a) limited in our view of the universe by our observational abilities, limits that may not exist in the actual reality (which we can't see all of) and (b) what we surmise to be beyond the bounds of our detecting ability is based on the part we can see, which, again, may not exist in the actual reality. The universe as we "perceive" it, in other words, may not have much or anything to do with the actual "universe."
Confused? Let me try an analogy. Let's say, someone is a clown fish in an anemone in a coral reef. For such a creature, the "universe" is limited to the small area of the coral reef around him. Even if his reef sits on the edge of the Pacific and looks out over the huge expanse of the ocean, he has no way of imagining the huge and diverse spots with dark arctic depths beneath the ice to the north and south or lava heated vents in the darkest corners of the ocean's depths, the huge monstrous creatures that swim in other areas of the ocean. Nor does he have a frame of reference for rivers and lakes and other freshwater ecologies. His idea of the world/universe is limited by the extent he can see and understand. Even if his anemone is in a big aquarium and people wander by, he is still limited.
He has no real way of understanding that the world outside his little world has air, even if he sees us breathing air and walking about. His world is water so that's his presumption about the rest of the universe. His world is warm and salty and filled with light. It also looks like something without limits as, indeed, the ocean would be for a wee fish.
We have huge telescopes and detectors and know a great deal about things thousands, even millions of light-years away. It's infinity as far as we are concerned. But, we have no way of knowing if there are rivers and lakes and vents and trenches and islands and whatever beyond the extent of our detection ability.
What I'm saying is, we don't know the extents of reality or the nature of its extents. Does it have boundaries? We haven't found them so far. Is there only one universe? Well, universe is as much a part of our minds as it is reality and, far across the expanses of space, there might be other intelligent dreamers imagining a universe as different from ours as the top of Mount Everest is from the coral reef (if not more). Reality likely includes both of these pockets of universe and who knows what else besides.
Did that help?