Imagine a box. A big box. A very big box. Big enough to stretch from the Cardassian border to where the Death Star used to be. Technically, it would have to stretch several hundred mega-parsecs in every direction. A parsec is 3.26 light-years, so our box would be so big that it would take a beam of light over a billion years to travel across our box.
According to the "Cosmological Principle", the universe is basically the same everywhere on a large enough scale. In other words, if we imagine a big enough box, its contents would be representative of the contents of the entire universe. It would be like a Noah's Ark of the stuff of the universe. The whole universe would then just be like that same box, just more of them, stacked beside and on top of each other for a long, long ways...
We happen to live in one of those boxes, in no special place in the universe (as far as we know).
But, what we really want to know is, What is in the box?In the "old cosmology", which really finally gave up the ghost over the past twenty years, the universe was made mostly of
To learn more about the nature of the atomic matter and dark matter and how they relate to particle physics, see the other pages!