blackllotus,
Perhaps it is my own lack of comprehension, but I cannot perceive a universe that is without a boundary somewhere.  However, I cannot perceive one that does have a limit either.  One would have to ask what is beyond that boundary, which is too imcomprehensible for even science to tackle.  However, I do not define the universe as being the entirety of space.  The univese only encompasses the physical celestial bodies, and beyond their range, I think that there is nothing but a void.  However, if anyone wishes to enlighten me, please feel free to do so.