> Shouldn't it be 13 2 = 26 across?* I guess this depends on how you define "across". Our Hubble sphere is all the space around us for which light has arrived

> Shouldn't it be 13 2 = 26 across?* I guess this depends on how you define "across". Our Hubble sphere is all the space around us for which light has arrived. If the universe is infinitely big, then yes, there are things that we can see that are 26 billion light years from each other. However, they can't see each other, and so they are not causally connected to each other, even though we are causally connected to both. >Is some space aliean on the edge of the universe going to see 13 light years in all directions? An alien at the edge of our Hubble sphere will live in a different, overlapping Hubble sphere, from which they will see 13 light years in all directions around themselves.