The visible universe is incredibly large. Only recently have we had the experimental tools and observational data to truly get a grasp on the numbers, and the numbers are astounding. They are so large that even when we come up with analogies to describe them, as in the above video, they still are hard to absorb. The number of stars and galaxies are beyond astronomical (see what I did there?). And those are just the ones that we can see.
As big as these numbers are, they are nothing next to eternity or infinity. Those are some truly absurd concepts (outside of mathematics, where infinity serves very useful purposes). Christianity and other religions bandy about terms like 'eternal' and 'infinite' with amazing (and I would say alarming) frequency and nonchalance. It's as though to think about spending an unending amount of time doing, well, whatever one thinks one does in heaven, were analagous to a weekend vacation to the beach. Yet clearly it's not. And what's worse, we are charged with coming to believe an impossible story about an unknown and unproven afterlife, with the promise of unending pleasure, or the pain of unending torture. Aint that grand!?