Enjoy the two universe without videos; one with a basic explanation and the other with a simple and silent visual measurement of size.
When looking outward, looking without, there are the things we can 'see' with our eyes, and there are things we can only imagine or guess at.
The universe without is an observable and imagined place.
Mathematical equations can allow the mathematician to visualize/imagine an arc or a spacial design, as do people imagine the places beyond the human's visual plain.
If there is life within a drop of water, yet this life is invisible to the human eye without the aid of microscopes, why would people suspect life to not exist in the greater spaces yet unfounded?
And if there is life far within, would people suspect the earth itself to simply be a dead rock flying through space?
Is the rest of the universe lifeless mass?