The human mind isn't really built to grasp astronomical scales. Even the solar system is hard to fathom, and while we have probably all heard comparisons involving football fields and marbles, you really need to see a scale model for it to start making sense.

For me it was always hard to make sense of the distances between the outer planets. Saturn is twice the distance from the sun as Jupiter, Uranus is twice that distance, and Neptune still further. The inner planets may as well be right next to each other on that sort of scale.