Size and distance are relative. Most of us would agree that 20 miles is a pretty long way to run and 3000 miles is a pretty good distance to travel by plane, train or car. When we start to think in terms of the size of the Earth, we’re getting into some big numbers, but they’re still easily comprehensible as distances to travel. We know we can get to the moon in a fairly short time, but we start to balk at the thought of a year-long journey to Mars. Once we’re out in space, dimensions and distances unfurl and quickly start to span beyond our comprehension.

Our solar system alone is vast enough to leave our heads spinning if we really start to think about it, and when we venture beyond, when we head into the Milky Way and past that into contemplation of the universe, the numbers become too enormous for us to understand. Nevertheless, we can attempt to grasp those sizes and distances by comparing them with sizes and distances right back here on Earth.

What's your thought?