Measures of the world

What are the different ways we can measure the size of the world?

There's the earth's diameter. Another measure is its surface area. That might be more meaningful to us, since our lives are played out on its surface. You could even just measure the amount of land, ignoring the water. Or limit the measurement to the amount of habitated or habitable land (according to some reasonable definitions of habitated and habitable).

Another thing we could ask is: how big is the world each of us has seen? How large an area have you actually seen with your own eyes, during your lifetime? For most of us, it's only a small fragment.

Though we may have only seen a fragment of it, our conception of the the world is much broader, because it also takes in details that we know secondhand, through conversations, books, television, etc.

This conception is subjective, and infused with personal and social details. The place I went to school. The path I take to get to the train station. Where my best friend lives. Those streets in the city where it doesn't feel safe to walk alone at night.

In my conception of the world, the unit where I live is sketched out in detail. But to the person down the road who only knows it from walking past it from time to time, it's little more than a facade made up of what's visble from the road.

Because of these personal and subjective details, this mental conception of the world, though only dealing with small portions of the world in detail, is -- in this sense -- richer than the physical world.

There's another kind of measure of the size of the world. Though the physical world is large and these mental worlds small, there is only one physical world, and billions of mental ones. And the total area and details covered by that billion-piece mozaic is large indeed.