Pale blue dot
September 22, 2011 22 Comments
Some time on Friday evening (GMT), the defunct UARS satellite is going to fall to earth. Six tons of blistering, white-hot metal are going to splatter the lower atmosphere and the larger chunks will strike the surface at horrendous speeds.
NASA tells us that there’s only a one in 3,200 chance of any of us being hit, and since there are seven billion of us, I don’t think it’s going to be me.
But out of idle curiosity I thought I’d look up how much of the Earth’s surface is actually occupied by humans. I had to do it by subtraction, from various sources within that amazing oracle of truthiness that is the interwebnet.
I could dismiss 70% of the planet immediately, since everyone agrees that this much of it is ocean. How much is jungle or forest? About one third of the total surface of the earth, apparently. And Wikipedia tells me that one third of the land surface is desert. One third of the 30% that is not ocean works out as 10% of the total surface. I figure deserts don’t contain forests, and oceans contain neither (the polar cap isn’t included in the figure for deserts) so these are mutually exclusive areas. Whatever is left is habitable space.
Okay, so 100% – 70% – 33% – 10% = negative 13%. Hmm. Maybe I need to double-check the figures.
Either way, allowing a decent margin for error, I have to conclude that, at the most optimistic estimate, humans occupy roughly zero percent of the planet, give or take a little. Given that there are an awful lot of us anyway, this means we must be spread out like a spider’s web clinging to a beachball.
Well, maybe not a beachball. If Jupiter is a beachball, Earth is a marble, lost in an emptiness so huge that we’re a barely discernable, sizeless dot in the Jovian night sky. And the star we orbit is just one of two hundred billion in our galaxy alone, and there are about a hundred billion galaxies in the observable universe.
I lost my bike helmet yesterday. It doesn’t seem so important any more.
[Edit: whoops. Corrected the math. D minus.]