Today, suddenly, it's 10 degrees colder than yesterday, and my knuckles were numb when I parked my bike in front of work. The sky is a very demanding blue. I say demanding because it divides us into two worlds - the underworld full of stone buildings full of office workers full of coffee, and the overworld of space, full of birds at first, then ozone, then nothing, then stars. It reminds you how limited your perspective is. It's demanding because it forces you to acknowledge that there's a well of emptiness right above your head, and it has a colour. The colour is the most disturbing part. Anyone can understand a black void, but a blue void is a weird and unreasonable concept.

When I do Yoga outside in the park in the summer, when I go into a headstand, I like to imagine that it's not me that's upside-down, but the world. I got the idea from Dharma Bums by Jack Kerouac. I imagine that we are all on the underside of a sphere hanging in - no, hurtling through - space. I imagine that we are all stuck on the bottom of the sphere by some strange force. We say that we are looking up into the sky, but that's just to make ourselves feel better, because really we are looking down into the void. Gazing into the abyss. I don't find this depressing. In fact, once it made me giggle so much I fell out of my headstand and nearly broke my neck. Everyone was beetling along minding their own business, pointedly ignoring the blue abyss. It was like a scene out of The Hitch Hiker's Guide to the Galaxy.

There's a man across the road in a long duffle coat and suit, standing in front of an office building, talking on a cellular phone held between his chin and his shoulder, tapping on his palm pilot. Maybe because the palm pilot screen is blue and unreflective he doesn't notice how blue the sky is, or the danger he's in - at any moment he could fall off the planet and go careening into the blue, scarf fluttering madly, and no one would say anything. It might be like Toy Story - The Claw! The Claw! He has been chosen!.

The sky is demanding. That would liven up my day.