© 2003 David Drysdale

Now that we've just had Diwali and Guy Fawke's night, I was reminded of why I've gone off fireworks in recent years.

A few years ago I had friends round to my house, and we set off fireworks in my back garden.

(This was also the year with the famous sparklers-in-a-power-drill experiment, to which both Mike and I claim origination.)

One particular firework that we set off was a Catherine Wheel, nailed to my shed. For those who've not encountered this, it's a circular firework that you nail to something solid, and when it's lit it spins around casting off flames and sparks and suchlike.

This particular Catherine Wheel seemed to be a particularly bright example of the genre. Once it had finished spinning, I was left with an glowing circular afterimage on my eyes from looking at it too directly. You know, that sort of yellow-red-purple afterimage you get for a moment or too, even with your eyes shut.

Except in this particular instance, when I closed my eyes the circular afterimage did go away. And when I moved my eyes around, the position of the afterimage didn't stay fixed at the same place in my visual field—it seemed to stay in the same place in the garden.

Ah, so that'll not actually be a visual afterimage then.

That'll actually be my shed on fire.