The butterfly effect

Taking advantage of the opportunity to wander outside without the precaution of donning wellies, coat and snorkel this weekend, I made the most of the unexpected good weather by lounging in the garden and monitoring the conflict between torpor and my desire for a cold beer.

As afternoon turns into evening, somebody at a flight control desk somewhere flips a switch and, thanks to a change in flight plans and runway approaches, or possibly just for variety, the patch of sky over my head is filled not just with darting swifts but with the occasional jet aeroplane, toiling across the blue.

The appearance of these jets is always preceded or followed by a gentle wind of passing. This is not, I am sure, imagination - hot weather means that I have perfected the art of sitting perfectly still. When a 747 goes past, I can see the effect of the wind as well as feel it myself.

It makes you wonder what violence is being done to the air so that something so far away (luckily they are always high by the time they pass) can have such an effect.