Lightning & thunder
This page was created on 9 August 2008, and
last modified on 10 February 2011.
During a short but fierce electrical storm over east Berkshire on 27
July 2008, I stood at an open window and took some video-clips with my Canon PowerShot S2 camera. I
was fortunate enough to record this exciting sequence—described
through the frame-captures below—and the accompanying sound-effect.
The six photographs below are consecutive frames from the video-clip.
The camera took frames at a rate of one per one-thirtieth of a
Above: The sky is dark before the
Above: A partial upstroke appears to be
originating from just a few yards away, but (luckily for me!) the main
bolt did not end up striking here in consequence.
Above: The whole sky is now fantastically
bright white, possibly as the cloud immediately above reflects numerous
upstrokes or inter-cloud strokes; individual raindrops can be seen lit by
the flash against the darker backdrops of the nearby buildings and
Above: This is the classic “forked
lightning” as the electrical potential between cloud and
ground reaches the critical point and an ionized path through the air is
Above: The downstroke now
travels between cloud and ground, following the ionized path which had
just been “found” by the forked lightning. This is the
actual lightning-bolt running to earth, and as can be seen by its
brightness and thickness, it is carrying a huge current: it is this part
(and not that depicted in the previous three frames) which kills people
outright, sets fire to cathedrals, blows trees to pieces, et cetera.
Above: Another 1⁄30 second later, the sky is dark and all is quiet…
until, of course, the thunder-clap!
Approximately 2.2 seconds later came the start of the thunder-clap,
which was of the type we like to refer to as sheds, because it
resembles the noise we like to assume would be made by a load of wooden
sheds being demolished! My camera was recording sound at CD-quality
(44.1 kHz) but its tiny microphones and automatic recording-level mean
that the result isn’t as spectacular as it should be, through a
drastic reduction in dynamic range. Still, you should get the idea:
The rain really was just getting started as this clip progressed.
I don’t claim to know a great deal about the electrical
phenomena described here, and so particularly welcome any corrections or