Science Questions

On many different occasions, I've noticed that in a thunder storm the lightning can be pastel blue or yellow or even green or pink. My question is why does the colour vary from one storm to another? Anthony in Essex

That's a 64 000 dollar question, that one! I'm not confident about this but it's probably to do with the amount of energy that's discharged from the bottom of the cloud. They'll be going through slightly different raindrops. The colour that you're seeing will also be dictated by the chemical behaviour of the things that get ionised or heated up by the lightning. So if there's contamination in the atmosphere, perhaps that could play a role. Street lights are orange because they contain sodium. If you heat sodium up to a very high level, the wavelength of light that you emit is an orange colour. Perhaps there are certain things in the air at that time that can affect the colour of the discharge.

April 2006