Lerwick would be a great place to see the Northern Lights but clearly not on a sunny summer afternoon. The hare will have to do! I looked up the source of the different colours. The green comes from electron jumps between energy levels in atomic oxygen. I have to think about that. Not molecular O2 but high enough up in the atmosphere for the bonds holding the molecules together to be broken by high energy radiation from space and individual oxygen atoms to be loose. The blues and purples come from molecular nitrogen lower down. Maybe one day I'll be lucky enough to see it for myself.
