Why could lightning look purple?

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Why could lightning look purple?
« on: 17/08/2009 10:30:04 »
Katie asked the Naked Scientists:
Dear Naked Scientists,

I was just standing on my balcony observing this amazing rain storm with thunder & lightning and the lightning was bright purple.

Was that just an illusion or has it something to do with my visual system or my perception or can lightning actually be purple?

Thanks a lot from Germany, Katie

What do you think?


Offline carreerslut

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Why could lightning look purple?
« Reply #1 on: 17/08/2009 12:23:27 »
First will ask the obvious.  You sure it wasn't an after image?  Eg you saw some bright streak of lightening, then saw it repeated as a fabricated version of overstimulated neurons in the eyes causing the illusion of the opposite colour to what you saw.  Just the first thing that came to mind, expressed terribly, but the optical scientists here will tidy the physiology side up hopefully.


Offline Chemistry4me

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Why could lightning look purple?
« Reply #2 on: 18/08/2009 06:09:14 »
Well it sort of looks purple anyway


Who gives a flying

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Why could lightning look purple?
« Reply #3 on: 18/08/2009 20:53:15 »
Lightning comes in a variety of colours; purple; blue; white; red; green and more. There are a few theories put forward as to the cause of the colour. The ones that most people agree on are:

blue lightning is a sign of hail within the cloud. white lightning occurs in dry conditions. Yellow lightning is caused by dust particles. Red lightning is seen mainly during intense rainfall.

So the colour of lightning is caused by the way lightning intereacts with atmospheric gas, dust and water molecules. The distance the observer is to the lightning is also a factor.. It is also possible for one single lightning stroke to produce more than one colour.

For a better and more indepth explanation you may want to try this link:

There is a nice graphic at this link: