Blue sky?

[mr_doubtfire]

Okay. The sky's blue because the light from our sun collides with the oxygen and nitrogen atoms, colours with shorter wavelengths are scattered more (violet and blue) our eyes are more perceptible to blue light so we perceive the sky to be blue. So here are my questions. What if our sun was a red giant or a white dwarf, would we still have a blue sky? And, what would the atmosphere have to contain for our sky to have a light green colour (research for my third novel. More so, would it be breathable?). If I get clear and concise answers you'll get an acknowledgement.
Cheers Mr_D

[beso]

In the case of a red giant there would be no blue wavelengths in the incident radiation so the original colour would be dimmed.

Both white dwarfs and red giants are stars nearing the end of their life. These stages are short compared to the main sequence stars. Consequently the life on any planet around them would have evolved during the main sequence and then have to deal with the change.

Our Sun will go through a red giant phase and expand beyond our orbit. So life surviving a red giant phase is problematic.

However, long before this the Earth will have been boiled dry because stars get hotter as they progress through the main sequence. Within one billion years the Sun will be so hot that the Earth would need to be at the orbit of Mars to maintain life as we know it.

[mr_doubtfire]

Right, I'm with you so far. But hypo(fantasy novel)thetically speaking, what would the atmosphere need to consist of to give the sky a light green colour? Assuming the sun was a yellow one. Mr_D

[ChuckFickens]

Oxygen will create a green light/sky in aurorae conditions, so I'd explain it in a book sense as an oxygen rich atmosphere (unless you have a reason for not wanting an oxygen atmosphere?) that is being hit by a lot lot more charged particles from a much stronger solar wind.

[Teddio]

A Red Giant, such as Betelgeuse, would have a spectrum similar to that of a tungsten-filament car headlight. If our Sun were replaced by a Red Giant star it would look blindingly bright and not red at all. It is a fallacy to thimk of a Red Giant looking like a setting sun, it wouldn't. The sky would still look blue because there would still be a strong blue component in the spectrum. Of course a Red Giant at the same distance as our Sun would be the size of a football at the end of your nose, and there would be little likelyhood of Earth's atmosphere remaining.

[heathfield]

http://www.dailymail....-light-night-sky.html

[mr_doubtfire]

Cheers, Chuck. That's the answer I was looking for. The novel's in it's early stages yet and, if my publisher accepts it, I'll make sure your noted in the acknowledgements. I'll keep you posted. Mr. D.

[scotman]

I will look out for an attribution or acknowledgement in a book to one 'ChuckFickens'