Red Sky

[simonbp]

Here comes the Physics:

The sky on Earth is blue for the same reason the sea is blue: Raleigh scattering, the blue-shifting of light that passes through a fluid. Neither N2 nor O2 nor H20 are inherently blue, but appear that way when light passes long distances through them.

The opposite of Raleigh scattering is Mie scattering, which is the red-shifting of light that passes through dust. The Martian atmosphere appears red because there is large amounts of dust in it.

(As a sidenode, measuring this scattering is how astronomers figure out if a nebula is primarily dust or gas.)

Thus, for the Earth to have a red atmosphere is not impossible, but would require a much dustier planet...

Simon

 

[DMA]

So simon, as a matter of interest, if Earth had a nitrogen-methane atmosphere, instead of the nitrogen-oxygen one we currently have, what would be the colour of the sky?

I ask, because, Titan, which has a nitrogen-methane atmosphere, doesn't have a blue sky, but rather an orange one.

 

[Othniel]

Hapsburg:

I think maybe you were counfusing Nitrous Oxide with Nitric Oxide.

Nitric Oxide is NO.

Nitrous Oxide (laughing gas) is N2O.

I have no idea what N3O is.

To my knowledge, besides Nitric Oxide, the major poisonous gases are Chlorine, Methane, Carbon Monoxide, Carbon Dioxide (in high enough amounts), and Ammonia. Nitrogen and noble gases like Aragon, Neon, etc are safe to breathe at any concentration, provided there is enough oxygen in them.

Edit: There is no easy way to make the sky red, as it is blue due to Rayleigh scattering, which is too complicated to explain quickly here (essentially, transparent air, no matter the components, will scatter light and appear blue). The only ways to change this are either to change the spectra of the sun, add a partially opaque gas like chlorine, or (easiest way) to have tons and tons of dust and other particulate matter in the atmosphere.

Mars' atmosphere is actually not pink, BTW, unless there is a dust-storm. It's basically as blue as Earth's.

Nitrate. N(subspcirpt 3) O or is it NO(subcript 3) is nitrate.

 

[csa945]

Nitrate is NO3, but nitrate is actually a substrate, not a compound. Alone it has a negative one charge, so it usually ends up bonding to a metal like Lithium, Sodium, or Potassium.

N3O doesn't exist.

 

[Othniel]

Nitrate is NO3, but nitrate is actually a substrate, not a compound. Alone it has a negative one charge, so it usually ends up bonding to a metal like Lithium, Sodium, or Potassium.

Iron, ...ect.

 

[csa945]

Actually, iron would be pretty tough, as it doesn't form a 1+ ion naturally. I think that most nitrate compounds only form with the Alkali Metals, the first group.

 

[Othniel]

You've never heard of Iron Nitrate? It's common compound, allow getting it is far more complex than that.

 

[csa945]

Oops. I didn't type in the nine water molecules on my chem formula search site. You'll have to forgive me. It's been a year since I finished general chem. I've been immersed in nothing but carbon compounds all year.

 

[Othniel]

Oops. I didn't type in the nine water molecules on my chem formula search site. You'll have to forgive me. It's been a year since I finished general chem. I've been immersed in nothing but carbon compounds all year.

Ah...combustibles....and life forms. Chem was my favorite subject while in high school, maybe I should go to colledge and take a bit more chemistry.

 

[simonbp]

Hi Othniel,

Titan's atmosphere is 90% N2, and the rest is various hydrocarbons. These hydrocarbons are clumpy enough to Mie scatter, but not enough to make a very red atmosphere like Mars, and thus the colour in between red and blue, yellow...

BTW, Titan's atmosphere is 10 denser than Earth and has a surface pressure of 60 atm (882 psi), only Venus is worse...

Simon

 

[eschaton]

Are you sure it's 10 times denser than Earth? I've always heard it's like 1.5 times as dense in my astronomy books.

 

[Straha]

a green sky IMO is VERY plausible and will probably happen sometime in the future when genetics becomes more advanced. All that would need to happen is a type of algae that floats in the high atmosphere and we'd get a sky thats green

 

[Hierophant]

Doesnt red influence people to violence? Would everyone be more violent?

 

[csa945]

Doesnt red influence people to violence?

Hunger, too. That's why so many fast food restaurants have red and yellow logos.

 

[FederationX]

Hunger, too. That's why so many fast food restaurants have red and yellow logos.

I'd be addicted to fast food 24/7. Start's ctying

 

[Ivan Druzhkov]

Okay, I'm not an expert on the subject, but couldn't we get a red sky if our atmosphere was a lot thicker? From what little I remember of grade-school science, during dawn and dusk the way the planet is angled to the sun means that the light has to travel through a lot more of our atmosphere than during noontime, thus scattering more of the light, allowing the red spectrum to come through.

Or am I full of it?

 

[Musketeer513]

Answers

The atmosphere of Titan is 10 times thicker than Earth's but with the lesser gravity it compresses to 1.5 times Earth's. Now we can not increase te amount of Nitrogen in the atmosphere to much. If the percentage of Oxygen goes under 15% you can not have an open fire. The best we can hope for is to increase the Nitrogen amount to 4 times current. You can increase the amount of Oygen to 5 times it's current amount. That gives you an atmosphere more than 4 times thicker than normal an Oxygen percentage of 25 and a Nitrogen of 75%. This is thick enough to change the color of the sky but I'm not sure if it would be read.