why isn't the sky purple?

Answer 1

This is a gpood question, and makes a variation on the usually asked "why is the sky blue?" (asked over 5000 times).

The short wavelengths of light are scattered more by the atmosphere than the red and yellow, so we see the sky as blue (explanation in detail below). Violet wavelengths are even shorter than blue, and are scattered more. The reason we don't see the sky as violet is that our eyes are much less sensitive to the violet wavelength than to the blue, so we see the blue colour more. In addition, the blue wavelengths make up a larger proportion of the sunlight spectrum.

As to the question of why the sky is blue, the following is a standard amswer I've prepared to this question:

This question has been asked over 5000 times, and I've prepared a simple answer, without too much science:

The correct answer is that the blue light is scattered by the air molecules in the atmosphere (referred to as Rayleigh scattering). The blue wavelength is scattered more, because the scatteing effect increases with the inverse of the fourth power of the incident wavelength.
OK, but I've known science graduates who don't understand what this means.
Here's my attempt at an answer without too much physics:

I think most people know that sunlight is made up of light of several different wavelengths, and can be split up into the colours of the rainbow. Blue light has the shorter wavelength, and red the longest wavelength.

When sunlight hits the molecules in the atmosphere, the light strikes the molecules and is absorbed. The molecules vibrate and and give off, or 're-emit' the light. Because the molecules vibrate in all directions, the light is emitted in all directions (called 'scattering'). The molecules in the air are much smaller than the wavelength of visible light, but because the blue wavelength is shorter and more energetic, it reacts much more with the air molecules than the red and yellow wavelengths; which tend to pass straight through.

Because the blue radiation is re-emitted from the air molecules in all directions, it seems to us looking from the ground that the blue light is coming from everywhere; hence the sky seems blue.

Near sunset, because of the low angle of the sunlight, we see more of the red and yellow wavelendth passing straight through, hence the colours of the setting sun.

BTW: The sky isn't blue because of a reflection of the sea; its the other way round, The blue colour of the sea is a little more complicated, because as well as the water molecules scattering the blue light, the water absorbs more of the red and yellow wavelengths, leaving the blue part of the spectrum, as well as part of the green (which is why deep water can appear bluish-green). This effect is even stronger with ice; which results in the intense blue colour we see if we look down a crevasse in a glacier, or down a hole in the snow made by a ski stock..
My thanks to varoius contributers for correcting me on some details.

For a complete, scientific explqanation, look up 'blue sky' in Wikipedia.

Answer 2

This Site Might Help You.

RE:
why isn't the sky purple?

Answer 3

Because the atmosphere soaks in the purple/violet light

Answer 4

The sky is blue because light waves of that length are scattered while longer go straight. Red is longer. Red plus blue are needed to make purple.

Answer 5

the light from the sun isn't hitting the atmosphere at the right angle..

Answer 6

the light that comes into our atmophere is bending, and only picks up the blue in the spectrum .if it were on a slightly different angle you would get another color but would it be purple??? Idk about that but it would be pretty :)

Answer 7

Yup. I'm with the favorite color thing. Sa gusto nya eh, bawal?

Answer 8

Because the ocean isn't purple and the sky gets its color from the reflection from all of the blue water that covers our planet.

Answer 9

Because then it wouldnt match my eyes.

Answer 10

cause then it would lok like someone punched god in the face.