Why is the sky blue?

Question

I need the scientific answer for my school project

Answer 1

This is one of the most popular Yahoo questions, asked over 450 times. Here is my standard answer:

The correct answer is that the blue light is scattered by the air molecules in the atmosphere (referred to as Rayleigh scatteringt); and that the blue light is scattered more, because the scatteing varies with the inverse of the fourth power of the incident wavelength. OK, but I've known science graduates who don't understand this.
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 gets bounced around by the molecules (what actually happens is that the light strikes the molecules and is absorbed, causing the molecules to vibrate and give off, or 're-emit' the lightt; but 'bounce around' is close enough).

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 ('scattered'), 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, although the blue colour of the sea is also caused by the water molecules scattering the blue light. This effect is even stronger with ice, which results in the intense blue colour, if we look down a crevasse in a glacier.

Answer 2

The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.

However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.

Answer 3

this question actually showed up on a sixth grade test.
Many people take the sky to be blue because of the sea, but it's actually the opposite.
The sun's light wavelengths differ. red light has the shortest wavelengths and blue has the longest, actually, its violet, but you cant really see the violet, it gets caught and absorbed mostly by the atmosphere's clouds and gases. when the sun's rays reach the earth, you can see blue because the red quickly scatters leaving the blue light behind to shine.
when the sun sets, the sun shines at a different angle causing the red light to be reflected and making the sunset red.

Answer 4

A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colours because the blue light has been scattered out and away from the line of sight.

The blueness you see everywhere else is all of the atoms in the atmosphere scattering blue light toward you. (Because red light, yellow light, green light and the other colors aren't scattered nearly as well, you see the sky as blue.)

Answer 5

air particles reflect blue light. something about the atmosphere filters out all the other colors in light, so only the blue is seen to us.

Answer 6

...really, it's "black" but because of our atmosphere and the moisture in the air etc. etc. the light that is coming in from the Sun goes thru all that "stuff" and like a light thru a glass prism, it appears "blue" from down here on the planet.

Answer 7

check these link n find for urself..
http://www.sciencemadesimple.com/sky_blue.html
http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html
http://acept.asu.edu/PiN/act/sky/sky.shtml
http://www.why-is-the-sky-blue.tv/why-is-the-sky-blue.htm
http://world.std.com/~mmcirvin/bluesky.html


do rate if it helped