why is sky blue?

Answer 1

The sky is blue due to an effect known as Rayleigh Scattering.

Rayleigh Scattering is, simply put, when light (made of Photons) bounce off of tiny particles. The amount that the photon is scattered is based off of it's wavelength. The longer the wavelength (Red Light), the less a photon is scattered, the shorter the wavelength (Blue Light), the more a photon is scattered.

Rayleigh Scattering takes place when electromagnetic radiation (Light, in the visible spectrum) strikes a particle that is smaller then the wavelength OF the radiation.

This is the mechanism, now for the effect.

Take a single ray of light, passing through the Earth's Atmosphere. It has two possible outcomes:
1)Pass through the atmosphere, and continue on through space.
2)Strike the Earth's surface, and be absorbed.

In either case, as the light travels through the atmosphere, it strikes all the particles suspended in the air. This scatters the Blues, Indigos, and Violets far more then the Reds, Yellows and green. This is also why the sun appears Red/Yellow. The ray of light passing through our atmosphere is now made up of less Blue, making it look more Red.

Our atmosphere is constantly being saturated with scattered blue light. This light is traveling chaotically in every direction, bouncing off of dust and other particles. The reds and yellows are traveling through the air, relatively unimpeded, and either passing out of the atmosphere or being absorbed into the Earth. This results in the sky having far more blue light present, then reds and yellows.

Thus, the sky is blue.

Answer 2

You've asked a classic question and Matt has given you a correct, classic answer. If you are observant, however, you will notice that Matt's answer glosses over the fundamental question: why is blue light scattered more than red in Rayleigh scattering?

Here's a highly simplified explanation: Small atmospheric particles and molecules include electrons which will respond to applied electric fields. Under conditions conducive to Rayleigh scattering, the electric field in incident sunlight will exert a force on these electrons, causing them to oscillate at the frequency of the applied field. An accelerated charge will radiate an electric field which is proportional to the acceleration. Since the charge is oscillating, it has an effective position which varies sinusoidally as sin(Ft) where F is the frequency of the light. Acceleration is the second time derivative of the position, which leads to a factor of F^2 in the amplitude of the radiated field. Radiated power is the square of the field, and therefore varies as F^4. Blue light has a higher F than green or red light, hence the F^4 factor is higher for scattered blue light than for green or red, although there will still be some green and red light scattered. This is what leads to the blue tint of the sky.

Answer 3

The sky is blue partly because air scatters short-wavelength light in preference to longer wavelengths. Where the sunlight is nearly tangent to the Earth's surface, the light's path through the atmosphere is so long that much of the blue and even yellow light is scattered out, leaving the sun rays and the clouds it illuminates red, at sunrise and sunset.

Scattering and absorption are major causes of the attenuation of radiation by the atmosphere. Scattering varies as a function of the ratio of the particle diameter to the wavelength of the radiation. When this ratio is less than about one-tenth, Rayleigh scattering occurs in which the scattering coefficient varies inversely as the fourth power of the wavelength. At larger values of the ratio of particle diameter to wavelength, the scattering varies in a complex fashion described, for spherical particles, by the Mie theory; at a ratio of the order of 10, the laws of geometric optics begin to apply.

Individual gas molecules are too small to scatter light effectively. However, in a gas, the molecules move more or less independently of each-other, unlike in liquids and solids where the density is determined the molecule's sizes. So the densities of gases, such as pure air, are subject to statistical fluctuations. Significant fluctuations are much more common on a small scale. It is mainly these density fluctuations on a small (tens of nanometers) scale that cause the sky to be blue.

Answer 4

It was Einstein who answered this question. It has to do with the way sunlight is scattered by the molecules in the atmosphere. Blue light scatters more than red (Tyndall effect also known as Rayleigh scattering), so more blue light reaches our eye.

There is an excellent description at the website listed below (look at the cartoon and it will be pretty clear).

It is not a reflection from the ocean. And it isn't just water molecules that cause the effect.

Aloha

Answer 5

Matt is correct. Rhythm has a point as well. Next time, search for a question to see whether it has been asked earlier.

Answer 6

its due to the scattering of blue light from white light, because it has the shortest wave length, and hence, it scatters better.

Answer 7

http://answers.yahoo.com/search/search_result;_ylt=AomEMEfWEphOKjPnPtcSXcsezKIX?p=sky+blue

- answered hundreds of times over.

Answer 8

Reflection of the ocean maybe..

Answer 9

dispersion of ligh by particles on the atmosphere.

Answer 10

a airliner