why is the sky blue?

Answer 1

The sky is blue because of a phenomenon called Rayleigh scattering, which basically means that shorter-wavelength light is preferentially scattered by the air in the atmosphere compared to longer wavelength light. Imagine you're looking up at the sky. All light is coming from the sun; some directly at you, some to other parts of the earth. The light coming from the sun will be strong enough that scattering is not an issue; it will look white. Now look away from the sun, to the blue sky. If there were no atmosphere, you would *not see any light that was not coming at you directly* and the sky would appear black - it's only because the atmosphere scatters light that it is visible to you. Since shorter-wavelength (bluer) light is scattered more than longer-wavelength (redder) light, the sky is blue. Actually, this means the sky should be violet or purple, but since our eyes are more attuned to seeing red & blue and are pretty bad at seeing purples, the sky looks blue (that is, slightly to the red of violet on the color spectrum).

This phenomenon has led some conspiracy theorists to complain that pictures of the Martian sky are false-colored, as they should also be blue for the same reasons. The standard explanation for the pinkish/salmon Mars sky is that there is a lot of iron-rich dust in the atmosphere. Personally, I hope the blue sky conspiracy theorists are correct. How neat is that, a blue sky on Mars?

Answer 2

The visible wavelengths of light are bent and separated by the earth's atmosphere. We see blue because what gets to our eyes from the sunlight coming through the atmosphere is all sorts of neat combinations of colors of reds and greens blues.

Think about it this way (this will also explain red skies at night):

If you stand on one side of a forest and play a bunch of instruments at once (say, a flute, a saxophone, and a tuba), what will get to a listener on the other side of the forest will be the tuba and the saxophone. This is because the trees absorb the energy of all of the sound waves made by the instruments. But the flute, even if it's just as loud as the tuba, has a shorter wavelength of sound (meaning it sounds higher). Shorter-wavelength things get interfered with more easily than longer-wavelength things.

If you have a shorter forest between you and your friend, some of the flute will get through.

If you have a longer forest, less of the saxophone, and none of the flute, will get through.

Now, think of light like musical instruments. Remember ROY G BIV, the spectrum? Well, red is the lowest wavelength, so it's like the tuba. The saxophone is G, and the flute is B. We'll have the piccolo be IV, but nobody likes them, so they're out of the story pretty quick. Next paragraph, in fact.

The atmosphere (forest) absorbs the highest-wavelength light (the IV). We see what's left, the combinations of the ROYGB, which looks blue to us.

And, at night, when the sun is lower on the horizon and has to pass through more of the atmosphere to reach our eyes, the atmosphere absorbs the saxophone, too, leaving us with just the Red, Orange, and Yellow tuba.

Answer 3

Light contains many colors, each one has a frequency. The atmosphere absorbs most of the frequencies, leaving blue as the most frequently seen color.

The atmosphere contains water vapor and other gases, along with particulate matter, such as dust and carbon monoxide emissions from vehicles and other fossil fuel burners.

In an area with high water vapor and relatively warm temperatures, such as the San Francisco Bay area, the moisture content which is sometimes referred to as haze, absorbs the deeper blue spectrum as well. The sky appears to be light blue, or even grayish white, depending on the conditions.

Deep blue sky occurs in dry weather, at higher altitudes and in pollution free environments. Pollution and particulate matter usually put a yellowish cast to the sky's color.

Answer 4

Light coming from the sun is what's called "white light" White light contains all the colors of the rainbow. When it enters Earth's atmosphere this light is separated into its individual colors by chemical elements in the atmosphere and scattered across the sky. Nitrogen is the most abundant element in our atmosphere, and that element scatters the color blue across our sky more than the other colors. In space, there is no atmosphere to separate colors from the white light and space looks black.

Answer 5

This is related to the Physics of Light. Light has different color components. The Red part has longer wavelength than the Blue component. It so happens that the longer wavelengths get dispersed more in the atmosphere, so Red gets dispersed more and what you see is the Blue part.

Nutshell: Red part gets dispersed more, so what REMAINS has more of blue and that is what you see in the sky.

Answer 6

I thought you asked what is sky blue, and I was going to say an alcholic drink.


The sky is blue because of the reflection off the water into the atomosphere, and the water is blue beause of the reflection of the sky into the water.

Answer 7

I'm not so sure- seriously, but I think it's ultraviolet rays in space bouncing off the sun to earth. Maybe the reason that bodies of water appear somewhat blue.

Answer 8

difficult to explain,but amounts to combination of things entering the eye bouncing off the retina and being perceived as sky blue.

Answer 9

the sky's blue because the atmosphere absorbs all the colour VIBGYOR absorbs all colours except blue.

Answer 10

Because if it was green, we wouldn't know when to stop mowing the lawn.


If you were serious, reflection (maybe refraction, don't remember) of light off water vapor as someone else said.