What is the experimental prosdure of "Why is the Sky Blue??"?

Question

I need this for a science project && I looked everywhere but cant find he answer!

Answer 1

first of all, to Paranoid Princess:



whoa, whoa WHOA. just a minute. the sky is not blue because there's liquid oxygen in the upper atmosphere. that's just retarded and you shouldn't go presenting bizzare mis-truths as fact when they *aren't* fact.



here is a profile of temperatures at various altitudes:

http://www.windows.ucar.edu/tour/link=/earth/images/profile_jpg_image.html

as you can clearly see the lowest temperature is about -100C. oxygen liquefies at -182C at normal pressures (reference: http://www.ucc.ie/ucc/depts/chem/dolchem/html/elem/elem008.html ), and even lower temperatures at the low pressures in the upper atmosphere. PLEASE don't present some bizarre fiction as truth to someone who isn't well-informed enough to know that you're simply fabricating nonsense from thin air. if you have simply been misled by someone else, at least try to do a marginal amount of research before answering a question on something you don't know much about.



that said, to the original asker:



the sky is blue because of a phenomenon called "rayleigh scattering", which occurs because the molecules of air (mostly N2 and O2) happen to be the right size to scatter blue light in all directions. some of this blue light reaches your eye after being re-scattered again by a second molecule, sometimes all the way across the sky.



this is also why the sky turns red at sunset - at low angles, the sunlight has to travel a longer distance through the atmosphere, and by the time it reaches your eye, a lot of the blue light has already been scattered away, leaving yellow orange and red. (i have yet to hear any explanation of why the sky doesn't turn green between daytime and sunset, though. still tryin' to figure that one out.)



anyway here are some home/school experiments designed to illustrate rayleigh scattering:

http://www.physics.brown.edu/physics/demopages/Demo/optics/demo/6f4010.htm

http://www.chaosscience.org.uk/dem/public_html/article.php?story=20050222224622239

http://teachers.web.cern.ch/teachers/archiv/HST2002/smallexp/krug/Rayleigh.htm

http://bulldog2.redlands.edu/facultyfolder/deweerd/research/scattering-AJP.pdf

http://www.ktca.org/newtons/9/sky.html



also, a nice page illustrating rayleigh scattering:

http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html

and a slightly more advanced version:

http://world.std.com/~mmcirvin/bluesky.html

Answer 2

Since there seem to be SOOO MANY people who don't understand why the sky is blue, as well as some really bizarre ideas on why it is blue, I applaud your efforts to PROVE once and for all, that there is a scientific explanation.



What you need to look for is information on Rayleigh scattering. Hyperphysccs website has a good diagram:http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html

On the lower part of the page they show how they measured the change in blue using Adobe photoshop. This would be interesting if you have access to photoshop software. Go through all their atmospheric optics pages. It's good stuff.



Then go here and you will find a procedure that you can use to demonstrate Rayleigh waves.

http://www.sciencemadesimple.net/sky_blue.html

Get a digital camera and record your results.



See if you can make some quantifiable measurements of the light's refraction. You can use a screen to project the light onto with measuring bars. Then vary the amount of the particles in the glass and see how it changes.

Be creative, try to get an analyzable result, have fun!

Answer 3

The simlpe answer is that blue light scatters more than any visible color in Earth atmosphere. That is you start. You need to write your experimental procedure.



The long answer:

When you look at the sky at night, it is black, with the stars and the moon forming points of light on that black background. So why is it that, during the day, the sky does not remain black with the sun acting as another point of light? Why does the daytime sky turn a bright blue and the stars disappear?



The first thing to recognize is that the sun is an extremely bright source of light -- much brighter than the moon. The second thing to recognize is that the atoms of nitrogen and oxygen in the atmosphere have an effect on the sunlight that passes through them.



There is a physical phenomenon called Rayleigh scattering that causes light to scatter when it passes through particles that have a diameter one-tenth that of the wavelength (color) of the light. Sunlight is made up of all different colors of light, but because of the elements in the atmosphere the color blue is scattered much more efficiently than the other colors.



So when you look at the sky on a clear day, you can see the sun as a bright disk. 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.)



here is a link to help you

http://science.howstuffworks.com/framed.htm?parent=question39.htm&url=http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html

Answer 4

The Earth's sky is blue because the air molecules (largely nitrogen

and oxygen) are much smaller than the wavelength of light. When light

encounters particles much smaller than its wavelength, the scattered

intensity is inversely proportional to the 4'th power of the

wavelength. This is called "Rayleigh scattering," and it means that

half the wavelength is scattered with 2**4 = 16 times more intensity.

That's why the sky appears blue: the blue light is scattered some 16

times more strongly than the red light. Rayleigh scattering is also

the reason why the setting Sun appears red: the blue light has been

scattered away from the direct sunlight.



Thus, if the atmosphere of another planet is composed of a transparent

gas or gases whose molecules are much smaller than the wavelength of

light, we would, in general, also expect the sky on that planet to

have a blue color.



If you want another color of the sky, you need bigger particles in the

air. You need something bigger than molecules in the air---dust.



Dust particles can be many times larger than air molecules but still

small enough to not fall out to the ground. If the dust particles are

much larger than the wavelength of light, the scattered light will be

neutral in color (i.e., white or gray)---this also happens in clouds

here on Earth, which consist of water droplets. If the dust particles

are of approximately the same size as the wavelength of light, the

situation gets complex, and all sorts of interesting scattering

phenomena may happen. This happens here on Earth from time to time,

particularly in desert areas, where the sky may appear white, brown,

or some other color. Dust is also responsible for the pinkish sky on

Mars, as seen in the photographs returned from the Viking landers.



If the atmosphere contains lots of dust, the direct light from the Sun

or Moon may occasionally get some quite unusual color. Sometimes,

green and blue moons have been reported. These phenomena are quite

rare though---they happen only "once in a blue moon...." :) The dust

responsible for these unusual color phenomena is most often volcanic

in origin. When El Chicon erupted in 1982, this caused unusually

strongly colored sunsets in equatorial areas for more than one year.

The much bigger volcanic explosion at Krakatoa, some 110 years ago,

caused green and blue moons worldwide for a few years.



One possible exception to the above discussion is if the clouds on the

planet are composed of a strongly colored chemical. This might occur

on Jupiter, where the clouds are thought to contain sulfur, phosphorus,

and/or various organic chemicals.



It's also worth pointing out that the light of the planet's primary is

quite insignificant. Our eyes are highly adaptable to the dominating

illumination and perceive it as "white," within a quite wide range of

possible colors. During daytime, we perceive the light from the Sun

(6000 K) as white, and at night we perceive the light from our

incandescent lamps (2800 K, like a late, cool M star) as white. Only

if we put these two lights side-by-side, at comparable intensities,

will we perceive a clear color difference.



If the Sun was a hot star (say of spectral type B), it's likely we

still would perceive its light as "white" and the sky's color as blue

Answer 5

Well, to first answer the question of "why is the sky blue?", the answer is that the sky is blue because of oxygen. If you take the same oxygen that everyone is breathing right now and freeze it until it changes from a gas to a liquid, it what you would get would be the same shade of blue as the sky is. As oxygen warms up and changes from a liquid back into a gas, the blueness gives way to a white mist, identical to the mist that emits from dry ice.

As far as the experimental procedure for changing the state of oxygen from a gas to a liquid state, while I've never done it, you can find the exact instructions as to how this is done. I should warn you though, if you do decide to make liquid oxygen, it is extremely flammable. To understand what exactly you'd be handling if you decide to liquefy oxygen to show that it's what makes the sky blue, type in "liquid oxygen explosions" into an internet search engine.

Whatever you do, be careful. As far as the full answer to why the sky is blue, you have to keep in mind that way up in the atmosphere, it is extremely cold. Cold enough to cause oxygen to change from a gas to a liquid state. Clouds are also make of oxygen, too. As it descends in the atmosphere, it warms up and changes from a liquid back into a gas again. As the oxygen warms up as it descends, it changes from a liquid to a white colored vapor, and finally, to a colorless gas.

Remember that oxygen is only colorless when it is in the gas state.

Answer 6

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