The question is that: If you see that pictures taken from satellites of the earth planet, you can see that the color
of the water on that pictures is blue. I was wandering:
Could the reason be that it reflects the blue color of the sky?
The ocean is blue is due to the absorption and scattering of light. The blue wavelengths of light are scattered, similar to the scattering of blue light in the sky but absorption is a much larger factor than scattering for the clear ocean water. In water, absorption is strong in the red and weak in the blue, thus red light is absorbed quickly in the ocean leaving blue. Almost all sunlight that enters the ocean is absorbed, except very close to the coast. The red, yellow, and green wavelengths of sunlight are absorbed by water molecules in the ocean. When sunlight hits the ocean, some of the light is reflected back directly but most of it penetrates the ocean surface and interacts with the water molecules that it encounters. The red, orange, yellow, and green wavelengths of light are absorbed so that the remaining light we see is composed of the shorter wavelength blues and violets.
In short terms, the colors we see on everything is due to the light reflected off of them. Certain colors are absorbed, while others are reflected. The colors that are reflected are the colors visible to us.
What he said... and the sky is blue for the same reason; it's the water molecules in the air causing the blue, along with reflected water from large bodies of water. It's all about absorption and refraction.
Well actually, the water where I live is green. 
Also, there are red patches in the ocean a couple hundred feet away from the shore. (Algae bloom, anyone?) Cool query,From my childhood i had doubt on this question.In our school one scientist had come.I had asked him about this.He gave me different answers like because sky is blue water is blue.Because water contains algae and green stuff.But still i and he had debate kind of thing.So that time i was not satisfied.
Still i have not got any perfect answer for this.Everyone gives me such answers.But i think it is due to color illusion and striking.Both due to color of sky and Vegetation inside water.Still some expeditions are going on lets see what new thing comes.
Cddhesh: | Quote: |
| But i think it is due to color illusion a |
What do you call "color illusion"? it has to do with the depth because the molecules reflect the blue frequencies of the visible light spectrum.
^I don't think it is so much that the water reflects only blue light, it is that the water absorbs all light except blue light (and blue light too, eventually). Any diver can confirm this, the deeper you go, the less colors there are, until the only color is blue, and eventually that goes away to nothing but black. If you turn on a light down in the all-blue zone, though, you can see all the colors.
| ocalhoun wrote: |
| ^I don't think it is so much that the water reflects only blue light, it is that the water absorbs all light except blue light (and blue light too, eventually). Any diver can confirm this, the deeper you go, the less colors there are, until the only color is blue, and eventually that goes away to nothing but black. If you turn on a light down in the all-blue zone, though, you can see all the colors. |
Water absorbing all colors except blue goes hand in hand with water reflecting only blue light =/ They're kind of dependent on each other. The colors absorbed are not visible, the color reflected is the color you see. Both aspects are equally important to the answer.because the sky is blue. it gets the color from reflection from the sky or something like that
than why sky is blue?... why the pyramid of world reflects sun light blue.
Am slightly worried by the people suggesting that the sky is blue because it is the reflection of the water, and vice-versa.
The explanation by ocalhoun is perfectly good and also has the added benifit of being right! There is a difference between absorbtion and reflection and the blue colour is because water absorbs all the other wavelengths of light - the blue light is not reflected any more or less from the surface (if you look in a puddle you can still see the other colours being reflected), but as the light travels through the water then only blue is left (until obviously it is fully absorbed also at depth).
http://www.dartmouth.edu/~etrnsfer/water.htm
The sky is blue for a very different reason - the air molecules (NOT water.dust etc) scatter the blue wavelengths more than the other colours and this creates the blue colour. For details visit below:
http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html Now, I've heard that the sky is actually purple, but because we have trouble picking up purple light, we only see the blue. (just like how yellow light looks white, purple light looks black)
This is due to scattering. There are different domains of scattering, Reyleigh scattering, MIE scattering and Geometric optics. the main parameter is the size of the particle, (the scatterers). In the case of the sky, its mostly dust particles so it belongs to the Reyleigh scattering regime. Reyleigh scattering has the famous lambda^-4 intensity formula so when light hits a particle, the most scattered light is blue light. you can read a primer on this. for this reason, water reflects the color of sky => resulting to blue color of water.
Pure water really is blue, but you need a long tube to actually see it. The reason for this is that the transition probability for absorption of other visible wavelengths is very low (to the fourth or fifth level) so little non-blue light will be absorbed. But if there's enough water (a long enough path for the light to travel through) there's enough absorption for the light to be visibly blue. This is not the case for the heavier D2O.
Ah!!! Thanks for the answer, now I know what to answer to my pesky 3 yrs old 
The correct answer for a 3 years old kid is: "the water is blue because the snow is white and the sand is yellow and the soil is black, because some leafs are green and some red... YOU HAVE TO KNOW HOT TO MAKE THE DIFFERENCE. So that' why the sky is blue... But you kid, try to paint other colors on this elements... maybe you like it!... AND DON'T ASK THIS QUESTION AGAIN! 
The water is blue because the sky is blue. The sky is blue because it is full of Oxygen and Nitrogen, which reflect blue light.
I love how everything is so simple and so incredibly complex at the same time.
| riv_ wrote: |
The water is blue because the sky is blue. The sky is blue because it is full of Oxygen and Nitrogen, which reflect blue light.
I love how everything is so simple and so incredibly complex at the same time. |
Unfortunately it's slightly less simple that you think. You are, unfortunately, wrong.
If you observe the ocean on a cloudy day it is no less blue than on a clear day. This disproves your theory.
The reason why the oceans are blue is because WATER IS BLUE.
If you want to know why water is blue then you will need to consider radiative scattering - as has already been said by arnie, ocalhoun, dac_nip and powers1983.In fact students at my chem lab did the experiment once for a Dutch national TV show. They prepared a long tube with water to show it really is blue.
| Arnie wrote: |
| In fact students at my chem lab did the experiment once for a Dutch national TV show. They prepared a long tube with water to show it really is blue. |
Nice one. Observation trumps theory everytime
