why is the sea blue?

Answer 1

the sea is not blue it just appears so because of the sun light shinning on it

Answer 2

While the sea does reflect the sky, this has nothing to do with the sea's blue color. A reflection is just on the surface and is seen as an image, not as the entire body.

The reason the sea is blue is quite simple - WATER IS BLUE. In small quantities (like a glass) water appears to be clear, but when you look at it on a larger scale you start to see its blue color (think about an indoor swimming pool - these are faintly blue, but there is no blue sky above them). This is why lakes, rivers, and the ocean appear blue but a glass of water will look clear.

So why is water blue? There are several theories - I think the best one is this... When sunlight hits the ocean it is scattered by the water molecules that make up the ocean. Sunlight is made up of all of the colors of the rainbow (red through violet). Water molecules scatter blue light the most. This makes the ocean look blue. Along the shores of some areas, however, the water looks green because the blue water is mixed with yellow pigments present in floating plants.

Water doesn't always look blue - the Black Sea appears black because of its low oxygen content and high concentration of hydrogen-sulfide. The Red Sea appears red because of algae blooms. The Yellow Sea appears yellow because of the yellow mud carried into it by rivers.

All these bodies of water are still reflecting the blue sky - but do not appear blue. I think that really puts that theory to bed.

EDIT:
People are giving some answers that are sort of right, but are confusing or even misleading. When I say that "water is blue", I mean it is blue when exposed to the light of the sun. This is the same as saying "grass is green", but grass is only green when exposed to the light of the sun. Were grass exposed to light that is not full spectrum (like a red light or black light), then grass would be a totally different color. The same is true for water. It is only blue because of the spectrum of the sunlight it recieves. In general, water is blue when exposed to white sunlight which contains all the colors of the rainbow. On a cloudy day the light that reaches the ground is not full spectrum, so the water will not appear to be as blue (it will be a greyish blue).

I don't feel like I'm explaining this very well, but I feel the other answers need clarification. I wish I could do a better job, but I'm just not that smart.

Answer 3

The sea is actually colourless but we see it blue due to the reflection of the sky in the water. Try it, go and watch the sea in a cloudy weather, the sea won't appear blue.

Answer 4

The sea is not blue. It may reflect the colour of the sky though

Answer 5

The colour of the sea is ever-changing, from all shades of blue to all shades of green and even to brown. The colour changes depending on many things. Among them is the depth of the water, the plankton and seaweed growth in the water, the cleanliness of the water and the brightness of the sky.

Answer 6

It is blue because it reflects the colour of the sky. The colour of the sea is ever-changing, from all shades of blue to all shades of green and even to brown. The colour changes depending on many things. Among them is the depth of the water, the plankton and seaweed growth in the water, the cleanliness of the water and the brightness of the sky.

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 white light from the sun is a mixture of all colours of the rainbow. This was demonstrated by Isaac Newton who used a prism to separate the different colours and so form a spectrum. The colours of light are distinguished by their different wavelengths. The visible part of the spectrum ranges from red light with a wavelength of about 720 nm to violet with a wavelength of about 380 nm with orange, yellow, green, blue and indigo between. The three different types of colour receptors in the retina of the human eye respond most strongly to red, green and blue wavelengths giving us our colour vision.

Tyndall Effect
The first steps towards correctly explaining the colour of the sky were taken by John Tyndall in 1859. He discovered that when light passes through a clear fluid holding small particles in suspension, the shorter blue wavelengths are scattered more strongly than the red. This can be demonstrated by shining a beam of white light through a tank of water with a little milk or soap mixed in. From the side the beam can be seen by the blue light it scatters, but the light seen directly from the end is reddened after it has passed through the tank. The scattered light can also be shown to be polarised using a filter of polarised light, just as the sky appears a deeper blue through polarised sun glasses.

This is most correctly called the Tyndall effect but it is more commonly known to physicists as Rayleigh scattering after Lord Rayleigh who studied it in more detail a few years later. He showed that the amount of light scattered is inversely proportional to the fourth power of wavelength for sufficiently small particles. It follows that blue light is scattered more than red light by a factor of (700/400)4 ~= 10.

Answer 7

sea is not blue , it just appears to be blue , otherwise it is transparent
sea has all water as u know which is denser than atmosphere and speed of light is quite less than that in air
when light enter water it undergoes refraction , and when light from water enters air it agn undergoes refraction
during all this process , scatterin of light takes place , due to variable wavelength of different components of light
b coz blue has minimum wavelength it refracts the most and and reaches our eyes
that's why sea appers to be blue
there is no other reason behind this phenomenon

Answer 8

the sea is not really blue. it actually depends
on the weather, if the sky is blue it's color will
reflect onto the sea.
whereas if it is cloudy out there, look at the sea,it will
look all grey!

Answer 9

Because it reflects the sky,which in turn is blue because of the way sunlight passes through the molecules of the different gases that consist the atmosphere.

Answer 10

It's because water is in fact Blue.