I would like the following excerpt from BA’s “Why is the Sky Blue” article to be reworded:

Text as it currently reads:

“Here's a simple refutation of this Bad Idea: if the sky were blue due to reflection from the oceans, wouldn't the sky be less blue farther inland? It isn't, so this cannot be the correct explanation.”

Text corrected:

“Here's a simple refutation of this Bad Idea: if the sky were blue due to reflection from the oceans, wouldn't the sky be clear in the middle of a large continent? It isn't, so this cannot be the correct explanation.”

Alternatively corrected text:

“Although blue skies over blue water are more blue, this does not explain why the skies are blue over large land masses.”


The sky is indeed blue for all the reasons written so well in the article.

The sky is, however, more blue over water and less blue over land.

How can this be?

Water is blue. Water is not blue simply because it reflects a blue sky. Water is intrinsically blue.

From the article in question: "However, red light actually travels less through water than blue! This is why the oceans are blue; they absorb red light so that only the blue part gets out."

Recently I’ve been told that the reason water appears to be blue is that it is reflecting the blue sky. I do not doubt that a blue sky can make water appear more blue. I have a red car and I have a blue jeep. When it is a bright sunny day the red car looks red and the blue jeep looks blue. When it is a cloudy day my red car looks red and my blue jeep looks blue. The sea looks blue on sunny days and on cloudy days too. I took a mirror outside today since it is very overcast here now the sky looks white. The reflection of the sky in my mirror looks white. This is because my mirror does not preferentially reflect one color more than another. My jeep looks blue today even though the sky is white. It’s because the jeep absorbs other colors more than blue and reflects blue more than any other color. The sea looks blue on cloudy days as well. This is because it reflects blue more than any other color and absorbs other light more than it absorbs blue. There is a term commonly used to describe an object that reflects blue light more than other colors. The term is “blue”.

Still not convinced that water is blue?

I’ve seen the not so rare phenomena of an indoor lap pool drained. It was painted white before and was given a fresh coat of new white paint. When the pool was filled once more, the water looked blue. Blue water in an indoor pool that is painted white can hardly be explained by a blue sky.

Need more?

Why is Cerenkov radiation blue? It’s because water is blue.

One more:

In this link the experimenter tests water for color with a spectrophotometer. And finds that water is indeed blue.

So even if you’ve never stood on a beech at noon and looked over the water at the sky and back over the land at the sky would it be too hard to imagine that a blue sky could be made to appear more blue because of a large body of water reflecting blue light back up into the sky so that more blue light would be reflected down to an observer?

I spend a lot of time on sea, and on cloudy days it looks very gray to me. And up close, it is distinctly green (although I am aware that's due to algae).

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Fiction has to be plausible. Reality is under no such constraint.

No doubt that a blue sky will make blue water look more blue. No doubt that particles in the water will make it appear different colors. I've seen red smoke bombs. Neither you nor I would suggest that air is red. Neither you nor I would doubt that small ammounts of air appear to be clear.

Take a look at this photo with your expirenced eyes and tell me what you see.

I see the sea on a mildly cloudy day. That's what water looks like in indirect sunilght. If you were standing on that ship, you'd see the sky as patchwork of blue and white, with the sun hidden.

On a HEAVILY overcast day, the sea is gray.

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Fiction has to be plausible. Reality is under no such constraint.

More data on the sky color, please, and less rhetoric.

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There's enough to discuss already. Deal with what's already on the table.

Yeah, I read it. That's why I asked for more to back up your claim:

It's unconvincing that the very slight blue color of water -- well documented, I feel -- actually somehow produces a more intense blue in the sky. Can you not find a source that measured the blueness of the sky above the ocean and above land?

As a skeptical person yourself, what fact convinced you that the sky is more blue over water?

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105,

I cannot find any scientific source for the blueness of sky over water or over land. The original BA article cited no scientific basis for “It isn’t.” either.

In photos and in my own experience, the sea can appear a deep dark blue. The sky is only ever a pale blue.

The fact that convinced me wasn’t a fact in a data driven scientific sense. It was accounts of seamen in the age of sail using the variations of sky color to predict proximity to land masses over the horizon. I don’t think any contemporary human has the knowledge that the sailors of tall ships had.

See if this logic holds up:

The sky is blue over land and over sea. That means that the sky’s blue appearance is due to its own interactions with sunlight.

For my assertion that the sky is more blue over the sea to be correct just one photon in the energy band of the blue end of the visible spectrum has to make it from sea to sky.

For the BA assertion that the sky’s blue color is not in any way influenced by the blue sea to be correct no photons in the blue spectrum energy band can reach the sky from the sea.

It is my assertion, based on personal observation and logic, that the vast amount of blue light leaving the sea doesn’t all pass through the atmosphere to space. Some of that light is scattered by the air and contributes to the blue appearance of the sky.

Additionally:

The sky reflects light back to Earth even if the light originated on the surface of the Earth.

Why are large telescopes often located away from cities?
Why are stars more visible in the country than the city?

City lights are white and although they are not full spectrum they are still covering the red and blue ends fairly well.

There are several online resources that confirm that ice can be seen over the horizon by its white reflection in the sky.

Forest fires and other large fires can be seen over the horizon by their red reflection in the sky.

So, the sky can reflect white and red light.

If the sky could not reflect blue light then reflected white light would appear more red. Therefore, the sky can reflect blue light.

Place an observer in the middle of a large ocean. The simple absence of the reflections from land will make the sky appear more blue.

Add to this the presence of blue light from the sea reflected back down to the observer and the sky will indeed be more blue.

Clouds.
Seafarers found distant land by the change in the light reflected by clouds. Likewise the "ice blink" and "water sky" of the polar explorers, the "herring blink" of fishermen, and the darker cloud layer I can see above distant coniferous forests that have shed their snow, when I travel across snowy countryside.

Grant Hutchison

I've no doubt about clouds, particularly low clouds having reflections in them. The clouds do not account for all the reflections seen in the skies.

Consider this quote:
Even if one were to remove the examples you cite, the sky is still known to reflect terrestrial light sources back to the surface.

Can you tie what you posted back to the main topic of this thread?

You really think one photon would cause someone to see the sky more blue? Besides, one "blue" photon headed into the sky would likely be seen by no one. It would have to be scattered to someone.

I suspect your logic is fine in principal, however, there are other factors which limit the appearance of a richer, augmented blue sky. The best blue skies I've seen are from land, and I've spent many hundreds of hours along the sea. Moisture and dust from winds, etc. produce a white haze that bleaches the blue appearance of the sky. It is the net effect of all the factors which determines the real impact on what we see.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

No. And that wasn't my claim either.

Ok. Isolate the factors that only affect sky over land from those that only affect sky over sea. I can't.
I'm sure we've all seen rain over land at least. Many of us have seen rain over water. So moisture is not unique to either land or sea. Dust, however, must be more common over land. Also, inner-city ozone is mostly a land-based phenomena. Industrial gaseous output is mostly a land-based phenomena. I chose to leave out particulates in the air on purpose because they can cause the sky to look unnatural. If you have some source you wish to cite that shows air over water being more prone to carry particulates than air over land I'd like to see it. I suspect that air over land is actually more likely to have particulates.

When I fill a white bathtub with water, the color of the water is
distinctly green, not blue. I'm willing to admit the possibility that
there is something in the water which gives it a green tint, though
I doubt that is the explanation. Another possibility would be that
a greater thickness of water is required to make it appear blue.

-- Jeff, in Minneapolis

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http://www.FreeMars.org/jeff/

"The other planets?
Well, they just happen to be there, but the point of rockets is to explore them!"
-- Kai Yeves

Mirages are not reflections. If we saw a mirage of the sea's colour in the sky, we'd see the sea in the sky: a phenomenon that sailors call looming.

I'm suggesting that the "accounts of seamen in the age of sail using the variations of sky color to predict proximity to land masses over the horizon" do not contribute anything to your argument, since they relate to a clouded rather than a blue sky.

Grant Hutchison

Ok.
I knew about other signs seaman used. (IE birds, clouds, scents, and shoaling)
I wasn’t referring to clouds, reflections of clouds, or reflections in clouds. I understand, now, that what was reported wasn’t a reflected image after all. It was a refracted image or multiple images. So I get it. The images that included both upside down and right side up objects over the horizon were not reflections even though they were reported as such. Do you think it’s just possible that a sailor from say 100 years ago or even yesterday could see a ship floating in the sky and not see that ship on the sea and report the sighting as a reflection? Is it possible that conditions which allow very clear images to be seen could be more rare than conditions which allow blurry images to be seen? So that at first the image may be just a dark shape then come into focus for a few seconds and then dissolve into a blur as the cold and warm air mix?

The greater point is that terrestrial light is returned to observers on the surface by the sky. I think there are enough other examples of this without relying upon refracted images even if they are reported as reflections.

Now that you’ve weighed in, tell me, is the sky more blue over the sea than land?

I would think it would appear more blue as your view approaches the zenith, especially if the air is dry. The view toward the horizon would become more white due to the additional air mass issue, as well as, Mie scattering issues. Keep in mind the blue photons keep scattering and scattering. Given enough air mass, they begin to scatter more away from the observer and the color becomes closer and closer to the original source color (i.e. the white sun). Grant has elaborated on this issue on at least one other thread, which I can find for you if you like.

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Lighten up! This is a stellar board! Author: duh.

"The Sun, with all the planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do..." Author: Galileo supposedly.

I think that because other variables strongly affect the saturation of the blue sky, the sort of effect you're talking about is going to fall below the noise level.
I've never seen any systematic difference between sky colours over land and sea.

Grant Hutchison