Fair enough, but I’ve perhaps spent more time looking out to the North Sea than you and I can assure you that on many days, blueness is the least of its qualities.
My childhood’s belief that the sea is blue was formed by looking at the fucking sea.
There’s a space walk along a bike path I ride from time to time. It’s 3/4 of a mile from the sun to Neptune (no love for Pluto). The planets are to scale too, with the sun 16" in diameter and Saturn being about the size of a golf ball. As a kid in elementary school we did a “human” solar system in the playfield. Poor Pluto ended up lost past the parking lot on the other side of the school while the inner planets got dizzy trying to orbit the sun AND rotate at the same time.
Also, water is blue in indoor swimming pools with no natural light.
From angles and in weather conditions that allowed you to see blueness, which, I repeat, might often otherwise be completely fucking absent.
Moderator Note
Let’s dial it back.
Colibri
General Questions Moderator
Sorry.
If Darwin was wrong about the appendix then evolution collapses like a house of cards! [/Ken Ham]
I got my Anthropology degree in 1976. Unlike the situation for most majors everything I know is wrong. Except that Piltdown Man was a hoax.
Isn’t light blue or turquoise tile the norm for swimming pools?
Imagine my shock to discover that Alaska isn’t an island off the coast of Baja California.
The very first result shows white, as do a lot of the other photos. I’ve been in plenty of white-lined pools and the water is still blue, or more of a light turquoise. Steps help to show the true color of the lining. https://www.tinostone.com/projects/casino-ibiza/
Sorry
OK, but (to continue with suitably dialled-back demeanour) the angle of view is not dependent upon the colour of the sky. I can look down on the water from a harbour wall, or Brighton pier on a sunny or cloudy day; I can look through the crests of breaking waves in summer or winter; I can (as we saw in the second linked video) go snorkelling on an overcast day, or under a clear sky - and in all of those situations, the sea is blue.
The reflection of the sky, on the surface of water, is different when the sky is different - but that is not what was falsely asserted to me at school - the assertion was: water is colourless; the sky makes the sea blue. This is demonstrably false.
Things “are” colors because they emit light, they reflect light, or they transmit light. I think we can agree that water does not emit light so it has color for one of the other two reasons. Usually, but not always, we thing of the color of something as the color it reflects.
Water transmits the portion of the electromagnetic spectrum that we call visible light. As this site points out, that is not a coincidence. Eyes evolved in organisms in the water. They were only useful if they were sensitive to the wavelengths of light available.
Actually you can see that water transmits blue light better than red. That is one reason why those nice natural light underwater photographs have a nice bluish tone to them.
But the more important reason is impurities. Tiny particles in the water (or air) preferentially scatter shorter wavelengths. Although all the colors pass through water, the blues are preferentially scattered and some of that scatter returns back through the surface to our eyes. If some impurities are somewhat larger, the green light is also scattered.
It’s still not a case of a scientific theory being wrong. Just one science teacher (or one book) being wrong.
(This may not quite meet OP’s criterion.) Archimedes did find a way to determine whether a gold crown was counterfeit by immersing it in water, and the obvious displacement test deduced from scanty record and written up by the great Marcus Vitruvius Pollio was sound in theory.
It seems that it was Galileo Galilei who first deduced that Archimedes took full advantage of his Principle of Hydrostatics by weighing the crown with a balance scale while it was immersed.
[Emphasis mine]
Hmm…if you look at the absorption spectrum for water at a slightly more useful scale:
You’ll notice that blue is transmitted a whole lot more than any other color; based on that alone, light transmitted through any substantial depth of water is going to be largely blue anyway.
Obviously, light scattering due to nanoscale particulates is a thing. Rayleigh scattering plays a large role in the atmosphere, but atmospheric Rayleigh scattering primarily scatters blue light, making it a low-pass filter that transmits yellow and red light better than blue light.
That’s a big reason why sunlight looks yellow, especially during the aptly-named golden hours at sunrise and sunset. But under water, blue light dominates.
It’s possible, of course, that ocean water looks blue from below because water transmits it preferentially while looking blue from above due to Rayliegh (or Mie or whatever) scattering.
Since water transmits blue light while mostly absorbing other colors even without scattering, I’d love to see confirmation of your claim that the sea is blue mostly because of blue-light scattering.
In short: got a cite? I mean specifically for the claim that scattering plays a bigger role in making the ocean look blue than does the blue-transmitting absorption spectrum of water.
Do I have a cite, no sorry. But when you’re looking at a lake or ocean from above, you aren’t seeing the transmitted light. The light source is from above the water surface so the transmitted light stays below the surface. I don’t see how the transmitted light could have anything to do with the blue color we see except under water as I noted.
If you are thinking of Rayleigh scattering which preferentially scatters blue light – that is why the sky is blue, but my understanding is that it only happens with free (gas) molecules, not molecules bound up in liquid or solid.
When you look into the ocean, what you see is light scattered by particles (dust, plankton, etc) floating in the water. These particles are generally much larger than the wavelength of light, so scattering is not preferentially blue. It’s mostly “white”, i.e. the same color as the light shining on the particle. And because water preferentially absorbs red & green light, that light shining on the particle is blue.
Wikipedia has a whole page on color of water, with a section specifically on color of lakes and oceans, which backs me up on this. It also discusses the reflection of the sky as being one component of it.