OK, so yesterday’s xkcd got me thinking about not only the color of the sky, but also of the oceans.
So imagine a planet with oceans much like ours, so Rayleigh scattering and preferential absorption of blues still play a role, but where the sun and/or atmosphere are significantly different in color.
Perhaps a sun just as bright as ours, but with peak wavelength emission in the reds. Or a planet with a sun much brighter than ours, with atmospheric particles that cause its sky to be a bright pink of the same intensity as our blue sky.
What color might the ocean on these planets appear and why? (It would still vary from day to day based on the weather and plant life, just as on Earth, but assume a clear, bright day with no color change due to life in or on the water.)
I don’t know the exact answer but red or pink skies sometimes happen on earth as well.
The color of the ocean looks like this for example. That sky isn’t as bright as normal sunlight but it still suggests a dark blue ocean with pink highlights where the sky is reflecting off of the waves.
Yeah, this could just as easily go in IMHO, I think, since there may not be an easily-obtained “right” answer.
Very nice video clip, by the way. Liked the color in that one.
The problem with when Earth’s skies are pink and red there’s usually a significant decline in light intensity as well - dusk, dawn, and areas shrouded in soot from fires or volcanic eruptions. I’m more curious about what a beautiful, clear day at the seashore of Ceti Alpha 4 is like.
The ocean does its own scattering, so it’s still going to “prefer” to appear blue. Since even blue skies have some red light coming through and even red skies have some blue light, your ocean is still going to be blue unless you change the chemical composition of the water.
Not in my opinion. I think it’ll look a lot like Shagnasty’s video - at best, you have red light reflecting on blue water.
In water, red light is absorbed more quickly than blue, so light that gone into the water and then back up out of it has traveled a fair distance and will strongly favor blue light. On Earth, we have sunlight that is pretty close to white (that is, all the colors are present) and so the blue is what comes back up. It may be pretty that we have blue sky reflecting off of blue water most of the time, but the water would be blue anyway.
The only way to get red water would be to use red light, but even red skies and red stars will have some other spectra of light mixed in, so I don’t think you’re going to wind up with water being anything but bluish unless you also change the composition of the water. You can get red tides or pink lakes on Earth caused by microorganisms.
Water has an intrinsically bluish/turquoise color to it, it’s just very weak looking through shallow volumes which gives the impression it’s colorless. Although, what makes oceans, lakes and other bodies of water appear blue is due to many things, such as Rayleigh scattering, fresnel reflection of the sky, particles and impurities in the water, etc.
But, even after a few meters of depth, it’s natural blue color does become apparent.
What color an ocean on another planet, like Mars (a dusky rose color sky) might appear, all depends on the purity of the water, how much the reddish wavelengths are absorbed or scattered, and how much the surface reflects the sky.
My guess is it’d appear a dull, steely blue or indigo; not quite as vivid as on earth.
The colour of the sky is dependent on the density of the atmosphere, the colour of the star in the sky,and the colour of any particulates in the atmosphere.
This could in theory lead to a quite wide range of colours. However, quite boringly, the range of colours that would be seen on planets that could support human life is quite narrow- it probably goes from pale blue to turquoise, and the colour of the sea would hardly be affected.
Worse still, the human eye/brain system would probably compensate for this minor colour variation, and what you would end up perceiving wouldn’t be much different to what you see on Earth.
It’s apparent in my bathtub, so far less than a few meters of depth is required. (And no, there’s nothing blue in my bathroom, that’s water’s own color.)
Oh, no doubt. Still, to be sure of its truest color, and eliminating incandescent or other ambient light (or the color of your tub walls… white isn’t always white) you could take a clear tube, about a meter tall, fill it with distiller water, and using only a 6500 K° light (the color temperature of daylight) to illuminate the column and peer down its length.
Cite? I’m genuinely curious. I’ve worked enough with DI water to think that it’s colorless. Plus, there is a color standard (colloquial) known as “water-white”, meaning colorless.
I’d love to actually carry out the right conditions to see the true color of water. I believe there have been times where it’s apparent, but the conditions were far from described in the experiment.
Thanks for the links!