Photographers all know about polarizing filters. They remove reflections off the surfaces of objects. We use them to see into water or windows that are obscured by those reflections. But anything with an even slightly glossy surface has a layer of reflection on top. So if you have a shiny green plant, it can remove the shiny and reveal a very saturated green underneath. Polarizers also remove a lot of scattered and reflected light from the sky. Which reveals a deep blue color you didn’t even know was there.
Here is a photo I took of my circular polarizer.
And the first thing I noticed when walking outside during the eclipse was the color of everything was more saturated, just like in that circle. Apparently, an eclipse significantly reduces polarized light and I got this creepy feeling because I was only ever used to seeing the world like that through the viewfinder of my camera.
The other thing I noticed was my outdoor lights. I leave them on all the time because I never remember to turn them on at night. And usually the sun will render them barely visible during the day. On a very sunny day they almost look like they are off.
But you can clearly see they are shining and even flaring the camera during the eclipse.
Our eyes adjust to lighting changes very well so it was hard to tell how much dimmer things were, but that is a good indication. I took this photo a few minutes ago and you can see how dim the lights appear after the moon has fucked off.
I did a calculation using the exposure settings between these two photos. The non-eclipse photo has 7 f-stops more light. That is 128 times or 12,700% more light.
A partial Pringle eclipse cut the sun’s light by 99.2% and somehow our eyes adjusted to make it seem like a normal sunny day (with weird ass saturated colors).
Not a camera person, so eclipses are the only time I’ve ever seen this effect: didn’t realize it was from polarization.
I wonder if, on worlds orbiting dimmer stars, the light looks like this all the time?
It’s not. I’m not a camera person, but I am an engineer person. The moon is blocking out polarized light in the sense that all light is technically polarized, since that is just a function of light being transverse waves. We describe the light from the sun as unpolarized because all of the individual waves are polarized randomly. A polarizing filter only lets light in certain orientations through. This removes glare and reflections because the light from glare and reflections isn’t in the right orientation to pass through the filter.
The moon isn’t selectively filtering light, it’s just indiscriminately blocking most of it. The effect of colors looking more saturated is likely because there is just less light available to cause glare in the first place, but there may be some other mechanism. Regardless, it’s not polarization in the sense that a polarizing filter makes things look more saturated.
If what I said didn’t make sense (because I know if you haven’t seen this explanation before it may seem like gibberish), this has pictures that help explain what’s going on visually.
I admit I am not a light scientist and perhaps I am misunderstanding, but I believed I confirmed my observations with this post from American Scientist. Here is a summary of what I found to be relevant.
“From an observation site in Hermon, Maine, they made measurements of the spectrum of the sky before and during the eclipse. They indeed found that the spectrum of the skylight shifts towards blue, thus appearing more purple to the human eye, as Halley observed.
…the purple appearance of the sky during an eclipse is due to different light scattering processes becoming more significant.
Most natural light sources produce unpolarized light, in which it rapidly and randomly changes the direction it oscillates. Light coming from the Sun is unpolarized, and one would naturally assume that the light of the sky during the day is also unpolarized—however, this is incorrect, as the following video shows.
When one looks at the sky through a polarizer, which preferentially blocks polarization in one direction and allows the perpendicular direction to pass, one sees that light in the sky possesses some amount of polarization. Just as the scattering of light in the sky is different for different colors, preferentially scattering blue, the scattering of light is different for different polarizations. If one measures the direction of polarization in the sky, one finds that the direction of polarization forms a complicated pattern that has been more or less known for nearly 200 years.
There are four “special” points in the sky which possess no direction of polarization, as illustrated in the figure. At these locations the light is in fact circularly polarized. As the figure above suggests, it is generally not possible to see all four of these neutral points at one time, though they were all measured from a hot air balloon a few years ago. It was natural to ask whether the neutral points change during an eclipse, and in 1999 a Hungarian research group investigated this question during the August 11 eclipse that passed over that country. The results they found were quite complicated, but definitely showed a significant change in the polarization of the sky during an eclipse.”
Perhaps I did not explain it perfectly. But the article made it sound like the sky was shifting to purple in a similar way that is seen through a circular polarizer filter.
