I was skiing in Whistler, Canada and had to pull out my Go-Pro helmet camera when I saw this weird glowing column of bright sparkling light. From where I was standing it looked like a fountain of light. SUPER bright. As I skied closer to it and around the corner it shrunk to more of a hovering ball of light. The sparkling became more apparent. As I skied around it the concentration of light seemed to stay fixed in place, hovering above the earth. however, as I got closer and further around the corner it continued to diminish in size until it finally disappeared when I got into the shade.
I have skied my whole life, grew up in a cold and snowy climate and have never seen anything like this. Can anyone tell what this phenomenon is called and how it works?
Here is a link to the video. I just posted it to YouTube so I could learn more about it. Please ignore the bad skiing, and forgive the bad camera work.
Yeh, it looks like some kind of lensing of sunlight, probably from the snow/ice crystals in the air.
Certainly odd though, I can’t tell from this video, since there’s no true perception of depth, if it’s projected on the side of that hill, of did it look like it was just a shaft of bright light in the middle of the air?
I don’t see how it can be sunlight reflecting off the snow, like in Chessic Sense’s picture. The snow is in shadow.
I’d have to guess that the snow on the hill has a crystal shape that causes it to act as a retro-reflector over a small range of angles. If I’m right, the portion of the snow where you’re seeing the light is reflecting the light of the snow near you into your eyes. Similar to the way road signs reflect headlights preferentially back towards the driver.
It appears to be a Sun Pillar, which is caused by sunlight reflecting from flat (usually hexagonal) plates that are oriented very nearly flat relative to the ground. The lack of color separation shows that this is not a refractive phenomenon, and it is clearly in perfect alignment with the sun, as you can tell from the shados of people around it.
Not really a subsun. A Subsun is what you get when the ice plates are really horizontal, and act very much like a mirror, reflecting the image of the sun. In that case, you get pretty close to a disc, as far below the horizon as the sun is above it. I’ve seen these from airplanes.
This appears to be spread out over a horizontal region. It occurs when the plates have a range of angles, but are relatively horizontal. You expect this sort of thing closer to the ground, where the air’s more turbulent. Then you get a vertical shaft of light, rather than a confined image.
Of course, you don’t generally get a perfect image of the sun… There are lots of stages betweebn a sunsun and an inferior solar pillar, but I think you’re closer to the latter here.
But it is clear to me that the sunlit slope in front of the shaded hillside is acting like a parabolic mirror reflecting the sunlight back onto the shaded hill.
THis is even more evident by the footage where glittery snow in air is seen around 4 min. The skier is in the spot of the mountain that is doing the reflecting and is in essence standing in (or close to) the mirror.
I don’t think it is a subsun because it looks like subsuns reflect light back up to airplanes and are caused by snowflakes in the air. I think this caused by a snow covered concave hillside reflecting and concentrating the light.
Sorry, folks. The odds of a valley (especiallyu one coated with diffusely reflecting snow) acting like a parabolic reflector is effectively zip.
And Naturally-occurring lenses and mirrors tend to concentrate light into cusp-shaped regions called caustic, with generally different shapes than the simple column you see in the film. That’s a solar pillar. See the links in my post.
Take a look sometime at how optics are manufactured, and the tolerances used. If you’ve got a shiny suirface reflecting the light, I could see your getting caustics and relatively good foci. In fact, it’s happened with buildings in Los Angeles (The Gehry-designed, very shiny Disney auditorium http://en.wikipedia.org/wiki/Walt_Disney_Concert_Hall ) and the Las Vegas Vdara Hotel, which is notorious for its “Death Ray”
Note that these are both shiny buildings. As you note, it’s hard to find a “Cite?” for a negative. The very nature of a diffuse reflecting surface – in which light is scattered in all directions – prevents it from concentrating light towards a focus, as happens with parallel light reflecting in a specular (non-diffuse) fashion from a paraboloid. Fortunately, there exists a counterexample – the “umbrellas” used by photographers to provide diffuse light from one direction. They bounce light off a concave diffuse curved surface:
It’s not exactly the same thing, since the light source is relatively close (but isn’t a point source, and probably isn’t at the focus), but it illustrates the point. If you doubt it, take a white umbrella out and try to focus the light from a distant source using it.
Actually, it occurs to me that there IS a case where a diffuse white reflector is used – inside integrating spheres. These are perfect spheres that are hollow* and coated with white diffuse reflecting material. the idea is that you introduce light that you’re curious about in through an aperture. It bounces off the walls many times and gets regularized in the process, so if you stick a detector into the sphere you get a measure of the absolute flux of photons, without “hot spots” (they often put a baffle in to prevent light from going directly from the source to the detector). If the theory that you could use the diffuse interior as a sort of parabolic reflector were true, there ought to be an image of the source on a line connecting the source with the center of the sphere.
But there isn’t – the whole point of using the sphere is to see to it that the light is “evened out”. Even if the diffuse coating isn’t perfect, the multiple reflections make the walls of the sphere act like a nearly perfevct Lambertian source. http://en.wikipedia.org/wiki/Integrating_sphere
*especially with infrared sources, people often fake the “perfect sphere” part. But visible integrating spheres are made nearly perfectly spherical.