If you have ever tried to drive or ski on snow in the bright sunlight, without sunglasses, then you know just how bright white snow can be. Actually, it is the most naturally reflective substance on earth, which is the very reason it is white in the first place.
The colors we see all around us are caused by various wavelengths of light penetrating different objects. The depth of penetration and the wavelength determine what color we see, but when it comes to snow, the situation is somewhat different. Snow, as a rule, does not absorb light rays from the sun. Since it is made up of billions of snowflakes, that all have reflective surfaces, light rays bounce off the snow in all directions, so all we see is the reflective pure white light of the sun. Its reflective qualities even beat out water, which can be very reflective, but still absorbs rays of light, causing the water to appear to be blue or green.
There are, however, instances when even snow appears to be various shades of blue, yellow, or even red or green. New fallen snow contains crystal snowflakes that are still intact, and therefore, excellent light reflectors. However, when snow begins to pile up into snow banks, snowflakes become more and more compacted, losing their reflective capability. The same holds true for glaciers, that have been compacted, and frozen, again and again, becoming more and more dense. When this happens, longer, blue light rays can penetrate the ice or snow and cause the formation to take on a blue color. The thicker the snow bank or glacier, the bluer it will appear.
Those who study glaciers and snow, are aware of the fact that as you dig down into one of these snow banks or glaciers, you will encounter various shades of color from yellow to green to blue, the deeper you go. All of this, of course, is due to the penetration of light rays. Instances of red snow are not the result of light rays at all, but a covering of a particular red algae, found in some Arctic and Alpine regions.
This same reflective quality that makes snow bright, white, and beautiful can be dangerous when not treated with care. Snow blindness and damage to the eyes, that may, in some cases, be permanent, are a result of this bright white pure light.
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