Why is Snow White

Few things in the world are “white as the driven snow.” We are all too aware of this while driving on a sunny winter’s day, but we seldom stop and consider why this is so.

The light that comes from the sun is “white light”; however, when its photons hit an object it allows us to see colors in the object due to the particular length of the light beam. Most objects absorb some light, and therefore have color. Snow reacts differently, in that it reflects, rather than absorbs.To understand why snow is white, you need to understand what albedo is. Albedo is a Latin word meaning “whiteness”. The albedo of an object is the extent to which it diffuses light from a light source, such as the sun. There is actually a scale by which an object’s ability to diffuse light is gauged. And, when it comes to reflecting light, snow is at the top of the list.

Even water can absorb light. In fact, only about 7% of the light is reflected from water. But snow is made up of billions of crystals that send the light rays shooting out in all directions, instead of being absorbed. No wavelength can be totally absorbed or reflected. So, the color we see is no color at all. What we see is true bright white, so it’s easy to understand why this reflection can cause “snow blindness”.

We are all aware that light colors reflect heat, and dark colors absorb more heat. That’s why in warmer climates people wear white, or light colored clothing. The diffusing power, or albedo of snow is different depending on where it is located. It can be as much as 90%, but even in Antarctica it is a little more than 80%. Once the snow begins to melt, it lowers the albedo, and causes it to melt faster as it absorbs the heat from the light rays.

Occasionally, snow has a bluish cast to it. This is caused by areas that have lost some of their ability to reflect light. A glacier will sometimes appear to be blue because, although there may be a layer of snow on top, beneath, the snow has become ice, which can absorb light rays, and so produce some color. Colors that can appear in snow when the conditions are rights are yellow, orange, green, purple, or rose. In the Antarctic, there is a red algae that grows on the snow, turning it a pink/red color.

While few things are as white, bright and beautiful as a world covered in bright white snow, it can become dangerous, and when driving or playing in the snow, your eyes should be protected at all times.