Snow is white because it reflects all the sunlight. The ice crystals that make it up scatter light in a random way, giving it this characteristic white color.
Snow is made up of a multitude of small ice crystals. These crystals have a specific geometric shape, often in hexagon, with six symmetrical branches radiating from the center. Their structure directly depends on how water freezes and assembles at the molecular level. Essentially, water molecules bond together while always maintaining the same hexagonal organization due to their chemical properties. This ultimately results in a multitude of crystals with varied shapes, but always based on this six-branched star structure. And it is precisely this particular network that plays a significant role in how light bounces off it, explaining why snow is so uniformly white.
Snowflakes are made up of tiny ice crystals with complex shapes, like little stars or dendrites. When light hits them, it bounces off all the facets and scatters in various directions: this is called scattering. This scattering occurs in all possible directions due to the multiple crystalline surfaces. As light hits everywhere and disperses completely, it creates that impression of bright white color, typical of fresh snow. The smaller and closer the flakes are to each other, the more efficiently light bounces, making the snow appear very white.
Snowflakes are made up of tiny ice crystals interlocked with one another. Together, these crystals act like a kind of luminous maze: rays of light enter, bounce around in all directions, and exit without being absorbed. And since snow reflects all visible wavelengths of sunlight without preference, it appears to our eyes as perfectly white. This is different from a colored surface, like a red apple, which only reflects a portion of the light spectrum. Here, there is no favoritism; everyone is included: red, orange, yellow, green, blue, indigo, and violet. The light rays emerge evenly after bouncing around everywhere, giving that characteristic, pure, and bright white.
The presence of certain particles and pollutants in the atmosphere can directly influence the whiteness of snow. For example, if you have ever noticed somewhat dirty snow, it is often because dust, soot, or other elements have settled on its surface, making the snow less reflective and therefore less white. A cloudy sky can make the snow appear more uniform to our eyes, while a clear and bright sky accentuates the nuances and shiny reflections on its surface. Even a thin layer of dust brought by the wind is enough to reduce that characteristic whiteness. Similarly, recent precipitation often revives the whiteness by covering previously accumulated dirt with a fresh layer. Finally, ambient humidity also influences the appearance of snow: slightly wet snow can be darker than nice dry powder.
Fresh snow, with its airy flakes filled with air, diffusely reflects light, giving it that bright white color. In contrast, pure ice is very compact and transparent, allowing light to penetrate deeply or pass through without being reflected as much. Over time or under weight, when snow becomes compacted, its crystals crush and the air gradually disappears. It then loses its powdery and luminous appearance; it becomes harder and denser, reflecting less light, often taking on a bluish or transparent look. A piece of ice or a chunk of glacier, for example, is transparent or bluish precisely because light passes directly through it, instead of being scattered everywhere.
Freshly fallen snow can reflect up to 90% of sunlight, which is why you may be dazzled on very sunny days on a recent snow cover.
Contrary to a common misconception, snow is not always white: it can take on pink or red hues due to a microscopic alga called 'Chlamydomonas nivalis,' a phenomenon also known as 'blood snow.'
If you closely observe a snowflake, you will notice a unique hexagonal symmetry. No snowflake is exactly identical to another; each crystal has its own structure.
Did you know that the bluish color of ice comes from the selective absorption of certain wavelengths of light? Unlike snow, compact ice reflects and scatters light differently, giving it a blue appearance.
The characteristic sound of footsteps in the snow comes from the compression and fracturing of snow crystals under the pressure of the feet. This sound depends on the temperature, humidity, and the shape of the snow crystals.
Snow may appear slightly blue when it is thick and compact, as blue light penetrates ice better than other colors and is then reflected less quickly.
No, unlike fresh snow, pure ice is generally transparent because its compact crystalline structure scatters very little light. It is the air trapped in the snowflakes that diffuses the light, giving it a white appearance.
No, in the city, the whiteness of the snow can be affected by air pollution, sometimes giving it a grayish or yellowish tint, whereas in the mountains, far from pollutants, the snow generally remains pure and very white.
In certain environmental conditions, snow can take on other hues such as pink or red, due to microalgae called Chlamydomonas nivalis, or even a brownish tint because of atmospheric particles like dust.
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