Why is the sky blue?

ROCHESTER, N.Y. (WROC) — The last few days in Rochester have been nothing short of beautiful. Warm temperatures and mostly clear skies, allowing for the sun to shine. But, have you ever sat down and wondered why the sky is blue? Let’s break it down.

The short answer is that when sunlight reach the earth’s atmosphere, it is scattered in all different directions by gases and particles in the air. Blue light is scattered more than the other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time. But, let’s take it one step further and break it down even more.

When looking at the light from the sun, it looks white. However, this is not the case. In reality, the light from the sun is made up of all the colors of the rainbow. When white light shines through a prism, the light is separated into all its colors. Just like energy passing through the ocean, light energy passes in waves as well. Some light travels in short, choppy waves while others travel in long, lazy waves. Taking a look at the image below, look how much shorter the blue light waves are than the red light waves.

According to NASA Science Space Place, all light travels in a straight line unless something gets in the way and does one of these things:

1. Reflect it (like a mirror)
2. Bend it (like a prism)
3. Scatter it (like molecules of the gases in the atmosphere)

When the sunlight reaches the earth’s atmosphere, it is scattered in all different directions by all of the gases and particles in the air. More specifically, blue light is scattered in all different directions by the tiny molecules of the air in Earth’s atmosphere. Blue light is scattered more than other colors because it travels in short and choppy waves, hence why we see a blue sky most of the time.

When closer to the horizon, the sky fades to a lighter blue or white color. The sunlight reaching us from low in the sky has passed through even more air than the sunlight reaching us from overhead. According to NASA Science Space Place, as the sunlight has passed through all this air, the air molecules have scattered or re-scattered the blue light many times in many directions. Also, the surface of the earth has reflected and scattered the light. All of this scattering mixes the colors together again so we see more white and less blue.

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