Some of the most important science questions arise from our everyday lives. For instance, the plants around us, the stars in the sky, and our bodies have prompted a lot of learning about the things surrounding us. One common question many people ask about the world is “Why is the sky blue?” This question is so common that adults and children alike ask about it.
Today, we will answer this question in a way that is understandable by everyone… even kids!
Why is the Sky Blue?
In short, light coming from the sun scatters when it encounters air molecules within our atmosphere. As these light particles scatter, blue wavelengths scatter the most. This is because they are some of the shortest and fastest waves in the visible light spectrum. Due to this increased scattering, we commonly see our sky as blue!
The process of light scattering to produce color in our atmosphere was discovered by Lord John Rayleigh, and is now known as Rayleigh scattering! Light scattering occurs in many different places. For instance, the blue color seen in the ocean arises from a similar process.
Light as a Travelling Particle
It is important to know that light acts as a particle when it is traveling through the atmosphere. Light particles take the form of waves that can have different speeds and lengths. Each specific wavelength produces a distinct color of visible light. Another important piece of information is that our atmosphere is composed of small molecules of gas. These gas particles can have varying compositions, and they play an important role in the travel of light.
With that said, these waves tend to travel in a straight path, unless they encounter some form of an obstacle. In the case of our atmosphere, the obstacle is air particles that act to scatter the light in all directions.
Blue light, which has one of the shortest wavelengths and fastest speeds gets scattered the most when the sun is high in the sky, which is why we typically see the sky as blue.
Is the Sky Always Blue?
As you have probably seen, the sky isn’t always blue when you look at it. Depending on your location, the time of day, the atmospheric composition, the sky can be a range of colors. It can range from deep reds to soft grays and whites.
Changes in the color of the sky typically occur when the sun has moved its relative location within our skies. Sunsets and sunrises are the best times to see the sky have new and amazing colors, but why is this?
When the sun is closer to the horizon (such as during sunrise and sunset), the light it produces has to travel through more molecules in the atmosphere than when it is high up in the sky.
Due to the increased path of travel, blue light is scattered so much that it actually interferes with itself, making the blue appearance disappear. Likewise, other colors of visible light that have shorter wavelengths get scattered enough to be seen, which is why we may see our sky as a red, pink, or stunning white color during these events!
