How to explain to a child why the sky is blue

Tell us about the spectrum

Sunlight is white, meaning it includes all the colors in the spectrum. It would seem that the sky should also be white, but it is blue.

Surely your child knows the phrase "Every Hunter Wants to Know Where the Pheasant Sits", which helps to remember the colors of the rainbow. And the rainbow is the best way to understand how light breaks down into waves of different frequencies. The longest wavelength is for red, the shortest is for violet and blue.

The air, which contains gas molecules, micro-crystals of ice and water droplets, scatters light with a short wavelength more strongly, so there are eight times more blue and purple in the sky than red. This effect is called Rayleigh scattering.

Draw an analogy with balls rolling down a corrugated board. The larger the ball, the less likely it is to stray off course or get stuck.

Explain why the sky cannot be other colors

Why isn't the sky purple?

It is logical to assume that the sky should be purple, because this color has the shortest wavelength. But here the features of sunlight and the structure of the human eye come into play. The spectrum of sunlight is uneven, with fewer shades of violet than other colors. And the human eye does not see part of the spectrum, which further reduces the percentage of shades of violet in the sky.

Why isn't the sky green?

A child may have a question: "Since the scattering increases with decreasing wavelength, why is the sky not green?" Not only blue rays are scattered in the atmosphere. Their wave is the shortest, so they are the most visible and brightest. But if the human eye was arranged differently, the sky would seem green to us. After all, the wavelength of this color is slightly longer than that of blue.

Light is not like paint. If you mix green, blue and purple colors, you get a dark color. With light, the opposite is true: the more colors are mixed, the lighter the result is.

Tell us about the sunset

We see blue skies when the Sun shines from above. When it approaches the horizon, and the angle of incidence of the sun's rays decreases, the rays go tangentially, passing a much larger path. Because of this, waves of the blue-blue spectrum are absorbed in the atmosphere and do not reach the Earth. In the atmosphere, red and yellow colors are scattered. Therefore, at sunset, the sky turns red.