Why Is the Sky Blue??

The sky appears blue due to a phenomenon known as Rayleigh scattering. When sunlight enters Earth’s atmosphere, it is made up of different colors, each with varying wavelengths. Blue light has a shorter wavelength and is scattered more easily by molecules in the air than other colors like red or yellow, which have longer wavelengths. As a result, when we look up, we see a predominantly blue sky. However, during sunrise and sunset, the sky changes to shades of orange and red because the sun’s light has to pass through a thicker layer of the atmosphere, scattering the shorter blue wavelengths out of our line of sight and allowing the longer red wavelengths to dominate. This same scattering effect is also responsible for the color of the ocean, as water molecules absorb longer wavelengths and reflect the blue ones. The simple science behind the sky’s color is a perfect example of how physics shapes our daily perception of the world.