The sky appears blue during the day because of the way that sunlight interacts with the Earth's atmosphere. Sunlight is made up of a spectrum of colors, including red, orange, yellow, green, blue, and violet. When sunlight reaches the Earth's atmosphere, it is scattered by the gases and particles in the air.
The blue light in sunlight is scattered more easily than the other colors because it travels as shorter, smaller waves. This means that when sunlight hits the Earth's atmosphere, the blue light is scattered in all directions, filling the sky with a blue glow.
At sunset and sunrise, the blue light is scattered less because the sunlight has to travel through more of the Earth's atmosphere to reach our eyes. This causes the sky to appear red, orange, and yellow during these times.
Overall, the blue color of the sky is caused by the scattering of sunlight by the Earth's atmosphere. This effect is known as Rayleigh scattering, and it is the same reason why the sky appears blue during the day, regardless of the location on Earth.
What is Rayleigh scattering?
Rayleigh scattering is the scattering of light by particles that are much smaller than the wavelength of the light. This scattering is named after the British scientist Lord Rayleigh, who first studied and explained the phenomenon in the 19th century.
When light travels through a medium such as air, water, or glass, it can be scattered by the particles in that medium. This scattering causes the light to change direction and spread out in different directions. In general, the shorter the wavelength of the light, the more easily it is scattered.
Blue light has a shorter wavelength than red light, so it is scattered more easily by the particles in the Earth's atmosphere. This is why the sky appears blue during the day. At sunrise and sunset, the blue light is scattered less because the sunlight has to travel through more of the Earth's atmosphere to reach our eyes. This allows the longer-wavelength colors such as red and orange to dominate the sky.
Overall, Rayleigh scattering is an important phenomenon that affects the way light travels through different media, including the Earth's atmosphere. It is responsible for the blue color of the sky during the day, as well as many other optical effects.