In my opinion, there are not a lot more things in nature that are more beautiful than sunsets and sunrises. A perfect vacation always starts with a sunrise over the ocean horizon. And if you love sunsets as much as I do, you probably can’t count the sunset photos on your phone. But have you ever asked yourself where the pretty colors in the sky come from?
When the sun rises or sets, it is mostly orange, red, pink, or yellow, even though the sky normally appears blue. This is closely connected to the wavelengths of light.
But let’s start at the beginning. You can imagine sunlight as waves of energy that travel through the atmosphere. These waves can be longer or shorter, while their length dictates the color of the light that we see.
The color of the sky results from sunlight waves that are scattered by molecules in the atmosphere. The scattering of light causes the light to break up into different wavelengths and depending on what wavelength light has, it appears as a different color. Blue light has short wavelengths, while red light has long wavelengths.
During the day, the sky looks blue because the sunlight gets split up and jumps back and forth between the air molecules, scattering in all directions. The repeated shattering of the light leads to short wavelengths, which appear blue. The result is our beautiful blue sky.
The even more beautiful colored sky of sunsets and sunrises, however, is due to the light traveling differently. As the sunlight enters the atmosphere, it is at a different angle than normally. When the sun is close to the horizon, the light has to travel through more of the atmosphere than it does when it is overhead. The science is the same as for the blue sky, just that longer wavelengths of red, orange, and pink light are passing through. Clouds play a big role in this too, because the red, orange, and pink light are only visible when hitting the clouds. Otherwise, there wouldn’t be anything for the colored light to reflect off of.
This is also how sunsets can be an indication of air pollution. The more intense the color, the more aerosols are in the atmosphere. This is due to the fact that there are more molecules in the air that scatter the light. Intensely red and orange sunsets might be spectacular to look at, but they are mostly a sign of increased air pollution.
Having this whole concept in mind, it is also easy to understand how a rainbow forms. It is common knowledge that you have to look for a rainbow when the sun is shining shortly after it has rained. The light gets scattered in all the wavelengths, long and short, because of the water droplets that refract the light as it travels through them. We can see the full spectrum of visible light, resulting in a rainbow with red (longest wavelength) on top and violet (shortest wavelength) at the bottom.
I hope you understand the basic science behind the colors of the sky and that you now know a little bit more about the magical beauty of our sky. The next time you see a sunset, you can even explain where the color comes from!
Sources:
https://scied.ucar.edu/learning-zone/atmosphere/appearance-sky (29.03.2023)
https://www.travelandleisure.com/trip-ideas/nature-travel/why-sky-changes-color-sunset (Jamie Carter 29.03.2023)