The physics of sunsets
Article by- Ethan Seigel /Source: Science blogs Before one can understand the mystery of sunsets, one must first understand the basic principles regarding wavelengths of light. The wavelengths that our eyes can see vary from 400nm to 700nm. Red has the greatest and violet the smallest, and of course all the others rest in-between. Scattering occurs when light rays are obstructed by particles. A particular type of scattering occurs called Rayleigh scattering when the particle is smaller than the wave's wave length. Rayleigh scattering takes a huge role in the making of sunsets. The earth's atmosphere is made up of an abundance of oxygen and nitrogen which are smaller than the wavelength of light. Shorter wavelengths are scattered much more efficiently than larger wave lengths. Therefore blue light gets scattered away and all the other colours and eventually leaving only or mainly red light. The bright red sun that we see is really just reflecting white light but as each colour gets scattered the only colour to reach our eyes is red. This does not happen in daylight because when the sun is directly above you it does not have to penetrate that much of the atmospheric layer. The angle at which we view the sun is what causes the sky to light up in such beautiful colours. This is why as the sun sets it becomes redder and redder because the light is penetrating a thicker and thicker atmosphere. The thicker the atmosphere the deeper red because the likelihood of the other colours not shattering is less likely. Of course, more than just red make it through the atmospheric layer, however red is the most likely to. The same effect occurs with the moon as well.