Have you ever starred at a beautiful sunset, a crystal blue sky or perfectly white clouds and wondered why they are the color that they are? If you’re like me, then the answer to that question is ….YES! In order to understand the beautiful colors that our world provides us, it is important to understand our atmosphere and how light works within it. Light is energy and travels at a rate of nearly 186,000 miles per second, and like water, exhibits the same characteristics of a wave, which has a wavelength and frequency (how many waves per second). As an example, imagine a long rope tied to the side of the wall and someone on the other end of the rope shaking it up and down. Each up and down shake of the rope is a cycle (i.e. frequency) and the distance between the ripples, created by the shaking of the rope, is the wavelength. When the rope moves more rapidly, the frequency will naturally increase and the wavelength will shorten. In the earth’s atmosphere, there are two principal gases, Nitrogen(78%), Oxygen(21%) and many other elements, which make up the balance. These gases react with the incoming light from the sun and since light is compromised of all the colors in the spectrum (i.e. Red, Orange, Yellow, Green, Blue, Indigo and Violet), certain color wavelengths interact differently as they enter our world. Blue light has the shortest wavelength in the spectrum, interacts best with oxygen atoms and gets scattered quite effectively, making it seem like the sky is blue.
As light travels, it moves in a straight line until something disturbs it, such as dust particles, water droplets, etc. Depending upon the light wavelength and the objects it hits (i.e. dust), will determine how much of a particular color is absorbed, reflected and scattered throughout the atmosphere. The higher frequencies (blues) are absorbed more often than the lower frequencies (reds) and since our eyes are more sensitive to the color blue than violet, the sky appears blue to us. In much the same way as to why the sky is blue, clouds appear white because their water droplets or ice crystals are large enough to scatter the light of the spectrum colors, which combine to produce white light. If a cloud appears dark, it is because either the one cloud is in another clouds shadow, or as clouds build vertically and get thicker, less light can pass through the cloud, giving it a darker appearance. This is also the reason why the bottom of clouds sometimes appear darker than the top. The darkness of a cloud also depends on the background sky. A cloud will look darker when a bright sky surrounds it and lighter when it is in front of a darker sky. So it is not always the case that a dark cloud will spell trouble for those trying to plan an outdoor activity. Lastly, why are sunrises and sunsets red? Simply put, as the sun lowers or rises in the horizon, its light must pass a greater distance before it reaches our eyes. That extra distance makes it harder for the blue light to be seen, but easier for the longer wavelength red color to pass, unhindered through the atmosphere. In other words, we see the sun’s disk as red because the atmosphere has blocked out its blue light. We do not see the entire sky red; however, because with a longer wavelength there is no scattering of red light as it reaches us in a direct line.
In the grand scheme of things, it is very easy to take for granted a blue sky, that perfect sunset or even that towering thunderstorm cloud, because in today’s society, one has barely enough time to breathe. So the next time your day is so hectic that you can’t stand it, take a deep breath, and step outside to enjoy what Mother Nature has blessed us with on a day in day out basis.