Chippewa Valley Times

An article originally published by The Conversation explores the scientific explanation behind why the sky appears blue. This inquiry, posed by Mariana A-E., an 11-year-old from Tucson, Arizona, delves into the complex science involving both physics and chemistry.

The primary components of Earth's atmosphere, nitrogen and oxygen molecules, play a crucial role in this phenomenon. These molecules are minuscule, measuring approximately 0.4 nanometers or 16 billionths of an inch. As sunlight traverses the atmosphere, it interacts with these tiny particles.

The explanation lies in a process known as scattering. "When one of those light marbles hits a nitrogen or oxygen tennis ball," describes the article using an analogy of tennis balls and marbles to represent molecules and light respectively, "the tennis ball 'eats' the marble and then very quickly spits it back out again." This scattering effect was first explained by British physicist John William Strutt, also known as Lord Rayleigh, around 1870. He discovered that blue light from the Sun is scattered more than other colors when passing through Earth's atmosphere—a phenomenon now termed Rayleigh scattering.

The presence of other atmospheric gases like carbon dioxide or methane has minimal impact on sky color but significant effects on global climate.

Without atmospheric scattering, our sky would resemble the dark skies seen from the Moon. However, thanks to this effect, we see a blue sky during sunny days because blue light is scattered more efficiently across the sky compared to other colors.

The article further explains how this same principle accounts for red and orange hues at sunrise and sunset: "When the Sun is near the horizon...the blue and green light is scattered so well that you can hardly see it."

Understanding these scientific principles helps us appreciate how colors influence human expression throughout history—something to ponder when choosing what color shirt to wear each day.