User:Sink Cat/SKYSOMETIMESBLUE

Verifiability is an important and core policy of Wikipedia. Article content should be backed up by reliable sources wherever needed to show that the presentation of material on Wikipedia is consistent with the views that are presented in scholarly discourse or the world at large. Such sources help to improve the encyclopedia.

The common trope "You don't need to cite that the sky is blue" attempts to convey that citing "obvious facts" is unnecessary and disruptive. This statement undermines the subjectivity and human-centricity present in language. How sure can we really be that the sky is blue?

Before we can break down the phrase "the sky is blue" into its parts and dissect them individually, we must understand what gives the sky its colouration.

What causes the sky to be a certain colour?

When photons from the sun enter the earth's atmosphere, they collide with air molecules. These collisions cause light to scatter in complex processes known as Rayleigh scattering and diffuse sky radiation. Because blue light has more energy (and therefore a shorter wavelength), it is scattered more than other colours.

Breaking down the phrase

Stating that the sky is blue is incorrect under many conditions. Therefore, the statement that the sky is blue is not an obvious one. Below are some examples in which the sky is not in fact blue.

Altitude

When we talk about the colouration of the sky, we assume that we're referring to the sky from sea level. This assumption ignores the altitude from which the observer is viewing the sky. At higher altitudes, there are fewer air molecules for the light to collide with. This causes less light to be scattered, and for the sky to become darker and more black. Stating that the sky is blue is incorrect if observed from high altitudes.

Ignorance of non-visible light

Because the sky scatters light with more energy than light with less energy, violet and ultraviolet light is scattered much more in comparison to blue light. The reason that we do not see the sky as violet is because the human eye is less adept to seeing violet light than it is blue light. Similarly, the reason that we do not see the sky as ultraviolet is because the human eye cannot see the ultraviolet light to begin with. These two facts reveal that the sky is in fact not blue, but violet and ultraviolet.

English

The English language defines the colours green, blue, indigo, cyan, and violet. However, not all languages create these distinctions. Many languages do not distinguish between green and blue, such as the Lakota language of North America. As such stating that the sky is blue is an inherently Anglo-centric statement, as to others, they may not distinguish between blue and green. This means that the sky is not blue to them.

Anthropocentrism

While the human eye can see blue light, some other animals may be unable to see blue light. To these animals, the sky would not be blue, as they would not be able to see the blue light being scattered. Conversely, many animals can see ultraviolet light. To them, they would see ultraviolet light being scattered instead of blue. As such, stating that the sky is blue is an anthropocentric statement.