Who hasn't asked themselves this question at some point? And perhaps they've told us something like... "It's a reflection of the oceans!" It's funny, if we ask the question the other way around, the popular answer to why the oceans are blue is usually because the sky is blue. Something doesn't quite fit, right? Of course, we shouldn't look for who's "painting" what, but rather where that color comes from. The white rays of sunlight coming from the Sun interacting with the atmosphere are the main culprits.
When light rays pass through transparent or translucent bodies, each of the colors that make up white light separate and drift at a certain angle. Always depending on the medium they pass through, the direction and shape will change. The white light emitted by the Sun corresponds to a fraction of all the waves that make up the electromagnetic spectrum. The color range is the same as the rainbow. In order to see this decomposition of colors, it is enough to make a ray of light pass through a prism.
Decomposing the colors of light
Electromagnetic spectrum
As the colors decompose, violet and blue wavelengths are shorter than the yellow ones (more intermediate) or its extreme, the red, with longer lengths. That is what causes this kind of fan of colors. When the sun's rays pass through the atmosphere, they do so through water vapor, dust, ash, etc. In this point, violet and blue light rays are deflected to a greater extent than yellows and reds.
These rays, constantly colliding with air particles loaded with humidity, dust and ash, cause a constant change in the trajectory. This process is known as "spreading." This is what causes that bluish color. By spreading four times faster than red colors due to the shorter wavelength, it is what causes us to have that general blue feeling and that it is not focused to a single point.
Yes, the sky looks blue during the day. But not always! Cast?
Graphic interpretation of the different shades | Gamavision
The opposite happens to rays belonging to the yellow and red spectra.Their longer wavelength causes them to disperse less. Because they travel more in a straight line, they cause these colors to mix, giving an orange hue. Depending on the time of day, the color of the sky can certainly vary. This is something we can see at dawn or dusk, and we see the Sun near sea level or the horizon. For more information on the subject, you can consult an article that delves into why does the sky turn orange.
Light rays here have to pass through a greater amount of atmospheric thickness. The forced interaction of a much larger number of water vapor particles, droplets, dust, etc., eventually forces the following. Light rays that tend toward blue and violet are continually scattered to the sides. Rays closer to the red spectrum, with straighter trajectories, continue, giving us that more orange and reddish color. You can also learn more about the composition of the atmosphere which influences this phenomenon.
It always depends on the amount of ash and dust suspended in the air
The intensity of red color that is perceived in the sky at sunrise or sunset always depends on the amount of ash and dust suspended in the air, apart from the water vapor. This is also the main reason why, when there are eruptions or fires, for example, the amount of dust and ash increases, making these colors even more vivid. If you want to learn more about how clouds form, check out this article on how orographic clouds form.
A good model of this phenomenon is found on Mars. In addition, now that he is going to conquer it, it takes something more relevant to explain why the planet always looks reddish. It is precisely because of the "amount of atmosphere" it has, that it is very fine. In addition, unlike on Earth, which is mainly oxygen, there it is made up mostly of carbon dioxide. Together with the large amount of iron oxide, and the gusts of wind that raise dust, they make Mars the red planet, unlike Earth, our blue planet.
