You may have been exposed before to some misconceptions about why the sky is blue, such as that the sky reflects the ocean or that oxygen is a blue gas, or that sunlight has a blue color, while - in fact - the cause of the blue of the sky is due to 3 simple factors, when they meet Together they are inevitable.
The first is that sunlight is composed of different wavelengths, and the second is that the Earth's atmosphere consists of particles that scatter light of different wavelengths in different quantities, in addition to the sensitivity of our eyes.
What is sunlight made of?
The sun emits a wide spectrum of light, consisting of ultraviolet, visible and infrared rays.
Visible light makes up about 50% of the spectrum of sunlight, and as its name suggests, it is the only part of the light that can be seen with the naked eye, while ultraviolet and infrared rays are invisible.
The visible sunlight consists of red, orange, yellow, green, blue, and violet colors.
Violet light - and its blue side - has the shortest wavelength, which means that it has the highest frequency and energy, while red has the longest wavelength, shortest frequency and lowest energy.
Although many people think the ocean is blue because it reflects the sky, this is not true (Pixabay)
How does light propagate on Earth?
Sunlight reaches the Earth's atmosphere and is scattered in all directions by all the gases and particles in the air.
The tiny, invisible particles that make up our atmosphere - like particles of nitrogen, oxygen, water, carbon dioxide, as well as argon atoms - all scatter light of all wavelengths, but they scatter light of shorter wavelengths more efficiently.
What is "Raleigh Scattering" causing the sky to blue?
Sky blue is explained by a phenomenon called "raleigh scattering", which refers to the scattering of electromagnetic radiation, of which light is a form, by much smaller wavelength particles, which are atmospheric particles.
What reaches the Earth - as a result of the scattering of solar radiation - is called diffuse sky radiation, and although only about a third of the light is scattered, the smallest wavelengths of light are what are easily dispersed and scattered, and this corresponds to the blue color that has the second shortest wavelength after the violet color This is why when we look at the sky we see it blue.
The sun emits a wide spectrum of light, consisting of ultraviolet, visible and infrared rays (pixabay)
Why is the sky not violet?
If the violet color has the shortest wavelength and the most dispersed color, then it is natural for the sky to appear violet rather than blue, but why does this not happen?
The reason for this is due to the sensitivity of our eyes to light. Although violet is the dominant color in the atmosphere that surrounds us, the eye cells are not sensitive enough to this color as is the case with blue.
There is more violet light coming from the atmosphere than blue light, but our eyes respond more strongly to the wavelengths of blue, cyan and green light compared to violet, so even though there is a lot of violet light, it is not enough to overcome the strong blue signal it sends. Our brains.
If we can see the ultraviolet rays very efficiently, the sky is likely to appear more violet.
If the sky contained only violet, our eyes would see the sky purple with a reddish tinge, but when the purple and blue lights overlap, we see the sky in a pale blue color.
Likewise, if human eyes are similar to the structure of dogs' eyes, they will be able to see the blue sky during the day, but they will not be able to see red, orange and yellow at sunset.
What is the secret of the orange twilight?
At sunset and sunrise, the angle from which sunlight enters the atmosphere changes dramatically, and most of the wavelengths of blue and green light are scattered even before reaching the lower atmosphere, so we see more orange and red colors in the sky.
When we look at the Earth from space, we find that it is clearly predominantly blue, due to the predominance of water bodies with a blue color (Pixabay)
Does the ocean reflect the color of the sky?
Although many people think that the ocean is blue because it reflects the sky, this is not true, as the water actually appears blue because it absorbs red light.
In deep water, not all wavelengths of light can fully penetrate the liquid, as there are many water molecules in the path of the photons, and water molecules absorb all the red wavelengths of light, making them reflect blue.
It is also for this reason that shallow water appears less blue than deep water, and less absorption means less reflection.
In shallow bodies of water - the cup of water you drink, for example - there is not enough water to absorb enough photons, so the light penetrates the cup's water completely, so we see the water is colorless.
Why does planet Earth appear blue from space?
When we look at the Earth from space, we find that it is clearly predominantly blue, but the atmosphere has nothing to do with this time, as this is due to the predominance of blue water bodies (70.8%) over the land area (29.2%).
This is also the reason why our planet is the brightest planet. The huge water bodies on its surface reflect sunlight, making the planet appear like a bright blue pearl.
Is the sun yellow or orange?
Young children usually color the sun yellow, orange, or even red, and the cultural factor may have a hand in that, and while children in the United States usually paint the image of the sun in yellow, children in Japan color it red, but this is not all The real sun, the sun is white.
The sun basically represents all the colors mixed together, which appears to our eyes white, and it is easy to confirm this through the images taken of the sun from space.
Planetary atmospheres contain a varied mixture of gases, which gives each planet its own color (pixabay)
Does the sky appear blue on other planets?
It all depends on what is present in the atmosphere, and the atmosphere in rocky planets such as Earth, is usually the lighter and thinner outer layer, which contains a variety of gases, and this combination is what gives the atmosphere of the planet its color.
For example, Mars has a very thin atmosphere, consisting mostly of carbon dioxide in addition to fine dust particles, and these particles scatter light differently from the gases and particles in the Earth's atmosphere.
The images captured from NASA vehicles have shown that what is happening on Mars is the opposite of what is happening on Earth.
Where the Martian sky takes an orange or reddish hue during the day, and the sky around the sun begins to take on a blue-gray tinge at sunset.
As for the atmosphere of the two ice giants "Neptune" and "Uranus", both of them appear blue, but that is caused by the enormous quantities of methane gas there.
Uranus' atmosphere also contains some "ammonia", which makes the planet slightly greener than the dark blue color we see on Neptune.
As for the planet "Saturn", the ice crystals made of "ammonia" in the upper atmosphere make it pale yellow.
As for "Jupiter", it contains distinct brown and orange stripes, thanks to gases that may contain "phosphorous" and "sulfur", and perhaps even more complex chemicals called "hydrocarbons".
As for the planet "Mercury", it has no atmosphere at all.