Though a vibrant blue sky can usually be seen on a clear sunny day, does this mean that blue is the sky's true color? Moreover, is blue the only color of the sky?
According to Space, the matter is quite intricate and complicated. It actually involves molecules, atoms, light, some parts of the atmosphere, and even big lasers.
ALSO READ : Why is the Sky Blue, But Space is Black?
Are Sunny and Clear Skies Really Blue?
When a blue sky fills a sunny day, do people see blue oxygen or blue nitrogen? Actually, it is none of these. Rather, the visible blue light is actually sunlight that is scattered.
Space notes how the sun comes up with a vast spectrum of light that can be seen. This is something seen by humans as white. However, it actually covers all rainbow colors.
When sunlight seeps through, atmospheric molecules and atoms scatter the blue light in various directions that go further than red light. According to HyperPhysics, this is referred to as Rayleigh scattering, and it leads to blue skies and a white sun on days that are clear.
During sunset, such effects are dialed up. This is because sunlight must seep through more air in order to reach the surface. When this hypergiant gets more proximate to the horizon, the blue light almost entirely gets scattered or sucked in by dust. This leads to a red sun that has blue hues that surround it.
As for the true color of the sky, answers can probably be taken when studying its condition in the night.
The Night Sky and Airglow
Though the night sky is clearly dark, it isn't totally black. Though stars are present on it, the sky itself actually glows due to its atmosphere being able to naturally glow.
When seen from the countryside and far from the lights, the sky will actually reflect the silhouette of hills and trees.
According to Space, such a glow is referred to as airglow. When the light is visible, oxygen builds red and green light. The OH (hydroxyl) molecules come up with red light while sodium comes up with a sickly yellow color. Nitrogen, an element that the air is more rich in compared to sodium, does not affect airglow as much.
The specific airglow colors result from molecules and atoms that expel specific energy amounts in light form. For instance, in conditions of high altitude, UV light can split molecules of oxygen into atomic pairs. When such atoms recombine later on, they end up with a unique green light.
Sodium
While the atmosphere is not rich in sodium atoms, such atoms play a huge part when it comes to airglow. Phys also reports how they have a unique origin: shooting stars.
As these stars rocket through the sky, they leave atomic and molecular remnants. At times, these shooting stars have unique colors because of the molecules and atoms that they are filled with. Shooting stars that are extremely bright may even leave smoke trails that are visible to the eyes. Among such remnants are sodium elements.
To make up for the turbulence, specialists make use of a method known as adaptive optics to gauge the distortion of the images. The problem with such an approach, however, is that naturally bright stars are insufficient for the method to work in the entire sky. Hence, astronomers come up with artificial stars called laser guide stars.
Such atoms are situated vastly above the turbulent atmosphere. Hence, they can be enabled to glow by being fired with a power laser that is tuned to sodium's unique yellow hue.
The Sky Isn't Always Blue
This goes to show that the sky isn't always blue. It is also a sky that glows in the dark, with a mix of yellow, red, and green. Such colors are results from sunlight that is scattered, as well as from sodium and oxygen of shooting stars. On top of that, with the help of physics and lasers, artificial yellow stars can also help gain sharp cosmis images.
Check out more news and information on Environment and Climate in Science Times.
