As sunlight passes through the atmosphere, particles of oxygen and nitrogen scatter it, with shorter wavelengths such as blue being scattered more than longer ones such as red.
Tyndall and Rayleigh initially believed that the sky was blue because it contained dust particles and droplets of water vapour; later scientists came to realise this explanation would cause more variation with humidity or haze conditions than actually observed; as an alternative theory they postulated that its hue may have been caused by molecules of oxygen and nitrogen scattered by electromagnetic fields in the atmosphere.
Rayleigh Scattering
Light travels through our atmosphere and interacts with its molecules, giving the sky its color. When sunlight strikes an atmospheric particle such as an oxygen or nitrogen molecule, its wavelength is scattered to different degrees; shorter wavelengths of blue light tend to scatter more readily than longer wavelengths of red light – hence why our skies appear blue!
Scientists such as Tyndall and Rayleigh theorized that light scattering was caused by molecules of nitrogen and oxygen found in the atmosphere, with blue light being more easily scattered by such molecules than other colors. Einstein later provided proof of their theories by formulating an extensive mathematical formula for such scattering processes.
As the Sun continues its descent toward Earth’s atmosphere, its light must pass through more layers and be scattered by air particles, making the sky seem less blue as its position nears horizon.
Some might say the sky is blue because it contains gas molecules such as oxygen. While that is partially true, most often why our skies appear so vibrant is Rayleigh Scattering; when sunlight hits Earth’s atmosphere and hits its various gas molecules it gets scattered in various directions by each one’s size and shape, and that scattering gives our skies its distinctive hue.
Rayleigh Scattering can be easily observed when shining a flashlight through milk. Light is scattered in all directions, yet blue waves bounce around more strongly and end up hitting your eyes, while white light (still passing through) just goes through. You can conduct this experiment yourself using some food-grade dye in water.
Shorter Wavelengths
The sky is blue due to Rayleigh Scattering; when sunlight enters our atmosphere from the sun and travels through its atmosphere, its white light scatters through many channels until reaching our eyes as colored light. Most commonly, we perceive blue, but sometimes green or red tones can also appear; longer wavelengths such as red and violet tend to remain more tightly bound to atmosphere particles so they are less likely to scatter easily.
At noon, however, the sky appears more vibrant due to light traveling through a more direct path in order to reach our eyes and less scattered colors such as blue are scattered further across the sky than on the horizon. By contrast, light from the sun rays being more directly above you at noon means they tend to dominate more directly, making their presence apparent across the entire sky.
One reason the sky is blue relates to the frequency of light waves. Different wavelengths of visible light produce different frequencies that influence their brightness and bend-refract capabilities – the higher its frequency is, the brighter and more it bends or refracts; similarly, color of visible light also depends on wavelength; various wavelengths create distinct hues of visible light.
Sky color can also be affected by other atmospheric particles, like smoke or dust particles in the atmosphere, creating a haze which makes the sky appear gray or yellow – this may have been caused by forest fires, volcanoes, pollution or just urban life in general.
Other particles can alter the color of the sky by altering its refraction. Clouds made up of water droplets can appear blue; however, clouds composed of particulates larger than wavelengths of light may produce whiter results and create bluer or even redder tones depending on their composition and conditions at that moment. Mountainous regions often experience these conditions creating a blue haze which could also appear white, red or gray depending on composition and conditions at that moment in time.
Light Reflection
The sky is blue because light hits different particles in the atmosphere and is scattered into all directions, its wavelengths differing for each color of light (red, yellow, green and blue). Blue light has shorter wavelengths than red so is more likely to be scattered by air molecules in our atmosphere and thus create the color we see; red wavelengths are less likely to scatter and therefore more likely reach your eyes directly.
The colors of the sky can also alter throughout the day, due to sunlight passing through more of Earth’s atmosphere at sunset and sunrise than during daytime. As sunlight travels deeper into this layer, its molecules scatter longer wavelengths (orange and red light) more readily than blue wavelengths – this causes sunset skies to appear redder than during daytime hours.
Scientists such as John Tyndall and Sir James Rayleigh once thought that the color of the sky came from microscopic dust particles and droplets of water in the atmosphere acting like small mirrors to reflect blue light while absorbing the remainder. But these theories were proven wrong over time as scientists discovered light is scattered by molecules (primarily nitrogen and oxygen) instead.
As light travels through the atmosphere, its wavelengths change significantly due to interaction with gases and molecules acting like prisms. Short wavelengths such as blue and violet tend to be scattered by these molecules because their frequencies match up more with those found naturally resonating between nitrogen and oxygen molecules; longer wavelengths such as red and orange tend not to be scattered as readily; this explains why sky appears blue during daytime hours while becoming pink, red, or yellow at sunset and sunrise.
Atmosphere
The atmosphere is a layer of gases encompassing Earth. These gases move and collide constantly, creating an unstable environment and driving weather patterns. Air molecules in this layer scatter shorter wavelengths of light more readily than longer ones; giving sky its blue color. As the Sun moves lower in the sky, more blue light gets scattered away and red and yellow hues make their way directly through into your eyes without competing against blue hues – hence sunsets often appear orange or red in hue.
Tyndall and Rayleigh believed that the sky’s blue color was caused by small particles of dust or droplets of water in the atmosphere, however this theory has since been disproved as scientists now understand it’s the molecules in air itself which account for its hue.
A blue sky occurs because air molecules scatter sunlight in all directions, with short wavelengths of blue light being dispersed more strongly than their long counterparts – due to tiny airborne particles being densely packed together and closer together than long wavelengths – this phenomenon is known as Rayleigh scattering; its dependence on wavelength is given as 1/l41/l4 where l is the wavelength and l1 represents distance from scattering particles.
At sunrise or sunset, when the Sun is low in the sky, its rays have to travel farther through the atmosphere before reaching your eyes – this means more blue-violet light is scattered away than expected, leaving only reds and yellows for you to experience. As such, skies nearer the horizon often look paler and less vibrant than directly overhead.
The stratospheric ozone layer is another significant contributor to the sky’s blue hue, situated just above the troposphere and consisting of very few air molecules which scatter light. At higher elevations, its presence creates an inky blue or even bluish-violet hue for our skies to reflect off of.